WorldWideScience

Sample records for atmospheric general circulation

  1. Idealized Tropical Cyclones in Atmospheric General Circulation Models

    Science.gov (United States)

    Reed, K. A.; Jablonowski, C.

    2008-12-01

    The paper discusses the design of idealized tropical cyclone experiments in Atmospheric General Circulation Models (GCMs). Our first goal is to suggest the evolution of an idealized tropical cyclone as a standard test case for atmospheric model developments that adds complexity to a dynamical-core and GCM test suite. In addition, we plan on using idealized cyclones as a test bed for hurricane-dust interactions in the Atlantic Ocean Basin and climate-hurricane sensitivity studies. A group of sensitivity tests will be presented using the National Center for Atmospheric Research's (NCAR) Community Atmosphere Model (CAM) 3.1. The tests are run in a so-called aqua-planet configuration that consists of an ocean-covered Earth with prescribed sea surface temperatures and radiative forcing. We utilize the CAM 3.1 Finite Volume dynamical core on a latitude-longitude grid at a half-degree horizontal resolution. The development of an idealized, initially weak warm-core vortex is investigated with varying initial parameters including vorticity, radius of maximum wind, latitude, and sea surface temperature. The evolution of the initial vortex is especially sensitive to the initial vorticity, and therefore the initial wind speed, and radius of maximum wind. This sensitivity is also related to the model resolution. Although model resolution has improved greatly over the last decade, improved resolution will still be needed to model tropical cyclones in global climate models. These sensitivity tests provide us with suitable initial parameter configurations to model tropical cyclogenesis in CAM 3.1 and other GCMs.

  2. Comparing the Degree of Land-Atmosphere Interaction in Four Atmospheric General Circulation Models

    Science.gov (United States)

    Koster, Randal D.; Dirmeyer, Paul A.; Hahmann, Andrea N.; Ijpelaar, Ruben; Tyahla, Lori; Cox, Peter; Suarez, Max J.; Houser, Paul R. (Technical Monitor)

    2001-01-01

    Land-atmosphere feedback, by which (for example) precipitation-induced moisture anomalies at the land surface affect the overlying atmosphere and thereby the subsequent generation of precipitation, has been examined and quantified with many atmospheric general circulation models (AGCMs). Generally missing from such studies, however, is an indication of the extent to which the simulated feedback strength is model dependent. Four modeling groups have recently performed a highly controlled numerical experiment that allows an objective inter-model comparison of land-atmosphere feedback strength. The experiment essentially consists of an ensemble of simulations in which each member simulation artificially maintains the same time series of surface prognostic variables. Differences in atmospheric behavior between the ensemble members then indicates the degree to which the state of the land surface controls atmospheric processes in that model. A comparison of the four sets of experimental results shows that feedback strength does indeed vary significantly between the AGCMs.

  3. The stability of the thermohaline circulation in a coupled ocean-atmosphere general circulation model

    Energy Technology Data Exchange (ETDEWEB)

    Schiller, A. [Max-Planck-Institut fuer Meteorologie, Hamburg (Germany); Mikolajewicz, U. [Max-Planck-Institut fuer Meteorologie, Hamburg (Germany); Voss, R. [Deutsches Klimarechenzentrum (DKRZ), Hamburg (Germany)

    1996-02-01

    The stability of the Atlantic thermohaline circulation against meltwater input is investigated in a coupled ocean-atmosphere general circulation model. The meltwater input to the Labrador Sea is increased linearly for 250 years to a maximum input of 0.625 Sv and then reduced again to 0 (both instantaneously and slowly decreasing over 250 years). The resulting freshening forces a shutdown of the formation of North Atlantic deepwater and a subsequent reversal of the thermohaline circulation of the Atlantic, filling the deep Atlantic with Antarctic bottom water. The change in the overturning pattern causes a drastic reduction of the Atlantic northward heat transport, resulting in a strong cooling with maximum amplitude over the northern North Atlantic and a southward shift of the sea-ice margin in the Atlantic. Due to the increased meridional temperature gradient, the Atlantic intertropical convergence zone is displaced southward and the westerlies in the northern hemisphere gain strength. We identify four main feedbacks affecting the stability of the thermohaline circulation: the change in the overturning circulation of the Atlantic leads to longer residence times of the surface waters in high northern latitudes, which allows them to accumulate more precipitation and runoff from the continents, which results in an increased stability in the North Atlantic.

  4. Venusian Polar Vortex reproduced in an Atmospheric General Circulation Model

    Science.gov (United States)

    Ando, Hiroki; Imamura, Takeshi; Takagi, Masahiro; Sugimoto, Norihiko; Kashimura, Hiroki

    The Venus atmosphere has a polar vortex rotating in the retrograde direction with a period of about three days. The vortex has a warm feature surrounded by a cold collar (e.g., Taylor et al. 1980; Piccioni et al. 2006). Although the Venusian polar vortex has been reported by many observations, its mechanism is still unknown. Elson (1982, 1989) examined the structure of the polar vortex by linear calculations. However, the background zonal wind assumed in the calculations was much stronger or weaker than those retrieved in the previous measurements (e.g., Peralta et al. 2008; Kouyama et al. 2012). Lee et al. (2010) and Yamamoto and Takahashi (2012) performed numerical simulations with general circulation models (GCMs) of the Venus atmosphere and obtained vertical structure in the polar region. However, the models included artificial forcing of Kelvin and/or Rossby waves. We have developed a new Venusian GCM by modifying the Atmospheric GCM For the Earth Simulator (Sugimoto et al. 2012; 2013). The basic equations of the GCM are primitive ones in the sigma coordinate on a sphere without topography. The model resolution is T42 (i.e., about 2.8 deg x 2.8 deg grids) and L60 (Deltaz is about 2 km). Rayleigh friction (sponge layer) in the upper layer (>80 km) is applied to prevent the reflection of waves, whose effect increases gradually with height. In the model, the atmosphere is dry and forced by the solar heating and Newtonian cooling. The vertical profile of the solar heating is based on Crisp (1986), and zonally averaged distribution is used. In addition diurnal component of the solar heating, which excites the diurnal and semi-diurnal tides, is also included. Newtonian cooling relaxes the temperature to the zonally uniform basic temperature which has a virtual static stability of Venus with almost neutral layers, and its coefficient is based on Crisp (1986). To prevent numerical instability, the biharmonic hyper-diffusion is included with 0.8 days of e-folding time

  5. Uncertainities in carbon dioxide radiative forcing in atmospheric general circulation models

    Energy Technology Data Exchange (ETDEWEB)

    Cess, R.D.; Zhang, M.H. (State Univ. of New York, Stony Brook, NY (United States)); Potter, G.L.; Gates, W.L.; Taylor, K.E. (Lawrence Livermore National Laboratory, CA (United States)); Colman, R.A.; Fraser, J.R.; McAvaney, B.J. (Bureau of Meterorology Research Centre, Victoria (Australia)); Dazlich, D.A.; Randall, D.A. (Colorado State Univ., Fort Collins, CO (United States)); Del Genio, A.D.; Lacis, A.A. (Goddard Institute for Space Studies, New York, NY (United States)); Esch, M.; Roeckner, E. (Max Planck Institute for Meteorology, Hamburg (Germany)); Galin, V. (Russian Academy of Sciences, Moscow (Russian Federation)); Hack, J.J.; Kiehl, J.T. (National Center for Atmospheric Research, Boulder, CO (United States)); Ingram, W.J. (Hadley Centre for Climate Prediction and Research, Berkshire (United Kingdom)); Le Treut, H.; Lli, Z.X. (Laboratoire de Meteorologie Dynamique, Paris (France)); Liang, X.Z.; Wang, W.C. (State Univ. of New York, Albany, NY (United States)); Mahfouf,

    1993-11-19

    Global warming, caused by an increase in the concentrations of greenhouse gases, is the direct result of greenhouse gas-induced radiative forcing. When a doubling of atmospheric carbon dioxide is considered, this forcing differed substantially among 15 atmospheric general circulation models. Although there are several potential causes, the largest contributor was the carbon dioxide radiation parameterizations of the models.

  6. Assessment of atmosphere-ocean general circulation model simulations of winter northern hemisphere atmospheric blocking

    Energy Technology Data Exchange (ETDEWEB)

    Vial, Jessica; Osborn, Tim J. [University of East Anglia, Climatic Research Unit, School of Environmental Sciences, Norwich (United Kingdom)

    2012-07-15

    An assessment of six coupled Atmosphere-Ocean General Circulation Models (AOGCMs) is undertaken in order to evaluate their ability in simulating winter atmospheric blocking highs in the northern hemisphere. The poor representation of atmospheric blocking in climate models is a long-standing problem (e.g. D'Andrea et al. in Clim Dyn 4:385-407, 1998), and despite considerable effort in model development, there is only a moderate improvement in blocking simulation. A modified version of the Tibaldi and Molteni (in Tellus A 42:343-365, 1990) blocking index is applied to daily averaged 500 hPa geopotential fields, from the ERA-40 reanalysis and as simulated by the climate models, during the winter periods from 1957 to 1999. The two preferred regions of blocking development, in the Euro-Atlantic and North Pacific, are relatively well captured by most of the models. However, the prominent error in blocking simulations consists of an underestimation of the total frequency of blocking episodes over both regions. A more detailed analysis revealed that this error was due to an insufficient number of medium spells and long-lasting episodes, and a shift in blocking lifetime distributions towards shorter blocks in the Euro-Atlantic sector. In the Pacific, results are more diverse; the models are equally likely to overestimate or underestimate the frequency at different spell lengths. Blocking spatial signatures are relatively well simulated in the Euro-Atlantic sector, while errors in the intensity and geographical location of the blocks emerge in the Pacific. The impact of models' systematic errors on blocking simulation has also been analysed. The time-mean atmospheric circulation biases affect the frequency of blocking episodes, and the maximum event duration in the Euro-Atlantic region, while they sometimes cause geographical mislocations in the Pacific sector. The analysis of the systematic error in time-variability has revealed a negative relationship between the

  7. Implementing Numerical Experiments Based on the Coupled Model of Atmospheric General Circulation and Thermohaline Ocean One

    Directory of Open Access Journals (Sweden)

    V. P. Parhomenko

    2015-01-01

    Full Text Available The paper presents a realized hydrodynamic three-dimensional global climatic model, which comprises the model blocks of atmospheric general circulation, thermohaline large-scale circulation of the ocean, and sea ice evolution. Before rather strongly aggregated heat-moisturebalance model of the atmosphere for temperature and humidity of a surface layer was used as a model of the atmosphere. The atmospheric general circulation model is significantly more complicated and allows us to describe processes in the atmosphere more adequately. Functioning of a coupled climatic model is considered in conditions of the seasonal cycle of solar radiation.The paper considers a procedure for coupled calculation of the ocean model and atmospheric general circulation model. Synchronization of a number of parameters in both models is necessary for their joint action. In this regard a procedure of two-dimensional interpolation of data defined on the grids of the ocean model and atmosphere model and back is developed. A feature of this task is discrepancy of grid nodes and continental configurations in models. Coupled model-based long-term calculations for more than 400 years have shown its stable work. Calculation results and comparison with observation data are under discussion.The paper shows distribution of mean global atmosphere temperature versus time in stable conditions to demonstrate that there is inter-annual variability of atmosphere temperature at the steady state of a climate system. It presents distribution of temperature difference of the ocean surface from the observations and from the model of the ocean thermohaline circulation for January. Noticeable deviations of temperature are observed near Antarctica. Apparently, it is because of inaccurate calculation of the sea ice distribution in model. The geographical distribution of the ocean surface temperature for January with coupled calculation shows, in general, a zonal uniform structure of isolines

  8. Results of an interactively coupled atmospheric chemistry – general circulation model: Comparison with observations

    Directory of Open Access Journals (Sweden)

    R. Hein

    Full Text Available The coupled climate-chemistry model ECHAM4.L39(DLR/CHEM is presented which enables a simultaneous treatment of meteorology and atmospheric chemistry and their feedbacks. This is the first model which interactively combines a general circulation model with a chemical model, employing most of the important reactions and species necessary to describe the stratospheric and upper tropospheric ozone chemistry, and which is computationally fast enough to allow long-term integrations with currently available computer resources. This is possible as the model time-step used for the chemistry can be chosen as large as the integration time-step for the dynamics. Vertically the atmosphere is discretized by 39 levels from the surface up to the top layer which is centred at 10 hPa, with a relatively high vertical resolution of approximately 700 m near the extra-tropical tropopause. We present the results of a control simulation representing recent conditions (1990 and compare it to available observations. The focus is on investigations of stratospheric dynamics and chemistry relevant to describe the stratospheric ozone layer. ECHAM4.L39(DLR/CHEM reproduces main features of stratospheric dynamics in the arctic vortex region, including stratospheric warming events. This constitutes a major improvement compared to earlier model versions. However, apparent shortcomings in Antarctic circulation and temperatures persist. The seasonal and interannual variability of the ozone layer is simulated in accordance with observations. Activation and deactivation of chlorine in the polar stratospheric vortices and their inter-hemispheric differences are reproduced. Considering methane oxidation as part of the dynamic-chemistry feedback results in an improved representation of the spatial distribution of stratospheric water vapour concentrations. The current model constitutes a powerful tool to investigate, for instance, the combined direct and indirect effects of anthropogenic

  9. 3D General Circulation Model of the Middle Atmosphere of Jupiter

    Science.gov (United States)

    Zube, Nicholas Gerard; Zhang, Xi; Li, Cheng; Le, Tianhao

    2017-10-01

    The characteristics of Jupiter’s large-scale stratospheric circulation remain largely unknown. Detailed distributions of temperature and photochemical species have been provided by recent observations [1], but have not yet been accurately reproduced by middle atmosphere general circulation models (GCM). Jupiter’s stratosphere and upper troposphere are influenced by radiative forcing from solar insolation and infrared cooling from hydrogen and hydrocarbons, as well as waves propagating from the underlying troposphere [2]. The relative significance of radiative and mechanical forcing on stratospheric circulation is still being debated [3]. Here we present a 3D GCM of Jupiter’s atmosphere with a correlated-k radiative transfer scheme. The simulation results are compared with observations. We analyze the impact of model parameters on the stratospheric temperature distribution and dynamical features. Finally, we discuss future tracer transport and gravity wave parameterization schemes that may be able to accurately simulate the middle atmosphere dynamics of Jupiter and other giant planets.[1] Kunde et al. 2004, Science 305, 1582.[2] Zhang et al. 2013a, EGU General Assembly, EGU2013-5797-2.[3] Conrath 1990, Icarus, 83, 255-281.

  10. How does the latitudinal dependency of the cloud structure change Venus' atmosphere's general circulation?

    Science.gov (United States)

    Garate-Lopez, I.; Lebonnois, S.

    2017-09-01

    Differently to the previous simulation of the LMD/IPSL Venus GCM, we now take into account the latitudinal variation of the clouds' structure and we analyze its impacts on the general circulation of Venus atmosphere. Both solar heating rates and the infrared net-exchange rate matrix used in the radiative transfer code have been modified in that sense. Additional tuning below the clouds has also been performed. The current results show a better agreement with observations in both mean zonal wind and average temperature fields. Moreover, taking into account the latitudinal variation of the clouds has brought along with it the formation of a well defined cold collar poleward of 60º at cloud level. Besides, we have reanalyzed the wave activity present in Venus atmosphere and found new baroclinic mid-latitude waves. However, we do not obtain the gravity waves present in the deep atmosphere in the previous model.

  11. Theoretical and experimental design studies for the Atmospheric General Circulation Experiment

    Science.gov (United States)

    Fowlis, W. W.; Hathaway, D. H.; Miller, T. L.; Roberts, G. O.; Kopecky, K. J.

    1985-01-01

    The major criterion for the Atmospheric General Circulation Experiment (AGCE) design is that it be possible to realize strong baroclinic instability in the spherical configuration chosen. A configuration was selected in which a hemispherical shell of fluid is subjected to latitudinal temperature gradients on its spherical boundaries and the latitudinal boundaries are insulators. Work in the laboratory with a cylindrical version of this configuration revealed more instabilities than baroclinic instability. Since researchers fully expect these additional instabilities to appear in the spherical configuration also, they decided to continue the laboratory cylindrical annulus studies. Four flow regimes were identified: an axisymmetric Hadley circulation, boundary layer convection, baroclinic waves and deep thermal convection. Regime diagrams were prepared.

  12. Venus atmosphere simulated by a high-resolution general circulation model

    Science.gov (United States)

    Sugimoto, Norihiko

    2016-07-01

    An atmospheric general circulation model (AGCM) for Venus on the basis of AFES (AGCM For the Earth Simulator) have been developed (e.g., Sugimoto et al., 2014a) and a very high-resolution simulation is performed. The highest resolution of the model is T319L120; 960 times 480 horizontal grids (grid intervals are about 40 km) with 120 vertical layers (layer intervals are about 1 km). In the model, the atmosphere is dry and forced by the solar heating with the diurnal and semi-diurnal components. The infrared radiative process is simplified by adopting Newtonian cooling approximation. The temperature is relaxed to a prescribed horizontally uniform temperature distribution, in which a layer with almost neutral static stability observed in the Venus atmosphere presents. A fast zonal wind in a solid-body rotation is given as the initial state. Starting from this idealized superrotation, the model atmosphere reaches a quasi-equilibrium state within 1 Earth year and this state is stably maintained for more than 10 Earth years. The zonal-mean zonal flow with weak midlatitude jets has almost constant velocity of 120 m/s in latitudes between 45°S and 45°N at the cloud top levels, which agrees very well with observations. In the cloud layer, baroclinic waves develop continuously at midlatitudes and generate Rossby-type waves at the cloud top (Sugimoto et al., 2014b). At the polar region, warm polar vortex zonally surrounded by a cold latitude band (cold collar) is well reproduced (Ando et al., 2016). As for horizontal kinetic energy spectra, divergent component is broadly (k>10) larger than rotational component compared with that on Earth (Kashimura et al., in preparation). Finally, recent results for thermal tides and small-scale waves will be shown in the presentation. Sugimoto, N. et al. (2014a), Baroclinic modes in the Venus atmosphere simulated by GCM, Journal of Geophysical Research: Planets, Vol. 119, p1950-1968. Sugimoto, N. et al. (2014b), Waves in a Venus general

  13. High-resolution numerical simulation of Venus atmosphere by AFES (Atmospheric general circulation model For the Earth Simulator)

    Science.gov (United States)

    Sugimoto, Norihiko; AFES project Team

    2016-10-01

    We have developed an atmospheric general circulation model (AGCM) for Venus on the basis of AFES (AGCM For the Earth Simulator) and performed a high-resolution simulation (e.g., Sugimoto et al., 2014a). The highest resolution is T639L120; 1920 times 960 horizontal grids (grid intervals are about 20 km) with 120 vertical layers (layer intervals are about 1 km). In the model, the atmosphere is dry and forced by the solar heating with the diurnal and semi-diurnal components. The infrared radiative process is simplified by adopting Newtonian cooling approximation. The temperature is relaxed to a prescribed horizontally uniform temperature distribution, in which a layer with almost neutral static stability observed in the Venus atmosphere presents. A fast zonal wind in a solid-body rotation is given as the initial state.Starting from this idealized superrotation, the model atmosphere reaches a quasi-equilibrium state within 1 Earth year and this state is stably maintained for more than 10 Earth years. The zonal-mean zonal flow with weak midlatitude jets has almost constant velocity of 120 m/s in latitudes between 45°S and 45°N at the cloud top levels, which agrees very well with observations. In the cloud layer, baroclinic waves develop continuously at midlatitudes and generate Rossby-type waves at the cloud top (Sugimoto et al., 2014b). At the polar region, warm polar vortex surrounded by a cold latitude band (cold collar) is well reproduced (Ando et al., 2016). As for horizontal kinetic energy spectra, divergent component is broadly (k > 10) larger than rotational component compared with that on Earth (Kashimura et al., in preparation). We will show recent results of the high-resolution run, e.g., small-scale gravity waves attributed to large-scale thermal tides. Sugimoto, N. et al. (2014a), Baroclinic modes in the Venus atmosphere simulated by GCM, Journal of Geophysical Research: Planets, Vol. 119, p1950-1968.Sugimoto, N. et al. (2014b), Waves in a Venus general

  14. Atmospheric Circulation of Exoplanets

    Science.gov (United States)

    Showman, A. P.; Cho, J. Y.-K.; Menou, K.

    2010-12-01

    We survey the basic principles of atmospheric dynamics relevant to explaining existing and future observations of exoplanets, both gas giant and terrestrial. Given the paucity of data on exoplanet atmospheres, our approach is to emphasize fundamental principles and insights gained from solar system studies that are likely to be generalizable to exoplanets. We begin by presenting the hierarchy of basic equations used in atmospheric dynamics, including the Navier-Stokes, primitive, shallow-water, and two-dimensional nondivergent models. We then survey key concepts in atmospheric dynamics, including the importance of planetary rotation, the concept of balance, and simple scaling arguments to show how turbulent interactions generally produce large-scale east-west banding on rotating planets. We next turn to issues specific to giant planets, including their expected interior and atmospheric thermal structures, the implications for their wind patterns, and mechanisms to pump their east-west jets. Hot Jupiter atmospheric dynamics are given particular attention, as these close-in planets have been the subject of most of the concrete developments in the study of exoplanetary atmospheres. We then turn to the basic elements of circulation on terrestrial planets as inferred from solar system studies, including Hadley cells, jet streams, processes that govern the large-scale horizontal temperature contrasts, and climate, and we discuss how these insights may apply to terrestrial exoplanets. Although exoplanets surely possess a greater diversity of circulation regimes than seen on the planets in our solar system, our guiding philosophy is that the multidecade study of solar system planets reviewed here provides a foundation upon which our understanding of more exotic exoplanetary meteorology must build.

  15. Land-sea thermal contrast determines the trend of Walker circulation simulated in atmospheric general circulation models

    Science.gov (United States)

    Yim, Bo Young; Yeh, Sang-Wook; Song, Hwan-Jin; Dommenget, Dietmar; Sohn, B. J.

    2017-06-01

    Strengthening or weakening of the Walker circulation can highly influence the global weather and climate variability by altering the location and strength of tropical heating. Therefore, there is considerable interest in understanding the mechanisms that lead to the trends in the Walker circulation intensity. Conventional wisdom indicates that a strengthening or weakening of the Walker circulation is primarily controlled by inhomogeneous sea surface temperature (SST) patterns across the tropical Pacific basin. However, we show that Atmospheric Model Intercomparison Project climate model simulations with identical SST forcing have different Walker circulation trends that can be linked to differences in land surface temperatures. More prominently, stronger land-sea thermal contrast leads to increases in the precipitation in South America as well as the sea level pressure in the eastern tropical Pacific through a local circulation, resulting in a strengthening of the Walker circulation trend. This implies that correctly simulating the land temperature in atmospheric models is crucial to simulating the intensity of the Walker circulation in the present climate as well as its future change.

  16. A system of conservative regridding for ice–atmosphere coupling in a General Circulation Model (GCM

    Directory of Open Access Journals (Sweden)

    R. Fischer

    2014-05-01

    Full Text Available The method of elevation classes, in which the ice surface model is run at multiple elevations within each grid cell, has proven to be a useful way for a low-resolution atmosphere inside a general circulation model (GCM to produce high-resolution downscaled surface mass balance fields for use in one-way studies coupling atmospheres and ice flow models. Past uses of elevation classes have failed to conserve mass and energy because the transformation used to regrid to the atmosphere was inconsistent with the transformation used to downscale to the ice model. This would cause problems for two-way coupling. A strategy that resolves this conservation issue has been designed and is presented here. The approach identifies three grids between which data must be regridded and five transformations between those grids required by a typical coupled atmosphere–ice flow model. This paper develops a theoretical framework for the problem and shows how each of these transformations may be achieved in a consistent, conservative manner. These transformations are implemented in Glint2, a library used to couple atmosphere models with ice models. Source code and documentation are available for download. Confounding real-world issues are discussed, including the use of projections for ice modeling, how to handle dynamically changing ice geometry, and modifications required for finite element ice models.

  17. Development of the GEOS-5 atmospheric general circulation model: evolution from MERRA to MERRA2

    Science.gov (United States)

    Molod, A.; Takacs, L.; Suarez, M.; Bacmeister, J.

    2015-05-01

    The Modern-Era Retrospective Analysis for Research and Applications-2 (MERRA2) version of the Goddard Earth Observing System-5 (GEOS-5) atmospheric general circulation model (AGCM) is currently in use in the NASA Global Modeling and Assimilation Office (GMAO) at a wide range of resolutions for a variety of applications. Details of the changes in parameterizations subsequent to the version in the original MERRA reanalysis are presented here. Results of a series of atmosphere-only sensitivity studies are shown to demonstrate changes in simulated climate associated with specific changes in physical parameterizations, and the impact of the newly implemented resolution-aware behavior on simulations at different resolutions is demonstrated. The GEOS-5 AGCM presented here is the model used as part of the GMAO MERRA2 reanalysis, global mesoscale simulations at 10 km resolution through 1.5 km resolution, the real-time numerical weather prediction system, and for atmosphere-only, coupled ocean-atmosphere and coupled atmosphere-chemistry simulations. The seasonal mean climate of the MERRA2 version of the GEOS-5 AGCM represents a substantial improvement over the simulated climate of the MERRA version at all resolutions and for all applications. Fundamental improvements in simulated climate are associated with the increased re-evaporation of frozen precipitation and cloud condensate, resulting in a wetter atmosphere. Improvements in simulated climate are also shown to be attributable to changes in the background gravity wave drag, and to upgrades in the relationship between the ocean surface stress and the ocean roughness. The series of resolution-aware parameters related to the moist physics was shown to result in improvements at higher resolutions and result in AGCM simulations that exhibit seamless behavior across different resolutions and applications.

  18. Martian atmospheric gravity waves simulated by a high-resolution general circulation model

    Science.gov (United States)

    Kuroda, Takeshi; Yiǧit, Erdal; Medvedev, Alexander S.; Hartogh, Paul

    2016-07-01

    Gravity waves (GWs) significantly affect temperature and wind fields in the Martian middle and upper atmosphere. They are also one of the observational targets of the MAVEN mission. We report on the first simulations with a high-resolution general circulation model (GCM) and present a global distributions of small-scale GWs in the Martian atmosphere. The simulated GW-induced temperature variances are in a good agreement with available radio occultation data in the lower atmosphere between 10 and 30 km. For the northern winter solstice, the model reveals a latitudinal asymmetry with stronger wave generation in the winter hemisphere and two distinctive sources of GWs: mountainous regions and the meandering winter polar jet. Orographic GWs are filtered upon propagating upward, and the mesosphere is primarily dominated by harmonics with faster horizontal phase velocities. Wave fluxes are directed mainly against the local wind. GW dissipation in the upper mesosphere generates a body force per unit mass of tens of m s^{-1} per Martian solar day (sol^{-1}), which tends to close the simulated jets. The results represent a realistic surrogate for missing observations, which can be used for constraining GW parameterizations and validating GCMs.

  19. AFES (Atmospheric general circulation model For the Earth Simulator) simulation for Venus

    Science.gov (United States)

    Sugimoto, Norihiko; Imamura, Takeshi; Takagi, Masahiro; Matsuda, Yoshihisa; Ando, Hiroki; Kashimura, Hiroki; Ohfuchi, Wataru; Enomoto, Takeshi; Takahashi, Yoshiyuki O.; Hayashi, Yoshi-Yuki

    We have developed an atmospheric general circulation model (AGCM) for Venus on the basis of AFES (AGCM For the Earth Simulator) and performed a very high-resolution simulation. The highest model resolution is T159L120; 0.75 degree times 0.75 degree latitude and longitude grids with 120 vertical layers (Δz is about 1 km). In the model, the atmosphere is dry and forced by the solar heating with the diurnal change and Newtonian cooling that relaxes the temperature to the zonally uniform basic temperature which has a virtual static stability of Venus with almost neutral layers. A fast zonal wind in a solid-body rotation is given as the initial state. In this paper, we will report several results newly obtained by this model. 1. Baroclinic instability appears in the cloud layer with small static stability and large vertical shear of the zonal flow. 2. Polar vortex is self-consistently generated by barotropic instability whose horizontal and vertical structure is consistent with the previous observations. 3. Kinetic energy spectra decreases by -5/3 power law in a range from wavenumber 4 to 45, whose range is different from that on Earth. Finally, we are now constructing the accurate radiation model of the Venus atmosphere.

  20. Radiative Impacts of Cloud Heterogeneity and Overlap in an Atmospheric General Circulation Model

    Science.gov (United States)

    Oreopoulos, L.; Lee, D.; Sud, Y. C.; Suarez, M. J.

    2012-01-01

    The radiative impacts of introducing horizontal heterogeneity of layer cloud condensate, and vertical overlap of condensate and cloud fraction are examined with the aid of a new radiation package operating in the GEOS-5 Atmospheric General Circulation Model. The impacts are examined in terms of diagnostic top-of-the-atmosphere shortwave (SW) and longwave (LW) cloud radiative effect (CRE) calculations for a range of assumptions and parameter specifications about the overlap. The investigation is conducted for two distinct cloud schemes, the one that comes with the standard GEOS-5 distribution, and another which has been recently used experimentally for its enhanced GEOS-5 distribution, and another which has been recently used experimentally for its enhanced cloud microphysical capabilities; both are coupled to a cloud generator allowing arbitrary cloud overlap specification. We find that cloud overlap radiative impacts are significantly stronger for the operational cloud scheme for which a change of cloud fraction overlap from maximum-random to generalized results to global changes of SW and LW CRE of approximately 4 Watts per square meter, and zonal changes of up to approximately 10 Watts per square meter. This is because of fewer occurrences compared to the other scheme of large layer cloud fractions and of multi-layer situations with large numbers of atmospheric being simultaneously cloudy, conditions that make overlap details more important. The impact on CRE of the details of condensate distribution overlap is much weaker. Once generalized overlap is adopted, both cloud schemes are only modestly sensitive to the exact values of the overlap parameters. We also find that if one of the CRE components is overestimated and the other underestimated, both cannot be driven towards observed values by adjustments to cloud condensate heterogeneity and overlap alone.

  1. Results of an interactively coupled atmospheric chemistry - general circulation model. Comparison with observations

    Energy Technology Data Exchange (ETDEWEB)

    Hein, R.; Dameris, M.; Schnadt, C. [and others

    2000-01-01

    An interactively coupled climate-chemistry model which enables a simultaneous treatment of meteorology and atmospheric chemistry and their feedbacks is presented. This is the first model, which interactively combines a general circulation model based on primitive equations with a rather complex model of stratospheric and tropospheric chemistry, and which is computational efficient enough to allow long-term integrations with currently available computer resources. The applied model version extends from the Earth's surface up to 10 hPa with a relatively high number (39) of vertical levels. We present the results of a present-day (1990) simulation and compare it to available observations. We focus on stratospheric dynamics and chemistry relevant to describe the stratospheric ozone layer. The current model version ECHAM4.L39(DLR)/CHEM can realistically reproduce stratospheric dynamics in the Arctic vortex region, including stratospheric warming events. This constitutes a major improvement compared to formerly applied model versions. However, apparent shortcomings in Antarctic circulation and temperatures persist. The seasonal and interannual variability of the ozone layer is simulated in accordance with observations. Activation and deactivation of chlorine in the polar stratospheric vortices and their interhemispheric differences are reproduced. The consideration of the chemistry feedback on dynamics results in an improved representation of the spatial distribution of stratospheric water vapor concentrations, i.e., the simulated meriodional water vapor gradient in the stratosphere is realistic. The present model version constitutes a powerful tool to investigate, for instance, the combined direct and indirect effects of anthropogenic trace gas emissions, and the future evolution of the ozone layer. (orig.)

  2. Arctic storms simulated in atmospheric general circulation models under uniform high, uniform low, and variable resolutions

    Science.gov (United States)

    Roesler, E. L.; Bosler, P. A.; Taylor, M.

    2016-12-01

    The impact of strong extratropical storms on coastal communities is large, and the extent to which storms will change with a warming Arctic is unknown. Understanding storms in reanalysis and in climate models is important for future predictions. We know that the number of detected Arctic storms in reanalysis is sensitive to grid resolution. To understand Arctic storm sensitivity to resolution in climate models, we describe simulations designed to identify and compare Arctic storms at uniform low resolution (1 degree), at uniform high resolution (1/8 degree), and at variable resolution (1 degree to 1/8 degree). High-resolution simulations resolve more fine-scale structure and extremes, such as storms, in the atmosphere than a uniform low-resolution simulation. However, the computational cost of running a globally uniform high-resolution simulation is often prohibitive. The variable resolution tool in atmospheric general circulation models permits regional high-resolution solutions at a fraction of the computational cost. The storms are identified using the open-source search algorithm, Stride Search. The uniform high-resolution simulation has over 50% more storms than the uniform low-resolution and over 25% more storms than the variable resolution simulations. Storm statistics from each of the simulations is presented and compared with reanalysis. We propose variable resolution as a cost-effective means of investigating physics/dynamics coupling in the Arctic environment. Future work will include comparisons with observed storms to investigate tuning parameters for high resolution models. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. SAND2016-7402 A

  3. Non-linear climate feedback analysis in an atmospheric general circulation model

    Energy Technology Data Exchange (ETDEWEB)

    Colman, R.A.; Power, S.B.; McAvaney, B.J. [Bureau of Meteorology, Melbourne, VIC (Australia). Research Centre

    1997-10-01

    A method is described for evaluating the `partial derivatives` of globally averaged top-of-atmosphere (TOA) radiation changes with respect to basicclimate model physical parameters. This method is used to analyse feedbacks in the Australian bureau of meteorology research centre general circulation model. The parameters considered are surface temperature, water vapour, lapse rate and cloud cover. The climate forcing which produces the changes is a globally uniform sea surface temperature (SST) perturbation. The first and second order differentials of model parameters with respect to the forcing (i.e. SST changes) are estimated from quadratic least square fitting. Except for total cloud cover, variables are found to be strong functions of global SST. Strongly nonlinear variations of lapse rate and high cloud amount and height appear to relate to the nonlinear response in penetrative convection. Globally averaged TOA radiation differentials with respect to model parameters are also evaluated. With the exception of total cloud contributions, a high correlation is generally found to exist, on the global mean level, between TOA radiation and the respective parameter perturbations. The largest nonlinear terms contributing to radiative changes are those due to lapse rate and high cloud. The contributions of linear and nonlinear terms to the overall radiative response from a 4 K SST perturbation are assessed. Significant nonlinear responses are found to be associated with lapse rate, water vapour and cloud changes. Although the exact magnitude of these responses is likely to be a function of the particular model as well as the imposed SST perturbation pattern, the present experiments flag these as processes which cannot properly be understood from linear theory in the evaluation of climate change sensitivity. (orig.) With 6 figs., 4 tabs., 28 refs.

  4. Atmospheric circulation associated with extreme generalized frosts persistence in central-southern South America

    Energy Technology Data Exchange (ETDEWEB)

    Mueller, Gabriela V. [Centro de Investigaciones Cientificas y Transferencia de Tecnologia a la Produccion, Diamante (CICYTTTP-CONICET), Diamante, Entre Rios (Argentina); Berri, Guillermo J. [Servicio Meteorologico Nacional - CONICET, Buenos Aires (Argentina)

    2012-03-15

    Generalized frosts (GF) in central-southern South America have a strong impact due to their spatial extension, and they are especially important when they become persistent. This paper aims at identifying the atmospheric circulation features that determine the extreme GF persistence, i.e. very persistent and without persistence, and the differences between them, during the 1961-1990 winters. Since the GF without persistence group outnumbers the other one, two subgroups are composed with events selected from winters with maximum and minimum frequency of GF occurrence, respectively. Additionally, the individual event of July 1988 within the very persistent GF group is analyzed due to its exceptional persistence. GF persistence is mainly conditioned by two large-scale dynamic factors. One is the Rossby wave train propagation across the Pacific Ocean, and the other one is the location with respect to the continent and the magnitude of the confluence in the jet entrance region in subtropical latitudes. A predominantly meridional Rossby wave train propagation with a confluence region to the west of the continent prior to the event favors GF with intermediate (null) persistence depending on the greater (lesser) jet acceleration. This is conditioned by the magnitude of the confluence, which, in turn, depends on the disposition of the wave train propagation pattern. Instead, an essentially zonal propagation with a confluence region to the east of the continent favors the GF persistence for several days, yet if there is no confluence the event does not persist. The greatest persistence of an event combines the confluence/diffluence of the jet entrance/exit region, which depends on the disposition with respect to the continent of the zonally propagating Rossby wave trains. (orig.)

  5. Analysing and combining atmospheric general circulation model simulations forced by prescribed SST: northern extratropical response

    Directory of Open Access Journals (Sweden)

    K. Maynard

    2001-06-01

    Full Text Available The ECHAM 3.2 (T21, ECHAM 4 (T30 and LMD (version 6, grid-point resolution with 96 longitudes × 72 latitudes atmospheric general circulation models were integrated through the period 1961 to 1993 forced with the same observed Sea Surface Temperatures (SSTs as compiled at the Hadley Centre. Three runs were made for each model starting from different initial conditions. The mid-latitude circulation pattern which maximises the covariance between the simulation and the observations, i.e. the most skilful mode, and the one which maximises the covariance amongst the runs, i.e. the most reproducible mode, is calculated as the leading mode of a Singular Value Decomposition (SVD analysis of observed and simulated Sea Level Pressure (SLP and geopotential height at 500 hPa (Z500 seasonal anomalies. A common response amongst the different models, having different resolution and parametrization should be considered as a more robust atmospheric response to SST than the same response obtained with only one model. A robust skilful mode is found mainly in December-February (DJF, and in June-August (JJA. In DJF, this mode is close to the SST-forced pattern found by Straus and Shukla (2000 over the North Pacific and North America with a wavy out-of-phase between the NE Pacific and the SE US on the one hand and the NE North America on the other. This pattern evolves in a NAO-like pattern over the North Atlantic and Europe (SLP and in a more N-S tripole on the Atlantic and European sector with an out-of-phase between the middle Europe on the one hand and the northern and southern parts on the other (Z500. There are almost no spatial shifts between either field around North America (just a slight eastward shift of the highest absolute heterogeneous correlations for SLP relative to the Z500 ones. The time evolution of the SST-forced mode is moderatly to strongly related to the ENSO/LNSO events but the spread amongst the ensemble of runs is not systematically related

  6. Investigating the Climate Impacts of Black Carbon in GFDL's AM2.1 Atmospheric General Circulation Model

    Science.gov (United States)

    Persad, G.; Ming, Y.

    2009-12-01

    Black carbon aerosols (BC) have been shown to significantly impact the climate system through their radiative effects. Many of the physical processes that drive BC climate impacts, however, are not yet well characterized across general circulation models. This has made it increasingly difficult to reach a consensus within the modeling community on how best to calculate BC radiative forcing in a way that is both representative and comparable between models. Calculation methodologies that include atmospheric perturbations, while more representative, are also more sensitive to model-specific representation of physical processes than those that do not. This study investigates the physical processes behind atmospheric perturbations due to BC using a modified version of the Geophysical Fluid Dynamics Laboratory's Atmospheric General Circulation Model (AM2.1). The preindustrial control case is perturbed by inserting a globally uniform BC burden into the atmosphere at a series of layers, and the TOA flux change is analyzed. We use a theoretical framework to establish the robustness of the atmospheric response produced by the model in order to determine the comparability of forcing calculations derived using atmospheric perturbations in AM2.1. Responses vary based on the cloud environment and the level of BC emplacement. Results, however, exhibit robust correlation with theory with positive implications for the inclusion of the atmospheric response in the calculation of BC radiative forcing.

  7. Seasonal Water Transport in the Atmosphere of Mars: Applications of a Mars General Circulation Model Using Mars Global Surveyor Data

    Science.gov (United States)

    Hollingsworth, Jeffery L.; Bridger, Alison F. C.; Haberle, Robert M.

    1999-01-01

    This is a Final Report for a Joint Research Interchange (JRI) between NASA Ames Research Center and San Jose State University, Department of Meteorology. We present below a summary of progress made during the duration of this JRI. The focus of this JRI has been to investigate seasonal water vapor transport in the atmosphere of Mars and its effects on the planet's present climate. To this end, the primary task has been to adapt a new dynamical processor for the adiabatic tendencies of the atmospheric circulation into the NASA Ames Mars general circulation model (MGCM). Using identical boundary and initial conditions, several comparative tests between the new and old MGCMs have been performed and the nature of the simulated circulations have been diagnosed. With confidence that the updated version of the Ames MGCM produces quite similar mean and eddy circulation statistics, the new climate model is well poised as a tool to pursue fundamental questions related to the spatial and seasonal variations of atmospheric water vapor on Mars, and to explore exchanges of water with non-atmospheric reservoirs and transport within its atmosphere. In particular, the role of surface sources and sinks can be explored, the range of water-vapor saturation altitudes can be investigated, and plausible precipitation mechanisms can be studied, for a range of atmospheric dust loadings. Such future investigations can contribute to a comprehensive study of surface inventories, exchange mechanisms, and the relative importance of atmospheric transport Mars' water cycle. A listing of presentations made and manuscripts submitted during the course of this project is provided.

  8. Variability in the general atmospheric circulation, precipitation and runoff in Eastern Europe

    Science.gov (United States)

    Ivanov, Sergiy; Svetlitchnyi, Alexander; Matygin, Alexander; Ivus, Galina; Palamarchuk, Julia

    2010-05-01

    Using different databases, changes of atmospheric circulation, regional precipitation, and runoff in Eastern Europe are analysed. The focus of the study is to search relationships between large-scale atmospheric flow characteristics and wet days as well as subsequent runoff in major rivers of the region. Unfortunately, various precipitation datasets developed in the last decades show significant differences in spatial and temporal distribution of available information that is difficult to reconcile. Nevertheless, results indicate that regional precipitation changes can be attributed to changes in large-scale atmospheric circulation. In particular, the zonal shift in storm tracks and associated atmospheric water vapor transfer changes cause a decrease in precipitation over the southern part of Eastern Europe, in particular, over the Danube River Basin. On the other hand, precipitation over the northern half of Eastern Europe increases, with largest increases over the Eastern European Plateau and the Dnepr River Basin. Thermodynamic changes also contribute to precipitation changes, mainly due to an increase in atmospheric precipitable water in the cold season (and, thus, increase in snowfall) in response to rising temperatures. Runoff of the major rivers in Eastern Europe correlates with precipitation over their basins less than it may be expected. Moreover, for the last decades the opposite tendencies in precipitation and runoff for Danube have been observed. This can be explained by the anthropogenic impact on the runoff for which the dynamics do not coincide with the tendencies in the natural factors responsible for runoff formation. In 1990, the fresh water withdrawal in the Ukraine was around 30 km3 that is comparable to local runoff resources of the nation. At the same time, the water consumption was around 11 km3. For socio-economic reasons, in the 1990s the water withdrawal and consumption sharply decreased when their minimums were reached only in 2004, being

  9. A passive dust experiment toward a high resolution simulation of the Martian atmospheric general circulation

    Science.gov (United States)

    Takahashi, Y. O.; Hayashi, Y.-Y.; Odaka, M.; Ohfuchi, W.

    2005-08-01

    A high resolution simulation of the Martian atmosphere is performed to examine the appearance of small to medium scale atmospheric disturbances and their effects on the dust lifting and transfer processes. The dynamical core of the Martian GCM used in this study is that of the terrestrial GCM, AFES (Atmospheric GCM for Earth Simulator, Ohfuchi et al., Journal of the Earth Simulator, 1, 8, 2004). The physical processes of the present model are those developed by our group so far (the earlier version of our Martian GCM and its physical processes are described in Takahashi et al., JGR, 108, 5013, doi:10.1029/2001JE001638, 2003). A test simulation is performed with a relatively low resolution of T79L24, which is equivalent to about 90 km grid size on Mars. Moreover, this simulation is a "passive dust experiment" in the sense that dust is assumed to be radiatively inert. Atmospheric heating due to dust absorption is given separately from a zonally uniform distribution of dust with the latitudinal profile following the MGS-TES observation. The result of test simulation shows clear frontal structures in the baroclinic zones at spring and fall seasons. In addition, medium scale vortex generations are observed in the lees of high mountains in the northern hemisphere. In this test simulation, dust lifting events occur only in some limited areas and limited seasonal dates. Major dust lifting regions include the vicinity of polar caps, the eastern flank of Tharsis plateau, the southern low latitude belt, and the Hellas basin. These regions roughly coincide with those of dust storms observed by the MGS and dust lifting regions reported by earlier GCM studies. It is suggested that the strong wind, which is associated with the fronts and the local circulations induced by topographic variation, plays an important role to lift dust and generate dust storms.

  10. Recent progress in the development of the general circulation and climate model of the martian atmosphere MART-ACC

    Science.gov (United States)

    Meister, C.-V.; Hartogh, P.; Sonnemann, G.; Berger, U.; Feofilov, A.; Kutepov, A.; Elbern, H.

    The seasonal dependence of the Martian general circulation and climate is studied within a fully non-linear, global and three-dimensional hydrodynamic Eulerian gridpoint model which extends from the surface of the planet to the lower thermosphere. Therefore the dust-free pure carbon dioxide model MART-ACC which was presented by Meister et al. on the EGS-AGU-EUG Assembly in Nice 2003 was essentially improved. Especially, the parametrizations for the solar and infrared radiation transport are further developed. The seasonal and diurnal dependences of the atmospheric LTE heating rates obtained by the general circulation and climate model are also compared with rates based on the nadir temperature profiles published in the Mars Global Surveyor Data Archives distributed by the NASA Planetary Data System (http://emma.la.asu.edu/data_archives). Besides, the influence of the surface albedo on the atmospheric heating is studied. Further non-LTE corrections of the heating rates at larger atmospheric altitudes are estimated and compared with results of other working groups. Basing on the calculations of the heating rates and taking into account influences of diffusion by gravity waves and molecular collisions, the temperature profiles and wind velocities of the atmosphere are obtained. Finally, first attempts to describe chemical processes are shown.

  11. Snow and cloud feedbacks modelled by an atmospheric general circulation model

    Energy Technology Data Exchange (ETDEWEB)

    Colman, R.A.; McAvaney, B.J.; Fraser, J.R. [Bureau of Meteorology Research Center, Victoria (Austria)] [and others

    1994-01-01

    One of the most important parametrizations in general circulation models used for climate change experiments is that of the surface albedo. The results an albedo feedback experiment carried out under the auspices of the US Department of Energy are presented. An analysis of long and short wave components of the model response shows that short wave response dominates changes in fixed to variable albedo experiments, but that long wave response dominates in clear to cloudy sky changes. Cloud distribution chances are also discussed and are related to changes in global sensitivity. At the surface, the heat balance change for perturbed sea surface temperatures is dominated by changes in latent heat flux and downward long wave radiation. If albedo is freed up however, the major contrast lies in the change in surface reflected short wave radiation, amplified by changes in downward short wave radiation caused by cloud amount changes. 14 refs., 7 figs., 6 tabs.

  12. A comparison of vertical coordinate systems for numerical modeling of the general circulation of the atmosphere

    Science.gov (United States)

    Heikes, Ross Parker

    The Colorado State University general circulation model has been dramatically changed in the last few years. The horizontal grid has been changed from a latitude/longitude grid with an Arakawa C-grid staggering of mass, zonal and meridional wind to a geodesic grid in which mass, vorticity and divergence are predicted at cell centers. Throughout this change the vertical structure has remained unchanged. Now, we are poised to revamp the vertical structure of the model. We have studied several possible alternative vertical coordinate systems in order to pick the one best suited for long-term climate prediction. After a brief historical review of various vertical coordinates used in numerical modeling, we will focus on three models---one based on the co-called sigma-coordinate, on based on a pure isentropic coordinate and one based a hybrid sigma-θ vertical coordinate. We will show how the continuous equations are transformed to finite-difference analogs, and how the transformation preserves many of the conservation properties of the continuous equations. We will show how different vertical discretization of the prognostic variables---Lorenz or Chamey-Phillips vertical staggering---can influence the quality of the numerical simulation. Many fundamental questions about the isentropic- and hybrid-coordinate need to be answered. Since the isentropic-coordinate surfaces behave as Lagrangian surfaces, the ideas of grid resolution from the Eulerian framework are not applicable. Also, in the isentropic- and hybrid-coordinates, there is a much greater variation in layer thickness. Excessive vertical resolution in the extra-tropics where coordinate surfaces are close, may become inadequately coarse in the tropics as the coordinate surfaces spread apart. We will show how the quality of the Held and Suarez test case changes as a function of resolution. We have performed a simulation of stratospheric sudden warming with the isentropic-coordinate model. We will compare our results

  13. Simulating organic species with the global atmospheric chemistry general circulation model ECHAM5/MESSy1: a comparison of model results with observation

    NARCIS (Netherlands)

    Pozzer, A.; Jöckel, P.; Tost, H.; Sander, R.; Ganzeveld, L.N.; Kerkweg, A.; Lelieveld, J.

    2007-01-01

    The atmospheric-chemistry general circulation model ECHAM5/MESSy1 is evaluated with observations of different organic ozone precursors. This study continues a prior analysis which focused primarily on the representation of atmospheric dynamics and ozone. We use the results of the same reference

  14. Sensitivity of the climate response of an atmospheric general circulation model to changes in convective parameterization and horizontal resolution

    Energy Technology Data Exchange (ETDEWEB)

    Colman, R.A.; Mcavaney, B.J. [Bureau of Meteorology Research Centre, Melbourne (Australia)

    1995-02-01

    Three equilibrium doubled CO2 experiments have been performed using the Bureau of Meteorology Research Centre atmospheric general circulation model. These experiments used identical versions of the model, apart from changes in the convective parameterization and the horizontal resolution. The penetrative convection parameterizations used were variants of the Tiedtke (1989) mass flux and Kuo (1974) schemes. The shallow convection was also varied in strength. In the control climate the mass flux scheme produces a warmer, moister troposphere, with substantially more high cloud than the Kuo scheme. The precipitation distributions agree reasonably with observations overall, although the mass flux scheme gives improvements in some regions. The increase in resolution is generally found to have a smaller impact upon the climate than the change in convection. Under a doubling of atmospheric CO2, the equilibrium responses of all three experiments were extremely similar in surface and tropospheric temperatures and humidity changes. The model response is at the low end of the scale of simulated climate change, consistent with a strong negative feedback found due to clouds. This feedback is similar to that found in earlier fixed season experiments. It appears to be insensitive to differences in cloud cover simulated in the control climates of the present experiments.

  15. Atmospheric Circulation of Exoplanets

    OpenAIRE

    Showman, Adam P.; Cho, James Y-K.; Menou, Kristen

    2009-01-01

    We survey the basic principles of atmospheric dynamics relevant to explaining existing and future observations of exoplanets, both gas giant and terrestrial. Given the paucity of data on exoplanet atmospheres, our approach is to emphasize fundamental principles and insights gained from Solar-System studies that are likely to be generalizable to exoplanets. We begin by presenting the hierarchy of basic equations used in atmospheric dynamics, including the Navier-Stokes, primitive, shallow-wate...

  16. How well do state-of-the-art atmosphere-ocean general circulation models reproduce atmospheric teleconnection patterns?

    Directory of Open Access Journals (Sweden)

    Dörthe Handorf

    2012-11-01

    Full Text Available This article evaluates the ability of state-of-the-art climate models to reproduce the low-frequency variability of the mid-tropospheric winter flow of the Northern Hemisphere in terms of atmospheric teleconnection patterns. Therefore, multi-model simulations for present-day conditions, performed for the 4th assessment report of the Intergovernmental Panel on Climate Change, have been analysed and compared with re-analysis data sets. The spatial patterns of atmospheric teleconnections are reproduced reasonably by most of the models. The comparison of coupled with atmosphere-only runs confirmed that a better representation of the forcing by sea surface temperatures has the potential to slightly improve the representation of only wave train-like patterns. Due to internally generated climate variability, the models are not able to reproduce the observed temporal behaviour. Insights into the dynamical reasons for the limited skill of climate models in reproducing teleconnections have been obtained by studying the relation between major teleconnections and zonal wind variability patterns. About half of the models are able to reproduce the observed relationship. For these cases, the quality of simulated teleconnection patterns is largely determined by the quality of zonal wind variability patterns. Therefore, improvements of simulated eddy-mean flow interaction have the potential to improve the atmospheric teleconnections.

  17. The atmospheric chemistry general circulation model ECHAM5/MESSy1: consistent simulation of ozone from the surface to the mesosphere

    Directory of Open Access Journals (Sweden)

    P. Jöckel

    2006-01-01

    Full Text Available The new Modular Earth Submodel System (MESSy describes atmospheric chemistry and meteorological processes in a modular framework, following strict coding standards. It has been coupled to the ECHAM5 general circulation model, which has been slightly modified for this purpose. A 90-layer model setup up to 0.01 hPa was used at spectral T42 resolution to simulate the lower and middle atmosphere. With the high vertical resolution the model simulates the Quasi-Biennial Oscillation. The model meteorology has been tested to check the influence of the changes to ECHAM5 and the radiation interactions with the new representation of atmospheric composition. In the simulations presented here a Newtonian relaxation technique was applied in the tropospheric part of the domain to weakly nudge the model towards the analysed meteorology during the period 1998–2005. This allows an efficient and direct evaluation with satellite and in-situ data. It is shown that the tropospheric wave forcing of the stratosphere in the model suffices to reproduce major stratospheric warming events leading e.g. to the vortex split over Antarctica in 2002. Characteristic features such as dehydration and denitrification caused by the sedimentation of polar stratospheric cloud particles and ozone depletion during winter and spring are simulated well, although ozone loss in the lower polar stratosphere is slightly underestimated. The model realistically simulates stratosphere-troposphere exchange processes as indicated by comparisons with satellite and in situ measurements. The evaluation of tropospheric chemistry presented here focuses on the distributions of ozone, hydroxyl radicals, carbon monoxide and reactive nitrogen compounds. In spite of minor shortcomings, mostly related to the relatively coarse T42 resolution and the neglect of inter-annual changes in biomass burning emissions, the main characteristics of the trace gas distributions are generally reproduced well. The MESSy

  18. Initiation of a Marinoan Snowball Earth in a state-of-the-art atmosphere-ocean general circulation model

    Energy Technology Data Exchange (ETDEWEB)

    Voigt, Aiko [Max Planck Institute for Meteorology, Hamburg (Germany); International Max Planck Research School on Earth System Modelling, Hamburg (Germany); Abbot, Dorian S.; Pierrehumbert, Raymond T. [Department of Geophysical Sciences, University of Chicago, Chicago, Illinois (United States); Marotzke, Jochem [Max Planck Institute for Meteorology, Hamburg (Germany)

    2011-07-01

    The apparent existence of low-latitude land glaciers at sea level during the Marinoan ({proportional_to}635 Ma) has led to the proposal that these glaciations were accompanied by completely ice-covered oceans. These states have become popular under the term ''Snowball Earth.'' In this contribution, we study the initiation of a Marinoan Snowball Earth with the most sophisticated model ever used for this purpose, the atmosphere-ocean general circulation model ECHAM5/MPI-OM. In particular, we focus on the total solar irradiance and atmospheric concentration of carbon dioxide needed to trigger a Marinoan Snowball Earth. We find that Snowball initiation in this model is much easier than found in various previous modelling studies. A zero-dimensional energy balance model is used to predict the Snowball Earth bifurcation point from only the equilibrium global mean ocean potential temperature for present-day TSI. We do not find stable states with sea-ice cover above 55%, and land conditions are such that glaciers could not grow with sea-ice cover of 55%. Therefore, none of our simulations qualifies as a ''slushball'' solution, with the caveat that mountains are not included in our study.

  19. Impact of absorbing aerosols on the simulation of climate over the Indian region in an atmospheric general circulation model

    Directory of Open Access Journals (Sweden)

    A. Chakraborty

    2004-04-01

    Full Text Available The impact of anthropogenic absorbing aerosols (such as soot on the climate over the Indian region has been studied using the NCMRWF general circulation model. The absorbing aerosols increase shortwave radiative heating of the lower troposphere and reduce the heating at the surface. These effects have been incorporated as heating of the lower troposphere (up to 700hPa and cooling over the continental surface based on INDOEX measurements. The heating effect is constant in the pre-monsoon season and reduces to zero during the monsoon season. It is shown that even in the monsoon season when the aerosol forcing is zero, there is an overall increase in rainfall and a reduction in surface temperature over the Indian region. The rainfall averaged over the Tropics shows a small reduction in most of the months during the January to September period. The impact of aerosol forcing, the model's sensitivity to this forcing and its interaction with model-physics has been studied by changing the cumulus parameterization from the Simplified Arakawa-Schubert (SAS scheme to the Kuo scheme. During the pre-monsoon season the major changes in precipitation occur in the oceanic Inter Tropical Convergence Zone (ITCZ, where both the schemes show an increase in precipitation. This result is similar to that reported in Chung2002. On the other hand, during the monsoon season the changes in precipitation in the continental region are different in the SAS and Kuo schemes. It is shown that the heating due to absorbing aerosols changes the vertical moist-static stability of the atmosphere. The difference in the precipitation changes in the two cumulus schemes is on account of the different responses in the two parameterization schemes to changes in vertical stability. Key words. Atmospheric composition and structure (aerosols and particles – Meteorology and atmospheric dynamics (tropical meteorology; precipitation

  20. Optimizing an atmospheric general circulation model for weather prediction (10km) and climate (100km) resolutions.

    Science.gov (United States)

    Putman, W.; Suarez, M.; Molod, A.; Takacs, L.; Barahona, D.

    2016-12-01

    At the GMAO we have developed a multi-scale modeling and assimilation system (GEOS-5) that is used at very different resolutions for numerical weather prediction (NWP), reanalysis, seasonal forecasting, and longer-term climate applications. We have tried to develop tunings of the AGCM parameterizations that allow us to use the model in this range of resolutions (Molod et al, 2015). In this presentation, we focus on several parameters that (in our system, at least) that appear to be most effectively tuned for achieving the desired seamlessness: (1) the critical relative humidity used in the precipitation PDF scheme, (2) the maximum allowed entrainment in the deep convective parameterization, (3) the timescales for shallow and deep convection, and (4) the physics/dynamics coupling timestep itself. Although some of these parameters require only choosing optimum values at each resolution, we find that those involved with the balance between resolved and parameterized deep convection must be varied in a flow-dependent way. In the presentation we describe a scheme to do this that uses low-level moisture in the free atmosphere to identify regions with active resolved convection. We will also argue, based on the sensitivity we see to physics/dynamics coupling timestep, that it may be necessary to bring water vapor transport and simple condensation and heating into the dynamics, since their time scales are comparable to those of resolved vertical motions. We will also discuss the tuning procedure, and in particular, the metrics used to select parameters. Using high-resolution observations of global brightness temperature, precipitation, and water vapor we explore the characteristics of weather produced within a well-tuned climate simulation. Re-forecasting experiments can be used to explore the ideal tuning for producing the best anomaly correlation and root mean squared (RMS) error statistics for the basic state variables in a five day forecast validated against high

  1. Some lessons and thoughts from development of an old-fashioned high-resolution atmospheric general circulation model

    Science.gov (United States)

    Ohfuchi, Wataru; Enomoto, Takeshi; Yoshioka, Mayumi K.; Takaya, Koutarou

    2014-05-01

    Some high-resolution simulations with a conventional atmospheric general circulation model (AGCM) were conducted right after the first Earth Simulator started operating in the spring of 2002. More simulations with various resolutions followed. The AGCM in this study, AFES (Agcm For the Earth Simulator), is a primitive equation spectral transform method model with a cumulus convection parameterization. In this presentation, some findings from comparisons between high and low-resolution simulations, and some future perspectives of old-fashioned AGCMs will be discussed. One obvious advantage of increasing resolution is capability of resolving the fine structures of topography and atmospheric flow. By increasing resolution from T39 (about 320 km horizontal grid interval) to T79 (160 km), to T159 (80 km) to T319 (40 km), topographic precipitation over Japan becomes increasingly realistic. This feature is necessary for climate and weather studies involving both global and local aspects. In order to resolve submesoscale (about 100 km horizontal scale) atmospheric circulation, about 10-km grid interval is necessary. Comparing T1279 (10 km) simulations with T319 ones, it is found that, for example, the intensity of heavy rain associated with Baiu front and the central pressure of typhoon become more realistic. These realistic submesoscale phenomena should have impact on larger-sale flow through dynamics and thermodynamics. An interesting finding by increasing horizontal resolution of a conventional AGCM is that some cumulus convection parameterizations, such as Arakawa-Schubert type scheme, gradually stop producing precipitation, while some others, such as Emanuel type, do not. With the former, the grid condensation increases with the model resolution to compensate. Which characteristics are more desirable is arguable but it is an important feature one has to consider when developing a high-resolution conventional AGCM. Many may think that conventional primitive equation

  2. Assessing the Tangent Linear Behaviour of Common Tracer Transport Schemes and Their Use in a Linearised Atmospheric General Circulation Model

    Science.gov (United States)

    Holdaway, Daniel; Kent, James

    2015-01-01

    The linearity of a selection of common advection schemes is tested and examined with a view to their use in the tangent linear and adjoint versions of an atmospheric general circulation model. The schemes are tested within a simple offline one-dimensional periodic domain as well as using a simplified and complete configuration of the linearised version of NASA's Goddard Earth Observing System version 5 (GEOS-5). All schemes which prevent the development of negative values and preserve the shape of the solution are confirmed to have nonlinear behaviour. The piecewise parabolic method (PPM) with certain flux limiters, including that used by default in GEOS-5, is found to support linear growth near the shocks. This property can cause the rapid development of unrealistically large perturbations within the tangent linear and adjoint models. It is shown that these schemes with flux limiters should not be used within the linearised version of a transport scheme. The results from tests using GEOS-5 show that the current default scheme (a version of PPM) is not suitable for the tangent linear and adjoint model, and that using a linear third-order scheme for the linearised model produces better behaviour. Using the third-order scheme for the linearised model improves the correlations between the linear and non-linear perturbation trajectories for cloud liquid water and cloud liquid ice in GEOS-5.

  3. Modeling of water stable isotopes in the ECHAM6 atmospheric general circulation model: current status and perspectives

    Science.gov (United States)

    Cauquoin, Alexandre; Werner, Martin; Lohmann, Gerrit

    2017-04-01

    We present here the first results for present-day conditions of the ongoing implementation of water stables isotopes in the latest version of the ECHAM atmospheric general circulation model, ECHAM6, enhanced by the JSBACH interactive land surface scheme (ECHAM6-wiso). Major changes with respect to its predecessor ECHAM5 have to do with the treatment of shortwave radiative transfer, the development of a new surface albedo representation, a new aerosol climatology, the height of the model top, and a more complex representation of the land surface [1]. Besides, a new five-layer soil hydrology scheme can be used instead of the single soil moisture reservoir in ECHAM5/JSBACH [2]. Our first analyses of the ECHAM6-wiso results concentrate on a detailed comparison to the previous model release, ECHAM5-wiso, and potential improvements in simulating the water stable isotopes signal due to overall model enhancements. This study represents the first step of the incorporation of water stable isotope tracers in all components of the fully coupled Earth system model MPI-ESM. The project is part of the PalMod initiative ("Paleo Modelling: A national paleo climate modelling initiative"), funded by the German Federal Ministry of Education and Science (BMBF). [1] Stevens et al., 2013, JAMES, 5, 146-172. [2] Hagemann and Stacke, 2015, Clim. Dyn., 44, 1731-1750.

  4. Initiation of a Marinoan Snowball Earth in a state-of-the-art atmosphere-ocean general circulation model

    Directory of Open Access Journals (Sweden)

    A. Voigt

    2011-03-01

    Full Text Available We study the initiation of a Marinoan Snowball Earth (~635 million years before present with the state-of-the-art atmosphere-ocean general circulation model ECHAM5/MPI-OM. This is the most sophisticated model ever applied to Snowball initiation. A comparison with a pre-industrial control climate shows that the change of surface boundary conditions from present-day to Marinoan, including a shift of continents to low latitudes, induces a global-mean cooling of 4.6 K. Two thirds of this cooling can be attributed to increased planetary albedo, the remaining one third to a weaker greenhouse effect. The Marinoan Snowball Earth bifurcation point for pre-industrial atmospheric carbon dioxide is between 95.5 and 96% of the present-day total solar irradiance (TSI, whereas a previous study with the same model found that it was between 91 and 94% for present-day surface boundary conditions. A Snowball Earth for TSI set to its Marinoan value (94% of the present-day TSI is prevented by doubling carbon dioxide with respect to its pre-industrial level. A zero-dimensional energy balance model is used to predict the Snowball Earth bifurcation point from only the equilibrium global-mean ocean potential temperature for present-day TSI. We do not find stable states with sea-ice cover above 55%, and land conditions are such that glaciers could not grow with sea-ice cover of 55%. Therefore, none of our simulations qualifies as a "slushball" solution. While uncertainties in important processes and parameters such as clouds and sea-ice albedo suggest that the Snowball Earth bifurcation point differs between climate models, our results contradict previous findings that Snowball Earth initiation would require much stronger forcings.

  5. Influence of Last Glacial Maximum boundary conditions on the global water isotope distribution in an atmospheric general circulation model

    Directory of Open Access Journals (Sweden)

    T. Tharammal

    2013-03-01

    Full Text Available To understand the validity of δ18O proxy records as indicators of past temperature change, a series of experiments was conducted using an atmospheric general circulation model fitted with water isotope tracers (Community Atmosphere Model version 3.0, IsoCAM. A pre-industrial simulation was performed as the control experiment, as well as a simulation with all the boundary conditions set to Last Glacial Maximum (LGM values. Results from the pre-industrial and LGM simulations were compared to experiments in which the influence of individual boundary conditions (greenhouse gases, ice sheet albedo and topography, sea surface temperature (SST, and orbital parameters were changed each at a time to assess their individual impact. The experiments were designed in order to analyze the spatial variations of the oxygen isotopic composition of precipitation (δ18Oprecip in response to individual climate factors. The change in topography (due to the change in land ice cover played a significant role in reducing the surface temperature and δ18Oprecip over North America. Exposed shelf areas and the ice sheet albedo reduced the Northern Hemisphere surface temperature and δ18Oprecip further. A global mean cooling of 4.1 °C was simulated with combined LGM boundary conditions compared to the control simulation, which was in agreement with previous experiments using the fully coupled Community Climate System Model (CCSM3. Large reductions in δ18Oprecip over the LGM ice sheets were strongly linked to the temperature decrease over them. The SST and ice sheet topography changes were responsible for most of the changes in the climate and hence the δ18Oprecip distribution among the simulations.

  6. Fractionation and current time trends of PCB congeners: evolvement of distributions 1950–2010 studied using a global atmosphere-ocean general circulation model

    OpenAIRE

    G. Lammel; I. Stemmler

    2012-01-01

    PCBs are ubiquitous environmental pollutants expected to decline in abiotic environmental media in response to decreasing primary emissions since the 1970s. A coupled atmosphere-ocean general circulation model with embedded dynamic sub-models for atmospheric aerosols and the marine biogeochemistry and air-surface exchange processes with soils, vegetation and the cryosphere is used to study the transport and fate of four PCB congeners covering a range of 3–7 chlorine atoms.
    &...

  7. Fractionation and current time trends of PCB congeners: evolvement of distributions 1950–2010 studied using a global atmosphere-ocean general circulation model

    OpenAIRE

    G. Lammel; I. Stemmler

    2012-01-01

    PCBs are ubiquitous environmental pollutants expected to decline in abiotic environmental media in response to decreasing primary emissions since the 1970s. A coupled atmosphere-ocean general circulation model with embedded dynamic sub-models for atmospheric aerosols and the marine biogeochemistry and air-surface exchange processes with soils, vegetation and the cryosphere is used to study the transport and fate of four PCB congeners covering a range of 3–7 chlorine atoms.

  8. The impact of oceanic heat transport on the atmospheric circulation

    OpenAIRE

    M.-A. Knietzsch; A. Schröder; V. Lucarini; F. Lunkeit

    2015-01-01

    A general circulation model of intermediate complexity with an idealized Earth-like aquaplanet setup is used to study the impact of changes in the oceanic heat transport on the global atmospheric circulation. Focus is on the atmospheric mean meridional circulation and global thermodynamic properties. The atmosphere counterbalances to a large extent the imposed changes in the oceanic heat transport, but, nonetheless, significant modifications to the atmospheric general ci...

  9. Impact of atmospheric convection on south Tibet summer precipitation isotopologue composition using a combination of in situ measurements, satellite data, and atmospheric general circulation modeling

    Science.gov (United States)

    He, You; Risi, Camille; Gao, Jing; Masson-Delmotte, Valérie; Yao, Tandong; Lai, Chun-Ta; Ding, Yongjian; Worden, John; Frankenberg, Christian; Chepfer, Helene; Cesana, Gregory

    2015-05-01

    Precipitation isotopologues recorded in natural archives from the southern Tibetan Plateau may document past variations of Indian monsoon intensity. The exact processes controlling the variability of precipitation isotopologue composition must therefore first be deciphered and understood. This study investigates how atmospheric convection affects the summer variability of δ18O in precipitation (δ18Op) and δD in water vapor (δDv) at the daily scale. This is achieved using isotopic data from precipitation samples at Lhasa, isotopic measurements of water vapor retrieved from satellites (Tropospheric Emission Spectrometer (TES), GOSAT) and atmospheric general circulation modeling. We reveal that both δ18Op and δDv at Lhasa are well correlated with upstream convective activity, especially above northern India. First, during days of strong convection, northern India surface air contains large amounts of vapor with relatively low δDv. Second, when this low-δDv moisture is uplifted toward southern Tibet, this initial depletion in HDO is further amplified by Rayleigh distillation as the vapor moves over the Himalayan. The intraseasonal variability of the isotopologue composition of vapor and precipitation over the southern Tibetan Plateau results from these processes occurring during air mass transportation.

  10. EOP MIT General Circulation Model (MITgcm)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data contains a regional implementation of the Massachusetts Institute of Technology general circulation model (MITgcm) at a 1-km spatial resolution for the...

  11. Ocean General Circulation Models

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Jin-Ho; Ma, Po-Lun

    2012-09-30

    1. Definition of Subject The purpose of this text is to provide an introduction to aspects of oceanic general circulation models (OGCMs), an important component of Climate System or Earth System Model (ESM). The role of the ocean in ESMs is described in Chapter XX (EDITOR: PLEASE FIND THE COUPLED CLIMATE or EARTH SYSTEM MODELING CHAPTERS). The emerging need for understanding the Earth’s climate system and especially projecting its future evolution has encouraged scientists to explore the dynamical, physical, and biogeochemical processes in the ocean. Understanding the role of these processes in the climate system is an interesting and challenging scientific subject. For example, a research question how much extra heat or CO2 generated by anthropogenic activities can be stored in the deep ocean is not only scientifically interesting but also important in projecting future climate of the earth. Thus, OGCMs have been developed and applied to investigate the various oceanic processes and their role in the climate system.

  12. Simulating influence of QBO phase on planetary waves during a stratospheric warming in a general circulation model of the middle atmosphere

    Science.gov (United States)

    Koval, Andrey; Gavrilov, Nikolai; Pogoreltsev, Alexander; Savenkova, Elena

    2016-04-01

    One of the important factors of dynamical interactions between the lower and upper atmosphere is energy and momentum transfer by atmospheric internal gravity waves. For numerical modeling of the general circulation and thermal regime of the middle and upper atmosphere, it is important to take into account accelerations of the mean flow and heating rates produced by dissipating internal waves. The quasi-biennial oscillations (QBOs) of the zonal mean flow at lower latitudes at stratospheric heights can affect the propagation conditions of planetary waves. We perform numerical simulation of global atmospheric circulation for the initial conditions corresponding to the years with westerly and easterly QBO phases. We focus on the changes in amplitudes of stationary planetary waves (SPWs) and traveling normal atmospheric modes (NAMs) in the atmosphere during SSW events for the different QBO phases. For these experiments, we use the global circulation of the middle and upper atmosphere model (MUAM). There is theory of PW waveguide describing atmospheric regions where the background wind and temperature allow the wave propagation. There were introduced the refractive index for PWs and found that strongest planetary wave propagation is in areas of large positive values of this index. Another important PW characteristic is the Eliassen-Palm flux (EP-flux). These characteristics are considered as useful tools for visualizing the PW propagation conditions. Sudden stratospheric warming (SSW) event has significant influence on the formation of the weather anomalous and climate changes in the troposphere. Also, SSW event may affect the dynamical and energy processes in the upper atmosphere. The major SSW events imply significant temperature rises (up to 30 - 40 K) at altitudes 30 - 50 km accompanying with corresponding decreases, or reversals, of climatological eastward zonal winds in the stratosphere.

  13. Investigating Cenozoic climate change in tectonically active regions with a high-resolution atmospheric general circulation model (ECHAM5)

    Science.gov (United States)

    Mutz, Sebastian; Ehlers, Todd; Li, Jingmin; Werner, Martin; Stepanek, Christian; Lohmann, Gerrit

    2016-04-01

    Studies of Cenozoic palaeo-climates contribute to our understanding of contemporary climate change by providing insight into analogues such as the Pliocene (PLIO), and by evaluation of GCM (General Circulation Models) performance using the Mid-Holocene (MH) and the Last Glacial Maximum (LGM). Furthermore, climate is a factor to be considered in the evolution of ecology, landscapes and mountains, and in the reconstruction of erosion histories. In this study, we use high-resolution (T159) ECHAM5 simulations to investigate pre-industrial (PI) and the the above mentioned palaeo-climates for four tectonically active regions: Alaska (St. Elias Range), the US Northwest Pacific (Cascade Range), western South America (Andes) and parts of Asia (Himalaya-Tibet). The PI climate simulation is an AMIP (Atmospheric Model Intercomparison Project) style ECHAM5 experiment, whereas MH and LGM simulation are based on simulations conducted at the Alfred Wegner Institute, Bremerhaven. Sea surface boundary conditions for MH were taken from coupled atmosphere-ocean model simulations (Wei and Lohmann, 2012; Zhang et al, 2013) and sea surface temperatures and sea ice concentration for the LGM are based on GLAMAP project reconstructions (Schäfer-Neth and Paul, 2003). Boundary conditions for the PLIO simulation are taken from the PRISM (Pliocene Research, Interpretation and Synoptic Mapping) project and the employed PLIO vegetation boundary condition is created by means of the transfer procedure for the PRISM vegetation reconstruction to the JSBACH plant functional types as described by Stepanek and Lohmann (2012). For each of the investigated areas and time slices, the regional simulated climates are described by means of cluster analyses based on the variability of precipitation, 2m air temperature and the intra-annual amplitude of the values. Results indicate the largest differences to a PI climate are observed for LGM and PLIO climates in the form of widespread cooling and warming

  14. The impact of oceanic heat transport on the atmospheric circulation

    OpenAIRE

    M.-A. Knietzsch; V. Lucarini; F. Lunkeit

    2014-01-01

    A general circulation model of intermediate complexity with an idealized earthlike aquaplanet setup is used to study the impact of changes in the oceanic heat transport on the global atmospheric circulation. Focus is put on the Lorenz energy cycle and the atmospheric mean meridional circulation. The latter is analysed by means of the Kuo–Eliassen equation. The atmospheric heat transport compensates the imposed oceanic heat transport changes to a large extent in co...

  15. An Evaluation of the Large-Scale Implementation of Ocean Thermal Energy Conversion (OTEC Using an Ocean General Circulation Model with Low-Complexity Atmospheric Feedback Effects

    Directory of Open Access Journals (Sweden)

    Yanli Jia

    2018-01-01

    Full Text Available Previous investigations of the large-scale deployment of Ocean Thermal Energy Conversions (OTEC systems are extended by allowing some atmospheric feedback in an ocean general circulation model. A modified ocean-atmosphere thermal boundary condition is used where relaxation corresponds to atmospheric longwave radiation to space, and an additional term expresses horizontal atmospheric transport. This produces lower steady-state OTEC power maxima (8 to 10.2 TW instead of 14.1 TW for global OTEC scenarios, and 7.2 to 9.3 TW instead of 11.9 TW for OTEC implementation within 100 km of coastlines. When power production peaks, power intensity remains practically unchanged, at 0.2 TW per Sverdrup of OTEC deep cold seawater, suggesting a similar degradation of the OTEC thermal resource. Large-scale environmental effects include surface cooling in low latitudes and warming elsewhere, with a net heat intake within the water column. These changes develop rapidly from the propagation of Kelvin and Rossby waves, and ocean current advection. Two deep circulation cells are generated in the Atlantic and Indo-Pacific basins. The Atlantic Meridional Overturning Circulation (AMOC is reinforced while an AMOC-like feature appears in the North Pacific, with deep convective winter events at high latitudes. Transport between the Indo-Pacific and the Southern Ocean is strengthened, with impacts on the Atlantic via the Antarctic Circumpolar Current (ACC.

  16. Impacts of the cloud structure's latitudinal variation on the general circulation of the Venus atmosphere as modeled by the LMD-GCM

    Science.gov (United States)

    Garate-Lopez, Itziar; Lebonnois, Sébastien

    2017-04-01

    A new simulation of Venus atmospheric circulation obtained with the LMD Venus GCM is described and the impact of cloud's latitudinal structure on the general circulation is analyzed. The model used here is based on that presented in Lebonnois et al. (2016). However, in the present simulation we consider the latitudinal variation of the cloud structure (Haus et al., 2014) both for the solar heating and to compute the infrared net-exchange rate matrix used in the radiative transfer module. The new cloud treatment affects mainly the balance in the angular momentum and the zonal wind distribution. Consequently, the agreement between the vertical profile of the modeled mean zonal wind and the profiles measured by different probes, is clearly improved from previous simulations in which zonal winds below the clouds were weak (roughly half the observed values). Moreover, the equatorial jet obtained at the base of the cloud deck is now more consistent with the observations. In Lebonnois et al. (2016) it was too strong compared to mid-latitudes, but in the present simulation the equatorial jet is less intense than the mid-latitude jets, in concordance with cloud-tracking measurements (Hueso et al., 2015). Since the atmospheric waves play a crucial role in the angular momentum budget of the Venus's atmospheric circulation, we analyze the wave activity by means of the Fast Fourier Transform technique studying the frequency spectrum of temperature, zonal and meridional wind fields. Modifications in the activity of the different types of waves present in the Venusian atmosphere compared to Lebonnois et al. (2016) are discussed, in terms of horizontal and vertical transport of the angular momentum by diurnal and semi-diurnal tides, barotropic and baroclinic waves, and Rossby and Kelvin type waves. Haus R., Kappel D. and Arnold G., 2014. Atmospheric thermal structure and cloud features in the southern hemisphere of Venus as retrieved from VIRTIS/VEX radiation measurements. Icarus

  17. Global trend analysis of surface CO simulated using the global atmospheric chemistry general circulation model, EMAC (ECHAM5/MESSy)

    Science.gov (United States)

    Yoon, Jongmin; Pozzer, Andrea; Lelieveld, Jos

    2013-04-01

    Carbon monoxide (CO) is an important trace gas in tropospheric chemistry. It directly influences the concentration of tropospheric hydroxyl radical (OH), and therefore regulates the lifetimes of various tropospheric trace gases. Since anthropogenic activity produces about 60% of the annual global emission of the tropospheric CO, temporal trend analysis of surface CO is needed to understand the increasing (decreasing) influence of humans on the cleansing capacity of the atmosphere. In this study, the global trend of surface CO from 2001 to 2010 was estimated using the EMAC (ECHAM5/MESSy for Atmospheric Chemistry) model. The simulation is based on the emission scenario based on RCP8.5 (Representative Concentration Pathways). The global EMAC simulations of monthly surface CO are evaluated with monthly MOPITT (Measurements Of Pollution In The Troposphere) observations (i.e. MOP03TM), and the spatial correlations range from 0.87 to 0.97. The simulated trends are compared with the data from a global surface CO monitoring network, the World Data Centre for Greenhouse Gases (WDCGG), which includes also the NOAA/CMDL (Climate Monitoring and Diagnostic Laboratory of the National Oceanic and Atmospheric Administration) Cooperative Air Sampling Network. Over the United States and Western Europe, the significant decreases of surface CO are estimated at -49.7±2.7 and -38.6±2.7 ppbv per decade. In contrast, the surface CO increased by +12.4±10.2 and +7.2±3.7 ppbv per decade over South America and South Africa, respectively.

  18. Fractionation and current time trends of PCB congeners: evolvement of distributions 1950–2010 studied using a global atmosphere-ocean general circulation model

    Directory of Open Access Journals (Sweden)

    G. Lammel

    2012-08-01

    Full Text Available PCBs are ubiquitous environmental pollutants expected to decline in abiotic environmental media in response to decreasing primary emissions since the 1970s. A coupled atmosphere-ocean general circulation model with embedded dynamic sub-models for atmospheric aerosols and the marine biogeochemistry and air-surface exchange processes with soils, vegetation and the cryosphere is used to study the transport and fate of four PCB congeners covering a range of 3–7 chlorine atoms.

    The change of the geographic distribution of the PCB mixture reflects the sources and sinks' evolvement over time. Globally, secondary emissions (re-volatilisation from surfaces are on the long term increasingly gaining importance over primary emissions. Secondary emissions are most important for the congeners with 5–6 chlorine atoms. Correspondingly, the levels of these congeners are predicted to decrease slowest. Changes in congener mixture composition (fractionation are characterized both geographically and temporally. In high latitudes enrichment of the lighter, less persistent congeners and more delayed decreasing levels in response to decreasing emissions are found. The delivery of the contaminants to high latitudes is predicted to be more efficient than previously suggested. The results suggest furthermore that the effectiveness of emission control measures may significantly vary among substances. The trends of decline of organic contaminant levels in the abiotic environmental media do not only vary with latitude (slow in high latitudes, but do also show longitudinal gradients.

  19. Differential Radiative Heating Drives Tropical Atmospheric Circulation Weakening

    Science.gov (United States)

    Xia, Yan; Huang, Yi

    2017-10-01

    The tropical atmospheric circulation is projected to weaken during global warming, although the mechanisms that cause the weakening remain to be elucidated. We hypothesize that the weakening is related to the inhomogeneous distribution of the radiative forcing and feedback, which heats the tropical atmosphere in the ascending and subsiding regions differentially and thus requires the circulation to weaken due to energetic constraints. We test this hypothesis in a series of numerical experiments using a fully coupled general circulation model (GCM), in which the radiative forcing distribution is controlled using a novel method. The results affirm the effect of inhomogeneous forcing on the tropical circulation weakening, and this effect is greatly amplified by radiative feedback, especially that of clouds. In addition, we find that differential heating explains the intermodel differences in tropical circulation response to CO2 forcing in the GCM ensemble of the Climate Model Intercomparison Project.

  20. Climate impact of contrails: investigations by means of an atmospheric general circulation model; Klimawirkung von Kondensstreifen: Untersuchungen mit einem globalen atmosphaerischen Zirkulationsmodell

    Energy Technology Data Exchange (ETDEWEB)

    Marquart, S. [DLR Deutsches Zentrum fuer Luft- und Raumfahrt e.V., Oberpfaffenhofen (Germany). Inst. fuer Physik der Atmosphaere

    2003-07-01

    A parameterization of line-shaped contrails for use within the framework of a general circulation model (ECHAM) was developed for the first time. Contrail coverage, optical properties and radiative forcing are calculated at any model time step depending in a physically based manner on the respective conditions in the ambient air. In addition, possible effects on atmospheric parameters can be simulated, allowing for the determination of a climate sensitivity parameter especially for line-shaped contrails. Regional contrail cover as well as the large range of simulated optical depth values show a fair qualitative and quantitative agreement with observations. Sensitivity studies result in a lower global radiative forcing of line-shaped contrails than estimated by the Intergovernmental Panel on Climate Change (1999). Remaining uncertainties are mainly associated with poor knowledge of microphysical properties such as ice water content, particle shape and size. Considering future changes in air traffic density, and aircraft technology, as well as anthropogenic climate change, an increase of global contrail cover and radiative forcing by roughly a factor of four between 1992 and 2050 is simulated. (orig.)

  1. Climatology of the HOPE-G global ocean general circulation model - Sea ice general circulation model

    Energy Technology Data Exchange (ETDEWEB)

    Legutke, S. [Deutsches Klimarechenzentrum (DKRZ), Hamburg (Germany); Maier-Reimer, E. [Max-Planck-Institut fuer Meteorologie, Hamburg (Germany)

    1999-12-01

    The HOPE-G global ocean general circulation model (OGCM) climatology, obtained in a long-term forced integration is described. HOPE-G is a primitive-equation z-level ocean model which contains a dynamic-thermodynamic sea-ice model. It is formulated on a 2.8 grid with increased resolution in low latitudes in order to better resolve equatorial dynamics. The vertical resolution is 20 layers. The purpose of the integration was both to investigate the models ability to reproduce the observed general circulation of the world ocean and to obtain an initial state for coupled atmosphere - ocean - sea-ice climate simulations. The model was driven with daily mean data of a 15-year integration of the atmosphere general circulation model ECHAM4, the atmospheric component in later coupled runs. Thereby, a maximum of the flux variability that is expected to appear in coupled simulations is included already in the ocean spin-up experiment described here. The model was run for more than 2000 years until a quasi-steady state was achieved. It reproduces the major current systems and the main features of the so-called conveyor belt circulation. The observed distribution of water masses is reproduced reasonably well, although with a saline bias in the intermediate water masses and a warm bias in the deep and bottom water of the Atlantic and Indian Oceans. The model underestimates the meridional transport of heat in the Atlantic Ocean. The simulated heat transport in the other basins, though, is in good agreement with observations. (orig.)

  2. NAO-ocean circulation interactions in a coupled general circulation model

    Energy Technology Data Exchange (ETDEWEB)

    Bellucci, A. [Centro Euro-Mediterraneo per i Cambiamenti Climatici, Bologna (Italy); Gualdi, S.; Navarra, A. [Centro Euro-Mediterraneo per i Cambiamenti Climatici, Bologna (Italy); Istituto Nazionale di Geofisica e Vulcanologia, Bologna (Italy); Scoccimarro, E. [Istituto Nazionale di Geofisica e Vulcanologia, Bologna (Italy)

    2008-12-15

    The interplay between the North Atlantic Oscillation (NAO) and the large scale ocean circulation is inspected in a twentieth century simulation conducted with a state-of-the-art coupled general circulation model. Significant lead-lag covariance between oceanic and tropospheric variables suggests that the system supports a damped oscillatory mode involving an active ocean-atmosphere coupling, with a typical NAO-like space structure and a 5 years timescale, qualitatively consistent with a mid-latitude delayed oscillator paradigm. The two essential processes governing the oscillation are (1) a negative feedback between ocean gyre circulation and the high latitude SST meridional gradient and (2) a positive feedback between SST and the NAO. The atmospheric NAO pattern appears to have a weaker projection on the ocean meridional overturning, compared to the gyre circulation, which leads to a secondary role for the thermohaline circulation in driving the meridional heat transport, and thus the oscillatory mode. (orig.)

  3. PV Perspectives On The Titan Atmospheric Circulation

    Science.gov (United States)

    Allison, M.

    Potential vorticity (or PV) has become an important tool for the conceptual model- ing of atmospheric/oceanic circulations and promises to be an important element of the diagnostic study of Titan. Recent applications of PV thinking to numerical simu- lations and observations of several extraterrestrial atmospheres have encouraged the prospects for a unified understanding of planetary circulations encompassing a wide range of rotation and stratification parameters. The accumulated evidence suggests that zonal-mean winds and temperatures at the jet levels approximate a state of zero potential vorticity within the bounding low-latitudes of anticyclonic flow, with the ex- terior cyclonic regions conforming to a PV state that is well mixed with respect to its polar limit [e.g. Allison et al., 1994; Allison, 2000]. The forthcoming reconnais- sance of Titan's atmosphere by the Cassini-Huygens mission will likely represent the greatest leap in the science of planetary meteorology for the coming decade, and pro- vide a unique test of the application of PV thinking to a global cyclostrophic regime, possibly in combination with a geostrophic sub-layer. The visualization of potential vorticity maps of the eight scale-height depth of atmosphere between Titan's surface and its visually opaque haze layer may be facilitated with an appropriately modeified but informationally equivalent formulation of the Ertel PV which removes the expo- nential variation with altitude of its inverse density factor [cf. Lait, 1994]. Specific examples of these kinds of maps and sections will be presented, as constrained by available observations, with a view to their eventual definition by anticipated in situ vertical profiles and orbital global maps from Cassini-Huygens.

  4. Nucla circulating atmospheric fluidized bed demonstration project

    Energy Technology Data Exchange (ETDEWEB)

    Keith, Raymond E.

    1991-10-01

    Colorado-Ute Electric Association began a study to evaluate options for upgrading and extending the life of its Nucla power station in 1982. Located in southwestern Colorado near the town of Nucla, this station was commissioned in 1959 with a local bituminous coal as its design fuel for three identical stoker-fired units, each rated at 12.6 MW(e). Poor station efficiency, high fuel costs, and spiraling boiler maintenance costs forced the Nucla Station into low priority in the CUEA dispatch order as early as 1981. Among the options CUEA considered was to serve as a host utility to demonstrate Atmospheric Fluidized Bed Combustion (AFBC) technology. The anticipated environmental benefits and apparent attractive economics of a circulating AFBC led to Colorado-Ute's decision to proceed with the design and construction of a demonstration project in 1984 at the Nucla facility.

  5. The impact of oceanic heat transport on the atmospheric circulation

    Science.gov (United States)

    Lucarini, Valerio; Lunkeit, Frank

    2017-04-01

    A general circulation model of intermediate complexity with an idealized Earth-like aquaplanet setup is used to study the impact of changes in the oceanic heat transport on the global atmospheric circulation. Focus is on the atmospheric mean meridional circulation and global thermodynamic properties. The atmosphere counterbalances to a large extent the imposed changes in the oceanic heat transport, but, nonetheless, significant modifications to the atmospheric general circulation are found. Increasing the strength of the oceanic heat transport up to 2.5 PW leads to an increase in the global mean near-surface temperature and to a decrease in its equator-to-pole gradient. For stronger transports, the gradient is reduced further, but the global mean remains approximately constant. This is linked to a cooling and a reversal of the temperature gradient in the tropics. Additionally, a stronger oceanic heat transport leads to a decline in the intensity and a poleward shift of the maxima of both the Hadley and Ferrel cells. Changes in zonal mean diabatic heating and friction impact the properties of the Hadley cell, while the behavior of the Ferrel cell is mostly controlled by friction. The efficiency of the climate machine, the intensity of the Lorenz energy cycle and the material entropy production of the system decline with increased oceanic heat transport. This suggests that the climate system becomes less efficient and turns into a state of reduced entropy production as the enhanced oceanic transport performs a stronger large-scale mixing between geophysical fluids with different temperatures, thus reducing the available energy in the climate system and bringing it closer to a state of thermal equilibrium.

  6. Autoregressive logistic regression applied to atmospheric circulation patterns

    Science.gov (United States)

    Guanche, Y.; Mínguez, R.; Méndez, F. J.

    2014-01-01

    Autoregressive logistic regression models have been successfully applied in medical and pharmacology research fields, and in simple models to analyze weather types. The main purpose of this paper is to introduce a general framework to study atmospheric circulation patterns capable of dealing simultaneously with: seasonality, interannual variability, long-term trends, and autocorrelation of different orders. To show its effectiveness on modeling performance, daily atmospheric circulation patterns identified from observed sea level pressure fields over the Northeastern Atlantic, have been analyzed using this framework. Model predictions are compared with probabilities from the historical database, showing very good fitting diagnostics. In addition, the fitted model is used to simulate the evolution over time of atmospheric circulation patterns using Monte Carlo method. Simulation results are statistically consistent with respect to the historical sequence in terms of (1) probability of occurrence of the different weather types, (2) transition probabilities and (3) persistence. The proposed model constitutes an easy-to-use and powerful tool for a better understanding of the climate system.

  7. Effect of cloud cover and atmospheric circulation patterns on the observed surface solar radiation in Europe

    National Research Council Canada - National Science Library

    Chiacchio, Marc; Vitolo, Renato

    2012-01-01

    ...) in Europe including cloud cover and atmospheric circulation patterns. The role of observed cloud cover on DSW was analyzed through generalized linear models using DSW measurements obtained from the Global Energy Balance Archive during 1971–1996...

  8. Treatment of cloud radiative effects in general circulation models

    Energy Technology Data Exchange (ETDEWEB)

    Wang, W.C.; Dudek, M.P.; Liang, X.Z.; Ding, M. [State Univ. of New York, Albany, NY (United States)] [and others

    1996-04-01

    We participate in the Atmospheric Radiation Measurement (ARM) program with two objectives: (1) to improve the general circulation model (GCM) cloud/radiation treatment with a focus on cloud verticle overlapping and layer cloud optical properties, and (2) to study the effects of cloud/radiation-climate interaction on GCM climate simulations. This report summarizes the project progress since the Fourth ARM Science Team meeting February 28-March 4, 1994, in Charleston, South Carolina.

  9. Solar Tides in the Upper Equatorial Thermosphere: A Comparison between AE-E (Atmosphere Explorer-E Satellite) Data and the NCAR Thermospheric General Circulation Model.

    Science.gov (United States)

    1987-01-01

    serves to increase the resolution of the binning scheme without seriously lowering the number of data points collected in any particular bin. This...binning scheme has 7 rows of bins corresponding to different latitudes and 24 columns of bins corresponding to different local solar times making a total...National Center for Atmospheric Research for her excellent work in running the NCAR TGCM. 13 * ... . REFERENCES Broglio, L., C. Buongiorno, U. Ponzi

  10. Atmospheric circulation classification comparison based on wildfires in Portugal

    Science.gov (United States)

    Pereira, M. G.; Trigo, R. M.

    2009-04-01

    Atmospheric circulation classifications are not a simple description of atmospheric states but a tool to understand and interpret the atmospheric processes and to model the relation between atmospheric circulation and surface climate and other related variables (Radan Huth et al., 2008). Classifications were initially developed with weather forecasting purposes, however with the progress in computer processing capability, new and more robust objective methods were developed and applied to large datasets prompting atmospheric circulation classification methods to one of the most important fields in synoptic and statistical climatology. Classification studies have been extensively used in climate change studies (e.g. reconstructed past climates, recent observed changes and future climates), in bioclimatological research (e.g. relating human mortality to climatic factors) and in a wide variety of synoptic climatological applications (e.g. comparison between datasets, air pollution, snow avalanches, wine quality, fish captures and forest fires). Likewise, atmospheric circulation classifications are important for the study of the role of weather in wildfire occurrence in Portugal because the daily synoptic variability is the most important driver of local weather conditions (Pereira et al., 2005). In particular, the objective classification scheme developed by Trigo and DaCamara (2000) to classify the atmospheric circulation affecting Portugal have proved to be quite useful in discriminating the occurrence and development of wildfires as well as the distribution over Portugal of surface climatic variables with impact in wildfire activity such as maximum and minimum temperature and precipitation. This work aims to present: (i) an overview the existing circulation classification for the Iberian Peninsula, and (ii) the results of a comparison study between these atmospheric circulation classifications based on its relation with wildfires and relevant meteorological

  11. Recent summer Arctic atmospheric circulation anomalies in a historical perspective

    Science.gov (United States)

    Belleflamme, A.; Fettweis, X.; Erpicum, M.

    2015-01-01

    A significant increase in the summertime occurrence of a high pressure area over the Beaufort Sea, the Canadian Arctic Archipelago, and Greenland has been observed since the beginning of the 2000s, and particularly between 2007 and 2012. These circulation anomalies are likely partly responsible for the enhanced Greenland ice sheet melt as well as the Arctic sea ice loss observed since 2007. Therefore, it is interesting to analyse whether similar conditions might have happened since the late 19th century over the Arctic region. We have used an atmospheric circulation type classification based on daily mean sea level pressure and 500 hPa geopotential height data from five reanalysis data sets (ERA-Interim, ERA-40, NCEP/NCAR, ERA-20C, and 20CRv2) to put the recent circulation anomalies in perspective with the atmospheric circulation variability since 1871. We found that circulation conditions similar to 2007-2012 have occurred in the past, despite a higher uncertainty of the reconstructed circulation before 1940. For example, only ERA-20C shows circulation anomalies that could explain the 1920-1930 summertime Greenland warming, in contrast to 20CRv2. While the recent anomalies exceed by a factor of 2 the interannual variability of the atmospheric circulation of the Arctic region, their origin (natural variability or global warming) remains debatable.

  12. NUCLA Circulating Atmospheric Fluidized Bed Demonstration Project

    Energy Technology Data Exchange (ETDEWEB)

    1992-02-01

    The objective of this DOE Cooperative Agreement is to conduct a cost-shared clean coal technology project to demonstrate the feasibility of circulating fluidized bed combustion technology and to evaluate economic, environmental, and operational benefits of CFB steam generators on a utility scale. At the conclusion of the Phase 2 program, testing related to satisfying these objectives was completed. Data analysis and reporting are scheduled for completion by October 1991. (VC)

  13. Nucla circulating atmospheric fluidized bed demonstration project

    Energy Technology Data Exchange (ETDEWEB)

    1991-01-31

    During the fourth quarter of 1990, steady-state performance testing at the Nucla Circulating Fluidized Bed (CFB) resumed under sponsorship of the US Department of Energy. Co-sponsorship of the Demonstration Test Program by the Electric Power Research Institute (EPRI) was completed on June 15, 1990. From October through December, 1990, Colorado-Ute Electric Association (CUEA) completed a total of 23 steady-state performance tests, 4 dynamic tests, and set operating records during November and December as the result of improved unit operating reliability. Highlight events and achievements during this period of operation are presented.

  14. Dynamics and transport in the stratosphere : Simulations with a general circulation mode

    NARCIS (Netherlands)

    Aalst, M.K. (Maarten Krispijn) van

    2005-01-01

    The middle atmosphere is strongly affected by two of the world's most important environmental problems: global climate change and stratospheric ozone depletion, caused by anthropogenic emissions of greenhouse gases and chlorofluorocarbons (CFCs), respectively. General circulation models with

  15. The robustness of the atmospheric circulation and precipitation response to future anthropogenic surface warming

    Science.gov (United States)

    He, Jie; Soden, Brian J.; Kirtman, Ben

    2014-04-01

    The impact of long-term sea surface temperature (SST) change on the atmospheric circulation is studied by comparing atmospheric general circulation model (AGCM) simulations forced with a spatially uniform SST increase and a structured SST increase. The structured SST increase is calculated from the response of an ensemble of coupled ocean-atmosphere models to increased CO2. Most of the impact of SST pattern change is confined to equatorial Indo-Pacific. However, the circulation change under the two types of SST forcing is similar over the rest of the tropics and almost identical in the extratropics, indicating that the pattern of future SST change has overall little impact on the response of the atmospheric circulation and, in turn, on the resulting changes in precipitation. The tropical similarity is argued to result from energetic constraints that weaken the atmospheric circulation, whereas the extratropical similarity likely results from the insensitivity of Rossby Wave generation to the changes in near-equatorial upper level divergence. A comparison of the AGCM simulations with those from externally forced coupled ocean-atmosphere models suggest that ocean coupling or the direct effect of radiative forcing has a larger impact on the projected changes in circulation and precipitation than the pattern of SST change over most regions.

  16. Impact of the Projected Future Sea Ice Concentrations on the Atmospheric Circulation

    Science.gov (United States)

    Bader, J.; Seierstad, I.

    2007-12-01

    The observed decline of Arctic sea ice cover and the projected future reduction raise the question of how reduced Artic sea ice will influence/feed back on the climate. Using the projected future sea ice concentration by the coupled atmosphere ocean sea ice model ECHAM5/MPI, we investigate the impact of the changed sea ice cover on the atmospheric circulation by conducting atmospheric general circulation model (AGCM) experiments. We force the AGCM ECHAM5 by the current seasonal cycle of arctic sea ice and the projected future arctic seasonal cycle. The goal of this experiment is to determine the impact of the Artic sea ice reduction - that is projected in the next 100 years - on the atmospheric circulation. We find a significant reduction in storminess. The response to sea ice concentration changes differs strongly even on intraseasonal time scales.

  17. A study into the effects of gravity wave activity on the diurnal tide and airglow emissions in the equatorial mesosphere and lower thermosphere using the Coupled Middle Atmosphere and Thermosphere (CMAT) general circulation model

    Science.gov (United States)

    England, S. L.; Dobbin, A.; Harris, M. J.; Arnold, N. F.; Aylward, A. D.

    2006-02-01

    Momentum deposition by gravity wave breaking is known to affect the amplitude and phase of the diurnal tide. Modelling studies of this interaction have produced some conflicting results and as yet, the exact nature of this interaction is not fully understood. In this study, the effects of parameterised gravity wave momentum deposition on the diurnal tide and subsequently on green line airglow from atomic oxygen during equinox are investigated using the Coupled Middle Atmosphere and Thermosphere (CMAT) general circulation model. The effects of gravity wave drag calculated by two different parameterisations, Meyer [1999. Gravity wave interactions with the diurnal propagating tide. Journal of Geophysical Research 104, 4223 4239] and Medvedev and Klaassen [2000. Parameterisation of gravity wave momentum deposition based on non-linear wave interactions: basic formulation and sensitivity tests. Journal of Atmospheric and Terrestrial Physics 62, 1015 1033], are compared in the low latitude MLT region between 70 and 120 km, where the amplitude of the diurnal tide and green line volume emission rates maximise. Results indicate that momentum sources from both gravity wave parameterisations act to reduce the mid-latitude zonal jets and advance the phase of the diurnal tide, such that the peak amplitude at a given height occurs at an earlier time of day. Gravity wave momentum deposition as parameterised by Meyer [1999. Gravity wave interactions with the diurnal propagating tide. Journal of Geophysical Research 104, 4223 4239] results in a reduction of the amplitude of the diurnal tide in the MLT region, whereas the tidal amplitude is increased when the Medvedev and Klaassen [2000. Parameterisation of gravity wave momentum deposition based on non-linear wave interactions: basic formulation and sensitivity tests. Journal of Atmospheric and Terrestrial Physics 62, 1015 1033] parameterisation is used. Both parameterisations affect the local time variability of the simulated

  18. Impact of continental meteorology and atmospheric circulation in the ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Earth System Science; Volume 121; Issue 2. Impact of continental meteorology and atmospheric circulation in the modulation of Aerosol Optical Depth over the Arabian Sea. Sandhya K Nair S Sijikumar S S Prijith. Volume 121 Issue 2 April 2012 pp 263-272 ...

  19. ATMOSPHERIC CIRCULATION AND COMPOSITION OF GJ1214b

    Energy Technology Data Exchange (ETDEWEB)

    Menou, Kristen [Department of Astronomy, Columbia University, 550 West 120th Street, New York, NY 10027 (United States)

    2012-01-15

    The exoplanet GJ1214b presents an interesting example of compositional degeneracy for low-mass planets. Its atmosphere may be composed of water, super-solar or solar metallicity material. We present atmospheric circulation models of GJ1214b for these three compositions, with explicit gray radiative transfer and an optional treatment of MHD bottom drag. All models develop strong, superrotating zonal winds ({approx}1-2 km s{sup -1}). The degree of eastward heat advection, which can be inferred from secondary eclipse and thermal phase curve measurements, varies greatly between the models. These differences are understood as resulting from variations in the radiative times at the thermal photosphere, caused by separate molecular weight and opacity effects. Our GJ1214b models illustrate how atmospheric circulation can be used as a probe of composition for similar tidally locked exoplanets in the mini-Neptune/waterworld class.

  20. Decadal climate variability simulated in a coupled general circulation model

    Energy Technology Data Exchange (ETDEWEB)

    Walland, D.J. [Bureau of Meteorology, Melbourne, VIC (Australia). National Climate Centre; Power, S.B. [Bureau of Meteorology, Melbourne, VIC (Australia). Research Centre; Hirst, A.C. [Commonwealth Scientific Industrial Research Organisation Division of Atmospheric Research (Australia)

    2000-02-01

    A 1000 year integration of the CSIRO coupled ocean-atmosphere general circulation model is used to study low frequency (decadal to centennial) climate variability in precipitation and temperature. The model is shown to exhibit sizeable decadal variability for these fields, generally accounting for approximately 20 to 40% of the variability (greater than one year) in precipitation and up to 80% for temperature. An empirical orthogonal function (EOF) analysis is applied to the model output to show some of the major statistical modes of low frequency variability. The first EOF spatial pattern looks very much like that of the interannual ENSO pattern. It bears considerable resemblance to observational estimates and is centred in the Pacific extending into both hemispheres. It modulates both precipitation and temperature globally. The EOF has a time evolution that appears to be more than just red noise. Finally, the link between SST in the Pacific with Australian rainfall variability seen in observations is also evident in the model. (orig.)

  1. The epistemological status of general circulation models

    Science.gov (United States)

    Loehle, Craig

    2017-05-01

    Forecasts of both likely anthropogenic effects on climate and consequent effects on nature and society are based on large, complex software tools called general circulation models (GCMs). Forecasts generated by GCMs have been used extensively in policy decisions related to climate change. However, the relation between underlying physical theories and results produced by GCMs is unclear. In the case of GCMs, many discretizations and approximations are made, and simulating Earth system processes is far from simple and currently leads to some results with unknown energy balance implications. Statistical testing of GCM forecasts for degree of agreement with data would facilitate assessment of fitness for use. If model results need to be put on an anomaly basis due to model bias, then both visual and quantitative measures of model fit depend strongly on the reference period used for normalization, making testing problematic. Epistemology is here applied to problems of statistical inference during testing, the relationship between the underlying physics and the models, the epistemic meaning of ensemble statistics, problems of spatial and temporal scale, the existence or not of an unforced null for climate fluctuations, the meaning of existing uncertainty estimates, and other issues. Rigorous reasoning entails carefully quantifying levels of uncertainty.

  2. Clouds and the atmospheric circulation response to warming

    Science.gov (United States)

    Ceppi, Paulo; Hartmann, Dennis

    2016-04-01

    We study the effect of clouds on the atmospheric circulation response to CO2 quadrupling in an aquaplanet model with a slab-ocean lower boundary. The cloud effect is isolated by locking the clouds to either the control or 4xCO2 state in the shortwave (SW) or longwave (LW) radiation schemes. In our model, cloud-radiative changes explain more than half of the total poleward expansion of the Hadley cells, midlatitude jets, and storm tracks under CO2 quadrupling, even though they cause only one-fourth of the total global-mean surface warming. The effect of clouds on circulation results mainly from the SW cloud-radiative changes, which strongly enhance the Equator-to-pole temperature gradient at all levels in the troposphere, favoring stronger and poleward-shifted midlatitude eddies. By contrast, quadrupling CO2 while holding the clouds fixed causes strong polar amplification and weakened midlatitude baroclinicity at lower levels, yielding only a small poleward expansion of the circulation. Our results show that (a) the atmospheric circulation responds sensitively to cloud-driven changes in meridional and vertical temperature distribution, and (b) the spatial structure of cloud feedbacks likely plays a dominant role in the circulation response to greenhouse gas forcing. While the magnitude and spatial structure of the cloud feedback are expected to be highly model-dependent, an analysis of 4xCO2 simulations of CMIP5 models shows that the SW cloud feedback likely forces a poleward expansion of the tropospheric circulation in most climate models.

  3. Interactions Between the Thermohaline Circulation and Tropical Atlantic SST in a Coupled General Circulation Model

    Science.gov (United States)

    Miller, Ron; Jiang, Xing-Jian; Travis, Larry (Technical Monitor)

    2001-01-01

    Tropical Atlantic SST shows a (statistically well-defined) decadal time scale in a 104-year simulation of unforced variability by a coupled general circulation model (CGCM). The SST anomalies superficially resemble observed Tropical Atlantic variability (TAV), and are associated with changes in the atmospheric circulation. Brazilian rainfall is modulated with a decadal time scale, along with the strength of the Atlantic trade winds, which are associated with variations in evaporation and the net surface heat flux. However, in contrast to observed tropical Atlantic variability, the trade winds damp the associated anomalies in ocean temperature, indicating a negative feedback. Tropical SST anomalies in the CGCM, though opposed by the surface heat flux, are advected in from the Southern Hemisphere mid-latitudes. These variations modulate the strength of the thermohaline circulation (THC): warm, salty anomalies at the equator sink drawing cold, fresh mid-latitude water. Upon reaching the equator, the latter inhibit vertical overturning and advection from higher latitudes, which allows warm, salty anomalies to reform, returning the cycle to its original state. Thus, the cycle results from advection of density anomalies and the effect of these anomalies upon the rate of vertical overturning and surface advection. This decadal modulation of Tropical Atlantic SST and the thermohaline circulation is correlated with ocean heat transport to the Northern Hemisphere high latitudes and Norwegian Sea SST. Because of the central role of equatorial convection, we question whether this mechanism is present in the current climate, although we speculate that it may have operated in palaeo times, depending upon the stability of the tropical water column.

  4. ATMOSPHERIC CIRCULATION OF HOT JUPITERS: DAYSIDE–NIGHTSIDE TEMPERATURE DIFFERENCES

    Energy Technology Data Exchange (ETDEWEB)

    Komacek, Thaddeus D.; Showman, Adam P., E-mail: tkomacek@lpl.arizona.edu [Department of Planetary Sciences, University of Arizona, Tucson, AZ 85721 (United States)

    2016-04-10

    The full-phase infrared light curves of low-eccentricity hot Jupiters show a trend of increasing dayside-to-nightside brightness temperature difference with increasing equilibrium temperature. Here, we present a three-dimensional model that explains this relationship, in order to provide insight into the processes that control heat redistribution in tidally locked planetary atmospheres. This three-dimensional model combines predictive analytic theory for the atmospheric circulation and dayside–nightside temperature differences over a range of equilibrium temperatures, atmospheric compositions, and potential frictional drag strengths with numerical solutions of the circulation that verify this analytic theory. The theory shows that the longitudinal propagation of waves mediates dayside–nightside temperature differences in hot Jupiter atmospheres, analogous to the wave adjustment mechanism that regulates the thermal structure in Earth’s tropics. These waves can be damped in hot Jupiter atmospheres by either radiative cooling or potential frictional drag. This frictional drag would likely be caused by Lorentz forces in a partially ionized atmosphere threaded by a background magnetic field, and would increase in strength with increasing temperature. Additionally, the amplitude of radiative heating and cooling increases with increasing temperature, and hence both radiative heating/cooling and frictional drag damp waves more efficiently with increasing equilibrium temperature. Radiative heating and cooling play the largest role in controlling dayside–nightside temperature differences in both our analytic theory and numerical simulations, with frictional drag only being important if it is stronger than the Coriolis force. As a result, dayside–nightside temperature differences in hot Jupiter atmospheres increase with increasing stellar irradiation and decrease with increasing pressure.

  5. Atmospheric Circulation of Hot Jupiters: Dayside-Nightside Temperature Differences

    Science.gov (United States)

    Komacek, Thaddeus D.; Showman, Adam P.

    2016-04-01

    The full-phase infrared light curves of low-eccentricity hot Jupiters show a trend of increasing dayside-to-nightside brightness temperature difference with increasing equilibrium temperature. Here, we present a three-dimensional model that explains this relationship, in order to provide insight into the processes that control heat redistribution in tidally locked planetary atmospheres. This three-dimensional model combines predictive analytic theory for the atmospheric circulation and dayside-nightside temperature differences over a range of equilibrium temperatures, atmospheric compositions, and potential frictional drag strengths with numerical solutions of the circulation that verify this analytic theory. The theory shows that the longitudinal propagation of waves mediates dayside-nightside temperature differences in hot Jupiter atmospheres, analogous to the wave adjustment mechanism that regulates the thermal structure in Earth’s tropics. These waves can be damped in hot Jupiter atmospheres by either radiative cooling or potential frictional drag. This frictional drag would likely be caused by Lorentz forces in a partially ionized atmosphere threaded by a background magnetic field, and would increase in strength with increasing temperature. Additionally, the amplitude of radiative heating and cooling increases with increasing temperature, and hence both radiative heating/cooling and frictional drag damp waves more efficiently with increasing equilibrium temperature. Radiative heating and cooling play the largest role in controlling dayside-nightside temperature differences in both our analytic theory and numerical simulations, with frictional drag only being important if it is stronger than the Coriolis force. As a result, dayside-nightside temperature differences in hot Jupiter atmospheres increase with increasing stellar irradiation and decrease with increasing pressure.

  6. Synoptic atmospheric circulation patterns controlling avalanche activity in central Svalbard

    Science.gov (United States)

    Hancock, Holt; Prokop, Alexander; Eckerstorfer, Markus; Hendrikx, Jordy

    2017-04-01

    Central Svalbard's avalanche activity is primarily controlled by the local and synoptic scale meteorological conditions characterizing the region's winter storms. Previous work has described Svalbard's direct-action snow climate as High-Arctic maritime based on the unique meteorological conditions and resulting snowpack stratigraphy observed in the region. To gain a better understanding of the broad-scale spatial controls on regional avalanche activity in Svalbard, this work investigates synoptic atmospheric circulation patterns associated with observed avalanche cycles during the 2007/2008 to 2015/2016 winter seasons. We use avalanche observations systematically recorded as part of the Cryoslope Svalbard project from 2007-2010 in combination with additional observations from notable avalanche events from 2010-2016 to develop a regional avalanche cycle history. We then compare the timing of these avalanche cycles to an existing daily calendar of synoptic types and NCEP/NCAR Reanalysis datasets to characterize the synoptic atmospheric circulation patterns influencing this avalanche activity. Our results indicate regional avalanche cycles are driven by cyclonic activity in the seas surrounding Svalbard under synoptic circulation patterns associated with warm air advection and moisture transport from lower latitudes to Svalbard. The character and spatial distribution of observed avalanche activity can be differentiated by atmospheric circulation type: mid-winter slushflow and wet slab avalanche cycles, for example, are typically associated with meridional southerly flow over the North Atlantic bringing warm air and heavy precipitation to Svalbard. Such analyses can provide a foundation upon which to improve the understanding of central Svalbard's snow climate to facilitate regional avalanche forecasting efforts.

  7. Validation of Atmospheric Dynamics (VADY) - connections between planetary waves and atmospheric circulation types

    Science.gov (United States)

    Lang, Benjamin; Jacobeit, Jucundus; Beck, Christoph; Philipp, Andreas

    2015-04-01

    The climate research program "Medium-range Climate Predictions" (MiKlip), funded by the Federal Ministry of Education and Research in Germany (BMBF), has the aim to develop a climate model system (MPI-ESM) that can provide reliable decadal predictions of climate, including extreme weather events. A substantial part of the development process is a comprehensive model validation. Within MiKlip, it includes comparisons of model simulations and observations in order to allow statements about the performance of the model and to give particular recommendations for the further development of the model. The research project "Validation of Atmospheric Dynamics" (VADY), conducted by the cooperation partners "Institute of Geography at the University of Augsburg" (IGUA) and the "German Aerospace Centre" (DLR), contributes to model validation within MiKlip with a special focus on atmospheric waves and circulation dynamics. Within the framework of VADY, DLR validates the representation of atmospheric waves on different levels and scales based on suitable activity indices (e.g. the so-called large-scale dynamical activity index (LDAI), which is a measure for the activity of planetary waves). The focus of IGUA is on the model validation with respect to the representation of atmospheric circulation types, dynamical modes and the teleconnectivity of the atmospheric circulation. Currently, the connection between LDAI and atmospheric circulation types on different levels and for different seasons in the North Atlantic-European region is analysed by considering, in particular, the North Atlantic Oscillation. Results will be shown for the connection between LDAI and atmospheric circulation types and subsequently for the representation of the identified connections in the decadal-prediction model system of MPI-ESM.

  8. Analysis of snow feedbacks in 14 general circulation models

    Energy Technology Data Exchange (ETDEWEB)

    Randall, D.A.; Cess, R.D.; Blanchet, J.P.; Chalita, S.; Colman, R.; Dazlich, D.A.; Del Genio, A.D.; Keup, E.; Lacis, A.; Le Treut, H. [Colorado State Univ., Fort Collins, CO (United States)]|[State Univ. of New York, Stony Brook, NY (United States)]|[Canadian Climate Center, Ontario (Canada)]|[Lab. de Meteorologie Dynamique, Paris (France)]|[Bureau of Meteorology Research Center, Melbourne, Victoria (Australia)]|[NASA, Goddard Inst. for Space Studies, New York, NY (United States)]|[Univ. of Hamburg (Germany)

    1994-10-01

    Snow feedbacks produced by 14 atmospheric general circulation models have been analyzed through idealized numerical experiments. Included in the analysis is an investigation of the surface energy budgets of the models. Negative or weak positive snow feedbacks occurred in some of the models, while others produced strong positive snow feedbacks. These feedbacks are due not only to melting snow, but also to increases in boundary temperature, changes in air temperature, changes in water vapor, and changes in cloudiness. As a result, the net response of each model is quite complex. We analyze in detail the responses of one model with a strong positive snow feedback and another with a weak negative snow feedback. Some of the models include a temperature dependence of the snow albedo, and this has significantly affected the results.

  9. Modes of variability of Southern Hemisphere atmospheric circulation estimated by AGCMs

    Energy Technology Data Exchange (ETDEWEB)

    Grainger, Simon; Frederiksen, Carsten S. [Bureau of Meteorology, Centre for Australian Weather and Climate Research, Melbourne (Australia); Zheng, Xiaogu [National Institute of Water and Atmospheric Research, Wellington (New Zealand); Beijing Normal University, College of Global Change and Earth System, Beijing (China); Fereday, David; Folland, Chris K.; Knight, Jeff R. [Met Office Hadley Centre for Climate Change, Exeter (United Kingdom); Jin, Emilia K.; Kinter, James L. [George Mason University, Department of Atmospheric, Oceanic and Earth Sciences, Fairfax, VA (United States); Center for Ocean-Land-Atmosphere Studies, Calverton, MD (United States); Schubert, Siegfried [NASA Goddard Space Flight Center, Greenbelt, MD (United States); Syktus, Jozef [Queensland Climate Change Centre of Excellence, Brisbane (Australia)

    2011-02-15

    The seasonal mean variability of the atmospheric circulation is affected by processes with time scales from less than seasonal to interannual or longer. Using monthly mean data from an ensemble of Atmospheric General Circulation Model (AGCM) realisations, the interannual variability of the seasonal mean is separated into intraseasonal, and slowly varying components. For the first time, using a recently developed method, the slowly varying component in multiple AGCM ensembles is further separated into internal and externally forced components. This is done for Southern Hemisphere 500 hPa geopotential height from five AGCMs in the CLIVAR International Climate of the Twentieth Century project for the summer and winter seasons. In both seasons, the intraseasonal and slow modes of variability are qualitatively well reproduced by the models when compared with reanalysis data, with a relative metric finding little overall difference between the models. The Southern Annular Mode (SAM) is by far the dominant mode of slowly varying internal atmospheric variability. Two slow-external modes of variability are related to El Nino-Southern Oscillation (ENSO) variability, and a third is the atmospheric response to trends in external forcing. An ENSO-SAM relationship is found in the model slow modes of variability, similar to that found by earlier studies using reanalysis data. There is a greater spread in the representation of model slow-external modes in winter than summer, particularly in the atmospheric response to external forcing trends. This may be attributable to weaker external forcing constraints on SH atmospheric circulation in winter. (orig.)

  10. Role of atmospheric circulations in haze pollution in December 2016

    Science.gov (United States)

    Yin, Zhicong; Wang, Huijun

    2017-09-01

    In the east of China, recent haze pollution has been severe and damaging. In addition to anthropogenic emissions, atmospheric circulations and local meteorological conditions were conducive factors. The number of December haze days over North China and the Huanghuai area has increased sharply since 2010 and was greatest in 2016. During 2016, the most aggressive control measures for anthropogenic emissions were implemented from 16 to 21 December, but the most severe haze pollution still occurred, covering approximately 25 % of the land area of China and lasting for 6 days. The atmospheric circulations must play critical roles in the sub-seasonal haze events. Actually, the positive phase of the East Atlantic-West Russia pattern in the middle troposphere strengthened the anomalous anti-cyclone over the NH area that confined vertical motion below. The associated southerly anomalies made the cold air and surface wind speed weaker, but enhanced the humid flow. Thus, the horizontal and vertical dispersion of atmospheric particulates was suppressed and the pollutants gathered within a narrow space. In December 2016, these key indices were strongly beneficial for haze occurrence and combined to result in the severest haze pollution. The influences of the preceding autumn sea surface temperature near the Gulf of Alaska and the subtropical eastern Pacific, October-November snow cover in western Siberia, and associated physical processes on haze pollution are also discussed.

  11. Transient Atmospheric Circulation Response to An Instantaneous Doubling of Carbon Dioxide: Understanding Cause and Effect in Atmospheric Circulation Adjustment to Global Warming

    Science.gov (United States)

    Wu, Y.; Seager, R.; Ting, M.; Naik, N.; Shaw, T. A.

    2011-12-01

    As a consequence of increased carbon dioxide emission, the atmospheric general circulation is expected to change. IPCC AR4 coupled models have consistently projected a poleward shift in tropospheric zonal jets and midlatitude storm tracks. We explore the associated dynamical mechanisms by looking into the transient step-by-step adjustment of the circulation. This allows an assessment of the causality sequence in the circulation and thermal structure response prior to establishment of a quasi-equilibrium state. The transient atmospheric adjustment is examined using the National Center for Atmospheric Research Community Atmospheric Model Version 3 coupled to a slab ocean model and the CO2 concentration in the atmosphere is uniformly and instantaneously doubled. The thermal structure and circulation response is well established after one year of integration with the magnitudes gradually increasing afterwards towards quasi-equilibrium. Tropical upper tropospheric warming occurs in the first month. The expansion of the warming in the middle and upper troposphere to the subtropics occurs later and is found to be primarily dynamically-driven due to the intensification of transient eddy momentum flux convergence and resulting anomalous descending motion in this region. This linkage between the eddy-driven vertical motion anomaly and the subtropical warming expansion in the middle and upper troposphere is also confirmed in the late 21st century in the IPCC AR4 simulations. The poleward displacement of the midlatitude tropospheric jet streams occurs together with the change in eddy momentum flux convergence but only after the intensification of the subpolar westerlies in the stratosphere. The results demonstrate the importance of the tropospheric eddies in setting up the extratropical tropospheric response to global warming. Our modeling results also show the sequence of the zonal wind anomaly in the vertical column of the atmosphere during the period of transient adjustment

  12. Multiscale low-frequency circulation modes in the global atmosphere

    Science.gov (United States)

    Lau, K.-M.; Sheu, P.-J.; Kang, I.-S.

    1994-01-01

    In this paper, fundamental multiscale circulation modes in the global atmosphere are identified with the objective of providing better understanding of atmospheric low-frequency variabilities over a wide range of spatial and temporal scales. With the use of a combination of rotated principal component technique, singular spectrum analysis, and phase space portraits, three categories of basic multiscale modes in the atmosphere are found. The first is the interannual-mode (IAM), which is dominated by time scales longer than a year and can be attributed to heating and circulation anomalies associated with the coupled tropical ocean-atmosphere, in particular the El Nino-Southern Oscillation. The second is a set of tropical intraseasonal modes consisting of three separate multiscale patterns (ISO-1, -2, -3) related to tropical heating that can be identified with the different phases of the Madden-Julian Oscillation (MJO), including its teleconnection to the extratropics. The ISO spatial and temporal patterns suggest that the extratropical wave train in the North Pacific and North America is related to heating over the Maritime Continent and that the evolution of the MJO around the equator may require forcing from the extratropics spawning convection over the Indian Ocean. The third category represents extratropical intraseasonal oscillations arising from internal dynamics of the basic-state circulation. In the Northern Hemisphere, there are two distinct circulation modes with multiple frequencies in this category: the Pacific/North America (PNA) and the North Atlantic/Eurasia (NAE). In the Southern Hemisphere, two phase-locked modes (PSA-1 and PSA-2) are found depicting an eastward propagating wave train from eastern Australia, via the Pacific South America to the South Atlantic. The extratropical modes exhibit temporal characteristics such as phase locking and harmonic oscillations possibly associated with quadratically nonlinear dynamical systems. Additionally, the

  13. The Atmospheric Circulation of Hot Jupiters: a Hierarchical Modeling Approach

    Science.gov (United States)

    Komacek, Thaddeus D.; Showman, Adam P.

    2017-10-01

    The atmospheres of extrasolar gas giants that receive strong stellar irradiation, or “hot Jupiters,” are beginning to be characterized as a population. Photometric full-phase light curves of hot Jupiters allow for basic inferences of their atmospheric circulation, providing two key observables. First, they measure the amplitude of brightness variation, which has shown that the fractional brightness temperature difference between the dayside and nightside in the atmospheres of these tidally locked planets can approach unity. Additionally, each planet has a significant observed offset of the brightest point in their light curve, and offsets in the infrared ubiquitously occur before secondary eclipse. These infrared offsets are best explained by strong (~km/s) eastward winds in hot Jupiter atmospheres. Motivated by these observations, we have developed a first-principles analytic theory that predicts dayside-nightside temperature differences and horizontal and vertical wind speeds as a function of incident stellar flux, rotation rate, frictional drag strength, and atmospheric pressure level. To complement and compare with this theory, we have performed a hierarchy of three-dimensional numerical simulations of the atmospheric circulation to explore changes with incident stellar flux, rotation rate, and drag strength. Both the theory and numerical simulations predict that the dayside-nightside temperature differences of hot Jupiters and their wind speeds should increase with increasing incident stellar flux and decrease with increasing drag strength. So far, this has been hinted at in the observed sample of nine hot Jupiter phase curves, but we predict that these broad trends will be robust with a larger observed population. We extend our theory to estimate vertical mixing rates, which is critical for understanding the impact of clouds and disequilibrium chemistry on observations of hot Jupiters. To show the regimes that this theory applies in, we compare

  14. Sensitivity simulations of superparameterised convection in a general circulation model

    Science.gov (United States)

    Rybka, Harald; Tost, Holger

    2015-04-01

    Cloud Resolving Models (CRMs) covering a horizontal grid spacing from a few hundred meters up to a few kilometers have been used to explicitly resolve small-scale and mesoscale processes. Special attention has been paid to realistically represent cloud dynamics and cloud microphysics involving cloud droplets, ice crystals, graupel and aerosols. The entire variety of physical processes on the small-scale interacts with the larger-scale circulation and has to be parameterised on the coarse grid of a general circulation model (GCM). Since more than a decade an approach to connect these two types of models which act on different scales has been developed to resolve cloud processes and their interactions with the large-scale flow. The concept is to use an ensemble of CRM grid cells in a 2D or 3D configuration in each grid cell of the GCM to explicitly represent small-scale processes avoiding the use of convection and large-scale cloud parameterisations which are a major source for uncertainties regarding clouds. The idea is commonly known as superparameterisation or cloud-resolving convection parameterisation. This study presents different simulations of an adapted Earth System Model (ESM) connected to a CRM which acts as a superparameterisation. Simulations have been performed with the ECHAM/MESSy atmospheric chemistry (EMAC) model comparing conventional GCM runs (including convection and large-scale cloud parameterisations) with the improved superparameterised EMAC (SP-EMAC) modeling one year with prescribed sea surface temperatures and sea ice content. The sensitivity of atmospheric temperature, precipiation patterns, cloud amount and types is observed changing the embedded CRM represenation (orientation, width, no. of CRM cells, 2D vs. 3D). Additionally, we also evaluate the radiation balance with the new model configuration, and systematically analyse the impact of tunable parameters on the radiation budget and hydrological cycle. Furthermore, the subgrid

  15. Atmospheric circulation modeling of super Earths and terrestrial extrasolar planets using the SPARC/MITgcm

    Science.gov (United States)

    Kataria, T.; Showman, A. P.; Haberle, R. M.; Marley, M. S.; Fortney, J. J.; Freedman, R. S.

    2013-12-01

    The field of exoplanets continues to be a booming field of research in astronomy and planetary science, with numerous ground-based (e.g., SuperWASP, HARPS-N and S) and space-based surveys (e.g., Kepler) that detect and characterize planets ranging from hot Jupiters, Jovian-sized planets orbiting less than 0.1 AU from their star, to super Earths and terrestrial exoplanets, planets that have masses equal to or less than 10 times that of Earth with a range of orbital distances. Atmospheric circulation modeling plays an important role in the characterization of these planets, helping to constrain observations that probe their atmospheres. These models have proven successful in understanding observations of transiting exoplanets (when the planet passes in front of the star along our line of sight) particularly when the planet is passing through secondary eclipse (when the planet's dayside is visible). In modeling super Earths and terrestrial exoplanets, we must consider not only planets with thick fluid envelopes, but also traditional terrestrial planets with solid surfaces and thinner atmospheres. To that end, we present results from studies investigating the atmospheric circulation of these classes of planets using the SPARC/MITgcm, a state-of-the-art model which couples the MIT General Circulation Model with a plane-parallel, two-stream, non-gray radiative transfer model. We will present results from two studies, the first focusing on the circulation of GJ 1214b, a super-Earth detected by the MEarth ground-based survey, and a second study which explores the circulation of terrestrial exoplanets orbiting M-dwarfs.

  16. Nucla circulating atmospheric fluidized bed demonstration project. Final report

    Energy Technology Data Exchange (ETDEWEB)

    1991-10-01

    Colorado-Ute Electric Association began a study to evaluate options for upgrading and extending the life of its Nucla power station in 1982. Located in southwestern Colorado near the town of Nucla, this station was commissioned in 1959 with a local bituminous coal as its design fuel for three identical stoker-fired units, each rated at 12.6 MW(e). Poor station efficiency, high fuel costs, and spiraling boiler maintenance costs forced the Nucla Station into low priority in the CUEA dispatch order as early as 1981. Among the options CUEA considered was to serve as a host utility to demonstrate Atmospheric Fluidized Bed Combustion (AFBC) technology. The anticipated environmental benefits and apparent attractive economics of a circulating AFBC led to Colorado-Ute`s decision to proceed with the design and construction of a demonstration project in 1984 at the Nucla facility.

  17. Modeling of Antarctic Sea Ice in a General Circulation Model.

    Science.gov (United States)

    Wu, Xingren; Simmonds, Ian; Budd, W. F.

    1997-04-01

    A dynamic-thermodynamic sea ice model is developed and coupled with the Melbourne University general circulation model to simulate the seasonal cycle of the Antarctic sea ice distribution. The model is efficient, rapid to compute, and useful for a range of climate studies. The thermodynamic part of the sea ice model is similar to that developed by Parkinson and Washington, the dynamics contain a simplified ice rheology that resists compression. The thermodynamics is based on energy conservation at the top surface of the ice/snow, the ice/water interface, and the open water area to determine the ice formation, accretion, and ablation. A lead parameterization is introduced with an effective partitioning scheme for freezing between and under the ice floes. The dynamic calculation determines the motion of ice, which is forced with the atmospheric wind, taking account of ice resistance and rafting. The simulated sea ice distribution compares reasonably well with observations. The seasonal cycle of ice extent is well simulated in phase as well as in magnitude. Simulated sea ice thickness and concentration are also in good agreement with observations over most regions and serve to indicate the importance of advection and ocean drift in the determination of the sea ice distribution.

  18. Intraseasonal Variability in an Aquaplanet General Circulation Model

    Directory of Open Access Journals (Sweden)

    Adam H Sobel

    2010-04-01

    Full Text Available An aquaplanet atmospheric general circulation model simulation with a robust intraseasonal oscillation is analyzed. The SST boundary condition resembles the observed December-April average with continents omitted, although with the meridional SST gradient reduced to be one-quarter of that observed poleward of 10 ̊ latitude. Slow, regular eastward propagation at 5 m s21 in winds and precipitation with amplitude greater than that in the observed MJO is clearly identified in unfiltered fields. Local precipitation rate is a strongly non-linear and increasing function of column precipitable water, as in observations. The model intraseasonal oscillation resembles a moisture mode that is destabilized by wind-evaporation feedback, and that propagates eastward through advection of anomalous humidity by the sum of perturbation winds and mean westerly flow. A series of sensitivity experiments are conducted to test hypothesized mechanisms. A mechanism denial experiment in which intraseasonal latent heat flux variability is removed largely eliminates intraseasonal wind and precipitation variability. Reducing the lower-troposphere westerly flow in the warm pool by reducing the zonal SST gradient slows eastward propagation, supporting the importance of horizontal advection by the low-level wind to eastward propagation. A zonally symmetric SST basic state produces weak and unrealistic intraseasonal variability between 30 and 90 day timescales, indicating the importance of mean low-level westerly winds and hence a realistic phase relationship between precipitation and surface flux anomalies for producing realistic tropical intraseasonal variability.

  19. Orbital, tectonic and oceanographic controls on Pliocene climate and atmospheric circulation in Arctic Norway

    Science.gov (United States)

    Panitz, Sina; Salzmann, Ulrich; Risebrobakken, Bjørg; De Schepper, Stijn; Pound, Matthew J.; Haywood, Alan M.; Dolan, Aisling M.; Lunt, Daniel J.

    2018-02-01

    During the Pliocene Epoch, a stronger-than-present overturning circulation has been invoked to explain the enhanced warming in the Nordic Seas region in comparison to low to mid-latitude regions. While marine records are indicative of changes in the northward heat transport via the North Atlantic Current (NAC) during the Pliocene, the long-term terrestrial climate evolution and its driving mechanisms are poorly understood. We present the first two-million-year-long Pliocene pollen record for the Nordic Seas region from Ocean Drilling Program (ODP) Hole 642B, reflecting vegetation and climate in Arctic Norway, to assess the influence of oceanographic and atmospheric controls on Pliocene climate evolution. The vegetation record reveals a long-term cooling trend in northern Norway, which might be linked to a general decline in atmospheric CO2 concentrations over the studied interval, and climate oscillations primarily controlled by precession (23 kyr), obliquity (54 kyr) and eccentricity (100 kyr) forcing. In addition, the record identifies four major shifts in Pliocene vegetation and climate mainly controlled by changes in northward heat transport via the NAC. Cool temperate (warmer than present) conditions prevailed between 5.03-4.30 Ma, 3.90-3.47 Ma and 3.29-3.16 Ma and boreal (similar to present) conditions predominated between 4.30-3.90 Ma, 3.47-3.29 and after 3.16 Ma. A distinct decline in sediment and pollen accumulation rates at c. 4.65 Ma is probably linked to changes in ocean currents, marine productivity and atmospheric circulation. Climate model simulations suggest that changes in the strength of the Atlantic Meridional Overturning Circulation during the Early Pliocene could have affected atmospheric circulation in the Nordic Seas region, which would have affected the direction of pollen transport from Scandinavia to ODP Hole 642B.

  20. Examining the West African Monsoon circulation response to atmospheric heating in a GCM dynamical core

    Science.gov (United States)

    Chadwick, R.; Martin, G. M.; Copsey, D.; Bellon, G.; Caian, M.; Codron, F.; Rio, C.; Roehrig, R.

    2017-03-01

    Diabatic heating plays a crucial role in the formation and maintenance of the West African Monsoon. A dynamical core configuration of a General Circulation Model (GCM) is used to test the influence of diabatic heating from different sources and regions on the strength and northward penetration of the monsoon circulation. The dynamical core is able to capture the main features of the monsoon flow, and when forced with heating tendencies from various different GCMs it recreates many of the differences seen between the full GCM monsoon circulations. Differences in atmospheric short-wave absorption over the Sahara and Sahel regions are a key driver of variation in the models' monsoon circulations, and this is likely to be linked to how aerosols, clouds and surface albedo are represented across the models. The magnitude of short-wave absorption also appears to affect the strength and position of the African easterly jet (AEJ), but not that of the tropical easterly jet (TEJ). The dynamical core is also used here to understand circulation changes that occur during the ongoing model development process that occurs at each modeling centre, providing the potential to trace these changes to specific alterations in model physics.

  1. AIR HUMIDITY AND EVAPORATION CONDITIONS IN POLAND IN RELATION TO ATMOSPHERIC CIRCULATION PATTERNS

    Directory of Open Access Journals (Sweden)

    A. WYPYCH

    2013-03-01

    Full Text Available The issue describing the amount of water vapour in the atmosphere and its backgrounds seems to be very important because of water vapour role among meteorological processes which are taking place within the atmosphere. The principal aim of this study is to examine the atmospheric circulation conditionings of evaporation and air humidity differentiation in Poland. Research was based on data for the period 1981-2010. The temporal and spatial differentiation of evaporation and air humidity in relation to atmospheric circulation patterns were examined by analysis of evaporation, evapotranspiration as well as specific humidity and saturation deficit values. The circulation factor was determined by a local atmospheric circulation calendar by Niedzwiedz. The results showed that atmospheric circulation is an important factor for humidity and evaporation conditions with the most significant: water vapour content and air mass temperature. Both air humidity and evaporation report temporal and spatial differentiation modified by particular synoptic situations. It is proved mainly by the extremes.

  2. Influence of Atlantic SST anomalies on the atmospheric circulation in the Atlantic-European sector

    Directory of Open Access Journals (Sweden)

    E. Kestenare

    2003-06-01

    Full Text Available Recent studies of observational data suggest that Sea Surface Temperature (SST anomalies in the Atlantic Ocean have a significant influence on the atmospheric circulation in the Atlantic-European sector in early winter and in spring. After reviewing this work and showing that the spring signal is part of a global air-sea interaction, we analyze for comparison an ensemble of simulations with the ECHAM4 atmospheric general circulation model in T42 resolution forced by the observed distribution of SST and sea ice, and a simulation with the ECHAM4/OPA8 coupled model in T30 resolution. In the two cases, a significant influence of the Atlantic on the atmosphere is detected in the Atlantic-European sector. In the forced mode, ECHAM4 responds to SST anomalies from early spring to late summer, and also in early winter. The forcing involves SST anomalies not only in the tropical Atlantic, but also in the whole tropical band, suggesting a strong ENSO influence. The modeled signal resembles that seen in the observations in spring, but not in early winter. In the coupled mode, the Atlantic SST only has a significant influence on the atmosphere in summer. Although the SST anomaly is confined to the Atlantic, the summer signal shows some similarity with that seen in the forced simulations. However, there is no counterpart in the observations.

  3. Projections of thermal conditions for Poland for winters 2021?2050 in relation to atmospheric circulation

    OpenAIRE

    Piotr Piotrowski; Joanna Jędruszkiewicz

    2013-01-01

    Winter thermal conditions in Poland are largely determined by atmospheric circulation. Therefore, the projection of future temperature change should be considered in relation to changes in circulation patterns. This paper assesses the spatial variability in winter temperature in Poland in the 2021?2050 period based on the CLM, HIRHAM5 and RACMO2 models. Thermal conditions in winter have been studied in relation to the atmospheric circulation as a main factor of winter temperature change i...

  4. The influence of atmospheric circulation on plant phenological phases in central and eastern Europe

    Science.gov (United States)

    Aasa, Anto; Jaagus, Jaak; Ahas, Rein; Sepp, Mait

    2004-10-01

    The objective of this study is to analyse relationships between the start dates of spring phenological phases and large-scale atmospheric circulation patterns. The timing of phenological phases in temperate zones is driven by temperature, and temperature regime is generally determined by atmospheric circulation. The database analysed consists of the first dates of flowering of coltsfoot (Tussilago farfara L.), of birch (Betula pendula Roth.) leaf unfolding and of flowering of lilac (Syringa vulgaris L.); the North Atlantic oscillation (NAO) and the Arctic oscillation (AO) indices, frequencies of the circulation forms classified by Vangengeim and Girs, and of the groups of Grosswetterlagen presented by Hess and Brezowsky. The study area covers central and eastern Europe, and the period considered is 1951-98.The results show that the influence of the westerly airflow is more pronounced in the winter half-year, and weakens and even disappears as spring advances. Phases have the highest correlation with NAO and AO indices during winter (December-March) and the first three months of the year (January-March), which have correlations stronger than -0.5 in the Baltic Sea region. Among the phenological phases, flowering of coltsfoot is the most strongly correlated with the NAO and AO indices, followed by leafing of birch and flowering of lilac. Airflow from the north and from the east has a greater influence in springtime, particularly in the northernmost and southernmost regions of the study area.

  5. Atmospheric circulation influence on climatic trends in Europe: an analysis of circulation type classifications from the COST733 catalogue

    Czech Academy of Sciences Publication Activity Database

    Cahynová, Monika; Huth, R.

    2016-01-01

    Roč. 36, č. 7 (2016), s. 2743-2760 ISSN 0899-8418 R&D Projects: GA MŠk(CZ) ED1.1.00/02.0073 Institutional support: RVO:67179843 Keywords : atmospheric circulation * classification * circulation type * climatic trends * Europe * COST733 Subject RIV: EH - Ecology, Behaviour Impact factor: 3.760, year: 2016 http://onlinelibrary.wiley.com/doi/10.1002/joc.4003/abstract

  6. Atmospheric circulation influence on climatic trends in Europe: an analysis of circulation type classifications from the COST733 catalogue

    Czech Academy of Sciences Publication Activity Database

    Cahynová, Monika; Huth, Radan

    2016-01-01

    Roč. 36, č. 7 (2016), s. 2743-2760 ISSN 0899-8418 R&D Projects: GA ČR GAP209/10/2265; GA ČR(CZ) GPP209/12/P811 Institutional support: RVO:68378289 Keywords : atmospheric circulation * classification * circulation type * climatic trends * Europe * COST733 Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 3.760, year: 2016 http://onlinelibrary.wiley.com/doi/10.1002/joc.4003/abstract

  7. Atmospheric circulation in regional climate models over Central Europe: links to surface air temperature and the influence of driving data

    Science.gov (United States)

    Plavcová, Eva; Kyselý, Jan

    2012-10-01

    The study examines simulation of atmospheric circulation, represented by circulation indices (flow direction, strength and vorticity), and links between circulation and daily surface air temperatures in regional climate models (RCMs) over Central Europe. We explore control simulations of five high-resolution RCMs from the ENSEMBLES project driven by re-analysis (ERA-40) and the same global climate model (ECHAM5 GCM) plus of one RCM (RCA) driven by different GCMs. The aims are to (1) identify errors in RCM-simulated distributions of circulation indices in individual seasons, (2) identify errors in simulated temperatures under particular circulation indices, and (3) compare performance of individual RCMs with respect to the driving data. Although most of the RCMs qualitatively reflect observed distributions of the airflow indices, each produces distributions significantly different from the observations. General biases include overestimation of the frequency of strong flow days and of strong cyclonic vorticity. Some circulation biases obviously propagate from the driving data. ECHAM5 and all simulations driven by ECHAM5 underestimate frequency of easterly flow, mainly in summer. Except for HIRHAM, however, all RCMs driven by ECHAM5 improve on the driving GCM in simulating atmospheric circulation. The influence on circulation characteristics in the nested RCM differs between GCMs, as demonstrated in a set of RCA simulations with different driving data. The driving data control on circulation in RCA is particularly weak for the BCM GCM, in which case RCA substantially modifies (but does not improve) the circulation from the driving data in both winter and summer. Those RCMs with the most distorted atmospheric circulation are HIRHAM driven by ECHAM5 and RCA driven by BCM. Relatively strong relationships between circulation indices and surface air temperatures were found in the observed data for Central Europe. The links differ by season and are usually stronger for

  8. A general circulation model (GCM) parameterization of Pinatubo aerosols

    Energy Technology Data Exchange (ETDEWEB)

    Lacis, A.A.; Carlson, B.E.; Mishchenko, M.I. [NASA Goddard Institute for Space Studies, New York, NY (United States)

    1996-04-01

    The June 1991 volcanic eruption of Mt. Pinatubo is the largest and best documented global climate forcing experiment in recorded history. The time development and geographical dispersion of the aerosol has been closely monitored and sampled. Based on preliminary estimates of the Pinatubo aerosol loading, general circulation model predictions of the impact on global climate have been made.

  9. Response of an ocean general circulation model to wind and ...

    Indian Academy of Sciences (India)

    The stretched-coordinate ocean general circulation model has been designed to study the observed variability due to wind and thermodynamic forcings. The model domain extends from 60°N to 60°S and cyclically continuous in the longitudinal direction. The horizontal resolution is 5° × 5° and 9 discrete vertical levels.

  10. Calibrating the ECCO ocean general circulation model using Green's functions

    Science.gov (United States)

    Menemenlis, D.; Fu, L. L.; Lee, T.; Fukumori, I.

    2002-01-01

    Green's functions provide a simple, yet effective, method to test and calibrate General-Circulation-Model(GCM) parameterizations, to study and quantify model and data errors, to correct model biases and trends, and to blend estimates from different solutions and data products.

  11. Application of Improved Radiation Modeling to General Circulation Models

    Energy Technology Data Exchange (ETDEWEB)

    Michael J Iacono

    2011-04-07

    This research has accomplished its primary objectives of developing accurate and efficient radiation codes, validating them with measurements and higher resolution models, and providing these advancements to the global modeling community to enhance the treatment of cloud and radiative processes in weather and climate prediction models. A critical component of this research has been the development of the longwave and shortwave broadband radiative transfer code for general circulation model (GCM) applications, RRTMG, which is based on the single-column reference code, RRTM, also developed at AER. RRTMG is a rigorously tested radiation model that retains a considerable level of accuracy relative to higher resolution models and measurements despite the performance enhancements that have made it possible to apply this radiation code successfully to global dynamical models. This model includes the radiative effects of all significant atmospheric gases, and it treats the absorption and scattering from liquid and ice clouds and aerosols. RRTMG also includes a statistical technique for representing small-scale cloud variability, such as cloud fraction and the vertical overlap of clouds, which has been shown to improve cloud radiative forcing in global models. This development approach has provided a direct link from observations to the enhanced radiative transfer provided by RRTMG for application to GCMs. Recent comparison of existing climate model radiation codes with high resolution models has documented the improved radiative forcing capability provided by RRTMG, especially at the surface, relative to other GCM radiation models. Due to its high accuracy, its connection to observations, and its computational efficiency, RRTMG has been implemented operationally in many national and international dynamical models to provide validated radiative transfer for improving weather forecasts and enhancing the prediction of global climate change.

  12. Hospitable archean climates simulated by a general circulation model.

    Science.gov (United States)

    Wolf, E T; Toon, O B

    2013-07-01

    Evidence from ancient sediments indicates that liquid water and primitive life were present during the Archean despite the faint young Sun. To date, studies of Archean climate typically utilize simplified one-dimensional models that ignore clouds and ice. Here, we use an atmospheric general circulation model coupled to a mixed-layer ocean model to simulate the climate circa 2.8 billion years ago when the Sun was 20% dimmer than it is today. Surface properties are assumed to be equal to those of the present day, while ocean heat transport varies as a function of sea ice extent. Present climate is duplicated with 0.06 bar of CO2 or alternatively with 0.02 bar of CO2 and 0.001 bar of CH4. Hot Archean climates, as implied by some isotopic reconstructions of ancient marine cherts, are unattainable even in our warmest simulation having 0.2 bar of CO2 and 0.001 bar of CH4. However, cooler climates with significant polar ice, but still dominated by open ocean, can be maintained with modest greenhouse gas amounts, posing no contradiction with CO2 constraints deduced from paleosols or with practical limitations on CH4 due to the formation of optically thick organic hazes. Our results indicate that a weak version of the faint young Sun paradox, requiring only that some portion of the planet's surface maintain liquid water, may be resolved with moderate greenhouse gas inventories. Thus, hospitable late Archean climates are easily obtained in our climate model.

  13. Interannual modes of variability of Southern Hemisphere atmospheric circulation in CMIP3 models

    Energy Technology Data Exchange (ETDEWEB)

    Grainger, S; Frederiksen, C S [Centre for Australian Weather and Climate Research, Bureau of Meteorology, Melbourne (Australia); Zheng, X, E-mail: S.Grainger@bom.gov.a [College of Global Change and Earth System Science, Beijing Normal University, Beijing (China)

    2010-08-15

    The atmospheric circulation acts as a bridge between large-scale sources of climate variability, and climate variability on regional scales. Here a statistical method is applied to monthly mean Southern Hemisphere 500hPa geopotential height to separate the interannual variability of the seasonal mean into intraseasonal and slowly varying (time scales of a season or longer) components. Intraseasonal and slow modes of variability are estimated from realisations of models from the Coupled Model Intercomparison Project Phase 3 (CMIP3) twentieth century coupled climate simulation (20c3m) and are evaluated against those estimated from reanalysis data. The intraseasonal modes of variability are generally well reproduced across all CMIP3 20c3m models for both Southern Hemisphere summer and winter. The slow modes are in general less well reproduced than the intraseasonal modes, and there are larger differences between realisations than for the intraseasonal modes. New diagnostics are proposed to evaluate model variability. It is found that differences between realisations from each model are generally less than inter-model differences. Differences between model-mean diagnostics are found. The results obtained are applicable to assessing the reliability of changes in atmospheric circulation variability in CMIP3 models and for their suitability for further studies of regional climate variability.

  14. Observed variations in U.S. frost timing linked to atmospheric circulation patterns

    Science.gov (United States)

    Strong, Courtenay; McCabe, Gregory J.

    2017-01-01

    Several studies document lengthening of the frost-free season within the conterminous United States (U.S.) over the past century, and report trends in spring and fall frost timing that could stem from hemispheric warming. In the absence of warming, theory and case studies link anomalous frost timing to atmospheric circulation anomalies. However, recent efforts to relate a century of observed changes in U.S. frost timing to various atmospheric circulations yielded only modest correlations, leaving the relative importance of circulation and warming unclear. Here, we objectively partition the U.S. into four regions and uncover atmospheric circulations that account for 25–48% of spring and fall-frost timing. These circulations appear responsive to historical warming, and they consistently account for more frost timing variability than hemispheric or regional temperature indices. Reliable projections of future variations in growing season length depend on the fidelity of these circulation patterns in global climate models.

  15. Observed variations in U.S. frost timing linked to atmospheric circulation patterns

    Science.gov (United States)

    Strong, Courtenay; McCabe, Gregory J.

    2017-05-01

    Several studies document lengthening of the frost-free season within the conterminous United States (U.S.) over the past century, and report trends in spring and fall frost timing that could stem from hemispheric warming. In the absence of warming, theory and case studies link anomalous frost timing to atmospheric circulation anomalies. However, recent efforts to relate a century of observed changes in U.S. frost timing to various atmospheric circulations yielded only modest correlations, leaving the relative importance of circulation and warming unclear. Here, we objectively partition the U.S. into four regions and uncover atmospheric circulations that account for 25-48% of spring and fall-frost timing. These circulations appear responsive to historical warming, and they consistently account for more frost timing variability than hemispheric or regional temperature indices. Reliable projections of future variations in growing season length depend on the fidelity of these circulation patterns in global climate models.

  16. Multidecadal Thermohaline Circulation Variability Driven by Atmospheric Surface Flux Forcing

    National Research Council Canada - National Science Library

    Delworth, Thomas L; Greatbatch, Richard J

    2000-01-01

      Previous analyses of an extended integration of the Geophysical Fluid Dynamics Laboratory coupled climate model have revealed pronounced multidecadal variations of the thermohaline circulation (THC...

  17. Atmospheric circulation remote response during two types of El Niño in changing climate

    Science.gov (United States)

    Zheleznova, Irina

    2017-04-01

    The ENSO is the general mode of interannual climate variability. Studies of the last decade revealed that there are two different types of El Niño (Central Pacific and Eastern Pacific), and the effect of these two phenomena on atmospheric circulation differs significantly [Ashok et al., 2007; Weng et al., 2009; Zheleznova and Gushchina, 2015; Zheleznova and Gushchina, 2016]. This study investigates the changes in characteristics of the remote response on two types of El Niño in the context of climate warming in the 21st century, using CMIP5 climate models data. The ability of CMIP5 coupled ocean-atmosphere general circulation models (CGCMs) to simulate two flavors of El Niño was estimated in preliminary researches [Matveeva and Gushchina, 2015; Zheleznova et al., 2015]. It was shown that only 14 of the 20 CGCMs realistically reproduce SST anomalies distinctive for two types of El Nino. Further research carried out among these models have shown that only three CGCMs are capable to reproduce features of the response of the global, regional and vertical atmospheric circulation on the two flavours of El Niño. These CGCMs are MIROC 5, GFDL-ESM2M and CESM1-CAM5. Changing remote response features under climate change (based on the RCP group of experiments) was assessed on the basis of the data of these CGCMs. It was noted a general weakening of the remote response intensity, reducing its duration, as well as explore its change depending on the "rigidity" of the experiment. The study was supported by the Russian foundation for basic research (project № 16-35-00394 mol_a). References: 1. Ashok K., Behera S. K., Rao S. A., Weng H., Yamagata, T. El Nino Modoki and its possible teleconnection. J. Geophys. Res. 2007, 112, C11007, doi:10.1029/2006JC003798. 2. Matveeva T., Gushchina D. The role of intraseasonal atmosphere variability in enso generation in future climate // European Geosciences Union General Assembly 2016. — Vol. 18 of Geophysical Research Abstracts.

  18. The Pechora River Runoff, Atmospheric Circulation and Solar Activity

    Science.gov (United States)

    Golovanov, O. F.

    This study presents an attempt to define and estimate the factors effecting and possi- bly, determining the spatial-temporal characteristics of the Pechora River hydrological regime. The time-series of hydrometeorological observations (runoff, precipitation, air temperature) carried out within the basin of the impact object U the Pechora River U are close to secular and include the year of the century maximum of the solar activ- ity (1957). The joint statistical analysis of these characteristics averaged both for a year and for the low water periods in spring (V-VII), summer-autumn (VIII-IX) and winter (X-IV) demonstrated the majority of integral curves to have minimums coin- ciding or slightly differing from the solar activity maximum in 1957. It is especially typical for the spring high water runoff along the entire length of the Pechora River. Only the curves of the air temperature in the summer-autumn low water period are in the opposite phase relative to all other elements. In the upper Pechora the inte- gral curves of winter and annual precipitation are synchronous to the runoff curves. The multiyear variability of the Pechora runoff corresponds to that of the atmospheric circulation in the northern hemisphere. This is clearly illustrated by the decrease of the Pechora runoff and increase of the climate continentality in its basin, that is ac- companied with predominating of the meridional circulation, anticyclone invasion and precipitation decrease while the solar activity grows. This process takes place at the background of the prevailing mass transport of E+C type, increase of number of the elementary synoptic processes (ESP). The maximum number of ESP (observed in 1963) was recorded soon after the century maximum of the solar activity. This fact may be explained by the anticyclone circulation prevalence which results in growth of the climate continentality in the Pechora basin in this period. The enumerated in- flection points of the integral curves of

  19. Dust sources and atmospheric circulation in concert controlling Saharan dust emission and transport towards the Western Mediterranean Basin

    Science.gov (United States)

    Schepanski, Kerstin; Mallet, Marc; Heinold, Bernd; Ulrich, Max

    2017-04-01

    Dust transported from north African source regions towards Europe is a ubiquitous phenomenon in the Mediterranean region, a geographic region that is in part densely populated. Besides its impacts on the atmospheric radiation budget, dust suspended in the atmosphere results in reduced air quality, which is generally sensed as a reduction in quality of life. Furthermore, the exposure to dust aerosols enhances the prevalence of respiratory diseases, which reduces the general human wellbeing, and ultimately results in an increased loss of working hours due to illness and hospitalization rates. Characteristics of the atmospheric dust life cycle that determine dust transport will be presented with focus on the ChArMEx special observation period in June and July 2013 using the atmosphere-dust model COSMO-MUSCAT (COSMO: Consortium for Small-scale MOdeling; MUSCAT: MUltiScale Chemistry Aerosol Transport Model). Modes of atmospheric circulation were identified from empirical orthogonal function (EOF) analysis of the geopotential height at 850 hPa for summer 2013 and compared to EOFs calculated from 1979-2015 ERA-Interim reanalysis. Generally, two different phases were identified. They are related to the eastward propagation of the subtropical ridge into the Mediterranean basin, the position of the Saharan heat low, and the predominant Iberian heat low. The relation of these centres of action illustrates a dipole pattern for enhanced (reduced) dust emission fluxes, stronger (weaker) meridional dust transport, and consequent increase (decrease) atmospheric dust concentrations and deposition fluxes. In concert, the results from this study aim at illustrating the relevance of knowing the dust source locations in concert with the atmospheric circulation. Ultimately, this study addresses the question of what is finally transported towards the Mediterranean basin and Europe from which source regions - and fostered by which atmospheric circulation pattern. Outcomes from this study

  20. Climate feedbacks in a general circulation model incorporating prognostic clouds

    Energy Technology Data Exchange (ETDEWEB)

    Colman, R.; Fraser, J. [Bureau of Meteorology Research Centre, Melbourne, Vic. (Australia); Rotstayn, L. [CSIRO Atmospheric Research, Aspendale (Australia)

    2001-11-01

    This study performs a comprehensive feedback analysis on the Bureau of Meteorology Research Centre General Circulation Model, quantifying all important feedbacks operating under an increase in atmospheric CO{sub 2}. The individual feedbacks are analysed in detail, using an offline radiation perturbation method, looking at long- and shortwave components, latitudinal distributions, cloud impacts, non-linearities under 2xCO{sub 2} and 4xCO{sub 2} warmings and at interannual variability. The water vapour feedback is divided into terms due to moisture height and amount changes. The net cloud feedback is separated into terms due to cloud amount, height, water content, water phase, physical thickness and convective cloud fraction. Globally the most important feedbacks were found to be (from strongest positive to strongest negative) those due to water vapour, clouds, surface albedo, lapse rate and surface temperature. For the longwave (LW) response the most important term of the cloud 'optical property' feedbacks is due to the water content. In the shortwave (SW), both water content and water phase changes are important. Cloud amount and height terms are also important for both LW and SW. Feedbacks due to physical cloud thickness and convective cloud fraction are found to be relatively small. All cloud component feedbacks (other than height) produce conflicting LW/SW feedbacks in the model. Furthermore, the optical property and cloud fraction feedbacks are also of opposite sign. The result is that the net cloud feedback is the (relatively small) product of conflicting physical processes. Non-linearities in the feedbacks are found to be relatively small for all but the surface albedo response and some cloud component contributions. The cloud impact on non-cloud feedbacks is also discussed: greatest impact is on the surface albedo, but impact on water vapour feedback is also significant. The analysis method here proves to be a powerful tool for detailing the

  1. The influence of land warming on precipitation and atmospheric circulation change

    Science.gov (United States)

    Chadwick, Robin; Ackerley, Duncan; Dommenget, Dietmar

    2017-04-01

    One robust aspect of climate change is that the land surface warms more than the ocean surface, and this is expected to influence precipitation and the atmospheric circulation. A new set of experiments are described, where the effect of land surface temperature change on precipitation and circulation change is isolated, and compared with the effects of sea-surface temperature (SST) change, direct CO2 radiative forcing, and the plant physiological effect. Land warming generally leads to enhanced low-level convergence and precipitation over land, while SST warming leads to reduced precipitation over land and increases over the oceans. However the combination of the two effects is strongly nonlinear. Direct radiative forcing drives precipitation change both through heating of the atmosphere, and through land warming, and this is particularly important in some monsoon regions. The plant physiological effect directly drives large reductions in transpiration and precipitation over tropical forest regions, as stomata close in response to elevated CO2 concentrations. However the plant effect also produces significant land warming, which leads to increased convergence and precipitation in some tropical forest regions. Therefore the overall result of the plant effect in each region depends on the balance between these two mechanisms.

  2. Seasonal predictability of Kiremt rainfall in coupled general circulation models

    Science.gov (United States)

    Gleixner, Stephanie; Keenlyside, Noel S.; Demissie, Teferi D.; Counillon, François; Wang, Yiguo; Viste, Ellen

    2017-11-01

    The Ethiopian economy and population is strongly dependent on rainfall. Operational seasonal predictions for the main rainy season (Kiremt, June–September) are based on statistical approaches with Pacific sea surface temperatures (SST) as the main predictor. Here we analyse dynamical predictions from 11 coupled general circulation models for the Kiremt seasons from 1985–2005 with the forecasts starting from the beginning of May. We find skillful predictions from three of the 11 models, but no model beats a simple linear prediction model based on the predicted Niño3.4 indices. The skill of the individual models for dynamically predicting Kiremt rainfall depends on the strength of the teleconnection between Kiremt rainfall and concurrent Pacific SST in the models. Models that do not simulate this teleconnection fail to capture the observed relationship between Kiremt rainfall and the large-scale Walker circulation.

  3. Synoptic and climatological analysis of atmospheric circulation impacts on particulate matter pollution in Shanghai, China

    Science.gov (United States)

    Liao, Z.; Fan, S.

    2016-12-01

    This study investigated the particulate matter characteristics within different circulation types (CTs) in the megacity of Shanghai during the period 2001-2015, and provided a quantitative evaluation of atmospheric circulation influences on PM10 pollution across a wide range of spatial and temporal scales, from local to region and daily to interannual. Ten CTs were identified over the Asian-Pacific region by objective Lamb Weather Type approach and each resulting CT was characterized with distinct local meteorology and air mass source. The PM10 loadings in the CTs associated with continental westerly flow were significant higher than that in the CTs linked to marine easterly air masses. Regional backgrounds that transported by the synoptic flows were more responsible for the distinct PM10 levels in different CTs. The locally-produced PM10 generally stabilized in range of 20-25 μg m-3, but enhanced to 41.2 μg m-3 in case of anticyclone type. There were distinct PM10 trends in different CTs (ranged from -3.74 to -0.28 μg m-3 yr-1), indicating the different background trends. Overall, the PM10 concentrations have decreased (-2.33 μg m-3 yr-1) in the studied period and the estimated locally-produced trend (-0.79 μg m-3 yr-1) accounted for 33.9% of overall downward trend. The occurrence frequency presented an increase (0.15 % yr-1) for anticyclone type, but a decrease (-0.10 % yr-1) for the type N associated with invasion of cold air. The 15-yr frequency change of atmospheric circulation induced an increase in PM­10 level (0.17 μg m-3) in Shanghai. On the contrary, controls on the pollutant emission had always positive effects and hence should be always encouraged.

  4. Contribution of changes in atmospheric circulation patterns to extreme temperature trends.

    Science.gov (United States)

    Horton, Daniel E; Johnson, Nathaniel C; Singh, Deepti; Swain, Daniel L; Rajaratnam, Bala; Diffenbaugh, Noah S

    2015-06-25

    Surface weather conditions are closely governed by the large-scale circulation of the Earth's atmosphere. Recent increases in the occurrence of some extreme weather phenomena have led to multiple mechanistic hypotheses linking changes in atmospheric circulation to increasing probability of extreme events. However, observed evidence of long-term change in atmospheric circulation remains inconclusive. Here we identify statistically significant trends in the occurrence of atmospheric circulation patterns, which partially explain observed trends in surface temperature extremes over seven mid-latitude regions of the Northern Hemisphere. Using self-organizing map cluster analysis, we detect robust circulation pattern trends in a subset of these regions during both the satellite observation era (1979-2013) and the recent period of rapid Arctic sea-ice decline (1990-2013). Particularly substantial influences include the contribution of increasing trends in anticyclonic circulations to summer and autumn hot extremes over portions of Eurasia and North America, and the contribution of increasing trends in northerly flow to winter cold extremes over central Asia. Our results indicate that although a substantial portion of the observed change in extreme temperature occurrence has resulted from regional- and global-scale thermodynamic changes, the risk of extreme temperatures over some regions has also been altered by recent changes in the frequency, persistence and maximum duration of regional circulation patterns.

  5. Multi-year predictability in a coupled general circulation model

    Energy Technology Data Exchange (ETDEWEB)

    Power, Scott; Colman, Rob [Bureau of Meteorology Research Centre, Melbourne, VIC (Australia)

    2006-02-01

    Multi-year to decadal variability in a 100-year integration of a BMRC coupled atmosphere-ocean general circulation model (CGCM) is examined. The fractional contribution made by the decadal component generally increases with depth and latitude away from surface waters in the equatorial Indo-Pacific Ocean. The relative importance of decadal variability is enhanced in off-equatorial ''wings'' in the subtropical eastern Pacific. The model and observations exhibit ''ENSO-like'' decadal patterns. Analytic results are derived, which show that the patterns can, in theory, occur in the absence of any predictability beyond ENSO time-scales. In practice, however, modification to this stochastic view is needed to account for robust differences between ENSO-like decadal patterns and their interannual counterparts. An analysis of variability in the CGCM, a wind-forced shallow water model, and a simple mixed layer model together with existing and new theoretical results are used to improve upon this stochastic paradigm and to provide a new theory for the origin of decadal ENSO-like patterns like the Interdecadal Pacific Oscillation and Pacific Decadal Oscillation. In this theory, ENSO-driven wind-stress variability forces internal equatorially-trapped Kelvin waves that propagate towards the eastern boundary. Kelvin waves can excite reflected internal westward propagating equatorially-trapped Rossby waves (RWs) and coastally-trapped waves (CTWs). CTWs have no impact on the off-equatorial sub-surface ocean outside the coastal wave guide, whereas the RWs do. If the frequency of the incident wave is too high, then only CTWs are excited. At lower frequencies, both CTWs and RWs can be excited. The lower the frequency, the greater the fraction of energy transmitted to RWs. This lowers the characteristic frequency of variability off the equator relative to its equatorial counterpart. Both the eastern boundary interactions and the accumulation of

  6. NUCLA Circulating Atmospheric Fluidized Bed Demonstration Project. 1990 Annual report

    Energy Technology Data Exchange (ETDEWEB)

    1992-02-01

    The objective of this DOE Cooperative Agreement is to conduct a cost-shared clean coal technology project to demonstrate the feasibility of circulating fluidized bed combustion technology and to evaluate economic, environmental, and operational benefits of CFB steam generators on a utility scale. At the conclusion of the Phase 2 program, testing related to satisfying these objectives was completed. Data analysis and reporting are scheduled for completion by October 1991. (VC)

  7. Atmospheric circulation in northern hemisphere and north atlantic oscillation

    Directory of Open Access Journals (Sweden)

    Александр Вадимович Холопцев

    2015-08-01

    Full Text Available Conditions under which statistical connections of interannual changes of repitition duration periods in Northern hemisphere of elementary circulation mechanisms associated to meridional northern and meridional southern groups with variations of North Atlantic oscillation are significant were revealed. It is shown, that the characteristics changes of these connections taking place in modern period can be caused by distribution changes of distribution of sea surface temperatures

  8. Impact of an improved shortwave radiation scheme in the MAECHAM5 General Circulation Model

    Directory of Open Access Journals (Sweden)

    J. J. Morcrette

    2007-05-01

    Full Text Available In order to improve the representation of ozone absorption in the stratosphere of the MAECHAM5 general circulation model, the spectral resolution of the shortwave radiation parameterization used in the model has been increased from 4 to 6 bands. Two 20-years simulations with the general circulation model have been performed, one with the standard and the other with the newly introduced parameterization respectively, to evaluate the temperature and dynamical changes arising from the two different representations of the shortwave radiative transfer. In the simulation with the increased spectral resolution in the radiation parameterization, a significant warming of almost the entire model domain is reported. At the summer stratopause the temperature increase is about 6 K and alleviates the cold bias present in the model when the standard radiation scheme is used. These general circulation model results are consistent both with previous validation of the radiation scheme and with the offline clear-sky comparison performed in the current work with a discrete ordinate 4 stream scattering line by line radiative transfer model. The offline validation shows a substantial reduction of the daily averaged shortwave heating rate bias (1–2 K/day cooling that occurs for the standard radiation parameterization in the upper stratosphere, present under a range of atmospheric conditions. Therefore, the 6 band shortwave radiation parameterization is considered to be better suited for the representation of the ozone absorption in the stratosphere than the 4 band parameterization. Concerning the dynamical response in the general circulation model, it is found that the reported warming at the summer stratopause induces stronger zonal mean zonal winds in the middle atmosphere. These stronger zonal mean zonal winds thereafter appear to produce a dynamical feedback that results in a dynamical warming (cooling of the polar winter (summer mesosphere, caused by an

  9. Active upper-atmosphere chemistry and dynamics from polar circulation reversal on Titan

    Science.gov (United States)

    Teanby, Nicholas A.; Irwin, Patrick G. J.; Nixon, Conor A.; de Kok, Remco; Vinatier, Sandrine; Coustenis, Athena; Sefton-Nash, Elliot; Calcutt, Simon B.; Flasar, F. Michael

    2012-11-01

    Saturn's moon Titan has a nitrogen atmosphere comparable to Earth's, with a surface pressure of 1.4 bar. Numerical models reproduce the tropospheric conditions very well but have trouble explaining the observed middle-atmosphere temperatures, composition and winds. The top of the middle-atmosphere circulation has been thought to lie at an altitude of 450 to 500 kilometres, where there is a layer of haze that appears to be separated from the main haze deck. This `detached' haze was previously explained as being due to the co-location of peak haze production and the limit of dynamical transport by the circulation's upper branch. Here we report a build-up of trace gases over the south pole approximately two years after observing the 2009 post-equinox circulation reversal, from which we conclude that middle-atmosphere circulation must extend to an altitude of at least 600 kilometres. The primary drivers of this circulation are summer-hemisphere heating of haze by absorption of solar radiation and winter-hemisphere cooling due to infrared emission by haze and trace gases; our results therefore imply that these effects are important well into the thermosphere (altitudes higher than 500 kilometres). This requires both active upper-atmosphere chemistry, consistent with the detection of high-complexity molecules and ions at altitudes greater than 950 kilometres, and an alternative explanation for the detached haze, such as a transition in haze particle growth from monomers to fractal structures.

  10. Active Upper-atmosphere Chemistry and Dynamics from Polar Circulation Reversal on Titan

    Science.gov (United States)

    Teanby, Nicholas A.; Irwin, Patrick Gerard Joseph; Nixon, Conor A.; DeKok, Remco; Vinatier, Sandrine; Coustenis, Athena; Sefton-Nash, Elliot; Calcutt, Simon B.; Flasar, Michael F.

    2012-01-01

    Saturn's moon Titan has a nitrogen atmosphere comparable to Earth's, with a surface pressure of 1.4 bar. Numerical models reproduce the tropospheric conditions very well but have trouble explaining the observed middle-atmosphere temperatures, composition and winds. The top of the middle-atmosphere circulation has been thought to lie at an altitude of 450 to 500 kilometres, where there is a layer of haze that appears to be separated from the main haze deck. This 'detached' haze was previously explained as being due to the colocation of peak haze production and the limit of dynamical transport by the circulation's upper branch. Herewe report a build-up of trace gases over the south pole approximately two years after observing the 2009 post-equinox circulation reversal, from which we conclude that middle-atmosphere circulation must extend to an altitude of at least 600 kilometres. The primary drivers of this circulation are summer-hemisphere heating of haze by absorption of solar radiation and winter-hemisphere cooling due to infrared emission by haze and trace gases; our results therefore imply that these effects are important well into the thermosphere (altitudes higher than 500 kilometres). This requires both active upper-atmosphere chemistry, consistent with the detection of high-complexity molecules and ions at altitudes greater than 950 kilometres, and an alternative explanation for the detached haze, such as a transition in haze particle growth from monomers to fractal structures.

  11. Regional atmospheric circulation shifts induced by a grand solar minimum

    NARCIS (Netherlands)

    Martin-Puertas, C.; Matthes, K.; Brauer, A.; Muscheler, R.; Hansen, F.; Petrick, C.; Aldahan, A.; Possnert, G.; van Geel, B.

    2012-01-01

    Large changes in solar ultraviolet radiation can indirectly affect climate1 by inducing atmospheric changes. Specifically, it has been suggested that centennial-scale climate variability during the Holocene epoch was controlled by the Sun2, 3. However, the amplitude of solar forcing is small when

  12. The Influence of Nitrogen Dioxide on Arrhythmias in Spain and Its Relationship with Atmospheric Circulation.

    Science.gov (United States)

    Santurtún, Ana; Sanchez-Lorenzo, Arturo; Villar, Alejandro; Riancho, José A; Zarrabeitia, María T

    2017-01-01

    Epidemiological studies suggest that increased ambient NO2 concentrations are associated with cardiovascular disease. However, none of them have examined the association between ambient air pollution and cardiac arrhythmias in the general population in Spain. This paper assesses the short-term association between the aforementioned air pollutant and hospital admissions for arrhythmia in nine different regions of Spain during a 6-year period (2005-2010), and the possible season-specific effects of the compound on this pathology, by performing a time-series analysis based on Poisson regression models. The results show statistically significant positive relationship increases between arrhythmia admissions and increments in NO2 concentration during the whole year, most notably in wintertime. Moreover, while trying to establish a threshold for NO2 concentration above which the incidence of arrhythmia episodes increases significantly, this study reveals that hospital admissions increased linearly in response to an increase in as we move to higher NO2 concentration levels. Finally, an analysis of NO2 concentrations and their relationship with atmospheric circulation is performed, showing higher values of NO2 under anticyclonic conditions during winter that could be used for implementing pollution level alert protocols depending on forecast circulation patterns.

  13. Atmospheric circulation patterns and phenological anomalies of grapevine in Italy

    Science.gov (United States)

    Cola, Gabriele; Alilla, Roberta; Dal Monte, Giovanni; Epifani, Chiara; Mariani, Luigi; Parisi, Simone Gabriele

    2014-05-01

    Grapevine (Vitis vinifera L.) is a fundamental crop for Italian agriculture as testified by the first place of Italy in the world producers ranking. This justify the importance of quantitative analyses referred to this crucial crop and aimed to quantify meteorological resources and limitations to development and production. Phenological rhythms of grapevine are strongly affected by surface fields of air temperature which in their turn are affected by synoptic circulation. This evidence highlights the importance of an approach based on dynamic climatology in order to detect and explain phenological anomalies that can have relevant effects on quantity and quality of grapevine production. In this context, this research is aimed to study the existing relation among the 850 hPa circulation patterns over the Euro-Mediterranean area from NOAA Ncep dataset and grapevine phenological fields for Italy over the period 2006-2013, highlighting the main phenological anomalies and analyzing synoptic determinants. This work is based on phenological fields with a standard pixel of 2 km routinely produced from 2006 by the Iphen project (Italian Phenological network) on the base of phenological observations spatialized by means of a specific algorithm based on cumulated thermal resources expressed as Normal Heat Hours (NHH). Anomalies have been evaluated with reference to phenological normal fields defined for the Italian area on the base of phenological observations and Iphen model. Results show that relevant phenological anomalies observed over the reference period are primarily associated with long lasting blocking systems driving cold air masses (Arctic or Polar-Continental) or hot ones (Sub-Tropical) towards the Italian area. Specific cases are presented for some years like 2007 and 2011.

  14. Impacts of four northern-hemisphere teleconnection patterns on atmospheric circulations over Eurasia and the Pacific

    Science.gov (United States)

    Gao, Tao; Yu, Jin-yi; Paek, Houk

    2017-08-01

    The impacts of four teleconnection patterns on atmospheric circulation components over Eurasia and the Pacific region, from low to high latitudes in the Northern Hemisphere (NH), were investigated comprehensively in this study. The patterns, as identified by the Climate Prediction Center (USA), were the East Atlantic (EA), East Atlantic/Western Russia (EAWR), Polar/Eurasia (POLEUR), and Scandinavian (SCAND) teleconnections. Results indicate that the EA pattern is closely related to the intensity of the subtropical high over different sectors of the NH in all seasons, especially boreal winter. The wave train associated with this pattern serves as an atmospheric bridge that transfers Atlantic influence into the low-latitude region of the Pacific. In addition, the amplitudes of the EAWR, SCAND, and POLEUR patterns were found to have considerable control on the "Vangengeim-Girs" circulation that forms over the Atlantic-Eurasian region in winter or spring. The EA and EAWR mainly affect the westerlies in winter and spring and the POLEUR and SCAND, respectively, in summer and winter. Strong westerlies confine the extension of the North Polar vortex, which generally results in a small weak vortex and a shallow East Asian trough located in a position further east than normal. Furthermore, the North Polar vortex presents significant connections with the patterns during winter and summer. Analyses in this work suggest that the teleconnection patterns in summer could be driven, at least partly, by the Atlantic Multidecadal Oscillation, which to some degree might transmit the influence of the Atlantic Ocean to Eurasia and the Pacific region.

  15. Water Isotope Tracers of Indo-Pacific Atmospheric Circulation: A Modern Take on Past Dynamics

    Science.gov (United States)

    Konecky, B. L.; Noone, D. C.; Nusbaumer, J. M.; Cobb, K. M.; Conroy, J. L.

    2015-12-01

    Stable oxygen and hydrogen isotope ratios (δ18O, δD) in precipitation, terrestrial water bodies, groundwater, and surface seawater are powerful integrators of the atmospheric water cycle. As such, proxy archives of δ18O and δD form the basis for much of our understanding of past changes in Indo-Pacific climate. Water isotope studies of the past millennium suggest that both internal variability and forced changes in global temperature drove decadal to centennial changes in monsoons, the Intertropical Convergence Zone, ENSO, and other modes of variability. However, recent observations as well as proxy data have shown that δ18O and δD signatures are far more complex than previously believed. Testing hypotheses about the drivers of past Indo-Pacific hydroclimate therefore requires an improved understanding of modern-day isotope ratios. In this study, we present new analyses of Indo-Pacific climate/isotope relationships from satellite and in situ observations, as well as new simulations with water isotope-enabled components of the Community Earth System Model. We evaluate the mechanisms that reinforce or weaken the tropical amount effect, which is often invoked in interpreting paleo-isotope data as hydroclimate proxies. We find that the amount effect is highly variable through space and time. Generally, it is strongest at sites with large-amplitude variations in the seasonal cycle. Circulation and moisture convergence play key roles in determining the strength of the amount effect, although cloud processes such as Rayleigh distillation and rain evaporation are still important, especially in determining initial isotope ratios of transported moisture. The relative influence of these mechanisms on vapor δ18O and δD varies in different parts of the tropics, affecting how regional archives record ENSO and other circulation patterns. We discuss these differences, and their implications for reconstructing Indo-Pacific atmospheric variability on decadal and longer

  16. A comparison of climate feedbacks in general circulation models

    Energy Technology Data Exchange (ETDEWEB)

    Colman, R. [Bureau of Meteorology Research Centre, GPO Box 1289K Melbourne 3001 (Australia)

    2003-05-01

    Heading Abstract. A comparison is performed for water vapour, cloud, albedo and lapse rate feedbacks taken from published results of 'offline' feedback calculations for general circulation models (GCMs) with mixed layer oceans performing 2 x CO{sub 2} and solar perturbation experiments. All feedbacks show substantial inter-model spread. The impact of uncertainties in feedbacks on climate sensitivity is discussed. A negative correlation is found between water vapour and lapse rate feedbacks, and also between longwave and shortwave components of the cloud feedback. The mean values of the feedbacks are compared with results derived from model intercomparisons which evaluated cloud forcing derived feedbacks under idealized climate forcing. Results are found to be comparable between the two approaches, after allowing for differences in experimental technique and diagnostic method. Recommendations are made for the future reporting of climate feedbacks. (orig.)

  17. Impact of sea ice cover changes on the Northern Hemisphere atmospheric winter circulation

    Directory of Open Access Journals (Sweden)

    D. Handorf

    2012-01-01

    Full Text Available The response of the Arctic atmosphere to low and high sea ice concentration phases based on European Center for Medium-Range Weather Forecast (ECMWF Re-Analysis Interim (ERA-Interim atmospheric data and Hadley Centre's sea ice dataset (HadISST1 from 1989 until 2010 has been studied. Time slices of winter atmospheric circulation with high (1990–2000 and low (2001–2010 sea ice concentration in the preceding August/September have been analysed with respect to tropospheric interactions between planetary and baroclinic waves. It is shown that a changed sea ice concentration over the Arctic Ocean impacts differently the development of synoptic and planetary atmospheric circulation systems. During the low ice phase, stronger heat release to the atmosphere over the Arctic Ocean reduces the atmospheric vertical static stability. This leads to an earlier onset of baroclinic instability that further modulates the non-linear interactions between baroclinic wave energy fluxes on time scales of 2.5–6 d and planetary scales of 10–90 d. Our analysis suggests that Arctic sea ice concentration changes exert a remote impact on the large-scale atmospheric circulation during winter, exhibiting a barotropic structure with similar patterns of pressure anomalies at the surface and in the mid-troposphere. These are connected to pronounced planetary wave train changes notably over the North Pacific.

  18. Weird planets and odd relations: Atmospheric Circulation on Hot Jupiters

    Science.gov (United States)

    Zhang, Michael; Knutson, Heather; Kataria, Tiffany; Burrows, Adam; Fortney, Jonathan

    2018-01-01

    We extract phase curves from Spitzer photometry for the highly irradiated hot Jupiter WASP-33b and the unusually dense Saturn-mass planet HD 149026b. To do so, we develop a new variant of Pixel Level Decorrelation that is effective at removing intrapixel sensitivity variations for long observations (> 10 hours) where the position of the star can vary by a significant fraction of a pixel. Using this algorithm, we derive eclipse depths, phase amplitudes, and phase offsets for both planets at 3.6 um and 4.5 um. We use a simple toy model to show that WASP-33b's phase offset, albedo, and heat recirculation efficiency are largely similar to those of other hot Jupiters despite its very high irradiation. On the other hand, our fits for HD 149026b prefer a very high albedo and an unusually high recirculation efficiency. We also compare our results to predictions from GCM models, and find that while neither provide a good match to the data, the discrepancies for HD 149026b are unusually large. We speculate that this may be related to its high bulk metallicity, which could lead to enhanced atmospheric opacities and the formation of reflective cloud layers in localized regions of the atmosphere. We then place these two planets in a broader context by exploring relationships between the temperatures, albedos, efficiencies, and phase offsets of all planets with published thermal phase curves. We find a striking relationship between phase offset and irradiation temperature--the former dips with temperature until around 3300 K, and rises thereafter. Although some aspects of this trend are mirrored in GCM models, there are notable differences that provide important clues for future modeling efforts.

  19. Numerical modeling of general circulation, thermohaline structure, and residence time in Gorgan Bay, Iran

    Science.gov (United States)

    Ranjbar, Mohammad Hassan; Hadjizadeh Zaker, Nasser

    2017-11-01

    Gorgan Bay is a semi-enclosed basin located in the southeast of the Caspian Sea, Iran. The bay is recognized as a resting place for migratory birds as well as a spawning habitat for native fish. However, apparently, no detailed research on its physical processes has previously been conducted. In this study, a 3D coupled hydrodynamic and solute transport model was used to investigate general circulation, thermohaline structure, and residence time in Gorgan Bay. Model outputs were validated against a set of field observations. Bottom friction and attenuation coefficient of light intensity were tuned in order to achieve optimum agreement with the observations. Results revealed that, due to the interaction between bathymetry and prevailing winds, a barotropic double-gyre circulation, dominating the general circulation, existed during all seasons in Gorgan Bay. Furthermore, temperature and salinity fluctuations in the bay were seasonal, due to the seasonal variability of atmospheric fluxes. Results also indicated that under the prevailing winds, the domain-averaged residence time in Gorgan Bay would be approximately 95 days. The rivers discharging into Gorgan Bay are considered as the main sources of nutrients in the bay. Since their mouths are located in the area with a residence time of over 100 days, Gorgan Bay could be at risk of eutrophication; it is necessary to adopt preventive measures against water quality degradation.

  20. Numerical modeling of general circulation, thermohaline structure, and residence time in Gorgan Bay, Iran

    Science.gov (United States)

    Ranjbar, Mohammad Hassan; Hadjizadeh Zaker, Nasser

    2018-01-01

    Gorgan Bay is a semi-enclosed basin located in the southeast of the Caspian Sea, Iran. The bay is recognized as a resting place for migratory birds as well as a spawning habitat for native fish. However, apparently, no detailed research on its physical processes has previously been conducted. In this study, a 3D coupled hydrodynamic and solute transport model was used to investigate general circulation, thermohaline structure, and residence time in Gorgan Bay. Model outputs were validated against a set of field observations. Bottom friction and attenuation coefficient of light intensity were tuned in order to achieve optimum agreement with the observations. Results revealed that, due to the interaction between bathymetry and prevailing winds, a barotropic double-gyre circulation, dominating the general circulation, existed during all seasons in Gorgan Bay. Furthermore, temperature and salinity fluctuations in the bay were seasonal, due to the seasonal variability of atmospheric fluxes. Results also indicated that under the prevailing winds, the domain-averaged residence time in Gorgan Bay would be approximately 95 days. The rivers discharging into Gorgan Bay are considered as the main sources of nutrients in the bay. Since their mouths are located in the area with a residence time of over 100 days, Gorgan Bay could be at risk of eutrophication; it is necessary to adopt preventive measures against water quality degradation.

  1. Classifications of Winter Euro-Atlantic Circulation Patterns: An Intercomparison of Five Atmospheric Reanalyses

    Czech Academy of Sciences Publication Activity Database

    Stryhal, J.; Huth, Radan

    2017-01-01

    Roč. 30, č. 19 (2017), s. 7847-7861 ISSN 0894-8755 Institutional support: RVO:68378289 Keywords : atmospheric circulation * classification * climate models * Europe * model evaluation/performance * reanalysis data Subject RIV: DG - Athmosphere Sciences, Meteorology OBOR OECD: Meteorology and atmospheric sciences Impact factor: 4.161, year: 2016 http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-17-0059.1

  2. Sensitivity of Atlantic meridional overturning circulation to the dynamical framework in an ocean general circulation model

    Science.gov (United States)

    Li, Xiaolan; Yu, Yongqiang; Liu, Hailong; Lin, Pengfei

    2017-06-01

    The horizontal coordinate systems commonly used in most global ocean models are the spherical latitude-longitude grid and displaced poles, such as a tripolar grid. The effect of the horizontal coordinate system on Atlantic meridional overturning circulation (AMOC) is evaluated by using an OGCM (ocean general circulation model). Two experiments are conducted with the model—one using a latitude-longitude grid (referred to as Lat_1) and the other using a tripolar grid (referred to as Tri). The results show that Tri simulates a stronger North Atlantic deep water (NADW) than Lat_1, as more saline water masses enter the Greenland-Iceland-Norwegian (GIN) seas in Tri. The stronger NADW can be attributed to two factors. One is the removal of the zonal filter in Tri, which leads to an increasing of the zonal gradient of temperature and salinity, thus strengthening the north geostrophic flow. In turn, it decreases the positive subsurface temperature and salinity biases in the subtropical regions. The other may be associated with topography at the North Pole, because realistic topography is applied in the tripolar grid while the latitude-longitude grid employs an artificial island around the North Pole. In order to evaluate the effect of the filter on AMOC, three enhanced filter experiments are carried out. Compared to Lat_1, an enhanced filter can also augment NADW formation, since more saline water is suppressed in the GIN seas, but accumulated in the Labrador Sea, especially in experiment Lat_2_S, which is the experiment with an enhanced filter on salinity.

  3. Orbit-spin coupling and the circulation of the Martian atmosphere

    Science.gov (United States)

    Shirley, James H.

    2017-07-01

    The physical origins of the observed interannual variability of weather and climate on Mars are poorly understood. In this paper we introduce a deterministic physical mechanism that may account for much of the variability of the circulation of the Mars atmosphere on seasonal and longer timescales. We focus on a possible coupling between the planetary orbital angular momentum and the angular momentum of the planetary rotation. We suspect that the planetary atmosphere may participate in an exchange of momentum between these two reservoirs. Nontrivial changes in the circulation of the atmosphere are likely to occur, as the atmospheric system gains and loses angular momentum, during this exchange. We derive a coupling expression linking orbital and rotational motions that produces an acceleration field varying with position and with time on and within a subject body. The spatially and temporally varying accelerations may interfere constructively or destructively with large-scale flows of geophysical fluids that are established and maintained by other means. This physical hypothesis predicts cycles of intensification and relaxation of circulatory flows of atmospheres on seasonal and longer timescales that are largely independent of solar forcing. The predictions of this hypothesis may be tested through numerical modeling. Examples from investigations of the atmospheric circulation of Mars are provided to illustrate qualitative features and quantitative aspects of the coupling mechanism proposed.

  4. Impact of 2007 and 2008 Arctic ice anomalies on the atmospheric circulation: Implications for long‐range predictions

    National Research Council Canada - National Science Library

    Balmaseda, Magdalena A; Ferranti, Laura; Molteni, Franco; Palmer, Tim N

    2010-01-01

    The impact on the atmospheric circulation of the unprecedented Arctic sea‐ice anomalies during the summers 2007 and 2008 is evaluated using the atmospheric model of the ECMWF operational seasonal forecasting system...

  5. The role of atmospheric circulation in the Mediterranean precipitation response to climate change.

    Science.gov (United States)

    Zappa, Giuseppe; Hoskins, Brian; Shepherd, Ted

    2017-04-01

    The Mediterranean region has been identified as a climate change hot-spot, due to a projected reduction in precipitation which could have large socio—economic impacts by affecting fresh water availability for agricultural and societal needs. However, the mechanisms that control such precipitation change are not well understood and there is large uncertainty in the amplitude of the projected precipitation change. We here show that more than 80% of the variance in the wintertime precipitation change in the CMIP5 models projections is linked to uncertainty in the atmospheric circulation response to climate change. This is demonstrated by introducing a simple index of atmospheric circulation based on the intensity of the westerly flow in North Africa. It is shown that the relationship between precipitation and circulation under climate change is consistent to what is found in the year to year variability. However, many CMIP5 climate models have biases in their ability of capturing the observed relationship between circulation and precipitation. This suggests that climate models may tend to underestimate the realised precipitation change for any given change in the atmospheric circulation.

  6. Resilience of the Asian atmospheric circulation shown by Paleogene dust provenance

    NARCIS (Netherlands)

    Licht, A.; Dupont-Nivet, G.; Pullen, A.; Kapp, P.; Abels, H.A.; Lai, Z.; Guo, Z.; Abell, J.; Giesler, D.

    2016-01-01

    The onset of modern central Asian atmospheric circulation is traditionally linked to the interplay of surface uplift of the Mongolian and Tibetan-Himalayan orogens, retreat of the Paratethys sea from central Asia and Cenozoic global cooling. Although the role of these players has not yet been

  7. Vertical heat flux in the ocean: Estimates from observations and from a coupled general circulation model

    Science.gov (United States)

    Cummins, Patrick F.; Masson, Diane; Saenko, Oleg A.

    2016-06-01

    The net heat uptake by the ocean in a changing climate involves small imbalances between the advective and diffusive processes that transport heat vertically. Generally, it is necessary to rely on global climate models to study these processes in detail. In the present study, it is shown that a key component of the vertical heat flux, namely that associated with the large-scale mean vertical circulation, can be diagnosed over extra-tropical regions from global observational data sets. This component is estimated based on the vertical velocity obtained from the geostrophic vorticity balance, combined with estimates of absolute geostrophic flow. Results are compared with the output of a non-eddy resolving, coupled atmosphere-ocean general circulation model. Reasonable agreement is found in the latitudinal distribution of the vertical heat flux, as well as in the area-integrated flux below about 250 m depth. The correspondence with the coupled model deteriorates sharply at depths shallower than 250 m due to the omission of equatorial regions from the calculation. The vertical heat flux due to the mean circulation is found to be dominated globally by the downward contribution from the Southern Hemisphere, in particular the Southern Ocean. This is driven by the Ekman vertical velocity which induces an upward transport of seawater that is cold relative to the horizontal average at a given depth. The results indicate that the dominant characteristics of the vertical transport of heat due to the mean circulation can be inferred from simple linear vorticity dynamics over much of the ocean.

  8. A hierarchical framework for coupling surface fluxes to atompsheric general circulation models: The homogeneity test

    Energy Technology Data Exchange (ETDEWEB)

    Miller, N.L.

    1993-01-01

    The atmosphere and the biosphere are inherently coupled to one another. Atmospheric surface state variables such as temperature, winds, water vapor, precipitation, and radiation control biophysical, biogeochemical, and ecological processes at the surface and subsurface. At the same time, surface fluxes of momentum, moisture, heat, and trace gases act as time-dependent boundary conditions providing feedback on atmospheric processes. To understand such phenomena, a coupled set of interactive models is required. Costs are still prohibitive for computing surface/subsurface fluxes directly for medium-resolution atmospheric general circulation models (AGCMs), but a technique has been developed for testing large-scale homogeneity and accessing surface parameterizations and models to reduce this computational cost and maintain accuracy. This modeling system potentially bridges the observed spatial and temporal ranges yet allows the incorporation of necessary details about individual ecological community types or biomes and simulates the net momentum, heat, moisture, and trace gas fluxes. This suite of coupled models is defined here as the hierarchical systems flux scheme (HSFS).

  9. A hierarchical framework for coupling surface fluxes to atompsheric general circulation models: The homogeneity test

    Energy Technology Data Exchange (ETDEWEB)

    Miller, N.L.

    1993-12-31

    The atmosphere and the biosphere are inherently coupled to one another. Atmospheric surface state variables such as temperature, winds, water vapor, precipitation, and radiation control biophysical, biogeochemical, and ecological processes at the surface and subsurface. At the same time, surface fluxes of momentum, moisture, heat, and trace gases act as time-dependent boundary conditions providing feedback on atmospheric processes. To understand such phenomena, a coupled set of interactive models is required. Costs are still prohibitive for computing surface/subsurface fluxes directly for medium-resolution atmospheric general circulation models (AGCMs), but a technique has been developed for testing large-scale homogeneity and accessing surface parameterizations and models to reduce this computational cost and maintain accuracy. This modeling system potentially bridges the observed spatial and temporal ranges yet allows the incorporation of necessary details about individual ecological community types or biomes and simulates the net momentum, heat, moisture, and trace gas fluxes. This suite of coupled models is defined here as the hierarchical systems flux scheme (HSFS).

  10. The Arctic atmospheric circulation modes and their impact on lower latitudes

    Science.gov (United States)

    Pasha Karami, Mehdi; Koenigk, Torben

    2017-04-01

    The role of the Arctic sea ice in the climate system and particularly in the future warmer climate deserves further investigations due to its complex coupling with the polar atmospheric circulation and the North Atlantic Ocean. While different regimes of the Arctic atmospheric circulation (e.g., Arctic oscillation, Arctic dipole anomaly) control the Arctic sea ice export into the North Atlantic Ocean, this in turn alters the sea ice extent and the Atlantic meridional overturning circulation, and can also generate changes in the atmospheric circulation during the following seasons. Such modes of Arctic atmosphere played a role in those events of Great Salinity Anomaly and recent record lows of Arctic summer sea ice extent, and led to extreme weather in lower latitudes. Understanding the interannaul to interdecadal variability of the Arctic is therefore crucial to better predict the climate on the seasonal to interannual scale in the highly populated regions of midlatitudes. Here we study the first three dominant modes of the Arctic atmosphere by applying EOF analysis to the monthly mean sea level pressure data (north of 70 °N) from ERA-20C reanalysis and CMIP5 models for the period of 1900-2010. We investigate the atmospheric teleconnections, changes in the Arctic sea ice and the North Atlantic Ocean, and extreme events that are associated with these modes. Furthermore, those regions of the Arctic that are more responsive to each of these modes are identified to better understand the dynamics controlling the sea ice. Our results also have implications for the impact of sea ice on lower latitudes.

  11. The influence of atmospheric circulation on the formation of snow cover on the north eastern Siberia

    Directory of Open Access Journals (Sweden)

    N. K. Kononova

    2012-01-01

    Full Text Available Based on daily data of the five meteorological stations located in different parts of northeastern Siberia (Anadyr, Chokurdakh, Wrangell Island, Verkhoyansk, Markovo the change of dates of formation, occurrence and maximum snow depth from year to year for the entire period of observation to 2008 is analyzed. The results are compared with long-term changes of the atmospheric circulation in the Northern Hemisphere and in a particular region (according to classification by B.L. Dzerdzeevskii, V.M. Kurganskaya and Z.M. Vitvitskaya. The differences in the fluctuations of selected indicators in circulation epochs are considered. The types of circulation, contribute to early or late formation of snow cover, as well as early or late it outright are identified. Macro-circulation processes which correspond with snowy or little snowy winters are defined. Time changing of maximum snow depth formation is considered. The change in frequency of extreme values of considered characteristics par circulation epochs and their relationship with macro-circulation processes, including possible tends, are analyzed. During recent years, in the Northeastern Siberia with sharp inter-annual fluctuations of atmosphere processes the later dates of setting and earlier dates of disappearance of snow cover dominate, which reduces the duration of snow cover, in comparison with long-term average. Maximum snow depth in all stations, except Anadyr, are above the average long-term value. There is a trend of increase the maximum snow depth, its duration, as well as its later formation, compare with the average, which indicates the increase in proportion of solid precipitation at the end of winter. These are facilitated by increasing of blocking atmospheric processes duration.

  12. Constraints on Saturn's Tropospheric General Circulation from Cassini ISS Images

    Science.gov (United States)

    DelGenio, Anthony D.; Barbara, John M.

    2013-01-01

    An automated cloud tracking algorithm is applied to Cassini Imaging Science Subsystem high-resolution apoapsis images of Saturn from 2005 and 2007 and moderate resolution images from 2011 and 2012 to define the near-global distribution of zonal winds and eddy momentum fluxes at the middle troposphere cloud level and in the upper troposphere haze. Improvements in the tracking algorithm combined with the greater feature contrast in the northern hemisphere during the approach to spring equinox allow for better rejection of erroneous wind vectors, a more objective assessment at any latitude of the quality of the mean zonal wind, and a population of winds comparable in size to that available for the much higher contrast atmosphere of Jupiter. Zonal winds at cloud level changed little between 2005 and 2007 at all latitudes sampled. Upper troposphere zonal winds derived from methane band images are approx. 10 m/s weaker than cloud level winds in the cores of eastward jets and approx. 5 m/s stronger on either side of the jet core, i.e., eastward jets appear to broaden with increasing altitude. In westward jet regions winds are approximately the same at both altitudes. Lateral eddy momentum fluxes are directed into eastward jet cores, including the strong equatorial jet, and away from westward jet cores and weaken with increasing altitude on the flanks of the eastward jets, consistent with the upward broadening of these jets. The conversion rate of eddy to mean zonal kinetic energy at the visible cloud level is larger in eastward jet regions (5.2x10(exp -5) sq m/s) and smaller in westward jet regions (1.6x10(exp -5) sqm/s) than the global mean value (4.1x10(ep -5) sq m/s). Overall the results are consistent with theories that suggest that the jets and the overturning meridional circulation at cloud level on Saturn are maintained at least in part by eddies due to instabilities of the large-scale flow near and/or below the cloud level.

  13. The influence of topography on Titan’s atmospheric circulation and hydrologic cycle

    Science.gov (United States)

    Lora, Juan M.; Faulk, Sean; Mitchell, Jonathan

    2017-10-01

    Titan’s atmospheric circulation is a dominant driver of the global methane hydrologic cycle—producing weather and a seasonal climate cycle—while interactions between the surface and the troposphere strongly constrain regional climates, and contribute to the differentiation between Titan’s low latitude deserts and high latitude lake districts. Yet the influence of surface topography on the atmospheric circulation has only been studied in a few instances, and no published work has investigated the coupling between topographical forcing and Titan’s hydrologic cycle. In this work, we examine the impacts of global topography in the Titan Atmospheric Model (TAM), which includes a robust representation of the methane cycle. We focus in particular on the influence of large-scale topographical features on the atmospheric flow, atmospheric moisture transport, and cloud formation. High latitude transient weather systems have previously been identified as important contributors to global atmospheric methane transport, and here we examine whether topographically-forced stationary or quasi-permanent systems are also important, as they are in Earth’s hydrologic cycle.

  14. The East Asian Atmospheric Water Cycle and Monsoon Circulation in the Met Office Unified Model

    Science.gov (United States)

    Rodríguez, José M.; Milton, Sean F.; Marzin, Charline

    2017-10-01

    In this study the low-level monsoon circulation and observed sources of moisture responsible for the maintenance and seasonal evolution of the East Asian monsoon are examined, studying the detailed water budget components. These observational estimates are contrasted with the Met Office Unified Model (MetUM) climate simulation performance in capturing the circulation and water cycle at a variety of model horizontal resolutions and in fully coupled ocean-atmosphere simulations. We study the role of large-scale circulation in determining the hydrological cycle by analyzing key systematic errors in the model simulations. MetUM climate simulations exhibit robust circulation errors, including a weakening of the summer west Pacific Subtropical High, which leads to an underestimation of the southwesterly monsoon flow over the region. Precipitation and implied diabatic heating biases in the South Asian monsoon and Maritime Continent region are shown, via nudging sensitivity experiments, to have an impact on the East Asian monsoon circulation. By inference, the improvement of these tropical biases with increased model horizontal resolution is hypothesized to be a factor in improvements seen over East Asia with increased resolution. Results from the annual cycle of the hydrological budget components in five domains show a good agreement between MetUM simulations and ERA-Interim reanalysis in northern and Tibetan domains. In simulations, the contribution from moisture convergence is larger than in reanalysis, and they display less precipitation recycling over land. The errors are closely linked to monsoon circulation biases.

  15. Integrated cumulus ensemble and turbulence (ICET): An integrated parameterization system for general circulation models (GCMs)

    Energy Technology Data Exchange (ETDEWEB)

    Evans, J.L.; Frank, W.M.; Young, G.S. [Pennsylvania State Univ., University Park, PA (United States)

    1996-04-01

    Successful simulations of the global circulation and climate require accurate representation of the properties of shallow and deep convective clouds, stable-layer clouds, and the interactions between various cloud types, the boundary layer, and the radiative fluxes. Each of these phenomena play an important role in the global energy balance, and each must be parameterized in a global climate model. These processes are highly interactive. One major problem limiting the accuracy of parameterizations of clouds and other processes in general circulation models (GCMs) is that most of the parameterization packages are not linked with a common physical basis. Further, these schemes have not, in general, been rigorously verified against observations adequate to the task of resolving subgrid-scale effects. To address these problems, we are designing a new Integrated Cumulus Ensemble and Turbulence (ICET) parameterization scheme, installing it in a climate model (CCM2), and evaluating the performance of the new scheme using data from Atmospheric Radiation Measurement (ARM) Program Cloud and Radiation Testbed (CART) sites.

  16. Asian Dust Storm Activity and Its Association with Atmospheric Circulation from 1995 to 2006

    Directory of Open Access Journals (Sweden)

    Jia-Yuh Yu

    2010-01-01

    Full Text Available In this pa per, Asian dust storm activity from 1995 to 2006 and the associated atmospheric circulation are examined using SYNOP data and the NCEP/NCAR reanalysis atmospheric data. Observations show that the Gobi Desert is the most frequent birth place for severe dust events in Asia, accounting for pproximately 58% of the total percent age, followed by about 32% from the Taklamakan Desert and nearly 10% from the Loess Plateau. Climatologically, the existence of a large-scale dry zone over mid-latitudes of Asia during the Spring pro vides a favor able environment for the frequent occurrences of dust events and subsequent dust transport across Asia.

  17. Annual mean meridional energy transport modelled by a general circulation model for present and 2 {times} CO{sub 2} equilibrium climates

    Energy Technology Data Exchange (ETDEWEB)

    Colman, R.A.; McAvaney, B.J.; Fraser, J.R.; Power, S.B. [Bureau of Meteorology Research Centre, Melbourne (Australia)

    1994-09-01

    The meridional energy flux modelled by the Bureau of Meteorology Research Centre general circulation model is examined. It is divided into atmospheric and oceanic components, and the resolved atmospheric and oceanic components, and the resolved atmospheric components in turn into mean and eddy circulations. Comparison with observations shows the modelled total planetary meridional energy transport to below, but shows better agreement for the resolved atmospheric component alone. The overall patterns of the individual circulation and energy components of the model also agree well, although strengths and locations do show some discrepancies. The doubled CO{sub 2} climate change is analyzed in terms of the changes in each of the circulation and energy components. It is found that the changes are the relatively small residual of larger, and generally opposing changes in sensible heat and potential energy fluxes. Despite the general decrease in poleward energy flux, the poleward latent heat flux is found to increase. The reduction in poleward transport is found to be dominated by changes in the mean meridional circulation at low southern latitudes, and changes in both mean circulations and eddy fluxes elsewhere. 37 refs., 11 figs.

  18. Changes in atmospheric circulation between solar maximum and minimum conditions in winter and summer

    Science.gov (United States)

    Lee, Jae Nyung

    2008-10-01

    Statistically significant climate responses to the solar variability are found in Northern Annular Mode (NAM) and in the tropical circulation. This study is based on the statistical analysis of numerical simulations with ModelE version of the chemistry coupled Goddard Institute for Space Studies (GISS) general circulation model (GCM) and National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis. The low frequency large scale variability of the winter and summer circulation is described by the NAM, the leading Empirical Orthogonal Function (EOF) of geopotential heights. The newly defined seasonal annular modes and its dynamical significance in the stratosphere and troposphere in the GISS ModelE is shown and compared with those in the NCEP/NCAR reanalysis. In the stratosphere, the summer NAM obtained from NCEP/NCAR reanalysis as well as from the ModelE simulations has the same sign throughout the northern hemisphere, but shows greater variability at low latitudes. The patterns in both analyses are consistent with the interpretation that low NAM conditions represent an enhancement of the seasonal difference between the summer and the annual averages of geopotential height, temperature and velocity distributions, while the reverse holds for high NAM conditions. Composite analysis of high and low NAM cases in both the model and observation suggests that the summer stratosphere is more "summer-like" when the solar activity is near a maximum. This means that the zonal easterly wind flow is stronger and the temperature is higher than normal. Thus increased irradiance favors a low summer NAM. A quantitative comparison of the anti-correlation between the NAM and the solar forcing is presented in the model and in the observation, both of which show lower/higher NAM index in solar maximum/minimum conditions. The summer NAM in the troposphere obtained from NCEP/NCAR reanalysis has a dipolar zonal structure with maximum

  19. Precipitation extremes in the wettest Mediterranean region (Krivošije) and associated atmospheric circulation types

    Science.gov (United States)

    Ducić, V.; Luković, J.; Burić, D.; Stanojević, G.; Mustafić, S.

    2012-03-01

    The aim of this paper is to analyse indices of extreme precipitation in Krivošije, Montenegro, the wettest Mediterranean region, from the period 1951-2007 and their relationships with atmospheric circulation using "SynopVis Grosswetterlagen" (SVG) series. Data from two stations were analysed, namely Crkvice (42°34'N and 18°39'E) and Herceg Novi (42°27'N and 18°31'E). Four indices of precipitation extremes (SDII, R75p, R95p, R95pTOT) were assessed including number of dry days. The results suggest that the number of days with precipitation decreased. To analyse the relationship between extreme precipitation events and circulation types we have used an efficiency coefficient (Ec). Regarding relation to atmospheric circulation, westerly, southwesterly and northwesterly circulation types with anticyclonic features over Central Europe are more frequent for dry days (days with Rcyclonic condition over Central Europe show a large proportion of wet and very wet days. Also, activity of Genoa cyclogenesis and orographic influence over a small area are the main reasons for the high precipitation amounts recorded in the Krivošije region (Crkvice).

  20. Debris flows in the eastern Italian Alps: seasonality and atmospheric circulation patterns

    OpenAIRE

    E. I. Nikolopoulos; M. Borga; Marra, F.; Crema, S.; Marchi, L.

    2015-01-01

    The work examines the seasonality and large-scale atmospheric circulation patterns associated with debris-flow occurrence in the Trentino–Alto Adige region (eastern Italian Alps). Analysis is based on classification algorithms applied to a uniquely dense archive of debris flows and hourly rain gauge precipitation series covering the period 2000–2009. Results highlight the seasonal and synoptic forcing patterns linked to debris flows in the study area. Summer and fall season ...

  1. First simulation results of Titan's atmosphere dynamics with a global 3-D non-hydrostatic circulation model

    Directory of Open Access Journals (Sweden)

    I. V. Mingalev

    2006-09-01

    Full Text Available We present the first results of a 3-D General Circulation Model of Titan's atmosphere which differs from traditional models in that the hydrostatic equation is not used and all three components of the neutral gas velocity are obtained from the numerical solution of the Navier-Stokes equation. The current version of our GCM is, however, a simplified version, as it uses a predescribed temperature field in the model region thereby avoiding the complex simulation of radiative transfer based on the energy equation. We present the first simulation results and compare them to the results of existing GCMs and direct wind observations. The wind speeds obtained from our GCM correspond well with data obtained during the Huygens probe descent through Titan's atmosphere. We interpret the most unexpected feature of these data which consist of the presence of a non-monotonicity of the altitude profile of the zonal wind speed between 60 and 75 km.

  2. Adaptive Error Estimation in Linearized Ocean General Circulation Models

    Science.gov (United States)

    Chechelnitsky, Michael Y.

    1999-01-01

    Data assimilation methods are routinely used in oceanography. The statistics of the model and measurement errors need to be specified a priori. This study addresses the problem of estimating model and measurement error statistics from observations. We start by testing innovation based methods of adaptive error estimation with low-dimensional models in the North Pacific (5-60 deg N, 132-252 deg E) to TOPEX/POSEIDON (TIP) sea level anomaly data, acoustic tomography data from the ATOC project, and the MIT General Circulation Model (GCM). A reduced state linear model that describes large scale internal (baroclinic) error dynamics is used. The methods are shown to be sensitive to the initial guess for the error statistics and the type of observations. A new off-line approach is developed, the covariance matching approach (CMA), where covariance matrices of model-data residuals are "matched" to their theoretical expectations using familiar least squares methods. This method uses observations directly instead of the innovations sequence and is shown to be related to the MT method and the method of Fu et al. (1993). Twin experiments using the same linearized MIT GCM suggest that altimetric data are ill-suited to the estimation of internal GCM errors, but that such estimates can in theory be obtained using acoustic data. The CMA is then applied to T/P sea level anomaly data and a linearization of a global GFDL GCM which uses two vertical modes. We show that the CMA method can be used with a global model and a global data set, and that the estimates of the error statistics are robust. We show that the fraction of the GCM-T/P residual variance explained by the model error is larger than that derived in Fukumori et al.(1999) with the method of Fu et al.(1993). Most of the model error is explained by the barotropic mode. However, we find that impact of the change in the error statistics on the data assimilation estimates is very small. This is explained by the large

  3. The climatological mean atmospheric transport under weakened Atlantic thermohaline circulation climate scenario

    Energy Technology Data Exchange (ETDEWEB)

    Erukhimova, T. [Texas A and M University, Department of Physics, College Station, TX (United States); Zhang, R. [GFDL/NOAA, Princeton, NJ (United States); Bowman, K.P. [Texas A and M University, Department of Atmospheric Sciences, College Station, TX (United States)

    2009-02-15

    Global atmospheric transport in a climate subject to a substantial weakening of the Atlantic thermohaline circulation (THC) is studied by using climatological Green's functions of the mass conservation equation for a conserved, passive tracer. Two sets of Green's functions for the perturbed climate and for the present climate are evaluated from 11-year atmospheric trajectory calculations, based on 3-D winds simulated by GFDL's newly developed global coupled ocean-atmosphere model (CM2.1). The Green's function analysis reveals pronounced effects of the climate change on the atmospheric transport, including seasonally modified Hadley circulation with a stronger Northern Hemisphere cell in DJF and a weaker Southern Hemisphere cell in JJA. A weakened THC is also found to enhance mass exchange rates through mixing barriers between the tropics and the two extratropical zones. The response in the tropics is not zonally symmetric. The 3-D Green's function analysis of the effect of THC weakening on transport in the tropical Pacific shows a modified Hadley cell in the eastern Pacific, confirming the results of our previous studies, and a weakening (strengthening) of the upward and eastward motion to the south (north) of the Equator in the western Pacific in the perturbed climate as compared to the present climate. (orig.)

  4. Prediction of cloud droplet number in a general circulation model

    Energy Technology Data Exchange (ETDEWEB)

    Ghan, S.J.; Leung, L.R. [Pacific Northwest National Lab., Richland, WA (United States)

    1996-04-01

    We have applied the Colorado State University Regional Atmospheric Modeling System (RAMS) bulk cloud microphysics parameterization to the treatment of stratiform clouds in the National Center for Atmospheric Research Community Climate Model (CCM2). The RAMS predicts mass concentrations of cloud water, cloud ice, rain and snow, and number concnetration of ice. We have introduced the droplet number conservation equation to predict droplet number and it`s dependence on aerosols.

  5. Acute effects of a large bolide impact simulated by a global atmospheric circulation model

    Science.gov (United States)

    Thompson, Starley L.; Crutzen, P. J.

    1988-01-01

    The goal is to use a global three-dimensional atmospheric circulation model developed for studies of atmospheric effects of nuclear war to examine the time evolution of atmospheric effects from a large bolide impact. The model allows for dust and NOx injection, atmospheric transport by winds, removal by precipitation, radiative transfer effects, stratospheric ozone chemistry, and nitric acid formation and deposition on a simulated Earth having realistic geography. Researchers assume a modest 2 km-diameter impactor of the type that could have formed the 32 km-diameter impact structure found near Manson, Iowa and dated at roughly 66 Ma. Such an impact would have created on the order of 5 x 10 to the 10th power metric tons of atmospheric dust (about 0.01 g cm(-2) if spread globally) and 1 x 10 to the 37th power molecules of NO, or two orders of magnitude more stratospheric NO than might be produced in a large nuclear war. Researchers ignore potential injections of CO2 and wildfire smoke, and assume the direct heating of the atmosphere by impact ejecta on a regional scale is not large compared to absorption of solar energy by dust. Researchers assume an impact site at 45 N in the interior of present day North America.

  6. Principal modes of atmospheric circulation anomalies associated with global angular momentum fluctuations

    Science.gov (United States)

    Kang, In-Sik; Lau, K.-M.

    1994-01-01

    This paper provides a description of the variability of global atmospheric angular momentum (GAM) and its relationship with principal modes of three-dimensional atmospheric circulation anomalies. The data used are 5-day mean global wind fields from the European Centre for Medium-Range Weather Forecasts initialized dataset for 1980-1989. Significant seasonal variation of GAM is observed with maxima in April and November and a minimum during late July. The amplitude of the annual cycle is largest in the upper troposphere and decreases toward the surface. Although the lower tropospheric contribution to the total angular momentum is relatively small, its annual cycle is out of phase with those of the upper atmosphere and GAM. Also identified is a distinct semiannual component, with double peaks appearing in April and November. This signal is most noticeable in the upper troposphere above the 300-mb level. The principal modes of zonal-mean angular momentum and meridional circulation anomalies and their coupled modes are obtained by using empirical orthogonal function analysis and singular value decomposition. It is shown that the leading modes of the angular momentum and meridional circulation are coupled with each other and are responsible for much of the variability in GAM. The coupled modes represent fluctuations of upper-level subtropical zonal flow, which are linked to the modulation of Hadley circulation intensity in both hemispheres. It is found that GAM is highly correlated with the first eigenvector of upper-level streamfunction anomalies, which consists of a superrotational flow in the tropics and subtropics, except over the central Pacific where a 'blocked' flow with two subtropical anticyclonic circulation cells straddling the equator is found. Much of the blocked flow is due to the establishment of dipole anomalies in the velocity potential with centers over the central Pacific and the Maritime Continent on the interannual time scale. On the intraseasonal

  7. DEBRIS FLOW AND LANDSLIDE HAZARDS UNDER CERTAIN TYPES OF ATMOSPHERIC CIRCULATION

    Directory of Open Access Journals (Sweden)

    Nina Kononova

    2012-01-01

    Full Text Available Conditions of formation and development of landslides and debris flows in the Black Sea coast of the Caucasus and on Sakhalin Island were considered. They are formed under the influence of heavy rainfall under the influence of the Mediterranean cyclones outlet in the Black Sea coast of the Caucasus and of the Pacific cyclones outlet on Sakhalin Island in the same macro-circulation processes. Activity of landslides and debris flows in these regions has been shown to be connected with certain types of atmospheric circulation during the XX—the beginning of the XXI century. Based on these results, possible increase in the activity of landslides and debris flows, in the Black Sea coast of the Caucasus and Sakhalin Island, is suggested.

  8. Bivariate spatial analysis of temperature and precipitation from general circulation models and observation proxies

    KAUST Repository

    Philbin, R.

    2015-05-22

    This study validates the near-surface temperature and precipitation output from decadal runs of eight atmospheric ocean general circulation models (AOGCMs) against observational proxy data from the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis temperatures and Global Precipitation Climatology Project (GPCP) precipitation data. We model the joint distribution of these two fields with a parsimonious bivariate Matérn spatial covariance model, accounting for the two fields\\' spatial cross-correlation as well as their own smoothnesses. We fit output from each AOGCM (30-year seasonal averages from 1981 to 2010) to a statistical model on each of 21 land regions. Both variance and smoothness values agree for both fields over all latitude bands except southern mid-latitudes. Our results imply that temperature fields have smaller smoothness coefficients than precipitation fields, while both have decreasing smoothness coefficients with increasing latitude. Models predict fields with smaller smoothness coefficients than observational proxy data for the tropics. The estimated spatial cross-correlations of these two fields, however, are quite different for most GCMs in mid-latitudes. Model correlation estimates agree well with those for observational proxy data for Australia, at high northern latitudes across North America, Europe and Asia, as well as across the Sahara, India, and Southeast Asia, but elsewhere, little consistent agreement exists.

  9. Excitation of equatorial Kelvin and Yanai waves by tropical cyclones in an ocean general circulation model

    Directory of Open Access Journals (Sweden)

    R. L. Sriver

    2013-01-01

    Full Text Available Tropical cyclones (TCs actively contribute to the dynamics of Earth's coupled climate system. They influence oceanic mixing rates, upper-ocean heat content, and air–sea fluxes, with implications for atmosphere and ocean dynamics on multiple spatial and temporal scales. Using an ocean general circulation model with modified surface wind forcing, we explore how TC winds can excite equatorial ocean waves in the tropical Pacific. We highlight a situation where three successive TCs in the western North Pacific region, corresponding to events in 2003, excite a combination of Kelvin and Yanai waves in the equatorial Pacific. The resultant thermocline adjustment significantly modifies the thermal structure of the upper equatorial Pacific and leads to eastward zonal heat transport. Observations of upper-ocean temperature by the Tropical Atmosphere Ocean (TAO buoy array and sea-level height anomalies using altimetry reveal wave passage during the same time period with similar properties to the modeled wave, although our idealized model methodology disallows precise identification of the TC forcing with the observed waves. Results indicate that direct oceanographic forcing by TCs may be important for understanding the spectrum of equatorial ocean waves, thus remotely influencing tropical mixing and surface energy budgets. Because equatorial Kelvin waves are closely linked to interannual variability in the tropical Pacific, these findings also suggest TC wind forcing may influence the timing and amplitude of El Niño events.

  10. The key role of topography in altering North Atlantic atmospheric circulation during the last glacial period

    Directory of Open Access Journals (Sweden)

    F. S. R. Pausata

    2011-10-01

    Full Text Available The Last Glacial Maximum (LGM; 21 000 yr before present was a period of low atmospheric greenhouse gas concentrations, when vast ice sheets covered large parts of North America and Europe. Paleoclimate reconstructions and modeling studies suggest that the atmospheric circulation was substantially altered compared to today, both in terms of its mean state and its variability. Here we present a suite of coupled model simulations designed to investigate both the separate and combined influences of the main LGM boundary condition changes (greenhouse gases, ice sheet topography and ice sheet albedo on the mean state and variability of the atmospheric circulation as represented by sea level pressure (SLP and 200-hPa zonal wind in the North Atlantic sector. We find that ice sheet topography accounts for most of the simulated changes during the LGM. Greenhouse gases and ice sheet albedo affect the SLP gradient in the North Atlantic, but the overall placement of high and low pressure centers is controlled by topography. Additional analysis shows that North Atlantic sea surface temperatures and sea ice edge position do not substantially influence the pattern of the climatological-mean SLP field, SLP variability or the position of the North Atlantic jet in the LGM.

  11. Simulations of physics and chemistry of polar stratospheric clouds with a general circulation model

    Energy Technology Data Exchange (ETDEWEB)

    Buchholz, J.

    2005-04-20

    A polar stratospheric cloud submodel has been developed and incorporated in a general circulation model including atmospheric chemistry (ECHAM5/MESSy). The formation and sedimentation of polar stratospheric cloud (PSC) particles can thus be simulated as well as heterogeneous chemical reactions that take place on the PSC particles. For solid PSC particle sedimentation, the need for a tailor-made algorithm has been elucidated. A sedimentation scheme based on first order approximations of vertical mixing ratio profiles has been developed. It produces relatively little numerical diffusion and can deal well with divergent or convergent sedimentation velocity fields. For the determination of solid PSC particle sizes, an efficient algorithm has been adapted. It assumes a monodisperse radii distribution and thermodynamic equilibrium between the gas phase and the solid particle phase. This scheme, though relatively simple, is shown to produce particle number densities and radii within the observed range. The combined effects of the representations of sedimentation and solid PSC particles on vertical H{sub 2}O and HNO{sub 3} redistribution are investigated in a series of tests. The formation of solid PSC particles, especially of those consisting of nitric acid trihydrate, has been discussed extensively in recent years. Three particle formation schemes in accordance with the most widely used approaches have been identified and implemented. For the evaluation of PSC occurrence a new data set with unprecedented spatial and temporal coverage was available. A quantitative method for the comparison of simulation results and observations is developed and applied. It reveals that the relative PSC sighting frequency can be reproduced well with the PSC submodel whereas the detailed modelling of PSC events is beyond the scope of coarse global scale models. In addition to the development and evaluation of new PSC submodel components, parts of existing simulation programs have been

  12. Earth Radiation Budget and Cloudiness Simulations with a General Circulation Model.

    Science.gov (United States)

    Harshvardhan; Randall, David A.; Corsetti, Thomas G.

    1989-07-01

    The UCLA/GLA general circulation model has been endowed with new parameterizations of solar and terrestrial radiation, as well as new parameterized cloud optical properties. A simple representation of the cloud liquid water feedback is included. We have used the model and several observational datasets to analyze the effects of cloudiness on the Earth's radiation budget.Analysis of January and July results obtained with the full model shows that the simulated Earth radiation budget is in reasonable agreement with Nimbus 7 data. The globally averaged planetary albedo and outgoing longwave radiation am both slightly less than observed. A tropical minimum of the outgoing longwave radiation is simulated, but is weaker than observed. Comparisons of the simulated cloudiness with observations from ISCCP and HIRS2/MSU show that the model overpredicts subtropical and midlatitude cloudiness.The simulated cloud radiative forcings at the top of the atmosphere, at the Earth's surface, and across the atmosphere are discussed, and comparisons are made with the limited observations available. The simulated atmospheric cloud radiative forcing (ACRF) is comparable in magnitude to the latent heating. We have compared the clear-sky radiation fields obtained using Methods I and II of Cess and Potter; the results show significant differences between the two methods, primarily due to systematic variations of the cloudiness with time of day.An important feature of the new terrestrial radiation parameterization is its incorporation (for the first time in this GCM) of the effects of the water vapor continuum. To determine the effects of this change on the model results, we performed a numerical experiment in which the effects of the water vapor continuum were neglected. The troposphere warmed dramatically, and shallow convection weakened, and the radiative effects of the clouds were significantly enhanced.

  13. Relay transport of aerosols to Beijing-Tianjin-Hebei region by multi-scale atmospheric circulations

    Science.gov (United States)

    Miao, Yucong; Guo, Jianping; Liu, Shuhua; Liu, Huan; Zhang, Gen; Yan, Yan; He, Jing

    2017-09-01

    The Beijing-Tianjin-Hebei (BTH) region experiences heavy aerosol pollution, which is found to have close relationships with the synoptic- and local-scale atmospheric circulations. However, how and to what extent these multi-scale circulations interplay to modulate aerosol transport have not been fully understood. To this end, this study comprehensively investigated the impacts of these circulations on aerosol transport in BTH by focusing on an episode occurred on 1 June 2013 through combining both observations and three-dimensional simulations. It was found that during this episode, the Bohai Sea acted as a transfer station, and the high-pressure system over the Yellow Sea and sea-breeze in BTH took turns to affect the transport of aerosols. In the morning, influenced by the high-pressure system, lots of aerosols emitted from Shandong and Jiangsu provinces were first transported to the Bohai Sea. After then, these aerosols were brought to the BTH region in the afternoon through the inland penetration of sea-breeze, significantly exacerbating the air quality in BTH. The inland penetration of sea-breeze could be identified by the sharp changes in ground-based observed temperature, humidity, and wind when the sea-breeze front (SBF) passed by. Combining observations with model outputs, the SBF was found to be able to advance inland more than ∼150 km till reaching Beijing. This study has important implications for better understanding the aerosol transport in BTH, and improving the forecast of such aerosol pollution.

  14. Variability of large-scale atmospheric circulation indices for the northern hemisphere during the past 100 years

    Energy Technology Data Exchange (ETDEWEB)

    Broennimann, Stefan; Stickler, Alexander [Inst. for Atmospheric and Climate Science, ETH Zurich (Switzerland); Griesser, Thomas; Fischer, Andreas M.; Grant, Andrea; Ewen, Tracy; Zhou Tianjun; Schraner, Martin; Peter, Thomas [LASG, Inst. of Atmospheric Physics, Chinese Academy of Sciences, BJ (China); Rozanov, Eugene [Inst. for Atmospheric and Climate Science, ETH Zurich (Switzerland); PMOD/WRC, Davos (Switzerland)

    2009-08-15

    We present an analysis of the large-scale atmospheric circulation variability since 1900 based on various circulation indices. They represent the main features of the zonal mean circulation in the northern hemisphere in boreal winter (such as the Hadley circulation, the subtropical jet, and the polar vortex in the lower stratosphere) as well as aspects of the regional and large-scale circulation (the Pacific Walker Circulation, the Indian monsoon, the North Atlantic Oscillation, NAO, and the Pacific North American pattern, PNA). For the past decades we calculate the indices from different reanalyses (NCEP/NCAR, ERA-40, JRA-25, ERA-Interim). For the first half of the 20{sup th} century the indices are statistically reconstructed based on historical upper-air and surface data as well as calculated from the Twentieth Century Reanalysis. The indices from all these observation-based data sets are compared to indices calculated from a 9-member ensemble of ''all forcings'' simulations performed with the chemistry-climate model SOCOL. After discussing the agreement among different data products, we analyse the interannual-to-decadal variability of the indices in the context of possible driving factors, such as El Nino/Southern Oscillation (ENSO), volcanic eruptions, and solar activity. The interannual variability of the Hadley cell strength, the subtropical jet strength, or the PNA is well reproduced by the model ensemble mean, i.e., it is predictable in the context of the specified forcings. The source of this predictability is mainly related to ENSO (or more generally, tropical sea-surface temperatures). For other indices such as the strength of the stratospheric polar vortex, the NAO, or the poleward extent of the Hadley cell the correlations between observations and model ensemble mean are much lower, but so are the correlations within the model ensemble. Multidecadal variability and trends in the individual series are discussed in the context of

  15. The GEM-Mars general circulation model for Mars: Description and evaluation

    Science.gov (United States)

    Neary, L.; Daerden, F.

    2018-01-01

    GEM-Mars is a gridpoint-based three-dimensional general circulation model (GCM) of the Mars atmosphere extending from the surface to approximately 150 km based on the GEM (Global Environmental Multiscale) model, part of the operational weather forecasting and data assimilation system for Canada. After the initial modification for Mars, the model has undergone considerable changes. GEM-Mars is now based on GEM 4.2.0 and many physical parameterizations have been added for Mars-specific atmospheric processes and surface-atmosphere exchange. The model simulates interactive carbon dioxide-, dust-, water- and atmospheric chemistry cycles. Dust and water ice clouds are radiatively active. Size distributed dust is lifted by saltation and dust devils. The model includes 16 chemical species (CO2, Argon, N2, O2, CO, H2O, CH4, O3, O(1D), O, H, H2, OH, HO2, H2O2 and O2(a1Δg)) and has fully interactive photochemistry (15 reactions) and gas-phase chemistry (31 reactions). GEM-Mars provides a good simulation of the water and ozone cycles. A variety of other passive tracers can be included for dedicated studies, such as the emission of methane. The model has both a hydrostatic and non-hydrostatic formulation, and together with a flexible grid definition provides a single platform for simulations on a variety of horizontal scales. The model code is fully parallelized using OMP and MPI. Model results are evaluated by comparison to a selection of observations from instruments on the surface and in orbit, relating to atmosphere and surface temperature and pressure, dust and ice content, polar ice mass, polar argon, and global water and ozone vertical columns. GEM-Mars will play an integral part in the analysis and interpretation of data that is received by the NOMAD spectrometer on the ESA-Roskosmos ExoMars Trace Gas Orbiter. The present paper provides an overview of the current status and capabilities of the GEM-Mars model and lays the foundations for more in-depth studies in support

  16. Climatology of atmospheric circulation patterns of Arabian dust in western Iran.

    Science.gov (United States)

    Najafi, Mohammad Saeed; Sarraf, B S; Zarrin, A; Rasouli, A A

    2017-08-28

    Being in vicinity of vast deserts, the west and southwest of Iran are characterized by high levels of dust events, which have adverse consequences on human health, ecosystems, and environment. Using ground based dataset of dust events in western Iran and NCEP/NCAR reanalysis data, the atmospheric circulation patterns of dust events in the Arabian region and west of Iran are identified. The atmospheric circulation patterns which lead to dust events in the Arabian region and western Iran were classified into two main categories: the Shamal dust events that occurs in warm period of year and the frontal dust events as cold period pattern. In frontal dust events, the western trough or blocking pattern at mid-level leads to frontogenesis, instability, and air uplift at lower levels of troposphere in the southwest of Asia. Non-frontal is other pattern of dust event in the cold period and dust generation are due to the regional circulation systems at the lower level of troposphere. In Shamal wind pattern, the Saudi Arabian anticyclone, Turkmenistan anticyclone, and Zagros thermal low play the key roles in formation of this pattern. Summer and transitional patterns are two sub-categories of summer Shamal wind pattern. In summer trough pattern, the mid-tropospheric trough leads to intensify the surface thermal systems in the Middle East and causes instability and rising of wind speed in the region. In synthetic pattern of Shamal wind and summer trough, dust is created by the impact of a trough in mid-levels of troposphere as well as existing the mentioned regional systems which are contributed in formation of summer Shamal wind pattern.

  17. Simple solutions for the summer shallow atmospheric circulation over North Africa

    Science.gov (United States)

    Dalu, Giovanni A.; Gaetani, Marco; Lavaysse, Christophe; Flamant, Cyrille; Evan, Amato T.; Baldi, Marina

    2017-04-01

    In this study, we present a model analysis of the summer shallow atmospheric circulation over North Africa driven by desert heat lows, performed by using a two layer Matsuno-Gill model system, where a lower Rayleigh frictional layer is coupled with an upper almost frictionless layer. We analyse the early summer circulation, when a single heat low spans from the west coast of Africa to the Arabian Peninsula, and the full summer circulation, when two separate heat lows are observed, one over western Sahara (the Saharan heat low, SHL) and one over the Arabian Peninsula (the Arabian heat low, AHL). In early summer, the SHL drives a lower layer cyclone and an upper layer anticyclone, with a jet on its southern edge (the African easterly jet, AEJ). The lower layer depression and its related cyclone are almost in-phase with the diabatic forcing, while the upper high pressure (West African high, WAH) and its related anticyclone are almost in quadrature with it. This phase shift between lower and upper dynamics is entirely due to the frictional difference between the two layers. The full summer shallow circulation over North Africa is characterised by two Walker-like cells, one generated by the AHL and the other generated by the SHL. These cells partially overlap resulting in a strengthening of the WAH and the AEJ. The model shows that the AEJ originates over the Arabian Peninsula, crosses the North Africa, and, invigorated by the SHL, crosses the Tropical Atlantic. The addition of a heating source in the upper layer, associated with the Saharan airborne dust, reveals a further strengthening of the AEJ.

  18. Sedimentological evaluation of general circulation model simulations for the ?greenhouse? Earth: Cretaceous and Jurassic case studies

    Science.gov (United States)

    Price, G. D.; Sellwood, B. W.; Valdes, P. J.

    1995-12-01

    Conceptual climate models, based on the workings of the present-day climate system, provided a first-order approach to ancient climate systems. They are potentially very subjective in character. Their main drawback was that they involved the relocation of continents beneath a stable atmospheric circulation modelled upon that of the present. General circulation models (GCMs) use the laws of physics and an understanding of past geography to simulate climatic responses. They are objective in character. However, they require super computers to handle vast numbers of calculations. Nonetheless it is now possible to compare results from different GCMs for a range of times and over a wide range of parameterisations. GCMs are currently producing simulated climate predictions which compare favourably with the distributions of climatically sensitive facies (e.g. coals, evaporites and palaeosols). They have been used effectively in the prediction of oceanic upwelling sites and the distribution of petroleum source-rocks and phosphorites. Parameterisation is the main weakness in GCMs (e.g. sea-surface temperature, orography, cloud behaviour). Sensitivity experiments can be run on GCMs which simulate the effects of Milankovitch forcing and thus provide insights into possible patterns of climate change both globally and locally (i.e. provide predictions that can be evaluated against the rock record). Future use of GCMs could be in the forward modelling of sequence stratigraphic evolution and in the prediction of the diagenetic characteristics of reservoir units in frontier exploration areas. The sedimentary record provides the only way that GCMs may themselves be evaluated and this is important because these same GCMs are being used currently to predict possible changes in future climate.

  19. Decadal changes in North Atlantic atmospheric circulation patterns recorded by sand spits since 1800 CE

    Science.gov (United States)

    Poirier, Clément; Tessier, Bernadette; Chaumillon, Éric; Bertin, Xavier; Fruergaard, Mikkel; Mouazé, Dominique; Noël, Suzanne; Weill, Pierre; Wöppelmann, Guy

    2017-03-01

    Present-day coastal barriers represent around 15% of the world's oceanic shorelines, and play an important role as early warning indicators of environmental change. Among them, wave-dominated barriers are dynamic landforms that tend to migrate landward in response to storms and sea-level change. High rates of sediment supply can locally offset the global retrogradation trend, providing valuable records of past environmental change occurring on transgressive coasts. However, geochronological control limits the temporal resolution of such records to millennial or centennial timescales, and the decadal or even faster response of wave-built barriers to historical climate changes is therefore poorly understood. In this study, we show that shoreline dynamics of sand spits reconstructed from old cartographic documents has been synchronous on both margins of the North Atlantic Ocean since about 1800 CE. Spit growth accelerated drastically during three periods lasting about 15 years, characterised by positive North Atlantic Oscillation (NAO) and negative East Atlantic-West Russia (EA-WR) atmospheric circulation patterns. These changes are in phase with periods of increased volcanic activity. We use a high-resolution wave hindcast (1948-2014 CE) in a reference area to confirm the association between NAO and EA-WR as a proxy for offshore and nearshore wave height and for associated longshore sediment transport (LST) involved in spit growth. A 24-month lagged correlation between sediment transport and volcanic aerosol optical thickness (concentration of ashes in the atmosphere) is observed, suggesting that spit shoreline dynamics at the decadal timescale is partially forced by external climate drivers via cascading effects on atmospheric circulation patterns and wave climate. Our results imply that NAO variability alone is not sufficient to understand the evolution of wave-built coastal environments. The associated sediment record can be used to reconstruct multi

  20. Plutonium isotopes in the atmosphere of Central Europe: Isotopic composition and time evolution vs. circulation factors

    Energy Technology Data Exchange (ETDEWEB)

    Kierepko, Renata, E-mail: Renata.Kierepko@ifj.edu.pl [Institute of Nuclear Physics, Polish Academy of Sciences, Krakow (Poland); Mietelski, Jerzy W. [Institute of Nuclear Physics, Polish Academy of Sciences, Krakow (Poland); Ustrnul, Zbigniew [Jagiellonian University, Krakow (Poland); Institute of Meteorology and Water Management, National Research Institute, Krakow (Poland); Anczkiewicz, Robert [Institute of Geological Sciences, Polish Academy of Sciences, Krakow (Poland); Wershofen, Herbert [Physikalisch-Technische Bundesanstalt, Braunschweig (Germany); Holgye, Zoltan [National Radiation Protection Institute, Prague (Czech Republic); Kapała, Jacek [Medical University of Bialystok (Poland); Isajenko, Krzysztof [Central Laboratory for Radiological Protection, Warsaw (Poland)

    2016-11-01

    This paper reports evidence of Pu isotopes in the lower part of the troposphere of Central Europe. The data were obtained based on atmospheric aerosol fraction samples collected from four places in three countries (participating in the informal European network known as the Ring of Five (Ro5)) forming a cell with a surface area of about 200,000 km{sup 2}. We compared our original data sets from Krakow (Poland, 1990–2007) and Bialystok (Poland, 1991–2007) with the results from two other locations, Prague (Czech Republic; 1997–2004) and Braunschweig (Germany; 1990–2003) to find time evolution of the Pu isotopes. The levels of the activity concentration for {sup 238}Pu and for {sup (239} {sup +} {sup 240)}Pu were estimated to be a few and some tens of nBq m{sup −} {sup 3}, respectively. However, we also noted some results were much higher (even about 70 times higher) than the average concentration of {sup 238}Pu in the atmosphere. The achieved complex data sets were used to test a new approach to the problem of solving mixing isotopic traces from various sources (here up to three) in one sample. Results of our model, supported by mesoscale atmospheric circulation parameters, suggest that Pu from nuclear weapon accidents or tests and nuclear burnt-up fuel are present in the air. - Highlights: • Evidence of Pu isotopes in the lower part of the troposphere of Central Europe • The effective annual doses associated with Pu inhalation • New approach to the problem of solving mixed Pu origins in one sample (3SM) • Relationship between Pu isotopes activity concentration and circulation factors.

  1. A global map of the atmospheric circulation and thermal structure for an ultrahot exoplanet

    Science.gov (United States)

    Evans, Tom; Sing, David; Tiffany, Kataria; Nikolov, Nikolay; Deming, Drake; Lewis, Nikole; Wakeford, Hannah; Marley, Mark; Gibson, Neale; Spake, Jessica; Drummond, Benjamin; Barstow, Joanna; Henry, Gregory; Mayne, Nathan

    2017-10-01

    WASP-121b is one of the standout exoplanets available for atmospheric characterization, both in transmission and emission, due to its large radius (1.8 Jupiter radii), high temperature ( 2700K), and bright host star (H=9.4mag). Recent HST/WFC3 eclipse observations made by our group have revealed the 1.4 micron water band in emission on the dayside hemisphere of WASP-121b, implying that the atmosphere has a thermal inversion. This new development, combined with the favorable system properties, makes it clear that WASP-121b is an ideal target to empirically probe the variation of thermal inversions with longitude. To do this, we propose phase curve measurements of WASP-121b over a full orbital period in each of the Spitzer/IRAC channels. Given the measurement precision demonstrated by our previous IRAC observations of WASP-121b, we anticipate this dataset will be one of the highest signal-to-noise phase curve measurements for an exoplanet to date. It will provide a powerful complement to full-orbit phase curves that have recently been confirmed for shorter wavelengths, to be made by HST/WFC3 and JWST/NIRISS. Combined, this Spitzer+HST+JWST phase curve dataset will produce an unprecedented map of the longitudinally-resolved thermal structure, chemical composition and global circulation of an exoplanet atmosphere, and, in particular, give crucial new insight into the long-standing mystery of thermal inversions in strongly-irradiated gas giants.

  2. Evaluation of the Surface Representation of the Greenland Ice Sheet in a General Circulation Model

    Science.gov (United States)

    Cullather, Richard I.; Nowicki, Sophie M. J.; Zhao, Bin; Suarez, Max J.

    2014-01-01

    Simulated surface conditions of the Goddard Earth Observing System model, version 5 (GEOS 5) atmospheric general circulation model (AGCM) are examined for the contemporary Greenland Ice Sheet (GrIS). A surface parameterization that explicitly models surface processes including snow compaction, meltwater percolation and refreezing, and surface albedo is found to remedy an erroneous deficit in the annual net surface energy flux and provide an adequate representation of surface mass balance (SMB) in an evaluation using simulations at two spatial resolutions. The simulated 1980-2008 GrIS SMB average is 24.7+/-4.5 cm yr(- 1) water-equivalent (w.e.) at.5 degree model grid spacing, and 18.2+/-3.3 cm yr(- 1) w.e. for 2 degree grid spacing. The spatial variability and seasonal cycle of the simulation compare favorably to recent studies using regional climate models, while results from 2 degree integrations reproduce the primary features of the SMB field. In comparison to historical glaciological observations, the coarser resolution model overestimates accumulation in the southern areas of the GrIS, while the overall SMB is underestimated. These changes relate to the sensitivity of accumulation and melt to the resolution of topography. The GEOS-5 SMB fields contrast with available corresponding atmospheric models simulations from the Coupled Model Intercomparison Project (CMIP5). It is found that only a few of the CMIP5 AGCMs examined provide significant summertime runoff, a dominant feature of the GrIS seasonal cycle. This is a condition that will need to be remedied if potential contributions to future eustatic change from polar ice sheets are to be examined with GCMs.

  3. A coupled general circulation model for the Late Jurassic including fully interactive carbon cycling

    Science.gov (United States)

    Williams, J.; Valdes, P. J.; Leith, T. L.; Sagoo, N.

    2011-12-01

    The climatology of a coupled atmosphere - ocean (including sea ice) general circulation model for the Late Jurassic epoch (Kimmeridgian stage) is presented. The simulation framework used is the FAMOUS climate model [Jones et al, Climate Dynamics 25, 189-204 (2005)], which is a reduced resolution configuration of the UK Met Office model HadCM3 [Pope et al, Climate Dynamics 16, 123-46 (2000)]. In order to enable computation of carbon fluxes through the Earth System, fully interactive terrestrial and oceanic carbon cycle modules are added to FAMOUS. These include temporally evolving vegetation on land and populations of zooplankton, phytoplankton and nitrogenous nutrients in the ocean. The Kimmeridgian was a time of significantly enhanced carbon dioxide concentrations in the atmosphere (roughly four times preindustrial) and as such is a useful test bed for "paleocalibration" of a future climate perturbed by anthropogenic emissions of greenhouse gases [Barron et al, Paleoceanography 10 (5) 953-962 (1995) for example]. From a geological perspective, the Kimmeridgian was also a time of significant laying down of hydrocarbon reserves (particularly in the North Sea) and thus the inclusion of a fully interactive carbon cycle in FAMOUS enables the study of the dysoxic (low oxygen) and circulatory conditions relevant to their formation and preservation. The parameter space of both the terrestrial and oceanic carbon cycles was explored using the Latin Hypercube method [Mckay, Proceedings of the 24th conference on winter simulation, ACM Press, Arlington, Virginia, 57-564 (1992)], which enables efficient yet rigorous sampling of multiple covarying parameters. These parameters were validated using present day observations of meteorological, vegetative and biological parameters since the data available for the Jurassic itself is relatively scarce. To remove subjective bias in the validation process, the "Arcsine Mielke" skill score was used [Watterson, Int. J. Climatology, 16, 379

  4. Easy Aerosol - Robust and non-robust circulation responses to aerosol radiative forcing in comprehensive atmosphere models

    Science.gov (United States)

    Voigt, Aiko; Bony, Sandrine; Stevens, Bjorn; Boucher, Olivier; Medeiros, Brian; Pincus, Robert; Wang, Zhili; Zhang, Kai; Lewinschal, Anna; Bellouin, Nicolas; Yang, Young-Min

    2015-04-01

    A number of recent studies illustrated the potential of aerosols to change the large-scale atmospheric circulation and precipitation patterns. It remains unclear, however, to what extent the proposed aerosol-induced changes reflect robust model behavior or are affected by uncertainties in the models' treatment of parametrized physical processes, such as those related to clouds. "Easy Aerosol", a model-intercomparison project organized within the Grand Challenge on Clouds, Circulation and Climate Sensitivity of the World Climate Research Programme, addresses this question by subjecting a suite of comprehensive atmosphere general circulation models with prescribed sea-surface temperatures (SSTs) to the same set of idealized "easy" aerosol perturbations. This contribution discusses the aerosol perturbations as well as their impact on the model's precipitation and surface winds. The aerosol perturbations are designed based on a global aerosol climatology and mimic the gravest mode of the anthropogenic aerosol. Specifically, the meridional and zonal distributions of total aerosol optical depth are approximated by a superposition of Gaussian plumes; the vertical distribution is taken as constant within the lowest 1250m of the atmosphere followed by an exponential decay with height above. The aerosol both scatters and absorbs shortwave radiation, but in order to focus on direct radiative effects aerosol-cloud interactions are omitted. Each model contributes seven simulations. A clean control case with no aerosol-radiative effects at all is compared to six perturbed simulations with differing aerosol loading, zonal aerosol distributions, and SSTs. To estimate the role of natural variability, one of the models, MPI-ESM, contributes a 5-member ensemble for each simulation. If the observed SSTs from years 1979-2005 are prescribed, the aerosol leads to a local depression of precipitation at the Northern Hemisphere center of the aerosol and a northward shift of the

  5. On the norms of r-circulant matrices with generalized Fibonacci numbers

    Directory of Open Access Journals (Sweden)

    Amara Chandoul

    2017-01-01

    Full Text Available In this paper, we obtain a generalization of [6, 8]. Firstly, we consider the so-called r-circulant matrices with generalized Fibonacci numbers and then found lower and upper bounds for the Euclidean and spectral norms of these matrices. Afterwards, we present some bounds for the spectral norms of Hadamard and Kronecker product of these matrices.

  6. Variability in winter mass balance of Northern Hemisphere glaciers and relations with atmospheric circulation

    Science.gov (United States)

    McCabe, G.J.; Fountain, A.G.; Dyurgerov, M.

    2000-01-01

    An analysis of variability in the winter mass balance (WMB) of 22 glaciers in the Northern Hemisphere indicates two primary modes of variability that explain 46% of the variability among all glaciers. The first mode of variability characterizes WMB variability in Northern and Central Europe and the second mode primarily represents WMB variability in northwestern North America, but also is related to variability in WMB of one glacier in Europe and one in Central Asia. These two modes of WMB variability are explained by variations in mesoscale atmospheric circulation which are driving forces of variations in surface temperature and precipitation. The first mode is highly correlated with the Arctic Oscillation Index, whereas the second mode is highly correlated with the Southern Oscillation Index. In addition, the second mode of WMB variability is highly correlated with variability in global winter temperatures. This result suggests some connection between global temperature trends and WMB for some glaciers.

  7. Katabatic winds over Antarctica and the relationship with Southern Hemisphere atmospheric circulation variability

    Science.gov (United States)

    Spangehl, T.; Leckebusch, G. C.; Speth, P.

    2003-04-01

    Katabatic winds are one of the outstanding features of the Antarctic boundary layer. Extreme katabatic winds can be found in a number of coastal regions where orographically induced confluence leads to further acceleration of cold air masses descending from the inner parts of the Antarctic continent. On the hemispheric scale they play an important role in maintaining the balance of mass, energy and angular momentum. Automatic weather station data and manned station data of wind speed and direction is used to assess katabatic wind activity. An objective method was developed to construct a katabatic outflow index, named KAI (from German: Katabatischer Abfluss Index). By the means of the KAI identification of katabatic outflow events was performed for 12 different regions around Antarctica. One of the main problems was to distinguish between katabatic forcing and wind regimes of pure synoptic scale origin. This will be discussed regarding the strength of the continental surface inversion. Cyclonic activity is assessed by an objective tracking method. It is investigated in how far the occurrence of regional katabatic outflow events depends on cyclones. It is especially examined in how far cyclones can favour katabatic outflow on the one hand and if cyclonic development can be modified by katabatic outflow on the other hand. Additionally, ECMWF-analysis data is used to construct a continental scale outflow index by means of mass flux. So katabatic wind activity on different spatial and temporal scales is investigated upon its relationship with extratropical and tropical atmospheric circulation variability as described by several Southern Hemisphere circulation indices. For example, it is investigated in how far katabatic wind activity can be related to the polar vortex variability in strength (Antarctic oscillation index) and eccentricity (trans polar index). Finally, process studies are performed for selected katabatic outflow events to gain a better understanding of

  8. Interactions of Multiple Atmospheric Circulation Drive the Drought in Tarim River Basin.

    Science.gov (United States)

    Wu, Yong-Ping; Feng, Guo-Lin; Li, Bai-Lian

    2016-05-20

    Global warming is likely to cause overall drying of land surfaces and aridity increasing leading to expansion of dry climate zones. There is an increased risk of extremely arid environment and large deserts developed progressively in the central Asia. However, the key factors causing the drying in mid-Asia remain inconclusive. Here, we analyzed the relationship among precipitation, water vapor transportation in Tarim River Basin (TRB) and Multiple Atmospheric Circulation (MAC) to explore the mechanism of MAC driving the drying in TRB, through comparing MAC between abundant and scarce precipitation years. We found that Westerly Circulation (WC) and Asian Summer Monsoon (ASM) are likely to promote the precipitation respectively. Whereas, they not only have their own influence but also restrict each other and facilitate the forming of peculiar water vapor transport channel for TRB, which is probably to restrain the precipitation and its distribution pattern and accelerate the drying in this region. Our results enrich the findings on mechanisms of wet places becoming wetter while dry areas getting drier under the global warming.

  9. Interactions of Multiple Atmospheric Circulation Drive the Drought in Tarim River Basin

    Science.gov (United States)

    Wu, Yong-Ping; Feng, Guo-Lin; Li, Bai-Lian

    2016-05-01

    Global warming is likely to cause overall drying of land surfaces and aridity increasing leading to expansion of dry climate zones. There is an increased risk of extremely arid environment and large deserts developed progressively in the central Asia. However, the key factors causing the drying in mid-Asia remain inconclusive. Here, we analyzed the relationship among precipitation, water vapor transportation in Tarim River Basin (TRB) and Multiple Atmospheric Circulation (MAC) to explore the mechanism of MAC driving the drying in TRB, through comparing MAC between abundant and scarce precipitation years. We found that Westerly Circulation (WC) and Asian Summer Monsoon (ASM) are likely to promote the precipitation respectively. Whereas, they not only have their own influence but also restrict each other and facilitate the forming of peculiar water vapor transport channel for TRB, which is probably to restrain the precipitation and its distribution pattern and accelerate the drying in this region. Our results enrich the findings on mechanisms of wet places becoming wetter while dry areas getting drier under the global warming.

  10. Sensitivity of two Iberian lakes to North Atlantic atmospheric circulation modes

    Science.gov (United States)

    Hernández, Armand; Trigo, Ricardo M.; Pla-Rabes, Sergi; Valero-Garcés, Blas L.; Jerez, Sonia; Rico-Herrero, Mayte; Vega, José C.; Jambrina-Enríquez, Margarita; Giralt, Santiago

    2015-12-01

    The North Atlantic Oscillation (NAO) exerts a major influence on the climate of the North Atlantic region. However, other atmospheric circulation modes (ACMs), such as the East Atlantic (EA) and Scandinavian (SCAND) patterns, also play significant roles. The dynamics of lakes on the Iberian Peninsula are greatly controlled by climatic parameters, but their relationship with these various ACMs has not been investigated in detail. In this paper, we analyze monthly meteorological and limnological long-term datasets (1950-2011 and 1992-2011, respectively) from two lakes on the northern and central Iberian Peninsula (Sanabria and Las Madres) to develop an understanding of the seasonal sensitivity of these freshwater systems to the NAO, EA and SCAND circulation modes. The limnological variability within Lake Sanabria is primarily controlled by fluctuations in the seasonal precipitation and wind, and the primary ACMs associated with the winter limnological processes are the NAO and the SCAND modes, whereas only the EA mode appears to weakly influence processes during the summer. However, Lake Las Madres is affected by precipitation, wind and, to a lesser extent, temperature, whereas the ACMs have less influence. Therefore, we aim to show that the lakes of the Iberian Peninsula are sensitive to these ACMs. The results presented here indicate that the lake dynamics, in some cases, have a higher sensitivity to variations in the ACMs than single local meteorological variables. However, certain local features, such as geography, lake morphology and anthropic influences, are crucial to properly record the signals of these ACMs.

  11. The nonlinear variation of drought and its relation to atmospheric circulation in Shandong Province, East China

    Directory of Open Access Journals (Sweden)

    Baofu Li

    2015-10-01

    Full Text Available Considerable attention has recently been devoted to the linear trend of drought at the decadal to inter-decadal time scale; however, the nonlinear variation of drought at multi-decadal scales and its relation to atmospheric circulation need to be further studied. The linear and nonlinear variations of the Palmer drought severity index (PDSI in Shandong from 1900 to 2012 and its relations to the Pacific decadal oscillation (PDO, El Niño-Southern Oscillation (ENSO, Siberian high (SH and Southern Oscillation (SO phase changes from multi-scale are detected using linear regression, the Mann–Kendall test, ensemble empirical mode decomposition (EEMD and the Pearson correlation analysis method. The results indicate that the PDSI shows no statistically significant linear change trend from 1900 to 2012; however, before (after the late 1950s, PDSI shows a significant upward (downward trend (P < 0.01 with a linear rate of 0.28/decade (−0.48/decade. From 1900 to 2012, the PDSI also exhibits a nonlinear variation trend at the inter-annual scale (quasi-3 and quasi-7-year, inter-decadal scale (quasi-14-year and multi-decadal scale (quasi-46 and quasi-65-year. The variance contribution rate of components from the inter-annual scale is the largest, reaching 38.7%, and that from the inter-decadal scale and multi-decadal scale are 18.9% and 19.0%, respectively, indicating that the inter-annual change exerts a huge influence on the overall PDSI change. The results also imply that the effect of the four atmospheric circulations (PDO, ENSO, SH, SO on PDSI at the multi-decadal variability scale are more important than that at the other scales. Consequently, we state that PDSI variation at the inter-annual scale has more instability, while that at the inter-decadal and multi-decadal scale is more strongly influenced by natural factors.

  12. Culturable bacteria in Himalayan glacial ice in response to atmospheric circulation

    Directory of Open Access Journals (Sweden)

    S. Zhang

    2007-01-01

    Full Text Available Only recently has specific attention been given to culturable bacteria in Tibetan glaciers, but their relation to atmospheric circulation is less understood yet. Here we present the results of culturable bacteria preserved in an ice core drilled from the East Rongbuk (ER glacier, Himalayas. The average concentrations of culturable bacteria are 5.0, 0.8, 0.1 and 0.7 CFU mL−1 for the glacier ice deposited during the premonsoon, monsoon, postmonsoon and winter seasons, respectively. The high concentration of culturable bacteria in ER glacier deposited during the premonsoon season is attributed to the transportation of continental dust stirred up by the frequent dust storms during spring. This is also confirmed by the spatial distribution of culturable bacteria in Tibetan glaciers. Continental dust originated from the Northwest China accounts for the high abundance of culturable bacteria in the northern Tibetan Plateau, while monsoon moisture exerts great influence on culturable bacteria with low abundance in the southern plateau. The numbers of representatives with different ARDRA patterns from RFLP analysis are 10, 15, 1 and 2 for the glacial ice deposited during the premonsoon, monsoon, postmonsoon and winter seasons, respectively, suggesting that culturable bacteria deposited in ER glacier during monsoon season are more diverse than that deposited during the other seasons, possibly due to their derivation from both marine air masses and local or regional continental sources, while culturable bacteria deposited during the other seasons are from only one possible origin that is transported by westerlies. Our results show the first report of seasonal variations of abundance and species diversity of culturable bacteria recovered from glacial ice in the Himalayas, and we suggest that microorganisms in Himalayan ice might provide a potential new proxy for the reconstruction of atmospheric circulation.

  13. Vertical Heat Flux in the Ocean: Estimates from Observations, and Comparisons with a Coupled General Circulation Model

    Science.gov (United States)

    Cummins, P. F.; Masson, D.; Saenko, O.

    2016-02-01

    The net heat uptake by the ocean in a changing climate involves small imbalances between the advective and diffusive processes that transport heat vertically. Generally, it is necessary to rely on global climate models to study these processes in detail. In the present study, it is shown that a key component of the vertical heat flux, namely that associated with the large-scale mean vertical circulation, can be diagnosed over extra-tropical regions from global observational data sets. This component is estimated based on the vertical velocity obtained from the geostrophic vorticity balance, combined with estimates of the absolute geostrophic flow. Results are compared with a non-eddy resolving, coupled atmosphere-ocean general circulation model. This shows reasonable agreement in the latitudinal distribution of the heat flux, along with net integrated vertical heat flux below about 300 meters depth. The mean vertical heat flux is shown to be dominated by the downward contribution from the southern hemisphere and, in particular, the Southern Ocean. This is driven by the Ekman vertical velocity which induces an upward vertical transport of seawater that is cold relative to the lateral average at a given depth. The correspondence with the coupled model breaks down at depths shallower than 300 m due to the dominant contribution of equatorial regions which have been excluded from the calculation. It appears that the vertical transport of heat by the large-scale mean circulation is consistent with simple linear vorticity dynamics over much of the ocean.

  14. Trends in frequency and persistence of atmospheric circulation types over Europe derived from a multitude of classifications

    Czech Academy of Sciences Publication Activity Database

    Kučerová, Monika; Beck, Ch.; Philipp, A.; Huth, Radan

    2017-01-01

    Roč. 37, č. 5 (2017), s. 2502-2521 ISSN 0899-8418 R&D Projects: GA ČR(CZ) GPP209/12/P811; GA ČR(CZ) GA16-04676S Institutional support: RVO:68378289 Keywords : atmospheric circulation * classification * circulation type * trend * persistence * Europe * COST733cat Subject RIV: DG - Athmosphere Sciences, Meteorology OBOR OECD: Meteorology and atmospheric sciences Impact factor: 3.760, year: 2016 http://onlinelibrary.wiley.com/doi/10.1002/joc.4861/full

  15. Using Search Algorithms and Probabilistic Graphical Models to Understand the Influence of Atmospheric Circulation on Western US Drought

    Science.gov (United States)

    Malevich, S. B.; Woodhouse, C. A.

    2015-12-01

    This work explores a new approach to quantify cool-season mid-latitude circulation dynamics as they relate western US streamflow variability and drought. This information is used to probabilistically associate patterns of synoptic atmospheric circulation with spatial patterns of drought in western US streamflow. Cool-season storms transport moisture from the Pacific Ocean and are a primary source for western US streamflow. Studies overthe past several decades have emphasized that the western US hydroclimate is influenced by the intensity and phasing of ocean and atmosphere dynamics and teleconnections, such as ENSO and North Pacific variability. These complex interactions are realized in atmospheric circulation along the west coast of North America. The region's atmospheric circulation can encourage a preferential flow in winter storm tracks from the Pacific, and thus influence the moisture conditions of a given river basin over the course of the cool season. These dynamics have traditionally been measured with atmospheric indices based on values from fixed points in space or principal component loadings. This study uses collective search agents to quantify the position and intensity of potentially non-stationary atmosphere features in climate reanalysis datasets, relative to regional hydrology. Results underline the spatio-temporal relationship between semi-permanent atmosphere characteristics and naturalized streamflow from major river basins of the western US. A probabilistic graphical model quantifies this relationship while accounting for uncertainty from noisy climate processes, and eventually, limitations from dataset length. This creates probabilities for semi-permanent atmosphere features which we hope to associate with extreme droughts of the paleo record, based on our understanding of atmosphere-streamflow relations observed in the instrumental record.

  16. Respective roles of direct GHG radiative forcing and induced Arctic sea ice loss on the Northern Hemisphere atmospheric circulation

    Science.gov (United States)

    Oudar, Thomas; Sanchez-Gomez, Emilia; Chauvin, Fabrice; Cattiaux, Julien; Terray, Laurent; Cassou, Christophe

    2017-12-01

    The large-scale and synoptic-scale Northern Hemisphere atmospheric circulation responses to projected late twenty-first century Arctic sea ice decline induced by increasing Greenhouse Gases (GHGs) concentrations are investigated using the CNRM-CM5 coupled model. An original protocol, based on a flux correction technique, allows isolating the respective roles of GHG direct radiative effect and induced Arctic sea ice loss under RCP8.5 scenario. In winter, the surface atmospheric response clearly exhibits opposing effects between GHGs increase and Arctic sea ice loss, leading to no significant pattern in the total response (particularly in the North Atlantic region). An analysis based on Eady growth rate shows that Arctic sea ice loss drives the weakening in the low-level meridional temperature gradient, causing a general decrease of the baroclinicity in the mid and high latitudes, whereas the direct impact of GHGs increase is more located in the mid-to-high troposphere. Changes in the flow waviness, evaluated from sinuosity and blocking frequency metrics, are found to be small relative to inter-annual variability.

  17. First simulation results of Titan's atmosphere dynamics with a global 3-D non-hydrostatic circulation model

    Directory of Open Access Journals (Sweden)

    I. V. Mingalev

    2006-09-01

    Full Text Available We present the first results of a 3-D General Circulation Model of Titan's atmosphere which differs from traditional models in that the hydrostatic equation is not used and all three components of the neutral gas velocity are obtained from the numerical solution of the Navier-Stokes equation. The current version of our GCM is, however, a simplified version, as it uses a predescribed temperature field in the model region thereby avoiding the complex simulation of radiative transfer based on the energy equation. We present the first simulation results and compare them to the results of existing GCMs and direct wind observations. The wind speeds obtained from our GCM correspond well with data obtained during the Huygens probe descent through Titan's atmosphere. We interpret the most unexpected feature of these data which consist of the presence of a non-monotonicity of the altitude profile of the zonal wind speed between 60 and 75 km.

  18. Precipitation characteristics for the Slovak republic and their link to the atmospheric circulation

    Science.gov (United States)

    Pokorná, Lucie; Pecho, Jozef; Faško, Pavol

    2013-04-01

    Slovak Republic is situated in the centre of Europe. Its terrain is rugged and altitude increases from the southern lowlands to mountains in the northeastern and northern parts of the region where it reaches more than 2000 m a. s. l. Precipitation in this region is affected by atmospheric systems coming from the Atlantic ocean (western direction) on one hand and from the Mediterranean on the other hand (southern direction). However cyclones passing the Baltic Sea play a significant role determining precipitation occurrence and amounts as well. All these factors together with local effects lead to three different precipitation regimes in Slovakia: (i) Continental (with low precipitation in winter and the highest in summer), (ii) Atlantic (with equally distributed precipi¬tation all year round) and (iii) Mediterranean (with highest pre¬cipitation in June or May and secon¬dary maximum in October-December). The Mediterranean regime is more pronounced in the southern part of Central Slovakia while the Continental in the northeastern Slovakia. In the contribution we focus on distribution of precipitation amounts during the year and on trends in occurrence of extreme precipitation and droughts. Series from 50 meteorological stations in the Slovak Republic from the period 1951, resp. 1961-2010, are used. The sub-regions with typical annual courses of precipitation are identified using cluster analysis. The temporal behaviour of mean precipitation totals during the second half of the 20th century is characterized by a significant decrease until the mid-1990s followed by an increase up to the present. The increase of precipitation totals is registered mainly in winter, and partly also in spring and autumn. Nevertheless the increase is not regular; short periods with heavy precipi-tation as well as longer and more severe drought spells have occurred more frequently in two recent decades. In the second part of this work, the influence of atmospheric circulation on

  19. Major River Floods and Severe Winter Storms Linked To Changes of The Atmospheric Circulation Across Europe

    Science.gov (United States)

    Caspary, H. J.

    During the last two decades Western and Central Europe faced several severe winter storms and major river floodings. The recent winter storms "Anatol" (3.-4.12.1999) in Northern Europe, "Lothar" (26.12.1999) in France, Switzerland, and Southwest Ger- many and "Martin" (27.12.1999) in France, Spain and Switzerland caused economic losses of 17.7 billion US- including 10.4 billion US- insured losses and more than 160 fatalities. From 25.01.-01.03.1990 a series of 8 winter storms caused economic losses of 14.8 billion US- and 230 fatalities. The major river floods of Dec. 1993 and Jan. 1995 in Germany, Belgium, France, and Netherlands caused economic losses of more than 4.7 billion US-. It will be demonstrated that all these winter storms and most of the major river floods in Southwest and Western Germany were produced by a few types of zonal circulations across Europe. The frequency and persistence of these zonal atmospheric circulation types have increased dramatically for the winter months (Dec.- Feb.) during the recent three decades. For their time series from 1881- 2001, nonparametric tests show that nonstationarity of the winter frequencies started in 1973. As a consequence of this, the winter precipitation has increased highly signif- icant in most parts of Southwest Germany. It will be demonstrated that the increasing trends in the time series of annual peak discharges of four river basins of Southwest Germany are closely linked to the frequency changes of the zonal circulations. During the observation period (1926-2001)nearly all extreme floods including the floods of Feb. 1990, Dec. 1993, Jan. 1995, Feb. 1997, and Oct. 1998 for all four basins have been caused by heavy, long lasting rainfall during zonal circulations, especially the type "West cyclonic" (Wz) during winter. It will be demonstrated that this leads to an increased flood risk. Nonstationarity of the peak discharges does not concern all Germany but for large areas of Southwest Germany the

  20. A comparison of general circulation model predictions to sand drift and dune orientations

    Energy Technology Data Exchange (ETDEWEB)

    Blumberg, D.G. [Arizona State Univ., Tempe, AZ (United States); Greeley, R. [Arizona State Univ., Tempe, AZ (United States)]|[Ben-Gurion Univ. of the Negev, Beer-Shera (Israel)

    1996-12-01

    The growing concern over climate change and decertification stresses the importance of aeolian process prediction. In this paper the use of a general circulation model to predict current aeolian features is examined. A GCM developed at NASA/Goddard Space Flight Center was used in conjunction with White`s aeolian sand flux model to produce a global potential aeolian transport map. Surface wind shear stress predictions were used from the output of a GCM simulation that was performed as part of the Atmospheric Model Intercomparison Project on 1979 climate conditions. The spatial resolution of this study (as driven by the GCM) is 4{degrees} X 5{degrees}; instantaneous 6-hourly wind stress data were saved by the GCM and used in this report. A global map showing potential sand transport was compared to drift potential directions as inferred from Landsat images from the 1980s for several sand seas and a coastal dune field. Generally, results show a good correlation between the simulated sand drift direction and the drift direction inferred for dune forms. Discrepancies between the drift potential and the drift inferred from images were found in the North American deserts and the Arabian peninsula. An attempt to predict the type of dune that would be formed in specific regions was not successful. The model could probably be further improved by incorporating soil moisture, surface roughness, and vegetation information for a better assessment of sand threshold conditions. The correlation may permit use of a GCM to analyze {open_quotes}fossil{close_quotes} dunes or to forecast aeolian processes. 48 refs., 8 figs.

  1. Spectral Energy Budget of High Resolution General Circulation Models: Simulation of the Direct Energy Cascade

    Science.gov (United States)

    Augier, P.; Lindborg, E.

    2012-12-01

    Nastrom and Gage (1985) showed that the atmospheric kinetic energy and potential temperature spectra measured in the upper troposphere and lower stratosphere present two inertial ranges. At the mesoscales, the spectra have a kh-5/3 power law dependence. At larger scales, there is a narrow range where the spectra show a kh-3 dependence. Recently, there has been considerable progress in simulating the observed spectra with some high resolution General Circulation Models (GCMs) (see e.g.~Hamilton et al., 2008). Our aim is to understand fundamental mechanisms of energy transfer between different scales and how well these mechanisms are described by different GCMs. In particular, we wish to test the hypothesis recently proposed by Vallgren, Deusebio & Lindborg (2011), that the atmospheric kinetic and potential energy spectra can be explained by assuming that there are two cascade processes emanating from the same large-scale energy source at scales of thousands of kilometers. In order to do this, we calculate the spectral budgets of energy using data from different GCMs, including data from the T639L24 AFES model and the T1279L91 ECMWF Integrated Forecast System. The concept of available potential energy (APE, Lorenz, 1955) has been used to formulate the spectral budgets of the so-called ``primitive equations'' in pressure coordinates, with spherical harmonics as the base functions, and taking into account the topography. The ratio of the total APE over the total kinetic energy (KE) is large, of the order of 3. This is due to a larger magnitude of the APE spectrum at the very large scales of the atmosphere (total wavenumber l ≤slant 3). At the other scales, APE and KE spectra are of the same order of magnitude. For the ECMWF model and at the synoptic scales, the APE spectrum is half the KE spectrum as predicted by Charney (1971). The main terms of the spectral energy budget are computed, which allows us to present a spectral representation of the Lorenz energy cycle

  2. Impacts of Local Soil Moisture Anomalies on the Atmospheric Circulation and on Remote Surface Meteorological Fields During Boreal Summer: A Comprehensive Analysis over North America

    Science.gov (United States)

    Koster, Randal D.; Chang, Yehui; Wang, Hailan; Schubert, Siegfried D.

    2016-01-01

    We perform a series of stationary wave model (SWM) experiments in which the boreal summer atmosphere is forced, over a number of locations in the continental U.S., with an idealized diabatic heating anomaly that mimics the atmospheric heating associated with a dry land surface. For localized heating within a large portion of the continental interior, regardless of the specific location of this heating, the spatial pattern of the forced atmospheric circulation anomaly (in terms of 250-mb eddy streamfunction) is largely the same: a high anomaly forms over west central North America and a low anomaly forms to the east. In supplemental atmospheric general circulation model (AGCM) experiments, we find similar results; imposing soil moisture dryness in the AGCM in different locations within the US interior tends to produce the aforementioned pattern, along with an associated near-surface warming and precipitation deficit in the center of the continent. The SWM-based and AGCM-based patterns generally agree with composites generated using reanalysis and precipitation gauge data. The AGCM experiments also suggest that dry anomalies imposed in the lower Mississippi Valley have remote surface impacts of particularly large spatial extent, and a region along the eastern half of the US-Canada border is particularly sensitive to dry anomalies in a number of remote areas. Overall, the SWM and AGCM experiments support the idea of a positive feedback loop operating over the continent: dry surface conditions in many interior locations lead to changes in atmospheric circulation that act to enhance further the overall dryness of the continental interior.

  3. Lowering of glacial atmospheric CO2 in response to changes in oceanic circulation and marine biogeochemistry

    Science.gov (United States)

    Brovkin, Victor; Ganopolski, Andrey; Archer, David; Rahmstorf, Stefan

    2007-12-01

    We use an Earth system model of intermediate complexity, CLIMBER-2, to investigate what recent improvements in the representation of the physics and biology of the glacial ocean imply for the atmospheric concentration. The coupled atmosphere-ocean model under the glacial boundary conditions is able to reproduce the deep, salty, stagnant water mass inferred from Antarctic deep pore water data and the changing temperature of the entire deep ocean. When carbonate compensation is included in the model, we find a CO2 drawdown of 43 ppmv associated mainly with the shoaling of the Atlantic thermohaline circulation and an increased fraction of water masses of southern origin in the deep Atlantic. Fertilizing the Atlantic and Indian sectors of the Southern Ocean north of the polar front leads to a further drawdown of 37 ppmv. Other changes to the glacial carbon cycle include a decrease in the amount of carbon stored in the terrestrial biosphere (540 Pg C), which increases atmospheric CO2 by 15 ppmv, and a change in ocean salinity resulting from a drop in sea level, which elevates CO2 by another 12 ppmv. A decrease in shallow water CaCO3 deposition draws down CO2 by 12 ppmv. In total, the model is able to explain more than two thirds (65 ppmv) of the glacial to interglacial CO2 change, based only on mechanisms that are clearly documented in the proxy data. A good match between simulated and reconstructed distribution of δ13C changes in the deep Atlantic suggests that the model captures the mechanisms of reorganization of biogeochemistry in the Atlantic Ocean reasonably well. Additional, poorly constrained mechanisms to explain the rest of the observed drawdown include changes in the organic carbon:CaCO3 ratio of sediment rain reaching the seafloor, iron fertilization in the subantarctic Pacific Ocean, and changes in terrestrial weathering.

  4. General theory of light propagation and imaging through the atmosphere

    CERN Document Server

    McKechnie, T Stewart

    2016-01-01

    This book lays out a new, general theory of light propagation and imaging through Earth’s turbulent atmosphere. Current theory is based on the – now widely doubted – assumption of Kolmogorov turbulence. The new theory is based on a generalized atmosphere, the turbulence characteristics of which can be established, as needed, from readily measurable properties of point-object, or star, images. The pessimistic resolution predictions of Kolmogorov theory led to lax optical tolerance prescriptions for large ground-based astronomical telescopes which were widely adhered to in the 1970s and 1980s. Around 1990, however, it became clear that much better resolution was actually possible, and Kolmogorov tolerance prescriptions were promptly abandoned. Most large telescopes built before 1990 have had their optics upgraded (e.g., the UKIRT instrument) and now achieve, without adaptive optics (AO), almost an order of magnitude better resolution than before. As well as providing a more comprehensive and precise under...

  5. Simulation of the Low-Level-Jet by general circulation models

    Energy Technology Data Exchange (ETDEWEB)

    Ghan, S.J. [Pacific Northwest National Lab., Richland, WA (United States)

    1996-04-01

    To what degree is the low-level jet climatology and it`s impact on clouds and precipitation being captured by current general circulation models? It is hypothesised that a need for a pramaterization exists. This paper describes this parameterization need.

  6. Midlatitude Forcing Mechanisms for Glacier Mass Balance Investigated Using General Circulation Models

    NARCIS (Netherlands)

    Reichert, B.K.; Bengtsson, L.; Oerlemans, J.

    2001-01-01

    A process-oriented modeling approach is applied in order to simulate glacier mass balance for individual glaciers using statistically downscaled general circulation models (GCMs). Glacier-specific seasonal sensitivity characteristics based on a mass balance model of intermediate complexity are used

  7. Selected translated abstracts of Russian-language climate-change publications. 4: General circulation models

    Energy Technology Data Exchange (ETDEWEB)

    Burtis, M.D. [comp.] [Oak Ridge National Lab., TN (United States). Carbon Dioxide Information Analysis Center; Razuvaev, V.N.; Sivachok, S.G. [All-Russian Research Inst. of Hydrometeorological Information--World Data Center, Obninsk (Russian Federation)

    1996-10-01

    This report presents English-translated abstracts of important Russian-language literature concerning general circulation models as they relate to climate change. Into addition to the bibliographic citations and abstracts translated into English, this report presents the original citations and abstracts in Russian. Author and title indexes are included to assist the reader in locating abstracts of particular interest.

  8. Aluminium in an ocean general circulation model compared with the West Atlantic Geotraces cruises

    CSIR Research Space (South Africa)

    Van Hulten, M

    2013-10-01

    Full Text Available A model of aluminium has been developed and implemented in an Ocean General Circulation Model (NEMO-PISCES). In the model, aluminium enters the ocean by means of dust deposition. The internal oceanic processes are described by advection, mixing...

  9. Trends in persistent seasonal-scale atmospheric circulation patterns responsible for precipitation and temperature extremes in California

    Science.gov (United States)

    Swain, D. L.; Horton, D. E.; Singh, D.; Diffenbaugh, N. S.

    2015-12-01

    Long-lived anomalous atmospheric circulation patterns are often associated with surface weather extremes. This is particularly true from a hydroclimatic perspective in regions that have well-defined "wet seasons," where atmospheric anomalies that persist on a seasonal scale can lead to drought or (conversely) increase the risk of flood. Recent evidence suggests that both natural variability and global warming may be responsible for spatially and temporally heterogeneous changes in Northern Hemisphere atmospheric conditions over the past several decades. In this investigation, we assess observed trends in cool-season (Oct-May) circulation patterns over the northeastern Pacific Ocean which have historically been associated with precipitation and temperature extremes in California. We find that the occurrence of certain extreme seasonal-scale atmospheric configurations has changed substantially over the 1948-2015 period, and also that there has been a trend towards amplification of the cool-season mean state in this region. Notably, patterns similar to the persistent anticyclone associated with the extremely warm and dry conditions experienced during the ongoing 2012-2015 California drought occur more frequently in the second half of the observed record. This finding highlights the importance of examining changes in extreme and/or persistent atmospheric circulation configurations, which may exhibit different responses to natural and anthropogenic forcings than the mean state.

  10. Removing Circulation Effects to Assess Central U.S. Land-Atmosphere Interactions in the CESM Large Ensemble

    Science.gov (United States)

    Merrifield, Anna; Lehner, Flavio; Xie, Shang-Ping; Deser, Clara

    2017-10-01

    Interannual variability of summer surface air temperature (SAT) in the central United States (U.S.) is influenced by atmospheric circulation and land surface feedbacks. Here a method of dynamical adjustment is used to remove the effects of circulation on summer SAT variability over North America in the Community Earth System Model Large Ensemble. The residual SAT variability is shown to reflect thermodynamic feedbacks associated with land surface conditions. In particular, the central U.S. is a "hot spot" of land-atmosphere interaction, with residual SAT accounting for more than half of the total SAT variability. Within the "hot spot," residual SAT anomalies show higher month-to-month persistence through the warm season and a redder spectrum than dynamically induced SAT anomalies. Residual SAT variability in this region is also shown to be related to preseason soil moisture conditions, surface flux variability, and local atmospheric pressure anomalies.

  11. Impact of atmospheric circulation types on southwest Asian dust and Indian summer monsoon rainfall

    Science.gov (United States)

    Kaskaoutis, D. G.; Houssos, E. E.; Solmon, F.; Legrand, M.; Rashki, A.; Dumka, U. C.; Francois, P.; Gautam, R.; Singh, R. P.

    2018-03-01

    This study examines the meteorological feedback on dust aerosols and rainfall over the Arabian Sea and India during the summer monsoon using satellite data, re-analysis and a regional climate model. Based on days with excess aerosol loading over the central Ganges basin during May - September, two distinct atmospheric circulation types (weather clusters) are identified, which are associated with different dust-aerosol and rainfall distributions over south Asia, highlighting the role of meteorology on dust emissions and monsoon rainfall. Each cluster is characterized by different patterns of mean sea level pressure (MSLP), geopotential height at 700 hPa (Z700) and wind fields at 1000 hPa and at 700 hPa, thus modulating changes in dust-aerosol loading over the Arabian Sea. One cluster is associated with deepening of the Indian/Pakistan thermal low leading to (i) increased cyclonicity and thermal convection over northwestern India and Arabian Peninsula, (ii) intensification of the southwest monsoon off the Horn of Africa, iii) increase in dust emissions from Rub-Al-Khali and Somalian deserts, (iv) excess dust accumulation over the Arabian Sea and, (v) strengthening of the convergence of humid air masses and larger precipitation over Indian landmass compared to the other cluster. The RegCM4.4 model simulations for dust-aerosol and precipitation distributions support the meteorological fields and satellite observations, while the precipitation over India is positively correlated with the aerosol loading over the Arabian Sea on daily basis for both weather clusters. This study highlights the key role of meteorology and atmospheric dynamics on dust life cycle and rainfall over the monsoon-influenced south Asia.

  12. Models for changes in atmospheric carbon dioxide, ocean geochemistry and circulation during the late Pleistocene

    Digital Repository Service at National Institute of Oceanography (India)

    Naqvi, S.W.A.; SenGupta, R.

    the regionally varying responses of primary productivity and water circulation to the climatic changes. For example, given the unique seasonally varying circulation pattern and an acute deficiency in dissolved oxygen at mid-depth, the feedback mechanisms...

  13. Linking atmospheric circulation to daily rainfall patterns across the Murrumbidgee River Basin.

    Science.gov (United States)

    Charles, S P; Bates, B C; Viney, N R

    2003-01-01

    The hydrological cycle in Australia covers an extraordinary range of climatic and hydrologic regimes. It is now widely accepted that Australian hydrology is significantly different from all other regions and continents with the partial exception of southern Africa. Rainfall variability is very high in almost all regions with respect to amount and the lengths of wet and dry spells. These factors are keys to the behaviour and health of Australian aquatic ecosystems and water resources. Thus assessment of how rainfall may change under a potential future climate is critical. For a case study of the Murrumbidgee River Basin (MRB), a statistical downscaling model that links broad scale atmospheric circulation to multi-site, daily precipitation is assessed using observed data. This model can be driven with climate model simulations to produce rainfall scenarios at the scale required by impacts models. These can then be used in probabilistic risk assessments of climate change impacts on river health. These issues will be discussed in the context of assessing the potential impacts of precipitation changes due to projected climate change on river health.

  14. Regional climates in the GISS general circulation model: Surface air temperature

    Science.gov (United States)

    Hewitson, Bruce

    1994-01-01

    One of the more viable research techniques into global climate change for the purpose of understanding the consequent environmental impacts is based on the use of general circulation models (GCMs). However, GCMs are currently unable to reliably predict the regional climate change resulting from global warming, and it is at the regional scale that predictions are required for understanding human and environmental responses. Regional climates in the extratropics are in large part governed by the synoptic-scale circulation and the feasibility of using this interscale relationship is explored to provide a way of moving to grid cell and sub-grid cell scales in the model. The relationships between the daily circulation systems and surface air temperature for points across the continental United States are first developed in a quantitative form using a multivariate index based on principal components analysis (PCA) of the surface circulation. These relationships are then validated by predicting daily temperature using observed circulation and comparing the predicted values with the observed temperatures. The relationships predict surface temperature accurately over the major portion of the country in winter, and for half the country in summer. These relationships are then applied to the surface synoptic circulation of the Goddard Institute for Space Studies (GISS) GCM control run, and a set of surface grid cell temperatures are generated. These temperatures, based on the larger-scale validated circulation, may now be used with greater confidence at the regional scale. The generated temperatures are compared to those of the model and show that the model has regional errors of up to 10 C in individual grid cells.

  15. JIGSAW-GEO (1.0: locally orthogonal staggered unstructured grid generation for general circulation modelling on the sphere

    Directory of Open Access Journals (Sweden)

    D. Engwirda

    2017-06-01

    Full Text Available An algorithm for the generation of non-uniform, locally orthogonal staggered unstructured spheroidal grids is described. This technique is designed to generate very high-quality staggered Voronoi–Delaunay meshes appropriate for general circulation modelling on the sphere, including applications to atmospheric simulation, ocean-modelling and numerical weather prediction. Using a recently developed Frontal-Delaunay refinement technique, a method for the construction of high-quality unstructured spheroidal Delaunay triangulations is introduced. A locally orthogonal polygonal grid, derived from the associated Voronoi diagram, is computed as the staggered dual. It is shown that use of the Frontal-Delaunay refinement technique allows for the generation of very high-quality unstructured triangulations, satisfying a priori bounds on element size and shape. Grid quality is further improved through the application of hill-climbing-type optimisation techniques. Overall, the algorithm is shown to produce grids with very high element quality and smooth grading characteristics, while imposing relatively low computational expense. A selection of uniform and non-uniform spheroidal grids appropriate for high-resolution, multi-scale general circulation modelling are presented. These grids are shown to satisfy the geometric constraints associated with contemporary unstructured C-grid-type finite-volume models, including the Model for Prediction Across Scales (MPAS-O. The use of user-defined mesh-spacing functions to generate smoothly graded, non-uniform grids for multi-resolution-type studies is discussed in detail.

  16. A nested Atlantic-Mediterranean Sea general circulation model for operational forecasting

    Directory of Open Access Journals (Sweden)

    P. Oddo

    2009-10-01

    Full Text Available A new numerical general circulation ocean model for the Mediterranean Sea has been implemented nested within an Atlantic general circulation model within the framework of the Marine Environment and Security for the European Area project (MERSEA, Desaubies, 2006. A 4-year twin experiment was carried out from January 2004 to December 2007 with two different models to evaluate the impact on the Mediterranean Sea circulation of open lateral boundary conditions in the Atlantic Ocean. One model considers a closed lateral boundary in a large Atlantic box and the other is nested in the same box in a global ocean circulation model. Impact was observed comparing the two simulations with independent observations: ARGO for temperature and salinity profiles and tide gauges and along-track satellite observations for the sea surface height. The improvement in the nested Atlantic-Mediterranean model with respect to the closed one is particularly evident in the salinity characteristics of the Modified Atlantic Water and in the Mediterranean sea level seasonal variability.

  17. Characteristics of Atmospheric Circulation and Hydrologic Cycle over the North Pacific on Sub-seasonal Timescale

    Science.gov (United States)

    Ren, X.

    2016-12-01

    The air-sea system over the North Pacific region has multi-scale processes. Among them, the sub-seasonal timescale process has attracted literature due to its close linkage with persistent cold event or heavy rainfall event over east Asia and North American. In this study, we focused on the atmospheric circulation and hydrologic cycle over the North Pacific on sub-seasonal timescale. The EOF results showed that, there are two dominant modes of latent heat fluxes (evaporation) anomaly over the North Pacific ocean region on sub-seasonal timescale. The first mode exhibits an above normal/below normal latent heat release along the East Asian coastal region between 10º-45ºN, and below normal/above one to the east side. The first modes propagates downstream like the wave-train. The second mode shows a see-saw pattern, with positive anomaly over the Kuroshio and its extending region and negative one over the Northeast Pacific. It is seen that the associated anomalies in integrated vapor transport (IVT) and precipitation exhibit opposite sign with the anomaly in evaporation: increased/decreased evaporation from the ocean to the air is linkage with decreased/increased IVT and precipitation locally. Additionally, for the second mode, the increased IVT extends to the northwest part of the North America. The precipitation along the North American northwest coast increase significantly. The influences of the first mode is mainly located over the northwest Pacific and fades to the east of the dateline. The driver of the first mode is the southeastward propagation of a wave train across Eurasian mid and high latitudes. The invasion of the wave train into the northwest Pacific contributes to the first mode of latent heat anomaly over the North Pacific ocean region. The driver of the second mode is the intensified/weakened Aleutian low. When the Aleutian low is intensified on sub-seasonal timescale, the increased wind speed and colder air temperature induce above

  18. Multi-temporal clustering of continental floods and associated atmospheric circulations

    Science.gov (United States)

    Liu, Jianyu; Zhang, Yongqiang

    2017-12-01

    Investigating clustering of floods has important social, economic and ecological implications. This study examines the clustering of Australian floods at different temporal scales and its possible physical mechanisms. Flood series with different severities are obtained by peaks-over-threshold (POT) sampling in four flood thresholds. At intra-annual scale, Cox regression and monthly frequency methods are used to examine whether and when the flood clustering exists, respectively. At inter-annual scale, dispersion indices with four-time variation windows are applied to investigate the inter-annual flood clustering and its variation. Furthermore, the Kernel occurrence rate estimate and bootstrap resampling methods are used to identify flood-rich/flood-poor periods. Finally, seasonal variation of horizontal wind at 850 hPa and vertical wind velocity at 500 hPa are used to investigate the possible mechanisms causing the temporal flood clustering. Our results show that: (1) flood occurrences exhibit clustering at intra-annual scale, which are regulated by climate indices representing the impacts of the Pacific and Indian Oceans; (2) the flood-rich months occur from January to March over northern Australia, and from July to September over southwestern and southeastern Australia; (3) stronger inter-annual clustering takes place across southern Australia than northern Australia; and (4) Australian floods are characterised by regional flood-rich and flood-poor periods, with 1987-1992 identified as the flood-rich period across southern Australia, but the flood-poor period across northern Australia, and 2001-2006 being the flood-poor period across most regions of Australia. The intra-annual and inter-annual clustering and temporal variation of flood occurrences are in accordance with the variation of atmospheric circulation. These results provide relevant information for flood management under the influence of climate variability, and, therefore, are helpful for developing

  19. Characteristics of atmospheric circulation over East Asia associated with summer blocking

    Science.gov (United States)

    Park, Yong-Jun; Ahn, Joong-Bae

    2014-01-01

    The boreal summer-blocking regions were defined using the reanalysis data over the three decades of 1981-2010, and the influence of the blocking on atmospheric circulation in East Asia was examined. The summer blocking occurred mostly in North Europe, Ural region, Sea of Okhotsk (OK), and northeastern Pacific. The summer blocking was the major mode in these four regions according to principal component analysis using 500 hPa geopotential heights. Among the four blocking regions, OK blocking frequencies (OK BFs) showed negative and positive correlations with summer temperature and precipitation of Northeast Asia centered around the East Sea/Sea of Japan, respectively. In particular, the OK BF had a statistically significant correlation coefficient of -0.54 with summer temperatures in the Korean Peninsula. This indicates that the summer temperature and precipitation in this region were closely related to the OK blocking. According to the composite analysis for the years of higher-than-average BF (positive BF years), the OK High became stronger and expanded, while the North Pacific High was weakened over the Korean Peninsula and Japan and an anomalously deep trough was developed in the upper layer (200 hPa). As the cool OK High expanded, the temperature decreased over Northeast Asia centered around the East Sea/Sea of Japan and the lower level (850 hPa) air converged cyclonically, resulting in the increased precipitation, which induced the divergence in the upper layer and thereby strengthened the jet stream. Thus, the boreal summer OK blocking systematically influencing the area as the most dominant mode.

  20. The Mars Dust Cycle: Investigating the Effects of Radiatively Active Water Ice Clouds on Surface Stresses and Dust Lifting Potential with the NASA Ames Mars General Circulation Model

    Science.gov (United States)

    Kahre, Melinda A.; Hollingsworth, Jeffery

    2012-01-01

    The dust cycle is a critically important component of Mars' current climate system. Dust is present in the atmosphere of Mars year-round but the dust loading varies with season in a generally repeatable manner. Dust has a significant influence on the thermal structure of the atmosphere and thus greatly affects atmospheric circulation. The dust cycle is the most difficult of the three climate cycles (CO2, water, and dust) to model realistically with general circulation models. Until recently, numerical modeling investigations of the dust cycle have typically not included the effects of couplings to the water cycle through cloud formation. In the Martian atmosphere, dust particles likely provide the seed nuclei for heterogeneous nucleation of water ice clouds. As ice coats atmospheric dust grains, the newly formed cloud particles exhibit different physical and radiative characteristics. Thus, the coupling between the dust and water cycles likely affects the distributions of dust, water vapor and water ice, and thus atmospheric heating and cooling and the resulting circulations. We use the NASA Ames Mars GCM to investigate the effects of radiatively active water ice clouds on surface stress and the potential for dust lifting. The model includes a state-of-the-art water ice cloud microphysics package and a radiative transfer scheme that accounts for the radiative effects of CO2 gas, dust, and water ice clouds. We focus on simulations that are radiatively forced by a prescribed dust map, and we compare simulations that do and do not include radiatively active clouds. Preliminary results suggest that the magnitude and spatial patterns of surface stress (and thus dust lifting potential) are substantial influenced by the radiative effects of water ice clouds.

  1. Atmospheric circulation influence on the interannual variability of snow pack in the Centre Asian Moutains during 1959-2008

    Science.gov (United States)

    Cui, C.; Wei, Rongqing; Yang, Qing

    2009-04-01

    Large areas in the Chinese Tianshans and Altays are covered by snow between December and April. A significant positive trend in these two moutains snow pack was detected during the past half century. This paper analyses the interannual variation of snow accumulation in these mountains in relation to the variability of atmospheric circulation. Two spatial scales, from weather types over the centre Asian to hemispheric atmospheric patterns were considered. The results show strong relationships between the annual occurrence of several weather types and winter snow accumulation. Changes in the frequency of several weather types are explained by the evolution of large scale hemispheric circulation patterns, especially the North Atlantic Oscillation (NAO) and the Western Wind Index(WWI). Thus, the positive trend observed in the NAO index and WWI leads to an increase in the occurrence of types that favour snow accumulation and a decrease in unfavourable conditions for snow pack during the last half of the 20th century.

  2. Response of the Atlantic Thermohaline Circulation to Increased Atmospheric CO2 in a Coupled Model.

    Science.gov (United States)

    Hu, Aixue; Meehl, Gerald A.; Washington, Warren M.; Dai, Aiguo

    2004-11-01

    Changes in the thermohaline circulation (THC) due to increased CO2 are important in future climate regimes. Using a coupled climate model, the Parallel Climate Model (PCM), regional responses of the THC in the North Atlantic to increased CO2 and the underlying physical processes are studied here. The Atlantic THC shows a 20-yr cycle in the control run, qualitatively agreeing with other modeling results. Compared with the control run, the simulated maximum of the Atlantic THC weakens by about 5 Sv (1 Sv 106 m3 s-1) or 14% in an ensemble of transient experiments with a 1% CO2 increase per year at the time of CO2 doubling. The weakening of the THC is accompanied by reduced poleward heat transport in the midlatitude North Atlantic. Analyses show that oceanic deep convective activity strengthens significantly in the Greenland Iceland Norway (GIN) Seas owing to a saltier (denser) upper ocean, but weakens in the Labrador Sea due to a fresher (lighter) upper ocean and in the south of the Denmark Strait region (SDSR) because of surface warming. The saltiness of the GIN Seas are mainly caused by an increased salty North Atlantic inflow, and reduced sea ice volume fluxes from the Arctic into this region. The warmer SDSR is induced by a reduced heat loss to the atmosphere, and a reduced sea ice flux into this region, resulting in less heat being used to melt ice. Thus, sea ice related salinity effects appear to be more important in the GIN Seas, but sea ice melt-related thermal effects seem to be more important in the SDSR region. On the other hand, the fresher Labrador Sea is mainly attributed to increased precipitation. These regional changes produce the overall weakening of the THC in the Labrador Sea and SDSR, and more vigorous ocean overturning in the GIN Seas. The northward heat transport south of 60°N is reduced with increased CO2, but increased north of 60°N due to the increased flow of North Atlantic water across this latitude.

  3. Precipitation extremes in the wettest Mediterranean region (Krivošije) and associated atmospheric circulation types

    National Research Council Canada - National Science Library

    Ducić, V; Luković, J; Burić, D; Stanojević, G; Mustafić, S

    2012-01-01

    .... The results suggest that the number of days with precipitation decreased. To analyse the relationship between extreme precipitation events and circulation types we have used an efficiency coefficient (E c...

  4. AnaWEGE: a weather generator based on analogues of atmospheric circulation

    OpenAIRE

    Yiou, P.

    2014-01-01

    This paper presents a stochastic weather generator based on analogues of circulation (AnaWEGE). Analogues of circulation have been a promising paradigm to analyse climate variability and its extremes. The weather generator uses precomputed analogues of sea-level pressure over the North Atlantic. The stochastic rules of the generator constrain the continuity in time of the simulations. The generator then simulates spatially coherent time series of a climate variable, drawn fr...

  5. The influence of persistence of atmospheric circulation on temperature anomalies revisited

    Science.gov (United States)

    Cahynova, Monika; Huth, Radan

    2010-05-01

    In this study we focus on the effect of persistence of circulation types on the occurrence of high and low temperatures in summer and winter, respectively, at several stations in Central Europe in the second half of the 20th century. The key question is to compare the subjective Hess-Brezowsky catalogue with its "objectivized" version, because serious concern has arisen on the credibility of the mid-1980s enhancement of persistence of the Hess-Brezowsky circulation types. For a direct comparison we have chosen an objective (automated) circulation catalogue that is based on the definition of Hess-Brezowsky types, and that also reproduces the minimum 3-day duration of circulation types. In this catalogue there is no significant upward trend in the persistence of types. We identify "hot" and "cold" circulation types and examine if there is a trend within these types, either in their frequency or temperature severity. We then determine whether the persistence of circulation types plays a role in these trends, e.g. whether the warming of "hot" types is caused rather by their longer duration or by the overall rise of their extremeness. The research is conducted within the COST733 Action "Harmonisation and Applications of Weather Types Classifications for European Regions". The Czech participation in it is supported by the Ministry of Education, Youth, and Sports of the Czech Republic, contract OC115.

  6. Effect of the large-scale atmospheric circulation on the variability of the Arctic Ocean freshwater export

    Energy Technology Data Exchange (ETDEWEB)

    Jahn, Alexandra; Mysak, Lawrence A. [McGill University, Department of Atmospheric and Oceanic Sciences, Montreal, QC (Canada); Tremblay, Bruno [McGill University, Department of Atmospheric and Oceanic Sciences, Montreal, QC (Canada); Columbia University of New York, Lamont-Doherty Earth Observatory, Palisades, NY (United States); Newton, Robert [Columbia University of New York, Lamont-Doherty Earth Observatory, Palisades, NY (United States)

    2010-02-15

    Freshwater (FW) leaves the Arctic Ocean through sea-ice export and the outflow of low-salinity upper ocean water. Whereas the variability of the sea-ice export is known to be mainly caused by changes in the local wind and the thickness of the exported sea ice, the mechanisms that regulate the variability of the liquid FW export are still under investigation. To better understand these mechanisms, we present an analysis of the variability of the liquid FW export from the Arctic Ocean for the period 1950-2007, using a simulation from an energy and mass conserving global ocean-sea ice model, coupled to an Energy Moisture Balance Model of the atmosphere, and forced with daily winds from the NCEP reanalysis. Our results show that the simulated liquid FW exports through the Canadian Arctic Archipelago (CAA) and the Fram Strait lag changes in the large-scale atmospheric circulation over the Arctic by 1 and 6 years, respectively. The variability of the liquid FW exports is caused by changes in the cyclonicity of the atmospheric forcing, which cause a FW redistribution in the Arctic through changes in Ekman transport in the Beaufort Gyre. This in turn causes changes in the sea surface height (SSH) and salinity upstream of the CAA and Fram Strait, which affect the velocity and salinity of the outflow. The SSH changes induced by the large-scale atmospheric circulation are found to explain a large part of the variance of the liquid FW export, while the local wind plays a much smaller role. We also show that during periods of increased liquid FW export from the Arctic, the strength of the simulated Atlantic meridional overturning circulation is reduced and the ocean heat transport into the Arctic is increased. These results are particularly relevant in the context of global warming, as climate simulations predict an increase in the liquid FW export from the Arctic during the twenty-first century. (orig.)

  7. Relationships between atmospheric circulation indices and rainfall in Northern Algeria and comparison of observed and RCM-generated rainfall

    Science.gov (United States)

    Taibi, S.; Meddi, M.; Mahé, G.; Assani, A.

    2017-01-01

    This work aims, as a first step, to analyze rainfall variability in Northern Algeria, in particular extreme events, during the period from 1940 to 2010. Analysis of annual rainfall shows that stations in the northwest record a significant decrease in rainfall since the 1970s. Frequencies of rainy days for each percentile (5th, 10th, 25th, 50th, 75th, 90th, 95th, and 99th) and each rainfall interval class (1-5, 5-10, 10-20, 20-50, and ≥50 mm) do not show a significant change in the evolution of daily rainfall. The Tenes station is the only one to show a significant decrease in the frequency of rainy days up to the 75th percentile and for the 10-20-mm interval class. There is no significant change in the temporal evolution of extreme events in the 90th, 95th, and 99th percentiles. The relationships between rainfall variability and general atmospheric circulation indices for interannual and extreme event variability are moderately influenced by the El Niño-Southern Oscillation and Mediterranean Oscillation. Significant correlations are observed between the Southern Oscillation Index and annual rainfall in the northwestern part of the study area, which is likely linked with the decrease in rainfall in this region. Seasonal rainfall in Northern Algeria is affected by the Mediterranean Oscillation and North Atlantic Oscillation in the west. The ENSEMBLES regional climate models (RCMs) are assessed using the bias method to test their ability to reproduce rainfall variability at different time scales. The Centre National de Recherches Météorologiques (CNRM), Czech Hydrometeorological Institute (CHMI), Eidgenössische Technische Hochschule Zürich (ETHZ), and Forschungszentrum Geesthacht (GKSS) models yield the least biased results.

  8. Surface-layer turbulence, energy balance and links to atmospheric circulations over a mountain glacier in the French Alps

    Science.gov (United States)

    Litt, Maxime; Sicart, Jean-Emmanuel; Six, Delphine; Wagnon, Patrick; Helgason, Warren D.

    2017-04-01

    Over Saint-Sorlin Glacier in the French Alps (45° N, 6.1° E; ˜ 3 km2) in summer, we study the atmospheric surface-layer dynamics, turbulent fluxes, their uncertainties and their impact on surface energy balance (SEB) melt estimates. Results are classified with regard to large-scale forcing. We use high-frequency eddy-covariance data and mean air-temperature and wind-speed vertical profiles, collected in 2006 and 2009 in the glacier's atmospheric surface layer. We evaluate the turbulent fluxes with the eddy-covariance (sonic) and the profile method, and random errors and parametric uncertainties are evaluated by including different stability corrections and assuming different values for surface roughness lengths. For weak synoptic forcing, local thermal effects dominate the wind circulation. On the glacier, weak katabatic flows with a wind-speed maximum at low height (2-3 m) are detected 71 % of the time and are generally associated with small turbulent kinetic energy (TKE) and small net turbulent fluxes. Radiative fluxes dominate the SEB. When the large-scale forcing is strong, the wind in the valley aligns with the glacier flow, intense downslope flows are observed, no wind-speed maximum is visible below 5 m, and TKE and net turbulent fluxes are often intense. The net turbulent fluxes contribute significantly to the SEB. The surface-layer turbulence production is probably not at equilibrium with dissipation because of interactions of large-scale orographic disturbances with the flow when the forcing is strong or low-frequency oscillations of the katabatic flow when the forcing is weak. In weak forcing when TKE is low, all turbulent fluxes calculation methods provide similar fluxes. In strong forcing when TKE is large, the choice of roughness lengths impacts strongly the net turbulent fluxes from the profile method fluxes and their uncertainties. However, the uncertainty on the total SEB remains too high with regard to the net observed melt to be able to

  9. Impact of tropical Atlantic sea-surface temperature biases on the simulated atmospheric circulation and precipitation over the Atlantic region: An ECHAM6 model study

    Science.gov (United States)

    Eichhorn, Astrid; Bader, Jürgen

    2017-09-01

    As many coupled atmosphere-ocean general circulation models, the coupled Earth System Model developed at the Max Planck Institute for Meteorology suffers from severe sea-surface temperature (SST) biases in the tropical Atlantic. We performed a set of SST sensitivity experiments with its atmospheric model component ECHAM6 to understand the impact of tropical Atlantic SST biases on atmospheric circulation and precipitation. The model was forced by a climatology of observed global SSTs to focus on simulated seasonal and annual mean state climate. Through the superposition of varying tropical Atlantic bias patterns extracted from the MPI-ESM on top of the control field, this study investigates the relevance of the seasonal variation and spatial structure of tropical Atlantic biases for the simulated response. Results show that the position and structure of the Intertropical Convergence Zone (ITCZ) across the Atlantic is significantly affected, exhibiting a dynamically forced shift of annual mean precipitation maximum to the east of the Atlantic basin as well as a southward shift of the oceanic rain belt. The SST-induced changes in the ITCZ in turn affect seasonal rainfall over adjacent continents. However not only the ITCZ position but also other effects arising from biases in tropical Atlantic SSTs, e.g. variations in the wind field, change the simulation of precipitation over land. The seasonal variation and spatial pattern of tropical Atlantic SST biases turns out to be crucial for the simulated atmospheric response and is essential for analyzing the contribution of SST biases to coupled model mean state biases. Our experiments show that MPI-ESM mean-state biases in the Atlantic sector are mainly driven by SST biases in the tropical Atlantic while teleconnections from other basins seem to play a minor role.

  10. Winter to winter recurrence of atmospheric circulation anomalies over East Asia and its impact on winter surface air temperature anomalies.

    Science.gov (United States)

    Zhao, Xia; Yang, Guang

    2017-01-01

    The persistence of atmospheric circulation anomalies over East Asia shows a winter to winter recurrence (WTWR) phenomenon. Seasonal variations in sea level pressure anomalies and surface wind anomalies display significantly different characteristics between WTWR and non-WTWR years. The WTWR years are characterized by the recurrence of both a strong (weak) anomalous Siberian High and an East Asian winter monsoon over two successive winters without persistence through the intervening summer. However, anomalies during the non-WTWR years have the opposite sign between the current and ensuing winters. The WTWR of circulation anomalies contributes to that of surface air temperature anomalies (SATAs), which is useful information for improving seasonal and interannual climate predictions over East Asia and China. In the positive (negative) WTWR years, SATAs are cooler (warmer) over East Asia in two successive winters, but the signs of the SATAs are opposite in the preceding and subsequent winters during the non-WTWR years.

  11. Evolving Impacts of Multiyear La Niña Events on Atmospheric Circulation and U.S. Drought

    Science.gov (United States)

    Okumura, Yuko M.; DiNezio, Pedro; Deser, Clara

    2017-11-01

    Wintertime precipitation over the southern U.S. is known to decrease with interannual cooling of the equatorial Pacific associated with La Niña, which often persists 2 years or longer. Composite analysis based on a suite of observational and reanalysis data sets covering the period 1901-2012 reveals distinct evolution of atmospheric teleconnections and U.S. precipitation anomalies during multiyear La Niña events. In particular, atmospheric circulation anomalies strengthen and become more zonally elongated over the North Pacific in the second winter compared to the first winter. U.S. precipitation deficits also remain large, while the region of reduced precipitation shifts northeastward in the second winter. This occurs despite a significant weakening of the equatorial Pacific cooling in the second winter and suggests that the large-scale atmospheric circulation is more sensitive to tropical sea surface temperature anomalies of broader meridional extent. Given the extended climatic impacts, accurate prediction of La Niña duration is crucial.

  12. Multi-model assessment of linkages between eastern Arctic sea-ice variability and the Euro-Atlantic atmospheric circulation in current climate

    Science.gov (United States)

    García-Serrano, J.; Frankignoul, C.; King, M. P.; Arribas, A.; Gao, Y.; Guemas, V.; Matei, D.; Msadek, R.; Park, W.; Sanchez-Gomez, E.

    2017-10-01

    A set of ensemble integrations from the Coupled Model Intercomparison Project phase 5, with historical forcing plus RCP4.5 scenario, are used to explore if state-of-the-art climate models are able to simulate previously reported linkages between sea-ice concentration (SIC) anomalies over the eastern Arctic, namely in the Greenland-Barents-Kara Seas, and lagged atmospheric circulation that projects on the North Atlantic Oscillation (NAO)/Arctic Oscillation (AO). The study is focused on variability around the long-term trends, so that all anomalies are detrended prior to analysis; the period of study is 1979-2013. The model linkages are detected by applying maximum covariance analysis. As also found in observational data, all the models considered here show a statistically significant link with sea-ice reduction over the eastern Arctic followed by a negative NAO/AO-like pattern. If the simulated relationship is found at a lag of one month, the results suggest that a stratospheric pathway could be at play as the driving mechanism; in observations this is preferentially shown for SIC in November. The interference of a wave-like anomaly over Eurasia, accompanying SIC changes, with the climatological wave pattern appears to be key in setting the mediating role of the stratosphere. On the other hand, if the simulated relationship is found at a lag of two months, the results suggest that tropospheric dynamics are dominant, presumably due to transient eddy feedback; in observations this is preferentially shown for SIC in December. The results shown here and previous evidence from atmosphere-only experiments emphasize that there could be a detectable influence of eastern Arctic SIC variability on mid-latitude atmospheric circulation anomalies. Even if the mechanisms are robust among the models, the timing of the simulated linkages strongly depends on the model and does not generally mimic the observational ones. This implies that the atmospheric sensitivity to sea

  13. Impacts of large-scale atmospheric circulation changes in winter on black carbon transport and deposition to the Arctic

    Directory of Open Access Journals (Sweden)

    L. Pozzoli

    2017-10-01

    Full Text Available Winter warming and sea-ice retreat observed in the Arctic in the last decades may be related to changes of large-scale atmospheric circulation pattern, which may impact the transport of black carbon (BC to the Arctic and its deposition on the sea ice, with possible feedbacks on the regional and global climate forcing. In this study we developed and applied a statistical algorithm, based on the maximum likelihood estimate approach, to determine how the changes of three large-scale weather patterns associated with increasing temperatures in winter and sea-ice retreat in the Arctic impact the transport of BC to the Arctic and its deposition. We found that two atmospheric patterns together determine a decreasing winter deposition trend of BC between 1980 and 2015 in the eastern Arctic while they increase BC deposition in the western Arctic. The increasing BC trend is mainly due to a pattern characterized by a high-pressure anomaly near Scandinavia favouring the transport in the lower troposphere of BC from Europe and North Atlantic directly into to the Arctic. Another pattern with a high-pressure anomaly over the Arctic and low-pressure anomaly over the North Atlantic Ocean has a smaller impact on BC deposition but determines an increasing BC atmospheric load over the entire Arctic Ocean with increasing BC concentrations in the upper troposphere. The results show that changes in atmospheric circulation due to polar atmospheric warming and reduced winter sea ice significantly impacted BC transport and deposition. The anthropogenic emission reductions applied in the last decades were, therefore, crucial to counterbalance the most likely trend of increasing BC pollution in the Arctic.

  14. Impacts of large-scale atmospheric circulation changes in winter on black carbon transport and deposition to the Arctic

    Science.gov (United States)

    Pozzoli, Luca; Dobricic, Srdan; Russo, Simone; Vignati, Elisabetta

    2017-10-01

    Winter warming and sea-ice retreat observed in the Arctic in the last decades may be related to changes of large-scale atmospheric circulation pattern, which may impact the transport of black carbon (BC) to the Arctic and its deposition on the sea ice, with possible feedbacks on the regional and global climate forcing. In this study we developed and applied a statistical algorithm, based on the maximum likelihood estimate approach, to determine how the changes of three large-scale weather patterns associated with increasing temperatures in winter and sea-ice retreat in the Arctic impact the transport of BC to the Arctic and its deposition. We found that two atmospheric patterns together determine a decreasing winter deposition trend of BC between 1980 and 2015 in the eastern Arctic while they increase BC deposition in the western Arctic. The increasing BC trend is mainly due to a pattern characterized by a high-pressure anomaly near Scandinavia favouring the transport in the lower troposphere of BC from Europe and North Atlantic directly into to the Arctic. Another pattern with a high-pressure anomaly over the Arctic and low-pressure anomaly over the North Atlantic Ocean has a smaller impact on BC deposition but determines an increasing BC atmospheric load over the entire Arctic Ocean with increasing BC concentrations in the upper troposphere. The results show that changes in atmospheric circulation due to polar atmospheric warming and reduced winter sea ice significantly impacted BC transport and deposition. The anthropogenic emission reductions applied in the last decades were, therefore, crucial to counterbalance the most likely trend of increasing BC pollution in the Arctic.

  15. Chlorophyll modulation of sea surface temperature in the Arabian Sea in a mixed-layer isopycnal general circulation model

    Digital Repository Service at National Institute of Oceanography (India)

    Nakamoto, S.; PrasannaKumar, S.; Muneyama, K.; Frouin, R.

    , embedded in the ocean isopycnal general circulation model (OPYC). A higher abundance of chlorophyll in October than in April in the Arabian Sea increases absorption of solar irradiance and heating rate in the upper ocean, resulting in decreasing the mixed...

  16. River-flow predictions for the South African mid-summer using a coupled general circulation model

    CSIR Research Space (South Africa)

    Olivier, C

    2013-09-01

    Full Text Available demonstrates the seasonal-to-interannual predictability of river-flow over the summer rainfall areas of South Africa by using various fields from a coupled general circulation model as predictors in statistical post-processing system....

  17. Karakoram temperature and glacial melt driven by regional atmospheric circulation variability

    Science.gov (United States)

    Forsythe, Nathan; Fowler, Hayley J.; Li, Xiao-Feng; Blenkinsop, Stephen; Pritchard, David

    2017-09-01

    Identifying mechanisms driving spatially heterogeneous glacial mass-balance patterns in the Himalaya, including the `Karakoram anomaly', is crucial for understanding regional water resource trajectories. Streamflows dependent on glacial meltwater are strongly positively correlated with Karakoram summer air temperatures, which show recent anomalous cooling. We explain these temperature and streamflow anomalies through a circulation system--the Karakoram vortex--identified using a regional circulation metric that quantifies the relative position and intensity of the westerly jet. Winter temperature responses to this metric are homogeneous across South Asia, but the Karakoram summer response diverges from the rest of the Himalaya. We show that this is due to seasonal contraction of the Karakoram vortex through its interaction with the South Asian monsoon. We conclude that interannual variability in the Karakoram vortex, quantified by our circulation metric, explains the variability in energy-constrained ablation manifested in river flows across the Himalaya, with important implications for Himalayan glaciers' futures.

  18. Atmospheric circulation leading to record breaking precipitation and floods in southern Iberia in December 1876

    Science.gov (United States)

    Trigo, R. M.; Varino, F.; Vaquero, J.; Valente, M. A.

    2012-04-01

    The first week of December 1876 was marked by extreme weather conditions that affected the south-western sector of the Iberian Peninsula (IP), leading to an all-time record flow in both large international rivers running from Spain to Portugal, Tagus and Guadiana. As a direct consequence, several towns in centre and south IP suffered serious flood damage. These catastrophic floods were amplified by the occurrence of anomalously wet October and November months, as shown by recently digitised time series for both IP countries. These events resulted from the continuous pouring of precipitation registered between 29 November and 7 December, due to the consecutive Atlantic low-pressure systems and their associated frontal systems that reached the Iberian Peninsula. Using several different data sources, such as historical newspapers of that time, meteorological data recently digitised from several stations in Portugal and Spain and the recently available 20th Century Reanalysis (Compo et al., 2011), we were able (135 years afterwards), to study in detail the damage and the atmospheric circulation conditions associated with this event. The synoptic conditions were represented by 6 hourly fields of complementary variables, namely; 1) precipitation rate and mean sea level pressure (SLP); 2) precipitation rate and CAPE; 3) wind speed intensity and divergence at 250 hPa, 4) wind speed intensity and divergence also at 850 hPa; 5) air temperature at 850 hPa and geopotential height at 500 hPa; 6) wind speed barbs and specific moisture content at 850 hPa. Movies with all these variables were obtained for the 10-day sequence that spans between 29 November and 7 December. For two recently digitised stations in Portugal (Lisbon and Évora), the values of precipitation registered during those weeks were so remarkable that when we computed daily accumulated precipitation successively from 1 to 10 days, the episode of 1876 always stood as the maximum precipitation event, with the

  19. Twentieth-century atmospheric river activity along the west coasts of Europe and North America: algorithm formulation, reanalysis uncertainty and links to atmospheric circulation patterns

    Science.gov (United States)

    Brands, S.; Gutiérrez, J. M.; San-Martín, D.

    2017-05-01

    A new atmospheric-river detection and tracking scheme based on the magnitude and direction of integrated water vapour transport is presented and applied separately over 13 regions located along the west coasts of Europe (including North Africa) and North America. Four distinct reanalyses are considered, two of which cover the entire twentieth-century: NOAA-CIRES Twentieth Century Reanalysis v2 (NOAA-20C) and ECMWF ERA-20C. Calculations are done separately for the OND and JFM-season and, for comparison with previous studies, for the ONDJFM-season as a whole. Comparing the AR-counts from NOAA-20C and ERA-20C with a running 31-year window looping through 1900-2010 reveals differences in the climatological mean and inter-annual variability which, at the start of the twentieth-century, are much more pronounced in western North America than in Europe. Correlating European AR-counts with the North Atlantic Oscillation (NAO) reveals a pattern reminiscent of the well-know precipitation dipole which is stable throughout the entire century. A similar analysis linking western North American AR-counts to the North Pacific index (NPI) is hampered by the aforementioned poor reanalysis agreement at the start of the century. During the second half of the twentieth-century, the strength of the NPI-link considerably varies with time in British Columbia and the Gulf of Alaska. Considering the period 1950-2010, AR-counts are then associated with other relevant large-scale circulation indices such as the East Atlantic, Scandinavian, Pacific-North American and West Pacific patterns (EA, SCAND, PNA and WP). Along the Atlantic coastline of the Iberian Peninsula and France, the EA-link is stronger than the NAO-link if the OND season is considered and the SCAND-link found in northern Europe is significant during both seasons. Along the west coast of North America, teleconnections are generally stronger during JFM in which case the NPI-link is significant in any of the five considered

  20. Numerical study of the effects of local atmospheric circulations on a pollution event over Beijing-Tianjin-Hebei, China.

    Science.gov (United States)

    Miao, Yucong; Liu, Shuhua; Zheng, Yijia; Wang, Shu; Chen, Bicheng; Zheng, Hui; Zhao, Jingchuan

    2015-04-01

    Currently, the Chinese central government is considering plans to build a trilateral economic sphere in the Bohai Bay area, including Beijing, Tianjin and Hebei (BTH), where haze pollution frequently occurs. To achieve sustainable development, it is necessary to understand the physical mechanism of the haze pollution there. Therefore, the pollutant transport mechanisms of a haze event over the BTH region from 23 to 24 September 2011 were studied using the Weather Research and Forecasting model and the FLEXible-PARTicle dispersion model to understand the effects of the local atmospheric circulations and atmospheric boundary layer structure. Results suggested that the penetration by sea-breeze could strengthen the vertical dispersion by lifting up the planetary boundary layer height (PBLH) and carry the local pollutants to the downstream areas; in the early night, two elevated pollution layers (EPLs) may be generated over the mountain areas: the pollutants in the upper EPL at the altitude of 2-2.5 km were favored to disperse by long-range transport, while the lower EPL at the altitude of 1 km may serve as a reservoir, and the pollutants there could be transported downward and contribute to the surface air pollution. The intensity of the sea-land and mountain-valley breeze circulations played an important role in the vertical transport and distribution of pollutants. It was also found that the diurnal evolution of the PBLH is important for the vertical dispersion of the pollutants, which is strongly affected by the local atmospheric circulations and the distribution of urban areas. Copyright © 2015. Published by Elsevier B.V.

  1. Circulating levels of fatty acid-binding protein family and metabolic phenotype in the general population.

    Directory of Open Access Journals (Sweden)

    Shutaro Ishimura

    Full Text Available OBJECTIVE: Fatty acid-binding proteins (FABPs are a family of 14-15-kDa proteins, and some FABPs have been to be used as biomarkers of tissue injury by leak from cells. However, recent studies have shown that FABPs can be secreted from cells into circulation. Here we examined determinants and roles of circulating FABPs in a general population. METHODS: From the database of the Tanno-Sobetsu Study, a study with a population-based cohort design, data in 2011 for 296 subjects on no medication were retrieved, and FABP1~5 in their serum samples were assayed. RESULTS: Level of FABP4, but not the other isoforms, showed a gender difference, being higher in females than in males. Levels of all FABPs were negatively correlated with estimated glomerular filtration rate (eGFR, but a distinct pattern of correlation with other clinical parameters was observed for each FABP isoform; significant correlates were alanine aminotransferase (ALT, blood pressure (BP, and brain natriuretic peptide (BNP for FABP1, none besides eGFR for FABP2, age, BP, and BNP for FABP3, age, waist circumference (WC, BP, BNP, lipid variables, high-sensitivity C-reactive protein (hsCRP, and HOMA-R for FABP4, and age, WC, BP, ALT, BNP, and HOMA-R for FABP5. FABP4 is the most strongly related to metabolic markers among FABPs. In a multivariate regression analysis, FABP4 level was an independent predictor of HOMA-R after adjustment of age, gender, WC, BP, HDL cholesterol, and hsCRP. CONCLUSIONS: Each FABP isoform level showed a distinct pattern of correlation with clinical parameters, although levels of all FABPs were negatively determined by renal function. Circulating FABP4 appears to be a useful biomarker for detecting pre-clinical stage of metabolic syndrome, especially insulin resistance, in the general population.

  2. The relationship between mixed Rossby-gravity waves and convection in a general circulation model

    Science.gov (United States)

    Hess, Peter G.; Hendon, Harry H.; Battisti, David S.

    1993-01-01

    We investigate the relationship between mixed Rossby-gravity waves (MRGWs) and convection in a general circulation model. The experiments described are performed in a general circulation model with the lower boundary set to that of an ocean surface everywhere. Several experiments are run varying the convective parameterization scheme (using either a modified Kuo scheme or a moist convective adjustment scheme) and varying the tropical sea surface temperatures (specified to be zonally symmetric in all cases), thereby changing the location of the modeled intertropical convergence zones (ITCZs). The appearance of a robust MRGW occurs when the sea surface temperature is such that two ITCZs straddle the equator. The particular sea surface temperature distribution used and the parameterization scheme for convection also affect the structure and strength of the modeled MRGW. The vertical structure of MRGWs is analyzed in the experiment in which this wave mode is the most energetic. We show that MRGWs of several different zonal length scales exist in the troposphere in association with convection; however, it is only the longer length scales which can be discerned in the upper troposphere and lower stratosphere.

  3. Simplifying a complex subject: some thoughts on teaching the general circulation

    Science.gov (United States)

    Grotjahn, Richard

    1998-01-01

    This issue is devoted to the many accomplishments of Dr Richard Pfeffer. His research is the focus of other articles in this issue. He has also been an instructor who both challenged and positively impressed students in his classes over several decades; for example, his general circulation class helped inspire a book on the subject by this author. So, his teaching is worthy of discussion and this unconventional article is intended to illustrate some aspects of his teaching style. This article has two main parts. First, the classroom environment 20 years ago (when the author was a student in Dr Pfeffer's classes) is sketched; it was different from today. Second, his homework and exam problems were lengthy, challenging, and integrated multiple concepts. Included are four problems; they are intended to be illustrative and to provide homework ideas for current instructors of general circulation subjects. For example, in a problem that estimates the energy release in an extratropical cyclone, a complementary calculation reveals whether baroclinic instability or latent release is the dominant growth mechanism.

  4. What are the most fire-dangerous atmospheric circulations in the Eastern-Mediterranean? Analysis of the synoptic wildfire climatology.

    Science.gov (United States)

    Paschalidou, A K; Kassomenos, P A

    2016-01-01

    Wildfire management is closely linked to robust forecasts of changes in wildfire risk related to meteorological conditions. This link can be bridged either through fire weather indices or through statistical techniques that directly relate atmospheric patterns to wildfire activity. In the present work the COST-733 classification schemes are applied in order to link wildfires in Greece with synoptic circulation patterns. The analysis reveals that the majority of wildfire events can be explained by a small number of specific synoptic circulations, hence reflecting the synoptic climatology of wildfires. All 8 classification schemes used, prove that the most fire-dangerous conditions in Greece are characterized by a combination of high atmospheric pressure systems located N to NW of Greece, coupled with lower pressures located over the very Eastern part of the Mediterranean, an atmospheric pressure pattern closely linked to the local Etesian winds over the Aegean Sea. During these events, the atmospheric pressure has been reported to be anomalously high, while anomalously low 500hPa geopotential heights and negative total water column anomalies were also observed. Among the various classification schemes used, the 2 Principal Component Analysis-based classifications, namely the PCT and the PXE, as well as the Leader Algorithm classification LND proved to be the best options, in terms of being capable to isolate the vast amount of fire events in a small number of classes with increased frequency of occurrence. It is estimated that these 3 schemes, in combination with medium-range to seasonal climate forecasts, could be used by wildfire risk managers to provide increased wildfire prediction accuracy. Copyright © 2015 Elsevier B.V. All rights reserved.

  5. Cyclones in the Mediterranean region: present and future climate scenarios derived from a general circulation model (HadAM3P

    Directory of Open Access Journals (Sweden)

    Chr. Anagnostopoulou

    2006-01-01

    Full Text Available In this paper, an attempt is made to assess and evaluate the skill of the Hadley Center atmospheric General Circulation Model (HadAM3P in generating successfully the frequency and intensity of severe cyclones (<1000 hPa in the Mediterranean region. The cyclonic occurrence is studied in three regions of enhanced cyclonic activity: Gulf of Genoa, Southern Italy and Cyprus. It was found that the HadAM3P predicts a future decrease of the frequency of the severe cyclones at the SLP level, but the future cyclones will be more intense (deeper, especially at the 500 hPa level.

  6. Variations of Younger Dryas atmospheric radiocarbon explicable without ocean circulation changes

    Science.gov (United States)

    Goslar; Arnold; Tisnerat-Laborde; Czernik; Wieckowski

    2000-02-24

    The concentration of radiocarbon, 14C, in the atmosphere depends on its production rate by cosmic rays, and on the intensity of carbon exchange between the atmosphere and other reservoirs, for example the deep oceans. For the Holocene (the past approximately 11,500 years), it has been shown that fluctuations in atmospheric radiocarbon concentrations have been caused mostly by variations in the solar magnetic field. Recent progress in extending the radiocarbon record backwards in time has indicated especially high atmospheric radiocarbon concentrations in the Younger Dryas cold period, between 12,700 and 11,500 years before the present. These high concentrations have been interpreted as a result of a reduced exchange with the deep-ocean reservoir, caused by a drastic weakening of the deep-ocean ventilation. Here we present a high-resolution reconstruction of atmospheric radiocarbon concentrations, derived from annually laminated sediments of two Polish lakes, Lake Gosciaz and Lake Perespilno. These records indicate that the maximum in atmospheric radiocarbon concentrations in the early Younger Dryas was smaller than previously believed, and might have been caused by variations in solar activity. If so, there is no indication that the deep-ocean ventilation in the Younger Dryas was significantly different from today's.

  7. Surface atmospheric circulation patterns and associated minimum temperatures in the Maipo and Casablanca valleys, central Chile

    Science.gov (United States)

    Montes, Carlo; Muñoz, Ricardo C.; Perez-Quezada, Jorge F.

    2013-01-01

    This paper analyzes the influence of circulation anomalies on the magnitude of minimum air temperature ( T min) at a daily scale in two important agricultural valleys of Chile (Maipo and Casablanca) during the period 2001-2007. A statistical classification of synoptic fields was performed, resulting in eight circulation patterns (CPs, 84 % of explained variance). The corresponding anomalies of T min (ATmin) of each CP were analyzed in order to understand their synoptic-scale forcing mechanisms. Results showed a direct association between ATmin and the synoptic structure. The average weakening in sea level pressure (SLP) yields positive ATmin, while negative ATmin is associated with a strengthening in SLP. In the latter case, it was also found that a synoptic structure (10.2 % of frequency) corresponding to a migratory high-pressure system passing eastward across the Andes led to the lowest ATmin and a higher probability of frost in both valleys (22 % on average) in winter and springtime.

  8. The influence of atmospheric circulation on the intensity of urban heat island and urban cold island in Poznań, Poland

    Science.gov (United States)

    Półrolniczak, Marek; Kolendowicz, Leszek; Majkowska, Agnieszka; Czernecki, Bartosz

    2017-02-01

    The study has analyzed influence of an atmospheric circulation on urban heat island (UHI) and urban cold island (UCI) in Poznań. Analysis was conducted on the basis of temperature data from two measurement points situated in the city center and in the Ławica airport (reference station) and the data concerning the air circulation (Niedźwiedź's calendar of circulation types and reanalysis of National Centers for Environmental Prediction (NCEP)/National Center for Atmospheric Research (NCAR)). The cases with UHI constitute about 85 % of all data, and UCI phenomena appear with a frequency of 14 % a year. The intensity of UHI phenomenon is higher in the anticyclonic circulation types. During the year in anticyclonic circulation, intensity of UHI is 1.2 °C on average while in cyclonic is only 0.8 °C. The occurring of UHI phenomena is possible throughout all seasons of the year in all hours of the day usually in anticyclonic circulation types. The cases with highest UHI intensity are related mostly to nighttime. The cases of UCI phenomena occurred almost ever on the daytime and the most frequently in colder part of the year together with cyclonic circulation. Study based on reanalysis data indicates that days with large intensity of UHI (above 4, 5, and 6 °C) are related to anticyclonic circulation. Anticyclonic circulation is also promoting the formation of the strongest UCI. Results based on both reanalysis and the atmospheric circulation data (Niedźwiedź's circulation type) confirm that cases with the strongest UHI and UCI during the same day occur in strong high-pressure system with the center situated above Poland or central Europe.

  9. Possible influence of atmospheric circulations on winter haze pollution in the Beijing–Tianjin–Hebei region, northern China

    Directory of Open Access Journals (Sweden)

    Z. Zhang

    2016-01-01

    Full Text Available Using the daily records derived from the synoptic weather stations and the NCEP/NCAR and ERA-Interim reanalysis data, the variability of the winter haze pollution (indicated by the mean visibility and number of hazy days in the Beijing–Tianjin–Hebei (BTH region during the period 1981 to 2015 and its relationship with the atmospheric circulations at middle–high latitude were analyzed in this study. The winter haze pollution in BTH had distinct inter-annual and inter-decadal variabilities without a significant long-term trend. According to the spatial distribution of correlation coefficients, six atmospheric circulation indices (I1 to I6 were defined from the key areas in sea level pressure (SLP, zonal and meridional winds at 850 hPa (U850, V850, geopotential height field at 500 hPa (H500, zonal wind at 200 hPa (U200, and air temperature at 200 hPa (T200, respectively. All of the six indices have significant and stable correlations with the winter visibility and number of hazy days in BTH. In the raw (unfiltered correlations, the correlation coefficients between the six indices and the winter visibility (number of hazy days varied from 0.57 (0.47 to 0.76 (0.6 with an average of 0.65 (0.54; in the high-frequency ( < 10 years correlations, the coefficients varied from 0.62 (0.58 to 0.8 (0.69 with an average of 0.69 (0.64. The six circulation indices together can explain 77.7 % (78.7 % and 61.7 % (69.1 % variances of the winter visibility and the number of hazy days in the year-to-year (inter-annual variability, respectively. The increase in Ic (a comprehensive index derived from the six individual circulation indices can cause a shallowing of the East Asian trough at the middle troposphere and a weakening of the Siberian high-pressure field at sea level, and is then accompanied by a reduction (increase of horizontal advection and vertical convection (relative humidity in the lowest troposphere and a reduced boundary layer

  10. A general circulation model study of the effects of faster rotation rate, enhanced CO2 concentration, and reduced solar forcing: Implications for the faint young sun paradox

    Science.gov (United States)

    Jenkins, Gregory S.

    1993-01-01

    Solar energy at the top of the atmosphere (solar constant), rotation rate, and carbon dioxide (CO2) may have varied significantly over Earth's history, especially during the earliest times. The sensitivity of a general circulation model to faster rotation, enhanced CO2 concentration, and reduced solar constant is presented. The control simulation of this study has a solar constant reduced by 10% the present amount, zero land fraction using a swamp ocean surface, CO2 concentrations of 330 ppmv, present-day rotation rate, and is integrated under mean diurnal and seasonal solar forcing. Four sensitivity test are performed under zero land fraction and reduced solar constant conditions by varying the earth's rotation rate atmospheric CO2 concentration and solar constant. The global mean sea surface temperatures (SSTs) compared to the control simulation: were 6.6 K to 12 K higher than the control's global mean temperature of 264.7 K. Sea ice is confined to higher latitudes in each experiment compared to the control, with ice-free areas equatorward of the subtropics. The warm SSTs are associated with a 20% reduction in clouds for the rotation rate experiments and higher CO2 concentrations in the other experiments. These results are in contrast to previous studies that have used energy balance and radiative convective models. Previous studies required a much larger atmospheric CO2 increase to prevent an ice-covered Earth. The results of the study, suggest that because of its possible feedback with clouds, the general circulation of the atmosphere should be taken into account in understanding the climate of early Earth. While higher CO2 concentrations are likely in view of the results, very large atmospheric CO2 concentrations may not be necessary to counterbalance the lower solar constant that existed early in Earth's history.

  11. Early Holocene Change in Atmospheric Circulation in the North-Central USA

    Science.gov (United States)

    Dean, W. E.

    2005-12-01

    Numerous proxies in cores from Elk Lake, northwestern Minnesota, have provided a record of climatic and environmental change with annual resolution for the last 10,000 years. The proxies that allow reconstruction of the lake's physical and chemical paleolimnology (diatoms, redox-sensitive trace metals, and 18O values) show that that prior to about 8.2 cal ka the lake was a stable, dimictic lake that was strongly stratified. The same proxies show that after 8.2 cal. ka the lake was turbulent, well-mixed and shallower. The proxies that are related to climate factors external to the lake (dust as % Al and % Si, varve thickness, and pollen) show that prior to 8.2 cal. ka the lake was receiving relatively little dust, implying little wind activity. After 8.2 cal ka, there was a marked increase in the influx of dust indicating an increase in westerly winds. Lastly, the ostracode faunal assemblages, which provide information about the limnology and watershed characteristics, indicate that, for 1000 years prior to 8.2 cal. ka, the lake was stable and dilute with characteristics typical of lakes in boreal forests. At 8.2 cal. ka, the ostracode assemblage abruptly shifted to an assemblage typical of Canadian prairie lakes that exhibit large seasonal variability in physical characteristics. This marks the northward displacement of the polar front and beginning of westerlies. The Elk Lake record further shows that the so-called 8.2 cal. yr cold event, recognized in ice-core and other records from the circum-North Atlantic, and thought by some to be caused by catastrophic drainage of freshwater from proglacial lakes Agassiz and Ojibway, was but a brief manifestation of a more fundamental and lasting change in the climate of North America. This fundamental climate change was the result of changes in atmospheric circulation in response to marked changes in the relative proportions of land, water, and, especially, glacial ice in North America during the early Holocene, the

  12. Anticyclonic atmospheric circulation as an analogue for the warm and dry mid-Holocene summer climate in central Scandinavia

    Directory of Open Access Journals (Sweden)

    K. Antonsson

    2008-10-01

    Full Text Available Climate reconstructions from central Scandinavia suggest that annual and summer temperatures were rising during the early Holocene and reached their maximum after 8000 cal yr BP. The period with highest temperatures was characterized by increasingly low lake-levels and dry climate, with driest and warmest conditions at about 7000 to 5000 cal yr BP. We compare the reconstructed climate pattern with simulations of a climate model for the last 9000 years and show that the model, which is predominantly driven by solar insolation patterns, suggests less prominent mid-Holocene dry and warm period in Scandinavia than the reconstructions. As an additional explanation for the reconstructed climate, we argue that the trend from the moist early Holocene towards dry and warm mid-Holocene was caused by a changing atmospheric circulation pattern with a mid-Holocene dominance of summer-time anticyclonic circulation. An extreme case of the anticyclonic conditions is the persistent blocking high, an atmospheric pressure pattern that at present often causes long spells of particularly dry and warm summer weather, or "Indian summers". The argument is tested with daily instrumental temperature and precipitation records in central Sweden and an objective circulation classification based on surface air pressure over the period 1900–2002. We conclude that the differences between the precipitation and temperature climates under anticyclonic and non-anticyclonic conditions are significant. Further, warm and dry combination, as indicated by mid-Holocene reconstructions, is a typical pattern under anticyclonic conditions. These results indicate that the presented hypothesis for the mid-Holocene climate is likely valid.

  13. An influence of extreme southern hemisphere cold surges on the North Atlantic Subtropical High through a shallow atmospheric circulation

    Science.gov (United States)

    Bowerman, A. R.; Fu, R.; Yin, L.; Fernando, D. N.; Arias, P. A.; Dickinson, R. E.

    2017-10-01

    Previous studies have attributed interhemisphere influences of the atmosphere to the latitudinal propagation of planetary waves crossing the equator, to the triggering of equatorial Kelvin waves, or to monsoonal circulation. Over the American-Atlantic sector, such cross-equatorial influences rarely occur during boreal summer due to unfavorable atmospheric conditions. We have observed that an alternative mechanism provides an interhemisphere influence. When episodes of extreme cold surges and upper tropospheric westerly winds occur concurrently over southern hemisphere Amazonia, cold surges from extratropical South America can penetrate deep into southern Amazonia. Although they do not appear to influence upper tropospheric circulation of the northern hemisphere, extremely strong southerly cross-equatorial advection (>2σ standard deviations, or 2) of cold and dense air in the lower troposphere can reach as least 10°N. Such cold advection increases the northward cross-equatorial pressure gradient in the lower to middle troposphere, thus shallow northerly return flow below 500 hPa. This return flow and the strong lower tropospheric southerly cross-equatorial flow form an anomalous shallow meridional circulation spanning from southern Amazonia to the subtropical North Atlantic, with increased geopotential height anomalies exceeding +1σ to at least 18°N. It projects onto the southern edge of the North Atlantic Subtropical High (NASH), increasing its pressure and leading to equatorward expansion of NASH's southern boundary. These anomalies enhance the NASH, leading to its equatorward expansion. These extreme cold surges can potentially improving the predictability of weather patterns of the tropical and subtropical Atlantic, including the variability of the NASH's southern edge.

  14. Circulating alpha1-antitrypsin in the general population: Determinants and association with lung function

    Directory of Open Access Journals (Sweden)

    Berger Wolfgang

    2008-04-01

    Full Text Available Abstract Background Severe alpha1-antitrypsin (AAT deficiency associated with low AAT blood concentrations is an established genetic COPD risk factor. Less is known about the respiratory health impact of variation in AAT serum concentrations in the general population. We cross-sectionally investigated correlates of circulating AAT concentrations and its association with FEV1. Methods In 5187 adults (2669 females with high-sensitive c-reactive protein (CRP levels ≤ 10 mg/l from the population-based Swiss SAPALDIA cohort, blood was collected at the time of follow-up examination for measuring serum AAT and CRP. Results Female gender, hormone intake, systolic blood pressure, age in men and in postmenopausal women, as well as active and passive smoking were positively, whereas alcohol intake and BMI inversely correlated with serum AAT levels, independent of CRP adjustment. We observed an inverse association of AAT with FEV1 in the total study population (p Conclusion The results of this population-based study reflect a complex interrelationship between tobacco exposure, gender related factors, circulating AAT, systemic inflammatory status and lung function.

  15. The ability of general circulation models to simulate tropical cyclones and their precursors over the North Atlantic main development region

    Energy Technology Data Exchange (ETDEWEB)

    Daloz, Anne Sophie; Chauvin, Fabrice [Groupe de Modelisation Grande Echelle et Climat, CNRM-GAME, Meteo-France, Toulouse Cedex 1 (France); Walsh, Kevin [University of Melbourne, School of Earth Sciences, Melbourne, VIC (Australia); Lavender, Sally; Abbs, Deborah [CSIRO Atmospheric and Marine Research, Aspendale, VIC (Australia); Roux, Frank [Universite de Toulouse and Centre National de la Recherche Scientifique, Laboratoire d' Aerologie, Toulouse (France)

    2012-10-15

    The ability of General Circulation Models (GCMs) to generate Tropical Cyclones (TCs) over the North Atlantic Main Development Region (MDR; 10-20 N, 20-80 W; Goldenberg and Shapiro in J Clim 9:1169-1187, 1996) is examined through a subset of ocean-atmosphere coupled simulations from the World Climate Research Programme (WCRP) Coupled Model Intercomparison Project phase 3 (CMIP3) multimodel data set and a high-resolution (0.5 ) Sea Surface Temperature (SST)-forced simulation from the Australian Conformal-Cubic Atmospheric Model GCM. The results are compared with National Center for Environmental Prediction (NCEP-2) and European Center for Medium Range Weather Forecasts Re-Analysis (ERA-40) reanalyses over a common period from 1980 to 1998. Important biases in the representation of the TC activity are encountered over the MDR. This study emphasizes the strong link in the GCMs between African Easterly Waves (AEWs) and TC activity in this region. However, the generation of AEWs is not a sufficient condition alone for the models to produce TCs. Precipitation over the Sahel, especially rainfall over the Fouta Djallon highlands (cf. Fig. 1), is playing a role in the generation of TCs over the MDR. The influence of large-scale fields such as SST, vertical wind shear and tropospheric humidity on TC genesis is also examined. The ability of TC genesis indices, such as the Genesis Potential Index and the Convective Yearly Genesis Potential, to represent TC activity over the MDR in simulations at low to high spatial resolutions is analysed. These indices are found to be a reasonable method for comparing cyclogenesis in different models, even though other factors such as AEW activity should also be considered. (orig.)

  16. Circulating Irisin Concentrations Are Associated with a Favourable Lipid Profile in the General Population.

    Directory of Open Access Journals (Sweden)

    Simon Oelmann

    Full Text Available Irisin is a myokine, which is mainly inversely associated with the risk for non-communicable diseases. Irisin improves cellular energy metabolism by uncoupling the mitochondrial respiratory chain resulting in increased energy expenditure using lipids. To date potential associations between irisin concentration and lipid profile are poorly understood. Therefore, this investigation aimed to evaluate potential associations between irisin and lipid levels in the general population.Data of 430 men and 537 women from the population-based Study of Health in Pomerania (SHIP-TREND with available irisin and lipid concentrations were used. Analyses of variance, linear and logistic regression models adjusted for age, HBA1c, waist circumference, physical activity, smoking, alcohol consumption, systolic blood pressure, ALAT were calculated.We detected significantly inverse associations between irisin and circulating levels of total [beta coefficient 0.21 (standard error 0.08, p = 0.01], low-density cholesterol [-0.16 (0.07, p = 0.03] and triglycerides [-0.17 (0.08, p = 0.02] for men. Females without lipid lowering medication had an inverse association between irisin and total cholesterol [-0.12 (0.06, p = 0.05]. Further, male subjects with irisin concentrations in the third tertile had an increased odds for elevated low-density cholesterol [odds ratio 1.96 (95% confidence interval 1.07-3.48, p = 0.03 and triglyceride [1.95 (1.09-3.47, p = 0.02] levels, even after exclusion of subjects with lipid lowering medication. In addition, our data revealed an annual rhythm of serum irisin levels with peak levels arise in winter and summer months.This is the first investigation to report a significant association between circulating irisin and a favourable lipid profile in the general population. This may infer that higher irisin concentrations are associated with a reduced risk for non-communicable diseases.

  17. Circulating Irisin Concentrations Are Associated with a Favourable Lipid Profile in the General Population.

    Science.gov (United States)

    Oelmann, Simon; Nauck, Matthias; Völzke, Henry; Bahls, Martin; Friedrich, Nele

    2016-01-01

    Irisin is a myokine, which is mainly inversely associated with the risk for non-communicable diseases. Irisin improves cellular energy metabolism by uncoupling the mitochondrial respiratory chain resulting in increased energy expenditure using lipids. To date potential associations between irisin concentration and lipid profile are poorly understood. Therefore, this investigation aimed to evaluate potential associations between irisin and lipid levels in the general population. Data of 430 men and 537 women from the population-based Study of Health in Pomerania (SHIP-TREND) with available irisin and lipid concentrations were used. Analyses of variance, linear and logistic regression models adjusted for age, HBA1c, waist circumference, physical activity, smoking, alcohol consumption, systolic blood pressure, ALAT were calculated. We detected significantly inverse associations between irisin and circulating levels of total [beta coefficient 0.21 (standard error 0.08), p = 0.01], low-density cholesterol [-0.16 (0.07), p = 0.03] and triglycerides [-0.17 (0.08), p = 0.02] for men. Females without lipid lowering medication had an inverse association between irisin and total cholesterol [-0.12 (0.06), p = 0.05]. Further, male subjects with irisin concentrations in the third tertile had an increased odds for elevated low-density cholesterol [odds ratio 1.96 (95% confidence interval 1.07-3.48), p = 0.03) and triglyceride [1.95 (1.09-3.47), p = 0.02] levels, even after exclusion of subjects with lipid lowering medication. In addition, our data revealed an annual rhythm of serum irisin levels with peak levels arise in winter and summer months. This is the first investigation to report a significant association between circulating irisin and a favourable lipid profile in the general population. This may infer that higher irisin concentrations are associated with a reduced risk for non-communicable diseases.

  18. Actual oxygen and suboxia representation: comparison of different ocean general circulation models

    Science.gov (United States)

    Duteil, O.; Oschlies, A.

    2010-12-01

    Oxygen is produced by photosynthesis in the light-lit surface waters, and quickly equilibrates with the atmosphere at the sea surface. In the ocean interior, oxygen is consumed during remineralization of organic matter exported from the euphotic surface and transported by ocean currents. Sluggish circulation combined with high export production lead to oxygen depletion and creation of suboxic regions. Although covering only a small fraction of the global ocean volume, these regions are of global biogeochemical significance, as they lead to a loss of fixed nitrogen from the ocean via denitrification and anaerobic ammonium oxidation (anammox). The mechanisms described above are reproduced in coupled biogeochemical - dynamical ocean models. We compare here oxygen and apparent oxygen utilization (AOU) distribution in 5 state-of-the-art models to observational data. Wide discrepancies, but also similar biases, are observed in term of suboxia extension and even mean oxygen content. These discrepancies are linked to the export production and also dynamical properties, such as overturning strength. The ratio of preformed over total nutrients has been computed to evaluate better relative impact of biological and physical pump in each case. Current study emphasizes the need of a better parameterization of oxygen compartment in ocean models.

  19. Comparison of the hydrological cycle in the general circulation model with 10 years SPICAM dataset

    Science.gov (United States)

    Shaposhnikov, D.; Rodin, A.; Medvedev, A. S.

    2016-12-01

    Water cycle plays a significant role in the Martian climate. Furthermore, water vapor can be a very sensitive marker of the transport processes, suitable for challenging 3D climate models. We present a new global circulation model developed in Max Planck Institute for Solar System Research (MPI-MGCM) also known as MAOAM (Martian Atmosphere: Observation and Modeling). The model has a spectral core and successfully predicts flows and temperatures through the use of physical parameterizations typical as well for terrestrial models as for the Martian ones. The hydrological block includes a realistictwo-moments microphysics, advection, and sedimentation according to the average particle size. The model successfully reproduces seasonal variations of water vapor and ice cloud distribution, in both latitude and longitude. More detailed matching of the water vapor geographical distribution shows discrete peaks in longitude during the aphelion season at Ls 90 - 150. We have employed Mars Express/SPICAM-IR nadir dataset collected during Martian years 27-31 for comparison with the GCM. Figure 1 shows the comparison of the annual water cycle on Mars according to SPICAM data and the GCM. The first image shows precipitable water vapor from SPICAM averaged over 4 Martian years and longitudes and then interpolated to the regular grid. Figure 2 displays the same for GCM data. Figures 3, 4 illustrate the difference between SPICAM data and our model and the logarithm of the ratio. The sources of discrepancies and degrees of freedom allowing the model to match the data are discussed.

  20. Nucla circulating atmospheric fluidized bed demonstration project. Quarterly technical progress report, October--December 1990

    Energy Technology Data Exchange (ETDEWEB)

    1991-01-31

    During the fourth quarter of 1990, steady-state performance testing at the Nucla Circulating Fluidized Bed (CFB) resumed under sponsorship of the US Department of Energy. Co-sponsorship of the Demonstration Test Program by the Electric Power Research Institute (EPRI) was completed on June 15, 1990. From October through December, 1990, Colorado-Ute Electric Association (CUEA) completed a total of 23 steady-state performance tests, 4 dynamic tests, and set operating records during November and December as the result of improved unit operating reliability. Highlight events and achievements during this period of operation are presented.

  1. Effect of the tropical Pacific and Indian Ocean warming since the late 1970s on wintertime Northern Hemispheric atmospheric circulation and East Asian climate interdecadal changes

    Science.gov (United States)

    Chu, Cuijiao; Yang, Xiu-Qun; Sun, Xuguang; Yang, Dejian; Jiang, Yiquan; Feng, Tao; Liang, Jin

    2017-07-01

    Observation reveals that the tropical Pacific-Indian Ocean (TPIO) has experienced a pronounced interdecadal warming since the end of the 1970s. Meanwhile, the wintertime midlatitude Northern Hemispheric atmospheric circulation and East Asian climate have also undergone substantial interdecadal changes. The effect of the TPIO warming on these interdecadal changes are identified by a suite of AMIP-type atmospheric general circulation model experiments in which the model is integrated from September 1948 to December 1999 with prescribed historical, observed realistic sea surface temperature (SST) in a specific region and climatological SST elsewhere. Results show that the TPIO warming reproduces quite well the observed Northern Hemispheric wintertime interdecadal changes, suggesting that these interdecadal changes primarily originate from the TPIO warming. However, each sub-region of TPIO has its own distinct contribution. Comparatively, the tropical central-eastern Pacific (TCEP) and tropical western Pacific (TWP) warming makes dominant contributions to the observed positive-phase PNA-like interdecadal anomaly over the North Pacific sector, while the tropical Indian Ocean (TIO) warming tends to cancel these contributions. Meanwhile, the TIO and TWP warming makes dominant contributions to the observed positive NAO-like interdecadal anomaly over the North Atlantic sector as well as the interdecadal anomalies over the Eurasian sector, although the TWP warming's contribution is relatively small. These remote responses are directly attributed to the TPIO warming-induced tropical convection, rainfall and diabatic heating increases, in which the TIO warming has the most significant effect. Moreover, the TPIO warming excites a Gill-type pattern anomaly over the tropical western Pacific, with a low-level anticyclonic circulation anomaly over the Philippine Sea. Of three sub-regions, the TIO warming dominates such a pattern, although the TWP warming tends to cancel this effect

  2. Relationship between atmospheric circulation weather types and seasonal precipitation in Serbia

    Science.gov (United States)

    Putniković, Suzana; Tošić, Ivana

    2017-04-01

    An automated version of the Lamb weather type classification scheme was used to classify daily circulation types over Serbia. The synoptic characteristics of 26 weather types and their relative frequencies are discussed for spring and autumn, complementing research previously published by Putniković et al. (Meteorol Atmos Phys 128:649-662, 2016) for winter and summer. Trends of the circulation types are presented, as well as precipitation trends during the period 1961-2010. Precipitation was modeled by the stepwise regression at six stations, defining weather types as independent variables. The anticyclonic (A) type is the most frequent class occurring in autumn (23.87%), displaying a positive trend for spring and significant negative trend for autumn. The frequencies of anticyclonic and cyclonic (C) types are almost the same for spring: 14.33 and 14.02%, respectively. The C type shows a significant negative trend only in spring. The increasing trend of the frequency of the C types and decreasing trend of the A types are in agreement with the increasing trend of precipitation in Serbia during autumn. Results suggest that the C type affects precipitation occurrence over most of the country, while the remaining 25 types provide more negligible or regional contributions to precipitation.

  3. Conceiving processes in atmospheric models-General equations, subscale parameterizations, and 'superparameterizations'

    Science.gov (United States)

    Gramelsberger, Gabriele

    The scientific understanding of atmospheric processes has been rooted in the mechanical and physical view of nature ever since dynamic meteorology gained ground in the late 19th century. Conceiving the atmosphere as a giant 'air mass circulation engine' entails applying hydro- and thermodynamical theory to the subject in order to describe the atmosphere's behaviour on small scales. But when it comes to forecasting, it turns out that this view is far too complex to be computed. The limitation of analytical methods precludes an exact solution, forcing scientists to make use of numerical simulation. However, simulation introduces two prerequisites to meteorology: First, the partitioning of the theoretical view into two parts-the large-scale behaviour of the atmosphere, and the effects of smaller-scale processes on this large-scale behaviour, so-called parametrizations; and second, the dependency on computational power in order to achieve a higher resolution. The history of today's atmospheric circulation modelling can be reconstructed as the attempt to improve the handling of these basic constraints. It can be further seen as the old schism between theory and application under new circumstances, which triggers a new discussion about the question of how processes may be conceived in atmospheric modelling.

  4. Changes in Central European Soil Moisture Availability and Atmospheric Circulation Patterns between 1875 and 2005 - Regional Climate Change in Progress?

    Science.gov (United States)

    Trnka, M.; Kysely, J.; Dubrovsky, M.; Mozny, M.; Hostynek, J.; Svoboda, M.; Hayes, M. J.; Zalud, Z.

    2007-12-01

    Relationships between the soil moisture availability and the atmospheric circulation in Central Europe were analyzed for the period 1881-2005. The analysis was based on the Hess-Brezowsky catalogue of circulation types (CTs), and a series of weekly self-calibrated Palmer Z-index (scZ-index) and Palmer Drought Severity Index (scPDSI) values at seven stations where high-quality daily data has recently become available. The results show that the large-scale droughts during spring months (MAM) were associated with east (E), south (S), and south- east (SE) circulation types, whereas during summer (JJA) and the whole vegetation season, i.e., April-September (VEG), the Central Europe high pressure systems (HM) and east (E) circulation types were conducive to drought. Statistically significant drying trends were noted at a majority of the stations, especially during MAM and JJA, over the whole period for which the scPDSI and scZ-index series were available (1875-2005). Although almost no statistically significant tendencies were found prior to 1940, a significant tendency towards more intense drought was present at all sites after this year. The largest drying trend was noted during the VEG and AMJ seasons. The overall drying trend might be associated with shifts in the frequency of CTs, especially during AMJ. Although the aggregate frequency of occurrence of drought-conducive CTs (i.e. E, S and HM) remained stable at approximately 30% up to the 1940s, a steady increase to the present 55% frequency is observed afterwards. Higher frequencies of S and HM types drove the observed increase of drought-conducive CTs at the expense of N types that are associated with wet conditions. The long-term shifts in the frequency of circulation types conducive to drought explain more than 50% of the long-term variations of both scZ-index and PDSI values over the territory of the Czech Republic, and they are likely to affect whole central European region as well. Acknowledgement: This study

  5. The Signature of Southern Hemisphere Atmospheric Circulation Patterns in Antarctic Precipitation

    Science.gov (United States)

    Marshall, Gareth J.; Thompson, David W. J.; van den Broeke, Michiel R.

    2017-11-01

    We provide the first comprehensive analysis of the relationships between large-scale patterns of Southern Hemisphere climate variability and the detailed structure of Antarctic precipitation. We examine linkages between the high spatial resolution precipitation from a regional atmospheric model and four patterns of large-scale Southern Hemisphere climate variability: the southern baroclinic annular mode, the southern annular mode, and the two Pacific-South American teleconnection patterns. Variations in all four patterns influence the spatial configuration of precipitation over Antarctica, consistent with their signatures in high-latitude meridional moisture fluxes. They impact not only the mean but also the incidence of extreme precipitation events. Current coupled-climate models are able to reproduce all four patterns of atmospheric variability but struggle to correctly replicate their regional impacts on Antarctic climate. Thus, linking these patterns directly to Antarctic precipitation variability may allow a better estimate of future changes in precipitation than using model output alone.

  6. The effects of disequilibrium carbon chemistry in general circulation models of hot Jupiters

    Science.gov (United States)

    Steinrueck, Maria Elisabeth; Parmentier, Vivien; Showman, Adam P.

    2017-10-01

    Abundances of methane (CH4) and carbon monoxide (CO) are expected to be in disequilibrium in the photospheres of hot Jupiter exoplanets due to transport-induced quenching. It has been proposed that including this effect in general circulation models (GCMs) could resolve the mismatch between models and the observed 4.5 micron phase curves of hot Jupiters HD 189733b and HD 209458b.We modified the SPARC/MITgcm to mimic quenched carbon chemistry by assuming a constant ratio of CH4 to CO to calculate the opacities. Water abundances are modified accordingly so that the number of oxygen atoms is conserved. We ran global circulation models of HD 189733b assuming different values of the CH4/CO ratio. The change in temperature structure due to the quenched abundances is significant enough to affect the emission spectra. Thus, the radiative effect of the quenched abundances should be included in global circulation modelsWe show that including disequilibrium effects does not lower the 4.5 micron night side fluxes. If CO is the dominant species, as predicted by kinetics models, the increased CO opacity is offset by a lower water opacity. In this case, the 4.5 micron band turns out to be a bad diagnostic for disequilibrium carbon chemistry. As a consequence, disequilibrium carbon chemistry does not provide a good explanation for the small nightside flux observed at 4.5 microns in HD 189733b. The 3.6 Spitzer band should be a better indicator of disequilibrium chemistry. We find that the presence of quenched abundances always reduces the phase curve amplitude at 3.6 microns compared to the chemical equilibrium case, such that they are inconsistent with existing observations of HD 189733b. Therefore, other processes such as the presence of drag or night side clouds must be responsible for the shape of currently observed HD 189733b phase curves.We find that observations between 7 and 10 microns are a better diagnostic of disequilibrium carbon chemistry in the CO dominated regime

  7. Common Era Hydroclimate and Atmospheric Circulation in the Western Mediterranean Basin

    Science.gov (United States)

    Touchan, R.; Anchukaitis, K. J.; Shishov, V. V.; Kherchouche, D.; Slimani, S.; Ilmen, R.; Hasnaoui, F.; Guibal, F.; Camarero, J. J.; Salguero, R. S.; Piermattei, A.; Sesbou, A.; Meko, D. M.; Cook, B. I.; Sabir, M.

    2016-12-01

    Drought phenomenon in the Mediterranean Basin, including North Africa and the western Mediterranean, has an impact on all segments of society and all economic sectors. To understand contemporary patterns and causes of drought in these regions, it is necessary to understand natural climate variability over the Common Era. Here, we use a network of tree-ring proxies spanning up to a millennium to understand and reconstruct both large-scale Atlantic circulation changes and regional hydroclimate. Eighty-five chronologies across the region show a variable but coherent response to winter-spring precipitation mediated by geography and topography. Reconstructions using this network of spatiotemporal drought variability as well as a new reconstruction of the North Atlantic Oscillation put the past, present, and future climate variability of the region into a long-term Common Era context.

  8. Equatorial Indian Ocean subsurface current variability in an Ocean General Circulation Model

    Science.gov (United States)

    Gnanaseelan, C.; Deshpande, Aditi

    2017-05-01

    The variability of subsurface currents in the equatorial Indian Ocean is studied using high resolution Ocean General Circulation Model (OGCM) simulations during 1958-2009. February-March eastward equatorial subsurface current (ESC) shows weak variability whereas strong variability is observed in northern summer and fall ESC. An eastward subsurface current with maximum amplitude in the pycnocline is prominent right from summer to winter during strong Indian Ocean Dipole (IOD) years when air-sea coupling is significant. On the other hand during weak IOD years, both the air-sea coupling and the ESC are weak. This strongly suggests the role of ESC on the strength of IOD. The extension of the ESC to the summer months during the strong IOD years strengthens the oceanic response and supports intensification and maintenance of IODs through modulation of air sea coupling. Although the ESC is triggered by equatorial winds, the coupled air-sea interaction associated with IODs strengthens the ESC to persist for several seasons thereby establishing a positive feedback cycle with the surface. This suggests that the ESC plays a significant role in the coupled processes associated with the evolution and intensification of IOD events by cooling the eastern basin and strengthening thermocline-SST (sea surface temperature) interaction. As the impact of IOD events on Indian summer monsoon is significant only during strong IOD years, understanding and monitoring the evolution of ESC during these years is important for summer monsoon forecasting purposes. There is a westward phase propagation of anomalous subsurface currents which persists for a year during strong IOD years, whereas such persistence or phase propagation is not seen during weak IOD years, supporting the close association between ESC and strength of air sea coupling during strong IOD years. In this study we report the processes which strengthen the IOD events and the air sea coupling associated with IOD. It also unravels

  9. A Study of Longwave Radiation Codes for Climate Studies: Validation with ARM Observations and Tests in General Circulation Models

    Energy Technology Data Exchange (ETDEWEB)

    Robert G. Ellingson

    2004-09-28

    One specific goal of the Atmospheric Radiation Measurements (ARM) program is to improve the treatment of radiative transfer in General Circulation Models (GCMs) under clear-sky, general overcast and broken cloud conditions. Our project was geared to contribute to this goal by attacking major problems associated with one of the dominant radiation components of the problem --longwave radiation. The primary long-term project objectives were to: (1) develop an optimum longwave radiation model for use in GCMs that has been calibrated with state-of-the-art observations for clear and cloudy conditions, and (2) determine how the longwave radiative forcing with an improved algorithm contributes relatively in a GCM when compared to shortwave radiative forcing, sensible heating, thermal advection and convection. The approach has been to build upon existing models in an iterative, predictive fashion. We focused on comparing calculations from a set of models with operationally observed data for clear, overcast and broken cloud conditions. The differences found through the comparisons and physical insights have been used to develop new models, most of which have been tested with new data. Our initial GCM studies used existing GCMs to study the climate model-radiation sensitivity problem. Although this portion of our initial plans was curtailed midway through the project, we anticipate that the eventual outcome of this approach will provide both a better longwave radiative forcing algorithm and from our better understanding of how longwave radiative forcing influences the model equilibrium climate, how improvements in climate prediction using this algorithm can be achieved.

  10. "New Climate" Warmed, "New Atmospheric Circulation" and "Extreme" Meteorological Phenomena associated with El Niño 2015-2016

    Science.gov (United States)

    Karrouk, M. S.

    2016-12-01

    Cumulating ocean-atmospheric thermal energy caused by global warming has resulted in the reversal of the energy balance towards the poles. This situation is characterized by a new ocean-continental thermal distribution: over the ocean, the balance is more in excess than in the mainland, if not the opposite when the balance is negative inland.Thanks to satellite observation and daily monitoring of meteorological conditions for more than ten years, we have observed that the positive balance has shifted more towards the poles, mainly in the northern hemisphere. Subtropical anticyclones are strengthened and have extended to high latitudes, especially over the Atlantic and Pacific oceans. This situation creates global peaks strengthened in winter periods, and imposes on cosmic cold the deep advection toward the south under the form of planetary valleys "Polar Vortex".This situation imposes on the jet stream a pronounced ripple and installs a meridional atmospheric circulation in winter, which brings the warm tropical air masses to reach the Arctic Circle, and cold polar air masses to reach North Africa and Florida.This situation creates unusual atmospheric events, characterized by hydrothermal "extreme" conditions: excessive heat at high latitudes, accompanied by heavy rains and floods, as well as cold at low latitudes and the appearance of snow in the Sahara!The populations are profoundly influenced by the new phenomena. The socioeconomic infrastructures can no longer assume their basic functions and man when unprotected is weak and hence the advanced vulnerability of all the regions especially those belonging to poor and developing countriesRecent studies have shown that global and regional climate system is affected by extreme events of El Niño. Statistical and dynamic links have been confirmed in Northern Africa and Western Europe; hence the importance of the fall situation and winter 2015-2016.These conditions are the consequences of the "New Climate" warmed

  11. Tropical cyclone genesis frequency over the western North Pacific simulated in medium-resolution coupled general circulation models

    Energy Technology Data Exchange (ETDEWEB)

    Yokoi, Satoru [University of Tokyo, Center for Climate System Research, Kashiwa, Chiba (Japan); Takayabu, Yukari N. [University of Tokyo, Center for Climate System Research, Kashiwa, Chiba (Japan); Japan Agency for Marine-Earth Science and Technology, Research Institute for Global Change, Yokosuka, Kanagawa (Japan); Chan, Johnny C.L. [City University of Hong Kong, Laboratory for Atmospheric Research, Department of Physics and Materials Science, Kowloon, Hong Kong (China)

    2009-10-15

    This study examines the tropical cyclone (TC) genesis frequency over the western North Pacific simulated in atmosphere-ocean coupled general circulation models from the World Climate Research Programme's Coupled Model Intercomparison Project phase 3. We first evaluate performances of eight models with atmospheric horizontal resolution of T63 or T106 by analyzing their daily-mean atmospheric outputs of twentieth-century climate simulations available from the Program for Climate Model Diagnosis and Intercomparison database. The genesis frequency is validated against the best-track data issued by the Japan Meteorological Agency. Five of the eight models reproduce realistic horizontal distribution of the TC genesis with a large fraction over the 10 -20 N, 120 -150 E area. These five high-performance models also realistically simulate the summer-winter contrast of the frequency. However, detailed seasonal march is slightly unrealistic; four of the models overestimate the frequency in the early season (May-June) while all of them underestimate the frequency in the mature season (July-September). Reasons for these biases in the seasonal march for the five high-performance models are discussed using the TC genesis potential (GP) index proposed by Emanuel and Nolan (in Am Meteor Soc, pp 240-241, 2004). The simulated GP has seasonal biases consistent with those of the TC genesis frequency. For all five models, the seasonal biases in GP are consistent with those in environmental lower-tropospheric vorticity, vertical wind shear, and relative humidity, which can be attributed to the simulated behavior of monsoon trough. The observed trough migrates northward from the equatorial region to reach the 10 -20 N latitudinal band during the mature season and contributes to the TC frequency maximum, whereas the simulated trough migrates northward too rapidly and reaches this latitude band in the early season, leading to the overestimation of the TC genesis frequency. In the

  12. Dynamic changes in temperature extremes and their association with atmospheric circulation patterns in the Songhua River Basin, China

    Science.gov (United States)

    Zhong, Keyuan; Zheng, Fenli; Wu, Hongyan; Qin, Chao; Xu, Ximeng

    2017-07-01

    Understanding dynamic changes in climate extremes is important in forecasting extreme climate events and reducing their associated impacts. The objectives of this study were to analyze the spatiotemporal variations in temperature extremes and their association with atmospheric circulation, based on daily maximum (TX) and minimum temperatures (TN) collected from 60 meteorological stations in the Songhua River Basin (SRB) and its surroundings from 1960 to 2014. Following the ETCCDI (Expert Team on Climate Change Detection and Indices), eight extreme temperature indices, including three warm indices, three cold indices and two extreme indices, were chosen to quantify temperature extremes. The Mann-Kendall method and linear trend analysis were used to examine the trends, and Pearson correlation analysis was used to analyze the correlation between the temperature extremes and each atmospheric circulation. The results showed that warm indices, including the number of warm nights, warm days, and summer days, and extreme indices, including minimum TN and maximum TX, showed increasing trends in the SRB from 1960 to 2014. On the other hand, cold indices, including the number of cold nights, cold days and frost days, showed decreasing trends; Warm indices and maximum TX showed significant positive correlations with latitude (P < 0.01). The Arctic Oscillation index (AO) displayed significant negative correlations with the cold indices (P < 0.01) and positive correlations with the warm indices. The warm indices and extreme indices had positive correlations with the Northern Hemisphere Subtropical High area and intensity indices, while the reverse relationship was found between the cold indices and Northern Hemisphere Subtropical High. The Asia polar vortex area and intensity indices showed negative correlations with warm indices and extreme indices, while they were positively correlated to cold indices. The multivariate ENSO index (MEI) showed no linear correlation with any of

  13. Atmospheric Circulation of Hot Jupiters: Three-dimensional Circulation Models of HD 209458b and HD 189733b with Simplified Forcing

    Science.gov (United States)

    Showman, Adam P.; Cooper, Curtis S.; Fortney, Jonathan J.; Marley, Mark S.

    2008-07-01

    We present global, three-dimensional numerical simulations of the atmospheric circulation on HD 209458b and HD 189733b and calculate the infrared spectra and light curves predicted by these simulations, which we compare with available observations. Radiative heating/cooling is parameterized with a simplified Newtonian relaxation scheme. Our simulations develop day-night temperature contrasts that vary strongly with pressure. At low pressure (poles. At deeper levels, the flow develops an eastward equatorial jet with speeds of 3-4 km s-1, with weaker westward flows at high latitudes. This basic flow pattern is robust to variations in model resolution, gravity, radiative time constant, and initial temperature structure. Nightside spectra show deep absorption bands of H2O, CO, and/or CH4, whereas on the dayside these absorption bands flatten out or even flip into emission. This results from the strong effect of dynamics on the vertical temperature-pressure structure; the temperature decreases strongly with altitude on the nightside but becomes almost isothermal on the dayside. In Spitzer bandpasses, our predicted planet-to-star flux ratios vary by a factor of ~2-10 with orbital phase, depending on the wavelength and chemistry. For HD 189733b, where a detailed 8 μm light curve has been obtained, we correctly produce the observed phase offset of the flux maximum, but we do not explain the flux minimum and we overpredict the total flux variation. This discrepancy likely results from the simplifications inherent in the Newtonian relaxation scheme and provides motivation for incorporating realistic radiative transfer in future studies.

  14. Climate responses of black carbon and sulfate aerosols assessed with coupled-ocean general circulation model

    Science.gov (United States)

    Takemura, T.; Suzuki, K.

    2016-12-01

    There are a lot of past studies on estimations of the aerosol radiative forcing, and therefore we can understand its best estimate and range of uncertainty, e.g., as shown in the IPCC assessment reports. Also we have implemented transient simulations from the preindustrial era to the future projection along the certain scenarios (e.g., SRES and RCP). Climate responses due to changes in anthropogenic aerosol emissions, however, have not been fully elucidated. In this study simulations with prescribed sea surface temperature and an ocean general circulation model, respectively, are done changing the ratios (0, 0.1, 0.3, 0.5, 0.8, 1.5, 2, 5, 10 times) of emission fluxes relative to the present for anthropogenic black carbon (BC) and sulfur dioxide (SO2) (parts of these simulations with the 5-times SO2 and 10-times BC emission fluxes are the same as the submitted results to the Precipitation Driver Response Model Intercomparison Project (PDRMIP)). Although the radiative forcing of the aerosol-radiation interaction both at the tropopause and surface has linear trends with the changes in BC and SO2 emissions, the equilibrium experiments with the coupled-ocean general circulation model show no clear correlations between the BC emission and surface air temperature in the realistic emission ratios (0 to 2). The simulated results suggests that the change in the surface air temperature much depends on a change in amount of water vapor, which implies that the variation of vertical profile of heating rate affected by the aerosol-radiation interaction is significant. This means that reducing short-lived climate pollutants (SLCPs) which have the positive radiative forcing at the tropopause does not necessarily result in cooling effect near the surface. Acknowledgements: Simulations in this study were executed with the supercomputer system of the National Institute for Environmental Studies, Japan. This study is partly supported by the Environment Research and Technology

  15. Synoptic patterns of atmospheric circulation associated with intense precipitation events over the Brazilian Amazon

    Science.gov (United States)

    Santos, Eliane Barbosa; Lucio, Paulo Sérgio; Santos e Silva, Cláudio Moisés

    2017-04-01

    The objective of this study is to characterize the atmospheric patterns associated with the occurrence of intense precipitation events (IPE) in different sub-regions of the Brazilian Amazon. Intense rainfall cases over six sub-regions were selected from a precipitation data set for the period from 1983 to 2012. The composition technique was used to characterize the prevailing atmospheric patterns for the occurrence of IPE. In the south of the Amazon, the composition fields showed a favorable configuration for the formation of the South Atlantic Convergence Zone (SACZ). Along the coast, the intense precipitation events must be associated with mesoscale systems, such as squall lines. In the northwest, they are apparently associated with the Intertropical Convergence Zone (ITCZ) and/or local convection. The results reveal the complexity of the synoptic environment associated with the formation and development of weather systems that produce heavy rainfall in the Amazon Basin. Several factors can interfere as conditions in large-scale, local conditions and thermodynamic factors.

  16. The role of North Atlantic Ocean circulation and biological sequestration on atmospheric CO2 uptake during the last deglaciation (CL Division Outstanding ECS Award Lecture)

    Science.gov (United States)

    Muschitiello, Francesco; D'Andrea, William J.; Dokken, Trond M.; Schmittner, Andreas

    2017-04-01

    Understanding the impact of ocean circulation on the global atmospheric CO2 budget is of paramount importance for anticipating the consequences of projected future changes in Atlantic Meridional Overturning Circulation (AMOC). In particular, the efficiency of the oceanic biological pump can impact atmospheric CO2 through changes in vertical carbon export mediated by variations in the nutrient inventory of the North Atlantic basin. However, the causal relationship between North Atlantic Ocean circulation, biological carbon sequestration, and atmospheric CO2 is poorly understood. Here we present new high-resolution planktic-benthic 14C data and biomarker records from an exceptionally well-dated marine core from the Nordic Seas spanning the last deglaciation ( 15,000-10,000 years BP). The records document for the first time large and rapid atmospheric CO2 drawdowns and increase in plankton stocks during major North Atlantic cooling events. Using transient climate simulations from a fully coupled climate-biosphere model, we show that minor perturbations of the North Atlantic biological pump resulting from surface freshening and AMOC weakening can have a major impact on the global atmospheric CO2 budget. Furthermore, our data help clarifying the timing and magnitude of the deglacial CO2 signal recorded in Antarctic ice cores. We conclude that the global CO2 budget is more sensitive to perturbations in North Atlantic circulation than previously thought, which has significance in the future debate of the AMOC response to anthropogenic warming.

  17. Experimental study of thermo-hydraulic characteristics of natural circulation loop at water and FC-72 boiling under atmospheric pressure

    Science.gov (United States)

    Kaban’kov, O. N.; Sukomel, L. A.; Zubov, N. O.; Yagov, V. V.

    2017-10-01

    The results of experimental study of thermo and hydraulic characteristics of flow boiling of water and FC-72 in natural circulation loop under atmospheric pressure are presented. The experimental data have been obtained in the range of wall heat flux densities (6 – 70) kW/m2 for water and (4.6 – 30) kW/m2 for FC-72. These two liquids differ substantially in thermophysical properties so it makes it possible to extend the range of reduced pressures almost for an order of magnitude without changing the technical parameters of experimental setup. An additional information for the analysis of flow pattern influence on onset of instability and unstable circulation mechanism have been obtained as the result. The flow up tube of the loop had inner diameter 9.1 mm and consisted of two section – heated one 98 diameters length (that is 65 % of total tube length) and upper adiabatic section with length 48 diameters. Different circulation regimes were realized in experiments: mixed regimes with single phase and boiling zones in the heated part of the tube and boiling regimes along the full length of the heated section. The experimental data on circulation velocity (flow rate) and wall temperature distributions (including pulsating components of temperature and velocity) are presented in dependence on wall heat flux density and liquid subcooling at the inlet to the heated zone. At water experiments autooscillating regimes of boiling flows were observed within the whole range of inlet liquid subcoolings up to saturation temperature and at all wall heat flux densities from lowest one (10 kW/m2) to somewhat upper limiting value of 64 kW/m2. At higher heat fluxes the two-phase boiling flow was stable not only in saturation inlet liquid temperature but also at low subcoolings. In FC-72 experiments the flow was stable at all realized heat flux densities within the range of inlet liquid subcoolings (2 – 20) °C.

  18. Generalized Geophysical Retrieval and Analysis Tool for Planetary Atmospheres Project

    Data.gov (United States)

    National Aeronautics and Space Administration — CPI proposes to develop an innovative, generalized retrieval algorithm and analysis tool (GRANT) that will facilitate analysis of remote sensing data from both...

  19. Role of Arctic sea ice in global atmospheric circulation: A review

    Science.gov (United States)

    Budikova, Dagmar

    2009-08-01

    Formed by the freezing of sea water, sea ice defines the character of the marine Arctic. The principal purpose of this review is to synthesize the published efforts that document the potential impact of Arctic sea ice on remote climates. The emphasis is on atmospheric processes and the resulting modifications in surface conditions such as air temperature, precipitation patterns, and storm track behavior at interannual timescales across the middle and low latitudes of the Northern hemisphere during cool months. Addressed also are the theoretical, methodological, and logistical challenges facing the current observational and modeling studies that aim to improve our awareness of the role that Arctic sea ice plays in the definition of global climate. Moving towards an improved understanding of the role that polar sea ice plays in shaping the global climate is a subject of timely importance as the Arctic environment is currently undergoing rapid change with little slowing down forecasted for the future.

  20. Midlatitude forcing mechanisms for glacier mass balance investigated using general circulation models

    Energy Technology Data Exchange (ETDEWEB)

    Reichert, B.K.; Bengtsson, L. [Max-Planck-Institut fuer Meteorologie, Hamburg (Germany); Oerlemans, J. [Rijksuniversiteit Utrecht (Netherlands). Inst. for Marine and Atmospheric Research

    2000-09-01

    A process-oriented modeling approach is applied in order to simulate glacier mass balance for individual glaciers using statistically downscaled general circulation models (GCMs). Glacier specific Seasonal Sensitivity Characteristics based on a mass balance model of intermediate complexity are used to simulate mass balances of Nigardsbreen (Norway) and Rhonegletscher (Switzerland). Simulations using reanalyses (ECMWF) for the period 1979-1993 are in good agreement with in situ mass balance measurements for Nigardsbreen. The method is applied to multi-century integrations of coupled (ECHAM4/OPYC) and mixed-layer (ECHAM4/MLO) GCMs excluding external forcing. A high correlation between decadal variations in the north atlantic oscillation (NAO) and mass balance of the glaciers is found. The dominant factor for this relationship is the strong impact of winter precipitation associated with the NAO. A high NAO phase means enhanced (reduced) winter precipitation for Nigardsbreen (Rhonegletscher), typically leading to a higher (lower) than normal annual mass balance. This mechanism, entirely due to internal variations in the climate system, can explain observed strong positive mass balances for Nigardsbreen and possibly other maritime Norwegian glaciers within the period 1980-1995. It can also partly be responsible for recent strong negative mass balances of Alpine glaciers. (orig.)

  1. Modeling and analysis of aerosol processes in an interactive chemistry general circulation model

    Science.gov (United States)

    Verma, Sunita; Boucher, O.; Reddy, M. S.; Upadhyaya, H. C.; Le van, P.; Binkowski, F. S.; Sharma, O. P.

    2007-02-01

    An "online" aerosol dynamics and chemistry module is included in the Laboratoire de Météorologie Dynamique general circulation model (LMDZ), so that the chemical species are advected at each dynamical time step and evolve through chemical and physical processes that have been parameterized consistently with the meteorology. These processes include anthropogenic and biogenic emissions, over 50 gas/aqueous phase chemical reactions, transport due to advection, vertical diffusion and convection, dry deposition and wet scavenging. We have introduced a size-resolved representation of aerosols which undergo various processes such as coagulation, nucleation and dry and wet scavenging. The model considers 16 prognostic tracers: water vapor, liquid water, dimethyl sulfide (DMS), hydrogen sulfide (H2S), dimethyl sulphoxide (DMSO), methanesulphonic acid (MSA), sulfur dioxide (SO2), nitrogen oxides (NOX), carbon monoxide (CO), nitric acid (HNO3), ozone (O3), hydrogen peroxide (H2O2), sulfate mass and number for Aitken and accumulation modes. The scheme accounts for two-way interactions between tropospheric chemistry and aerosols. The oxidants and chemical species fields that represent the sulfate aerosol formation are evolved interactively with the model dynamics. A detailed description on the coupled climate-chemistry interactive module is presented with the evaluation of chemical species in winter and summer seasons. Aqueous phase reactions in cloud accounted for 71% of sulfate production rate, while only 45% of the sulfate burden in the troposphere is derived from in-cloud oxidation.

  2. A General Investigation of Optimized Atmospheric Sample Duration

    Energy Technology Data Exchange (ETDEWEB)

    Eslinger, Paul W.; Miley, Harry S.

    2012-11-28

    ABSTRACT The International Monitoring System (IMS) consists of up to 80 aerosol and xenon monitoring systems spaced around the world that have collection systems sensitive enough to detect nuclear releases from underground nuclear tests at great distances (CTBT 1996; CTBTO 2011). Although a few of the IMS radionuclide stations are closer together than 1,000 km (such as the stations in Kuwait and Iran), many of them are 2,000 km or more apart. In the absence of a scientific basis for optimizing the duration of atmospheric sampling, historically scientists used a integration times from 24 hours to 14 days for radionuclides (Thomas et al. 1977). This was entirely adequate in the past because the sources of signals were far away and large, meaning that they were smeared over many days by the time they had travelled 10,000 km. The Fukushima event pointed out the unacceptable delay time (72 hours) between the start of sample acquisition and final data being shipped. A scientific basis for selecting a sample duration time is needed. This report considers plume migration of a nondecaying tracer using archived atmospheric data for 2011 in the HYSPLIT (Draxler and Hess 1998; HYSPLIT 2011) transport model. We present two related results: the temporal duration of the majority of the plume as a function of distance and the behavior of the maximum plume concentration as a function of sample collection duration and distance. The modeled plume behavior can then be combined with external information about sampler design to optimize sample durations in a sampling network.

  3. Dynamics of Arctic and Sub-Arctic Climate and Atmospheric Circulation: Diagnosis of Mechanisms and Biases Using Data Assimilation

    Energy Technology Data Exchange (ETDEWEB)

    Eric T. DeWeaver

    2010-01-19

    This is the final report for DOE grant DE-FG02-07ER64434 to Eric DeWeaver at the University of Wisconsin-Madison. The overall goal of work performed under this grant is to enhance understanding of simulations of present-day climate and greenhouse gas-induced climate change. Enhanced understanding is desirable 1) as a prerequisite for improving simulations; 2) for assessing the credibility of model simulations and their usefulness as tools for decision support; and 3) as a means to identify robust behaviors which commonly occur over a wide range of models, and may yield insights regarding the dominant physical mechanisms which determine mean climate and produce climate change. A furthe objective is to investigate the use of data assimilation as a means for examining and correcting model biases. Our primary focus is on the Arctic, but the scope of the work was expanded to include the global climate system to the extent that research targets of opportunity present themselves. Research performed under the grant falls into five main research areas: 1) a study of data assimilation using an ensemble filter with the atmospheric circulation model of the National Center for Atmospheric Research, in which both conventional observations and observations of the refraction of radio waves from GPS satellites were used to constrain the atmospheric state of the model; 2) research on the likely future status of polar bears, in which climate model simluations were used to assess the effectiveness of climate change mitigation efforts in preserving the habitat of polar bears, now considered a threatened species under global warming; 3) as assessment of the credibility of Arctic sea ice thickness simulations from climate models; 4) An examination of the persistence and reemergence of Northern Hemisphere sea ice area anomalies in climate model simulations and in observations; 5) An examination of the roles played by changes in net radiation and surface relative humidity in determine the

  4. Reassessing the impacts and the atmospheric circulation of the large storms over Portugal

    Science.gov (United States)

    Varino, F.; Trigo, R. M.; Zêzere, J. L.

    2012-04-01

    The present work was made possible after the recently development of a database of flooding and landslide events that occurred in Portugal during the 20 century. This database was collected through careful analysis of most available daily Portuguese newspapers at the time, namely "Diário de Noticias" and "Século" describing the consequences of important hydro-geological hazards during the 20 century. Therefore it is possible to evaluate the impact of these events through relatively detailed reports of the most affected places, including; number of deaths, dislodged and evacuated people, and even involved rescue entities or costs. On the other hand, the analysis of meteorological conditions for these events was made possible through the recent development of the 20 Century Reanalysis dataset from National Oceanic & Atmospheric Administration (NOAA) (Compo et al., 2011), that covers the entire period in study. This long-term database allows re-evaluating the atmospheric conditions not only at the surface but also at several levels of the atmosphere, enabling a new approach to the studied events. Moreover, the new reanalysis is also more extended in time, with available data from 1871 until 2008 which makes it possible to represent and study the weather events before 1948 with a new perspective. In this work it is analysed in detail the most important and devastating storm that took place since 1871, including the strongest sequence of storms ever observed in early December 1876 that lead to catastrophic floods in river Guadiana and Tagus. Other extreme events episodes that took place throughout the 20 century and never studied before are also analysed (albeit in less detail), namely on the 22 December 1909, 20 November 1937, 23 January and 1 February 1941, 19 November 1945, 2 January 1962 and 25 November 1967 the deadliest flood ever that occurred in Portugal. For each event it was computed the sequence of 6 hourly weather fields of precipitation rate and mean sea

  5. Simulações do clima do holoceno médio na américa do sul com o modelo de circulação geral da atmosfera do CPTEC Climate simulations of the mid-holocene in the south america as produced by the CPTEC atmospheric general circulation model

    Directory of Open Access Journals (Sweden)

    Maria Luciene Dias de Melo

    2008-06-01

    values. In general, the model simulations indicate a wetter Northeast. In the central region, south and southeast of the continent, the MH climate was marked by reduced precipitation in comparison with the present model climate. A cooling signal is observed in the MH according to the paleoclimatic evidences. A increase of the intensity of the 850 hPa flow over the continent is produced by the model in the MH climate in comparison with the present model climate. The South Atlantic subtropical high intensity is increased and less intense climatological northerly flow east of the Andes during all seasons. This weakening of the northerly flow has a significant impact on the moisture transport from the Amazon to the La Plata basin, and consequently over the SACZ.

  6. Comparison of mid-Pliocene climate predictions produced by the HadAM3 and GCMAM3 General Circulation Models

    Science.gov (United States)

    Haywood, A.M.; Chandler, M.A.; Valdes, P.J.; Salzmann, U.; Lunt, D.J.; Dowsett, H.J.

    2009-01-01

    The mid-Pliocene warm period (ca. 3 to 3.3??million years ago) has become an important interval of time for palaeoclimate modelling exercises, with a large number of studies published during the last decade. However, there has been no attempt to assess the degree of model dependency of the results obtained. Here we present an initial comparison of mid-Pliocene climatologies produced by the Goddard Institute for Space Studies and Hadley Centre for Climate Prediction and Research atmosphere-only General Circulation Models (GCMAM3 and HadAM3). Whilst both models are consistent in the simulation of broad-scale differences in mid-Pliocene surface air temperature and total precipitation rates, significant variation is noted on regional and local scales. There are also significant differences in the model predictions of total cloud cover. A terrestrial data/model comparison, facilitated by the BIOME 4 model and a new data set of Piacenzian Stage land cover [Salzmann, U., Haywood, A.M., Lunt, D.J., Valdes, P.J., Hill, D.J., (2008). A new global biome reconstruction and data model comparison for the Middle Pliocene. Global Ecology and Biogeography 17, 432-447, doi:10.1111/j.1466-8238.2007.00381.x] and combined with the use of Kappa statistics, indicates that HadAM3-based biome predictions provide a closer fit to proxy data in the mid to high-latitudes. However, GCMAM3-based biomes in the tropics provide the closest fit to proxy data. ?? 2008 Elsevier B.V.

  7. Simulating Mars' Dust Cycle with a Mars General Circulation Model: Effects of Water Ice Cloud Formation on Dust Lifting Strength and Seasonality

    Science.gov (United States)

    Kahre, Melinda A.; Haberle, Robert; Hollingsworth, Jeffery L.

    2012-01-01

    The dust cycle is critically important for the current climate of Mars. The radiative effects of dust impact the thermal and dynamical state of the atmosphere [1,2,3]. Although dust is present in the Martian atmosphere throughout the year, the level of dustiness varies with season. The atmosphere is generally the dustiest during northern fall and winter and the least dusty during northern spring and summer [4]. Dust particles are lifted into the atmosphere by dust storms that range in size from meters to thousands of kilometers across [5]. Regional storm activity is enhanced before northern winter solstice (Ls200 degrees - 240 degrees), and after northern solstice (Ls305 degrees - 340 degrees ), which produces elevated atmospheric dust loadings during these periods [5,6,7]. These pre- and post- solstice increases in dust loading are thought to be associated with transient eddy activity in the northern hemisphere with cross-equatorial transport of dust leading to enhanced dust lifting in the southern hemisphere [6]. Interactive dust cycle studies with Mars General Circulation Models (MGCMs) have included the lifting, transport, and sedimentation of radiatively active dust. Although the predicted global dust loadings from these simulations capture some aspects of the observed dust cycle, there are marked differences between the simulated and observed dust cycles [8,9,10]. Most notably, the maximum dust loading is robustly predicted by models to occur near northern winter solstice and is due to dust lifting associated with down slope flows on the flanks of the Hellas basin. Thus far, models have had difficulty simulating the observed pre- and post- solstice peaks in dust loading.

  8. The influence of winter and summer atmospheric circulation on the variability of temperature and sea ice around Greenland

    Directory of Open Access Journals (Sweden)

    Masayo Ogi

    2016-10-01

    Full Text Available Most peripheral seas of the Arctic Ocean have seen a pronounced rise in sea surface temperatures in the past century, and this signature of Arctic amplification in proximity to the land suggests that the observed marine and terrestrial changes might be connected to each other. Using in situ observations of temperature from nine coastal meteorological stations around Greenland (GrSTs and remotely sensed fields of sea ice extent (SIE, we examine the interannual variations of surface air temperature (T2m and sea level pressure (SLP anomalies associated with the GrSTs and SIEs surrounding Greenland, specifically within Baffin Bay, the Greenland Sea and Kara-Barents Seas. During winter, the interannual variation in T2m and SLP of the west and south coasts of GrSTs and the Baffin Bay SIE are different from that of the east coast of GrSTs and the SIEs in the Greenland Sea and Kara-Barents Seas. The GrSTs on the west and south coasts of Greenland and the Baffin Bay SIE are associated with the T2m anomalies over Baffin Bay and Davis Strait. The winter SLP patterns associated with these GrSTs and SIEs show positive anomalies over the Arctic and negative anomalies over the North Atlantic with a large-scale atmospheric circulation such as the winter NAO. On the contrary, the east coast of GrSTs and the SIEs in the Greenland Sea and Kara-Barents Seas are correlated with the T2m anomalies over the Greenland Sea and Barents Sea. The surface wind pattern associated with the SIEs in the Greenland Sea and Kara-Barents Seas has a cyclonic circulation in the Greenland Sea and Barents Sea. At the local scale the cyclonic circulation could induce negative SIE anomalies and contribute to increasing open water in the Greenland Sea and Barents Sea. The effect of the loss of sea ice and the heat from the open ocean warming to the atmosphere may influence the GrSTs in the east coast of Greenland. As a result, the T2m pattern associated with the GrSTs in the east coast of

  9. Geophysical Fluid Dynamics Laboratory general circulation model investigation of the indirect radiative effects of anthropogenic sulfate aerosol

    Science.gov (United States)

    Ming, Yi; Ramaswamy, V.; Ginoux, Paul A.; Horowitz, Larry W.; Russell, Lynn M.

    2005-11-01

    The Geophysical Fluid Dynamics Laboratory (GFDL) atmosphere general circulation model, with its new cloud scheme, is employed to study the indirect radiative effect of anthropogenic sulfate aerosol during the industrial period. The preindustrial and present-day monthly mean aerosol climatologies are generated from running the Model for Ozone And Related chemical Tracers (MOZART) chemistry-transport model. The respective global annual mean sulfate burdens are 0.22 and 0.81 Tg S. Cloud droplet number concentrations are related to sulfate mass concentrations using an empirical relationship (Boucher and Lohmann, 1995). A distinction is made between "forcing" and flux change at the top of the atmosphere in this study. The simulations, performed with prescribed sea surface temperature, show that the first indirect "forcing" ("Twomey" effect) amounts to an annual mean of -1.5 W m-2, concentrated largely over the oceans in the Northern Hemisphere (NH). The annual mean flux change owing to the response of the model to the first indirect effect is -1.4 W m-2, similar to the annual mean forcing. However, the model's response causes a rearrangement of cloud distribution as well as changes in longwave flux (smaller than solar flux changes). There is thus a differing geographical nature of the radiation field than for the forcing even though the global means are similar. The second indirect effect, which is necessarily an estimate made in terms of the model's response, amounts to -0.9 W m-2, but the statistical significance of the simulated geographical distribution of this effect is relatively low owing to the model's natural variability. Both the first and second effects are approximately linearly additive, giving rise to a combined annual mean flux change of -2.3 W m-2, with the NH responsible for 77% of the total flux change. Statistically significant model responses are obtained for the zonal mean total indirect effect in the entire NH and in the Southern Hemisphere low

  10. Atmospheric circulation and hydroclimate impacts of alternative warming scenarios for the Eocene

    Directory of Open Access Journals (Sweden)

    H. Carlson

    2017-08-01

    Full Text Available Recent work in modelling the warm climates of the early Eocene shows that it is possible to obtain a reasonable global match between model surface temperature and proxy reconstructions, but only by using extremely high atmospheric CO2 concentrations or more modest CO2 levels complemented by a reduction in global cloud albedo. Understanding the mix of radiative forcing that gave rise to Eocene warmth has important implications for constraining Earth's climate sensitivity, but progress in this direction is hampered by the lack of direct proxy constraints on cloud properties. Here, we explore the potential for distinguishing among different radiative forcing scenarios via their impact on regional climate changes. We do this by comparing climate model simulations of two end-member scenarios: one in which the climate is warmed entirely by CO2 (which we refer to as the greenhouse gas (GHG scenario and another in which it is warmed entirely by reduced cloud albedo (which we refer to as the low CO2–thin clouds or LCTC scenario . The two simulations have an almost identical global-mean surface temperature and equator-to-pole temperature difference, but the LCTC scenario has  ∼  11 % greater global-mean precipitation than the GHG scenario. The LCTC scenario also has cooler midlatitude continents and warmer oceans than the GHG scenario and a tropical climate which is significantly more El Niño-like. Extremely high warm-season temperatures in the subtropics are mitigated in the LCTC scenario, while cool-season temperatures are lower at all latitudes. These changes appear large enough to motivate further, more detailed study using other climate models and a more realistic set of modelling assumptions.

  11. Atmospheric circulation and hydroclimate impacts of alternative warming scenarios for the Eocene

    Science.gov (United States)

    Carlson, Henrik; Caballero, Rodrigo

    2017-08-01

    Recent work in modelling the warm climates of the early Eocene shows that it is possible to obtain a reasonable global match between model surface temperature and proxy reconstructions, but only by using extremely high atmospheric CO2 concentrations or more modest CO2 levels complemented by a reduction in global cloud albedo. Understanding the mix of radiative forcing that gave rise to Eocene warmth has important implications for constraining Earth's climate sensitivity, but progress in this direction is hampered by the lack of direct proxy constraints on cloud properties. Here, we explore the potential for distinguishing among different radiative forcing scenarios via their impact on regional climate changes. We do this by comparing climate model simulations of two end-member scenarios: one in which the climate is warmed entirely by CO2 (which we refer to as the greenhouse gas (GHG) scenario) and another in which it is warmed entirely by reduced cloud albedo (which we refer to as the low CO2-thin clouds or LCTC scenario) . The two simulations have an almost identical global-mean surface temperature and equator-to-pole temperature difference, but the LCTC scenario has ˜ 11 % greater global-mean precipitation than the GHG scenario. The LCTC scenario also has cooler midlatitude continents and warmer oceans than the GHG scenario and a tropical climate which is significantly more El Niño-like. Extremely high warm-season temperatures in the subtropics are mitigated in the LCTC scenario, while cool-season temperatures are lower at all latitudes. These changes appear large enough to motivate further, more detailed study using other climate models and a more realistic set of modelling assumptions.

  12. Role of Atmospheric Circulation and Westerly Jet Changes in the mid-Holocene East Asian Summer Monsoon

    Science.gov (United States)

    Kong, W.; Chiang, J. C. H.

    2014-12-01

    The East Asian Summer Monsoon (EASM) varies on inter-decadal to interglacial-glacial timescales. The EASM is stronger in the mid-Holocene than today, and these changes can be readily explained by orbitally-driven insolation increase during the boreal summer. However, a detailed understanding of the altered seasonal evolution of the EASM during this time is still lacking. In particular, previous work has suggested a close link between seasonal migration of the EASM and that of the mid-latitude westerlies impinging on the Tibetan Plateau. In this study, we explore, this problem in PMIP3 climate model simulations of the mid-Holocene, focusing on the role of atmospheric circulation and in particular how the westerly jet modulates the East Asia summer climate on paleoclimate timescales. Analysis of the model simulations suggests that, compared to the preindustrial simulations, the transition from Mei-Yu to deep summer rainfall occurs earlier in the mid-Holocene. This is accompanied by an earlier weakening and northward shift of westerly jet away from the Tibetan Plateau. The variation in the strength and the 3-D structure of the westerly jet in the mid-Holocene is summarized. We find that changes to the monsoonal rainfall, westerly jet and meridional circulation covary on paleoclimate timescales. Meridional wind changes in particular are tied to an altered stationary wave pattern, resembling today's the so-called 'Silk Road' teleconnection pattern, riding along the westerly jet. Diagnostic analysis also reveals changes in moist static energy and eddy energy fluxes associated with the earlier seasonal transition of the EASM. Our analyses suggest that the westerly jet is critical to the altered dynamics of the East Asian summer monsoon during the mid-Holocene.

  13. North Atlantic atmospheric circulation and surface wind in the Northeast of the Iberian Peninsula: uncertainty and long term downscaled variability

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Bustamante, E.; Jimenez, P.A. [CIEMAT, Departamento de Energias Renovables, Madrid (Spain); Universidad Complutense de Madrid, Departamento de Astrofisica y CC. de la Atmosfera, Madrid (Spain); Gonzalez-Rouco, J.F. [Universidad Complutense de Madrid, Departamento de Astrofisica y CC. de la Atmosfera, Madrid (Spain); Navarro, J. [CIEMAT, Departamento de Energias Renovables, Madrid (Spain); Xoplaki, E. [University of Bern, Institute of Geography and Oeschger Centre for Climate Change Research, Bern (Switzerland); Montavez, J.P. [Universidad de Murcia, Departamento de Fisica, Murcia (Spain)

    2012-01-15

    The variability and predictability of the surface wind field at the regional scale is explored over a complex terrain region in the northeastern Iberian Peninsula by means of a downscaling technique based on Canonical Correlation Analysis. More than a decade of observations (1992-2005) allows for calibrating and validating a statistical method that elicits the main associations between the large scale atmospheric circulation over the North Atlantic and Mediterranean areas and the regional wind field. In an initial step the downscaling model is designed by selecting parameter values from practise. To a large extent, the variability of the wind at monthly timescales is found to be governed by the large scale circulation modulated by the particular orographic features of the area. The sensitivity of the downscaling methodology to the selection of the model parameter values is explored, in a second step, by performing a systematic sampling of the parameters space, avoiding a heuristic selection. This provides a metric for the uncertainty associated with the various possible model configurations. The uncertainties associated with the model configuration are considerably dependent on the spatial variability of the wind. While the sampling of the parameters space in the model set up moderately impact estimations during the calibration period, the regional wind variability is very sensitive to the parameters selection at longer timescales. This fact illustrates that downscaling exercises based on a single configuration of parameters should be interpreted with extreme caution. The downscaling model is used to extend the estimations several centuries to the past using long datasets of sea level pressure, thereby illustrating the large temporal variability of the regional wind field from interannual to multicentennial timescales. The analysis does not evidence long term trends throughout the twentieth century, however anomalous episodes of high/low wind speeds are identified

  14. Variational estimation of process parameters in a simplified atmospheric general circulation model

    Science.gov (United States)

    Lv, Guokun; Koehl, Armin; Stammer, Detlef

    2016-04-01

    Parameterizations are used to simulate effects of unresolved sub-grid-scale processes in current state-of-the-art climate model. The values of the process parameters, which determine the model's climatology, are usually manually adjusted to reduce the difference of model mean state to the observed climatology. This process requires detailed knowledge of the model and its parameterizations. In this work, a variational method was used to estimate process parameters in the Planet Simulator (PlaSim). The adjoint code was generated using automatic differentiation of the source code. Some hydrological processes were switched off to remove the influence of zero-order discontinuities. In addition, the nonlinearity of the model limits the feasible assimilation window to about 1day, which is too short to tune the model's climatology. To extend the feasible assimilation window, nudging terms for all state variables were added to the model's equations, which essentially suppress all unstable directions. In identical twin experiments, we found that the feasible assimilation window could be extended to over 1-year and accurate parameters could be retrieved. Although the nudging terms transform to a damping of the adjoint variables and therefore tend to erases the information of the data over time, assimilating climatological information is shown to provide sufficient information on the parameters. Moreover, the mechanism of this regularization is discussed.

  15. Climate Simulations from Super-parameterized and Conventional General Circulation Models with a Third-order Turbulence Closure

    Science.gov (United States)

    Xu, Kuan-Man; Cheng, Anning

    2014-05-01

    A high-resolution cloud-resolving model (CRM) embedded in a general circulation model (GCM) is an attractive alternative for climate modeling because it replaces all traditional cloud parameterizations and explicitly simulates cloud physical processes in each grid column of the GCM. Such an approach is called "Multiscale Modeling Framework." MMF still needs to parameterize the subgrid-scale (SGS) processes associated with clouds and large turbulent eddies because circulations associated with planetary boundary layer (PBL) and in-cloud turbulence are unresolved by CRMs with horizontal grid sizes on the order of a few kilometers. A third-order turbulence closure (IPHOC) has been implemented in the CRM component of the super-parameterized Community Atmosphere Model (SPCAM). IPHOC is used to predict (or diagnose) fractional cloudiness and the variability of temperature and water vapor at scales that are not resolved on the CRM's grid. This model has produced promised results, especially for low-level cloud climatology, seasonal variations and diurnal variations (Cheng and Xu 2011, 2013a, b; Xu and Cheng 2013a, b). Because of the enormous computational cost of SPCAM-IPHOC, which is 400 times of a conventional CAM, we decided to bypass the CRM and implement the IPHOC directly to CAM version 5 (CAM5). IPHOC replaces the PBL/stratocumulus, shallow convection, and cloud macrophysics parameterizations in CAM5. Since there are large discrepancies in the spatial and temporal scales between CRM and CAM5, IPHOC used in CAM5 has to be modified from that used in SPCAM. In particular, we diagnose all second- and third-order moments except for the fluxes. These prognostic and diagnostic moments are used to select a double-Gaussian probability density function to describe the SGS variability. We also incorporate a diagnostic PBL height parameterization to represent the strong inversion above PBL. The goal of this study is to compare the simulation of the climatology from these three

  16. Fluoride pollution of atmospheric precipitation and its relationship with air circulation and weather patterns (Wielkopolski National Park, Poland).

    Science.gov (United States)

    Walna, Barbara; Kurzyca, Iwona; Bednorz, Ewa; Kolendowicz, Leszek

    2013-07-01

    A 2-year study (2010-2011) of fluorides in atmospheric precipitation in the open area and in throughfall in Wielkopolski National Park (west-central Poland) showed their high concentrations, reaching a maximum value of 2 mg/l under the tree crowns. These high values indicate substantial deposition of up to 52 mg/m(2)/year. In 2011, over 51% of open area precipitation was characterized by fluoride concentration higher than 0.10 mg/l, and in throughfall such concentrations were found in more than 86% of events. In 2010, a strong connection was evident between fluoride and acid-forming ions, and in 2011, a correlation between phosphate and nitrite ions was seen. Analysis of available data on F(-) concentrations in the air did not show an unequivocal effect on F(-) concentrations in precipitation. To find reasons for and source areas of high fluoride pollution, the cases of extreme fluoride concentration in rainwater were related to atmospheric circulation and weather patterns. Weather conditions on days of extreme pollution were determined by movement of weather fronts over western Poland, or by small cyclonic centers with meteorological fronts. Macroscale air advection over the sampling site originated in the western quadrant (NW, W, and SW), particularly in the middle layers of the troposphere (2,500-5,000 m a.s.l.). Such directions indicate western Poland and Germany as possible sources of the pollution. At the same time in the lower troposphere, air inflow was frequently from the north, showing short distance transport from local emitters, and from the agglomeration of Poznań.

  17. Atmospheric circulation in the Indian Ocean sector of East Antarctica over the last 200 years according to chemical studies of snow‑firn cover

    Directory of Open Access Journals (Sweden)

    E. Yu. Osipov

    2017-01-01

    Full Text Available Spatial and temporal variability of a sea‑salt aerosol (Na+ concentration was investigated in snow‑firn cores and snow pits taken at four sites of the Indian Ocean sector of the East Antarctica (along a profile between stations Progress and Vostok: PV‑10, NVFL‑1, SW‑42, and the Vostok point. In long annually resolved Na+ records, we had revealed the following periodicities: 17 to 95‑year (Vostok and 29 to 52‑year (NVFL‑1, while the shorter records are characterized by 8‑year periodicity. The Na+ concentrations decrease as the snow accu‑ mulation increases (especially, at the Vostok station, and this is evidence for a presence of «dilution effect» in the sites with the great part of «dry precipitation». The closest relationship was revealed between changes in flows of Na+ at points SW‑42, and PV‑10. Variability of the Na+ fluxes had been linked to the circulation indices (AAO, PDO, SOI, MEI, SPO and the sea level pressure in the Southern Hemisphere, as well as to occurrence of Elementary Circulation Mechanisms (ECM. The revealed irregularity of the Na+ precipitation over the area under investigation is caused by different atmospheric circulation patterns as well as by influ‑ ence of basic Action Centers of the Atmosphere (ACA in the Southern Hemisphere. The closest relationship is found to take place with South Pacific ACA (Vostok, 1976–2009 and with the South Indian ACA (SW‑42 and PV‑10. A presence of distant atmospheric relations (including one with El Nino had been revealed for the inland areas. Changes in features of the atmospheric circulation in the South Indian Ocean over the last 200‑year period have been reconstructed on the basis of summarized Na+ records from the Vostok station area. Distinctive feature of the atmospheric circulation is the 40‑year periodicity with its increasing intensity during the following periods: 1805–1820, 1830–1860, 1890–1900, 1940–1950, and 1980–2000. In

  18. New evidence of Holocene atmospheric circulation dynamics based on lake sediments from southern Sweden: a link to the Siberian High

    Science.gov (United States)

    Muschitiello, F.; Schwark, L.; Wohlfarth, B.; Sturm, C.; Hammarlund, D.

    2013-10-01

    Oxygen (δ18O) and carbon (δ13C) isotope records of calcitic carbonate components (Chara sp. algal encrustations and Bithynia tentaculata gastropod opercula) from a lake-sediment succession on the Baltic Sea island of Gotland, south-eastern Sweden, have been obtained to investigate regional climate dynamics during the Holocene. The hydrological sensitivity of the small lake, particularly in terms of spring snowmelt contribution to the local water budget, provides a means of tracing past changes in the influence of snow-bearing easterly winds across the Baltic Sea Proper, which signifies the wintertime strength of the Siberian High. Repeated episodic depletions in 18O at the centennial scale correlate with events of increased potassium concentration in the GISP2 ice-core record from Greenland, which indicates a coupling to large-scale fluctuations in atmospheric circulation patterns. A corresponding correlation with simultaneous depletions in 13C suggests repeated responses of the local lake hydrology to snow-rich winters through decreasing water residence time, perhaps augmented by methanogenesis due to prolonged ice-cover seasons under the influence of an expanding Siberian High. Frequency analysis of the isotopic records reveals well-defined fluctuations at quasi-500-520-, 670-, 830- and 1430-yr periodicities, and a gradually stronger impact of Polar air outbreaks across the southern Baltic Sea region with time after ca 6000 cal. BP.

  19. Ocean-Ice Sheet Interactions in the Norwegian Sea and Teleconnections to Low Latitude Hydrology and Atmospheric Circulation

    Science.gov (United States)

    Brendryen, J.; Hannisdal, B.; Haaga, K. A.; Haflidason, H.; Castro, D. D.; Grasmo, K. J.; Sejrup, H. P.; Edwards, R. L.; Cheng, H.; Kelly, M. J.; Lu, Y.

    2016-12-01

    Abrupt millennial scale climatic events known as Dansgaard-Oeschger events are a defining feature of the Quaternary climate system dynamics in the North Atlantic and beyond. We present a high-resolution multi-proxy record of ocean-ice sheet interactions in the Norwegian Sea spanning the interval between 50 and 150 ka BP. A comparison with low latitude records indicates a very close connection between the high northern latitude ocean-ice sheet interactions and large scale changes in low latitude atmospheric circulation and hydrology even on sub-millennial scales. The records are placed on a common precise radiometric chronology based on correlations to U/Th dated speleothem records from China and the Alps. This enables a comparison of the records to orbital and other climatically important parameters such as U/Th dated sea-level data from corals and speleothems. We explore the drive-response relationships in these coupled systems with the information transfer (IT) and the convergent cross mapping (CCM) analytical techniques. These methods employ conceptually different approaches to detect the relative strength and directionality of potentially chaotic and nonlinearly coupled systems. IT is a non-parametric measure of information transfer between data records based on transfer entropy, while CCM relies on delay reconstructions using Takens' theorem. This approach enables us to address how the climate system processes interact and how this interaction is affected by external forcing from for example greenhouse gases and orbital variability.

  20. Aerosol indirect effects -- general circulation model intercomparison and evaluation with satellite data

    Energy Technology Data Exchange (ETDEWEB)

    Quaas, Johannes; Ming, Yi; Menon, Surabi; Takemura, Toshihiko; Wang, Minghuai; Penner, Joyce E.; Gettelman, Andrew; Lohmann, Ulrike; Bellouin, Nicolas; Boucher, Olivier; Sayer, Andrew M.; Thomas, Gareth E.; McComiskey, Allison; Feingold, Graham; Hoose, Corinna; Kristjansson, Jon Egill; Liu, Xiaohong; Balkanski, Yves; Donner, Leo J.; Ginoux, Paul A.; Stier, Philip; Feichter, Johann; Sednev, Igor; Bauer, Susanne E.; Koch, Dorothy; Grainger, Roy G.; Kirkevag, Alf; Iversen, Trond; Seland, Oyvind; Easter, Richard; Ghan, Steven J.; Rasch, Philip J.; Morrison, Hugh; Lamarque, Jean-Francois; Iacono, Michael J.; Kinne, Stefan; Schulz, Michael

    2009-04-10

    Aerosol indirect effects continue to constitute one of the most important uncertainties for anthropogenic climate perturbations. Within the international AEROCOM initiative, the representation of aerosol-cloud-radiation interactions in ten different general circulation models (GCMs) is evaluated using three satellite datasets. The focus is on stratiform liquid water clouds since most GCMs do not include ice nucleation effects, and none of the model explicitly parameterizes aerosol effects on convective clouds. We compute statistical relationships between aerosol optical depth (Ta) and various cloud and radiation quantities in a manner that is consistent between the models and the satellite data. It is found that the model-simulated influence of aerosols on cloud droplet number concentration (Nd) compares relatively well to the satellite data at least over the ocean. The relationship between Ta and liquid water path is simulated much too strongly by the models. It is shown that this is partly related to the representation of the second aerosol indirect effect in terms of autoconversion. A positive relationship between total cloud fraction (fcld) and Ta as found in the satellite data is simulated by the majority of the models, albeit less strongly than that in the satellite data in most of them. In a discussion of the hypotheses proposed in the literature to explain the satellite-derived strong fcld - Ta relationship, our results indicate that none can be identified as unique explanation. Relationships similar to the ones found in satellite data between Ta and cloud top temperature or outgoing long-wave radiation (OLR) are simulated by only a few GCMs. The GCMs that simulate a negative OLR - Ta relationship show a strong positive correlation between Ta and fcld The short-wave total aerosol radiative forcing as simulated by the GCMs is strongly influenced by the simulated anthropogenic fraction of Ta, and parameterisation assumptions such as a lower bound on Nd

  1. General circulation of Venus from a long-term synoptic study of tropospheric CO by Venus Express/VIRTIS

    Science.gov (United States)

    Tsang, Constantine C. C.; McGouldrick, Kevin

    2017-06-01

    The understanding of spatial and temporal variations in tropospheric abundances of the trace gas carbon monoxide (CO) is key to understanding the deep atmospheric circulation on Venus. CO is entrained in the global circulation, as well as being key ingredients in the multi-reaction chemical cycle that creates and destroys the sulfuric acid that is a primary constituent of the clouds. Long-term temporal variations of CO across Venus' disc would provide critical insights and constraints into the large-scale circulation and cloud forming processes in the troposphere. Here, we present an in-depth look at the CO as a function of latitude, longitude and local time as seen by the VIRTIS-M-IR instrument onboard the Venus Express spacecraft during its three years of operation. We find that CO is slightly enhanced on the dusk hemisphere near the poles (by ∼2 ppmv) and the equatorial concentrations from 22:00 - 03:00 are also elevated. Longitudinal variations of CO are largely absent, except for a potential correlation of anomalous CO around Themis Regio. These observations provide the most stringent constraints yet on global dynamics and CO chemistry of the deep troposphere on Venus.

  2. Numerical simulation of local atmospheric circulations in the pre-Alpine area between Lake Garda and Verona

    Science.gov (United States)

    Laiti, L.; Serafin, S.; Zardi, D.

    2010-09-01

    The pre-Alpine area between Lake Garda and Verona displays a very complex and heterogeneous territory, allowing the development of several interacting systems of thermally driven local winds, the major being the lake/land breeze system on the coasts of Lake Garda and the up/down-valley wind system between the plain and the river Adige Valley. In order to investigate the local wind patterns, a series of nested numerical simulations with a horizontal resolution of 500 m were carried out using the ARPS 5.2.9 model (Xue et al. 2000, 2001), considering a fair weather day suitable for a clear development of the expected circulations (15th July 2003). The simulated wind speed and direction, pressure, temperature and water vapour mixing ratio were compared to synoptic scale meteorological charts, to vertical profiles from radiosoundings taken at the major sounding stations of the alpine region and to local scale measurements performed at the surface station of Dolcè (at the inlet of the Adige Valley). Numerical results at all scales were found to be in very good agreement with the available sets of meteorological observations. The analysis of the diurnal evolution of the 3D fields of temperature, moisture content, wind and turbulent kinetic energy allowed the identification of a very shallow and clearly defined breeze front of cold and humid air moving from off-shore towards the Lake Garda coast, from the late morning (10:00 LST) until the evening (20:00 LST). The diurnal up-valley breeze was also well reproduced: the valley atmosphere displays a thick mixed layer dominated by shallow turbulent convection between 11:00 LST and 21:00 LST. Lateral slope winds were also recognized, as they created cross-valley convective cells. While no clear evidence of a nocturnal land breeze was found in the simulations, the nocturnal down-valley wind in the Adige Valley was clearly reproduced. Finally, a scalar transport equation was added to the ARPS model in order to simulate transport

  3. Sensitivity of boreal-summer circulation and precipitation to atmospheric aerosols in selected regions – Part 1: Africa and India

    Directory of Open Access Journals (Sweden)

    Y. C. Sud

    2009-10-01

    Full Text Available Version-4 of the Goddard Earth Observing System (GEOS-4 General Circulation Model (GCM was employed to assess the influence of potential changes in aerosols on the regional circulation, ambient temperatures, and precipitation in four selected regions: India and Africa (current paper, as well as North and South America (companion paper. Ensemble-simulations were carried out with the GCM to assess the aerosol direct and indirect effects, hereafter ADE and AIE. Each simulation was started from the NCEP-analyzed initial conditions for 1 May and was integrated through May-June-July-August of each year: 1982–1987 to provide an ensemble set of six simulations. In the first set, called experiment (#1, climatological aerosols were prescribed. The next two experiments (#2 and #3 had two sets of simulations each: one with 2X and other with 1/2X the climatological aerosols over each of the four selected regions. In experiment #2, the anomaly regions were advectively restricted (AR, i.e., the large-scale prognostic fields outside the aerosol anomaly regions were prescribed while in experiment #3, the anomaly regions were advectively Interactive (AI as is the case in a normal GCM integrations, but with the same aerosols anomalies as in experiment #2. Intercomparisons of circulation, diabatic heating, and precipitation difference fields showed large disparities among the AR and AI simulations, which raised serious questions about the proverbial AR assumption, commonly invoked in regional climate simulation studies. Consequently AI simulation mode was chosen for the subsequent studies. Two more experiments (#4 and #5 were performed in the AI mode in which ADE and AIE were activated one at a time. The results showed that ADE and AIE work in concert to make the joint influences larger than sum of each acting alone. Moreover, the ADE and AIE influences were vastly different for the Indian and Africa regions, which suggest an imperative need to include them

  4. Modulation Transfer Function of a Gaussian Beam Based on the Generalized Modified Atmospheric Spectrum

    Directory of Open Access Journals (Sweden)

    Chao Gao

    2016-01-01

    Full Text Available This paper investigates the modulation transfer function of a Gaussian beam propagating through a horizontal path in weak-fluctuation non-Kolmogorov turbulence. Mathematical expressions are obtained based on the generalized modified atmospheric spectrum, which includes the spectral power law value of non-Kolmogorov turbulence, the finite inner and outer scales of turbulence, and other optical parameters of the Gaussian beam. The numerical results indicate that the atmospheric turbulence would produce less negative effects on the wireless optical communication system with an increase in the inner scale of turbulence. Additionally, the increased outer scale of turbulence makes a Gaussian beam influenced more seriously by the atmospheric turbulence.

  5. Airborne pollen in three European cities: Detection of atmospheric circulation pathways by applying three-dimensional clustering of backward trajectories

    Science.gov (United States)

    Makra, LáSzló; SáNta, TamáS.; Matyasovszky, IstváN.; Damialis, Athanasios; Karatzas, Kostas; Bergmann, Karl-Christian; Vokou, Despoina

    2010-12-01

    The long-range transport of particulates can substantially contribute to local air pollution. The importance of airborne pollen has grown due to the recent climate change; the lengthening of the pollen season and rising mean airborne pollen concentrations have increased health risks. Our aim is to identify atmospheric circulation pathways influencing pollen levels in three European cities, namely Thessaloniki, Szeged, and Hamburg. Trajectories were computed using the HYSPLIT model. The 4 day, 6 hourly three-dimensional (3-D) backward trajectories arriving at these locations at 1200 UT are produced for each day over a 5 year period. A k-means clustering algorithm using the Mahalanobis metric was applied in order to develop trajectory types. The delimitation of the clusters performed by the 3-D function "convhull" is a novel approach. The results of the cluster analysis reveal that the main pathways for Thessaloniki contributing substantially to the high mean Urticaceae pollen levels cover western Europe and the Mediterranean. The key pathway patterns for Ambrosia for Szeged are associated with backward trajectories coming from northwestern Europe, northeastern Europe, and northern Europe. A major pollen source identified is a cluster over central Europe, namely the Carpathian basin with peak values in Hungary. The principal patterns for Poaceae for Hamburg include western Europe and the mid-Atlantic region. Locations of the source areas coincide with the main habitat regions of the species in question. Critical daily pollen number exceedances conditioned on the clusters were also evaluated using two statistical indices. An attempt was made to separate medium- and long-range airborne pollen transport.

  6. Aerosol indirect effects ? general circulation model intercomparison and evaluation with satellite data

    Energy Technology Data Exchange (ETDEWEB)

    Quaas, Johannes; Ming, Yi; Menon, Surabi; Takemura, Toshihiko; Wang, Minghuai; Penner, Joyce E.; Gettelman, Andrew; Lohmann, Ulrike; Bellouin, Nicolas; Boucher, Olivier; Sayer, Andrew M.; Thomas, Gareth E.; McComiskey, Allison; Feingold, Graham; Hoose, Corinna; Kristansson, Jon Egill; Liu, Xiaohong; Balkanski, Yves; Donner, Leo J.; Ginoux, Paul A.; Stier, Philip; Grandey, Benjamin; Feichter, Johann; Sednev, Igor; Bauer, Susanne E.; Koch, Dorothy; Grainger, Roy G.; Kirkevag, Alf; Iversen, Trond; Seland, Oyvind; Easter, Richard; Ghan, Steven J.; Rasch, Philip J.; Morrison, Hugh; Lamarque, Jean-Francois; Iacono, Michael J.; Kinne, Stefan; Schulz, Michael

    2010-03-12

    Aerosol indirect effects continue to constitute one of the most important uncertainties for anthropogenic climate perturbations. Within the international AEROCOM initiative, the representation of aerosol-cloud-radiation interactions in ten different general circulation models (GCMs) is evaluated using three satellite datasets. The focus is on stratiform liquid water clouds since most GCMs do not include ice nucleation effects, and none of the model explicitly parameterises aerosol effects on convective clouds. We compute statistical relationships between aerosol optical depth ({tau}{sub a}) and various cloud and radiation quantities in a manner that is consistent between the models and the satellite data. It is found that the model-simulated influence of aerosols on cloud droplet number concentration (N{sub d}) compares relatively well to the satellite data at least over the ocean. The relationship between {tau}{sub a} and liquid water path is simulated much too strongly by the models. This suggests that the implementation of the second aerosol indirect effect mainly in terms of an autoconversion parameterisation has to be revisited in the GCMs. A positive relationship between total cloud fraction (f{sub cld}) and {tau}{sub a} as found in the satellite data is simulated by the majority of the models, albeit less strongly than that in the satellite data in most of them. In a discussion of the hypotheses proposed in the literature to explain the satellite-derived strong f{sub cld} - {tau}{sub a} relationship, our results indicate that none can be identified as a unique explanation. Relationships similar to the ones found in satellite data between {tau}{sub a} and cloud top temperature or outgoing long-wave radiation (OLR) are simulated by only a few GCMs. The GCMs that simulate a negative OLR - {tau}{sub a} relationship show a strong positive correlation between {tau}{sub a} and f{sub cld} The short-wave total aerosol radiative forcing as simulated by the GCMs is

  7. Performance evaluation of generalized M-modeled atmospheric optical communications links

    DEFF Research Database (Denmark)

    Lopez-Gonzalez, Francisco J.; Garrido-Balsellss, José María; Jurado-Navas, Antonio

    2016-01-01

    In this paper, the performance analysis of atmospheric optical communications links is analyzed in terms of the average bit error rate. To this end, the optical irradiance scintillation due to the turbulence effects is modeled by a generalization of the M´alaga or M distribution. In particular...... for the average bit error rate for each Generalized-K sub-channel, in which the turbulence parameters are real numbers, are provided, together with the closed-form expression of the whole optical link. Theses new expressions are a valuable tool for analysing the performance of atmospheric optical links....

  8. An energy and potential enstrophy conserving scheme for the shallow water equations. [orography effects on atmospheric circulation

    Science.gov (United States)

    Arakawa, A.; Lamb, V. R.

    1979-01-01

    A three-dimensional finite difference scheme for the solution of the shallow water momentum equations which accounts for the conservation of potential enstrophy in the flow of a homogeneous incompressible shallow atmosphere over steep topography as well as for total energy conservation is presented. The scheme is derived to be consistent with a reasonable scheme for potential vorticity advection in a long-term integration for a general flow with divergent mass flux. Numerical comparisons of the characteristics of the present potential enstrophy-conserving scheme with those of a scheme that conserves potential enstrophy only for purely horizontal nondivergent flow are presented which demonstrate the reduction of computational noise in the wind field with the enstrophy-conserving scheme and its convergence even in relatively coarse grids.

  9. Seasonal variability in Northern Hemisphere atmospheric circulation during the Medieval Climate Anomaly and the Little Ice Age

    Science.gov (United States)

    Edwards, Thomas W. D.; Hammarlund, Dan; Newton, Brandi W.; Sjolte, Jesper; Linderson, Hans; Sturm, Christophe; St. Amour, Natalie A.; Bailey, Joscelyn N.-L.; Nilsson, Anders L.

    2017-06-01

    Here we report new reconstructions of winter temperature and summer moisture during the past millennium in southeastern Sweden, based on stable-isotope data from a composite tree-ring sequence, that further enhances our knowledge and understanding of seasonal climate variability in the Northern Hemisphere over the past millennium. Key features of these new climate proxy records include evidence for distinctive fluctuations in winter temperature in SE Sweden, superimposed upon the general pattern of cooling between the so-called Medieval Climate Anomaly (MCA) of the early millennium and the Little Ice Age (LIA) of the late millennium, as well as evidence for sustained summer wetness during the MCA, followed by drier and less variable conditions during the LIA. We also explore these new records within a circumpolar spatial context by employing self-organizing map analysis of meteorological reanalysis data to identify potential modern analogues of mid-tropospheric synoptic circulation types in the Northern Hemisphere extratropics that can reconcile varying seasonal climate states during the MCA and LIA in SE Sweden with less variable conditions in southwestern Canada, as portrayed by paleoclimate records developed in the same manner in an earlier study.

  10. Local and regional effects of large scale atmospheric circulation patterns on winter wind power output in Western Europe

    Science.gov (United States)

    Zubiate, Laura; McDermott, Frank; Sweeney, Conor; O'Malley, Mark

    2014-05-01

    Recent studies (Brayshaw, 2009, Garcia-Bustamante, 2010, Garcia-Bustamante, 2013) have drawn attention to the sensitivity of wind speed distributions and likely wind energy power output in Western Europe to changes in low-frequency, large scale atmospheric circulation patterns such as the North Atlantic Oscillation (NAO). Wind speed variations and directional shifts as a function of the NAO state can be larger or smaller depending on the North Atlantic region that is considered. Wind speeds in Ireland and the UK for example are approximately 20 % higher during NAO + phases, and up to 30 % lower during NAO - phases relative to the long-term (30 year) climatological means. By contrast, in southern Europe, wind speeds are 15 % lower than average during NAO + phases and 15 % higher than average during NAO - phases. Crucially however, some regions such as Brittany in N.W. France have been identified in which there is negligible variability in wind speeds as a function of the NAO phase, as observed in the ERA-Interim 0.5 degree gridded reanalysis database. However, the magnitude of these effects on wind conditions is temporally and spatially non-stationary. As described by Comas-Bru and McDermott (2013) for temperature and precipitation, such non-stationarity is caused by the influence of two other patterns, the East Atlantic pattern, (EA), and the Scandinavian pattern, (SCA), which modulate the position of the NAO dipole. This phenomenon has also implications for wind speeds and directions, which has been assessed using the ERA-Interim reanalysis dataset and the indices obtained from the PC analysis of sea level pressure over the Atlantic region. In order to study the implications for power production, the interaction of the NAO and the other teleconnection patterns with local topography was also analysed, as well as how these interactions ultimately translate into wind power output. The objective is to have a better defined relationship between wind speed and power

  11. Approximate Method of Calculating Heating Rates at General Three-Dimensional Stagnation Points During Atmospheric Entry

    Science.gov (United States)

    Hamilton, H. H., II

    1982-01-01

    An approximate method for calculating heating rates at general three dimensional stagnation points is presented. The application of the method for making stagnation point heating calculations during atmospheric entry is described. Comparisons with results from boundary layer calculations indicate that the method should provide an accurate method for engineering type design and analysis applications.

  12. A study of the kinetic energy generation with general circulation models

    Science.gov (United States)

    Chen, T.-C.; Lee, Y.-H.

    1983-01-01

    The history data of winter simulation by the GLAS climate model and the NCAR community climate model are used to examine the generation of atmospheric kinetic energy. The contrast between the geographic distributions of the generation of kinetic energy and divergence of kinetic energy flux shows that kinetic energy is generated in the upstream side of jets, transported to the downstream side and destroyed there. The contributions from the time-mean and transient modes to the counterbalance between generation of kinetic energy and divergence of kinetic energy flux are also investigated. It is observed that the kinetic energy generated by the time-mean mode is essentially redistributed by the time-mean flow, while that generated by the transient flow is mainly responsible for the maintenance of the kinetic energy of the entire atmospheric flow.

  13. Simulation of the climate impact of Mt. Pinatubo eruption using ECHAM5 – Part 1: Sensitivity to the modes of atmospheric circulation and boundary conditions

    Directory of Open Access Journals (Sweden)

    M. A. Thomas

    2009-01-01

    Full Text Available The eruption of Mt. Pinatubo in the Philippines in June 1991 was one of the strongest volcanic eruptions in the 20th century and this well observed eruption can serve as an important case study to understand the subsequent weather and climate changes. In this paper, the most comprehensive simulations to date of the climate impact of Mt. Pinatubo eruption are carried out with prescribed volcanic aerosols including observed SSTs, QBO and volcanically induced ozone anomalies. This is also the first attempt to include all the known factors for the simulation of such an experiment. Here, the climate response is evaluated under different boundary conditions including one at a time, thereby, investigating the radiative and dynamical responses to individual and combined forcings by observed SSTs, QBO and volcanic effects. Two ensembles of ten members each, for unperturbed and volcanically perturbed conditions were carried out using the middle atmosphere configuration of ECHAM5 general circulation model. Our results show that the simulated climate response that may arise solely from aerosol forcing in lower stratospheric temperature is insensitive to the boundary conditions in the tropics and does not show some observed features such as the temperature signature of the QBO phases. Also, statistically significant positive anomalies in the high latitudes in NH winter of 1991/92 seen in our model simulations with prescribed observed SST and QBO phases as boundary conditions are consistent with the observations. To simulate realistically the lower stratospheric temperature response, one must include all the known factors. The pure QBO and ocean signatures in lower stratospheric temperature are simulated consistently with earlier studies. The indirect effect of the volcanic aerosols manifested as the winter warming pattern is not simulated in the ensemble mean of the experiments. Our analysis also shows that the response to El Niño conditions is very strong

  14. Chlorophyll modulation of mixed layer thermodynamics in a mixed-layer isopycnal general circulation model - An example from Arabian Sea and Equatorial Pacific

    Digital Repository Service at National Institute of Oceanography (India)

    Nakamoto, S.; PrasannaKumar, S.; Oberhuber, J.M.; Saito, H.; Muneyama, K.

    in the ocean isopycnal general circulation model (OPYC). A higher abundance of chlorophyll increases absorption of solar irradiance and heating rate in the upper ocean, resulting in decreasing the mixed layer thickness than they would be under clear waer...

  15. Effect of general anaesthesia on functional outcome in patients with anterior circulation ischaemic stroke having endovascular thrombectomy versus standard care: a meta-analysis of individual patient data

    NARCIS (Netherlands)

    Campbell, Bruce C. V.; van Zwam, Wim H.; Goyal, Mayank; Menon, Bijoy K.; Dippel, Diederik W. J.; Demchuk, Andrew M.; Bracard, Serge; White, Philip; Dávalos, Antoni; Majoie, Charles B. L. M.; van der Lugt, Aad; Ford, Gary A.; de la Ossa, Natalia Pérez; Kelly, Michael; Bourcier, Romain; Donnan, Geoffrey A.; Roos, Yvo B. W. E. M.; Bang, Oh Young; Nogueira, Raul G.; Devlin, Thomas G.; van den Berg, Lucie A.; Clarençon, Frédéric; Burns, Paul; Carpenter, Jeffrey; Berkhemer, Olvert A.; Yavagal, Dileep R.; Pereira, Vitor Mendes; Ducrocq, Xavier; Dixit, Anand; Quesada, Helena; Epstein, Jonathan; Davis, Stephen M.; Jansen, Olav; Rubiera, Marta; Urra, Xabier; Micard, Emilien; Lingsma, Hester F.; Naggara, Olivier; Brown, Scott; Guillemin, Francis; Muir, Keith W.; van Oostenbrugge, Robert J.; Saver, Jeffrey L.; Jovin, Tudor G.; Hill, Michael D.; Mitchell, Peter J.; Fransen, Puck Ss; Beumer, Debbie; Yoo, Albert J.; Schonewille, Wouter J.; Vos, Jan Albert; Nederkoorn, Paul J.; Wermer, Marieke Jh; van Walderveen, Marianne Aa; Staals, Julie; Hofmeijer, Jeannette; van Oostayen, Jacques A.; Lycklama à Nijeholt, Geert J.; Boiten, Jelis; Brouwer, Patrick A.; Emmer, Bart J.; de Bruijn, Sebastiaan F.; van Dijk, Lukas C.; Kappelle, Jaap; Lo, Rob H.; van Dijk, Ewoud J.; de Vries, Joost; de Kort, Paul L. M.; van Rooij, Willem Jan J.; van den Berg, Jan S. P.; van Hasselt, Boudewijn A. A. M.; Aerden, Leo A. M.; Dallinga, René J.; Visser, Marieke C.; Bot, Joseph C. J.; Vroomen, Patrick C.; Eshghi, Omid; Schreuder, Tobien H. C. M. L.; Heijboer, Roel J. J.; Keizer, Koos; Tielbeek, Alexander V.; den Hertog, Heleen M.; Gerrits, Dick G.; van den Berg-Vos, Renske M.; Karas, Giorgos B.; Steyerberg, Ewout W.; Flach, Zwenneke; Marquering, Henk A.; Sprengers, Marieke E. S.; Jenniskens, Sjoerd F. M.; Beenen, Ludo F. M.; van den Berg, René; Koudstaal, Peter J.; Brown, Martin M.; Liebig, Thomas; Stijnen, Theo; Andersson, Tommy; Mattle, Heinrich; Wahlgren, Nils; van der Heijden, Esther; Ghannouti, Naziha; Fleitour, Nadine; Hooijenga, Imke; Puppels, Corina; Pellikaan, Wilma; Geerling, Annet; Lindl-Velema, Annemieke; van Vemde, Gina; de Ridder, Ans; Greebe, Paut; de Bont-Stikkelbroeck, José; de Meris, Joke; Janssen, Kirsten; Struijk, Willy; Licher, Silvan; Boodt, Nikki; Ros, Adriaan; Venema, Esmee; Slokkers, Ilse; Ganpat, Raymie-Jayce; Mulder, Maxim; Saiedie, Nawid; Heshmatollah, Alis; Schipperen, Stefanie; Vinken, Stefan; van Boxtel, Tiemen; Koets, Jeroen; Boers, Merel; Santos, Emilie; Borst, Jordi; Jansen, Ivo; Kappelhof, Manon; Lucas, Marit; Geuskens, Ralph; Barros, Renan Sales; Dobbe, Roeland; Csizmadia, Marloes; Hill, M. D.; Goyal, M.; Demchuk, A. M.; Menon, B. K.; Eesa, M.; Ryckborst, K. J.; Wright, M. R.; Kamal, N. R.; Andersen, L.; Randhawa, P. A.; Stewart, T.; Patil, S.; Minhas, P.; Almekhlafi, M.; Mishra, S.; Clement, F.; Sajobi, T.; Shuaib, A.; Montanera, W. J.; Roy, D.; Silver, F. L.; Jovin, T. G.; Frei, D. F.; Sapkota, B.; Rempel, J. L.; Thornton, J.; Williams, D.; Tampieri, D.; Poppe, A. Y.; Dowlatshahi, D.; Wong, J. H.; Mitha, A. P.; Subramaniam, S.; Hull, G.; Lowerison, M. W.; Salluzzi, M.; Maxwell, M.; Lacusta, S.; Drupals, E.; Armitage, K.; Barber, P. A.; Smith, E. E.; Morrish, W. F.; Coutts, S. B.; Derdeyn, C.; Demaerschalk, B.; Yavagal, D.; Martin, R.; Brant, R.; Yu, Y.; Willinsky, R. A.; Weill, A.; Kenney, C.; Aram, H.; Stys, P. K.; Watson, T. W.; Klein, G.; Pearson, D.; Couillard, P.; Trivedi, A.; Singh, D.; Klourfeld, E.; Imoukhuede, O.; Nikneshan, D.; Blayney, S.; Reddy, R.; Choi, P.; Horton, M.; Musuka, T.; Dubuc, V.; Field, T. S.; Desai, J.; Adatia, S.; Alseraya, A.; Nambiar, V.; van Dijk, R.; Newcommon, N. J.; Schwindt, B.; Butcher, K. S.; Jeerakathil, T.; Buck, B.; Khan, K.; Naik, S. S.; Emery, D. J.; Owen, R. J.; Kotylak, T. B.; Ashforth, R. A.; Yeo, T. A.; McNally, D.; Siddiqui, M.; Saqqur, M.; Hussain, D.; Kalashyan, H.; Manosalva, A.; Kate, M.; Gioia, L.; Hasan, S.; Mohammad, A.; Muratoglu, M.; Cullen, A.; Brennan, P.; O'Hare, A.; Looby, S.; Hyland, D.; Duff, S.; McCusker, M.; Hallinan, B.; Lee, S.; McCormack, J.; Moore, A.; O'Connor, M.; Donegan, C.; Brewer, L.; Martin, A.; Murphy, S.; O'Rourke, K.; Smyth, S.; Kelly, P.; Lynch, T.; Daly, T.; O'Brien, P.; O'Driscoll, A.; Martin, M.; Collins, R.; Coughlan, T.; McCabe, D.; O'Neill, D.; Mulroy, M.; Lynch, O.; Walsh, T.; O'Donnell, M.; Galvin, T.; Harbison, J.; McElwaine, P.; Mulpeter, K.; McLoughlin, C.; Reardon, M.; Harkin, E.; Dolan, E.; Watts, M.; Cunningham, N.; Fallon, C.; Gallagher, S.; Cotter, P.; Crowe, M.; Doyle, R.; Noone, I.; Lapierre, M.; Coté, V. A.; Lanthier, S.; Odier, C.; DUROCHER, A.; Raymond, J.; Daneault, N.; Deschaintre, Y.; Jankowitz, B.; Baxendell, L.; Massaro, L.; Jackson-Graves, C.; DeCesare, S.; Porter, P.; Armbruster, K.; Adams, A.; Billigan, J.; Oakley, J.; Ducruet, A.; Jadhav, A.; Giurgiutiu, D.-V.; Aghaebrahim, A.; Reddy, V.; Hammer, M.; Starr, M.; Totoraitis, V.; Wechsler, L.; Streib, S.; Rangaraju, S.; Campbell, D.; Rocha, M.; Gulati, D.; Krings, T.; Kalman, L.; Cayley, A.; Williams, J.; Wiegner, R.; Casaubon, L. K.; Jaigobin, C.; del Campo, J. M.; Elamin, E.; Schaafsma, J. D.; Agid, R.; Farb, R.; ter Brugge, K.; Sapkoda, B. L.; Baxter, B. W.; Barton, K.; Knox, A.; Porter, A.; Sirelkhatim, A.; Devlin, T.; Dellinger, C.; Pitiyanuvath, N.; Patterson, J.; Nichols, J.; Quarfordt, S.; Calvert, J.; Hawk, H.; Fanale, C.; Bitner, A.; Novak, A.; Huddle, D.; Bellon, R.; Loy, D.; Wagner, J.; Chang, I.; Lampe, E.; Spencer, B.; Pratt, R.; Bartt, R.; Shine, S.; Dooley, G.; Nguyen, T.; Whaley, M.; McCarthy, K.; Teitelbaum, J.; Poon, W.; Campbell, N.; Cortes, M.; Lum, C.; Shamloul, R.; Robert, S.; Stotts, G.; Shamy, M.; Steffenhagen, N.; Blacquiere, D.; Hogan, M.; AlHazzaa, M.; Basir, G.; Lesiuk, H.; Iancu, D.; Santos, M.; Choe, H.; Weisman, D. C.; Jonczak, K.; Blue-Schaller, A.; Shah, Q.; MacKenzie, L.; Klein, B.; Kulandaivel, K.; Kozak, O.; Gzesh, D. J.; Harris, L. J.; Khoury, J. S.; Mandzia, J.; Pelz, D.; Crann, S.; Fleming, L.; Hesser, K.; Beauchamp, B.; Amato-Marzialli, B.; Boulton, M.; Lopez-Ojeda, P.; Sharma, M.; Lownie, S.; Chan, R.; Swartz, R.; Howard, P.; Golob, D.; Gladstone, D.; Boyle, K.; Boulos, M.; Hopyan, J.; Yang, V.; da Costa, L.; Holmstedt, C. A.; Turk, A. S.; Navarro, R.; Jauch, E.; Ozark, S.; Turner, R.; Phillips, S.; Shankar, J.; Jarrett, J.; Gubitz, G.; Maloney, W.; Vandorpe, R.; Schmidt, M.; Heidenreich, J.; Hunter, G.; Kelly, M.; Whelan, R.; Peeling, L.; Burns, P. A.; Hunter, A.; Wiggam, I.; Kerr, E.; Watt, M.; Fulton, A.; Gordon, P.; Rennie, I.; Flynn, P.; Smyth, G.; O'Leary, S.; Gentile, N.; Linares, G.; McNelis, P.; Erkmen, K.; Katz, P.; Azizi, A.; Weaver, M.; Jungreis, C.; Faro, S.; Shah, P.; Reimer, H.; Kalugdan, V.; Saposnik, G.; Bharatha, A.; Li, Y.; Kostyrko, P.; Marotta, T.; Montanera, W.; Sarma, D.; Selchen, D.; Spears, J.; Heo, J. H.; Jeong, K.; Kim, D. J.; Kim, B. M.; Kim, Y. D.; Song, D.; Lee, K.-J.; Yoo, J.; Bang, O. Y.; Rho, S.; Lee, J.; Jeon, P.; Kim, K. H.; Cha, J.; Kim, S. J.; Ryoo, S.; Lee, M. J.; Sohn, S.-I.; Kim, C.-H.; Ryu, H.-G.; Hong, J.-H.; Chang, H.-W.; Lee, C.-Y.; Rha, J.; Campbell, Bruce Cv; Churilov, Leonid; Yan, Bernard; Dowling, Richard; Yassi, Nawaf; Oxley, Thomas J.; Wu, Teddy Y.; Silver, Gabriel; McDonald, Amy; McCoy, Rachael; Kleinig, Timothy J.; Scroop, Rebecca; Dewey, Helen M.; Simpson, Marion; Brooks, Mark; Coulton, Bronwyn; Krause, Martin; Harrington, Timothy J.; Steinfort, Brendan; Faulder, Kenneth; Priglinger, Miriam; Day, Susan; Phan, Thanh; Chong, Winston; Holt, Michael; Chandra, Ronil V.; Ma, Henry; Young, Dennis; Wong, Kitty; Wijeratne, Tissa; Tu, Hans; MacKay, Elizabeth; Celestino, Sherisse; Bladin, Christopher F.; Loh, Poh Sien; Gilligan, Amanda; Ross, Zofia; Coote, Skye; Frost, Tanya; Parsons, Mark W.; Miteff, Ferdinand; Levi, Christopher R.; Ang, Timothy; Spratt, Neil; Kaauwai, Lara; Badve, Monica; Rice, Henry; de Villiers, Laetitia; Barber, P. Alan; McGuinness, Ben; Hope, Ayton; Moriarty, Maurice; Bennett, Patricia; Wong, Andrew; Coulthard, Alan; Lee, Andrew; Jannes, Jim; Field, Deborah; Sharma, Gagan; Salinas, Simon; Cowley, Elise; Snow, Barry; Kolbe, John; Stark, Richard; King, John; Macdonnell, Richard; Attia, John; D'Este, Cate; Diener, Hans Christoph; Levy, Elad I.; Bonafé, Alain; Mendes Pereira, Vitor; Jahan, Reza; Albers, Gregory W.; Cognard, Christophe; Cohen, David J.; Hacke, Werner; Mattle, Heinrich P.; Siddiqui, Adnan H.; von Kummer, Ruüdiger; Smith, Wade; Turjman, Francis; Hamilton, Scott; Chiacchierini, Richard; Amar, Arun; Sanossian, Nerses; Loh, Yince; Baxter, B.; Reddy, V. K.; Horev, A.; Star, M.; Siddiqui, A.; Hopkins, L. N.; Snyder, K.; Sawyer, R.; Hall, S.; Costalat, V.; Riquelme, C.; Machi, P.; Omer, E.; Arquizan, C.; Mourand, I.; Charif, M.; Ayrignac, X.; Menjot de Champfleur, N.; Leboucq, N.; Gascou, G.; Moynier, M.; du Mesnil de Rochemont, R.; Singer, O.; Berkefeld, J.; Foerch, C.; Lorenz, M.; Pfeilschifer, W.; Hattingen, E.; Wagner, M.; You, S. J.; Lescher, S.; Braun, H.; Dehkharghani, S.; Belagaje, S. R.; Anderson, A.; Lima, A.; Obideen, M.; Haussen, D.; Dharia, R.; Frankel, M.; Patel, V.; Owada, K.; Saad, A.; Amerson, L.; Horn, C.; Doppelheuer, S.; Schindler, K.; Lopes, D. K.; Chen, M.; Moftakhar, R.; Anton, C.; Smreczak, M.; Carpenter, J. S.; Boo, S.; Rai, A.; Roberts, T.; Tarabishy, A.; Gutmann, L.; Brooks, C.; Brick, J.; Domico, J.; Reimann, G.; Hinrichs, K.; Becker, M.; Heiss, E.; Selle, C.; Witteler, A.; Al'Boutros, S.; Danch, M.-J.; Ranft, A.; Rohde, S.; Burg, K.; Weimar, C.; Zegarac, V.; Hartmann, C.; Schlamann, M.; Göricke, S.; Ringlestein, A.; Wanke, I.; Mönninghoff, C.; Dietzold, M.; Budzik, R.; Davis, T.; Eubank, G.; Hicks, W. J.; Pema, P.; Vora, N.; Mejilla, J.; Taylor, M.; Clark, W.; Rontal, A.; Fields, J.; Peterson, B.; Nesbit, G.; Lutsep, H.; Bozorgchami, H.; Priest, R.; Ologuntoye, O.; Barnwell, S.; Dogan, A.; Herrick, K.; Takahasi, C.; Beadell, N.; Brown, B.; Jamieson, S.; Hussain, M. S.; Russman, A.; Hui, F.; Wisco, D.; Uchino, K.; Khawaja, Z.; Katzan, I.; Toth, G.; Cheng Ching, E.; Bain, M.; Man, S.; Farrag, A.; George, P.; John, S.; Shankar, L.; Drofa, A.; Dahlgren, R.; Bauer, A.; Itreat, A.; Taqui, A.; Cerejo, R.; Richmond, A.; Ringleb, P.; Bendszus, M.; Möhlenbruch, M.; Reiff, T.; Amiri, H.; Purrucker, J.; Herweh, C.; Pham, M.; Menn, O.; Ludwig, I.; Acosta, I.; Villar, C.; Morgan, W.; Sombutmai, C.; Hellinger, F.; Allen, E.; Bellew, M.; Gandhi, R.; Bonwit, E.; Aly, J.; Ecker, R. D.; Seder, D.; Morris, J.; Skaletsky, M.; Belden, J.; Baker, C.; Connolly, L. S.; Papanagiotou, P.; Roth, C.; Kastrup, A.; Politi, M.; Brunner, F.; Alexandrou, M.; Merdivan, H.; Ramsey, C.; Given Ii, C.; Renfrow, S.; Deshmukh, V.; Sasadeusz, K.; Vincent, F.; Thiesing, J. T.; Putnam, J.; Bhatt, A.; Kansara, A.; Caceves, D.; Lowenkopf, T.; Yanase, L.; Zurasky, J.; Dancer, S.; Freeman, B.; Scheibe Mirek, T.; Robison, J.; Roll, J.; Clark, D.; Rodriguez, M.; Fitzsimmons, B.-Fm; Zaidat, O.; Lynch, J. R.; Lazzaro, M.; Larson, T.; Padmore, L.; Das, E.; Farrow Schmidt, A.; Hassan, A.; Tekle, W.; Cate, C.; Jansen, O.; Cnyrim, C.; Wodarg, F.; Wiese, C.; Binder, A.; Riedel, C.; Rohr, A.; Lang, N.; Laufs, H.; Krieter, S.; Remonda, L.; Diepers, M.; Añon, J.; Nedeltchev, K.; Kahles, T.; Biethahn, S.; Lindner, M.; Chang, V.; Gächter, C.; Esperon, C.; Guglielmetti, M.; Arenillas Lara, J. F.; Martínez Galdámez, M.; Calleja Sanz, A. I.; Cortijo Garcia, E.; Garcia Bermejo, P.; Perez, S.; Mulero Carrillo, P.; Crespo Vallejo, E.; Ruiz Piñero, M.; Lopez Mesonero, L.; Reyes Muñoz, F. J.; Brekenfeld, C.; Buhk, J.-H.; Kruützelmann, A.; Thomalla, G.; Cheng, B.; Beck, C.; Hoppe, J.; Goebell, E.; Holst, B.; Grzyska, U.; Wortmann, G.; Starkman, S.; Duckwiler, G.; Jahan, R.; Rao, N.; Sheth, S.; Ng, K.; Noorian, A.; Szeder, V.; Nour, M.; McManus, M.; Huang, J.; Tarpley, J.; Tateshima, S.; Gonzalez, N.; Ali, L.; Liebeskind, D.; Hinman, J.; Calderon Arnulphi, M.; Liang, C.; Guzy, J.; Koch, S.; DeSousa, K.; Gordon Perue, G.; Elhammady, M.; Peterson, E.; Pandey, V.; Dharmadhikari, S.; Khandelwal, P.; Malik, A.; Pafford, R.; Gonzalez, P.; Ramdas, K.; Andersen, G.; Damgaard, D.; Von Weitzel Mudersbach, P.; Simonsen, C.; Ruiz de Morales Ayudarte, N.; Poulsen, M.; Sørensen, L.; Karabegovich, S.; Hjørringgaard, M.; Hjort, N.; Harbo, T.; Sørensen, K.; Deshaies, E.; Padalino, D.; Swarnkar, A.; Latorre, J. G.; Elnour, E.; El Zammar, Z.; Villwock, M.; Farid, H.; Balgude, A.; Cross, L.; Hansen, K.; Holtmannspötter, M.; Kondziella, D.; Hoejgaard, J.; Taudorf, S.; Soendergaard, H.; Wagner, A.; Cronquist, M.; Stavngaard, T.; Cortsen, M.; Krarup, L. H.; Hyldal, T.; Haring, H.-P.; Guggenberger, S.; Hamberger, M.; Trenkler, J.; Sonnberger, M.; Nussbaumer, K.; Dominger, C.; Bach, E.; Jagadeesan, B. D.; TAYLOR, R.; Kim, J.; Shea, K.; Tummala, R.; Zacharatos, H.; Sandhu, D.; Ezzeddine, M.; Grande, A.; Hildebrandt, D.; Miller, K.; Scherber, J.; Hendrickson, A.; Jumaa, M.; Zaidi, S.; Hendrickson, T.; Snyder, V.; Killer Oberpfalzer, M.; Mutzenbach, J.; Weymayr, F.; Broussalis, E.; Stadler, K.; Jedlitschka, A.; Malek, A.; Mueller Kronast, N.; Beck, P.; Martin, C.; Summers, D.; Day, J.; Bettinger, I.; Holloway, W.; Olds, K.; Arkin, S.; Akhtar, N.; Boutwell, C.; Crandall, S.; Schwartzman, M.; Weinstein, C.; Brion, B.; Prothmann, S.; Kleine, J.; Kreiser, K.; Boeckh Behrens, T.; Poppert, H.; Wunderlich, S.; Koch, M. L.; Biberacher, V.; Huberle, A.; Gora Stahlberg, G.; Knier, B.; Meindl, T.; Utpadel Fischler, D.; Zech, M.; Kowarik, M.; Seifert, C.; Schwaiger, B.; Puri, A.; Hou, S.; Wakhloo, A.; Moonis, M.; Henniger, N.; Goddeau, R.; Massari, F.; Minaeian, A.; Lozano, J. D.; Ramzan, M.; Stout, C.; Patel, A.; Tunguturi, A.; Onteddu, S.; Carandang, R.; Howk, M.; Ribó, M.; Sanjuan, E.; Rubiera, M.; Pagola, J.; Flores, A.; Muchada, M.; Meler, P.; Huerga, E.; Gelabert, S.; Coscojuela, P.; Tomasello, A.; Rodriguez, D.; Santamarina, E.; Maisterra, O.; Boned, S.; Seró, L.; Rovira, A.; Molina, C. A.; Millán, M.; Muñoz, L.; Pérez de la Ossa, N.; Gomis, M.; Dorado, L.; López-Cancio, E.; Palomeras, E.; Munuera, J.; García Bermejo, P.; Remollo, S.; Castaño, C.; García-Sort, R.; Cuadras, P.; Puyalto, P.; Hernández-Pérez, M.; Jiménez, M.; Martínez-Piñeiro, A.; Lucente, G.; Dávalos, A.; Chamorro, A.; Urra, X.; Obach, V.; Cervera, A.; Amaro, S.; Llull, L.; Codas, J.; Balasa, M.; Navarro, J.; Ariño, H.; Aceituno, A.; Rudilosso, S.; Renu, A.; Macho, J. M.; San Roman, L.; Blasco, J.; López, A.; Macías, N.; Cardona, P.; Quesada, H.; Rubio, F.; Cano, L.; Lara, B.; de Miquel, M. A.; Aja, L.; Serena, J.; Cobo, E.; Lees, Kennedy R.; Arenillas, J.; Roberts, R.; Al-Ajlan, F.; Zimmel, L.; Patel, S.; Martí-Fàbregas, J.; Salvat-Plana, M.; Bracard, S.; Anxionnat, René; Baillot, Pierre-Alexandre; Barbier, Charlotte; Derelle, Anne-Laure; Lacour, Jean-Christophe; Richard, Sébastien; Samson, Yves; Sourour, Nader; Baronnet-Chauvet, Flore; Clarencon, Frédéric; Crozier, Sophie; Deltour, Sandrine; Di Maria, Federico; Le Bouc, Raphael; Leger, Anne; Mutlu, Gurkan; Rosso, Charlotte; Szatmary, Zoltan; Yger, Marion; Zavanone, Chiara; Bakchine, Serge; Pierot, Laurent; Caucheteux, Nathalie; Estrade, Laurent; Kadziolka, Krzysztof; Leautaud, Alexandre; Renkes, Céline; Serre, Isabelle; Desal, Hubert; Guillon, Benoît; Boutoleau-Bretonniere, Claire; Daumas-Duport, Benjamin; de Gaalon, Solène; Derkinderen, Pascal; Evain, Sarah; Herisson, Fanny; Laplaud, David-Axel; Lebouvier, Thibaud; Lintia-Gaultier, Alina; Pouclet-Courtemanche, Hélène; Rouaud, Tiphaine; Rouaud Jaffrenou, Violaine; Schunck, Aurélia; Sevin-Allouet, Mathieu; Toulgoat, Frederique; Wiertlewski, Sandrine; Gauvrit, Jean-Yves; Ronziere, Thomas; Cahagne, Vincent; Ferre, Jean-Christophe; Pinel, Jean-François; Raoult, Hélène; Mas, Jean-Louis; Meder, Jean-François; Al Najjar-Carpentier, Amen-Adam; Birchenall, Julia; Bodiguel, Eric; Calvet, David; Domigo, Valérie; Godon-Hardy, Sylvie; Guiraud, Vincent; Lamy, Catherine; Majhadi, Loubna; Morin, Ludovic; Trystram, Denis; Turc, Guillaume; Berge, Jérôme; Sibon, Igor; Menegon, Patrice; Barreau, Xavier; Rouanet, François; Debruxelles, Sabrina; Kazadi, Annabelle; Renou, Pauline; Fleury, Olivier; Pasco-Papon, Anne; Dubas, Frédéric; Caroff, Jildaz; Godard Ducceschi, Sophie; Hamon, Marie-Aurélie; Lecluse, Alderic; Marc, Guillaume; Giroud, Maurice; Ricolfi, Frédéric; Bejot, Yannick; Chavent, Adrien; Gentil, Arnaud; Kazemi, Apolline; Osseby, Guy-Victor; Voguet, Charlotte; Mahagne, Marie-Hélène; Sedat, Jacques; Chau, Yves; Suissa, Laurent; Lachaud, Sylvain; Houdart, Emmanuel; Stapf, Christian; Buffon Porcher, Frédérique; Chabriat, Hugues; Guedin, Pierre; Herve, Dominique; Jouvent, Eric; Mawet, Jérôme; Saint-Maurice, Jean-Pierre; Schneble, Hans-Martin; Nighoghossian, Norbert; Berhoune, Nadia-Nawel; Bouhour, Françoise; Cho, Tae-Hee; Derex, Laurent; Felix, Sandra; Gervais-Bernard, Hélène; Gory, Benjamin; Manera, Luis; Mechtouff, Laura; Ritzenthaler, Thomas; Riva, Roberto; Salaris Silvio, Fabrizio; Tilikete, Caroline; Blanc, Raphael; Obadia, Michaël; Bartolini, Mario Bruno; Gueguen, Antoine; Piotin, Michel; Pistocchi, Silvia; Redjem, Hocine; Drouineau, Jacques; Neau, Jean-Philippe; Godeneche, Gaelle; Lamy, Matthias; Marsac, Emilia; Velasco, Stephane; Clavelou, Pierre; Chabert, Emmanuel; Bourgois, Nathalie; Cornut-Chauvinc, Catherine; Ferrier, Anna; Gabrillargues, Jean; Jean, Betty; Marques, Anna-Raquel; Vitello, Nicolas; Detante, Olivier; Barbieux, Marianne; Boubagra, Kamel; Favre Wiki, Isabelle; Garambois, Katia; Tahon, Florence; Ashok, Vasdev; Coskun, Oguzhan; Rodesch, Georges; Lapergue, Bertrand; Bourdain, Frédéric; Evrard, Serge; Graveleau, Philippe; Decroix, Jean Pierre; Wang, Adrien; Sellal, François; Ahle, Guido; Carelli, Gabriela; Dugay, Marie-Hélène; Gaultier, Claude; Lebedinsky, Ariel Pablo; Lita, Lavinia; Musacchio, Raul Mariano; Renglewicz-Destuynder, Catherine; Tournade, Alain; Vuillemet, Françis; Montoro, Francisco Macian; Mounayer, Charbel; Faugeras, Frederic; Gimenez, Laetitia; Labach, Catherine; Lautrette, Géraldine; Denier, Christian; Saliou, Guillaume; Chassin, Olivier; Dussaule, Claire; Melki, Elsa; Ozanne, Augustin; Puccinelli, Francesco; Sachet, Marina; Sarov, Mariana; Bonneville, Jean-François; Moulin, Thierry; Biondi, Alessandra; de Bustos Medeiros, Elisabeth; Vuillier, Fabrice; Courtheoux, Patrick; Viader, Fausto; Apoil-Brissard, Marion; Bataille, Mathieu; Bonnet, Anne-Laure; Cogez, Julien; Touze, Emmanuel; Leclerc, Xavier; Leys, Didier; Aggour, Mohamed; Aguettaz, Pierre; Bodenant, Marie; Cordonnier, Charlotte; Deplanque, Dominique; Girot, Marie; Henon, Hilde; Kalsoum, Erwah; Lucas, Christian; Pruvo, Jean-Pierre; Zuniga, Paolo; Arquizan, Caroline; Costalat, Vincent; Machi, Paolo; Mourand, Isabelle; Riquelme, Carlos; Bounolleau, Pierre; Arteaga, Charles; Faivre, Anthony; Bintner, Marc; Tournebize, Patrice; Charlin, Cyril; Darcel, Françoise; Gauthier-Lasalarie, Pascale; Jeremenko, Marcia; Mouton, Servane; Zerlauth, Jean-Baptiste; Lamy, Chantal; Hervé, Deramond; Hassan, Hosseini; Gaston, André; Barral, Francis-Guy; Garnier, Pierre; Beaujeux, Rémy; Wolff, Valérie; Herbreteau, Denis; Debiais, Séverine; Murray, Alicia; Ford, Gary; Clifton, Andy; Freeman, Janet; Ford, Ian; Markus, Hugh; Wardlaw, Joanna; Molyneux, Andy; Robinson, Thompson; Lewis, Steff; Norrie, John; Robertson, Fergus; Perry, Richard; Cloud, Geoffrey; Clifton, Andrew; Madigan, Jeremy; Roffe, Christine; Nayak, Sanjeev; Lobotesis, Kyriakos; Smith, Craig; Herwadkar, Amit; Kandasamy, Naga; Goddard, Tony; Bamford, John; Subramanian, Ganesh; Lenthall, Rob; Littleton, Edward; Lamin, Sal; Storey, Kelley; Ghatala, Rita; Banaras, Azra; Aeron-Thomas, John; Hazel, Bath; Maguire, Holly; Veraque, Emelda; Harrison, Louise; Keshvara, Rekha; Cunningham, James

    2018-01-01

    General anaesthesia (GA) during endovascular thrombectomy has been associated with worse patient outcomes in observational studies compared with patients treated without GA. We assessed functional outcome in ischaemic stroke patients with large vessel anterior circulation occlusion undergoing

  16. Effect of general anaesthesia on functional outcome in patients with anterior circulation ischaemic stroke having endovascular thrombectomy versus standard care: a meta-analysis of individual patient data

    NARCIS (Netherlands)

    Campbell, Bruce C. V.; van Zwam, Wim H.; Goyal, Mayank; Menon, Bijoy K.; Dippel, Diederik W. J.; Demchuk, Andrew M.; Bracard, Serge; White, Philip; Dávalos, Antoni; Majoie, Charles B. L. M.; van der Lugt, Aad; Ford, Gary A.; de la Ossa, Natalia Pérez; Kelly, Michael; Bourcier, Romain; Donnan, Geoffrey A.; Roos, Yvo B. W. E. M.; Bang, Oh Young; Nogueira, Raul G.; Devlin, Thomas G.; van den Berg, Lucie A.; Clarençon, Frédéric; Burns, Paul; Carpenter, Jeffrey; Berkhemer, Olvert A.; Yavagal, Dileep R.; Pereira, Vitor Mendes; Ducrocq, Xavier; Dixit, Anand; Quesada, Helena; Epstein, Jonathan; Davis, Stephen M.; Jansen, Olav; Rubiera, Marta; Urra, Xabier; Micard, Emilien; Lingsma, Hester F.; Naggara, Olivier; Brown, Scott; Guillemin, Francis; Muir, Keith W.; van Oostenbrugge, Robert J.; Saver, Jeffrey L.; Jovin, Tudor G.; Hill, Michael D.; Mitchell, Peter J.; Fransen, Puck Ss; Beumer, Debbie; Yoo, Albert J.; Schonewille, Wouter J.; Vos, Jan Albert; Nederkoorn, Paul J.; Wermer, Marieke Jh; van Walderveen, Marianne Aa; Staals, Julie; Hofmeijer, Jeannette; van Oostayen, Jacques A.; Lycklama à Nijeholt, Geert J.; Boiten, Jelis; Brouwer, Patrick A.; Emmer, Bart J.; de Bruijn, Sebastiaan F.; van Dijk, Lukas C.; Kappelle, Jaap; Lo, Rob H.; van Dijk, Ewoud J.; de Vries, Joost; de Kort, Paul L. M.; van Rooij, Willem Jan J.; van den Berg, Jan S. P.; van Hasselt, Boudewijn A. A. M.; Aerden, Leo A. M.; Dallinga, René J.; Visser, Marieke C.; Bot, Joseph C. J.; Vroomen, Patrick C.; Eshghi, Omid; Schreuder, Tobien H. C. M. L.; Heijboer, Roel J. J.; Keizer, Koos; Tielbeek, Alexander V.; den Hertog, Heleen M.; Gerrits, Dick G.; van den Berg-Vos, Renske M.; Karas, Giorgos B.; Steyerberg, Ewout W.; Flach, Zwenneke; Marquering, Henk A.; Sprengers, Marieke E. S.; Jenniskens, Sjoerd F. M.; Beenen, Ludo F. M.; van den Berg, René; Koudstaal, Peter J.; Brown, Martin M.; Liebig, Thomas; Stijnen, Theo; Andersson, Tommy; Mattle, Heinrich; Wahlgren, Nils; van der Heijden, Esther; Ghannouti, Naziha; Fleitour, Nadine; Hooijenga, Imke; Puppels, Corina; Pellikaan, Wilma; Geerling, Annet; Lindl-Velema, Annemieke; van Vemde, Gina; de Ridder, Ans; Greebe, Paut; de Bont-Stikkelbroeck, José; de Meris, Joke; Janssen, Kirsten; Struijk, Willy; Licher, Silvan; Boodt, Nikki; Ros, Adriaan; Venema, Esmee; Slokkers, Ilse; Ganpat, Raymie-Jayce; Mulder, Maxim; Saiedie, Nawid; Heshmatollah, Alis; Schipperen, Stefanie; Vinken, Stefan; van Boxtel, Tiemen; Koets, Jeroen; Boers, Merel; Santos, Emilie; Borst, Jordi; Jansen, Ivo; Kappelhof, Manon; Lucas, Marit; Geuskens, Ralph; Barros, Renan Sales; Dobbe, Roeland; Csizmadia, Marloes; Hill, M. D.; Goyal, M.; Demchuk, A. M.; Menon, B. K.; Eesa, M.; Ryckborst, K. J.; Wright, M. R.; Kamal, N. R.; Andersen, L.; Randhawa, P. A.; Stewart, T.; Patil, S.; Minhas, P.; Almekhlafi, M.; Mishra, S.; Clement, F.; Sajobi, T.; Shuaib, A.; Montanera, W. J.; Roy, D.; Silver, F. L.; Jovin, T. G.; Frei, D. F.; Sapkota, B.; Rempel, J. L.; Thornton, J.; Williams, D.; Tampieri, D.; Poppe, A. Y.; Dowlatshahi, D.; Wong, J. H.; Mitha, A. P.; Subramaniam, S.; Hull, G.; Lowerison, M. W.; Salluzzi, M.; Maxwell, M.; Lacusta, S.; Drupals, E.; Armitage, K.; Barber, P. A.; Smith, E. E.; Morrish, W. F.; Coutts, S. B.; Derdeyn, C.; Demaerschalk, B.; Yavagal, D.; Martin, R.; Brant, R.; Yu, Y.; Willinsky, R. A.; Weill, A.; Kenney, C.; Aram, H.; Stys, P. K.; Watson, T. W.; Klein, G.; Pearson, D.; Couillard, P.; Trivedi, A.; Singh, D.; Klourfeld, E.; Imoukhuede, O.; Nikneshan, D.; Blayney, S.; Reddy, R.; Choi, P.; Horton, M.; Musuka, T.; Dubuc, V.; Field, T. S.; Desai, J.; Adatia, S.; Alseraya, A.; Nambiar, V.; van Dijk, R.; Newcommon, N. J.; Schwindt, B.; Butcher, K. S.; Jeerakathil, T.; Buck, B.; Khan, K.; Naik, S. S.; Emery, D. J.; Owen, R. J.; Kotylak, T. B.; Ashforth, R. A.; Yeo, T. A.; McNally, D.; Siddiqui, M.; Saqqur, M.; Hussain, D.; Kalashyan, H.; Manosalva, A.; Kate, M.; Gioia, L.; Hasan, S.; Mohammad, A.; Muratoglu, M.; Cullen, A.; Brennan, P.; O'Hare, A.; Looby, S.; Hyland, D.; Duff, S.; McCusker, M.; Hallinan, B.; Lee, S.; McCormack, J.; Moore, A.; O'Connor, M.; Donegan, C.; Brewer, L.; Martin, A.; Murphy, S.; O'Rourke, K.; Smyth, S.; Kelly, P.; Lynch, T.; Daly, T.; O'Brien, P.; O'Driscoll, A.; Martin, M.; Collins, R.; Coughlan, T.; McCabe, D.; O'Neill, D.; Mulroy, M.; Lynch, O.; Walsh, T.; O'Donnell, M.; Galvin, T.; Harbison, J.; McElwaine, P.; Mulpeter, K.; McLoughlin, C.; Reardon, M.; Harkin, E.; Dolan, E.; Watts, M.; Cunningham, N.; Fallon, C.; Gallagher, S.; Cotter, P.; Crowe, M.; Doyle, R.; Noone, I.; Lapierre, M.; Coté, V. A.; Lanthier, S.; Odier, C.; DUROCHER, A.; Raymond, J.; Daneault, N.; Deschaintre, Y.; Jankowitz, B.; Baxendell, L.; Massaro, L.; Jackson-Graves, C.; DeCesare, S.; Porter, P.; Armbruster, K.; Adams, A.; Billigan, J.; Oakley, J.; Ducruet, A.; Jadhav, A.; Giurgiutiu, D.-V.; Aghaebrahim, A.; Reddy, V.; Hammer, M.; Starr, M.; Totoraitis, V.; Wechsler, L.; Streib, S.; Rangaraju, S.; Campbell, D.; Rocha, M.; Gulati, D.; Krings, T.; Kalman, L.; Cayley, A.; Williams, J.; Wiegner, R.; Casaubon, L. K.; Jaigobin, C.; del Campo, J. M.; Elamin, E.; Schaafsma, J. D.; Agid, R.; Farb, R.; ter Brugge, K.; Sapkoda, B. L.; Baxter, B. W.; Barton, K.; Knox, A.; Porter, A.; Sirelkhatim, A.; Devlin, T.; Dellinger, C.; Pitiyanuvath, N.; Patterson, J.; Nichols, J.; Quarfordt, S.; Calvert, J.; Hawk, H.; Fanale, C.; Bitner, A.; Novak, A.; Huddle, D.; Bellon, R.; Loy, D.; Wagner, J.; Chang, I.; Lampe, E.; Spencer, B.; Pratt, R.; Bartt, R.; Shine, S.; Dooley, G.; Nguyen, T.; Whaley, M.; McCarthy, K.; Teitelbaum, J.; Poon, W.; Campbell, N.; Cortes, M.; Lum, C.; Shamloul, R.; Robert, S.; Stotts, G.; Shamy, M.; Steffenhagen, N.; Blacquiere, D.; Hogan, M.; AlHazzaa, M.; Basir, G.; Lesiuk, H.; Iancu, D.; Santos, M.; Choe, H.; Weisman, D. C.; Jonczak, K.; Blue-Schaller, A.; Shah, Q.; MacKenzie, L.; Klein, B.; Kulandaivel, K.; Kozak, O.; Gzesh, D. J.; Harris, L. J.; Khoury, J. S.; Mandzia, J.; Pelz, D.; Crann, S.; Fleming, L.; Hesser, K.; Beauchamp, B.; Amato-Marzialli, B.; Boulton, M.; Lopez-Ojeda, P.; Sharma, M.; Lownie, S.; Chan, R.; Swartz, R.; Howard, P.; Golob, D.; Gladstone, D.; Boyle, K.; Boulos, M.; Hopyan, J.; Yang, V.; da Costa, L.; Holmstedt, C. A.; Turk, A. S.; Navarro, R.; Jauch, E.; Ozark, S.; Turner, R.; Phillips, S.; Shankar, J.; Jarrett, J.; Gubitz, G.; Maloney, W.; Vandorpe, R.; Schmidt, M.; Heidenreich, J.; Hunter, G.; Kelly, M.; Whelan, R.; Peeling, L.; Burns, P. A.; Hunter, A.; Wiggam, I.; Kerr, E.; Watt, M.; Fulton, A.; Gordon, P.; Rennie, I.; Flynn, P.; Smyth, G.; O'Leary, S.; Gentile, N.; Linares, G.; McNelis, P.; Erkmen, K.; Katz, P.; Azizi, A.; Weaver, M.; Jungreis, C.; Faro, S.; Shah, P.; Reimer, H.; Kalugdan, V.; Saposnik, G.; Bharatha, A.; Li, Y.; Kostyrko, P.; Marotta, T.; Montanera, W.; Sarma, D.; Selchen, D.; Spears, J.; Heo, J. H.; Jeong, K.; Kim, D. J.; Kim, B. M.; Kim, Y. D.; Song, D.; Lee, K.-J.; Yoo, J.; Bang, O. Y.; Rho, S.; Lee, J.; Jeon, P.; Kim, K. H.; Cha, J.; Kim, S. J.; Ryoo, S.; Lee, M. J.; Sohn, S.-I.; Kim, C.-H.; Ryu, H.-G.; Hong, J.-H.; Chang, H.-W.; Lee, C.-Y.; Rha, J.; Campbell, Bruce Cv; Churilov, Leonid; Yan, Bernard; Dowling, Richard; Yassi, Nawaf; Oxley, Thomas J.; Wu, Teddy Y.; Silver, Gabriel; McDonald, Amy; McCoy, Rachael; Kleinig, Timothy J.; Scroop, Rebecca; Dewey, Helen M.; Simpson, Marion; Brooks, Mark; Coulton, Bronwyn; Krause, Martin; Harrington, Timothy J.; Steinfort, Brendan; Faulder, Kenneth; Priglinger, Miriam; Day, Susan; Phan, Thanh; Chong, Winston; Holt, Michael; Chandra, Ronil V.; Ma, Henry; Young, Dennis; Wong, Kitty; Wijeratne, Tissa; Tu, Hans; MacKay, Elizabeth; Celestino, Sherisse; Bladin, Christopher F.; Loh, Poh Sien; Gilligan, Amanda; Ross, Zofia; Coote, Skye; Frost, Tanya; Parsons, Mark W.; Miteff, Ferdinand; Levi, Christopher R.; Ang, Timothy; Spratt, Neil; Kaauwai, Lara; Badve, Monica; Rice, Henry; de Villiers, Laetitia; Barber, P. Alan; McGuinness, Ben; Hope, Ayton; Moriarty, Maurice; Bennett, Patricia; Wong, Andrew; Coulthard, Alan; Lee, Andrew; Jannes, Jim; Field, Deborah; Sharma, Gagan; Salinas, Simon; Cowley, Elise; Snow, Barry; Kolbe, John; Stark, Richard; King, John; Macdonnell, Richard; Attia, John; D'Este, Cate; Diener, Hans Christoph; Levy, Elad I.; Bonafé, Alain; Mendes Pereira, Vitor; Jahan, Reza; Albers, Gregory W.; Cognard, Christophe; Cohen, David J.; Hacke, Werner; Mattle, Heinrich P.; Siddiqui, Adnan H.; von Kummer, Ruüdiger; Smith, Wade; Turjman, Francis; Hamilton, Scott; Chiacchierini, Richard; Amar, Arun; Sanossian, Nerses; Loh, Yince; Baxter, B.; Reddy, V. K.; Horev, A.; Star, M.; Siddiqui, A.; Hopkins, L. N.; Snyder, K.; Sawyer, R.; Hall, S.; Costalat, V.; Riquelme, C.; Machi, P.; Omer, E.; Arquizan, C.; Mourand, I.; Charif, M.; Ayrignac, X.; Menjot de Champfleur, N.; Leboucq, N.; Gascou, G.; Moynier, M.; du Mesnil de Rochemont, R.; Singer, O.; Berkefeld, J.; Foerch, C.; Lorenz, M.; Pfeilschifer, W.; Hattingen, E.; Wagner, M.; You, S. J.; Lescher, S.; Braun, H.; Dehkharghani, S.; Belagaje, S. R.; Anderson, A.; Lima, A.; Obideen, M.; Haussen, D.; Dharia, R.; Frankel, M.; Patel, V.; Owada, K.; Saad, A.; Amerson, L.; Horn, C.; Doppelheuer, S.; Schindler, K.; Lopes, D. K.; Chen, M.; Moftakhar, R.; Anton, C.; Smreczak, M.; Carpenter, J. S.; Boo, S.; Rai, A.; Roberts, T.; Tarabishy, A.; Gutmann, L.; Brooks, C.; Brick, J.; Domico, J.; Reimann, G.; Hinrichs, K.; Becker, M.; Heiss, E.; Selle, C.; Witteler, A.; Al'Boutros, S.; Danch, M.-J.; Ranft, A.; Rohde, S.; Burg, K.; Weimar, C.; Zegarac, V.; Hartmann, C.; Schlamann, M.; Göricke, S.; Ringlestein, A.; Wanke, I.; Mönninghoff, C.; Dietzold, M.; Budzik, R.; Davis, T.; Eubank, G.; Hicks, W. J.; Pema, P.; Vora, N.; Mejilla, J.; Taylor, M.; Clark, W.; Rontal, A.; Fields, J.; Peterson, B.; Nesbit, G.; Lutsep, H.; Bozorgchami, H.; Priest, R.; Ologuntoye, O.; Barnwell, S.; Dogan, A.; Herrick, K.; Takahasi, C.; Beadell, N.; Brown, B.; Jamieson, S.; Hussain, M. S.; Russman, A.; Hui, F.; Wisco, D.; Uchino, K.; Khawaja, Z.; Katzan, I.; Toth, G.; Cheng Ching, E.; Bain, M.; Man, S.; Farrag, A.; George, P.; John, S.; Shankar, L.; Drofa, A.; Dahlgren, R.; Bauer, A.; Itreat, A.; Taqui, A.; Cerejo, R.; Richmond, A.; Ringleb, P.; Bendszus, M.; Möhlenbruch, M.; Reiff, T.; Amiri, H.; Purrucker, J.; Herweh, C.; Pham, M.; Menn, O.; Ludwig, I.; Acosta, I.; Villar, C.; Morgan, W.; Sombutmai, C.; Hellinger, F.; Allen, E.; Bellew, M.; Gandhi, R.; Bonwit, E.; Aly, J.; Ecker, R. D.; Seder, D.; Morris, J.; Skaletsky, M.; Belden, J.; Baker, C.; Connolly, L. S.; Papanagiotou, P.; Roth, C.; Kastrup, A.; Politi, M.; Brunner, F.; Alexandrou, M.; Merdivan, H.; Ramsey, C.; Given Ii, C.; Renfrow, S.; Deshmukh, V.; Sasadeusz, K.; Vincent, F.; Thiesing, J. T.; Putnam, J.; Bhatt, A.; Kansara, A.; Caceves, D.; Lowenkopf, T.; Yanase, L.; Zurasky, J.; Dancer, S.; Freeman, B.; Scheibe Mirek, T.; Robison, J.; Roll, J.; Clark, D.; Rodriguez, M.; Fitzsimmons, B.-Fm; Zaidat, O.; Lynch, J. R.; Lazzaro, M.; Larson, T.; Padmore, L.; Das, E.; Farrow Schmidt, A.; Hassan, A.; Tekle, W.; Cate, C.; Jansen, O.; Cnyrim, C.; Wodarg, F.; Wiese, C.; Binder, A.; Riedel, C.; Rohr, A.; Lang, N.; Laufs, H.; Krieter, S.; Remonda, L.; Diepers, M.; Añon, J.; Nedeltchev, K.; Kahles, T.; Biethahn, S.; Lindner, M.; Chang, V.; Gächter, C.; Esperon, C.; Guglielmetti, M.; Arenillas Lara, J. F.; Martínez Galdámez, M.; Calleja Sanz, A. I.; Cortijo Garcia, E.; Garcia Bermejo, P.; Perez, S.; Mulero Carrillo, P.; Crespo Vallejo, E.; Ruiz Piñero, M.; Lopez Mesonero, L.; Reyes Muñoz, F. J.; Brekenfeld, C.; Buhk, J.-H.; Kruützelmann, A.; Thomalla, G.; Cheng, B.; Beck, C.; Hoppe, J.; Goebell, E.; Holst, B.; Grzyska, U.; Wortmann, G.; Starkman, S.; Duckwiler, G.; Jahan, R.; Rao, N.; Sheth, S.; Ng, K.; Noorian, A.; Szeder, V.; Nour, M.; McManus, M.; Huang, J.; Tarpley, J.; Tateshima, S.; Gonzalez, N.; Ali, L.; Liebeskind, D.; Hinman, J.; Calderon Arnulphi, M.; Liang, C.; Guzy, J.; Koch, S.; DeSousa, K.; Gordon Perue, G.; Elhammady, M.; Peterson, E.; Pandey, V.; Dharmadhikari, S.; Khandelwal, P.; Malik, A.; Pafford, R.; Gonzalez, P.; Ramdas, K.; Andersen, G.; Damgaard, D.; Von Weitzel Mudersbach, P.; Simonsen, C.; Ruiz de Morales Ayudarte, N.; Poulsen, M.; Sørensen, L.; Karabegovich, S.; Hjørringgaard, M.; Hjort, N.; Harbo, T.; Sørensen, K.; Deshaies, E.; Padalino, D.; Swarnkar, A.; Latorre, J. G.; Elnour, E.; El Zammar, Z.; Villwock, M.; Farid, H.; Balgude, A.; Cross, L.; Hansen, K.; Holtmannspötter, M.; Kondziella, D.; Hoejgaard, J.; Taudorf, S.; Soendergaard, H.; Wagner, A.; Cronquist, M.; Stavngaard, T.; Cortsen, M.; Krarup, L. H.; Hyldal, T.; Haring, H.-P.; Guggenberger, S.; Hamberger, M.; Trenkler, J.; Sonnberger, M.; Nussbaumer, K.; Dominger, C.; Bach, E.; Jagadeesan, B. D.; TAYLOR, R.; Kim, J.; Shea, K.; Tummala, R.; Zacharatos, H.; Sandhu, D.; Ezzeddine, M.; Grande, A.; Hildebrandt, D.; Miller, K.; Scherber, J.; Hendrickson, A.; Jumaa, M.; Zaidi, S.; Hendrickson, T.; Snyder, V.; Killer Oberpfalzer, M.; Mutzenbach, J.; Weymayr, F.; Broussalis, E.; Stadler, K.; Jedlitschka, A.; Malek, A.; Mueller Kronast, N.; Beck, P.; Martin, C.; Summers, D.; Day, J.; Bettinger, I.; Holloway, W.; Olds, K.; Arkin, S.; Akhtar, N.; Boutwell, C.; Crandall, S.; Schwartzman, M.; Weinstein, C.; Brion, B.; Prothmann, S.; Kleine, J.; Kreiser, K.; Boeckh Behrens, T.; Poppert, H.; Wunderlich, S.; Koch, M. L.; Biberacher, V.; Huberle, A.; Gora Stahlberg, G.; Knier, B.; Meindl, T.; Utpadel Fischler, D.; Zech, M.; Kowarik, M.; Seifert, C.; Schwaiger, B.; Puri, A.; Hou, S.; Wakhloo, A.; Moonis, M.; Henniger, N.; Goddeau, R.; Massari, F.; Minaeian, A.; Lozano, J. D.; Ramzan, M.; Stout, C.; Patel, A.; Tunguturi, A.; Onteddu, S.; Carandang, R.; Howk, M.; Ribó, M.; Sanjuan, E.; Rubiera, M.; Pagola, J.; Flores, A.; Muchada, M.; Meler, P.; Huerga, E.; Gelabert, S.; Coscojuela, P.; Tomasello, A.; Rodriguez, D.; Santamarina, E.; Maisterra, O.; Boned, S.; Seró, L.; Rovira, A.; Molina, C. A.; Millán, M.; Muñoz, L.; Pérez de la Ossa, N.; Gomis, M.; Dorado, L.; López-Cancio, E.; Palomeras, E.; Munuera, J.; García Bermejo, P.; Remollo, S.; Castaño, C.; García-Sort, R.; Cuadras, P.; Puyalto, P.; Hernández-Pérez, M.; Jiménez, M.; Martínez-Piñeiro, A.; Lucente, G.; Dávalos, A.; Chamorro, A.; Urra, X.; Obach, V.; Cervera, A.; Amaro, S.; Llull, L.; Codas, J.; Balasa, M.; Navarro, J.; Ariño, H.; Aceituno, A.; Rudilosso, S.; Renu, A.; Macho, J. M.; San Roman, L.; Blasco, J.; López, A.; Macías, N.; Cardona, P.; Quesada, H.; Rubio, F.; Cano, L.; Lara, B.; de Miquel, M. A.; Aja, L.; Serena, J.; Cobo, E.; Lees, Kennedy R.; Arenillas, J.; Roberts, R.; Al-Ajlan, F.; Zimmel, L.; Patel, S.; Martí-Fàbregas, J.; Salvat-Plana, M.; Bracard, S.; Anxionnat, René; Baillot, Pierre-Alexandre; Barbier, Charlotte; Derelle, Anne-Laure; Lacour, Jean-Christophe; Richard, Sébastien; Samson, Yves; Sourour, Nader; Baronnet-Chauvet, Flore; Clarencon, Frédéric; Crozier, Sophie; Deltour, Sandrine; Di Maria, Federico; Le Bouc, Raphael; Leger, Anne; Mutlu, Gurkan; Rosso, Charlotte; Szatmary, Zoltan; Yger, Marion; Zavanone, Chiara; Bakchine, Serge; Pierot, Laurent; Caucheteux, Nathalie; Estrade, Laurent; Kadziolka, Krzysztof; Leautaud, Alexandre; Renkes, Céline; Serre, Isabelle; Desal, Hubert; Guillon, Benoît; Boutoleau-Bretonniere, Claire; Daumas-Duport, Benjamin; de Gaalon, Solène; Derkinderen, Pascal; Evain, Sarah; Herisson, Fanny; Laplaud, David-Axel; Lebouvier, Thibaud; Lintia-Gaultier, Alina; Pouclet-Courtemanche, Hélène; Rouaud, Tiphaine; Rouaud Jaffrenou, Violaine; Schunck, Aurélia; Sevin-Allouet, Mathieu; Toulgoat, Frederique; Wiertlewski, Sandrine; Gauvrit, Jean-Yves; Ronziere, Thomas; Cahagne, Vincent; Ferre, Jean-Christophe; Pinel, Jean-François; Raoult, Hélène; Mas, Jean-Louis; Meder, Jean-François; Al Najjar-Carpentier, Amen-Adam; Birchenall, Julia; Bodiguel, Eric; Calvet, David; Domigo, Valérie; Godon-Hardy, Sylvie; Guiraud, Vincent; Lamy, Catherine; Majhadi, Loubna; Morin, Ludovic; Trystram, Denis; Turc, Guillaume; Berge, Jérôme; Sibon, Igor; Menegon, Patrice; Barreau, Xavier; Rouanet, François; Debruxelles, Sabrina; Kazadi, Annabelle; Renou, Pauline; Fleury, Olivier; Pasco-Papon, Anne; Dubas, Frédéric; Caroff, Jildaz; Godard Ducceschi, Sophie; Hamon, Marie-Aurélie; Lecluse, Alderic; Marc, Guillaume; Giroud, Maurice; Ricolfi, Frédéric; Bejot, Yannick; Chavent, Adrien; Gentil, Arnaud; Kazemi, Apolline; Osseby, Guy-Victor; Voguet, Charlotte; Mahagne, Marie-Hélène; Sedat, Jacques; Chau, Yves; Suissa, Laurent; Lachaud, Sylvain; Houdart, Emmanuel; Stapf, Christian; Buffon Porcher, Frédérique; Chabriat, Hugues; Guedin, Pierre; Herve, Dominique; Jouvent, Eric; Mawet, Jérôme; Saint-Maurice, Jean-Pierre; Schneble, Hans-Martin; Nighoghossian, Norbert; Berhoune, Nadia-Nawel; Bouhour, Françoise; Cho, Tae-Hee; Derex, Laurent; Felix, Sandra; Gervais-Bernard, Hélène; Gory, Benjamin; Manera, Luis; Mechtouff, Laura; Ritzenthaler, Thomas; Riva, Roberto; Salaris Silvio, Fabrizio; Tilikete, Caroline; Blanc, Raphael; Obadia, Michaël; Bartolini, Mario Bruno; Gueguen, Antoine; Piotin, Michel; Pistocchi, Silvia; Redjem, Hocine; Drouineau, Jacques; Neau, Jean-Philippe; Godeneche, Gaelle; Lamy, Matthias; Marsac, Emilia; Velasco, Stephane; Clavelou, Pierre; Chabert, Emmanuel; Bourgois, Nathalie; Cornut-Chauvinc, Catherine; Ferrier, Anna; Gabrillargues, Jean; Jean, Betty; Marques, Anna-Raquel; Vitello, Nicolas; Detante, Olivier; Barbieux, Marianne; Boubagra, Kamel; Favre Wiki, Isabelle; Garambois, Katia; Tahon, Florence; Ashok, Vasdev; Coskun, Oguzhan; Rodesch, Georges; Lapergue, Bertrand; Bourdain, Frédéric; Evrard, Serge; Graveleau, Philippe; Decroix, Jean Pierre; Wang, Adrien; Sellal, François; Ahle, Guido; Carelli, Gabriela; Dugay, Marie-Hélène; Gaultier, Claude; Lebedinsky, Ariel Pablo; Lita, Lavinia; Musacchio, Raul Mariano; Renglewicz-Destuynder, Catherine; Tournade, Alain; Vuillemet, Françis; Montoro, Francisco Macian; Mounayer, Charbel; Faugeras, Frederic; Gimenez, Laetitia; Labach, Catherine; Lautrette, Géraldine; Denier, Christian; Saliou, Guillaume; Chassin, Olivier; Dussaule, Claire; Melki, Elsa; Ozanne, Augustin; Puccinelli, Francesco; Sachet, Marina; Sarov, Mariana; Bonneville, Jean-François; Moulin, Thierry; Biondi, Alessandra; de Bustos Medeiros, Elisabeth; Vuillier, Fabrice; Courtheoux, Patrick; Viader, Fausto; Apoil-Brissard, Marion; Bataille, Mathieu; Bonnet, Anne-Laure; Cogez, Julien; Touze, Emmanuel; Leclerc, Xavier; Leys, Didier; Aggour, Mohamed; Aguettaz, Pierre; Bodenant, Marie; Cordonnier, Charlotte; Deplanque, Dominique; Girot, Marie; Henon, Hilde; Kalsoum, Erwah; Lucas, Christian; Pruvo, Jean-Pierre; Zuniga, Paolo; Arquizan, Caroline; Costalat, Vincent; Machi, Paolo; Mourand, Isabelle; Riquelme, Carlos; Bounolleau, Pierre; Arteaga, Charles; Faivre, Anthony; Bintner, Marc; Tournebize, Patrice; Charlin, Cyril; Darcel, Françoise; Gauthier-Lasalarie, Pascale; Jeremenko, Marcia; Mouton, Servane; Zerlauth, Jean-Baptiste; Lamy, Chantal; Hervé, Deramond; Hassan, Hosseini; Gaston, André; Barral, Francis-Guy; Garnier, Pierre; Beaujeux, Rémy; Wolff, Valérie; Herbreteau, Denis; Debiais, Séverine; Murray, Alicia; Ford, Gary; Clifton, Andy; Freeman, Janet; Ford, Ian; Markus, Hugh; Wardlaw, Joanna; Molyneux, Andy; Robinson, Thompson; Lewis, Steff; Norrie, John; Robertson, Fergus; Perry, Richard; Cloud, Geoffrey; Clifton, Andrew; Madigan, Jeremy; Roffe, Christine; Nayak, Sanjeev; Lobotesis, Kyriakos; Smith, Craig; Herwadkar, Amit; Kandasamy, Naga; Goddard, Tony; Bamford, John; Subramanian, Ganesh; Lenthall, Rob; Littleton, Edward; Lamin, Sal; Storey, Kelley; Ghatala, Rita; Banaras, Azra; Aeron-Thomas, John; Hazel, Bath; Maguire, Holly; Veraque, Emelda; Harrison, Louise; Keshvara, Rekha; Cunningham, James

    2018-01-01

    Background General anaesthesia (GA) during endovascular thrombectomy has been associated with worse patient outcomes in observational studies compared with patients treated without GA. We assessed functional outcome in ischaemic stroke patients with large vessel anterior circulation occlusion

  17. Long-term trend in ground-based air temperature and its responses to atmospheric circulation and anthropogenic activity in the Yangtze River Delta, China

    Science.gov (United States)

    Peng, Xia; She, Qiannan; Long, Lingbo; Liu, Min; Xu, Qian; Zhang, Jiaxin; Xiang, Weining

    2017-10-01

    The Yangtze River Delta (YRD), including Shanghai City, Jiangsu and Zhejiang Provinces, is the largest metropolitan region in China. In the past decades, the region has experienced massive urbanization and detrimentally affected the environment in the region. Identifying the spatio-temporal variations of climate change and its influencing mechanism in the YRD is an important task for assessing their impacts on the local society and ecosystem. Based on long-term (1958-2014) observation data of meteorological stations, three temperature indices, i.e. extreme maximum temperature (TXx), extreme minimum temperature (TNn), and mean temperature (TMm), were selected and spatialized with climatological calculations and spatial techniques. Evolution and spatial heterogeneity of three temperature indices over YRD as well as their links to atmospheric circulation and anthropogenic activity were investigated. In the whole YRD, a statistically significant overall uptrend could be detected in three temperature indices with the Mann-Kendall (M-K) trend test method. The linear increasing trend for TMm was 0.31 °C/10 a, which was higher than the global average (0.12 °C/10 a during 1951-2012). For TXx and TNn, the increasing rates were 0.41 °C/10 a and 0.52 °C/10 a. Partial correlation analysis indicated that TMm was more related with TXx (rp = 0.68, p < 0.001) than TNn (rp = 0.48, p < 0.001). Furthermore, it was detected with M-K analysis at pixel scale that 62.17%, 96.75% and 97.05% of the areas in the YRD showed significant increasing trends for TXx, TNn and TMm, respectively. The increasing trend was more obvious in the southern mountainous areas than the northern plains areas. Further analysis indicated that the variation of TXx over YRD was mainly influenced by anthropogenic activities (e.g. economic development), while TNn was more affected by atmospheric circulations (e.g., the Eurasian zonal circulation index (EAZ) and the cold air activity index (CA)). For TMm, it was a

  18. Identification and frequency of atmospheric circulation patterns causing spring frost in the northern French vineyards using the objective version of the Hess-Brezowsky classification

    Science.gov (United States)

    Quénol, H.; Planchon, O.; Wahl, L.

    2009-04-01

    frosts (until June). In the Loire Valley area, frost is rare as early as April. The combined effects of the continentality and the topographical features of the Upper Rhine Graben explain the hard frosts in early spring at Colmar, but also higher temperature at Colmar than at Reims from April. The Champagne area is the most exposed to frost-producing North-Westerly and Northerly atmospheric circulations in late spring (e.g. on May the 5th, 1996: minimum temperature of -1°C at Reims / Champagne and +3.8°C at Colmar). The identification and frequency of atmospheric circulation patterns causing spring frost (daily minimum temperature below 0°C) and hard frost (daily minimum temperature below -5°C) were carried out using the objective computational version of the 29-type Hess and Brezowsky Grosswetterlagen system of classifying European synoptic regimes (James, 2007). Minimum temperature data were got from the Meteo-France database (Climathèque), for the spring months (March, April and May) and for the period 1960-2007, at the weather stations of Saumur (Loire Valley), Reims (Champagne), Dijon (Burgundy) and Colmar (Alsace). More than 40% of the frost days occurring at all weather stations were associated with North-Westerly and Northerly circulation types, 27% with North-Easterly and Easterly circulation types and 16% with a main high or low pressure area over central Europe. More precisely, the cyclonic circulations involving a northerly flow over western Europe (15.6%) and Anticyclonic North-Easterly circulations (9,3%) are the most frequent circulations types associated with frost days. These circulation types bring air-masses favourable to radiation cooling, under clear sky and light wind, or cold air-masses from northern or eastern Europe causing advection cooling. The stations of eastern France can be subjected to frost events even during Westerly or Southerly circulations, while frost occurrence in the Saumur area requires a higher ratio of North-Easterly and

  19. Solar and geomagnetic effects on the frequency of atmospheric circulation types over Europe: an analysis based on a large number of classifications

    Science.gov (United States)

    Huth, Radan; Cahynová, Monika; Kyselý, Jan

    2010-05-01

    Recently, effects of the 11-year solar cycle on various aspects of tropospheric circulation in the Northern Hemisphere in winter have been recognized. One of our previous studies showed a significant solar effect on the frequency of synoptic types from the Hess-Brezowsky catalogue. Here, we use a large collection of varied classifications of circulation patterns, assembled within the COST733 Action "Harmonization and Applications of Weather Types Classifications for European Regions" to detect the solar effect on the frequency of synoptic types. The collection contains both objective and subjective classifications. The advantage of this multi-classification approach is that peculiarities or biases of any single classification (catalogue) that might influence the detected solar signal vanish once a large ensemble of classifications is used. We divide winter months (December to March) into three groups according to the mean monthly solar activity, quantified by the F10.7 flux. The three groups correspond to the minima of the 11-year solar cycle, a moderate solar activity, and solar maxima. Within each group, frequencies of occurrence of individual circulation types are calculated. Differences in the occurrence of individual classes between solar activity groups indicate the presence of a solar activity effect on atmospheric circulation over Europe. Statistical significance of these differences is estimated by a block resampling method. The research is supported by the Grant Agency of the Czech Academy of Sciences, project A300420805, and by the Ministry of Education, Youth, and Sports of the Czech Republic, contract OC115.

  20. The climatology of carbon monoxide and water vapor on Mars as observed by CRISM and modeled by the GEM-Mars general circulation model

    Science.gov (United States)

    Smith, Michael D.; Daerden, Frank; Neary, Lori; Khayat, Alain

    2018-02-01

    Radiative transfer modeling of near-infrared spectra taken by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) instrument onboard Mars Reconnaissance Orbiter (MRO) enables the column-integrated abundance of carbon monoxide (CO) and water vapor (H2O) to be retrieved. These results provide a detailed global description of the seasonal and spatial distribution of CO in the Mars atmosphere and new information about the interannual variability of H2O. The CRISM retrievals show the seasonally and globally averaged carbon monoxide mixing ratio to be near 800 ppm, but with strong seasonal variations, especially at high latitudes. At low latitudes, the carbon monoxide mixing ratio varies in response to the mean seasonal cycle of surface pressure and shows little variation with topography. At high latitudes, carbon monoxide is depleted in the summer hemisphere by a factor of two or more, while in the winter hemisphere there is relatively higher mixing ratio in regions with low-lying topography. Water vapor shows only modest interannual variations, with the largest observed difference being unusually dry conditions in the wake of the Mars Year 28 global dust storm. Modeling results from the GEM-Mars general circulation model generally reproduce the observed seasonal and spatial trends and provide insight into the underlying physical processes.

  1. Probabilistic multi-model ensemble prediction of Indian summer monsoon rainfall using general circulation models: A non-parametric approach

    Science.gov (United States)

    Acharya, Nachiketa; Mohanty, Uma Charan; Sahoo, Lokanath

    2013-03-01

    Probabilistic prediction has the ability to convey the intrinsic uncertainty of forecast that helps the decision makers to manage the climate risk more efficiently than deterministic forecasts. In recent times, probabilistic predictions obtained from the products from General Circulation Models (GCMs) have gained considerable attention. The probabilistic forecast can be generated in parametric (assuming Gaussian distribution) as well as non-parametric (counting method) ways. The present study deals with the non-parametric approach that requires no assumption about the form of the forecast distribution for the prediction of Indian summer monsoon rainfall (ISMR) based on the hindcast run of seven general circulation models from 1982 to 2008. Probabilistic prediction from each of the GCM products has been generated by non-parametric methods for tercile categories (viz. below normal (BN), near-normal (NN), and above normal (AN)) and evaluation of their skill is assessed against observed data. Five different types of PMME schemes have been used for combining probabilities from each GCM to improve the forecast skill as compared to the individual GCMs. These schemes are different in nature of assigning the weights for combining probabilities. After a rigorous analysis through Rank Probability Skill Score (RPSS) and relative operating characteristic (ROC) curve, the superiority of PMME has been established over climatological probability. It is also found that, the performances of PMME1 and PMME3 are better than all the other methods whereas PMME3 has showed more improvement over PMME1.

  2. Links Between Flood Events In Central Europe Since Ad 1500 and The Large-scale Atmospheric Circulation

    Science.gov (United States)

    Jacobeit, J.; Glaser, R.

    Based on historical climatic data bank information compiled by Glaser (2001) inci- dence variations of flood events can be reconstructed back to AD 1500 for several catchment areas in Central Europe. Based on gridded SLP data reconstructed back to AD 1500 by Luterbacher et al. (University of Berne) links to the large-scale atmo- spheric circulation may be identified on climatic time scales (monthly to seasonal). For this purpose several indices have been calculated describing the particular im- portance of different circulation patterns as a dynamical background for the varying incidence of flood events. For example, zonal circulation patterns cover the greatest part of these events, in relation to the pattern frequency, however, other circulation modes come to the fore during historical periods of increased flood frequency, e.g. modes characterised by Atlantic low and Russian high pressure centres during win- ter. Additionally, modifications in large-scale circulation patterns have been identified between periods with and without flood events as well as between periods with in- creased and decreased flood frequency, respectively. In particular shifts from westerly types to southwesterly or cyclonic wave patterns could be substantiated for months with historical flood events during winter.

  3. Effect of AMOC collapse on ENSO in a high resolution general circulation model

    Science.gov (United States)

    Williamson, Mark S.; Collins, Mat; Drijfhout, Sybren S.; Kahana, Ron; Mecking, Jennifer V.; Lenton, Timothy M.

    2017-06-01

    We look at changes in the El Niño Southern Oscillation (ENSO) in a high-resolution eddy-permitting climate model experiment in which the Atlantic Meridional Circulation (AMOC) is switched off using freshwater hosing. The ENSO mode is shifted eastward and its period becomes longer and more regular when the AMOC is off. The eastward shift can be attributed to an anomalous eastern Ekman transport in the mean equatorial Pacific ocean state. Convergence of this transport deepens the thermocline in the eastern tropical Pacific and increases the temperature anomaly relaxation time, causing increased ENSO period. The anomalous Ekman transport is caused by a surface northerly wind anomaly in response to the meridional sea surface temperature dipole that results from switching the AMOC off. In contrast to a previous study with an earlier version of the model, which showed an increase in ENSO amplitude in an AMOC off experiment, here the amplitude remains the same as in the AMOC on control state. We attribute this difference to variations in the response of decreased stochastic forcing in the different models, which competes with the reduced damping of temperature anomalies. In the new high-resolution model, these effects approximately cancel resulting in no change in amplitude.

  4. Modelling atmospheric circulations for the study of Alpine valleys pollution; Modelisation des circulations atmospheriques pour l'etude de la pollution des vallees alpines

    Energy Technology Data Exchange (ETDEWEB)

    Brulfert, G.

    2004-11-15

    Local weather phenomena observed in alpine valleys frequently lead to the accumulation of emitted anthropogenic airborne species in the low layers of the atmosphere. The development of a numerical model allows reproducing the chemical evolution of air mass during POVA intensive period of observations. In Chamonix and Maurienne valley, computations of photochemical indicators (NO{sub y}, O{sub 3}/NO{sub z}, H{sub 2}O{sub 2}/HNO{sub 3}) prove the ozone regime to be control by volatile organic compounds. Moreover simulation highlighted that the major part of this secondary pollutant is regionally produced. The development of an indicator who localised ozone production sites can help to define abatement scenarios. The chemical mechanism RACM allows describing the evolution of many species. It is possible to conclude that in winter road traffic and heating are the main sources of volatile organic compounds. (author)

  5. Explaining the mechanisms through which regional atmospheric circulation variability drives summer temperatures and glacial melt in western High Mountain Asia (HMA)

    Science.gov (United States)

    Forsythe, Nathan; Fowler, Hayley; Blenkinsop, Stephen; Li, Xiaofeng; Pritchard, David

    2017-04-01

    Comprehension of mechanisms by which atmospheric circulation influences sub-regional temperature and water resources variability in high-elevation mountainous catchments is of great scientific urgency due to the dependency of large downstream populations on the river flows these basins provide. In this work we quantify a regional atmospheric pattern, the Karakoram Zonal Shear (KZS), with a very pronounced annual cycle which we standardise into a dimensionless (seasonal) circulation metric the Karakoram Zonal Index (KZI). Going beyond previous regional circulation metrics such as the "middle-upper tropospheric temperature index" (MUTTI) or the Webster and Yang Monsoonal Index (WYMI) which have focused solely on the South Asian Summer Monsoon (June to September) season, the KZS/KZI provides an indicator which captures the influence and interactions of the westerly jet throughout the entire annual cycle. Use of the KZS and KZI have led us to identify a further regional atmospheric system, the Karakoram Vortex, which propagates "warm high" (anticyclonic postitive temperature anomaly) and "cold low" (cyclonic negative temperature anomaly) patterns across a very broad swath of Central and South Asia in winter but over a much more constrained area of western HMA in summer. The KV exerts this temperature influence through a combination of adiabatic effects and large-scale advection. Quantify KV influence, the KZI shows strong and statistically significantly near surface (2m) air temperatures both across western HMA both as observed through local meteorological stations and as estimated by an ensemble of global meteorological reanalyses. We show that this strong influence on temperature translates to important consequences for meltwater generation from highly glaciated Indus river tributaries which is logical given that previous studies have established the role of air temperature in modulating glacially-derived river flows in western HMA. By improving the understanding of

  6. Constraints on Climate and Habitability for Earth-like Exoplanets Determined from a General Circulation Model

    Science.gov (United States)

    Wolf, Eric T.; Shields, Aomawa L.; Kopparapu, Ravi K.; Haqq-Misra, Jacob; Toon, Owen B.

    2017-03-01

    Conventional definitions of habitability require abundant liquid surface water to exist continuously over geologic timescales. Water in each of its thermodynamic phases interacts with solar and thermal radiation and is the cause for strong climatic feedbacks. Thus, assessments of the habitable zone require models to include a complete treatment of the hydrological cycle over geologic time. Here, we use the Community Atmosphere Model from the National Center for Atmospheric Research to study the evolution of climate for an Earth-like planet at constant CO2, under a wide range of stellar fluxes from F-, G-, and K-dwarf main sequence stars. Around each star we find four stable climate states defined by mutually exclusive global mean surface temperatures (T s); snowball (T s ≤ 235 K), waterbelt (235 K ≤ T s ≤ 250 K), temperate (275 K ≤ T s ≤ 315 K), and moist greenhouse (T s ≥ 330 K). Each is separated by abrupt climatic transitions. Waterbelt, temperate, and cooler moist greenhouse climates can maintain open-ocean against both sea ice albedo and hydrogen escape processes respectively, and thus constitute habitable worlds. We consider the warmest possible habitable planet as having T s ˜ 355 K, at which point diffusion limited water-loss could remove an Earth ocean in ˜1 Gyr. Without long timescale regulation of non-condensable greenhouse species at Earth-like temperatures and pressures, such as CO2, habitability can be maintained for an upper limit of ˜2.2, ˜2.4, and ˜4.7 Gyr around F-, G-, and K-dwarf stars respectively, due to main sequence brightening.

  7. Resolving Orbital and Climate Keys of Earth and Extraterrestrial Environments with Dynamics (ROCKE-3D) 1.0: A General Circulation Model for Simulating the Climates of Rocky Planets

    Energy Technology Data Exchange (ETDEWEB)

    Way, M. J.; Aleinov, I.; Amundsen, David S.; Chandler, M. A.; Genio, A. D. Del; Fujii, Y.; Kelley, M.; Kiang, N. Y.; Sohl, L.; Tsigaridis, K. [NASA Goddard Institute for Space Studies, New York, NY 10025 (United States); Clune, T. L. [Global Modeling and Assimilation Office, NASA Goddard Space Flight Center (United States)

    2017-07-01

    Resolving Orbital and Climate Keys of Earth and Extraterrestrial Environments with Dynamics (ROCKE-3D) is a three-dimensional General Circulation Model (GCM) developed at the NASA Goddard Institute for Space Studies for the modeling of atmospheres of solar system and exoplanetary terrestrial planets. Its parent model, known as ModelE2, is used to simulate modern Earth and near-term paleo-Earth climates. ROCKE-3D is an ongoing effort to expand the capabilities of ModelE2 to handle a broader range of atmospheric conditions, including higher and lower atmospheric pressures, more diverse chemistries and compositions, larger and smaller planet radii and gravity, different rotation rates (from slower to more rapid than modern Earth’s, including synchronous rotation), diverse ocean and land distributions and topographies, and potential basic biosphere functions. The first aim of ROCKE-3D is to model planetary atmospheres on terrestrial worlds within the solar system such as paleo-Earth, modern and paleo-Mars, paleo-Venus, and Saturn’s moon Titan. By validating the model for a broad range of temperatures, pressures, and atmospheric constituents, we can then further expand its capabilities to those exoplanetary rocky worlds that have been discovered in the past, as well as those to be discovered in the future. We also discuss the current and near-future capabilities of ROCKE-3D as a community model for studying planetary and exoplanetary atmospheres.

  8. Resolving Orbital and Climate Keys of Earth and Extraterrestrial Environments with Dynamics (ROCKE-3D) 1.0: A General Circulation Model for Simulating the Climates of Rocky Planets

    Science.gov (United States)

    Way, M. J.; Aleinov, I.; Amundsen, David S.; Chandler, M. A.; Clune, T. L.; Del Genio, A.; Fujii, Y.; Kelley, M.; Kiang, N. Y.; Sohl, L.; hide

    2017-01-01

    Resolving Orbital and Climate Keys of Earth and Extraterrestrial Environments with Dynamics (ROCKE-3D) is a three-dimensional General Circulation Model (GCM) developed at the NASA Goddard Institute for Space Studies for the modeling of atmospheres of solar system and exoplanetary terrestrial planets. Its parent model, known as ModelE2, is used to simulate modern Earth and near-term paleo-Earth climates. ROCKE-3D is an ongoing effort to expand the capabilities of ModelE2 to handle a broader range of atmospheric conditions, including higher and lower atmospheric pressures, more diverse chemistries and compositions, larger and smaller planet radii and gravity, different rotation rates (from slower to more rapid than modern Earth's, including synchronous rotation), diverse ocean and land distributions and topographies, and potential basic biosphere functions. The first aim of ROCKE-3D is to model planetary atmospheres on terrestrial worlds within the solar system such as paleo-Earth, modern and paleo-Mars, paleo-Venus, and Saturn's moon Titan. By validating the model for a broad range of temperatures, pressures, and atmospheric constituents, we can then further expand its capabilities to those exoplanetary rocky worlds that have been discovered in the past, as well as those to be discovered in the future. We also discuss the current and near-future capabilities of ROCKE-3D as a community model for studying planetary and exoplanetary atmospheres.

  9. [Respiratory symptoms and atmospheric pollution and respiratory symptoms in the general population].

    Science.gov (United States)

    Simon, I; Charpin, D

    2010-06-01

    Epidemiological studies on air pollution have mainly been interested in the effects of short- or long-term exposure on patients suffering from respiratory illnesses. Fewer studies have addressed the acute effects of air pollution on respiratory symptoms in the general population. We conducted a review of the literature over the last 16years that has addressed the impact of atmospheric pollution on respiratory symptoms in the general population to estimate the magnitude of effect. The majority of studies demonstrated a significant association between exposure to air pollutants and the occurrence of respiratory symptoms, without any threshold. Although a link between atmospheric pollution and respiratory symptoms has been demonstrated, knowledge of the effects of specific air pollutants and the effect of pollution on particular vulnerable groups (infants, young children, the elderly) is still limited. There is a need for further studies in this area. Copyright 2010 SPLF. Published by Elsevier Masson SAS. All rights reserved.

  10. A PROPOSAL FOR OBSERVATION OF ATMOSPHERIC CIRCULATION AND TRANSPORT PROCESSES IN THE TROPOSPHERE AND LOWER STRATOSPHERE OVER ANTARCTICA WITH A NETWORK OF WIND PROFILERS

    OpenAIRE

    カンザワ, ヒロシ; Hiroshi, KANZAWA

    1992-01-01

    The wind profiler is a powerful tool to study atmospheric circulation and transport processes because it can measure not only horizontal components but also the vertical component of wind. A wind profiler developed originally by the U.S. NOAA/Environmental Research Laboratories/Wave Propagation Laboratory can measure winds from 0.5-17km above the surface with an altitude resolution of 250m and time resolution under 1 hour. The profiler uses a 400MHz UHF band, and the area of the antenna is ab...

  11. Bioactive factors in uteroplacental and systemic circulation link placental ischemia to generalized vascular dysfunction in hypertensive pregnancy and preeclampsia.

    Science.gov (United States)

    Shah, Dania A; Khalil, Raouf A

    2015-06-15

    Preeclampsia is a pregnancy-associated disorder characterized by hypertension, and could lead to maternal and fetal morbidity and mortality; however, the pathophysiological mechanisms involved are unclear. Predisposing demographic, genetic and environmental risk factors could cause localized abnormalities in uteroplacental cytoactive factors such as integrins, matrix metalloproteinases, cytokines and major histocompatibility complex molecules leading to decreased vascular remodeling, uteroplacental vasoconstriction, trophoblast cells apoptosis, and abnormal development of the placenta. Defective placentation and decreased trophoblast invasion of the myometrium cause reduction in uteroplacental perfusion pressure (RUPP) and placental ischemia/hypoxia, an important event in preeclampsia. RUPP could stimulate the release of circulating bioactive factors such as the anti-angiogenic factors soluble fms-like tyrosine kinase-1 and soluble endoglin that cause imbalance with the pro-angiogenic factors vascular endothelial growth factor and placental growth factor, or cause the release of inflammatory cytokines, reactive oxygen species, hypoxia-induced factor-1 and AT1 angiotensin receptor agonistic autoantibodies. The circulating bioactive factors target endothelial cells causing generalized endotheliosis, endothelial dysfunction, decreased vasodilators such as nitric oxide and prostacyclin and increased vasoconstrictors such as endothelin-1 and thromboxane A2, leading to increased vasoconstriction. The bioactive factors also stimulate the mechanisms of VSM contraction including Ca(2+), protein kinase C, and Rho-kinase and induce extracellular matrix remodeling leading to further vasoconstriction and hypertension. While therapeutic options are currently limited, understanding the underlying mechanisms could help design new interventions for management of preeclampsia. Copyright © 2015 Elsevier Inc. All rights reserved.

  12. Bioactive Factors in Uteroplacental and Systemic Circulation Link Placental Ischemia to Generalized Vascular Dysfunction in Hypertensive Pregnancy and Preeclampsia

    Science.gov (United States)

    Shah, Dania A.; Khalil, Raouf A.

    2015-01-01

    Preeclampsia is a pregnancy-associated disorder characterized by hypertension, and could lead to maternal and fetal morbidity and mortality; however, the pathophysiological mechanisms involved are unclear. Predisposing demographic, genetic and environmental risk factors could cause localized abnormalities in uteroplacental cytoactive factors such as integrins, matrix metalloproteinases, cytokines and major histocompatibility complex molecules leading to decreased vascular remodeling, uteroplacental vasoconstriction, trophoblast cells apoptosis, and abnormal development of the placenta. Defective placentation and decreased trophoblast invasion of the myometrium cause reduction in uteroplacental perfusion pressure (RUPP) and placental ischemia/hypoxia, an important event in preeclampsia. RUPP could stimulate the release of circulating bioactive factors such as the anti-angiogenic factors soluble fms-like tyrosine kinase-1 and soluble endoglin that cause imbalance with the pro-angiogenic factors vascular endothelial growth factor and placental growth factor, or cause the release of inflammatory cytokines, reactive oxygen species, hypoxia-induced factor-1 and AT1 angiotensin receptor agonistic autoantibodies. The circulating bioactive factors target endothelial cells causing generalized endotheliosis, endothelial dysfunction, decreased vasodilators such as nitric oxide and prostacyclin and increased vasoconstrictors such as endothelin-1 and thromboxane A2, leading to increased vasoconstriction. The bioactive factors also stimulate the mechanisms of VSM contraction including Ca2+, protein kinase C, and Rho-kinase and induce extracellular matrix remodeling leading to further vasoconstriction and hypertension. While therapeutic options are currently limited, understanding the underlying mechanisms could help design new interventions for management of preeclampsia. PMID:25916268

  13. Are there differences in atmospheric circulations between a 1.5°C and a 2.0°C warmer world?

    Science.gov (United States)

    Seland Graff, Lise; Bethke, Ingo; Iversen, Trond; Li, Camille

    2017-04-01

    In this presentation, we use a multi-model ensemble of global atmospheric model simulations to examine how the atmospheric circulation at mid-latitudes may change in a world that experiences a warming of 1.5°C and of 2.0°C over pre-industrial conditions. The data are taken from a suite of simulations carried out for the international project "Half a degree Additional Warming, Prognosis and Projected Implications" (HAPPI), coordinated by Oxford and Bristol Universities as a follow-up of the "Paris agreement" of December 2015 (http://www.happimip.org/). The HAPPI data set includes simulation results from several (˜10) atmospheric models, each with 50-100 ensemble members covering 10-year long periods. This large sample size enables assessing the systematic climate response relative to the internal climate variability. We will present results from the present decade, as well as the 1.5°C and 2.0°C experiments. The presentation focuses on data from the interim version of the Norwegian Earth System Model (NorESM1_Happi), but also includes data from the other models participating in the project as they become available. The analysis will mainly focus on changes in extratropical atmospheric circulation patterns, including the jet streams, the mid-latitude storm tracks, and the frequency and duration of blocking events. We would like to acknowledge the contributions of the modeling centers participating in the HAPPI project and the coordinators Myles Allen and Dann Mitchell.

  14. Factors associated with circulating concentrations of irisin in the general population cohort of the ABCD study.

    Science.gov (United States)

    Buscemi, S; Corleo, D; Vasto, S; Buscemi, C; Massenti, M F; Nuzzo, D; Lucisano, G; Barile, A M; Rosafio, G; Maniaci, V; Giordano, C

    2017-10-13

    Animal studies have shown that irisin is a myokine secreted following physical exercise, and that it induces the remodeling of white adipose tissue toward brown adipose tissue. Therefore, a protective role of irisin against obesity, diabetes, and other metabolic and cardiovascular conditions has been hypothesized. However, data in humans are contradictory and few data are available concerning the general population. We aimed to evaluate the association between serum irisin concentrations and habitual physical activity, as well as other metabolic and cardiovascular factors in a general population in a Mediterranean area. We considered 858 consecutive individuals included in the ABCD (Alimentazione, Benessere Cardiovascolare e Diabete) study (ISRCTN15840340), a longitudinal observational single-center study of a cohort representative of the general population of Palermo, Sicily. Irisin serum concentrations (Phoenix Europe, Germany), habitual physical activity (HPA) level, and other blood and clinical variables were measured. The irisin serum concentrations were not normally distributed in the cohort (Shapiro-Wilk test=0.94; P<0.001). A significant association between irisin concentrations and HPA was observed (P<0.001). Irisin concentrations were higher in women than in men (P<0.01), and significantly correlated with serum concentrations of HDL-cholesterol (P<0.05) and hs-C-reactive protein (hs-CRP; P<0.05). Binary logistic regression analysis demonstrated that high (⩾median value) irisin serum concentrations were significantly associated with female gender (OR=1.63; 95%CI=1.16-2.28), high serum hs-CRP concentrations (OR=1.61; 95%CI=1.02-2.54) and the HPA level (OR=1.42; 95%CI=1.02-1.96). Our study confirms, in a cohort of a general population, that irisin concentrations gradually increase with the usual level of habitual physical activity.International Journal of Obesity accepted article preview online, 13 October 2017. doi:10.1038/ijo.2017.255.

  15. Development of Adaptive Mesh Refinement Techniques for an Ocean General Circulation Model

    Science.gov (United States)

    Herrnstein, A.

    2003-12-01

    A problem faced by all computational physicists is the trade off between run time and grid resolution. The number of time steps and cost per time step drastically increases as finer and finer grids are used. In effort to combat this dilemma, research areas such as fluid dynamics use a modeling technique known as Adaptive Mesh Refinement (AMR). This involves increasing grid resolution in localized areas of the domain while preserving the structured nature of the original grid. The concept of AMR has been around for nearly two decades, but only in recent years have software packages become available to aid in many of the details. Atmospheric and ocean models simulate phenomena with motion derived from fluid dynamics. This suggests AMR is feasible for global climate modeling. The success of nested regional models also supports this hypothesis. In this research, techniques are developed which will allow AMR to perform on an existing ocean model known as the Modular Ocean Model (MOM). Of particular interest is the ability to use AMR on a staggered grid with centered differencing numerics. These are two characteristics of MOM which reduce computational noise and run time respectively. To aid AMR implementation, the software package SAMRAI (Structured Adaptive Mesh Refinement Application Infrastructure) is used. Refinement is based on solution gradients and possibly other criteria as needed. In addition, regions of critical topography might be refined if necessary. Current tools include time integrators which implement Leap Frog, Predictor Corrector, and Runge Kutta numerics. Velocities are defined at nodes and all other quantities at cell centers. A bench mark simulation of a barotropic modon will be presented.

  16. Analysis of a general circulation model product. I - Frontal systems in the Brazil/Malvinas and Kuroshio/Oyashio regions

    Science.gov (United States)

    Garzoli, Silvia L.; Garraffo, Zulema; Podesta, Guillermo; Brown, Otis

    1992-01-01

    The general circulation model (GCM) of Semtner and Chervin (1992) is tested by comparing the fields produced by this model with available observations in two western boundary current regions, the Brazil/Malvinas and the Kuroshio/Oyashio confluences. The two sets of data used are the sea surface temperature from satellite observations and the temperature field product from the GCM at levels 1 (12.5 m), 2 (37.5 m), and 6 (160 m). It is shown that the model reproduces intense thermal fronts at the sea surface and in the upper layers (where they are induced by the internal dynamics of the model). The location of the fronts are reproduced in the model within 4 to 5 deg, compared with observations. However, the variability of these fronts was found to be less pronounced in the model than in the observations.

  17. Determination of humidity and temperature fluctuations based on MOZAIC data and parametrisation of persistent contrail coverage for general circulation models

    Directory of Open Access Journals (Sweden)

    K. M. Gierens

    1997-08-01

    Full Text Available Humidity and temperature fluctuations at pressure levels between 166 and 290 hPa on the grid scale of general circulation models for a region covered by the routes of airliners, mainly over the Atlantic, have been determined by evaluation of the data obtained with almost 2000 flights within the MOZAIC programme. It is found that the distributions of the fluctuations cannot be modelled by Gaussian distributions, because large fluctuations appear with a relatively high frequency. Lorentz distributions were used for the analytical representation of the fluctuation distributions. From these a joint probability distribution has been derived for simultaneous temperature and humidity fluctuations. This function together with the criteria for the formation and persistence of contrails are used to derive the maximum possible fractional coverage of persistent contrails in a grid cell of a GCM. This can be employed in a statistical formulation of contrail appearance in a climate model.

  18. Determination of humidity and temperature fluctuations based on MOZAIC data and parametrisation of persistent contrail coverage for general circulation models

    Directory of Open Access Journals (Sweden)

    K. M. Gierens

    Full Text Available Humidity and temperature fluctuations at pressure levels between 166 and 290 hPa on the grid scale of general circulation models for a region covered by the routes of airliners, mainly over the Atlantic, have been determined by evaluation of the data obtained with almost 2000 flights within the MOZAIC programme. It is found that the distributions of the fluctuations cannot be modelled by Gaussian distributions, because large fluctuations appear with a relatively high frequency. Lorentz distributions were used for the analytical representation of the fluctuation distributions. From these a joint probability distribution has been derived for simultaneous temperature and humidity fluctuations. This function together with the criteria for the formation and persistence of contrails are used to derive the maximum possible fractional coverage of persistent contrails in a grid cell of a GCM. This can be employed in a statistical formulation of contrail appearance in a climate model.

  19. Embedding a mixed layer model into an ocean general circulation model of the Atlantic: The importance of surface mixing for heat flux and temperature

    Science.gov (United States)

    Sterl, Andreas; Kattenberg, Arie

    1994-07-01

    A primitive equation ocean general circulation model (OGCM) of the Atlantic is coupled with an explicit mixed layer model (MLM). The coupled model is used to investigate the impact and possible improvement achieved by an MLM on the representation of temperature and heat flux. The MLM improves model performance in regions where mixed layer (ML) formation is governed by wind stirring, which is identified as a major missing process in the OGCM. It is shown that the widely used parameterization of Pacanowski and Philander for the vertical exchange coefficients is not able to properly represent this process. The deepening of the ML by wind stirring leads to temperature and heat flux being in closer agreement with climatology than is the case without MLM. Integrations with a coupled ocean-atmosphere model are needed to show whether this improvement leads to a reduced climate drift in such models. Furthermore, momentum mixing improves the vertical profiles of velocity. The Ekman transport now occurs over the whole depth of the ML instead of just within the upper model layer. Convective adjustment as incorporated in the OGCM already tends to overestimate the depth of the mixed layer in buoyancy-driven situations. Adding the MLM cannot remedy this failure. Thus under these circumstances there are only slight improvments of some model aspects while others become even worse. We conclude that the parameterization of convection has to be improved.

  20. Reconstructing atmospheric circulation over southern New Zealand: Establishment of modern westerly airflow 5500 years ago and implications for Southern Hemisphere Holocene climate change

    Science.gov (United States)

    Turney, C. S. M.; Wilmshurst, J. M.; Jones, R. T.; Wood, J. R.; Palmer, J. G.; Hogg, A. G.; Fenwick, P.; Crowley, S. F.; Privat, K.; Thomas, Z.

    2017-03-01

    Late-twentieth century changes in the intensity and migration of Southern Hemisphere westerly winds have been implicated in spatially complex variability in atmospheric and ocean circulation, and ice-sheet dynamics, across the mid- to high-latitudes. A major uncertainty, however, is whether present day hemispheric-wide symmetrical airflow is representative of past behaviour. Here we report a multi-proxy study from Stewart Island and southern Fiordland, New Zealand (46-47°S) reconstructing Holocene changes at the northern limit of westerly airflow. Increased minerogenic input and a pronounced shift in cool-loving vegetation around 5500 years ago is consistent with the establishment of westerly airflow at this latitude in the southwest Pacific. In marked contrast, stronger winds are reported further south over the subantarctic Auckland (50°S) and Campbell (52°S) Islands from 8000 years ago. Intriguingly, reconstructions from the east Pacific suggest a weakening of core westerly airflow after 8500 years ago, but an expansion along the northern limits sometime after 5500 years ago. Our results suggest similar atmospheric circulation changes have been experienced in the Pacific since 5500 years ago, but indicate an expanded network of sites is needed to comprehensively test the driver(s) and impact(s) of Holocene mid-latitude westerly winds across the Southern Hemisphere.

  1. Hydroclimate variability and regional atmospheric circulation over the past 1,350 years reconstructed from Lake Ohau, New Zealand

    Science.gov (United States)

    Roop, H. A.; Levy, R. H.; Vandergoes, M.; Dunbar, G. B.; Howarth, J. D.; Lorrey, A.; Phipps, S. J.

    2016-12-01

    Comprehensive understanding of natural climate-system dynamics requires high-resolution paleoclimate records extending beyond the instrumental period. This is particularly the case for the sparsely-instrumented Southern Hemisphere mid-latitudes, where the timing and amplitude of regional and hemispheric-scale climatic events are poorly constrained. Here we present a 1,350-year record of hydroclimatic variability and regional circulation derived from an annually laminated sediment record from Lake Ohau, South Island, New Zealand (44.23°S, 169.85°E). The climate of New Zealand is influenced by climatological patterns originating in both the tropics (e.g. El-Niño-Southern Oscillation, Interdecadal Pacific Oscillation) and the Antarctic (Southern Annular Mode, SAM). Utilizing the annually resolved Lake Ohau hydroclimate record in combination with a tree-ring record of summer temperature from Oroko Swamp, New Zealand (Cook et al., 2002), we generate a circulation index for the Western South Island of New Zealand. This index utilizes the temperature and precipitation anomalies defined by the Regional Climate Regime Classification scheme for New Zealand to assign synoptic scale circulation patterns to 25-year intervals from 900-2000 AD. This circulation index shows significant periods of change, most notably 835 - 985 AD when northerly airflow dominated and from 1385 - 1710 AD when strong southerly airflow persisted. Comparisons with regional SAM and ENSO reconstructions show that dry, warm conditions at Lake Ohau are consistently associated with strengthened tropical teleconnections to New Zealand and a positive SAM, while cold and wet conditions are driven by increased southerly airflow and negative phase SAM. A persistent negative SAM dominates the Little Ice Age (LIA; 1385-1710 AD) interval in the Western South Island. This same period coincides with the Northern Hemisphere LIA.

  2. Predictability of 2-year La Niña events in a coupled general circulation model

    Science.gov (United States)

    DiNezio, Pedro N.; Deser, Clara; Okumura, Yuko; Karspeck, Alicia

    2017-03-01

    The predictability of the duration of La Niña is assessed using the Community Earth System Model Version 1 (CESM1), a coupled climate model capable of simulating key features of the El Niño/Southern Oscillation (ENSO) phenomenon, including the multi-year duration of La Niña. Statistical analysis of a 1800 year long control simulation indicates that a strong thermocline discharge or a strong El Niño can lead to La Niña conditions that last 2 years (henceforth termed 2-year LN). This relationship suggest that 2-year LN maybe predictable 18 to 24 months in advance. Perfect model forecasts performed with CESM1 are used to further explore the link between 2-year LN and the "Discharge" and "Peak El Niño" predictors. Ensemble forecasts are initialized on January and July coinciding with ocean states characterized by peak El Niño amplitudes and peak thermocline discharge respectively. Three cases with different magnitudes of these predictors are considered resulting in a total of six ensembles. Each "Peak El Niño" and "Discharge" ensemble forecast consists of 30 or 20 members respectively, generated by adding a infinitesimally small perturbation to the atmospheric initial conditions unique to each member. The forecasts show that the predictability of 2-year LN, measured by the potential prediction utility (PPU) of the Niño -3.4 SST index during the second year, is related to the magnitude of the initial conditions. Forecasts initialized with strong thermocline discharge or strong peak El Niño amplitude show higher PPU than those with initial conditions of weaker magnitude. Forecasts initialized from states characterized by weaker predictors are less predictable, mainly because the ensemble-mean signal is smaller, and therefore PPU is reduced due to the influence of forecast spread. The error growth of the forecasts, measured by the spread of the Niño -3.4 SST index, is independent of the initial conditions and appears to be driven by wind variability over the

  3. Predictability of 2-year La Niña events in a coupled general circulation model

    Science.gov (United States)

    DiNezio, Pedro N.; Deser, Clara; Okumura, Yuko; Karspeck, Alicia

    2017-12-01

    The predictability of the duration of La Niña is assessed using the Community Earth System Model Version 1 (CESM1), a coupled climate model capable of simulating key features of the El Niño/Southern Oscillation (ENSO) phenomenon, including the multi-year duration of La Niña. Statistical analysis of a 1800 year long control simulation indicates that a strong thermocline discharge or a strong El Niño can lead to La Niña conditions that last 2 years (henceforth termed 2-year LN). This relationship suggest that 2-year LN maybe predictable 18 to 24 months in advance. Perfect model forecasts performed with CESM1 are used to further explore the link between 2-year LN and the "Discharge" and "Peak El Niño" predictors. Ensemble forecasts are initialized on January and July coinciding with ocean states characterized by peak El Niño amplitudes and peak thermocline discharge respectively. Three cases with different magnitudes of these predictors are considered resulting in a total of six ensembles. Each "Peak El Niño" and "Discharge" ensemble forecast consists of 30 or 20 members respectively, generated by adding a infinitesimally small perturbation to the atmospheric initial conditions unique to each member. The forecasts show that the predictability of 2-year LN, measured by the potential prediction utility (PPU) of the Niño-3.4 SST index during the second year, is related to the magnitude of the initial conditions. Forecasts initialized with strong thermocline discharge or strong peak El Niño amplitude show higher PPU than those with initial conditions of weaker magnitude. Forecasts initialized from states characterized by weaker predictors are less predictable, mainly because the ensemble-mean signal is smaller, and therefore PPU is reduced due to the influence of forecast spread. The error growth of the forecasts, measured by the spread of the Niño-3.4 SST index, is independent of the initial conditions and appears to be driven by wind variability over the

  4. Dominant Large-Scale Atmospheric Circulation Systems for the Extreme Precipitation over the Western Sichuan Basin in Summer 2013

    Directory of Open Access Journals (Sweden)

    Yamin Hu

    2015-01-01

    Full Text Available The western Sichuan Basin (WSB is a rainstorm center influenced by complicated factors such as topography and circulation. Based on multivariable empirical orthogonal function technique for extreme precipitation processes (EPP in WSB in 2013, this study reveals the dominant circulation patterns. Results indicate that the leading modes are characterized by “Saddle” and “Sandwich” structures, respectively. In one mode, a TC from the South China Sea (SCS converts into the inverted trough and steers warm moist airflow northward into the WSB. At the same time, WPSH extends westward over the Yangtze River and conveys a southeasterly warm humid flow. In the other case, WPSH is pushed westward by TC in the Western Pacific and then merges with an anomalous anticyclone over SCS. The anomalous anticyclone and WPSH form a conjunction belt and convey the warm moist southwesterly airflow to meet with the cold flow over the WSB. The configurations of WPSH and TC in the tropic and the blocking and trough in the midhigh latitudes play important roles during the EPPs over the WSB. The persistence of EPPs depends on the long-lived large-scale circulation configuration steady over the suitable positions.

  5. Circulating Aldosterone and Natriuretic Peptides in the General Community: Relationship to Cardiorenal and Metabolic Disease

    Science.gov (United States)

    Buglioni, Alessia; Cannone, Valentina; Cataliotti, Alessandro; Sangaralingham, S. Jeson; Heublein, Denise M.; Scott, Christopher G.; Bailey, Kent R.; Rodeheffer, Richard J.; Dessì-Fulgheri, Paolo; Sarzani, Riccardo; Burnett, John C.

    2014-01-01

    We sought to investigate the role of aldosterone as a mediator of disease and its relationship with the counter-regulatory natriuretic peptide (NP) system. We measured plasma aldosterone (n=1674; age ≥45 years old) in a random sample of the general population from Olmsted County, MN. In a multivariate logistic regression model, aldosterone analyzed as a continuous variable was associated with hypertension (HTN) (OR=1.75, 95%CI= 1.57,1.96; psyndrome (MetS) (OR=1.41, 95%CI= 1.26,1.58; pcardiorenal and metabolic disease. Further studies are warranted to evaluate a therapeutic and preventive strategy to delay the onset and/or progression of disease, using mineralocorticoid antagonists or chronic NP administration in high risk subjects identified by plasma aldosterone. PMID:25368032

  6. Influenza virus but not MERS coronavirus circulation in Iran, 2013-2016: Comparison between pilgrims and general population.

    Science.gov (United States)

    Yavarian, Jila; Shafiei Jandaghi, Nazanin Zahra; Naseri, Maryam; Hemmati, Peyman; Dadras, Mohhamadnasr; Gouya, Mohammad Mehdi; Mokhtari Azad, Talat

    2017-10-12

    The pilgrimage to Mecca and Karbala bring many Muslims to a confined area. Respiratory tract infections are the most common diseases transmitted during mass gatherings in Hajj, Umrah and Karbala. The aim of this study was to determine and compare the prevalence of Middle East respiratory syndrome coronavirus (MERS-CoV) and influenza virus infections among Iranian general population and pilgrims with severe acute respiratory infections (SARI) returning from Mecca and Karbala during 2013-2016. During 2013-2016, a total of 42351 throat swabs were examined for presence of influenza viruses and MERS-CoV in Iranian general population and pilgrims returning from Mecca and Karbala with SARI by using one step RT-PCR kit. None of the patients had MERS-CoV but influenza viruses were detected in 12.7% with high circulation of influenza A/H1N1 (47.1%). This study showed the prevalence of influenza infections among Iranian pilgrims and general population and suggests continuing surveillance, infection control and appropriate vaccination especially nowadays that the risk of influenza pandemic threatens the world, meanwhile accurate screening for MERS-CoV is also recommended. Copyright © 2017 Elsevier Ltd. All rights reserved.

  7. A General Model of the Atmospheric Scattering in the Wavelength Interval 300 - 1100nm

    Directory of Open Access Journals (Sweden)

    K. Dimitrov

    2009-12-01

    Full Text Available We have presented and developed new theoretic-empirical models of the extinction coefficients of the molecular scattering in the lower, close to the ground troposphere. We have included the indicatrices of backscattering. The models have been presented using general analytical functions valid for the whole wavelength interval 300-1100 nm and for the whole interval of visibility from 0.1 km up to 50 km. The results have been compared in quantity with the model and experimental data of other authors. The modeling of troposphere scattering is necessary for the analysis and design of all optoelectronic free space systems: atmospheric optical communication systems, location systems for atmospheric research (LIDAR, optical radiometric systems.

  8. The occurrence of hot weather in the Lublin-Felin and Czesławice in relation to atmospheric circulation (1966–2010

    Directory of Open Access Journals (Sweden)

    Bartoszek Krzysztof

    2016-03-01

    Full Text Available The occurrence of hot weather in the Lublin-Felin and Czesławice in relation to atmospheric circulation (1966−2010. The paper describes the occurrence of hot (tmax 25.1−30.0°C and very hot days (tmax >30°C in Lublin-Felin and Czesławice in the years 1966−2010. The analysis covers the long-term variability of such days, and duration of heat waves. Their circulation conditions were also determined, with indication of circulation types during which the probability of occurrence of hot and very hot days was the highest. In the study area, hot days occurred from April to September, and very hot days from May to August, with the highest frequency in July in both cases. In the period from 1991 to 2010, a considerably higher number of cases of very hot days were recorded than in the 1970s and 1980s. Moreover, they occurred in increasingly long sequences, contributing to more frequent occurrence of unfavourable thermal and humid conditions during the growing season of plants. The highest probability of occurrence of hot and very hot days was determined for circulation types with airflow from the southern sector, and the lowest from the northern sector. Should the upward trend in the frequency of very hot days continue, the risk of the effect of such unfavourable thermal conditions on the health and well-being of tourists and patients of the health resort in Nałęczów will also increase

  9. IL-33 circulating serum levels are increased in patients with non-segmental generalized vitiligo.

    Science.gov (United States)

    Vaccaro, Mario; Cicero, Francesca; Mannucci, Carmen; Calapai, Gioacchino; Spatari, Giovanna; Barbuzza, Olga; Cannavò, Serafinella P; Gangemi, Sebastiano

    2016-09-01

    IL-33 is a recently identified cytokine, encoded by the IL-33 gene, which is a member of the IL-1 family that drives the production of T-helper-2 (Th-2)-associated cytokines. Serum levels of IL-33 have been reported to be up-regulated in various T-helper (Th)-1/Th-17-mediated diseases, such as psoriasis, rheumatoid arthritis, and inflammatory bowel. To investigate whether cytokine imbalance plays a role in the pathogenesis of vitiligo, we performed a case-control association study by enzyme-linked immunosorbent assay of IL-33 in our patients. IL-33 serum levels were measured by a quantitative enzyme immunoassay technique in patients with non-segmental generalized vitiligo and compared with those of healthy controls. IL-33 serum levels in patients with vitiligo were significantly increased than those in healthy controls. There was a positive correlation of IL-33 serum levels with extension of vitiligo and disease activity. This study suggests a possible systemic role of IL-33 in the pathogenesis of vitiligo. Inhibiting IL-33 activity might be a novel therapeutic strategy in the treatment of autoimmune inflammatory disease, like vitiligo.

  10. Novel formulation of the ℳ model through the Generalized-K distribution for atmospheric optical channels.

    Science.gov (United States)

    Garrido-Balsells, José María; Jurado-Navas, Antonio; Paris, José Francisco; Castillo-Vazquez, Miguel; Puerta-Notario, Antonio

    2015-03-09

    In this paper, a novel and deeper physical interpretation on the recently published Málaga or ℳ statistical distribution is provided. This distribution, which is having a wide acceptance by the scientific community, models the optical irradiance scintillation induced by the atmospheric turbulence. Here, the analytical expressions previously published are modified in order to express them by a mixture of the known Generalized-K and discrete Binomial and Negative Binomial distributions. In particular, the probability density function (pdf) of the ℳ model is now obtained as a linear combination of these Generalized-K pdf, in which the coefficients depend directly on the parameters of the ℳ distribution. In this way, the Málaga model can be physically interpreted as a superposition of different optical sub-channels each of them described by the corresponding Generalized-K fading model and weighted by the ℳ dependent coefficients. The expressions here proposed are simpler than the equations of the original ℳ model and are validated by means of numerical simulations by generating ℳ -distributed random sequences and their associated histogram. This novel interpretation of the Málaga statistical distribution provides a valuable tool for analyzing the performance of atmospheric optical channels for every turbulence condition.

  11. Prompt neutrinos from atmospheric charm in the general-mass variable-flavor-number scheme

    Science.gov (United States)

    Benzke, M.; Garzelli, M. V.; Kniehl, B. A.; Kramer, G.; Moch, S.; Sigl, G.

    2017-12-01

    We present predictions for the prompt-neutrino flux arising from the decay of charmed mesons and baryons produced by the interactions of high-energy cosmic rays in the Earth's atmosphere, making use of a QCD approach on the basis of the general-mass variable-flavor-number scheme for the description of charm hadroproduction at NLO, complemented by a consistent set of fragmentation functions. We compare the theoretical results to those already obtained by our and other groups with different theoretical approaches. We provide comparisons with the experimental results obtained by the IceCube Collaboration in two different analyses and we discuss the implications for parton distribution functions.

  12. Shallow Circulations: Relevance and Strategies for Satellite Observation

    Science.gov (United States)

    Bellon, Gilles; Reitebuch, Oliver; Naumann, Ann Kristin

    2017-11-01

    Shallow circulations are central to many tropical cloud systems. We investigate the potential of existing and upcoming data to document these circulations. Different methods to observe or constrain atmospheric circulations rely on satellite-borne instruments. Direct observations of the wind are currently possible at the ocean surface or using tracer patterns. Satellite-borne wind lidar will soon be available, with a much better coverage and accuracy. Meanwhile, circulations can be constrained using satellite observations of atmospheric diabatic heating. We evaluate the commonalities and discrepancies of these estimates together with reanalysis in systems that include shallow circulations. It appears that existing datasets are in qualitative agreement, but that they still differ too much to provide robust evaluation criteria for general circulation models. This state of affairs highlights the potential of satellite-borne wind lidar and of further work on current satellite retrievals.

  13. Regional and Global Climate Effects of US Anthropogenic Aerosols: A Sensitivity Study with a General Circulation Model

    Science.gov (United States)

    Mickley, L. J.; Leibensperger, E. M.; Jacob, D. J.

    2008-12-01

    To improve air quality and reduce acid deposition, United States policymakers are actively reducing the precursor emissions of sulfate and carbonaceous aerosols. Since aerosols are thought to have a net cooling effect, their removal may have unintended consequences for regional and global-scale climate. Using the Goddard Institute for Space Studies General Circulation Model 3, we simulate the direct effect of aerosol removal over the United States. We carry out two 16-year simulations, from 2010 to 2025, following the A1B emissions scenario for the well-mixed greenhouse gases. In our control simulation, aerosol optical depths are fixed at present-day levels, while in our sensitivity simulation, aerosol optical depths over the United States are set to zero. We find that reduction of aerosol optical depths over the United States results in an annually averaged warming over the eastern U.S. of 0.3-1.0° C. This warming is especially pronounced in the winter (1.0-1.5° C) when it is accompanied by a 10-40% increase in precipitation. We also find that removing these pollutants, which are generally only considered as a local problem due to their short lifetimes, has hemispheric-scale effects due to a stronger and northward-shifted Atlantic storm track. In winter, these effects include a cooling of 1.0-2.0° C in the Arctic and northern Canada and a warming of 1.0° C in southeastern Siberia and northern China.

  14. A study of long-term trends in mineral dust aerosol distributions in Asia using a general circulation model

    Science.gov (United States)

    Mukai, Makiko; Nakajima, Teruyuki; Takemura, Toshihiko

    2004-10-01

    Dust events have been observed in Japan with high frequency since 2000. On the other hand, the frequency of dust storms is said to have decreased in the desert regions of China since about the middle of the 1970s. This study simulates dust storms and transportation of mineral dust aerosols in the east Asia region from 1981 to 2001 using an aerosol transport model, Spectral Radiation-Transport Model for Aerosol Species (SPRINTARS), implemented in the Center for Climate System Research/National Institute for Environmental Studies atmospheric global circulation model, in order to investigate the main factors that control a dust event and its long-term variation. The model was forced to simulate a real atmospheric condition by a nudging technique using European Centre for Medium-Range Weather Forecasts reanalysis data on wind velocities, temperature, specific humidity, soil wetness, and snow depth. From a comparison between the long-term change in the dust emission and model parameters, it is found that the wind speed near the surface level had a significant influence on the dust emission, and snow is also an important factor in the early spring dust emission. The simulated results suggested that dust emissions from northeast China have a great impact on dust mass concentration in downwind regions, such as the cities of northeastern China, Korea, and Japan. When the frequency of dust events was high in Japan, a low-pressure system tended to develop over the northeast China region that caused strong winds. From 2000 to 2001 the simulated dust emission flux decreased in the Taklimakan desert and the northwestern part of China, while it increased in the Gobi desert and the northeastern part of China. Consequently, dust particles seem to be transported more from the latter region by prevailing westerlies in the springtime to downwind areas as actually observed. In spite of the similarity, however, there is still a large disagreement between observed and simulated dust

  15. The increase in September precipitation in the Mediterranean region as a result of changes in atmospheric circulation

    Science.gov (United States)

    Nojarov, Peter

    2017-04-01

    The study analyzes changes in September precipitation in the Mediterranean region and their possible causes. The research period is 1950-2014. The main finding is that the reduction in aerosol pollution over Europe in the late twentieth century has led to an upward shift of air temperatures in the region, which in turn has reduced the meridional temperature gradient, leading to weakening and shift to the north of the Azores High (the north end of Hadley circulation). This northward shift placed the Mediterranean region in an area with decreasing SLP, which results in an increase in the number or intensity of cyclones, increase in cloudiness and precipitation and a decrease in air temperatures. In the period 1995-2014 the region (especially its eastern part) lies within the boundaries of Inter Tropical Convergence Zone in September.

  16. Non-stationarities of Mediterranean heavy precipitation events in the second half of the 20th century related to the large-scale atmospheric circulation

    Science.gov (United States)

    Merkenschlager, Christian; Hertig, Elke; Jacobeit, Jucundus

    2015-04-01

    In the context of analysing temporally varying relationships of heavy precipitation events in the Mediterranean area and associated anomalies of the large-scale atmospheric circulation, quantile regression models (QRMs) have been established. Different circulation and thermodynamic variables at the 700hPa and 850hPa levels of the NCEP/NCAR-reanalysis dataset (predictors) as well as daily precipitation time series of different weather stations in the Mediterranean area (predictand) have been used in these regression models. Special emphasis is put on non-stationarities in the relationships of the large-scale atmospheric circulation and heavy precipitation events. Based on rainfall time series tested for homogeneity and completeness, a s-mode principal component analysis (PCA) yields 22 regions of similar precipitation variability for the winter season. The station with the highest PC loading represents the reference station for each region. S-mode PCAs have also been applied to reduce dimensions of the predictor data. The areas of high PC loadings reflect corresponding spatial centres of variation and their time coefficients (scores) are used as predictors in the QRMs. Since the daily precipitation sums are not Gaussian distributed, a three-step censored quantile regression is used to assess the different quantiles. The zero precipitation line represents the censor. By means of the Censored Quantile Verification Skill Score (CQVSS) as a measure of goodness, the best combination of predictor variables can be determined. Mostly, a combination of one thermodynamic predictor and one circulation predictor provides the highest scores whereas an additional predictor does not lead to any significant improvement. In a next step, the number of PCs for both predictors has been determined according to their significance on the level of α=0.01 for every quantile. In the scope of assessing non-stationarities in the predictors-predictand relationships, the time series are divided

  17. Adjustments of a global Finite-Element Sea Ice Ocean Model configuration to improve the general ocean circulation in the North Pacific and its marginal seas.

    Science.gov (United States)

    Scholz, Patrick; Lohmann, Gerrit

    2017-04-01

    The sub-Arctic oceans like the Sea of Okhotsk, the Bering Sea, the Labrador Sea or the Greenland- Irminger-Norwegian (GIN) Sea react particularly sensitive to global climate changes and have the potential to reversely regulate climate change by CO2 uptake in the other areas of the world. So far, the natural processes in the Arctic and Subarctic system, especially over the Pacific realm, remain poorly understood in terms of numerical modeling. As such, in this study we focus on the North Pacific and its adjacent marginal seas (e.g. the Sea of Okhotsk, the Bering Sea and the Sea of Japan), which have nowadays a significant role in the climate system of the Northwest Pacific by influencing the atmospheric and oceanic circulation as well as the hydrology of the Pacific water masses. The Sea of Okhotsk, in particular, is characterized by a highly dynamical sea-ice coverage, where, in autumn and winter, due to massive sea ice formation and brine rejection, the Sea of Okhotsk Intermediate Water (SOIW) is formed which contributes to the mid-depth (500-1000m) water layer of the North Pacific known as newly formed North Pacific Intermediate Water (NPIW). By employing a Finite-Element Sea-Ice Ocean Model (FESOM), in a global configuration, but with high resolution over the marginal seas of the Northwest Pacific Ocean ( 7 km), we tested different meshes and forcing improvements to correct the general ocean circulation in the North Pacific realm towards a more realistic pattern. By using different forcing data (e.g. CORE2, ERA-40/interim, CCMP-correction), adapting the mesh resolutions in the tropical and subtropical North Pacific and changing the bathymetry over important inflow straits (e.g. Amukta Passage, Kruzenstern Strait), we show that the better results are obtained (when compared with observational data) via a combination of CCMP corrected COREv2 forcing with increased resolution in the pathway of the Kuroshio Extension Current and Northern Equatorial Current.

  18. Polynomial Chaos-based Bayesian Inference of K-Profile Parametrization in a General Circulation Model of the Torpical Pacific

    Science.gov (United States)

    Hoteit, I.; Sraj, I.; Zedler, S. E.; Jackson, C. S.; Knio, O. M.

    2016-02-01

    We present a Polynomial Chaos (PC)-based Bayesian inference method for quantifying the uncertainties of K-Profile Parametrization (KPP) model in MIT General Circulation Model (MITgcm). The inference of the uncertain parameters is based on a Markov Chain Monte Carlo (MCMC) scheme that utilizes a newly formulated test statistic taking into account the different components representing the structures of turbulent mixing on both daily and seasonal timescales in addition to the data quality, and filters for the effects of parameter perturbations over those due to changes in the wind. To avoid the prohibitive computational cost of integrating the MITgcm model at each MCMC iteration, we build a surrogate model for the test statistic using the PC method. The traditional spectral projection method for finding the PC coefficients suffered from convergence issues due to the internal noise in the model predictions. Instead, a Basis-Pursuit-DeNoising (BPDN) compressed sensing approach was employed that filtered out the noise and determined the PC coefficients of a representative surrogate model. The PC surrogate is then used to evaluate the test statistic in the MCMC step for sampling the posterior of the uncertain parameters. We present results of the posteriors that indicate a good agreement with the default values for two parameters of the KPP model namely the critical bulk and gradient Richardson; while the posteriors of the remaining parameters were hardly informative.

  19. Discussion on climate oscillations: CMIP5 general circulation models versus a semi empirical harmonic model based on astronomical cycles

    CERN Document Server

    Scafetta, Nicola

    2013-01-01

    Power spectra of global surface temperature (GST) records reveal major periodicities at about 9.1, 10-11, 19-22 and 59-62 years. The Coupled Model Intercomparison Project 5 (CMIP5) general circulation models (GCMs), to be used in the IPCC (2013), are analyzed and found not able to reconstruct this variability. From 2000 to 2013.5 a GST plateau is observed while the GCMs predicted a warming rate of about 2 K/century. In contrast, the hypothesis that the climate is regulated by specific natural oscillations more accurately fits the GST records at multiple time scales. The climate sensitivity to CO2 doubling should be reduced by half, e.g. from the IPCC-2007 2.0-4.5 K range to 1.0-2.3 K with 1.5 C median. Also modern paleoclimatic temperature reconstructions yield the same conclusion. The observed natural oscillations could be driven by astronomical forcings. Herein I propose a semi empirical climate model made of six specific astronomical oscillations as constructors of the natural climate variability spanning ...

  20. A general circulation model study of the climatic effect of observed stratospheric ozone depletion between 1980 and 1990

    Science.gov (United States)

    Dudek, Michael P.; Wang, Wei-Chyung; Liang, Xin-Zhong; Li, Zhu

    1994-01-01

    The total ozone mapping spectrometer (TOMS) and stratospheric aerosol and gas experiment (SAGE) measurements show a significant reduction in the stratospheric ozone over the middle and high latitudes of both hemispheres between the years 1979 and 1991 (WMO, 1992). This change in ozone will effect both the solar and longwave radiation with climate implications. However, recent studies (Ramaswamy et al., 1992; WMO, 1992) indicate that the net effect depends not only on latitudes and seasons, but also on the response of the lower stratospheric temperature. In this study we use a general circulation model (GCM) to calculate the climatic effect due to stratospheric ozone depletion and compare the effect with that due to observed increases of trace gases CO2, CH4, N2O, and CFC's for the period 1980-1990. In the simulations, we use the observed changes in ozone derived from the TOMS data. The GCM used is a version of the NCAR community climate model referenced in Wang et al. (1991). For the present study we run the model in perpetual January and perpetual July modes in which the incoming solar radiation and climatological sea surface temperatures are held constant.

  1. Polynomial Chaos–Based Bayesian Inference of K-Profile Parameterization in a General Circulation Model of the Tropical Pacific

    KAUST Repository

    Sraj, Ihab

    2016-08-26

    The authors present a polynomial chaos (PC)-based Bayesian inference method for quantifying the uncertainties of the K-profile parameterization (KPP) within the MIT general circulation model (MITgcm) of the tropical Pacific. The inference of the uncertain parameters is based on a Markov chain Monte Carlo (MCMC) scheme that utilizes a newly formulated test statistic taking into account the different components representing the structures of turbulent mixing on both daily and seasonal time scales in addition to the data quality, and filters for the effects of parameter perturbations over those as a result of changes in the wind. To avoid the prohibitive computational cost of integrating the MITgcm model at each MCMC iteration, a surrogate model for the test statistic using the PC method is built. Because of the noise in the model predictions, a basis-pursuit-denoising (BPDN) compressed sensing approach is employed to determine the PC coefficients of a representative surrogate model. The PC surrogate is then used to evaluate the test statistic in the MCMC step for sampling the posterior of the uncertain parameters. Results of the posteriors indicate good agreement with the default values for two parameters of the KPP model, namely the critical bulk and gradient Richardson numbers; while the posteriors of the remaining parameters were barely informative. © 2016 American Meteorological Society.

  2. Fluoride pollution of atmospheric precipitation and its relationship with air circulation and weather patterns (Wielkopolski National Park, Poland)

    OpenAIRE

    Walna, Barbara; Kurzyca, Iwona; Bednorz, Ewa; Kolendowicz, Leszek

    2012-01-01

    A 2-year study (2010?2011) of fluorides in atmospheric precipitation in the open area and in throughfall in Wielkopolski National Park (west-central Poland) showed their high concentrations, reaching a maximum value of 2?mg/l under the tree crowns. These high values indicate substantial deposition of up to 52?mg/m2/year. In 2011, over 51?% of open area precipitation was characterized by fluoride concentration higher than 0.10?mg/l, and in throughfall such concentrations were found in more tha...

  3. Characteristics and sources of tephra layers in the EPICA-Dome C ice record (East Antarctica): Implications for past atmospheric circulation and ice core stratigraphic correlations [rapid communication

    Science.gov (United States)

    Narcisi, B.; Petit, J. R.; Delmonte, B.; Basile-Doelsch, I.; Maggi, V.

    2005-11-01

    Thirteen discrete air-fall tephra layers were identified in the last 200,000-yr section of the EPICA-Dome C ice record drilled in the East Antarctic plateau (75°06'S, 123°21'E). Quantitative grain size, glass particle morphology, and the grain-discrete major element composition of the glass fraction of these layers were investigated. Through comparison with literature data on the rock composition of Quaternary volcanic centres located within and around Antarctica, five tephra layers were attributed to South Sandwich volcanoes in the South Atlantic Ocean, two to South Shetland volcanoes (northern Antarctic Peninsula), two to Andean volcanoes, and four to Antarctic (Marie Byrd Land and Melbourne) provinces. The abundance of layers originating in the southern part of the Atlantic confirms that westerly atmospheric circulation spiralling towards East Antarctica prevailed over the last 200 ka. Moreover, the record of events from Antarctic centres suggests that atmospheric trajectories from West to East Antarctica can also be significant. A few ash layers are geochemically distinct and appear equivalent to levels from Vostok and Dome Fuji deep ice records, located ca. 600 km and ca. 2000 km, respectively, from Dome C on the Antarctic plateau. These layers provide unambiguous markers for future correlation with other Antarctic ice cores and circumpolar marine climatic records. They also provide reliable constraints to get a common timescale by glaciological modelling, and represent a first step towards absolute ice core dating.

  4. Stable isotopic evidence of El Niño-like atmospheric circulation in the Pliocene western United States

    Directory of Open Access Journals (Sweden)

    M. J. Winnick

    2013-04-01

    Full Text Available Understanding how the hydrologic cycle has responded to warmer global temperatures in the past is especially important today as concentrations of CO2 in the atmosphere continue to increase due to human activities. The Pliocene offers an ideal window into a climate system that has equilibrated with current atmospheric pCO2. During the Pliocene the western United States was wetter than modern, an observation at odds with our current understanding of future warming scenarios, which involve the expansion and poleward migration of the subtropical dry zone. Here we compare Pliocene oxygen isotope profiles of pedogenic carbonates across the western US to modern isotopic anomalies in precipitation between phases of the El Niño–Southern Oscillation (ENSO. We find that when accounting for seasonality of carbonate formation, isotopic changes through the late Pliocene match modern precipitation isotopic anomalies in El Niño years. Furthermore, isotopic shifts through the late Pliocene mirror changes through the early Pleistocene, which likely represents the southward migration of the westerly storm track caused by growth of the Laurentide ice sheet. We propose that the westerly storm track migrated northward through the late Pliocene with the development of the modern cold tongue in the east equatorial Pacific, then returned southward with widespread glaciation in the Northern Hemisphere – a scenario supported by terrestrial climate proxies across the US. Together these data support the proposed existence of background El Niño-like conditions in western North America during the warm Pliocene. If the earth behaves similarly with future warming, this observation has important implications with regard to the amount and distribution of precipitation in western North America.

  5. 2012/13 abnormal cold winter in Japan associated with Large-scale Atmospheric Circulation and Local Sea Surface Temperature over the Sea of Japan

    Science.gov (United States)

    Ando, Y.; Ogi, M.; Tachibana, Y.

    2013-12-01

    On Japan, wintertime cold wave has social, economic, psychological and political impacts because of the lack of atomic power stations in the era of post Fukushima world. The colder winter is the more electricity is needed. Wintertime weather of Japan and its prediction has come under the world spotlight. The winter of 2012/13 in Japan was abnormally cold, and such a cold winter has persisted for 3 years. Wintertime climate of Japan is governed by some dominant modes of the large-scale atmospheric circulations. Yasunaka and Hanawa (2008) demonstrated that the two dominant modes - Arctic Oscillation (AO) and Western Pacific (WP) pattern - account for about 65% of the interannual variation of the wintertime mean surface air temperature of Japan. A negative AO brings about cold winter in Japan. In addition, a negative WP also brings about cold winter in Japan. Looking back to the winter of 2012/13, both the negative AO and negative WP continued from October through December. If the previous studies were correct, it would have been extremely very cold from October through December. In fact, in December, in accordance with previous studies, it was colder than normal. Contrary to the expectation, in October and November, it was, however, warmer than normal. This discrepancy signifies that an additional hidden circumstance that heats Japan overwhelms these large-scale atmospheric circulations that cool Japan. In this study, we therefore seek an additional cause of wintertime climate of Japan particularly focusing 2012 as well as the AO and WP. We found that anomalously warm oceanic temperature surrounding Japan overwhelmed influences of the AO or WP. Unlike the inland climate, the island climate can be strongly influenced by surrounding ocean temperature, suggesting that large-scale atmospheric patterns alone do not determine the climate of islands. (a) Time series of a 5-day running mean AO index (blue) as defined by Ogi et al., (2004), who called it the SVNAM index. For

  6. Evolution of the 1991-1992 Arctic vortex and comparison with the Geophysical Fluid Dynamics Laboratory SKYHI general circulation model

    Energy Technology Data Exchange (ETDEWEB)

    Strahan, S.E.; Rosenfield, J.E.; Loewenstein, M.; Podolske, J.R.; Weaver, A. [Applied Research Corp., Landover, MD (United States)]|[NASA, Goddard Space Flight Center, Greenbelt, MD (United States)]|[NASA, Ames Research Center, Moffett Field, CA (United States)

    1994-10-01

    Nitrous oxide (N2O) measured on board the ER-2 aircraft during the Airborne Arctic Stratospheric Expedition 2 (AASE 2) has been used to monitor descent of air inside the Arctic vortex between October 1991 and March 1992. Monthly mean N2O fields are calculated from the flight data and then compared with mean fields calculated from the high-resolution Geophysical Fluid Dynamics Laboratory general circulation model SKYHI in order to evaluate the model`s simulation of the polar vortex. From late fall through winter the model vortex evolves in much the same way as the 1991-1992 vortex, with N2O gradients at the edge becoming progressively steeper. The October to March trends in N2O profiles inside the vortex are used to verify daily net heating rates in the vortex that were computed from clear sky radiative heating rates and National Meteorological Center temperature observations. The computed heating rates successfully estimate the descent of vortex air from December through February but suggest that before December, air at high latitudes may not be isolated from the midlatitudes. SKYHI heating rates are in good agreement with the computed rates but tend to be slightly higher (i.e., less cooling) due to meteorological differences between SKYHI and the 1991-1992 winter. Three ER-2 flights measured N2O just north of the subtropical jet. These low-midlatitude profiles show only slight differences from the high-midlatitude profiles (45 deg - 60 deg N), indicating strong meridional mixing in the midlatitude `surf zone.` Mean midwinter N2O profiles inside and outside the vortex calculated from AASE 2 data are shown to be nearly identical to 1989 AASE profiles, pointing to the N2O/potential temperature relationship as an excellent marker for vortex air.

  7. Meridional Atmospheric and Oceanic Circulation and its influence on the Biogeochemical Cycling of Carbon West of the Antarctic Peninsula

    Science.gov (United States)

    Hughes, M. G.; Gabric, A. J.

    2010-12-01

    The region of the Southern Ocean directly adjacent to the Western Antarctic Peninsula is one of the fastest warming on the planet. The observed temperature increase has been coincident with a trend toward a positive Southern Annual Mode which introduces relatively warm northerly winds onto the peninsula. Furthermore, deep meridional waters (Upper Circumpolar Deep Water) can upwell onto the Antarctic continental shelf adjacent to the peninsula, introducing heat and nutrients to surface waters. The regional warming trend and the complex atmosphere - ocean interactions have altered the extent, duration and thickness of sea-ice in shelf waters. These environmental changes affect phytoplankton community distribution, bloom timing and species composition in what is typically a highly productive region. The efficiency of regional biogeochemical cycling of carbon may also be significantly altered. Understanding how environmental change affects biological production is key in understanding the regional biological carbon pump. This study brings together Chlorophyll-a climatology, derived from satellite data, to quantify changes in spring phytoplankton blooms. This time series is then used to investigate how fluctuations in upwelling of Upper Circumpolar Deep Water, fluctuations in large scale climate indices and sea-ice conditions modify marine productivity. Conclusions are also drawn as to how this may affect the regional carbon pump.

  8. Contribution of atmospheric circulation to recent off-shore sea-level variations in the Baltic Sea and the North Sea

    Directory of Open Access Journals (Sweden)

    S. Karabil

    2018-01-01

    Full Text Available The main purpose of this study is to quantify the contribution of atmospheric factors to recent off-shore sea-level variability in the Baltic Sea and the North Sea on interannual timescales. For this purpose, we statistically analysed sea-level records from tide gauges and satellite altimetry and several climatic data sets covering the last century. Previous studies had concluded that the North Atlantic Oscillation (NAO is the main pattern of atmospheric variability affecting sea level in the Baltic Sea and the North Sea in wintertime. However, we identify a different atmospheric circulation pattern that is more closely connected to sea-level variability than the NAO. This circulation pattern displays a link to sea level that remains stable through the 20th century, in contrast to the much more variable link between sea level and the NAO. We denote this atmospheric variability mode as the Baltic Sea and North Sea Oscillation (BANOS index. The sea-level pressure (SLP BANOS pattern displays an SLP dipole with centres of action located over (5° W, 45° N and (20° E, 70° N and this is distinct from the standard NAO SLP pattern in wintertime. In summertime, the discrepancy between the SLP BANOS and NAO patterns becomes clearer, with centres of action of the former located over (30° E, 45° N and (20° E, 60° N. This index has a stronger connection to off-shore sea-level variability in the study area than the NAO in wintertime for the period 1993–2013, explaining locally up to 90 % of the interannual sea-level variance in winter and up to 79 % in summer. The eastern part of the Gulf of Finland is the area where the BANOS index is most sensitive to sea level in wintertime, whereas the Gulf of Riga is the most sensitive region in summertime. In the North Sea region, the maximum sea-level sensitivity to the BANOS pattern is located in the German Bight for both winter and summer seasons. We investigated, and when possible

  9. The role of the thermohaline circulation in abrupt climate change.

    Science.gov (United States)

    Clark, Peter U; Pisias, Nicklas G; Stocker, Thomas F; Weaver, Andrew J

    2002-02-21

    The possibility of a reduced Atlantic thermohaline circulation in response to increases in greenhouse-gas concentrations has been demonstrated in a number of simulations with general circulation models of the coupled ocean-atmosphere system. But it remains difficult to assess the likelihood of future changes in the thermohaline circulation, mainly owing to poorly constrained model parameterizations and uncertainties in the response of the climate system to greenhouse warming. Analyses of past abrupt climate changes help to solve these problems. Data and models both suggest that abrupt climate change during the last glaciation originated through changes in the Atlantic thermohaline circulation in response to small changes in the hydrological cycle. Atmospheric and oceanic responses to these changes were then transmitted globally through a number of feedbacks. The palaeoclimate data and the model results also indicate that the stability of the thermohaline circulation depends on the mean climate state.

  10. Seasonal flows of international British Columbia-Alaska rivers: The nonlinear influence of ocean-atmosphere circulation patterns

    Science.gov (United States)

    Fleming, Sean W.; Hood, Eran; Dalhke, Helen; O'Neel, Shad

    2016-01-01

    The northern portion of the Pacific coastal temperate rainforest (PCTR) is one of the least anthropogenically modified regions on earth and remains in many respects a frontier area to science. Rivers crossing the northern PCTR, which is also an international boundary region between British Columbia, Canada and Alaska, USA, deliver large freshwater and biogeochemical fluxes to the Gulf of Alaska and establish linkages between coastal and continental ecosystems. We evaluate interannual flow variability in three transboundary PCTR watersheds in response to El Niño-Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), Arctic Oscillation (AO), and North Pacific Gyre Oscillation (NPGO). Historical hydroclimatic datasets from both Canada and the USA are analyzed using an up-to-date methodological suite accommodating both seasonally transient and highly nonlinear teleconnections. We find that streamflow teleconnections occur over particular seasonal windows reflecting the intersection of specific atmospheric and terrestrial hydrologic processes. The strongest signal is a snowmelt-driven flow timing shift resulting from ENSO- and PDO-associated temperature anomalies. Autumn rainfall runoff is also modulated by these climate modes, and a glacier-mediated teleconnection contributes to a late-summer ENSO-flow association. Teleconnections between AO and freshet flows reflect corresponding temperature and precipitation anomalies. A coherent NPGO signal is not clearly evident in streamflow. Linear and monotonically nonlinear teleconnections were widely identified, with less evidence for the parabolic effects that can play an important role elsewhere. The streamflow teleconnections did not vary greatly between hydrometric stations, presumably reflecting broad similarities in watershed characteristics. These results establish a regional foundation for both transboundary water management and studies of long-term hydroclimatic and environmental change.

  11. Interdecadal change on the relationship between the mid-summer temperature in South China and atmospheric circulation and sea surface temperature

    Science.gov (United States)

    Chen, Ruidan; Wen, Zhiping; Lu, Riyu

    2017-11-01

    South China suffers from high temperature frequently in mid-summer and this study aims to explore the interdecadal change of interannual variation of the mid-summer temperature in South China. It is revealed that the relationship between South China temperature and atmospheric circulation and sea surface temperature anomaly (SSTA) experiences an interdecadal change around the early 1990s. Before the early 1990s, warmer summer in South China is associated with the mid-latitude teleconnection featured by higher pressure over the Ural Mountains and the Korean Peninsula and lower pressure around the Lake Baikal. South China is located at the southern flank of an anomalous high pressure. After the early 1990s, South China temperature is prominently influenced by the tropical SSTA, and meanwhile the mid-latitude teleconnection becomes much weaker. Warmer summer is associated with higher pressure centered over South China and the El Niño to La Niña transition phase. The higher pressure influencing South China is located more southwards after the early 1990s, and it is favored by the tropical SSTA. The warmer SST in summer over the western tropical Pacific enhances the local convection and triggers an anomalous local Hadley cell with stronger subsidence over South China, directly leading to higher pressure over South China. Moreover, the colder SST over the central-eastern Pacific induces an anomalous Walker circulation and further strengthens the convection over the western tropical Pacific, exerting an indirect impact on the higher pressure over South China. The relative role of the western Pacific warming and central-eastern Pacific cooling is verified by CAM4 simulations. The intimate relationship between the tropical SSTA and South China temperature occurs during the El Niño to La Niña transition phase, which is the case after the early 1990s and suggests higher predictability for South China temperature in the recent decades.

  12. Atmospheric circulation patterns and geochemistry time series from ice/firn cores and snow samples of central Asian glaciers (Pamir, Tien Shan and Altai).

    Science.gov (United States)

    Aizen, E. M.; Aizen, V. B.; Joswiak, D. R.; Mayewski, P. A.

    2008-12-01

    Combination of high mountain ice-core isotope-geochemistry, ground based aerosol monitoring, NASA remote sensed and a NOAA atmospheric pressure distribution data were used to receive information on sources of dust/loess transport, their time and spatial extension in modern and pre-industrial time. Hundreds of samples from snow pits and ice/firn cores obtained from central Asian glaciers were collected, processed and analyzed. The NASA RS products address the gap in interpretation of available snow, firn and ice records by providing the spatial resolution necessary for identifying possible local and regional-scale dust sources, transport routes and depositions. NOAA Hypslit program modeled the air back-trajectories allowed to found association between the ice core geochemistry records and aerosol sources. To find the circulation patterns, which are closely associated with geochemistry ice core/snow pit records, the correlation coefficients between the Empirical Orthogonal Functions of the atmospheric circulation patterns and geochemistry time coefficients for first two unrotated scores were computed. The loess / dust storm sources with corresponding geo-chemical composition (trace elements, major ions and dust particles) in western, central and northern Asia were identified: 1. Tajik loess deposition and Iran, Afghanistan /Turkmenistan sands are for the Pamir. For example, the Pamir ice core records that associated with Tajikistan loess deposition are characterized by high concentrations of REEs and Al, high or median content of Ca, and a background S concentration. Samples from the Pamir Mountains differed in having low concentrations of Gadolinium. Occasional intrusions of Chinese loess to Pamir glaciers are not excluded. REE profile of pilot Pamir cores documented one of the most extreme droughts of 2001 and 2002 that developed in south-west Asia. 2. Chinese loess deposition in the Takla Makhan, sands in the Tajikistan Deserts and western Gobi, and dust aerosols

  13. The effects of future nationwide forest transition to discharge in the 21st century with regard to general circulation model climate change scenarios.

    Science.gov (United States)

    Mouri, Goro; Nakano, Katsuhiro; Tsuyama, Ikutaro; Tanaka, Nobuyuki

    2016-08-01

    Forest disturbance (or land-cover change) and climatic variability are commonly recognised as two major drivers interactively influencing hydrology in forested watersheds. Future climate changes and corresponding changes in forest type and distribution are expected to generate changes in rainfall runoff that pose a threat to river catchments. It is therefore important to understand how future climate changes will effect average rainfall distribution and temperature and what effect this will have upon forest types across Japan. Recent deforestation of the present-day coniferous forest and expected increases in evergreen forest are shown to influence runoff processes and, therefore, to influence future runoff conditions. We strongly recommend that variations in forest type be considered in future plans to ameliorate projected climate changes. This will help to improve water retention and storage capacities, enhance the flood protection function of forests, and improve human health. We qualitatively assessed future changes in runoff including the effects of variation in forest type across Japan. Four general circulation models (GCMs) were selected from the Coupled Model Intercomparison Project Phase 5 (CMIP5) ensemble to provide the driving fields: the Model for Interdisciplinary Research on Climate (MIROC), the Meteorological Research Institute Atmospheric General Circulation Model (MRI-GCM), the Hadley Centre Global Environment Model (HadGEM), and the Geophysical Fluid Dynamics Laboratory (GFDL) climate model. The simulations consisted of an ensemble including multiple physics configurations and different reference concentration pathways (RCP2.6, 4.5, and 8.5), the results of which have produced monthly data sets for the whole of Japan. The impacts of future climate changes on forest type in Japan are based on the balance amongst changes in rainfall distribution, temperature and hydrological factors. Methods for assessing the impact of such changes include the

  14. Influence of various forcings on global climate in historical times using a coupled atmosphere-ocean general circulation model

    DEFF Research Database (Denmark)

    Stendel, Martin; Mogensen, Irene A.; Christensen, Jens H.

    2006-01-01

    temperature record. The model is able to simulate individual extreme events such as the "year without a summer" 1816. Warm periods in the early seventeenth century and the second half of eighteenth century occur in periods of increased solar irradiation. Strong warming is simulated after 1850, in particular....... These cooling events are not restricted to Europe and North America, but cover most of the Northern Hemisphere. Colder than average conditions, for example during the late seventeenth and early eighteenth centuries, go along with a decrease in pressure difference between low and high latitudes and a decrease...... of the North Atlantic Oscillation. This favours positive sea ice anomalies east of Greenland and around Iceland, leading to widespread negative temperature anomalies over Europe. We also find characteristic blocking patterns over Western Europe, in particular during autumn, which contribute to the advection...

  15. Atmospheric circulation patterns, cloud-to-ground lightning, and locally intense convective rainfall associated with debris flow initiation in the Dolomite Alps of northeastern Italy

    Science.gov (United States)

    Underwood, S. Jeffrey; Schultz, Michael D.; Berti, Metteo; Gregoretti, Carlo; Simoni, Alessandro; Mote, Thomas L.; Saylor, Anthony M.

    2016-02-01

    The Dolomite Alps of northeastern Italy experience debris flows with great frequency during the summer months. An ample supply of unconsolidated material on steep slopes and a summer season climate regime characterized by recurrent thunderstorms combine to produce an abundance of these destructive hydro-geologic events. In the past, debris flow events have been studied primarily in the context of their geologic and geomorphic characteristics. The atmospheric contribution to these mass-wasting events has been limited to recording rainfall and developing intensity thresholds for debris mobilization. This study aims to expand the examination of atmospheric processes that preceded both locally intense convective rainfall (LICR) and debris flows in the Dolomite region. 500 hPa pressure level plots of geopotential heights were constructed for a period of 3 days prior to debris flow events to gain insight into the synoptic-scale processes which provide an environment conducive to LICR in the Dolomites. Cloud-to-ground (CG) lightning flash data recorded at the meso-scale were incorporated to assess the convective environment proximal to debris flow source regions. Twelve events were analyzed and from this analysis three common synoptic-scale circulation patterns were identified. Evaluation of CG flashes at smaller spatial and temporal scales illustrated that convective processes vary in their production of CF flashes (total number) and the spatial distribution of flashes can also be quite different between events over longer periods. During the 60 min interval immediately preceding debris flow a majority of cases exhibited spatial and temporal colocation of LICR and CG flashes. Also a number of CG flash parameters were found to be significantly correlated to rainfall intensity prior to debris flow initiation.

  16. Application of General Circulation Models to Assess the Potential Impact of Climate Change on Potential Distribution and Relative Abundance of Melanoplus sanguinipes (Fabricius (Orthoptera: Acrididae in North America

    Directory of Open Access Journals (Sweden)

    O. Olfert

    2011-01-01

    Full Text Available Climate is the dominant factor determining the distribution and abundance of most insect species. In recent years, the issue of climatic changes caused by human activities and the effects on agriculture has raised concern. General circulation model scenarios were applied to a bioclimatic model of Melanoplus sanguinipes to assess the potential impact of global warming on its distribution and relative abundance. Native to North America and widely distributed, M. sanguinipes is one of the grasshopper species of the continent most responsible for economic damage to grain, oilseed, pulse, and forage crops. Compared to predicted range and distribution under current climate conditions, model results indicated that M. sanguinipes would have increased range and relative abundance under the three general circulation model scenarios in more northern regions of North America. Conversely, model output predicted that the range of this crop pest could contract in regions where climate conditions became limiting.

  17. Changes in atmospheric circulation and the Arctic Oscillation preserved within a millennial length reconstruction of summer cloud cover from northern Fennoscandia

    Energy Technology Data Exchange (ETDEWEB)

    Young, Giles H.F.; McCarroll, Danny; Loader, Neil J.; Gagen, Mary H.; Demmler, Joanne C. [Swansea University, Department of Geography, Swansea (United Kingdom); Kirchhefer, Andreas J. [University of Tromsoe, Department of Arctic and Marine Biology, Tromsoe (Norway); Dendrooekologen, Tromsoe (Norway)

    2012-07-15

    Cloud cover currently represents the single greatest source of uncertainty in General Circulation Models. Stable carbon isotope ratios ({delta}{sup 13}C) from tree-rings, in areas of low moisture stress, are likely to be primarily controlled by photosynthetically active radiation (PAR), and therefore should provide a proxy record for cloud cover or sunshine; indeed this association has previously been demonstrated experimentally for Scots pine in Fennoscandia, with sunlight explaining ca 90% of the variance in photosynthesis and temperature only ca 4%. We present a statistically verifiable 1011-year reconstruction of cloud cover from a well replicated, annually-resolved {delta}{sup 13}C record from Forfjord in coastal northwestern Norway. This reconstruction exhibits considerable variability in cloud cover over the past millennium, including extended sunny periods during the cool seventeenth and eighteenth centuries and warm cloudy periods during the eleventh, early fifteenth and twentieth centuries. We find that while a generally positive relationship persists between sunshine and temperature at high-frequency, at lower (multi-decadal) frequencies the relationship is more often a negative one, with cool periods being sunny (most notably the Little Ice Age period from 1600 to 1750 CE) and warm periods more cloudy (e.g. the mediaeval and the twentieth century). We conclude that these long-term changes may be caused by changes in the dominant circulation mode, likely to be associated with the Arctic Oscillation. There is also strong circumstantial evidence that prolonged periods of high summer cloud cover, with low PAR and probably high precipitation, may be in part responsible for major European famines caused by crop failures. (orig.)

  18. The Role of the Ozone Hole and Elevated Greenhouse Gases as Drivers of Antarctic Sea Ice Extent Increase Via Changes in Atmospheric Circulation

    Science.gov (United States)

    Pope, J. O.; Orr, A.; Marshall, G.; Abraham, N. L.

    2015-12-01

    Antarctic sea ice extent has displayed an overall increase across the duration of the 35-year satellite record. However, the cause of this increase is uncertain, with both anthropogenic and natural forcing changes proposed as drivers. Here, we investigate two possible anthropogenic forcings that could influence sea ice extent via changes in the near-surface wind field over the Southern Ocean; (i) ozone depletion and (ii) greenhouse gas increases. We employ an atmosphere-only version of the UK Met Office model, HadGEM3, with prescribed sea surface temperatures and sea ice coupled to the UKCA interactive climate-chemistry model. Starting from a pre-industrial control simulation, two additional simulations were spun off, one investigating the forcing from increased 21st century greenhouse gases and one investigating the forcing from the ozone hole. Based on the work of Holland & Kwok (2012) we analyse the changes in Antarctic circulation, in particular the surface wind properties which have been shown to correlate with sea ice extent. We examine changes in the surface wind field in these two model simulations relative to that in the pre-industrial control simulation, compare them to observed changes during the satellite record, and assess their potential role in driving a response in sea ice extent at both continental and regional scales.

  19. Effect of Vegetation on the Late Miocene Ocean Circulation

    Directory of Open Access Journals (Sweden)

    Gerrit Lohmann

    2015-11-01

    Full Text Available We examine the role of the vegetation cover and the associated hydrological cycle on the deep ocean circulation during the Late Miocene (~10 million years ago. In our simulations, an open Central American gateway and exchange with fresh Pacific waters leads to a weak and shallow thermohaline circulation in the North Atlantic Ocean which is consistent with most other modeling studies for this time period. Here, we estimate the effect of a changed vegetation cover on the ocean general circulation using atmospheric circulation model simulations for the late Miocene climate with 353 ppmv CO2 level. The Late Miocene land surface cover reduces the albedo, the net evaporation in the North Atlantic catchment is affected and the North Atlantic water becomes more saline leading to a more vigorous North Atlantic Deep Water circulation. These effects reveal potentially important feedbacks between the ocean circulation, the hydrological cycle and the land surface cover for Cenozoic climate evolution.

  20. Sensitivity analysis of radiative heating and cooling rates in planetary atmospheres: general linearization and adjoint approaches

    Science.gov (United States)

    Ustinov, E. A.

    2002-01-01

    Radiative heating and cooling provide primary source and ultimate sink of energy driving lower planetary atmospheres. Evaluating the sensitivities of atmospheric dynamics models on these primary atmospheric parameters requires knowing how heating and cooling rates depend on these same parameters. We discuss two approaches that make it possible to directly compute the sensitivities of heating and cooling rates in parallel with evaluation of heating and cooling rates themselves.

  1. Snow cover setting-up dates in the north of Eurasia: relations and feedback to the macro-scale atmospheric circulation

    Directory of Open Access Journals (Sweden)

    V. V. Popova

    2014-01-01

    Full Text Available Variations of snow cover onset data in 1950–2008 based on daily snow depth data collected at first-order meteorological stations of the former USSR compiled at the Russia Institute of Hydrometeorological Information are analyzed in order to reveal climatic norms, relations with macro-scale atmospheric circulation and influence of snow cover anomalies on strengthening/weakening of westerly basing on observational data and results of simulation using model Planet Simulator, as well. Patterns of mean snow cover setting-up data and their correlation with temperature of the Northern Hemisphere extra-tropical land presented in Fig. 1 show that the most sensible changes observed in last decade are caused by temperature trend since 1990th. For the most portion of the studied territory variations of snow cover setting-up data may be explained by the circulation indices in the terms of Northern Hemisphere Teleconnection Patterns: Scand, EA–WR, WP and NAO (Fig. 2. Role of the Scand and EA–WR (see Fig. 2, а, в, г is recognized as the most significant.Changes of snow cover extent calculated on the base of snow cover onset data over the Russia territory, and its western and eastern parts as well, for the second decade of October (Fig. 3 demonstrate significant difference in variability between eastern and western regions. Eastern part of territory essentially differs by lower both year-to-year and long-term variations in the contrast to the western part, characterized by high variance including long-term tendencies: increase in 1950–70th and decrease in 1970–80 and during last six years. Nevertheless relations between snow cover anomalies and Arctic Oscillation (AO index appear to be significant exceptionally for the eastern part of the territory. In the same time negative linear correlation revealed between snow extent and AO index changes during 1950–2008 from statistically insignificant values (in 1950–70 and 1996–2008 to coefficient

  2. Using Mauna Loa Atmospheric CO2 Data in Large General Education Geoscience Courses

    Science.gov (United States)

    Richardson, R. M.; Kapp, J. L.

    2007-12-01

    We have been using the Mauna Loa atmospheric CO2 dataset (http://scrippsco2.ucsd.edu/data/in_situ_co2/monthly_mlo.csv) in a large (up to 300) General Education Geoscience course, primarily in small breakout groups (30 students). The exercise is designed to address quantitative literacy including percentages, slopes and linear trends, issues of data completeness and bias, quality of extrapolations, as well as implications for climate change. We are significantly revising the course, which serves 600 students a semester, with help from a curriculum grant. A major goal is to improve student learning by incorporating inquiry based activities in the large lecture setting. Lectures now incorporate several activities throughout a given class period, in which students are asked to use critical thinking skills such as interpreting patterns in data and graphs, analyzing a scientific hypothesis for its coherence with the scientific method, and answering higher order synthesis questions in both verbal and written form. This differs from our past format where class periods were dominated by lecture, with a single short activity done individually about every other lecture. To test the effectiveness of the new course format we will give students the same atmospheric CO2 exercise in the lecture setting that they were given previously in breakout groups. Students will work in small groups in lecture after receiving a short introduction to the exercise by the instructor. They will plot CO2 concentrations, make extrapolations, and interpret patterns in the data. We will compare scores on the exercise with previous semesters. We expect that students will do better having had more experience with interpreting scientific data and practicing higher order thinking skills. We also expect working in small groups will foster better learning through peer teaching and discussion. We will incorporate responses from students who took part in the exercises from current and previous semesters. We

  3. Multi-time-scale hydroclimate dynamics of a regional watershed and links to large-scale atmospheric circulation: Application to the Seine river catchment, France

    Science.gov (United States)

    Massei, N.; Dieppois, B.; Hannah, D. M.; Lavers, D. A.; Fossa, M.; Laignel, B.; Debret, M.

    2017-03-01

    In the present context of global changes, considerable efforts have been deployed by the hydrological scientific community to improve our understanding of the impacts of climate fluctuations on water resources. Both observational and modeling studies have been extensively employed to characterize hydrological changes and trends, assess the impact of climate variability or provide future scenarios of water resources. In the aim of a better understanding of hydrological changes, it is of crucial importance to determine how and to what extent trends and long-term oscillations detectable in hydrological variables are linked to global climate oscillations. In this work, we develop an approach associating correlation between large and local scales, empirical statistical downscaling and wavelet multiresolution decomposition of monthly precipitation and streamflow over the Seine river watershed, and the North Atlantic sea level pressure (SLP) in order to gain additional insights on the atmospheric patterns associated with the regional hydrology. We hypothesized that: (i) atmospheric patterns may change according to the different temporal wavelengths defining the variability of the signals; and (ii) definition of those hydrological/circulation relationships for each temporal wavelength may improve the determination of large-scale predictors of local variations. The results showed that the links between large and local scales were not necessarily constant according to time-scale (i.e. for the different frequencies characterizing the signals), resulting in changing spatial patterns across scales. This was then taken into account by developing an empirical statistical downscaling (ESD) modeling approach, which integrated discrete wavelet multiresolution analysis for reconstructing monthly regional hydrometeorological processes (predictand: precipitation and streamflow on the Seine river catchment) based on a large-scale predictor (SLP over the Euro-Atlantic sector). This

  4. Examination of aerosol distributions and radiative effects over the Bay of Bengal and the Arabian Sea region during ICARB using satellite data and a general circulation model

    Directory of Open Access Journals (Sweden)

    R. Cherian

    2012-02-01

    Full Text Available In this paper we analyse aerosol loading and its direct radiative effects over the Bay of Bengal (BoB and Arabian Sea (AS regions for the Integrated Campaign on Aerosols, gases and Radiation Budget (ICARB undertaken during 2006, using satellite data from the MODerate Resolution Imaging Spectroradiometer (MODIS on board the Terra and Aqua satellites, the Aerosol Index from the Ozone Monitoring Instrument (OMI on board the Aura satellite, and the European-Community Hamburg (ECHAM5.5 general circulation model extended by Hamburg Aerosol Module (HAM. By statistically comparing with large-scale satellite data sets, we firstly show that the aerosol properties measured during the ship-based ICARB campaign and simulated by the model are representative for the BoB and AS regions and the pre-monsoon season. In a second step, the modelled aerosol distributions were evaluated by a comparison with the measurements from the ship-based sunphotometer, and the satellite retrievals during ICARB. It is found that the model broadly reproduces the observed spatial and temporal variability in aerosol optical depth (AOD over BoB and AS regions. However, AOD was systematically underestimated during high-pollution episodes, especially in the BoB leg. We show that this underprediction of AOD is mostly because of the deficiencies in the coarse mode, where the model shows that dust is the dominant component. The analysis of dust AOD along with the OMI Aerosol Index indicate that missing dust transport that results from too low dust emission fluxes over the Thar Desert region in the model caused this deficiency. Thirdly, we analysed the spatio-temporal variability of AOD comparing the ship-based observations to the large-scale satellite observations and simulations. It was found that most of the variability along the track was from geographical patterns, with a minor influence by single events. Aerosol fields were homogeneous enough to yield a good statistical agreement

  5. Seasonal overturning circulation in the Red Sea: 2. Winter circulation

    KAUST Repository

    Yao, Fengchao

    2014-04-01

    The shallow winter overturning circulation in the Red Sea is studied using a 50 year high-resolution MITgcm (MIT general circulation model) simulation with realistic atmospheric forcing. The overturning circulation for a typical year, represented by 1980, and the climatological mean are analyzed using model output to delineate the three-dimensional structure and to investigate the underlying dynamical mechanisms. The horizontal model circulation in the winter of 1980 is dominated by energetic eddies. The climatological model mean results suggest that the surface inflow intensifies in a western boundary current in the southern Red Sea that switches to an eastern boundary current north of 24N. The overturning is accomplished through a cyclonic recirculation and a cross-basin overturning circulation in the northern Red Sea, with major sinking occurring along a narrow band of width about 20 km along the eastern boundary and weaker upwelling along the western boundary. The northward pressure gradient force, strong vertical mixing, and horizontal mixing near the boundary are the essential dynamical components in the model\\'s winter overturning circulation. The simulated water exchange is not hydraulically controlled in the Strait of Bab el Mandeb; instead, the exchange is limited by bottom and lateral boundary friction and, to a lesser extent, by interfacial friction due to the vertical viscosity at the interface between the inflow and the outflow. Key Points Sinking occurs in a narrow boundary layer along the eastern boundary Surface western boundary current switches into an eastern boundary current Water exchange in the Strait of Bab el Mandeb is not hydraulically controlled © 2014. American Geophysical Union. All Rights Reserved.

  6. Circulation of Venusian atmosphere at 95-100 km apparent motions of 1.27 μm nightglow of O2 observed by VIRTIS on board Venus Express

    Science.gov (United States)

    Gorinov, D.; Khatuntsev, I.; Zasova, L.; Tyurin, A.

    2017-09-01

    This work is aimed at understanding the complex atmosphere motion on Venus in the altitude range of 95-100 km. It is located above the area of dominance of the retrograde zonal superrotation (RZS) and below the area of dominance of the subsolar-antisolar circulation (SS-AS), thus being important for the global circulation models. The work analyzes the entire dataset of the VIRTIS instrument (Venus Express spacecraft). Wind velocities are calculated after tracking the displacements of the markers in the cloud-like oxygen airglow. The resulting distribution of the motion indicates a stronger influence of the SS-AS and an almost negligible of the RZS, with an influence of other presumed mechanisms of circulation. Both zonal and meridional components of the motion manifest dependence on latitude and local time. Several examples of the orbit-to-orbit variation show evolution and a high variability of the winds in localized areas.

  7. Parietaria judaica flowering phenology, pollen production, viability and atmospheric circulation, and expansive ability in the urban environment: impacts of environmental factors

    Science.gov (United States)

    Fotiou, Christina; Damialis, Athanasios; Krigas, Nikolaos; Halley, John M.; Vokou, Despoina

    2011-01-01

    Parietaria judaica (Urticaceae) grows abundantly in urban areas of the Mediterranean region. Its pollen is a major allergy source. We studied the species' distribution and abundance in and around Thessaloniki (Greece), pollen production and pollen season. We also examined how urban pollution affects pollen viability. Our ultimate goal was to obtain an estimate of the species' performance and ability to expand under different environmental conditions related to climate change. We mapped P. judaica and the other Urticaceae species. In a north- and a south-facing population, we recorded the progress of P. judaica flowering and estimated the pollen content per flower, shoot and surface unit. We concurrently assessed atmospheric circulation of Urticaceae pollen. We estimated P. judaica pollen viability and Cu, Pb and Zn concentrations in plants collected from sites differing in traffic intensity. P. judaica is the most abundant Urticaceae species in the area; its occurrence has increased dramatically over the last 100 years. Production of flowers is intense in spring and autumn. Flowering started 12 days earlier in the south-facing population in spring, and 3 days later in autumn. Pollen production was higher in spring and in the south-facing population. Flower and pollen production were positively correlated with the size of the plant and the flower, respectively. Copper and lead concentrations in plants were positively correlated with pollen viability, which was higher for plants collected from high-traffic sites. P. judaica has a high phenotypic plasticity; this is a feature that promotes success of expansive and invasive species. It is also well adapted to warm and polluted urban environments. The climatic change forecast for the Mediterranean region could provoke earlier, longer, and more pronounced flowering and, consequently, more P. judaica pollen in the air. In return, this would result in increased severity of Parietaria pollinosis.

  8. Variations in extreme precipitation on the Loess Plateau using a high-resolution dataset and their linkages with atmospheric circulation indices

    Science.gov (United States)

    Zhao, Guangju; Zhai, Jianqing; Tian, Peng; Zhang, Limei; Mu, Xingmin; An, Zhengfeng; Han, Mengwei

    2017-08-01

    Assessing regional patterns and trends in extreme precipitation is crucial for facilitating flood control and drought adaptation because extreme climate events have more damaging impacts on society and ecosystems than simple shifts in the mean values. In this study, we employed daily precipitation data from 231 climate stations spanning 1961 to 2014 to explore the changes in precipitation extremes on the Loess Plateau, China. Nine of the 12 extreme precipitation indices suggested decreasing trends, and only the annual total wet-day precipitation (PRCPTOT) and R10 declined significantly: - 0.69 mm/a and - 0.023 days/a at the 95% confidence level. The spatial patterns in all of the extreme precipitation indices indicated mixed trends on the Loess Plateau, with decreasing trends in the precipitation extremes at the majority of the stations examined in the Fen-Wei River valley and high-plain plateau. Most of extreme precipitation indices suggested apparent regional differences, whereas R25 and R20 had spatially similar patterns on the Loess Plateau, with many stations revealing no trends. In addition, we found a potential decreasing trend in rainfall amounts and rainy days and increasing trends in rainfall intensities and storm frequencies in some regions due to increasing precipitation events in recent years. The relationships between extreme rainfall events and atmospheric circulation indices suggest that the weakening trend in the East Asia summer monsoon has limited the northward extension of the rainfall belt to northern China, thereby leading to a decrease in rainfall on the Loess Plateau.

  9. Variability of onset and retreat of the rainy season in mainland China and associations with atmospheric circulation and sea surface temperature

    Science.gov (United States)

    Cao, Qing; Hao, Zhenchun; Shao, Quanxi; Hao, Jie; Nyima, Tsring

    2018-02-01

    Precipitation plays an important role in both environment and human society and is a significant factor in many scientific researches such as water resources, agriculture and climate impact studies. The onset and retreat of rainy season are useful features to understand the variability of precipitation under the influence of climate change. In this study, the characteristics of onset and retreat in mainland China are investigated. The multi-scale moving t-test was applied to determine rainy season and K-means cluster analysis was used to divide China into sub-regions to better investigate rainy season features. The possible linkage of changing characteristics of onset and retreat to climate factors were also explored. Results show that: (1) the onset started from middle March in the southeast of China to early June in the northwest and rainy season ended earliest in the northwest and southeast while the central China had the latest retreat; (2) Delayed onset and advanced retreat over time were observed in many parts of China, together with overall stable or increased rainy-season precipitation, would likely lead to higher probability of flooding; (3) The onset (retreat) was associated with the increased (decreased) number of cyclones in eastern China and anticyclone near the South China Sea. Delayed onset, and advanced retreat were likely related to cold and warm sea surface temperature (SST) in the conventional El Niño-Southern Oscillation (ENSO) regions, respectively. These results suggest that predictability of rainy season can be improved through the atmospheric circulation and SST, and help water resources management and agricultural planning.

  10. Antarctic boundary layer parametrization in a general circulation model : 1-D simulations facing summer observations at Dome C

    NARCIS (Netherlands)

    Vignon, Etienne; Hourdin, Frédéric; Genthon, Christophe; Gallée, Hubert; Bazile, Eric; Lefebvre, Marie Pierre; Madeleine, Jean Baptiste; van de Wiel, B.J.H.

    2017-01-01

    The parametrization of the atmospheric boundary layer (ABL) is critical over the Antarctic Plateau for climate modelling since it affects the climatological temperature inversion and the negatively buoyant near-surface flow over the ice-sheet. This study challenges state-of-the-art

  11. Scientific investigations of atmospheric processes

    Science.gov (United States)

    1994-01-01

    Research was performed in atmospheric, dynamical, and thermodynamical processes and in other disciplines necessary to accomplish the following tasks: develop procedures for combining generalized radiative transfer codes with dynamic atmospheric model codes; perform diagnostic analysis of atmospheric processes to gain a better understanding of the evolution and development of mesoscale circulation systems and their precipitation structures; and to develop algorithms and software necessary to graphically display diagnostic sets on the MSFC McIDAS and EADS to facilitate scientific study and sensor capability evaluation. Research activities during this reporting period are detailed.

  12. Why do general circulation models overestimate the aerosol cloud lifetime effect? A case study comparing CAM5 and a CRM

    OpenAIRE

    Zhou, C.; J. E. Penner

    2017-01-01

    Observation-based studies have shown that the aerosol cloud lifetime effect or the increase of cloud liquid water path (LWP) with increased aerosol loading may have been overestimated in climate models. Here, we simulate shallow warm clouds on 27 May 2011 at the southern Great Plains (SGP) measurement site established by the Department of Energy's (DOE) Atmospheric Radiation Measurement (ARM) program using a single-column version of a global climate model (Community Atmosphe...

  13. Numerical Analysis of General Trends in Single-Phase Natural Circulation in a 2D-Annular Loop

    Directory of Open Access Journals (Sweden)

    Gilles Desrayaud

    2008-01-01

    Full Text Available The aim of this paper is to address fluid flow behavior of natural circulation in a 2D-annular loop filled with water. A two-dimensional, numerical analysis of natural convection in a 2D-annular closed-loop thermosyphon has been performed for various radius ratios from 1.2 to 2.0, the loop being heated at a constant flux over the bottom half and cooled at a constant temperature over the top half. It has been numerically shown that natural convection in a 2D-annular closed-loop thermosyphon is capable of showing pseudoconductive regime at pitchfork bifurcation, stationary convective regimes without and with recirculating regions occurring at the entrance of the exchangers, oscillatory convection at Hopf bifurcation and Lorenz-like chaotic flow. The complexity of the dynamic properties experimentally encountered in toroidal or rectangular loops is thus also found here.

  14. Do regions outside the tropical Pacific influence ENSO through atmospheric teleconnections?

    Digital Repository Service at National Institute of Oceanography (India)

    Dayan, H.; Izumo, T.; Vialard, J.; Lengaigne, M.; Masson, S

    This paper aims at identifying oceanic regions outside the tropical Pacific, which may influence the El Ni�o Southern Oscillation (ENSO) through interannual modulation of equatorial Pacific winds An Atmospheric General Circulation Model (AGCM) 7...

  15. Atmospheric circulation changes and neoglacial conditions in the Southern Hemisphere mid-latitudes: insights from PMIP2 simulations at 6 kyr

    Energy Technology Data Exchange (ETDEWEB)

    Rojas, Maisa [University of Chile, Department of Geophysics, Santiago (Chile); Moreno, Patricio I. [University of Chile, Department of Ecology, Santiago (Chile)

    2011-07-15

    Glacial geologic studies in the Southern Hemisphere (SH) mid-latitudes (40-54 S) indicate renewed glacial activity in southern South America (Patagonia) and New Zealand's (NZ) South Island starting at {proportional_to}7 kyr, the so-called neoglaciation. Available data indicate that neoglacial advances in these regions occurred during a rising trend in atmospheric CO{sub 2} and CH{sub 4} concentrations, lower-than-present but increasing summer insolation and seasonality contrasts. In this paper we examine the climatological context in which neoglaciations occurred through analysis of the complete Paleoclimate Modelling Inter-comparison Project (PMIP2) database of simulations at 6 kyr for the SH. We observe that the amplitude of the annual insolation cycle in the SH did not change significantly at 6 kyr compared to the pre-industrial values, the largest difference occurring in autumn (MAM, negative anomalies) and spring (SON, positive anomalies). The simulated changes in temperatures over the SH respond to the insolation changes, with a 1-2 month delay over the oceans. This results in a reduced amplitude of the annual cycle of temperature and precipitation over most continental regions, except over Patagonia and NZ, that show a slight increase. In contrast, large-scale circulation features, such as the low and upper level winds and the subtropical anticyclones show an amplified annual cycle, as a direct response to the increased/decreased insolation during the transitional seasons SON/MAM. In the annual mean, there is a small but consistent equatorward shift of the latitude of maximum wind speed of 1-3 over the entire SH, which results in a small increase of wind speed over the South Pacific and Atlantic Oceans north of {proportional_to}50 S and a widespread decline south of 50 S. PMIP2 simulations for 6 kyr, indicate that in the annual mean, the SH mid-latitudes were colder, wetter and with stronger winds north of about 50 S. These conditions are consistent

  16. New directions in hydro-climatic histories: observational data recovery, proxy records and the atmospheric circulation reconstructions over the earth (ACRE) initiative in Southeast Asia

    Science.gov (United States)

    Williamson, Fiona; Allan, Rob; Switzer, Adam D.; Chan, Johnny C. L.; Wasson, Robert James; D'Arrigo, Rosanne; Gartner, Richard

    2015-12-01

    The value of historic observational weather data for reconstructing long-term climate patterns and the detailed analysis of extreme weather events has long been recognized (Le Roy Ladurie, 1972; Lamb, 1977). In some regions however, observational data has not been kept regularly over time, or its preservation and archiving has not been considered a priority by governmental agencies. This has been a particular problem in Southeast Asia where there has been no systematic country-by-country method of keeping or preserving such data, the keeping of data only reaches back a few decades, or where instability has threatened the survival of historic records. As a result, past observational data are fragmentary, scattered, or even absent altogether. The further we go back in time, the more obvious the gaps. Observational data can be complimented however by historical documentary or proxy records of extreme events such as floods, droughts and other climatic anomalies. This review article highlights recent initiatives in sourcing, recovering, and preserving historical weather data and the potential for integrating the same with proxy (and other) records. In so doing, it focuses on regional initiatives for data research and recovery - particularly the work of the international Atmospheric Circulation Reconstructions over the Earth's (ACRE) Southeast Asian regional arm (ACRE SEA) - and the latter's role in bringing together disparate, but interrelated, projects working within this region. The overarching goal of the ACRE SEA initiative is to connect regional efforts and to build capacity within Southeast Asian institutions, agencies and National Meteorological and Hydrological Services (NMHS) to improve and extend historical instrumental, documentary and proxy databases of Southeast Asian hydroclimate, in order to contribute to the generation of high-quality, high-resolution historical hydroclimatic reconstructions (reanalyses) and, to build linkages with humanities researchers

  17. Interannual variability of a precipitation gradient along the semi-arid catchment areas for the metropolitan region of Lima- Peru in relation to atmospheric circulation at the mesoscale

    Science.gov (United States)

    Otto, Marco; Seidel, Jochen; Trachte, Katja

    2013-04-01

    following questions. How is the interannual variability of the observed precipitation gradient related to atmospheric circulation east (Amazon basin) and west (south-east Pacific) of the study region? If those relations are quantifiable, are there any forecast potentials for the characteristics of the precipitation gradient during the raining season? The results of the study provide valuable information needed to understand the generation of rainfall in the frame of a case study for the largest metropolitan area that is located at the arid Pacific coast of Peru. This information may also be useful for local managers in order to optimise water resource management and land use strategies.

  18. Why do general circulation models overestimate the aerosol cloud lifetime effect? A case study comparing CAM5 and a CRM

    Science.gov (United States)

    Zhou, Cheng; Penner, Joyce E.

    2017-01-01

    Observation-based studies have shown that the aerosol cloud lifetime effect or the increase of cloud liquid water path (LWP) with increased aerosol loading may have been overestimated in climate models. Here, we simulate shallow warm clouds on 27 May 2011 at the southern Great Plains (SGP) measurement site established by the Department of Energy's (DOE) Atmospheric Radiation Measurement (ARM) program using a single-column version of a global climate model (Community Atmosphere Model or CAM) and a cloud resolving model (CRM). The LWP simulated by CAM increases substantially with aerosol loading while that in the CRM does not. The increase of LWP in CAM is caused by a large decrease of the autoconversion rate when cloud droplet number increases. In the CRM, the autoconversion rate is also reduced, but this is offset or even outweighed by the increased evaporation of cloud droplets near the cloud top, resulting in an overall decrease in LWP. Our results suggest that climate models need to include the dependence of cloud top growth and the evaporation/condensation process on cloud droplet number concentrations.

  19. Development of the Grid-Independent GEOS-Chem Module and its deployment in the GEOS-5 General Circulation Model

    Science.gov (United States)

    Long, M. S.; Yantosca, R. M.; Nielsen, J. E.; da Silva, A.; Pawson, S.; Keller, C. A.; Sulprizio, M.; Jacob, D. J.

    2013-12-01

    The Harvard University GEOS-Chem 3-D chemical transport model simulates atmospheric composition - including tropospheric oxidants, primary and secondary aerosols, carbon gases, mercury, and others - driven by NASA's Goddard Earth Observing System (GEOS) assimilated meteorological data. A collaborative project between Harvard University and NASA's Global Modeling and Assimilation Office (GMAO) is focused on redesigning GEOS-Chem's core program structure to meet requirements of the Earth System Modeling Framework (ESMF). This new module, the Grid-Independent GEOS-Chem (GIGC), is capable of operating on an arbitrary horizontal geophysical grid, and has been embedded as the tropospheric chemistry component in GEOS-5, which is an HPC-capable Earth System Model. The primary goals of the GIGC are (1) the use of the GEOS-Chem inside the GEOS-5 Data Assimilation System, for multi-constituent chemical data assimilation of satellite observations (including tropospheric ozone, CO, and NO2); and (2) studies of fully-coupled atmospheric chemistry-climate feedbacks. Both of these goals are enhanced by the ease-of-implementation of new science within GEOS-Chem, which permits model development by GEOS-Chem's wide user community to be quickly integrated within both the stand-alone and the GCM-embedded model versions. Here, we present the first results of the GIGC-coupled GEOS-5 GCM, run at multiple grid resolutions and both rectilinear and cubed-sphere grids. Case studies are used to illustrate model performance at a variety of spatial resolutions.

  20. European Geophysical Society (23rd) General Assembly, Annales Geophysicae. Part 2. Hydrology, Oceans & Atmosphere, Supplement 2 to Volume 16 Held in Nice, France on 20-24 April 1998

    Science.gov (United States)

    1998-01-01

    management in the Mediterranean for efficient water use C 535 II.2 OCEANS & ATMOSPHERE (OA) OA1 The thermohaline circulation C 536 OA2...rivers of (he basin. Is de- lected as of concentration of nutrient matters (N02", NO,", rvV -) cyclical ostll- lalloru. It I* discovered that phases of...have implications for the sustainability of agricultural cultivation on shallow soils OCEANS & ATMOSPHERE (OA) OA1 The thermohaline circulation

  1. A new method for evaluating the impact of vertical distribution on aerosol radiative forcing in general circulation models

    Science.gov (United States)

    Vuolo, M. R.; Schulz, M.; Balkanski, Y.; Takemura, T.

    2013-07-01

    The quantification and understanding of direct aerosol forcing is essential in the study of climate. One of the main issues that makes its quantification difficult is the lack of a complete comprehension of the role of the aerosol and clouds vertical distribution. This work aims at reducing the incertitude of aerosol forcing due to the vertical superposition of several short-lived atmospheric components, in particular different aerosols species and clouds. We propose a method to quantify the contribution of different parts of the atmospheric column to the forcing, and to evaluate model differences by isolating the effect of radiative interactions only. Any microphysical or thermo-dynamical interactions between aerosols and clouds are deactivated in the model, to isolate the effects of radiative flux coupling. We investigate the contribution of aerosol above, below and in clouds, by using added diagnostics in the aerosol-climate model LMDz. We also compute the difference between the forcing of the ensemble of the aerosols and the sum of the forcings from individual species, in clear-sky. This difference is found to be moderate on global average (14%) but can reach high values regionally (up to 100%). The non-additivity of forcing already for clear-sky conditions shows, that in addition to represent well the amount of individual aerosol species, it is critical to capture the vertical distribution of all aerosols. Nonlinear effects are even more important when superposing aerosols and clouds. Four forcing computations are performed, one where the full aerosol 3-D distribution is used, and then three where aerosols are confined to regions above, inside and below clouds respectively. We find that the forcing of aerosols depends crucially on the presence of clouds and on their position relative to that of the aerosol, in particular for black carbon (BC). We observe a strong enhancement of the forcing of BC above clouds, attenuation for BC below clouds, and a moderate

  2. The linkage between stratospheric water vapor and surface temperature in an observation-constrained coupled general circulation model

    Science.gov (United States)

    Wang, Yuan; Su, Hui; Jiang, Jonathan H.; Livesey, Nathaniel J.; Santee, Michelle L.; Froidevaux, Lucien; Read, William G.; Anderson, John

    2017-04-01

    We assess the interactions between stratospheric water vapor (SWV) and surface temperature during the past two decades using satellite observations and the Community Earth System Model (CESM). From 1992 to 2013, to first order, the observed SWV exhibited three distinct piece-wise trends: a steady increase from 1992 to 2000, an abrupt drop from 2000 to 2004, and a gradual recovery after 2004, while the global-mean surface temperature experienced a strong increase until 2000 and a warming hiatus after 2000. The atmosphere-only CESM shows that the seasonal variation of tropical-mean (30°S-30°N) SWV is anticorrelated with that of the tropical-mean sea surface temperature (SST), while the correlation between the tropical SWV and SST anomalies on the interannual time scale is rather weak. By nudging the modeled SWV to prescribed profiles in coupled atmosphere-slab ocean experiments, we investigate the impact of SWV variations on surface temperature change. We find that a uniform 1 ppmv (0.5 ppmv) SWV increase (decrease) leads to an equilibrium global mean surface warming (cooling) of 0.12 ± 0.05 °C (-0.07 ± 0.05 °C). Sensitivity experiments show that the equilibrium response of global mean surface temperature to SWV perturbations over the extratropics is larger than that over the tropics. The observed sudden drop of SWV from 2000 to 2004 produces a global mean surface cooling of about -0.048 ± 0.041 °C, which suggests that a persistent change in SWV would make an imprint on long-term variations of global-mean surface temperature. A constant linear increase in SWV based on the satellite-observed rate of SWV change yields a global mean surface warming of 0.03 ± 0.01 °C/decade over a 50-year period, which accounts for about 19 % of the observed surface temperature increase prior to the warming hiatus. In the same experiment, trend analyses during different periods reveal a multi-year adjustment of surface temperature before the response to SWV forcing becomes

  3. CONCENTRATION OF CIRCULATING IMMUNE COMPLEXES IN EXPERIMENTAL GENERALIZED INFLAMMATORY PROCESS IN ANIMALS OF DIFFERENT AGE UNDER ACTION OF IMMUNOMODULATORS

    Directory of Open Access Journals (Sweden)

    Kovalenko T.I.

    2015-05-01

    Full Text Available Under physiological conditions a formation and a presence of the CEC in liquids is one of the manifestations of the immune response to receipt of antigens and an important factor, which provides immunity. Circulating immune complexes act as agents involved in the regulation of immune response and maintaining communication between the immune system and other regulatory systems of the body and direction to his defense. The intensity of the formation of the CEC may vary under the influence of infectious antigens and immune preparations. Material and methods. Material for the experiment were white male rats 3 months of age ("young" weighing 100 -140gr. (n = 40 and 22-month ("old" weighing 200 -240 g. (n = 40. And the first (n=10 and second (n=10 groups of rats served as controls. Third (n=15 and fourth (n=15 group of animals was injected intraperitoneal daily agar culture of Pseudomonas aeruginosa № 27835 ATCC (injected with 1.5 ml suspension of bacteria, which contained 109 CFU/ml. Fifth (n=15 and sixth (n=15 groups of animals were injected intraperitoneally daily agar culture of Escherichia coli number 25592, ATCC (injected with 1.5 ml of bacteria suspension which contain 109 CFU/ml. Control animals were taken from the experiment by decapitation 3rd day – n=20. Control and infected animals were taken from the experiment by decapitation at 3rd day - n=27, 5th day – n=27 and 7th day – n=26. In the second phase of the experiment Ia (n = 6 and IIa (n = 6 were the control group of rats following administration of the experimental composite preparation consisting amino acids, nucleotides, enzymes, vitamins (MF. In two age groups of animals with inflammation induced by E. coli suspension treated with MF 20 mсl 3- month rats (IIIa group n = 6 and 40 mсl 22-month rats (IVa group n = 6. Ib (n = 6 and IIb (n = 6 were the control group of rats after the injection of comparison, containing mannitol and natural antioxidant betakaroten (PO. In two age

  4. Large-scale atmospheric circulation biases and changes in global climate model simulations and their importance for climate change in Central Europe

    Directory of Open Access Journals (Sweden)

    A. P. van Ulden

    2006-01-01

    Full Text Available The quality of global sea level pressure patterns has been assessed for simulations by 23 coupled climate models. Most models showed high pattern correlations. With respect to the explained spatial variance, many models showed serious large-scale deficiencies, especially at mid-latitudes. Five models performed well at all latitudes and for each month of the year. Three models had a reasonable skill. We selected the five models with the best pressure patterns for a more detailed assessment of their simulations of the climate in Central Europe. We analysed observations and simulations of monthly mean geostrophic flow indices and of monthly mean temperature and precipitation. We used three geostrophic flow indices: the west component and south component of the geostrophic wind at the surface and the geostrophic vorticity. We found that circulation biases were important, and affected precipitation in particular. Apart from these circulation biases, the models showed other biases in temperature and precipitation, which were for some models larger than the circulation induced biases. For the 21st century the five models simulated quite different changes in circulation, precipitation and temperature. Precipitation changes appear to be primarily caused by circulation changes. Since the models show widely different circulation changes, especially in late summer, precipitation changes vary widely between the models as well. Some models simulate severe drying in late summer, while one model simulates significant precipitation increases in late summer. With respect to the mean temperature the circulation changes were important, but not dominant. However, changes in the distribution of monthly mean temperatures, do show large indirect influences of circulation changes. Especially in late summer, two models simulate very strong warming of warm months, which can be attributed to severe summer drying in the simulations by these models. The models differ also

  5. Precipitation response to solar geoengineering in a high-resolution tropical-cyclone permitting coupled general circulation model

    Science.gov (United States)

    Irvine, P. J.; Keith, D.; Dykema, J. A.; Vecchi, G. A.; Horowitz, L. W.

    2016-12-01

    Solar geoengineering may limit or even halt the rise in global-average surface temperatures. Evidence from the geoMIP model intercomparison project shows that idealized geoengineering can greatly reduce temperature changes on a region-by-region basis. If solar geoengineering is used to hold radiative forcing or surface temperatures constant in the face of rising CO2, then the global evaporation and precipitation rates will be reduced below pre-industrial. The spartial and frequency distribution of the precipitation response is, however, much less well understood. There is limited evidence that solar geoengineering may reduce extreme precipitation events more that it reduces mean precipitation, but that evidence is based on relatively course resolution models that may to a poor job representing the distribution of extreme precipitation in the current climate. The response of global and regional climate, as well as tropical cyclone (TC) activity, to increasing solar geoengineering is explored through experiments with climate models spanning a broad range of atmospheric resolutions. Solar geoengineering is represented by an idealized adjustment of the solar constant that roughly halves the rate of increase in radiative forcing in a scenario with increasing CO2 concentration. The coarsest resolution model has approximately a 2-degree global resolution, representative of the typical resolution of past GCMs used to explore global response to CO2 increase, and its response is compared to that of two tropical cyclone permitting GCMs of approximately 0.5 and 0.25 degree resolution (FLOR and HiFLOR). The models have exactly the same ocean and sea-ice components, as well as the same parameterizations and parameter settings. These high-resolution models are used for real-time seasonal prediction, providing a unified framework for seasonal-to-multidecadal climate modeling. We assess the extreme precipitation response, comparing the frequency distribution of extreme events with

  6. Assessing the ability of isotope-enabled General Circulation Models to simulate the variability of Iceland water vapor isotopic composition

    Science.gov (United States)

    Erla Sveinbjornsdottir, Arny; Steen-Larsen, Hans Christian; Jonsson, Thorsteinn; Ritter, Francois; Riser, Camilla; Messon-Delmotte, Valerie; Bonne, Jean Louis; Dahl-Jensen, Dorthe

    2014-05-01

    During the fall of 2010 we installed an autonomous water vapor spectroscopy laser (Los Gatos Research analyzer) in a lighthouse on the Southwest coast of Iceland (63.83°N, 21.47°W). Despite initial significant problems with volcanic ash, high wind, and attack of sea gulls, the system has been continuously operational since the end of 2011 with limited down time. The system automatically performs calibration every 2 hours, which results in high accuracy and precision allowing for analysis of the second order parameter, d-excess, in the water vapor. We find a strong linear relationship between d-excess and local relative humidity (RH) when normalized to SST. The observed slope of approximately -45 o/oo/% is similar to theoretical predictions by Merlivat and Jouzel [1979] for smooth surface, but the calculated intercept is significant lower than predicted. Despite this good linear agreement with theoretical calculations, mismatches arise between the simulated seasonal cycle of water vapour isotopic composition using LMDZiso GCM nudged to large-scale winds from atmospheric analyses, and our data. The GCM is not able to capture seasonal variations in local RH, nor seasonal variations in d-excess. Based on daily data, the performance of LMDZiso to resolve day-to-day variability is measured based on the strength of the correlation coefficient between observations and model outputs. This correlation coefficient reaches ~0.8 for surface absolute humidity, but decreases to ~0.6 for δD and ~0.45 d-excess. Moreover, the magnitude of day-to-day humidity variations is also underestimated by LMDZiso, which can explain the underestimated magnitude of isotopic depletion. Finally, the simulated and observed d-excess vs. RH has similar slopes. We conclude that the under-estimation of d-excess variability may partly arise from the poor performance of the humidity simulations.

  7. [Effect of dexmedetomidine and midazolam on respiration and circulation functions in patients undergoing open heart surgery under acupuncture-assisted general anesthesia].

    Science.gov (United States)

    Tang, Wei; Wang, Jian; Fu, Guo-Qiang; Yuan, Lan

    2014-06-01

    To evaluate the effect of Dexmedetomidine and Midazolam on respiratory and circulation in patients experiencing open heart surgery under acupuncture-assisted general anesthesia. Sixty patients undergoing open heart surgery (cardiac valve replacement surgery and aortic valve replacement surgery) were randomly and equally divided into Dexmedetomidine (D) and Midazolam (M) groups. Electroacupuncture (EA) was applied to bilateral Yunmen (LU 2), Zhongfu (LU1), Lieque (LU7) and Neiguan (PC6). For patients of group D, Dexmedetomidine (i.v., loading dose: 1 microg/kg, and succedent dose: 0.2-1 microg x kg(-1) x h(-1)) was given. For patients of group M, Midazolam (i.v., loading dose: 0.05 mg/kg, succedent dose: 0.01-0.03 mg x kg(-1) x h(-1)) was given. Arterial oxygen pressure (PaO2), arterial carbondioxide tension (PaCO2), O2 saturation (SPO2), mean arterial pressure (MAP), heart rate (HR), anesthetic effect, time of spontaneous breathing recovery, and time of resuscitation were recorded before operation (T0), immediately after skin incision (T1), immediately after sternotomy (T2), before suspension of cardiopulmonary bypass (CPB, T3), immediately after cardiac re-beating (T4), immediately after CPB cessation (T5), and at the end of surgery (T6). Before operation, no significant differences were found between the group D and M in the levels of PaO2, PaCO2 and SPO2 (P > 0.05). The PaO2 and SPO2 levels after skin incision, sternotomy, before suspension of CPB and at the end of surgery were significantly lower in group M than in group D (P surgery, and HR after skin incision, sternotomy, before suspension of CPB, after heart re-beating,after CPB cessation and at the end of surgery in group M were considerably higher than those in group D (P surgery, in the PaO2, PaCO2 and SPO2 levels at the time-points of post-cardiac re-beating, and after CPB cessation (P > 0.05). It suggested that the respiration and circulation states in group D were more smoothly than those in group M

  8. Possible combined influences of absorbing aerosols and anomalous atmospheric circulation on summertime diurnal temperature range variation over the middle and lower reaches of the Yangtze River

    Science.gov (United States)

    Cai, Jiaxi; Guan, Zhaoyong; Ma, Fenhua

    2016-12-01

    Based on the temperature data from the China Meteorological Administration, NCEP-NCAR reanalysis data, and the TOMS Aerosol Index (AI), we analyze the variations in the summertime diurnal temperature range (DTR) and temperature maxima in the middle and lower reaches of the Yangtze River (MLRYR) in China. The possible relationships between the direct warming effect of the absorbing aerosol and temperature variations are further investigated, although with some uncertainties. It is found that the summertime DTR exhibits a decreasing trend over the most recent 50 years, along with a slight increasing tendency since the 1980s. The trend of the maximum temperature is in agreement with those of the DTR and the absorbing aerosols. To investigate the causes of the large anomalies in the temperature maxima, composite analyses of the circulation anomalies are performed. When anomalous AI and anomalous maximum temperature over the MLRYR have the same sign, an anomalous circulation with a quasi-barotropic structure occurs there. This anomalous circulation is modulated by the Rossby wave energy propagations from the regions northwest of the MLRYR and influences the northwestern Pacific subtropical high over the MLRYR. In combination with aerosols, the anomalous circulation may increase the maximum temperature in this region. Conversely, when the anomalous AI and anomalous maximum temperature in the MLRYR have opposite signs, the anomalous circulation is not equivalently barotropic, which possibly offsets the warming effect of aerosols on the maximum temperature changes in this region. These results are helpful for a better understanding of the DTR changes and the occurrences of temperature extremes in the MLRYR region during boreal summer.

  9. Use of ARM observations and numerical models to determine radiative and latent heating profiles of mesoscale convective systems for general circulation models

    Energy Technology Data Exchange (ETDEWEB)

    Tao, Wei-Kuo; Houze, Robert, A., Jr.; Zeng, Xiping

    2013-03-14

    This three-year project, in cooperation with Professor Bob Houze at University of Washington, has been successfully finished as planned. Both ARM (the Atmospheric Radiation Measurement Program) data and cloud-resolving model (CRM) simulations were used to identify the water budgets of clouds observed in two international field campaigns. The research results achieved shed light on several key processes of clouds in climate change (or general circulation models), which are summarized below. 1. Revealed the effect of mineral dust on mesoscale convective systems (MCSs) Two international field campaigns near a desert and a tropical coast provided unique data to drive and evaluate CRM simulations, which are TWP-ICE (the Tropical Warm Pool International Cloud Experiment) and AMMA (the African Monsoon Multidisciplinary Analysis). Studies of the two campaign data were contrasted, revealing that much mineral dust can bring about large MCSs via ice nucleation and clouds. This result was reported as a PI presentation in the 3rd ASR Science Team meeting held in Arlington, Virginia in March 2012. A paper on the studies was published in the Journal of the Atmospheric Sciences (Zeng et al. 2013). 2. Identified the effect of convective downdrafts on ice crystal concentration Using the large-scale forcing data from TWP-ICE, ARM-SGP (the Southern Great Plains) and other field campaigns, Goddard CRM simulations were carried out in comparison with radar and satellite observations. The comparison between model and observations revealed that convective downdrafts could increase ice crystal concentration by up to three or four orders, which is a key to quantitatively represent the indirect effects of ice nuclei, a kind of aerosol, on clouds and radiation in the Tropics. This result was published in the Journal of the Atmospheric Sciences (Zeng et al. 2011) and summarized in the DOE/ASR Research Highlights Summaries (see http://www.arm.gov/science/highlights/RMjY5/view). 3. Used radar

  10. Arctic circulation regimes.

    Science.gov (United States)

    Proshutinsky, Andrey; Dukhovskoy, Dmitry; Timmermans, Mary-Louise; Krishfield, Richard; Bamber, Jonathan L

    2015-10-13

    Between 1948 and 1996, mean annual environmental parameters in the Arctic experienced a well-pronounced decadal variability with two basic circulation patterns: cyclonic and anticyclonic alternating at 5 to 7 year intervals. During cyclonic regimes, low sea-level atmospheric pressure (SLP) dominated over the Arctic Ocean driving sea ice and the upper ocean counterclockwise; the Arctic atmosphere was relatively warm and humid, and freshwater flux from the Arctic Ocean towards the subarctic seas was intensified. By contrast, during anticylonic circulation regimes, high SLP dominated driving sea ice and the upper ocean clockwise. Meanwhile, the atmosphere was cold and dry and the freshwater flux from the Arctic to the subarctic seas was reduced. Since 1997, however, the Arctic system has been under the influence of an anticyclonic circulation regime (17 years) with a set of environmental parameters that are atypical for this regime. We discuss a hypothesis explaining the causes and mechanisms regulating the intensity and duration of Arctic circulation regimes, and speculate how changes in freshwater fluxes from the Arctic Ocean and Greenland impact environmental conditions and interrupt their decadal variability. © 2015 The Authors.

  11. Control of primary production in the Arctic by nutrients and light: insights from a high resolution ocean general circulation model

    Directory of Open Access Journals (Sweden)

    E. E. Popova

    2010-11-01

    Full Text Available Until recently, the Arctic Basin was generally considered to be a low productivity area and was afforded little attention in global- or even basin-scale ecosystem modelling studies. Due to anthropogenic climate change however, the sea ice cover of the Arctic Ocean is undergoing an unexpectedly fast retreat, exposing increasingly large areas of the basin to sunlight. As indicated by existing Arctic phenomena such as ice-edge blooms, this decline in sea-ice is liable to encourage pronounced growth of phytoplankton in summer and poses pressing questions concerning the future of Arctic ecosystems. It thus provides a strong impetus to modelling of this region.

    The Arctic Ocean is an area where plankton productivity is heavily influenced by physical factors. As these factors are strongly responding to climate change, we analyse here the results from simulations of the 1/4° resolution global ocean NEMO (Nucleus for European Modelling of the Ocean model coupled with the MEDUSA (Model for Ecosystem Dynamics, carbon Utilisation, Sequestration and Acidification biogeochemical model, with a particular focus on the Arctic basin. Simulated productivity is consistent with the limited observations for the Arctic, with significant production occurring both under the sea-ice and at the thermocline, locations that are difficult to sample in the field.

    Results also indicate that a substantial fraction of the variability in Arctic primary production can be explained by two key physical factors: (i the maximum penetration of winter mixing, which determines the amount of nutrients available for summer primary production, and (ii short-wave radiation at the ocean surface, which controls the magnitude of phytoplankton blooms. A strong empirical correlation was found in the model output between primary production and these two factors, highlighting the importance of physical processes in the Arctic Ocean.

  12. Persistent Cold States of the Tropical Pacific Ocean in an Intermediate Coupled Model and a General Circulation Model

    Science.gov (United States)

    Ramesh, N.; Cane, M. A.; Seager, R.

    2014-12-01

    The tropical Pacific Ocean has persistently cool sea surface temperature (SST) anomalies that last several years to a decade, with either no El Niño events or very few weak El Niño events. These have been shown to cause large-scale droughts in the extratropics[i], including the major North American droughts such as the 1930s Dust Bowl, and may also be responsible for modulating the global mean surface temperature[ii]. Here we show that two models with different levels of complexity - the Zebiak-Cane model and the Geophysical Fluid Dynamics Laboratory Coupled Model version 2.1 - are able to produce such periods in a realistic manner. We then test the predictability of these periods in the Zebiak-Cane model using an ensemble of experiments with perturbed initial states. Our results show that the cool mean state is modestly predictable, while the lack of El Niño events during these cool periods is not. These results have implications for our understanding of the origins of such persistent cool states and the possibility of improving predictions of large-scale droughts. Further, we apply this method of using an ensemble of model simulations with perturbed initial states to make retrospective forecasts and to forecast the mean state of the tropical Pacific Ocean for the upcoming decade. Our results suggest, albeit with low confidence, that the current cool mean state will persist. This could imply the continuation of the drier than normal conditions that have, in general, afflicted southwest North America since the 1997/98 El Niño, as well as the current pause in global warming. [i] C. Herweijer and R. Seager, "The global footprint of persistent extra-tropical drought in the instrumental era," International Journal of Climatology, vol. 28, pp. 1761-1774, 2008. [ii] G. A. Meehl, J. M. Arblaster, J. T. Fasullo, A. Hu and K. E. Trenberth, "Model-based evidence of deep-ocean heat uptake during surface-temperature hiatus periods," Nature Climate Change, vol. 1, pp. 360

  13. Can we determine what controls the spatio-temporal distribution of d-excess and 17O-excess in precipitation using the LMDZ general circulation model?

    Directory of Open Access Journals (Sweden)

    C. Risi

    2013-09-01

    Full Text Available Combined measurements of the H218O and HDO isotopic ratios in precipitation, leading to second-order parameter D-excess, have provided additional constraints on past climates compared to the H218O isotopic ratio alone. More recently, measurements of H217O have led to another second-order parameter: 17O-excess. Recent studies suggest that 17O-excess in polar ice may provide information on evaporative conditions at the moisture source. However, the processes controlling the spatio-temporal distribution of 17O-excess are still far from being fully understood. We use the isotopic general circulation model (GCM LMDZ to better understand what controls d-excess and 17O-excess in precipitation at present-day (PD and during the last glacial maximum (LGM. The simulation of D-excess and 17O-excess is evaluated against measurements in meteoric water, water vapor and polar ice cores. A set of sensitivity tests and diagnostics are used to quantify the relative effects of evaporative conditions (sea surface temperature and relative humidity, Rayleigh distillation, mixing between vapors from different origins, precipitation re-evaporation and supersaturation during condensation at low temperature. In LMDZ, simulations suggest that in the tropics convective processes and rain re-evaporation are important controls on precipitation D-excess and 17O-excess. In higher latitudes, the effect of distillation, mixing between vapors from different origins and supersaturation are the most important controls. For example, the lower d-excess and 17O-excess at LGM simulated at LGM are mainly due to the supersaturation effect. The effect of supersaturation is however very sensitive to a parameter whose tuning would require more measurements and laboratory experiments. Evaporative conditions had previously been suggested to be key controlling factors of d-excess and 17O-excess, but LMDZ underestimates their role. More generally, some shortcomings in the simulation of 17O

  14. ATMOSPHERIC DYNAMICS OF TERRESTRIAL EXOPLANETS OVER A WIDE RANGE OF ORBITAL AND ATMOSPHERIC PARAMETERS

    Energy Technology Data Exchange (ETDEWEB)

    Kaspi, Yohai [Department of Earth and Planetary Sciences, Weizmann Institute of Science, 234 Herzl st., 76100, Rehovot (Israel); Showman, Adam P., E-mail: yohai.kaspi@weizmann.ac.il [Department of Planetary Sciences and Lunar and Planetary Laboratory, The University of Arizona, 1629 University Blvd., Tucson, AZ 85721 (United States)

    2015-05-01

    The recent discoveries of terrestrial exoplanets and super-Earths extending over a broad range of orbital and physical parameters suggest that these planets will span a wide range of climatic regimes. Characterization of the atmospheres of warm super-Earths has already begun and will be extended to smaller and more distant planets over the coming decade. The habitability of these worlds may be strongly affected by their three-dimensional atmospheric circulation regimes, since the global climate feedbacks that control the inner and outer edges of the habitable zone—including transitions to Snowball-like states and runaway-greenhouse feedbacks—depend on the equator-to-pole temperature differences, patterns of relative humidity, and other aspects of the dynamics. Here, using an idealized moist atmospheric general circulation model including a hydrological cycle, we study the dynamical principles governing the atmospheric dynamics on such planets. We show how the planetary rotation rate, stellar flux, atmospheric mass, surface gravity, optical thickness, and planetary radius affect the atmospheric circulation and temperature distribution on such planets. Our simulations demonstrate that equator-to-pole temperature differences, meridional heat transport rates, structure and strength of the winds, and the hydrological cycle vary strongly with these parameters, implying that the sensitivity of the planet to global climate feedbacks will depend significantly on the atmospheric circulation. We elucidate the possible climatic regimes and diagnose the mechanisms controlling the formation of atmospheric jet streams, Hadley and Ferrel cells, and latitudinal temperature differences. Finally, we discuss the implications for understanding how the atmospheric circulation influences the global climate.

  15. On the General Theory of Thermal and Gravitational Excitation of Atmospheric Oscillations

    Directory of Open Access Journals (Sweden)

    f. Mariani

    1959-06-01

    Full Text Available In questo lavoro si considera in forma generale la teoria delle oscillazionidi marea della atmosfera, di origine sia gravitazionale sia termica,assumendo la corretta variazione con la quota della accelerazione di aravità g e del raggio vettore R. La equazione fondamentale che descrive il fenomenodi marea viene risolta separatamente nei due casi di oscillazionipuramente gravitazionali e di oscillazioni puramente termiche, per un modellodi atmosfera {fig. 1 ottenuto approssimando con tratti lineari la effettivavariazione con la quota della scala delle altezze H.Rispetto al caso classico che g ed R non variino con la quota, si constatanel caso puramente gravitazionale un aumento del periodo di risonanzadella atmosfera di qualche minuto-, la ampiezza di risonanza al suoloè invece circa 1.5 volte inferiore-, il più notevole effetto è tuttavia un notevoleinnalzamento, da circa 35 a circa 80 km, della quota a cui la oscillazionedi pressione cambia di segno. Risultati sostanzialmente analoghi valgonoper la oscillazione di origine puramente termica, in quanto in condizionidi risonanza le oscillazioni della pressione nei due casi tendono aidentificarsi.Si calcola infine la ampiezza di oscillazione della temperatura prodottadalla oscillazione di pressione e si trova che essa è dell'ordine dei decimidi grado centigrado, in accordo con le indicazioni sperimentali.

  16. The Relationship of Loss, Mean Age of Air and the Distribution of CFC's to Stratospheric Circulation and Implications for Atmospheric Lifetimes

    Science.gov (United States)

    Douglas, A. R.; Stolarski, R. S.; Schoeberl, M. R.; Jackman, C. H.; Gupta, M. L.; Newman, P. A.; Nielsen, J. E.; Fleming, E. L.

    2008-01-01

    Model-derived estimates of the annually integrated destruction and lifetime for various ozone depleting substances (ODSs) depend on the simulated stratospheric transport and mixing in the global model used to produce the estimate. Observations in the middle and high latitude lower stratosphere show that the mean age of an air parcel (i.e., the time since its stratospheric entry) is related to the fractional release for the ODs (i.e., the amount of the ODS that has been destroyed relative to the amount at the time of stratospheric entry). We use back trajectory calculations to produce an age spectrum, and explain the relationship between the mean age and the fractional release by showing that older elements in the age spectrum have experienced higher altitudes and greater ODs destruction than younger elements. In our study, models with faster circulations produce distributions for the age-of-air that are 'young' compared to a distribution derived from observations. These models also fail to reproduce the observed relationship between the mean age of air and the fractional release. Models with slower circulations produce both realistic distributions for mean age and a realistic relationship between mean age and fractional release. These models also produce a CFCl3 lifetime of approximately 56 years, longer than the 45 year lifetime used to project future mixing ratios. We find that the use of flux boundary conditions in assessment models would have several advantages, including consistency between ODS evolution and simulated loss even if the simulated residual circulation changes due to climate change.

  17. Implementation of non-local boundary layer schemes in the Regional Atmospheric Modeling System and its impact on simulated mesoscale circulations

    NARCIS (Netherlands)

    Gómez, I.; Ronda, R.J.; Caselles, V.; Estrela, M.J.

    2016-01-01

    This paper proposes the implementation of different non-local Planetary Boundary Layer schemes within the Regional Atmospheric Modeling System (RAMS) model. The two selected PBL parameterizations are the Medium-Range Forecast (MRF) PBL and its updated version, known as the Yonsei University (YSU)

  18. Dynamics of Massive Atmospheres

    Science.gov (United States)

    Chemke, Rei; Kaspi, Yohai

    2017-10-01

    The many recently discovered terrestrial exoplanets are expected to hold a wide range of atmospheric masses. Here the dynamic-thermodynamic effects of atmospheric mass on atmospheric circulation are studied using an idealized global circulation model by systematically varying the atmospheric surface pressure. On an Earth analog planet, an increase in atmospheric mass weakens the Hadley circulation and decreases its latitudinal extent. These changes are found to be related to the reduction of the convective fluxes and net radiative cooling (due to the higher atmospheric heat capacity), which, respectively, cool the upper troposphere at mid-low latitudes and warm the troposphere at high latitudes. These together decrease the meridional temperature gradient, tropopause height and static stability. The reduction of these parameters, which play a key role in affecting the flow properties of the tropical circulation, weakens and contracts the Hadley circulation. The reduction of the meridional temperature gradient also decreases the extraction of mean potential energy to the eddy fields and the mean kinetic energy, which weakens the extratropical circulation. The decrease of the eddy kinetic energy decreases the Rhines wavelength, which is found to follow the meridional jet scale. The contraction of the jet scale in the extratropics results in multiple jets and meridional circulation cells as the atmospheric mass increases.

  19. Variations in the temperature and circulation of the atmosphere during the 11-year cycle of solar activity derived from the ERA-Interim reanalysis data

    Science.gov (United States)

    Gruzdev, A. N.

    2017-07-01

    Using the data of the ERA-Interim reanalysis, we have obtained estimates of changes in temperature, the geopotential and its large-scale zonal harmonics, wind velocity, and potential vorticity in the troposphere and stratosphere of the Northern and Southern hemispheres during the 11-year solar cycle. The estimates have been obtained using the method of multiple linear regression. Specific features of response of the indicated atmospheric parameters to the solar cycle have been revealed in particular regions of the atmosphere for a whole year and dep