WorldWideScience

Sample records for atmospheric circulation

  1. Atmospheric Circulation of Exoplanets

    CERN Document Server

    Showman, Adam P; 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-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 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 d...

  2. Atmospheric Circulation of Terrestrial Exoplanets

    CERN Document Server

    Showman, Adam P; Merlis, Timothy M; Kaspi, Yohai

    2013-01-01

    The investigation of planets around other stars began with the study of gas giants, but is now extending to the discovery and characterization of super-Earths and terrestrial planets. Motivated by this observational tide, we survey the basic dynamical principles governing the atmospheric circulation of terrestrial exoplanets, and discuss the interaction of their circulation with the hydrological cycle and global-scale climate feedbacks. Terrestrial exoplanets occupy a wide range of physical and dynamical conditions, only a small fraction of which have yet been explored in detail. Our approach is to lay out the fundamental dynamical principles governing the atmospheric circulation on terrestrial planets--broadly defined--and show how they can provide a foundation for understanding the atmospheric behavior of these worlds. We first survey basic atmospheric dynamics, including the role of geostrophy, baroclinic instabilities, and jets in the strongly rotating regime (the "extratropics") and the role of the Hadle...

  3. Atmospheric General Circulation Changes under Global Warming

    Science.gov (United States)

    Palipane, Erool

    The work in this thesis is mainly two-fold. First we study the internal variability of the general circulation and focus our study on the annular modes and how important it is to simulate the subsynoptic scales in the circulation. In the next major section we will try to understand the mechanisms of the forced response and the mechanisms leading towards the jet shift from transient evolution in Atmospheric general circulation models. In the first part, in an attempt to assess the benefit of resolving the sub-synoptic to mesoscale processes, the spatial and temporal characteristics of the Annular Modes (AMs), in particular those related to the troposphere-stratosphere interaction, are evaluated for moderate- and high-horizontal resolution simulations with a global atmospheric general circulation model (AGCM), in comparison with the ERA40 re- analysis. Relative to the CMIP-type climate models, the IFS AGCM demonstrates notable improvement in capturing the key characteristics of the AMs. Notably, the performance with the high horizontal resolution version of the model is systematically superior to the moderate resolution on all metrics examined, including the variance of the AMs at different seasons of the year, the intrinsic e-folding time scales of the AMs, and the downward influence from the stratosphere to troposphere in the AMs. Moreover, the high-resolution simulation with a greater persistence in the intrinsic variability of the SAM projects an appreciably larger shift of the surface westerly wind during the Southern Hemisphere summer under climate change. In the second part, the response of the atmospheric circulation to greenhouse gas-induced SST warming is investigated using large ensemble experiments with two AGCMs, with a focus on the robust feature of the poleward shift of the eddy driven jet. In these experiments, large ensembles of simulations are conducted by abruptly switching the SST forcing on from January 1st to focus on the wintertime circulation

  4. Three-dimensional decomposition method of global atmospheric circulation

    Institute of Scientific and Technical Information of China (English)

    LIU HaiTao; HU ShuJuan; XU Ming; CHOU JiFan

    2008-01-01

    By adopting the idea of three-dimensional Walker, Hadley and Rossby stream functions, the global atmospheric circulation can be considered as the sum of three stream functions from a global perspective. Therefore, a mathematical model of three-dimensional decomposition of global atmospheric circulation is proposed and the existence and uniqueness of the model are proved. Besides, the model includes a numerical method leading to no truncation error in the discrete three-dimensional grid points. Results also show that the three-dimensional stream functions exist and are unique for a given velocity field. The mathematical model shows the generalized form of three-dimensional stream functions equal to the velocity field in representing the features of atmospheric motion. Besides, the vertical velocity calculated through the model can represent the main characteristics of the vertical motion. In sum, the three-dimensional decomposition of atmospheric circulation is convenient for the further investigation of the features of global atmospheric motions.

  5. 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

  6. 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)

  7. 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.

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

    CERN Document Server

    Komacek, Thaddeus D

    2016-01-01

    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 shed insight on 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 temperature, atmospheric composition, and potential frictional drag strengths with numerical solutions of the circulation that verify this analytic theory. This analytic 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 r...

  9. NUCLA Circulating Atmospheric Fluidized Bed Demonstration Project

    Energy Technology Data Exchange (ETDEWEB)

    Keith, Raymond E.; Heller, Thomas J.; Bush, Stuart A.

    1991-01-01

    This Annual Report on Colorado-Ute Electric Association's NUCLA Circulating Fluidized Bed (CFB) Demonstration Program covers the period from February 1987 through December 1988. The outline for presentation in this report includes a summary of unit operations along with individual sections covering progress in study plan areas that commenced during this reporting period. These include cold-mode shakedown and calibration, plant commercial performance statistics, unit start-up (cold), coal and limestone preparation and handling, ash handling system performance and operating experience, tubular air heater, baghouse operation and performance, materials monitoring, and reliability monitoring. During this reporting period, the coal-mode shakedown and calibration plan was completed. (VC)

  10. Glacial ocean circulation and stratification explained by reduced atmospheric temperature

    Science.gov (United States)

    Jansen, Malte F.

    2017-01-01

    Earth’s climate has undergone dramatic shifts between glacial and interglacial time periods, with high-latitude temperature changes on the order of 5–10 °C. These climatic shifts have been associated with major rearrangements in the deep ocean circulation and stratification, which have likely played an important role in the observed atmospheric carbon dioxide swings by affecting the partitioning of carbon between the atmosphere and the ocean. The mechanisms by which the deep ocean circulation changed, however, are still unclear and represent a major challenge to our understanding of glacial climates. This study shows that various inferred changes in the deep ocean circulation and stratification between glacial and interglacial climates can be interpreted as a direct consequence of atmospheric temperature differences. Colder atmospheric temperatures lead to increased sea ice cover and formation rate around Antarctica. The associated enhanced brine rejection leads to a strongly increased deep ocean stratification, consistent with high abyssal salinities inferred for the last glacial maximum. The increased stratification goes together with a weakening and shoaling of the interhemispheric overturning circulation, again consistent with proxy evidence for the last glacial. The shallower interhemispheric overturning circulation makes room for slowly moving water of Antarctic origin, which explains the observed middepth radiocarbon age maximum and may play an important role in ocean carbon storage.

  11. Three-dimensional decomposition method of global atmospheric circulation

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    By adopting the idea of three-dimensional Walker, Hadley and Rossby stream functions, the global atmospheric circulation can be considered as the sum of three stream functions from a global per- spective. Therefore, a mathematical model of three-dimensional decomposition of global atmospheric circulation is proposed and the existence and uniqueness of the model are proved. Besides, the model includes a numerical method leading to no truncation error in the discrete three-dimensional grid points. Results also show that the three-dimensional stream functions exist and are unique for a given velocity field. The mathematical model shows the generalized form of three-dimensional stream func- tions equal to the velocity field in representing the features of atmospheric motion. Besides, the vertical velocity calculated through the model can represent the main characteristics of the vertical motion. In sum, the three-dimensional decomposition of atmospheric circulation is convenient for the further in- vestigation of the features of global atmospheric motions.

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

    CERN Document Server

    Knietzsch, Marc-Andre; Lunkeit, Frank

    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 conjunction with significant modification of the general circulation. Up to a maximum about 3PW, an increase of the oceanic heat transport leads to an increase of the global mean near surface temperature and a decrease of its equator-to-pole gradient. For larger 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. A larger oceanic heat transport leads to a reduction of all reservoirs and conversions of the Lorenz energy cycl...

  13. Modelling Saturn's atmospheric circulations and cloud structure with OPUS

    Science.gov (United States)

    Zuchowski, L. C.; Read, P. L.; Yamazaki, Y. H.

    2009-04-01

    We are investigating Saturn's atmospheric circulations and cloud structure in the Northern and Southern hemisphere as initial value problems by use of the Oxford Planetary Unified model System (OPUS), a sophisticated GCM based on the UK Met Office Unified Model. Solving an extended form of the Hydrodynamic Primitive Equations, OPUS is capable of including 40 vertical levels from 0.1 bar to 100 bar. The model was initiated with temperature and balanced thermal wind profiles recently obtained by Cassini's Composite InfraRed Spectrometer (CIRS). A simple cloud scheme for the Jovian planets has been added to OPUS and is employed to model the three major cloud decks (ammonia, ammonium-hydrosulfide and water) on Saturn and the advection of these clouds with the atmosphere. We have already conducted several numerical studies with OPUS, simulating jet scale meridional circulations, the formation of cloud bands and discrete turbulent features on Jupiter. By modelling the dynamics and clouds of Saturn in a similar way, we are hoping to gain further insight into the formation of circulation cells over the zonal jet streams as well as to examine the distribution of atmospheric condensates in response to these motions. The model will also be used to numerically investigate the characteristic features in Saturn's Northern hemisphere. It is envisioned to directly compare the atmospheric configurations obtained for Saturn with previous results from the Jupiter model.

  14. A Study on Planetary Atmospheric Circulations using THOR

    Science.gov (United States)

    Mendonça, João; Grosheintz, Luc; Lukas Grimm, Simon; Heng, Kevin

    2015-12-01

    The large variety of planetary parameters observed leads us to think that exoplanets may show a large range of possible climates. It is therefore of the uttermost importance to investigate the influence of astronomical and planetary bulk parameters in driving the atmospheric circulations. In the solar system the results from planetary spacecraft missions have demonstrated how different the planetary climate and atmospheric circulations can be. The study of exoplanets will require probing a far wider range of physical and orbital parameters than the ones of our neighbor planets. For this reason, such a study will involve exploring an even larger diversity of circulation and climate regimes. Our new atmospheric model, THOR, is intended to be extremely flexible and to explore the large diversity of planetary atmospheres.THOR is part of the Exoclimes Simulation Platform, and is a project of the Exoplanet and Exoclimes Group (see www.exoclime.org). THOR solves the complex atmospheric fluid equations in a rotating sphere (fully compressible - nonhydrostatic system) using an icosahedral grid. The main advantages of using our new platform against other recent exoplanet models is that 1) The atmospheric fluid equations are completely represented and no approximations are used that could compromise the physics of the problem; 2) The model uses for the first time in exoplanet studies, a specific icosahedral grid that solves the pole problem; 3) The interface is user friendly and can be easily adapted to a multitude of atmospheric conditions; 4) By using GPU computation, our code greatly improves the typical code running time.We will present and discuss the first detailed results of our simulations, more specifically of two benchmark tests that are a representative sample of the large range of exoplanetary parameters: Earth-like conditions (the Held-Suarez test) and a tidally locked hot-Jupiter. THOR has successfully passed these tests and is able to determine the main

  15. Culturable bacteria in Himalayan ice in response to atmospheric circulation

    Directory of Open Access Journals (Sweden)

    S. Zhang

    2006-06-01

    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 investigate the seasonal variation of culturable bacteria preserved in a Himalayan ice core. High concentration of culturable bacteria in glacial ice deposited during the pre-monsoon season is attributed to the transportation of continental dust stirred up by the frequent dust storms in Northwest China during spring. This is also confirmed by the spatial distribution of culturable bacteria in Tibetan glaciers. Culturable bacteria deposited during monsoon season are more diverse than other seasons because they derive from both marine air masses and local or regional continental sources. We suggest that microorganisms in Himalayan ice can be used to reconstruct atmospheric circulation.

  16. Analogues of atmospheric circulation to probe extreme and rare events

    Science.gov (United States)

    Yiou, P.

    2015-12-01

    Analogues of atmospheric circulation have had many applications, from weather prediction to the downscaling of climate variables. The main assumptions behind this methodology are that climate variables (such as temperature or precipitation) are linked a large-scale atmospheric predictand, which is usually taken as sea-level pressure, and that such predictands recur through time. They offer a possibility to estimate probability distributions of a climate variable, conditional to patterns of atmospheric circulation. In addition, this methodology allows the quantification of unusual weather patterns that have been observed. I will represent a way to use analogues of circulation for the detection/attribution of extreme events of precipitation and temperature. This approach will be illustrated on test cases, including the warm European winter of 2006/2007, the extremes of precipitation over Southern UK and northwestern France in January 2014, and the European summer of 2015. I will show how this analysis provides a low-cost estimate of the fraction of attributable risk (FAR) for extreme events that verify the above mentioned hypotheses. Such an analysis can be performed in continuous time with reanalysis data and meteorological observations.

  17. 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.

  18. Interactions between clouds and atmospheric circulation in the extratropics

    Science.gov (United States)

    Ceppi, Paulo

    In climate models, the simulation of clouds is known to be particularly problematic, leading to important biases in the climatological energy balance on regional scales, as well as to large uncertainties in the future amount of warming in response to greenhouse gas increase. This thesis explores the connections between clouds and atmospheric circulation in extratropical regions. In particular, we investigate the impacts of clouds and their uncertainties on atmospheric circulation and its response to global warming. We find that clouds have very substantial effects both on the mean circulation and on its future response to warming in climate models. In the mean state, the position of the midlatitude jet correlates well with the midlatitude shortwave cloud-radiative effect (SW CRE), which suffers from very large biases in models. Models in which midlatitude SW CRE is too negative have anomalously cold midlatitudes, leading to an anomalously equatorward jet position. This result is supported by idealized model experiments and appears consistent with the effect of midlatitude baroclinicity changes on eddy activity. This means that an accurate representation of clouds and their radiative effects is essential to correctly portray the mean circulation. In the context of greenhouse gas--forced change, we demonstrate that cloud-radiative changes have a surprisingly large impact on the atmospheric circulation response. This results mainly from the SW cloud feedback, whose specific spatial structure induces low-latitude warming and high-latitude cooling, enhancing midlatitude baroclinicity and favoring a strengthening and poleward shift of the midlatitude jet. This opposes the effects of other major feedbacks (e.g., the water vapor feedback and the longwave cloud feedback), which produce polar-amplified warming and weakened midlatitude baroclinicity. For this reason, cloud-radiative changes explain the majority of the poleward expansion of atmospheric circulation in our model

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

    Directory of Open Access Journals (Sweden)

    M.-A. Knietzsch

    2014-11-01

    Full Text Available 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 conjunction with significant modification of the general circulation. Up to a maximum about 3 PW, an increase of the oceanic heat transport leads to an increase of the global mean near-surface temperature and a decrease of its equator-to-pole gradient. For larger 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. A larger oceanic heat transport leads to a reduction of all reservoirs and conversions of the Lorenz energy cycle but of different relative magnitude for the individual components. The available potential energy of the zonal mean flow and its conversion to eddy available potential energy are affected most. Both the Hadley and Ferrel cell show a decline for increasing oceanic heat transport, with the Hadley cell being more sensitive. Both cells exhibit a poleward shift of their maxima, and the Hadley cell broadens for larger oceanic transports. The partitioning, by means of the Kuo–Eliassen equation, reveals that zonal mean diabatic heating and friction are the most important sources for changes of the Hadley cell, while the behaviour of the Ferrell cell is mostly controlled by friction.

  20. High Resolution Global Modeling of the Atmospheric Circulation

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    An informal review is presented of recent developments in numerical simulation of the global atmospheric circulation with very fine numerical resolution models. The focus is on results obtained recently with versions of the GFDL SKYHI model and the Atmospheric Model for the Earth Simulator (AFES) global atmospheric models. These models have been run with effective horizontal grid resolution of ~10-40 km and fine vertical resolution. The results presented demonstrate the utility of such models for the study of a diverse range of phenomena. Specifically the models are shown to simulate the development of tropical cyclones with peak winds and minimum central pressures comparable to those of the most intense hurricanes actually observed. More fundamentally, the spectrum of energy content in the mesoscale in the flow can be reproduced by these models down to near the smallest explicitly-resolved horizontal scales. In the middle atmosphere it is shown that increasing horizontal resolution can lead to significantly improved overall simulation of the global-scale circulation. The application of the models to two specific problems requiring very fine resolution global will be discussed. The spatial and temporal variability of the vertical eddy flux of zonal momentum associated with gravity waves near the tropopause is evaluated in the very fine resolution AFES model. This is a subject of great importance for understanding and modelling the flow in the middle atmosphere. Then the simulation of the small scale variations of the semidiurnal surface pressure oscillation is analyzed, and the signature of significant topographic modulation of the semidiurnal atmospheric tide is identified.

  1. DOPPLER SIGNATURES OF THE ATMOSPHERIC CIRCULATION ON HOT JUPITERS

    Energy Technology Data Exchange (ETDEWEB)

    Showman, Adam P.; Lewis, Nikole K. [Department of Planetary Sciences and Lunar and Planetary Laboratory, The University of Arizona, 1629 University Boulevard, Tucson, AZ 85721 (United States); Fortney, Jonathan J. [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Shabram, Megan, E-mail: showman@lpl.arizona.edu [Department of Astronomy, University of Florida, 211 Bryant Space Science Center, Gainesville, FL 32611-2055 (United States)

    2013-01-01

    The meteorology of hot Jupiters has been characterized primarily with thermal measurements, but recent observations suggest the possibility of directly detecting the winds by observing the Doppler shift of spectral lines seen during transit. Motivated by these observations, we show how Doppler measurements can place powerful constraints on the meteorology. We show that the atmospheric circulation-and Doppler signature-of hot Jupiters splits into two regimes. Under weak stellar insolation, the day-night thermal forcing generates fast zonal jet streams from the interaction of atmospheric waves with the mean flow. In this regime, air along the terminator (as seen during transit) flows toward Earth in some regions and away from Earth in others, leading to a Doppler signature exhibiting superposed blueshifted and redshifted components. Under intense stellar insolation, however, the strong thermal forcing damps these planetary-scale waves, inhibiting their ability to generate jets. Strong frictional drag likewise damps these waves and inhibits jet formation. As a result, this second regime exhibits a circulation dominated by high-altitude, day-to-night airflow, leading to a predominantly blueshifted Doppler signature during transit. We present state-of-the-art circulation models including non-gray radiative transfer to quantify this regime shift and the resulting Doppler signatures; these models suggest that cool planets like GJ 436b lie in the first regime, HD 189733b is transitional, while planets hotter than HD 209458b lie in the second regime. Moreover, we show how the amplitude of the Doppler shifts constrains the strength of frictional drag in the upper atmospheres of hot Jupiters. If due to winds, the {approx}2 km s{sup -1} blueshift inferred on HD 209458b may require drag time constants as short as 10{sup 4}-10{sup 6} s, possibly the result of Lorentz-force braking on this planet's hot dayside.

  2. Doppler Signatures of the Atmospheric Circulation on Hot Jupiters

    CERN Document Server

    Showman, Adam P; Lewis, Nikole K; Shabram, Megan

    2013-01-01

    The meteorology of hot Jupiters has been characterized primarily with thermal measurements, but recent observations suggest the possibility of directly detecting the winds by observing the Doppler shift of spectral lines seen during transit. Motivated by these observations, we show how Doppler measurements can place powerful constraints on the meteorology. We show that the atmospheric circulation--and Doppler signature--of hot Jupiters splits into two regimes. Under weak stellar insolation, the day-night thermal forcing generates fast zonal jet streams from the interaction of atmospheric waves with the mean flow. In this regime, air along the terminator (as seen during transit) flows toward Earth in some regions and away from Earth in others, leading to a Doppler signature exhibiting superposed blue- and redshifted components. Under intense stellar insolation, however, the strong thermal forcing damps these planetary-scale waves, inhibiting their ability to generate jets. Strong frictional drag likewise damps...

  3. Connection between ozone concentration and atmosphere circulation at peak Moussala

    Science.gov (United States)

    Nojarov, Peter; Ivanov, Peter; Kalapov, Ivo; Penev, Ilia; Drenska, Mirolujba

    2009-09-01

    Connection between ozone concentration and atmosphere circulation is investigated based on measurements at BEO station, peak Moussala (2,925 m a.s.l.), for the period 09 August 2006 to 29 January 2008. Ozone concentration data are collected with UV-analyzer “Environnement O3 42” and meteo data with weather station “Vaisala”. There are measurements of 7Be. Data from NOAA HYSPLIT model for particle trajectories are also used. Eight wind directions and three ranges of wind velocities are employed in the analysis. A comparison of ozone concentrations in upward and downward air transport according to HYSPLIT model is made. The number of cases with ozone concentration above 63 ppb has been counted. Mann-Whitney nonparametric test is employed as a basic statistical method. Correlation between atmosphere pressure and tropospheric ozone content is made. The same is done for 7Be and ozone. The main conclusion is that there is not any local or regional pollution effect detectable at peak Moussala, but most of the ozone measured is due to emissions of hydrocarbons and NO x over a larger region. There could be some regional sources of ozone building substances in southwest direction from peak Moussala. Air transported from the north quarter has higher ozone concentrations compared to the south quarter. In vertical direction, upward transport of air masses shows higher values of ozone concentration. Higher wind velocity is associated with low ozone concentrations at peak Moussala. The annual course of ozone concentration has summer maximum and winter minimum. There is right connection between air pressure and ozone concentration. The same is valid for the correlation between 7Be and ozone. Diurnal ozone course shows daytime maximum in winter and nighttime maximum in summer.

  4. 27.3-day and 13.6-day Atmospheric Tide and Lunar Forcing on Atmospheric Circulation

    Institute of Scientific and Technical Information of China (English)

    LI Guoqing

    2005-01-01

    An analysis of time variations of the earth's length of day (LOD) versus atmospheric geopotential height fields and lunar phase is presented. A strong correlation is found between LOD and geopotential height from which a close relationship is inferred and found between atmospheric circulation and the lunar cycle around the earth. It is found that there is a 27.3-day and 13.6-day east-west oscillation in the atmospheric circulation following the lunar phase change. The lunar revolution around the earth strongly influences the atmospheric circulation. During each lunar cycle around the earth there is, on average, an alternating change of 6.8-day-decrease, 6.8-day-increase, 6.8-day-decrease and 6.8-day-increase in atmospheric zonal wind, atmospheric angular momentum and LOD. The dominant factor producing such an oscillation in atmospheric circulation is the periodic change of lunar declination during the lunar revolution around the earth. The 27.3- day and 13.6-day atmospheric oscillatory phenomenon is akin to a strong atmospheric tide, which is different from the weak atmospheric tides, diurnal and semidiurnal, previously documented in the literature. Also it is different from the tides in the ocean in accordance with their frequency and date of occurrence. Estimation shows that the 27.3-day lunar forcing produces a 1-2 m s-1 change in atmospheric zonal wind. Therefore, it should be considered in models of atmospheric circulation and short and middle term weather forecasting. The physical mechanism and dynamic processes in lunar forcing on atmospheric circulation are discussed.

  5. Winter atmospheric circulation over Europe and the North Atlantic: an intercomparison of reanalysis datasets

    Science.gov (United States)

    Stryhal, Jan; Huth, Radan

    2016-04-01

    Research on atmospheric circulation has been quite common lately and includes e.g. analyses of circulation properties and trends in both reanalysis datasets and circulation model outputs. In many cases, however, studies have been restricted to only one set of data and only one research method. The goal of our present work is to compare the properties of winter European atmospheric circulation in five reanalysis datasets (ERA-40, NCEP/NCAR, JRA-55, ERA-20C, and 20CRv2) over 1961-2000. The main research method we use is an automated circulation classification. In order to bring robust results, however, eight distinct circulation type calendars are defined based on the reanalysed daily mean sea level pressure patterns, for each of the reanalyses and over the total of eight European domains. Subsequently, basic properties of these calendars are computed and compared. Lastly, we show how results of GCM validation can vary if different reanalyses are taken as a benchmark.

  6. Temperature Structure and Atmospheric Circulation of Dry, Tidally Locked Rocky Exoplanets

    CERN Document Server

    Koll, Daniel D B

    2016-01-01

    Next-generation space telescopes will observe the atmospheres of rocky planets orbiting nearby M-dwarfs. Understanding these observations will require well-developed theory in addition to numerical simulations. Here we present theoretical models for the temperature structure and atmospheric circulation of dry, tidally locked rocky exoplanets with grey radiative transfer and test them using a general circulation model (GCM). First, we develop a radiative-convective model that captures surface temperatures of slowly rotating and cool atmospheres. Second, we show that the atmospheric circulation acts as a global heat engine, which places strong constraints on large-scale wind speeds. Third, we develop a radiative-convective-subsiding model which extends our radiative-convective model to hot and thin atmospheres. We find that rocky planets develop large day-night temperature gradients at a ratio of wave-to-radiative timescales up to two orders of magnitude smaller than the value suggested by work on hot Jupiters....

  7. Atmospheric Circulation Influence During Winter on Measurements at Yakutsk Array

    CERN Document Server

    Knurenko, Stanislav

    2014-01-01

    The paper presents long-term observations of the atmosphere in Yakutsk region. Analysis of the data for 40 year period indicates a gradual strengthening of cyclonic activity in the region and hence the increase of the average winter temperature, increase variations of the rest atmosphere, which greatly softens the continental climate of Central Yakutia.

  8. 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.

  9. Interannual and Interdecadal Variations in Atmospheric Circulation Factors and Rainfall in China and Their Relationship

    Institute of Scientific and Technical Information of China (English)

    YAN Huasheng; WAN Yunxia; CHENG Jiangang

    2005-01-01

    Wavelet analysis is used to study the interannual and interdecadal variations of rainfall in China and atmospheric circulation factors, including the key atmospheric oscillations, W, C, E patterns and subtropical high. Regression analysis and correlation analysis are both used to study the relationship of atmospheric circulation factors and China rainfall on different time scale and spatial scale. The results are as follows:(1) The variations of atmospheric circulation and rainfall in China are characterized by interannual and interdecadal scales. The variations of atmospheric circulation and rainfall are composed of interannual and interdecadal variations. It is necessary to separate those two time scales when climate changes and forecast are studied. (2) The variations of China rainfall are due to the interaction of multi-factors rather than single factors. The marked factors which influence the interannual and interdecadal variations are various.Subtropical high is one of the marked factors which influence interannual variations of rainfall, while AO,NAO, and NPO are one of the marked factors which influence interdecadal variations of rainfall. (3) The longer the time scale is, and the larger the spatial scale is, and the more remarkable the relationships between atmospheric circulation and rainfall are.

  10. The impact of atmospheric circulation on the chemistry of the hot Jupiter HD 209458b

    CERN Document Server

    Agundez, M; Iro, N; Selsis, F; Hersant, F; Hebrard, E; Dobrijevic, M

    2012-01-01

    We investigate the effects of atmospheric circulation on the chemistry of the hot Jupiter HD 209458b. We use a simplified dynamical model and a robust chemical network, as opposed to previous studies which have used a three dimensional circulation model coupled to a simple chemical kinetics scheme. The temperature structure and distribution of the main atmospheric constituents are calculated in the limit of an atmosphere that rotates as a solid body with an equatorial rotation rate of 1 km/s. Such motion mimics a uniform zonal wind which resembles the equatorial superrotation structure found by three dimensional circulation models. The uneven heating of this tidally locked planet causes, even in the presence of such a strong zonal wind, large temperature contrasts between the dayside and nightside, of up to 800 K. This would result in important longitudinal variations of some molecular abundances if the atmosphere were at chemical equilibrium. The zonal wind, however, acts as a powerful disequilibrium process...

  11. 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)

  12. Turbulence, superrotation, and general circulation models of the atmosphere of Venus

    Science.gov (United States)

    Izakov, M. N.

    2016-09-01

    The data obtained in space-borne measurements and the findings of turbulence theory show that turbulence, of both small and large scales, has a decisive influence on the structure and dynamics of the atmosphere of Venus. The small-scale turbulence generates anomalous convection, while large-scale turbulence induces the return spectral flux of energy that is the main element of the superrotation mechanism in the atmosphere. Ways for improving the general circulation model of the atmosphere of Venus are proposed.

  13. 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.

  14. NUCLA Circulating Atmospheric Fluidized Bed Demonstration Project. Annual report, 1988

    Energy Technology Data Exchange (ETDEWEB)

    1991-01-01

    This Annual Report on Colorado-Ute Electric Association`s NUCLA Circulating Fluidized Bed (CFB) Demonstration Program covers the period from February 1987 through December 1988. The outline for presentation in this report includes a summary of unit operations along with individual sections covering progress in study plan areas that commenced during this reporting period. These include cold-mode shakedown and calibration, plant commercial performance statistics, unit start-up (cold), coal and limestone preparation and handling, ash handling system performance and operating experience, tubular air heater, baghouse operation and performance, materials monitoring, and reliability monitoring. During this reporting period, the coal-mode shakedown and calibration plan was completed. (VC)

  15. Projections of Southern Hemisphere atmospheric circulation interannual variability

    Science.gov (United States)

    Grainger, Simon; Frederiksen, Carsten S.; Zheng, Xiaogu

    2017-02-01

    An analysis is made of the coherent patterns, or modes, of interannual variability of Southern Hemisphere 500 hPa geopotential height field under current and projected climate change scenarios. Using three separate multi-model ensembles (MMEs) of coupled model intercomparison project phase 5 (CMIP5) models, the interannual variability of the seasonal mean is separated into components related to (1) intraseasonal processes; (2) slowly-varying internal dynamics; and (3) the slowly-varying response to external changes in radiative forcing. In the CMIP5 RCP8.5 and RCP4.5 experiments, there is very little change in the twenty-first century in the intraseasonal component modes, related to the Southern annular mode (SAM) and mid-latitude wave processes. The leading three slowly-varying internal component modes are related to SAM, the El Niño-Southern oscillation (ENSO), and the South Pacific wave (SPW). Structural changes in the slow-internal SAM and ENSO modes do not exceed a qualitative estimate of the spatial sampling error, but there is a consistent increase in the ENSO-related variance. Changes in the SPW mode exceed the sampling error threshold, but cannot be further attributed. Changes in the dominant slowly-varying external mode are related to projected changes in radiative forcing. They reflect thermal expansion of the tropical troposphere and associated changes in the Hadley Cell circulation. Changes in the externally-forced associated variance in the RCP8.5 experiment are an order of magnitude greater than for the internal components, indicating that the SH seasonal mean circulation will be even more dominated by a SAM-like annular structure. Across the three MMEs, there is convergence in the projected response in the slow-external component.

  16. The atmospheric circulation of the super Earth GJ 1214b: Dependence on composition and metallicity

    CERN Document Server

    Kataria, Tiffany; Fortney, Jonathan J; Marley, Mark S; Freedman, Richard S

    2014-01-01

    We present three-dimensional atmospheric circulation models of GJ 1214b, a 2.7 Earth-radius, 6.5 Earth-mass super Earth detected by the MEarth survey. Here we explore the planet's circulation as a function of atmospheric metallicity and atmospheric composition, modeling atmospheres with a low mean-molecular weight (i.e., H2-dominated) and a high mean-molecular weight (i.e. water- and CO2-dominated). We find that atmospheres with a low mean-molecular weight have strong day-night temperature variations at pressures above the infrared photosphere that lead to equatorial superrotation. For these atmospheres, the enhancement of atmospheric opacities with increasing metallicity lead to shallower atmospheric heating, larger day-night temperature variations and hence stronger superrotation. In comparison, atmospheres with a high mean-molecular weight have larger day-night and equator-to-pole temperature variations than low mean-molecular weight atmospheres, but differences in opacity structure and energy budget lead ...

  17. Relation among Summer Rainfall in South Shandong and High Pressure in South Asia and Atmospheric Circulation

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    [Objective] The aim was to study the relation among summer rainfall in south Shandong and high pressure in South Asia and atmospheric circulation.[Method] Taking the precipitation in south Shandong along the Yellow River and Huaihe River,using the NCEP/NCAR data and summer rainfall data in south Shandong in summer from 1961 to 2005,the characteristics of high pressure in South Asia and atmospheric circulation in drought year and flood year in summer in south Shandong Province were expounded.The mechanism of...

  18. 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.

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

    Science.gov (United States)

    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 unravelled, the vast dust deposits of central China support the presence of arid conditions and modern atmospheric pathways for the last 25 million years (Myr). Here, we present provenance data from older (42–33 Myr) dust deposits, at a time when the Tibetan Plateau was less developed, the Paratethys sea still present in central Asia and atmospheric pCO2 much higher. Our results show that dust sources and near-surface atmospheric circulation have changed little since at least 42 Myr. Our findings indicate that the locus of central Asian high pressures and concurrent aridity is a resilient feature only modulated by mountain building, global cooling and sea retreat. PMID:27488503

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

    Science.gov (United States)

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

    2016-08-01

    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 unravelled, the vast dust deposits of central China support the presence of arid conditions and modern atmospheric pathways for the last 25 million years (Myr). Here, we present provenance data from older (42-33 Myr) dust deposits, at a time when the Tibetan Plateau was less developed, the Paratethys sea still present in central Asia and atmospheric pCO2 much higher. Our results show that dust sources and near-surface atmospheric circulation have changed little since at least 42 Myr. Our findings indicate that the locus of central Asian high pressures and concurrent aridity is a resilient feature only modulated by mountain building, global cooling and sea retreat.

  1. Global Coupled Ocean-Atmosphere General Circulation Models in LASG/IAP

    Institute of Scientific and Technical Information of China (English)

    俞永强; 张学洪; 郭裕福

    2004-01-01

    Coupled ocean-atmospheric general circulation models are the only tools to quantitatively simulate the climate system. Since the end of the 1980s, a group of scientists in the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG), Institute of Atmospheric Physics (IAP), Chinese Academy of Sciences (CAS), have been working to develop a global OGCM and a global coupled ocean-atmosphere general circulation model (CGCM). From the original flux anomalycoupling model developed in the beginning of the 1990s to the latest directly-coupling model, LASG scientists have developed four global coupled GCMs. This study summarizes the development history of these models and describes the third and fourth coupled GCMs and selected applications. Strengths and weaknesses of these models are highlighted.

  2. The atmospheric circulation of a nine-hot Jupiter sample: Probing circulation and chemistry over a wide phase space

    CERN Document Server

    Kataria, Tiffany; Lewis, Nikole K; Visscher, Channon; Showman, Adam P; Fortney, Jonathan J; Marley, Mark S

    2016-01-01

    We present results from an atmospheric circulation study of nine hot Jupiters that comprise a large transmission spectral survey using the Hubble and Spitzer Space Telescopes. These observations exhibit a range of spectral behavior over optical and infrared wavelengths which suggest diverse cloud and haze properties in their atmospheres. By utilizing the specific system parameters for each planet, we naturally probe a wide phase space in planet radius, gravity, orbital period, and equilibrium temperature. First, we show that our model "grid" recovers trends shown in traditional parametric studies of hot Jupiters, particularly equatorial superrotation and increased day-night temperature contrast with increasing equilibrium temperature. We show how spatial temperature variations, particularly between the dayside and nightside and west and east terminators, can vary by hundreds of K, which could imply large variations in Na, K, CO and CH4 abundances in those regions. These chemical variations can be large enough...

  3. Impact of variations of gravitational acceleration on the general circulation of the planetary atmosphere

    Science.gov (United States)

    Kilic, Cevahir; Raible, Christoph C.; Stocker, Thomas F.; Kirk, Edilbert

    2017-01-01

    Fundamental to the redistribution of energy in a planetary atmosphere is the general circulation and its meridional structure. We use a general circulation model of the atmosphere in an aquaplanet configuration with prescribed sea surface temperature and investigate the influence of the gravitational acceleration g on the structure of the circulation. For g =g0 = 9.81 ms-2 , three meridional cells exist in each hemisphere. Up to about g /g0 = 1.4 all cells increase in strength. Further increasing this ratio results in a weakening of the thermally indirect cell, such that a two- and finally a one-cell structure of the meridional circulation develops in each hemisphere. This transition is explained by the primary driver of the thermally direct Hadley cell: the diabatic heating at the equator which is proportional to g. The analysis of the energetics of the atmospheric circulation based on the Lorenz energy cycle supports this finding. For Earth-like gravitational accelerations transient eddies are primarily responsible for the meridional heat flux. For large gravitational accelerations, the direct zonal mean conversion of energy dominates the meridional heat flux.

  4. The influence of glacial ice sheets on Atlantic meridional overturning circulation through atmospheric circulation change under glacial climate

    Science.gov (United States)

    Sherriff-Tadano, Sam; Abe-Ouchi, Ayako; Yoshimori, Masakazu; Oka, Akira; Chan, Wing-Le

    2016-04-01

    Recent coupled modeling studies have shown that the existence of the glacial ice sheets intensifies the Atlantic meridional overturning circulation (AMOC). Since this may play an important role in maintaining a strong AMOC over the last glacial period, which is suggested by recent reconstruction study, it is very important to understand the process by which glacial ice sheets intensify the AMOC. Here, a decoupled simulation is conducted to investigate the effect of wind change due to glacial ice sheets on the AMOC, the crucial region where wind modifies the AMOC and the mechanism, which remained elusive in previous studies. First, from atmospheric general circulation model (AGCM) experiments, the effect of glacial ice sheets on the surface wind is evaluated. Second, from ocean general circulation model (OGCM) experiments, the influence of the wind stress change on the AMOC is evaluated by applying only the changes in the surface wind as a boundary condition, while leaving surface heat and freshwater fluxes unchanged. Moreover, several sensitivity experiments are conducted. Using the AGCM, glacial ice sheets are applied individually. Using the OGCM, changes in the wind are applied regionally or at different magnitudes, ranging from the full glacial to modern levels. These experiments demonstrate that glacial ice sheets intensify the AMOC through an increase in the wind stress curl mainly at the North Atlantic mid-latitudes. This intensification is caused by the increased Ekman upwelling and gyre transport of salt while the change in sea ice transport works as a negative, though minor, feedback.

  5. Radiosonde observational evidence of the influence of extreme SST gradient upon atmospheric meso-scale circulation

    Science.gov (United States)

    Nishikawa, H.; Tachibana, Y.; Udagawa, Y.

    2012-12-01

    Although the influence of the anomalous midlatitude SST upon atmospheric local circulation has been getting common in particular over the Kuroshio and the Gulf Stream regions, observational studies on the influence of the Okhotsk Sea, which is to the north of the Kuroshio, upon the atmospheric local circulation is much less than those of the Kuroshio. The climate of the Okhotsk SST is very peculiar. Extremely cold SST spots, whose summertime SST is lower than 5 Celsius degrees, are formed around Kuril Islands. Because SSTs are generally determined by local air-sea interaction as well as temperature advection, it is very difficult to isolate only the oceanic influence upon the atmosphere. The SST in this cold spot is, however, dominated by the tidal mixing, which is independent of the atmospheric processes. This unique condition may ease the account for the oceanic influence only. Although the SST environment of the Okhotsk Sea is good for understanding the oceanic influence upon the atmosphere, only a few studies has been executed in this region because of the difficulty of observations by research vessels in this region, where territory problems between Japan and Russia is unsolved. Because of the scant of direct observation, the Okhotsk Sea was still mysterious. In 2006 August, GPS radiosonde observation was carried out by Russian research vessel Khromov in the Sea of Okhotsk by the cooperation between Japan and Russia, and strong SST gradient of about 7 Celsius degrees/10km was observed around the Kuril Islands. The purpose of this study is to demonstrate observational finding of meso-scale atmospheric anticyclonic circulation influenced by the cold oceanic spot around the Kuril Island. The summaries of the observation are as follows. Meso-scale atmospheric ageostrophic anticyclonic circulation in the atmospheric marine-boundary layer is observed in and around the cold spot. A high air pressure area as compared with other surrounding areas is also located at the

  6. A two-tier atmospheric circulation classification scheme for the European-North Atlantic region

    Science.gov (United States)

    Guentchev, Galina S.; Winkler, Julie A.

    A two-tier classification of large-scale atmospheric circulation was developed for the European-North-Atlantic domain. The classification was constructed using a combination of principal components and k-means cluster analysis applied to reanalysis fields of mean sea-level pressure for 1951-2004. Separate classifications were developed for the winter, spring, summer, and fall seasons. For each season, the two classification tiers were identified independently, such that the definition of one tier does not depend on the other tier having already been defined. The first tier of the classification is comprised of supertype patterns. These broad-scale circulation classes are useful for generalized analyses such as investigations of the temporal trends in circulation frequency and persistence. The second, more detailed tier consists of circulation types and is useful for numerous applied research questions regarding the relationships between large-scale circulation and local and regional climate. Three to five supertypes and up to 19 circulation types were identified for each season. An intuitive nomenclature scheme based on the physical entities (i.e., anomaly centers) which dominate the specific patterns was used to label each of the supertypes and types. Two example applications illustrate the potential usefulness of a two-tier classification. In the first application, the temporal variability of the supertypes was evaluated. In general, the frequency and persistence of supertypes dominated by anticyclonic circulation increased during the study period, whereas the supertypes dominated by cyclonic features decreased in frequency and persistence. The usefulness of the derived circulation types was exemplified by an analysis of the circulation associated with heat waves and cold spells reported at several cities in Bulgaria. These extreme temperature events were found to occur with a small number of circulation types, a finding that can be helpful in understanding past

  7. Explanatory analysis of the relationship between atmospheric circulation and occurrence of flood generating events in a coastal city

    DEFF Research Database (Denmark)

    Åström, Helena Lisa Alexandra; Sunyer Pinya, Maria Antonia; Madsen, H.;

    2016-01-01

    , respectively. To describe the atmospheric circulation we used the Lamb circulation type (LCT) classification and re-grouped it into Lamb circulation classes (LCC). The daily LCCs/LCTs were connected with rare precipitation and water level events in Aarhus, a Danish coastal city. Westerly and cyclonic LCCs (W...

  8. Cloud-radiative effects on implied oceanic energy transport as simulated by atmospheric general circulation models

    Science.gov (United States)

    Gleckler, P. J.; Randall, D. A.; Boer, G.; Colman, R.; Dix, M.; Galin, V.; Helfand, M.; Kiehl, J.; Kitoh, A.; Lau, W.

    1995-01-01

    This paper summarizes the ocean surface net energy flux simulated by fifteen atmospheric general circulation models constrained by realistically-varying sea surface temperatures and sea ice as part of the Atmospheric Model Intercomparison Project. In general, the simulated energy fluxes are within the very large observational uncertainties. However, the annual mean oceanic meridional heat transport that would be required to balance the simulated surface fluxes is shown to be critically sensitive to the radiative effects of clouds, to the extent that even the sign of the Southern Hemisphere ocean heat transport can be affected by the errors in simulated cloud-radiation interactions. It is suggested that improved treatment of cloud radiative effects should help in the development of coupled atmosphere-ocean general circulation models.

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

    CERN Document Server

    Shirley, James H

    2016-01-01

    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 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. The 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 the hypothesis may be tested through numerical modeling. Examples from investigations of the atmospheric circulation of Mars are provided to illustrate quali...

  10. Impact of oceanic circulation changes on atmospheric δ13CO2

    Science.gov (United States)

    Menviel, L.; Mouchet, A.; Meissner, K. J.; Joos, F.; England, M. H.

    2015-12-01

    δ13CO2 measured in Antarctic ice cores provides constraints on oceanic and terrestrial carbon cycle processes linked with millennial-scale and glacial/interglacial changes in atmospheric CO2. However, the interpretation of δ13CO2 is not straightforward. Using two Earth system models of intermediate complexity we perform a set of sensitivity experiments in which the formation rates of North Atlantic Deep Water (NADW), North Pacific Deep Water (NPDW), Antarctic Bottom Water (AABW) and Antarctic Intermediate Water (AAIW) are varied. We study the impact of these circulation changes on atmospheric δ13CO2 as well as on the oceanic δ13C distribution. In general, we find that the formation rates of AABW, NADW, NPDW and AAIW are negatively correlated with changes in δ13CO2: namely strong oceanic ventilation decreases atmospheric δ13CO2. However, since large scale ocean circulation reorganizations also impact nutrient utilization and the Earth's climate the relationship between atmospheric δ13CO2 levels and ocean ventilation rate is not unequivocal. In both models atmospheric δ13CO2 is very sensitive to changes in AABW formation rates: increased AABW formation enhances the upwelling of low δ13C waters to the surface and decreases atmospheric δ13CO2. By contrast, the impact of NADW changes on atmospheric δ13CO2 is less robust and might be model dependent.

  11. Temperature Structure and Atmospheric Circulation of Dry Tidally Locked Rocky Exoplanets

    Science.gov (United States)

    Koll, Daniel D. B.; Abbot, Dorian S.

    2016-07-01

    Next-generation space telescopes will observe the atmospheres of rocky planets orbiting nearby M-dwarfs. Understanding these observations will require well-developed theory in addition to numerical simulations. Here we present theoretical models for the temperature structure and atmospheric circulation of dry, tidally locked rocky exoplanets with gray radiative transfer and test them using a general circulation model (GCM). First, we develop a radiative-convective (RC) model that captures surface temperatures of slowly rotating and cool atmospheres. Second, we show that the atmospheric circulation acts as a global heat engine, which places strong constraints on large-scale wind speeds. Third, we develop an RC-subsiding model which extends our RC model to hot and thin atmospheres. We find that rocky planets develop large day-night temperature gradients at a ratio of wave-to-radiative timescales up to two orders of magnitude smaller than the value suggested by work on hot Jupiters. The small ratio is due to the heat engine inefficiency and asymmetry between updrafts and subsidence in convecting atmospheres. Fourth, we show, using GCM simulations, that rotation only has a strong effect on temperature structure if the atmosphere is hot or thin. Our models let us map out atmospheric scenarios for planets such as GJ 1132b, and show how thermal phase curves could constrain them. Measuring phase curves of short-period planets will require similar amounts of time on the James Webb Space Telescope as detecting molecules via transit spectroscopy, so future observations should pursue both techniques.

  12. Future changes in atmospheric circulation types and related precipitation extremes in Central Europe

    Science.gov (United States)

    Homann, Markus; Jacobeit, Jucundus; Beck, Christoph; Philipp, Andreas

    2016-04-01

    The statistical evaluation of the relationships between atmospheric circulation types and areal precipitation events took place in the context of an international project called WETRAX (Weather patterns, storm tracks and related precipitation extremes). The aim of the project was to estimate the regional flooding potential in Central Europe under enhanced climate change conditions. For parts of southern Central Europe, a gridded daily precipitation set with 6km horizontal resolution has been generated for the period 1951-2006 by the Austrian Zentralanstalt für Meteorologie und Geodynamik (ZAMG). To determine regions with similar precipitation variability, a S-mode principal component analysis has been applied. Extreme precipitation events are defined by the 95% percentile, based on regional arithmetic means of daily precipitation. Large-scale atmospheric circulation types have been derived by different statistical methods and variables using the COST733 classification software and gridded daily NCEP1 reanalysis data. To evaluate the performance of a particular circulation type classification with respect to regional precipitation extremes, multiple regression models have been derived between the circulation type frequencies as predictor variables and monthly frequencies of extreme precipitation as well as monthly rainfall amounts from these events. To estimate the regional flooding potential in Central Europe under enhanced climate change conditions, multiple regression models are applied to different projected GCM predictor data. Thus, future changes in circulation type occurrence frequencies are transferred into assessments of future changes in precipitation extremes on a regional scale.

  13. The impact of regional Arctic sea ice loss on atmospheric circulation and the NAO

    Science.gov (United States)

    Anker Pedersen, Rasmus; Cvijanovic, Ivana; Langen, Peter Lang; Vinther, Bo

    2016-04-01

    Reduction of the Arctic sea ice cover can affect the atmospheric circulation, and thus impact the climate beyond the Arctic. The atmospheric response may, however, vary with the geographical location of sea ice loss. The atmospheric sensitivity to the location of sea ice loss is studied using a general circulation model in a configuration that allows combination of a prescribed sea ice cover and an active mixed layer ocean. This hybrid setup makes it possible to simulate the isolated impact of sea ice loss and provides a more complete response compared to experiments with fixed sea surface temperatures. Three investigated sea ice scenarios with ice loss in different regions all exhibit substantial near-surface warming which peaks over the area of ice loss. The maximum warming is found during winter, delayed compared to the maximum sea ice reduction. The wintertime response of the mid-latitude atmospheric circulation shows a non-uniform sensitivity to the location of sea ice reduction. While all three scenarios exhibit decreased zonal winds related to high-latitude geopotential height increases, the magnitudes and locations of the anomalies vary between the simulations. Investigation of the North Atlantic Oscillation reveals a high sensitivity to the location of the ice loss. The northern center of action exhibits clear shifts in response to the different sea ice reductions. Sea ice loss in the Atlantic and Pacific sectors of the Arctic cause westward and eastward shifts, respectively.

  14. North Atlantic thermohaline circulation predictability in a coupled ocean-atmosphere model

    CERN Document Server

    Griffies, S M; Griffies, Stephen M.; Bryan, Kirk

    1995-01-01

    Predictability of the North Atlantic thermohaline circulation (THC) variability as simulated in the GFDL coupled ocean-atmosphere general circulation model is established for a set of ensemble experiments. The ensembles consist of identical oceanic initial conditions underneath a model atmosphere chosen randomly from the model climatology. This experimental design is based on the separation in time scales present in the model which motivates the assumption that the predictability deduced from these ensembles provides an upper limit to the model's THC predictability. The climatology is taken from a multi-century model integration whose THC variability has power concentrated at the 40-60 year time scale. A linear stochastic perspective is shown to be generally consistent with the ensemble statistics. The linear theory suggests a natural measure of ensemble predictability as the time at which the ensemble variance becomes a subjectively defined fraction (0.5 used here) of the climatological variance. It is furth...

  15. Debris flows in the Eastern Italian Alps: seasonality and atmospheric circulation patterns

    Directory of Open Access Journals (Sweden)

    E. I. Nikolopoulos

    2014-12-01

    Full Text Available The work examines the seasonality and large-scale atmospheric circulation patterns of debris flows in the Trentino-Alto Adige region (Eastern Italian Alps. Analysis is based on classification algorithms applied on 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 account for 92% of the debris flows in the record, while atmospheric circulation characterized by Zonal West, Mixed and Meridional South, Southeast patterns account for 80%. Both seasonal and circulation patterns exhibit geographical preference. In the case of seasonality, there is a strong north–south separation of summer–fall dominance while spatial distribution of dominant circulation patterns exhibits clustering, with both Zonal West and Mixed prevailing in the northwest and central east part of the region, while the southern part relates to Meridional South, Southeast pattern. Seasonal and synoptic pattern dependence is pronounced also on the debris flow triggering rainfall properties. Examination of rainfall intensity–duration thresholds derived for different data classes (according to season and synoptic pattern revealed a distinct variability in estimated thresholds. These findings imply a certain control on debris-flow events and can therefore be used to improve existing alert systems.

  16. A statistical assessment of tropical cyclone activity in atmospheric general circulation models

    OpenAIRE

    Suzana J. Camargo; Barnston, Anthony G; Zebiak, Stephen E.

    2005-01-01

    The properties of tropical cyclones in three low-resolution atmospheric general circulation models (AGCMs) in seven ocean basins are discussed. The models are forced by prescribed, observed sea surface temperatures over a period of 40 yr, and their simulations of tropical cyclone activity are compared with observations. The model cyclone characteristics considered include genesis position, number of cyclones per year, seasonality, accumulated cyclone energy, track locations, and number of sto...

  17. 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

  18. Long-term air temperature variation in the Karkonosze mountains according to atmospheric circulation

    Science.gov (United States)

    Migała, Krzysztof; Urban, Grzegorz; Tomczyński, Karol

    2016-07-01

    The results of meteorological measurements carried out continuously on Mt Śnieżka in Karkonosze mountains since 1880 well document the warming observed on a global scale. Data analysis indicates warming expressed by an increase in the mean annual air temperature of 0.8 °C/100 years. A much higher temperature increase was recorded in the last two decades at the turn of the twenty-first century. Mean decade air temperatures increased from -0.1 to 1.5 °C. It has been shown that there are relationships between air temperature at Mt Śnieżka and global mechanisms of atmospheric and oceanic circulation. Thermal conditions of the Karkonosze (Mt Śnieżka) accurately reflect global climate trends and impact of the North Atlantic Oscillation (NAO) index, macrotypes of atmospheric circulation in Europe (GWL) and Atlantic Multidecadal Oscillation (AMO). The increase in air temperature during the 1989-2012 solar magnetic cycle may reveal a synergy effect to which astrophysical effects and atmospheric and oceanic circulation effects contribute, modified by constantly increasing anthropogenic factors.

  19. Atmospheric circulation of eccentric hot Jupiter HAT-P-2B

    Energy Technology Data Exchange (ETDEWEB)

    Lewis, Nikole K. [Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Showman, Adam P. [Department of Planetary Sciences and Lunar and Planetary Laboratory, The University of Arizona, Tucson, AZ 85721 (United States); Fortney, Jonathan J. [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Knutson, Heather A. [Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125 (United States); Marley, Mark S., E-mail: nklewis@mit.edu [NASA Ames Research Center 245-3, Moffett Field, CA 94035 (United States)

    2014-11-10

    The hot Jupiter HAT-P-2b has become a prime target for Spitzer Space Telescope observations aimed at understanding the atmospheric response of exoplanets on highly eccentric orbits. Here we present a suite of three-dimensional atmospheric circulation models for HAT-P-2b that investigate the effects of assumed atmospheric composition and rotation rate on global scale winds and thermal patterns. We compare and contrast atmospheric models for HAT-P-2b, which assume one and five times solar metallicity, both with and without TiO/VO as atmospheric constituents. Additionally we compare models that assume a rotation period of half, one, and two times the nominal pseudo-synchronous rotation period. We find that changes in assumed atmospheric metallicity and rotation rate do not significantly affect model predictions of the planetary flux as a function of orbital phase. However, models in which TiO/VO are present in the atmosphere develop a transient temperature inversion between the transit and secondary eclipse events that results in significant variations in the timing and magnitude of the peak of the planetary flux compared with models in which TiO/VO are omitted from the opacity tables. We find that no one single atmospheric model can reproduce the recently observed full orbit phase curves at 3.6, 4.5 and 8.0 μm, which is likely due to a chemical process not captured by our current atmospheric models for HAT-P-2b. Further modeling and observational efforts focused on understanding the chemistry of HAT-P-2b's atmosphere are needed and could provide key insights into the interplay between radiative, dynamical, and chemical processes in a wide range of exoplanet atmospheres.

  20. Atmospheric Circulation of Eccentric Hot Jupiter HAT-P-2b

    CERN Document Server

    Lewis, Nikole K; Fortney, Jonathan J; Knutson, Heather A; Marley, Mark S

    2014-01-01

    The hot-Jupiter HAT-P-2b has become a prime target for Spitzer Space Telescope observations aimed at understanding the atmospheric response of exoplanets on highly eccentric orbits. Here we present a suite of three-dimensional atmospheric circulation models for HAT-P-2b that investigate the effects of assumed atmospheric composition and rotation rate on global scale winds and thermal patterns. We compare and contrast atmospheric models for HAT-P-2b, which assume one and five times solar metallicity, both with and without TiO/VO as atmospheric constituents. Additionally we compare models that assume a rotation period of half, one, and two times the nominal pseudo-synchronous rotation period. We find that changes in assumed atmospheric metallicity and rotation rate do not significantly affect model predictions of the planetary flux as a function of orbital phase. However, models in which TiO/VO are present in the atmosphere develop a transient temperature inversion between the transit and secondary eclipse even...

  1. The Energetic Constraints on the Zonal Mean Atmospheric Circulations in the Tropics, Midlatitudes, and High Latitudes

    Science.gov (United States)

    Hwang, Yen-Ting

    In this doctoral thesis, I have studied the processes that affect the atmospheric energy budget and their coupling relationships with atmospheric circulations. The equator-to-pole radiation gradient at the top of the atmosphere is the fundamental driver of atmospheric and oceanic circulations. Any anomaly in the energy budget due to variations in different climate components (such as clouds, aerosols, atmospheric properties, and land surfaces) will have an effect on the atmospheric and oceanic circulations and energy transport. Variations in the energy budget of extratropical regions have a non-local effect on tropical climate and vice versa. We first investigated climate components that affect the atmospheric energy budget and their coupled relationships with the atmospheric energy transport, using CMIP multi-model ensembles. We studied how individual components affect energy transport in three latitude bands: (1) at 70 degrees, where increasing poleward energy transport may cause polar amplification, (2) at 40 degrees, where eddies are the strongest, and (3) in the deep tropics, where global climate models (GCMs) do not agree on the changes in transport in global warming scenarios. In high latitudes, positive radiative effects from melting sea ice decrease the equator-to-pole temperature gradient and prevent poleward fluxes from increasing. Models that have more melting ice tend to predict a smaller increase in the energy transport, which is counterintuitive based on the argument that increasing poleward transport can lead to melting sea ice. The cooling effect of increasing low clouds over newly open ocean along the ice edge sharpens the temperature gradient and increases the energy transport in midlatitudes. Clouds and sea ice in the extratropics can also influence energy transport at the equator. We then shifted our focus to the tropical rain belt, built on the first part that demonstrated a directly linkage from hemispheric asymmetry of the atmospheric energy

  2. 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.)

  3. Atmospheric circulation of brown dwarfs and directly imaged extrasolar giant planets with active clouds

    Science.gov (United States)

    Tan, Xianyu; Showman, Adam

    2016-10-01

    Observational evidence have suggested active meteorology in the atmospheres of brown dwarfs (BDs) and directly imaged extrasolar giant planets (EGPs). In particular, a number of surveys for brown dwarfs showed that near-IR brightness variability is common for L and T dwarfs. Directly imaged EGPs share similar observations, and can be viewed as low-gravity versions of BDs. Clouds are believed to play the major role in shaping the thermal structure, dynamics and near-IR flux of these atmospheres. So far, only a few studies have been devoted to atmospheric circulation and the implications for observations of BDs and directly EGPs, and yet no global model includes a self-consistent active cloud formation. Here we present preliminary results from the first global circulation model applied to BDs and directly imaged EGPs that can properly treat absorption and scattering of radiation by cloud particles. Our results suggest that horizontal temperature differences on isobars can reach up to a few hundred Kelvins, with typical horizontal length scale of the temperature and cloud patterns much smaller than the radius of the object. The combination of temperature anomaly and cloud pattern can result in moderate disk-integrated near-IR flux variability. Wind speeds can reach several hundred meters per second in cloud forming layers. Unlike Jupiter and Saturn, we do not observe stable zonal jet/banded patterns in our simulations. Instead, our simulated atmospheres are typically turbulent and dominated by transient vortices. The circulation is sensitive to the parameterized cloud microphysics. Under some parameter combinations, global-scale atmospheric waves can be triggered and maintained. These waves induce global-scale temperature anomalies and cloud patterns, causing large (up to several percent) disk-integrated near-IR flux variability. Our results demonstrate that the commonly observed near-IR brightness variability for BDs and directly imaged EGPs can be explained by the

  4. Primary Reasoning behind the Double ITCZ Phenomenon in a Coupled Ocean-Atmosphere General Circulation Model

    Institute of Scientific and Technical Information of China (English)

    李江龙; 张学洪; 俞永强; 戴福山

    2004-01-01

    This paper investigates the processes behind the double ITCZ phenomenon, a common problem in Coupled ocean-atmosphere General Circulation Models (CGCMs), using a CGCM-FGCM-0 (Flexible General Circulation Model, version 0). The double ITCZ mode develops rapidly during the first two years of the integration and becomes a perennial phenomenon afterwards in the model. By way of Singular Value Decomposition (SVD) for SST, sea surface pressure, and sea surface wind, some air-sea interactions are analyzed. These interactions prompt the anomalous signals that appear at the beginning of the coupling to develop rapidly. There are two possible reasons, proved by sensitivity experiments: (1) the overestimated east-west gradient of SST in the equatorial Pacific in the ocean spin-up process, and (2) the underestimated amount of low-level stratus over the Peruvian coast in CCM3 (the Community Climate Model, Version Three). The overestimated east-west gradient of SST brings the anomalous equatorial easterly. The anomalous easterly, affected by the Coriolis force in the Southern Hemisphere, turns into an anomalous westerly in a broad area south of the equator and is enhanced by atmospheric anomalous circulation due to the underestimated amount of low-level stratus over the Peruvian coast simulated by CCM3. The anomalous westerly leads to anomalous warm advection that makes the SST warm in the southeast Pacific.The double ITCZ phenomenon in the CGCM is a result of a series of nonlocal and nonlinear adjustment processes in the coupled system, which can be traced to the uncoupled models, oceanic component, and atmospheric component. The zonal gradient of the equatorial SST is too large in the ocean component and the amount of low-level stratus over the Peruvian coast is too low in the atmosphere component.

  5. Atmospheric circulation processes contributing to a multidecadal variation in reconstructed and modeled Indian monsoon precipitation

    Science.gov (United States)

    Wu, Qianru; Hu, Qi

    2015-01-01

    analysis of the recently reconstructed gridded May-September total precipitation in the Indian monsoon region for the past half millennium discloses significant variations at multidecadal timescales. Meanwhile, paleo-climate modeling outputs from the National Center for Atmospheric Research Community Climate System Model 4.0 show similar multidecadal variations in the monsoon precipitation. One of those variations at the frequency of 40-50 years per cycle is examined in this study. Major results show that this variation is a product of the processes in that the meridional gradient of the atmospheric enthalpy is strengthened by radiation loss in the high-latitude and polar region. Driven by this gradient and associated baroclinicity in the atmosphere, more heat/energy is generated in the tropical and subtropical (monsoon) region and transported poleward. This transport relaxes the meridional enthalpy gradient and, subsequently, the need for heat production in the monsoon region. The multidecadal timescale of these processes results from atmospheric circulation-radiation interactions and the inefficiency in generation of kinetic energy from the potential energy in the atmosphere to drive the eddies that transport heat poleward. This inefficiency creates a time delay between the meridional gradient of the enthalpy and the poleward transport. The monsoon precipitation variation lags that in the meridional gradient of enthalpy but leads that of the poleward heat transport. This phase relationship, and underlining chasing process by the transport of heat to the need for it driven by the meridional enthalpy gradient, sustains this multidecadal variation. This mechanism suggests that atmospheric circulation processes can contribute to multidecadal timescale variations. Interactions of these processes with other forcing, such as sea surface temperature or solar irradiance anomalies, can result in resonant or suppressed variations in the Indian monsoon precipitation.

  6. The switching between zonal and blocked mid-latitude atmospheric circulation: a dynamical system perspective

    Science.gov (United States)

    Faranda, Davide; Masato, Giacomo; Moloney, Nicholas; Sato, Yuzuru; Daviaud, Francois; Dubrulle, Bérengère; Yiou, Pascal

    2016-09-01

    Atmospheric mid-latitude circulation is dominated by a zonal, westerly flow. Such a flow is generally symmetric, but it can be occasionally broken up by blocking anticyclones. The subsequent asymmetric flow can persist for several days. In this paper, we apply new mathematical tools based on the computation of an extremal index in order to reexamine the dynamical mechanisms responsible for the transitions between zonal and blocked flows. We discard the claim that mid-latitude circulation features two distinct stable equilibria or chaotic regimes, in favor of a simpler mechanism that is well understood in dynamical systems theory: we identify the blocked flow as an unstable fixed point (or saddle point) of a single basin chaotic attractor, dominated by the westerlies regime. We also analyze the North Atlantic Oscillation and the Arctic Oscillation atmospheric indices, whose behavior is often associated with the transition between the two circulation regimes, and investigate analogies and differences with the bidimensional blocking indices. We find that the Arctic Oscillation index, which can be thought as a proxy for a hemispheric average of the Tibaldi-Molteni blocking index, tracks unstable fixed points. On the other hand, the North Atlantic Oscillation, representative only for local properties of the North Atlantic blocking dynamics, does not show any trace of the presence of unstable fixed points of the dynamics.

  7. Climate change on the Tibetan Plateau in response to shifting atmospheric circulation since the LGM

    Science.gov (United States)

    Zhu, Liping; Lü, Xinmiao; Wang, Junbo; Peng, Ping; Kasper, Thomas; Daut, Gerhard; Haberzettl, Torsten; Frenzel, Peter; Li, Quan; Yang, Ruimin; Schwalb, Antje; Mäusbacher, Roland

    2015-01-01

    The Tibetan Plateau (TP) is primarily influenced by the northern hemispheric middle latitude Westerlies and the Indian summer monsoon (ISM). The extent, long-distance effects and potential long-term changes of these two atmospheric circulations are not yet fully understood. Here, we analyse modern airborne pollen in a transition zone of seasonally alternating dominance of the Westerlies and the ISM to develop a pollen discrimination index (PDI) that allows us to distinguish between the intensities of the two circulation systems. This index is applied to interpret a continuous lacustrine sedimentary record from Lake Nam Co covering the past 24 cal kyr BP to investigate long-term variations in the atmospheric circulation systems. Climatic variations on the central TP widely correspond to those of the North Atlantic (NA) realm, but are controlled through different mechanisms resulting from the changing climatic conditions since the Last Glacial Maximum (LGM). During the LGM, until 16.5 cal kyr BP, the TP was dominated by the Westerlies. After 16.5 cal kyr BP, the climatic conditions were mainly controlled by the ISM. From 11.6 to 9 cal kyr BP, the TP was exposed to enhanced solar radiation at the low latitudes, resulting in greater water availability. PMID:26294226

  8. 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.

  9. Influence of atmospheric circulation patterns on local cloud and solar variability in Bergen, Norway

    Science.gov (United States)

    Parding, Kajsa; Olseth, Jan Asle; Liepert, Beate G.; Dagestad, Knut-Frode

    2016-08-01

    In a previous paper, we have shown that long-term cloud and solar observations (1965-2013) in Bergen, Norway (60.39°N, 5.33°E) are compatible with a largely cloud dominated radiative climate. Here, we explicitly address the relationship between the large scale circulation over Europe and local conditions in Bergen, identifying specific circulation shifts that have contributed to the observed cloud and solar variations. As a measure of synoptic weather patterns, we use the Grosswetterlagen (GWL), a daily classification of European weather for 1881-2013. Empirical models of cloud cover, cloud base, relative sunshine duration, and normalised global irradiance are constructed based on the GWL frequencies, extending the observational time series by more than 70 years. The GWL models successfully reproduce the observed increase in cloud cover and decrease in solar irradiance during the 1970s and 1980s. This cloud-induced dimming is traced to an increasing frequency of cyclonic and decreasing frequency of anticyclonic weather patterns over northern Europe. The changing circulation patterns in winter can be understood as a shift from the negative to the positive phase of the North Atlantic and Arctic Oscillation. A recent period of increasing solar irradiance is observed but not reproduce by the GWL models, suggesting this brightening is associated with factors other than large scale atmospheric circulation, possibly decreasing aerosol loads and local cloud shifts.

  10. THOR: A New and Flexible Global Circulation Model to Explore Planetary Atmospheres

    CERN Document Server

    Mendonça, João M; Grosheintz, Luc; Heng, Kevin

    2016-01-01

    We have designed and developed, from scratch, a global circulation model named THOR that solves the three-dimensional non-hydrostatic Euler equations. Our general approach lifts the commonly used assumptions of a shallow atmosphere and hydrostatic equilibrium. We solve the "pole problem" (where converging meridians on a sphere lead to increasingly smaller time steps near the poles) by implementing an icosahedral grid. Irregularities in the grid, which lead to grid imprinting, are smoothed using the "spring dynamics" technique. We validate our implementation of spring dynamics by examining calculations of the divergence and gradient of test functions. To prevent the computational time step from being bottlenecked by having to resolve sound waves, we implement a split-explicit method together with a horizontally explicit and vertically implicit integration. We validate our global circulation model by reproducing the Earth and also the hot Jupiter-like benchmark tests. THOR was designed to run on Graphics Proces...

  11. 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.

  12. Radiation and atmospheric circulation controls on carbonyl sulfide concentrations in the marine boundary layer

    Science.gov (United States)

    Berkelhammer, M.; Steen-Larsen, H. C.; Cosgrove, A.; Peters, A. J.; Johnson, R.; Hayden, M.; Montzka, S. A.

    2016-11-01

    A potential closure of the global carbonyl sulfide (COS or OCS) budget has recently been attained through a combination of remote sensing, modeling, and extended surface measurements. However, significant uncertainties in the spatial and temporal dynamics of the marine flux still persist. In order to isolate the terrestrial photosynthetic component of the global atmospheric OCS budget, tighter constraints on the marine flux are needed. We present 6 months of nearly continuous in situ OCS concentrations from the North Atlantic during the fall and winter of 2014-2015 using a combination of research vessel and fixed tower measurements. The data are characterized by synoptic-scale ˜100 pmol mol-1 variations in marine boundary layer air during transitions from subtropical to midlatitude source regions. The synoptic OCS variability is shown here to be a linear function of the radiation history along an air parcel's trajectory with no apparent sensitivity to the chlorophyll concentration of the surface waters that the air mass interacted with. This latter observation contradicts expectations and suggests a simple radiation limitation for the combined direct and indirect marine OCS emissions. Because the concentration of OCS in the marine boundary layer is so strongly influenced by an air parcel's history, marine and atmospheric concentrations would rarely be near equilibrium and thus even if marine production rates are held constant at a given location, the ocean-atmosphere flux would be sensitive to changes in atmospheric circulation alone. We hypothesize that changes in atmospheric circulation including latitudinal shifts in the storm tracks could affect the marine flux through this effect.

  13. 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

  14. Resilience of the Asian atmospheric circulation to paleogeographic and climatic changes

    Science.gov (United States)

    Licht, Alexis; Dupont-Nivet, Guillaume; Pullen, Alex; Kapp, Paul; Abels, Hemmo; Abell, Jordan; Giesler, Dominique

    2016-04-01

    At the southwestern margin of the Chinese Loess Plateau in the Xining Basin, Eocene-Oligocene red mudstones have been interpreted as isolated remnants of dust deposits based on grain-size distribution and quartz grain morphology. These deposits have not received the focus that the Plio-Quaternary Loess Plateau strata have received though they could provide an opportunity to document late Paleogene regional atmospheric circulation and the early mechanisms of central Asian aridification. Here, we used single-grain U-Pb dating of multiple detrital zircons to constrain their provenance. Red mudstone strata yield statistically different age distributions when compared to coeval fluvial sandstones from the Xining Basin, thus corroborating distal aeolian transport. Comparison with Paleogene regional age distributions indicates that provenance of the red mudstones is well-explained by a combination of surface westerly, dust-generating winds blowing along the northern margin of the Tibetan Plateau and recycling of locally-sourced fluvial sediment. We thus propose that dust accumulation in central China has been occurring during most of the Cenozoic but that Paleogene deposits are rare because of long-term deflation and recycling into younger terrestrial loess deposits and into the Northern Pacific Ocean. The inferred Paleogene arid surface conditions along the northern margin of the Tibetan Plateau, despite the presence of an extended seaway in central Asia -the Tarim Sea, suggest the presence of a strong subtropical high in central China. Evidence of orbitally-controlled lacustrine phases inter-fingered within the red mudstones indicates regular weakening or shifting of this subtropical high and mirrors the Plio-Quaternary monsoonal atmospheric circulation dynamics in central Asia. These findings thus indicate that synoptic-level atmospheric circulation over central Asia has changed little since middle Eocene time and suggest that the retreat of the Tarim Sea and the

  15. Southwestern Tropical Atlantic coral growth response to atmospheric circulation changes induced by ozone depletion in Antarctica

    Directory of Open Access Journals (Sweden)

    H. Evangelista

    2015-08-01

    Full Text Available Climate changes induced by stratospheric ozone depletion over Antarctica have been recognized as an important consequence of the recently observed Southern Hemisphere atmospheric circulation. Here we present evidences that the Brazilian coast (Southwestern Atlantic may have been impacted from both winds and sea surface temperature changes derived from this process. Skeleton analysis of massive coral species living in shallow waters off Brazil are very sensitive to air–sea interactions, and seem to record this impact. Growth rates of Brazilian corals show a trend reversal that fits the ozone depletion evolution, confirming that ozone impacts are far reaching and potentially affect coastal ecosystems in tropical environments.

  16. Intercomparison and interpretation of surface energy fluxes in atmospheric general circulation models

    Science.gov (United States)

    Randall, D. A.; Cess, R. D.; Blanchet, J. P.; Boer, G. J.; Dazlich, D. A.; Del Genio, A. D.; Deque, M.; Dymnikov, V.; Galin, V.; Ghan, S. J.

    1992-01-01

    Responses of the surface energy budgets and hydrologic cycles of 19 atmospheric general circulation models to an imposed, globally uniform sea surface temperature perturbation of 4 K were analyzed. The responses of the simulated surface energy budgets are extremely diverse and are closely linked to the responses of the simulated hydrologic cycles. The response of the net surface energy flux is not controlled by cloud effects; instead, it is determined primarily by the response of the latent heat flux. The prescribed warming of the oceans leads to major increases in the atmospheric water vapor content and the rates of evaporation and precipitation. The increased water vapor amount drastically increases the downwelling IR radiation at the earth's surface, but the amount of the change varies dramatically from one model to another.

  17. Design and Performance Analysis of a Massively Parallel Atmospheric General Circulation Model

    Directory of Open Access Journals (Sweden)

    Daniel S. Schaffer

    2000-01-01

    Full Text Available In the 1990's, computer manufacturers are increasingly turning to the development of parallel processor machines to meet the high performance needs of their customers. Simultaneously, atmospheric scientists studying weather and climate phenomena ranging from hurricanes to El Niño to global warming require increasingly fine resolution models. Here, implementation of a parallel atmospheric general circulation model (GCM which exploits the power of massively parallel machines is described. Using the horizontal data domain decomposition methodology, this FORTRAN 90 model is able to integrate a 0.6° longitude by 0.5° latitude problem at a rate of 19 Gigaflops on 512 processors of a Cray T3E 600; corresponding to 280 seconds of wall-clock time per simulated model day. At this resolution, the model has 64 times as many degrees of freedom and performs 400 times as many floating point operations per simulated day as the model it replaces.

  18. A Review of Water Isotopes in Atmospheric General Circulation Models: Recent Advances and Future Prospects

    Directory of Open Access Journals (Sweden)

    Xi Xi

    2014-01-01

    Full Text Available Stable water isotopologues, mainly 1H2O, 1H2HO (HDO, and H12O18, are useful tracers for processes in the global hydrological cycle. The incorporation of water isotopes into Atmospheric General Circulation Models (AGCMs since 1984 has helped scientists gain substantial new insights into our present and past climate. In recent years, there have been several significant advances in water isotopes modeling in AGCMs. This paper reviews and synthesizes key advances accomplished in modeling (1 surface evaporation, (2 condensation, (3 supersaturation, (4 postcondensation processes, (5 vertical distribution of water isotopes, and (6 spatial δ18O-temperature slope and utilizing (1 spectral nudging technique, (2 higher model resolutions, and (3 coupled atmosphere-ocean models. It also reviews model validation through comparisons of model outputs and ground-based and spaceborne measurements. In the end, it identifies knowledge gaps and discusses future prospects of modeling and model validation.

  19. Atmospheric circulation of tidally locked exoplanets II: dual-band radiative transfer and convective adjustment

    CERN Document Server

    Heng, Kevin; Phillipps, Peter J

    2011-01-01

    Improving upon our purely dynamical work, we present three-dimensional simulations of the atmospheric circulation on Earth-like (exo)planets and hot Jupiters using the GFDL-Princeton Flexible Modeling System (FMS). As the first steps away from the purely dynamical benchmarks of Heng, Menou & Phillipps (2011), we add dual-band radiative transfer and dry convective adjustment schemes to our computational setup. Our treatment of radiative transfer assumes stellar irradiation to peak at a wavelength shorter than and distinct from that at which the exoplanet re-emits radiation ("shortwave" versus "longwave"), and also uses a two-stream approximation. Convection is mimicked by adjusting unstable lapse rates to the dry adiabat. The bottom of the atmosphere is bounded by an uniform slab with a finite thermal inertia. For our hot Jupiter models, we include an analytical formalism for calculating temperature-pressure profiles, in radiative equilibrium, which accounts for the effect of collision-induced absorption v...

  20. The Impact of Oceanic Heat Transport on the Atmospheric Circulation: a Thermodynamic Perspective

    CERN Document Server

    Schröder, Alexander; Lunkeit, Frank

    2014-01-01

    The present study investigates how global thermodynamic properties of the climate system are affected by the changes in the intensity of the imposed oceanic heat transport in an atmospheric general circulation model in aqua-planet configuration. Increasing the poleward oceanic heat transport results in an overall increase in the surface temperature and a decrease in the equator-to-pole surface temperature difference as a result of the ice-albedo feedback. Following the classical ansatz by Stone, the atmospheric heat transport changes in such a way that the total poleward heat transport remains almost unchanged. We also find that 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 which 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 fl...

  1. The water cycle in the general circulation model of the martian atmosphere

    Science.gov (United States)

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

    2016-03-01

    Within the numerical general-circulation model of the Martian atmosphere MAOAM (Martian Atmosphere: Observation and Modeling), we have developed the water cycle block, which is an essential component of modern general circulation models of the Martian atmosphere. The MAOAM model has a spectral dynamic core and successfully predicts the temperature regime on Mars through the use of physical parameterizations typical of both terrestrial and Martian models. We have achieved stable computation for three Martian years, while maintaining a conservative advection scheme taking into account the water-ice phase transitions, water exchange between the atmosphere and surface, and corrections for the vertical velocities of ice particles due to sedimentation. The studies show a strong dependence of the amount of water that is actively involved in the water cycle on the initial data, model temperatures, and the mechanism of water exchange between the atmosphere and the surface. The general pattern and seasonal asymmetry of the water cycle depends on the size of ice particles, the albedo, and the thermal inertia of the planet's surface. One of the modeling tasks, which results from a comparison of the model data with those of the TES experiment on board Mars Global Surveyor, is the increase in the total mass of water vapor in the model in the aphelion season and decrease in the mass of water ice clouds at the poles. The surface evaporation scheme, which takes into account the turbulent rise of water vapor, on the one hand, leads to the most complete evaporation of ice from the surface in the summer season in the northern hemisphere and, on the other hand, supersaturates the atmosphere with ice due to the vigorous evaporation, which leads to worse consistency between the amount of the precipitated atmospheric ice and the experimental data. The full evaporation of ice from the surface increases the model sensitivity to the size of the polar cap; therefore, the increase in the

  2. 3D modeling of GJ1214b's atmosphere: vertical mixing driven by an anti-Hadley circulation

    CERN Document Server

    Charnay, Benjamin; Leconte, Jérémy

    2015-01-01

    GJ1214b is a warm sub-Neptune transiting in front of a nearby M dwarf star. Recent observations indicate the presence of high and thick clouds or haze whose presence requires strong atmospheric mixing. In order to understand the transport and distribution of such clouds/haze, we study the atmospheric circulation and the vertical mixing of GJ1214b with a 3D General Circulation Model for cloud-free hydrogen-dominated atmospheres (metallicity of 1, 10 and 100 times the solar value) and for a water-dominated atmosphere. We analyze the effect of the atmospheric metallicity on the thermal structure and zonal winds. We also analyze the zonal mean meridional circulation and show that it corresponds to an anti-Hadley circulation in most of the atmosphere with upwelling at mid-latitude and downwelling at the equator in average. This circulation must be present on a large range of synchronously rotating exoplanets with strong impact on cloud formation and distribution. Using simple tracers, we show that vertical winds o...

  3. Tests of the higher order turbulence model for atmospheric circulations (HOTMAC) at Deseret Chemical Depot

    Energy Technology Data Exchange (ETDEWEB)

    Costigan, K.R.

    1998-11-01

    Deseret Chemical Depot is one of the US Army`s storage facilities for its stockpile of chemical weapon agents. Congress has directed the Department of Defense to eliminate the aging stockpiles, which have existed since the end of World War II, and the US Army is destroying these lethal chemical munitions. Although the danger is slight, accurate predictions of the wind field in the valley are necessary for dispersion calculations in the event of an accident involving toxic chemicals at the depot. There are several small communities in Rush and Tooele valleys, including the town of Tooele, and Salt Lake City is located 65 km to the Northeast of Deseret Chemical Depot South area, at 1,300 m MSL and beyond the Oquirrh Mountains. The purpose of this report is to carry out three-dimensional numerical simulations of the atmospheric circulations in the region around Deseret Chemical Depot with the Higher Order Turbulence Model for Atmospheric Circulations (HOTMAC) and to evaluate the performance of the model. The code had been modified to assimilate local meteorological observations through the use of Newtonian nudging. The nudging scheme takes advantage of the extensive network of local observations in the valley.

  4. The Winter Atmospheric Circulation Patterns and their relationship with precipitation variability in Iran

    Science.gov (United States)

    Fattahi, E.; Sedaghatkerdar, A.

    2009-04-01

    To classify the atmospheric circulation patterns over Iran the sea level pressure and 500 hpa geopotential height for December-February of 1961-2003 was retrieved from NCEP/NCAR and used as input variables. By applying the S-mode principle component analysis (PCA) on daily composite of 500 hpa we reduced the data matrix (3880*408) to 11 components. The identified components were then rotated using varimax method in order to obtain simpler structure. The ward clustering algorithm was then used to classify studied days based on time variability of PC scores. So, by applying Ward clustering on resultant PC scores we grouped all days into 8 weather types. The relationship between frequency of various weather types and precipitation variability over Iran was investigated using correlation analysis. Moreover, the occurrences of precipitation during warm, cold and neutral phases of ENSO were also linked to the identified weather types. The results reveal that the Mediterranean low, Sub-polar low, Eastern high pressure, North high pressure and East European high pressure and also the combination of Siberian and European high pressures have the highest frequencies during El Nino periods, Whereas the Siberian high pressure and central high pressure systems are more frequent in La Nina periods. Keywords: Atmospheric circulation Patterns, principal component analysis, cluster analysis, ENSO, Iran.

  5. Linkages between atmospheric blocking, sea ice export through Fram Strait and the Atlantic Meridional Overturning Circulation

    Science.gov (United States)

    Ionita, M.; Scholz, P.; Lohmann, G.; Dima, M.; Prange, M.

    2016-09-01

    As a key persistent component of the atmospheric dynamics, the North Atlantic blocking activity has been linked to extreme climatic phenomena in the European sector. It has also been linked to Atlantic multidecadal ocean variability, but its potential links to rapid oceanic changes have not been investigated. Using a global ocean-sea ice model forced with atmospheric reanalysis data, here it is shown that the 1962–1966 period of enhanced blocking activity over Greenland resulted in anomalous sea ice accumulation in the Arctic and ended with a sea ice flush from the Arctic into the North Atlantic Ocean through Fram Strait. This event induced a significant decrease of Labrador Sea water surface salinity and an abrupt weakening of the Atlantic Meridional Overturning Circulation (AMOC) during the 1970s. These results have implications for the prediction of rapid AMOC changes and indicate that an important part of the atmosphere-ocean dynamics at mid- and high latitudes requires a proper representation of the Fram Strait sea ice transport and of the synoptic scale variability such as atmospheric blocking, which is a challenge for current coupled climate models.

  6. Taiwan Yushan Snowfall Activity and Its Association with Atmospheric Circulation from 1979 to 2009

    Institute of Scientific and Technical Information of China (English)

    TSAI Li-Min; LIU Koung-Ying; WANG Zifa

    2011-01-01

    Yushan is the most famous location for snow in Taiwan,while snowfall in the subtropical zone is rare.When it is snowing in Yushan,people are experiencing unusually cold and wet weather elsewhere in Taiwan.In this study,Yushan snowfall activity from 1979 to 2009 and the related atmosphere circulation were examined with the Taiwan Central Weather Bureau's Yushan weather station observations and the National Centers for Environmental Prediction/Department of Energy (NCEP/DOE) reanalysis atmospheric data.To provide a quantitative measure of snowfall events,a snowfall activity index (SAI) was defined in this study.The time series of yearly SAIs shows that Yushan snowfall activity for an active year,such as 1983 (SAI =39 153) was ~118 times larger than for an inactive year,such as 1999 (SAI=331).Our analyses show that snowfall activity is closely related to the position of the East Asian Trough (EAT) and the strength of the West Pacific High (WPH).In active years,when the EAT shifted eastward and the strength of WPH increased,an anomalous anticyclone occurred in the West Pacific.This anticyclone introduced anomalous southwesterly flows along the southeastern cost of mainland China and over Taiwan,resulting in a wetter-than-normal atmosphere that favored snowfall.Alternatively,in inactive years,a drierthan-normal atmosphere resulted in sluggish snowfall seasons.

  7. Boreal Atmospheric circulation patterns on the basis of the world network weather station data

    Science.gov (United States)

    Melnikov, V. A.; Moskalenko, L. V.; Golenko, N. N.; Golenko, M. N.

    2012-04-01

    Due to the recent developments of various methods of data representation in meteorology, the image of the globe-scale atmospheric circulation system has appeared. Basically, the circulation assessment is based on the indirect teleconnection method and rotated principal component analysis of the sea level pressure or geopotential height fields. These methods have several constraints because of the integration of intermittent and frontal atmospheric synoptic variability.As follows from the work of prof. B.L. Dzerdzeevskii, due to the existing of Arctic blocking processes, simplified geostrophic wind concept on the basis of the low-frequency baric patterns of the permanent centers of action, should be reconsidered in more details. For this purpose, weather station direct in-situ data with the use of progressive vector diagrams for wind speed and direction time series visualization are appropriate. Wind diagrams incorporate various fluctuations with time scales from synoptic to climatic, which can be considered without any filtration applied. The subject of work is to study the long-term wind regimes in the Northern Hemisphere, with the aim to obtain atmospheric circulation patterns in the regions of interest, in particular induced by the NAO(North Atlantic oscillation), EAWR(East Atlantic-West Russia) and SH(Siberian High) centers of action at different time and space scales. The analysis is based on the standard meteorological data (including wind direction and speed) of WMO network weather stations in the period since 1998 up to the present. For intercalibration and validation, NCEP-NCAR and QuickSCAT sea winds databases were considered, as well. Basic features of the wind variability are governed by the relevant types of the large-scale synoptic atmospheric processes, which depend upon the state of the global atmospheric circulation, their large-scale gyres and separate smaller vorticity cells. All the individual wind diagrams appear as having rather simple low

  8. Evaluating the Climate Role of Tropical Cyclones Using an Atmospheric General Circulation Model

    Science.gov (United States)

    Winterbottom, H. R.; Pegion, P. J.; Hart, R. E.

    2011-12-01

    A formal assessment and an identification for the global circulation impact of a tropical cyclone (TC) remains in the developmental stages. This area of research was first suggested by Bengtsson et al., [1982], when questions were posed regarding the role of TCs with respect to the poleward transport of heat, moisture, and momentum. To date, much attention has been paid to the role of oceanic heat transport [Emanuel, 2001; Sriver and Huber, 2007; Hart et al., 2007; Liu et al., 2008; Hu and Meehl, 2009]. Fewer studies, however, have identified an explicit role for the TC within the atmosphere, although recent work has begun to quantify the magnitude of that atmospheric footprint from reanalysis datasets [Hart et al., 2007; Schenkel and Hart, 2011]. A recent study by Hart [2011] deduced a statistical relationship between northern hemisphere TC activity (evaluated using both TC count and power dissipation [Emanuel, 2007]) and the subsequent winter climate. Hart [2011] ascertained that there exists a strong (statistical) inverse relationship between the amount of pole-ward TC power-dissipation (e.g., recurving TCs) and the 500-hPa extratropical stationary eddy-temperature flux, and speculated on the physical (and potential nonphysical) explanations for such a relationship. Indeed, the relationship was so strong that it was the most robust predictor of this measure of wind activity amidst all known teleconnection indices. These prior works provide the foundation on which to further explore the TC role in climate. Accordingly, in this study, we diagnose the climatic impact of TCs upon the Earth's general circulation using the National Center for Atmospheric Research (NCAR) Community Atmosphere Model (CAM) and the TC vortex removal procedure discussed by Winterbottom and Chassignet [2011]. A series of experiments with and without TCs will be compared. We will evaluate the mean and transient eddy fluxes as a function of a simulation with TCs and a simulation without. We

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

    Energy Technology Data Exchange (ETDEWEB)

    Plavcova, Eva [Institute of Atmospheric Physics, Academy of Sciences of the Czech Republic, Prague 4 (Czech Republic); Technical University, Department of Applied Mathematics, Liberec (Czech Republic); Charles University, Faculty of Mathematics and Physics, Prague (Czech Republic); Kysely, Jan [Institute of Atmospheric Physics, Academy of Sciences of the Czech Republic, Prague 4 (Czech Republic); Technical University, Department of Applied Mathematics, Liberec (Czech Republic)

    2012-10-15

    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

  10. Summer atmospheric circulation anomalies over the Arctic Ocean and their influences on September sea ice extent: A cautionary tale

    Science.gov (United States)

    Serreze, Mark C.; Stroeve, Julienne; Barrett, Andrew P.; Boisvert, Linette N.

    2016-10-01

    Numerous studies have addressed links between summer atmospheric circulation patterns and interannual variability and the downward trend in total September Arctic sea ice extent. In general, low extent is favored when the preceding summer is characterized by positive sea level pressure (SLP) anomalies over the central Arctic Ocean north of Alaska. High extent is favored when low pressure dominates. If such atmospheric patterns could be predicted several months out, these links provide an avenue for improved seasonal predictability of total September extent. We analyze detrended September extent time series (1979-2015), atmospheric reanalysis fields, ice age and motion, and Atmospheric Infrared Sounder data, to show that while there is merit to this summer circulation framework, it has limitations. Large departures in total September extent relative to the trend line are preceded by a wide range of summer circulation patterns. While patterns for the four years with the largest positive departures in September extent have below average SLP over the central Arctic Ocean, they differ markedly in the magnitude and location of pressure and air temperature anomalies. Differences in circulation for the four years with the largest negative departures are equally prominent. Circulation anomalies preceding Septembers with ice extent close to the trend also have a wide range of patterns. In turn, years (such as 2013 and 2014) with almost identical total September extent were preceded by very different summer circulation patterns. September ice conditions can also be strongly shaped by events as far back as the previous winter or spring.

  11. 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

  12. Recent interdecadal changes in the interannual variability of precipitation and atmospheric circulation over northern Eurasia

    Science.gov (United States)

    Hiyama, Tetsuya; Fujinami, Hatsuki; Kanamori, Hironari; Ishige, Takaya; Oshima, Kazuhiro

    2016-06-01

    This study investigated the interannual variability and trends in precipitation and atmospheric circulation patterns over northern Eurasia using long-term Precipitation REConstruction over Land and atmospheric Japanese 55-year Reanalysis data (JRA-55) from 1958 to 2012. Special emphasis was placed on the recent increase in summer (June, July and August) precipitation around the Lena river basin in eastern Siberia. We found interdecadal modulation in the relationships between interannual variability in summer precipitation and atmospheric circulation patterns among the three major Siberian river basins (Lena, Yenisei, and Ob). The interannual variations in summer precipitation over the Ob and Lena river basins were negatively correlated from the mid-1970s to the mid-1990s. However, after the mid-1990s, this negative correlation became insignificant. In contrast, a significant positive correlation was apparent between the Yenisei and Lena river basins. We also found that there has been a significant increasing (positive) trend in geopotential height in the low-level troposphere since the mid-1980s over Mongolia and European Russia, resulting in an increasing trend of westerly moisture flux into the Yenisei and Lena river basins. Summer precipitation in both basins was continuously high from 2005 to 2008 under a trough that broadly extended from the Yenisei and Lena river basins, which has been a typical pattern of interannual variation since the mid-1990s. This trough increased the meridional pressure gradient between Mongolia and eastern Siberia in combination with the trend pattern. This further enhanced the eastward moisture flux towards the Lena river basin and its convergence over the basin, resulting in high summer precipitation from 2005 to 2008.

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

    Directory of Open Access Journals (Sweden)

    A. Molod

    2014-11-01

    Full Text Available The Modern-Era Retrospective Analysis for Research and Applications-2 (MERRA2 version of the 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's MERRA2 reanalysis, the global mesoscale "nature run", 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 were shown to result in improvements at higher resolutions, and result in AGCM simulations that exhibit seamless behavior across different resolutions and applications.

  14. The annual pressure cycle on Mars: Results from the LMD Martian atmospheric general circulation model

    Science.gov (United States)

    Hourdin, Frederic; Forget, Francois; Talagrand, O.

    1993-01-01

    We have been developing a General Circulation Model (GCM) of the martian atmosphere since 1989. The model has been described rather extensively elsewhere and only the main characteristics are given here. The dynamical part of the model, adapted from the LMD terrestrial climate model, is based on a finite-difference formulation of the classical 'primitive equations of meteorology.' The radiative transfer code includes absorption and emission by CO2 (carefully validated by comparison to line-by-line calculations) and dust in the thermal range and absorption and scattering by dust in the visible range. Other physical parameterizations are included: modeling of vertical turbulent mixing, dry convective adjustment (in order to prevent vertical unstable temperature profiles), and a multilayer model of the thermal conduction in the soil. Finally, the condensation-sublimation of CO2 is introduced through specification of a pressure-dependent condensation temperature. The atmospheric and surface temperatures are prevented from falling below this critical temperature by condensation and direct precipitation onto the surface of atmospheric CO2. The only prespecified spatial fields are the surface thermal inertia, albedo, and topography.

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

    Science.gov (United States)

    Kierepko, Renata; Mietelski, Jerzy W; Ustrnul, Zbigniew; Anczkiewicz, Robert; Wershofen, Herbert; Holgye, Zoltan; Kapała, Jacek; Isajenko, Krzysztof

    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 200,000km(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 (238)Pu and for ((239+240))Pu were estimated to be a few and some tens of nBqm(-3), respectively. However, we also noted some results were much higher (even about 70 times higher) than the average concentration of (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.

  16. A model intercomparison of changes in the Atlantic thermohaline circulation in response to increasing atmospheric CO2 concentration

    OpenAIRE

    Gregory, J; Dixon, K; Stouffer, R.; Weaver, A.; E. Driesschaert; Eby, M.; Fichefet, T.; Hasumi, H.; Hu, A.; J. Jungclaus; Kamenkovich, I.; A. Levermann; Montoya, M.; Murakami, S.; Nawrath , S.

    2005-01-01

    As part of the Coupled Model Intercomparison Project, integrations with a common design have been undertaken with eleven different climate models to compare the response of the Atlantic thermohaline circulation ( THC) to time-dependent climate change caused by increasing atmospheric CO2 concentration. Over 140 years, during which the CO2 concentration quadruples, the circulation strength declines gradually in all models, by between 10 and 50%. No model shows a rapid or complete collapse, desp...

  17. Volcanic forcing improves Atmosphere-Ocean Coupled General Circulation Model scaling performance

    CERN Document Server

    Vyushin, D; Havlin, S; Bunde, A; Brenner, S; Vyushin, Dmitry; Zhidkov, Igor; Havlin, Shlomo; Bunde, Armin; Brenner, Stephen

    2004-01-01

    Recent Atmosphere-Ocean Coupled General Circulation Model (AOGCM) simulations of the twentieth century climate, which account for anthropogenic and natural forcings, make it possible to study the origin of long-term temperature correlations found in the observed records. We study ensemble experiments performed with the NCAR PCM for 10 different historical scenarios, including no forcings, greenhouse gas, sulfate aerosol, ozone, solar, volcanic forcing and various combinations, such as it natural, anthropogenic and all forcings. We compare the scaling exponents characterizing the long-term correlations of the observed and simulated model data for 16 representative land stations and 16 sites in the Atlantic Ocean for these scenarios. We find that inclusion of volcanic forcing in the AOGCM considerably improves the PCM scaling behavior. The scenarios containing volcanic forcing are able to reproduce quite well the observed scaling exponents for the land with exponents around 0.65 independent of the station dista...

  18. Relations between atmospheric circulation and mass balance of South Cascade Glacier, Washington, USA

    Science.gov (United States)

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

    1995-01-01

    The yearly net mass balance of South Cascade Glacier, Washington, has decreased since the mid-1970s. Resuls show that the decrease is primarily caused by a significant decrease in the winter mass balance. Changes in atmospheric circulation indicate a decrease in the movement of storms and moisture from the Pacific Ocean into the western contiguous United States. In addition, the increase in winter mean 700-mb heights over western Canada and the northern western contiguous United States indicates an increase in subsidence, which results in a warming and drying of the air that further reduces precipitation and also increases the ratio of rain to snow during the cold season. These factors contribute to below-average winter mass balances. -from Authors

  19. 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.

  20. Migration history of air-breathing fishes reveals Neogene atmospheric circulation patterns

    Science.gov (United States)

    Böhme, M.

    2004-05-01

    The migration history of an air-breathing fish group (Channidae; snakehead fishes) is used for reconstructing Neogene Eurasian precipitation and atmospheric circulation patterns. The study shows that snakeheads are sensitive indicators of summer precipitation maxima in subtropical and temperate regions, and are present regularly if the wettest month exceeds 150 mm precipitation and 20 °C mean temperature. The analysis of 515 fossil freshwater fish deposits of the past 50 m.y. from Africa and Eurasia shows two continental-scale migration events from the snakeheads' center of origin in the south Himalayan region, events that can be related to changes in the Northern Hemisphere circulation pattern. The first migration, ca. 17.5 Ma, into western and central Eurasia may have been caused by a northward shift of the Intertropical Convergence Zone that brought western Eurasia under the influence of trade winds that produced a zonal and meridional precipitation gradient in Europe. During the second migration, between 8 and 4 Ma, into Africa and East Asia, snakeheads reached their present-day distribution. This migration could have been related to the intensification of the Asian monsoon that brought summer precipitation to their migratory pathways in East Africa Arabia and East Asia.

  1. Turbulent circulation above the surface heat source in stably stratified atmosphere

    Science.gov (United States)

    Kurbatskii, A. F.; Kurbatskaya, L. I.

    2016-10-01

    The 3-level RANS approach for simulating a turbulent circulation over the heat island in a stably stratified environment under nearly calm conditions is formulated. The turbulent kinetic energy its spectral consumption (dissipation) and the dispersion of turbulent fluctuations of temperature are found from differential equations, thus the correct modeling of transport processes in the interface layer with the counter-gradient heat flux is assured. The three-parameter turbulence RANS approach minimizes difficulties in simulating the turbulent transport in a stably stratified environment and reduces efforts needed for the numerical implementation of the 3-level RANS approach. Numerical simulation of the turbulent structure of the penetrative convection over the heat island under conditions of stably stratified atmosphere demonstrates that the three-equation model is able to predict the thermal circulation induced by the heat island. The temperature distribution, root-mean-square fluctuations of the turbulent velocity and temperature fields and spectral turbulent kinetic energy flux are in good agreement with the experimental data. The model describes such thin physical effects, as a crossing of vertical profiles of temperature of a thermal plume with the formation of the negative buoyancy area testifying to development of the dome-shaped form at the top part of a plume in the form of "hat".

  2. Arctic sea ice and atmospheric circulation under the abrupt4xCO2 scenario

    Institute of Scientific and Technical Information of China (English)

    YU Xiaoyong; Annette Rinke; JI Duoying; CUI Xuefeng; John C Moore

    2014-01-01

    We analyze sea ice changes from eight different earth system models that have conducted experiment abrupt4xCO2 of the Coupled Model Intercomparison Project Phase 5 (CMIP5). In response to abrupt quadrupling of CO2 from preindustrial levels, Arctic temperatures dramatically rise by about 10°C—16°C in winter and the seasonal sea ice cycle and sea ice concentration are signiifcantly changed compared with the pre-industrial control simulations (piControl). Changes of Arctic sea ice concentration are spatially correlated with temperature patterns in all seasons and highest in autumn. Changes in sea ice are associated with changes in atmospheric circulation patterns at heights up to the jet stream. While the pattern of sea level pressure changes is generally similar to the surface air temperature change pattern, the wintertime 500 hPa circulation displays a positive Paciifc North America (PNA) anomaly under abrupt4xCO2-piControl. This large scale teleconnection may contribute to, or feedback on, the simulated sea ice cover change and is associated with an intensiifcation of the jet stream over East Asia and the north Paciifc in winter.

  3. Quantifying the roles of ocean circulation and biogeochemistry in governing ocean carbon-13 and atmospheric carbon dioxide at the last glacial maximum

    OpenAIRE

    Tagliabue, A.; L. Bopp; Roche, D. M.; N. Bouttes; J.-C. Dutay; Alkama, R.; Kageyama, M.; Michel, E.; Paillard, D.

    2009-01-01

    We use a state-of-the-art ocean general circulation and biogeochemistry model to examine the impact of changes in ocean circulation and biogeochemistry in governing the change in ocean carbon-13 and atmospheric CO2 at the last glacial maximum (LGM). We examine 5 different realisations of the ocean's overturning circulation produced by a fully coupled atmosphere-ocean model under LGM forcing and suggested changes in the atmospheric deposition of iron and phytoplankton ph...

  4. Multidecadal changes in the relationship between extreme temperature events in Uruguay and the general atmospheric circulation

    Energy Technology Data Exchange (ETDEWEB)

    Renom, Madeleine; Barreiro, Marcelo [Universidad de la Republica, Unidad de Ciencias de la Atmosfera, Instituto de Fisica, Facultad de Ciencias, Montevideo (Uruguay); Rusticucci, Matilde [Universidad de Buenos Aires, Departamento de Ciencias de la Atmosfera y los Oceanos, Facultad de Ciencias Exactas y Naturales, Buenos Aires (Argentina)

    2011-12-15

    We analyze changes in the relationship between extreme temperature events and the large scale atmospheric circulation before and after the 1976 climate shift. To do so we first constructed a set of two temperature indices that describe the occurrence of warm nights (TN90) and cold nights (TN10) based on a long daily observed minimum temperature database that spans the period 1946-2005, and then divided the period into two subperiods of 30 years each (1946-1975 and 1976-2005). We focus on summer (TN10) and winter (TN90) seasons. During austral summer before 1976 the interannual variability of cold nights was characterized by a negative phase of the Southern Annular Mode (SAM) with a cyclonic anomaly centered off Uruguay that favoured the entrance of cold air from the south. After 1976 cold nights are associated not with the SAM, but with an isolated vortex at upper levels over South Eastern South America. During austral winter before 1976, the El Nino phenomenon dominated the interannual variability of warm nights through an increase in the northerly warm flow into Uruguay. However, after 1976 the El Nino connection weakened and the variability of warm nights is dominated by a barotropic anticyclonic anomaly located in the South Atlantic and a low pressure center over South America. This configuration also strengthens the northward flow of warm air into Uruguay. Our results suggest that changes in El Nino evolution after 1976 may have played a role in altering the relationship between temperature extreme events in Uruguay and the atmospheric circulation. (orig.)

  5. Why was Atmospheric Circulation Decoupled from Tropical Pacific SSTs in 2014/15 winter?

    Science.gov (United States)

    Peng, P.

    2015-12-01

    In late 2014 and early 2015, although Niño3.4 index exceeded the threshold for a weak-moderate El Niño, a canonical atmospheric response to ENSO event was not observed in the central and eastern equatorial Pacific. In an effort to understand why it was so, this study decomposed the DJF mean sea surface temperature (SST), precipitation rate and 200hPa stream function anomalies observed in the 2014/15 winter into the patterns related to the principal components of the DJF SST variability. It is found that the anomalies of these variables were mainly determined by the patterns related to two SST modes, one is the North Pacific Mode (NPM), and the other the El Niño and South Oscillation (ENSO) mode. The NPM was the dominant factor and was responsible for the apparent uncoupled air-sea relationship in the central equatorial Pacific and the east-west structure of the circulation anomalies over North America. The ENSO mode was important for SSTs in the central and eastern equatorial Pacific and for the circulation in the central equatorial Pacific. Further, ENSO signal likely evolved from the NPM pattern in the 2013/14 winter, however, its full development was impeded by the unusual persistence of the strong NPM throughout the year. The analysis for DJF 2014/15 winter indicates that the SST anomalies in Niño3.4 alone were not adequate for capturing the coupling of ocean and atmosphere anomalies in the tropical Pacific, due to the fact that it can't distinguish if the SST anomaly in the Niño3.4 region is associated with the ENSO mode or NPM, or both.

  6. Using Atmospheric Circulation Patterns to Detect and Attribute Changes in the Risk of Extreme Climate Events

    Science.gov (United States)

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

    2015-12-01

    Because of the high cost of extreme events and the growing evidence that global warming is likely to alter the statistical distribution of climate variables, detection and attribution of changes in the probability of extreme climate events has become a pressing topic for the scientific community, elected officials, and the public. While most of the emphasis has thus far focused on analyzing the climate variable of interest (most often temperature or precipitation, but also flooding and drought), there is an emerging emphasis on applying detection and attribution analysis techniques to the underlying physical causes of individual extreme events. This approach is promising in part because the underlying physical causes (such as atmospheric circulation patterns) can in some cases be more accurately represented in climate models than the more proximal climate variable (such as precipitation). In addition, and more scientifically critical, is the fact that the most extreme events result from a rare combination of interacting causes, often referred to as "ingredients". Rare events will therefore always have a strong influence of "natural" variability. Analyzing the underlying physical mechanisms can therefore help to test whether there have been changes in the probability of the constituent conditions of an individual event, or whether the co-occurrence of causal conditions cannot be distinguished from random chance. This presentation will review approaches to applying detection/attribution analysis to the underlying physical causes of extreme events (including both "thermodynamic" and "dynamic" causes), and provide a number of case studies, including the role of frequency of atmospheric circulation patterns in the probability of hot, cold, wet and dry events.

  7. Black carbon ageing in the Canadian Centre for Climate modelling and analysis atmospheric general circulation model

    Directory of Open Access Journals (Sweden)

    B. Croft

    2005-01-01

    Full Text Available Black carbon (BC particles in the atmosphere have important impacts on climate. The amount of BC in the atmosphere must be carefully quantified to allow evaluation of the climate effects of this type of aerosol. In this study, we present the treatment of BC aerosol in the developmental version of the 4th generation Canadian Centre for Climate modelling and analysis (CCCma atmospheric general circulation model (AGCM. The focus of this work is on the conversion of insoluble BC to soluble/mixed BC by physical and chemical ageing. Physical processes include the condensation of sulphuric and nitric acid onto the BC aerosol, and coagulation with more soluble aerosols such as sulphates and nitrates. Chemical processes that may age the BC aerosol include the oxidation of organic coatings by ozone. Four separate parameterizations of the ageing process are compared to a control simulation that assumes no ageing occurs. These simulations use 1 an exponential decay with a fixed 24h half-life, 2 a condensation and coagulation scheme, 3 an oxidative scheme, and 4 a linear combination of the latter two ageing treatments. Global BC burdens are 2.15, 0.15, 0.11, 0.21, and 0.11TgC for the control run, and four ageing schemes, respectively. The BC lifetimes are 98.1, 6.6, 5.0, 9.5, and 4.9 days, respectively. The sensitivity of modelled BC burdens, and concentrations to the factor of two uncertainty in the emissions inventory is shown to be greater than the sensitivity to the parameterization used to represent the BC ageing, except for the oxidation based parameterization. A computationally efficient parameterization that represents the processes of condensation, coagulation, and oxidation is shown to simulate BC ageing well in the CCCma AGCM. As opposed to the globally fixed ageing time scale, this treatment of BC ageing is responsive to varying atmospheric composition.

  8. Combining Abundance/Temperature Retrieval with 3D Atmospheric Circulation Simulations of Hot Jupiters

    Science.gov (United States)

    Heng, Kevin

    2011-09-01

    The atmospheres of hot Jupiters are three-dimensional, non-linear entities and understanding them requires the construction of a hierarchy of models of varying sophistication. Since previous work has either focused on the atmospheric dynamics or implemented multi-band radiative transfer, a reasonable approach is to combine the treatment of 3D dynamics with dual-band radiative transfer, where the assumption is that the stellar irradiation and re-emitted radiation from the exoplanet are at distinct wavelengths. I report on the successful implementation of such a setup and demonstrate how it can be used to compute self-consistent temperature-pressure profiles on both the day and night sides of a hot Jupiter, as well as zonal-wind profiles, circulation cell patterns and the angular/temporal offset of the hotspot from the substellar point. In particular, the hotspot offset should aid us in distinguishing between different types of hot Jupiter atmospheres. Together with N. Madhusudhan, we combine the dual-band simulation technique with the abundance/temperature retrieval method of Madhusudhan & Seager, by empirically constraining a range of values for the broad-band opacities which are consistent with the current observations. The advantage of our novel method is that the range of opacities used improves with time as the observations get better. The ability to thoroughly, efficiently and systematically explore the interplay between atmospheric dynamics, radiation and synthetic spectra is an important step forward, as it prepares us for the theoretical interpretation of exoplanetary spectra which will be obtained by future space-based missions such as JWST and EChO. I acknowledge generous support from the Zwicky Prize Fellowship and the Star and Planet Formation Group (PI: Michael Meyer) at ETH Zurich.

  9. On the effects of constraining atmospheric circulation in a coupled atmosphere-ocean Arctic regional climate model

    Science.gov (United States)

    Berg, Peter; Döscher, Ralf; Koenigk, Torben

    2016-06-01

    Impacts of spectral nudging on simulations of Arctic climate in coupled simulations have been investigated in a set of simulations with a regional climate model (RCM). The dominantly circumpolar circulation in the Arctic lead to weak constraints on the lateral boundary conditions (LBCs) for the RCM, which causes large internal variability with strong deviations from the driving model. When coupled to an ocean and sea ice model, this results in sea ice concentrations that deviate from the observed spatial distribution. Here, a method of spectral nudging is applied to the atmospheric model RCA4 in order to assess the potentials for improving results for the sea ice concentrations when coupled to the RCO ocean-sea ice model. The spectral nudging applied to reanalysis driven simulations significantly improves the generated sea ice regarding its temporal evolution, extent and inter-annual trends, compared to simulations with standard LBC nesting. The method is furthermore evaluated with driving data from two CMIP5 GCM simulations for current and future conditions. The GCM biases are similar to the RCA4 biases with ERA-Interim, however, the spectral nudging still improves the surface winds enough to show improvements in the simulated sea ice. For both GCM downscalings, the spectrally nudged version retains a larger sea ice extent in September further into the future. Depending on the sea ice formulation in the GCM, the temporal evolution of the regional sea ice model can deviate strongly.

  10. Nonlinear winter atmospheric circulation response to Arctic sea ice concentration anomalies for different periods during 1966-2012

    Science.gov (United States)

    Semenov, V. A.; Latif, M.

    2015-05-01

    The early 21st century was marked by several severe winters over Central Eurasia linked to a blocking anti-cyclone centered south of the Barents Sea. Severe winters in Central Eurasia were frequent in the 1960s when Arctic sea ice cover was anomalously large, and rare in the 1990s featuring considerably less sea ice cover; the 1960s being characterized by a low, the 1990s by a high phase of the North Atlantic Oscillation, the major driver of surface climate variability in Central Eurasia. We performed ensemble simulations with an atmospheric general circulation model using a set of multi-year Arctic sea ice climatologies corresponding to different periods during 1966-2012. The atmospheric response to the strongly reduced sea ice cover of 2005-2012 exhibits a statistically significant anti-cyclonic surface pressure anomaly which is similar to that observed. A similar response is found when the strongly positive sea ice cover anomaly of 1966-1969 drives the model. Basically no significant atmospheric circulation response was simulated when the model was forced by the sea ice cover anomaly of 1990-1995. The results suggest that sea ice cover reduction, through a changed atmospheric circulation, considerably contributed to the recent anomalously cold winters in Central Eurasia. Further, a nonlinear atmospheric circulation response to shrinking sea ice cover is suggested that depends on the background sea ice cover.

  11. Summer Asian-Pacific Oscillation and Its Relationship with Atmospheric Circulation and Monsoon Rainfall

    Institute of Scientific and Technical Information of China (English)

    ZHAO Ping; CHEN Junming; XIAO Dong; NAN Sulan; ZOU Yan; ZHOU Botao

    2008-01-01

    Using the ERA-40 data and numerical simulations, this study investigated the teleconnection over the extratropical Asian-Pacific region and its relationship with the Asian monsoon rainfall and the climatological characteristics of tropical cyclones over the western North Pacific, and analyzed impacts of the Tibetan Plateau (TP) heating and Pacific sea surface temperature (SST) on the teleconnection. The Asian-Pacific oscillation (APO) is defined as a zonal seesaw of the tropospheric temperature in the midlatitudes of the Asian-Pacific region. When the troposphere is cooling in the midlatitudes of the Asian continent, it is warming in the midlatitudes of the central and eastern North Pacific; and vice versa. The APO also appears in the stratosphere, but with a reversed phase. Used as an index of the thermal contrast between Asia and the North Pacific, it provides a new way to explore interactions between the Asian and Pacific atmospheric circulations. The APO index exhibits the interannual and interdecadal variability. It shows a downward trend during 1958-2001, indicating a weakening of the thermal contrast, and shows a 5.5-yr oscillation period. The formation of the APO is associated with the zonal vertical circulation caused by a difference in the solar radiative heating between the Asian continent and the North Pacific. The numerical simulations further reveal that the summer TP heating enhances the local tropospheric temperature and upward motion, and then strengthens downward motion and decreases the tropospheric temperature over the central and eastern North Pacific. This leads to the formation of the APO. The Pacific decadal oscillation and El Nino/La Nina over the tropical eastern Pacific do not exert strong influences on the APO. When there is an anomaly in the summer APO, the South Asian high, the westerly jet over Eurasia, the tropical easterly jet over South Asia, and the subtropical high over the North Pacific change significantly, with anomalous Asian

  12. Performance of a reconfigured atmospheric general circulation model at low resolution

    Science.gov (United States)

    Wen, Xinyu; Zhou, Tianjun; Wang, Shaowu; Wang, Bin; Wan, Hui; Li, Jian

    2007-07-01

    Paleoclimate simulations usually require model runs over a very long time. The fast integration version of a state-of-the-art general circulation model (GCM), which shares the same physical and dynamical processes but with reduced horizontal resolution and increased time step, is usually developed. In this study, we configure a fast version of an atmospheric GCM (AGCM), the Grid Atmospheric Model of IAP/LASG (Institute of Atmospheric Physics/State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics), at low resolution (GAMIL-L, hereafter), and compare the simulation results with the NCEP/NCAR reanalysis and other data to examine its performance. GAMIL-L, which is derived from the original GAMIL, is a finite difference AGCM with 72×40 grids in longitude and latitude and 26 vertical levels. To validate the simulated climatology and variability, two runs were achieved. One was a 60-year control run with fixed climatological monthly sea surface temperature (SST) forcing, and the other was a 50-yr (1950 2000) integration with observational time-varying monthly SST forcing. Comparisons between these two cases and the reanalysis, including intra-seasonal and inter-annual variability are also presented. In addition, the differences between GAMIL-L and the original version of GAMIL are also investigated. The results show that GAMIL-L can capture most of the large-scale dynamical features of the atmosphere, especially in the tropics and mid latitudes, although a few deficiencies exist, such as the underestimated Hadley cell and thereby the weak strength of the Asia summer monsoon. However, the simulated mean states over high latitudes, especially over the polar regions, are not acceptable. Apart from dynamics, the thermodynamic features mainly depend upon the physical parameterization schemes. Since the physical package of GAMIL-L is exactly the same as the original high-resolution version of GAMIL, in which the NCAR Community

  13. Performance of a Reconfigured Atmospheric General Circulation Model at Low Resolution

    Institute of Scientific and Technical Information of China (English)

    WEN Xinyu; ZHOU Tianjun; WANG Shaowu; WANG Bin; WAN Hui; LI Jian

    2007-01-01

    Paleoclimate simulations usually require model runs over a very long time. The fast integration version of a state-of-the-art general circulation model (GCM), which shares the same physical and dynamical processes but with reduced horizontal resolution and increased time step, is usually developed. In this study, we configure a fast version of an atmospheric GCM (AGCM), the Grid Atmospheric Model of IAP/LASG(Institute of Atmospheric Physics/State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics), at low resolution (GAMIL-L, hereafter), and compare the simulation results with the NCEP/NCAR reanalysis and other data to examine its performance. GAMIL-L, which is derived from the original GAMIL, is a finite difference AGCM with 72×40 grids in longitude and latitude and 26 vertical levels. To validate the simulated climatology and variability, two runs were achieved. One was a 60-year control run with fixed climatological monthly sea surface temperature (SST) forcing, and the other was a 50-yr (1950-2000) integration with observational time-varying monthly SST forcing. Comparisons between these two cases and the reanalysis, including intra- seasonal and inter-annual variability are also presented. In addition, the differences between GAMIL-L and the original version of GAMIL are also investigated.The results show that GAMIL-L can capture most of the large-scale dynamical features of the atmosphere,especially in the tropics and mid latitudes, although a few deficiencies exist, such as the underestimated Hadley cell and thereby the weak strength of the Asia summer monsoon. However, the simulated mean states over high latitudes, especially over the polar regions, are not acceptable. Apart from dynamics, the thermodynamic features mainly depend upon the physical parameterization schemes. Since the physical package of GAMIL-L is exactly the same as the original high-resolution version of GAMIL, in which the NCAR Community

  14. Changes in Atlantic Thermohaline Circulation under Different Atmospheric CO2 Scenarios in a Climate Model

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The changes in the thermohaline circulation (THC) because of the increased CO2 in the atmosphere play an important role in future climate regimes.In this article, a new climate model developed at the Max-Planck Institute for Meteorology is used to study the variation in THC strength, the changes of North Atlantic deep-water (NADW) formation, and the regional responses of the THC in the North Atlantic to increasing atmospheric CO2.From 2000 to 2100, under increased CO2 scenarios (B1, A1B, and A2), the strength of THC decreases by 4 Sv (106 m3/s), 5.1 Sv, and 5.2 Sv, respectively, equivalent to a reduction of 20%, 25%, and 25.1% of the present THC strength.The analyses show that the oceanic deep convective activity significantly strengthens in the Greenland-Iceland-Norway(GIN) Seas owing to saltier (denser) upper oceans, whereas weakens in the Labrador Sea and in the south of the Denmark Strait region (SDSR) because of surface warming and freshening due to global warming.The saltiness of the GIN Seas is mainly caused by the increase of the saline North Atlantic inflow through the Faro-Bank (FB) Channel.Under the scenario A1B, the deep-water formation rate in the North Atlantic decreases from 16.2 Sv to 12.9 Sv with increasing CO2.

  15. On the Observed Relationships between Variability in Gulf Stream Sea Surface Temperatures and the Atmospheric Circulation in the North Atlantic

    Science.gov (United States)

    Wills, Samantha; Thompson, David; Ciasto, Laura

    2016-04-01

    The advent of increasingly high-resolution satellite observations and numerical models has led to a series of advances in our understanding of the role of midlatitude sea surface temperature (SST) in climate variability, especially near western boundary currents (WBC). Observational analyses have suggested that ocean dynamics play a central role in driving interannual SST variability over the Kuroshio-Oyashio and Gulf Stream extensions. Numerical experiments have suggested that variations in the SST field within these WBC regions may have a much more pronounced influence on the atmospheric circulation than previously thought. In this study, the authors examine the observational support for (or against) a robust atmospheric response to midlatitude SST variability in the Gulf Stream extension. To do so, lead/lag analysis based on daily-mean data is applied to assess the evidence for two-way coupling between SST anomalies and the atmospheric circulation on transient timescales, building off of previous studies that have utilized weekly data. A novel decomposition approach is employed to demonstrate that atmospheric circulation anomalies over the Gulf Stream extension can be separated into two distinct patterns of midlatitude atmosphere/ocean interaction: 1) a pattern that peaks 2-3 weeks before the largest SST anomalies in the Gulf Stream extension, which can be viewed as the "atmospheric forcing" and 2) a pattern that peaks several weeks after the largest SST anomalies, which the authors argue can be viewed as the "atmospheric response". The latter pattern is linearly independent of the former, and is interpreted as the potential response of the atmospheric circulation to SST variability in the Gulf Stream extension.

  16. Climate forcings and climate sensitivities diagnosed from atmospheric global circulation models

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, Bruce T. [Boston University, Department of Geography and Environment, Boston, MA (United States); Knight, Jeff R.; Ringer, Mark A. [Met Office Hadley Centre, Exeter (United Kingdom); Deser, Clara; Phillips, Adam S. [National Center for Atmospheric Research, Boulder, CO (United States); Yoon, Jin-Ho [University of Maryland, Cooperative Institute for Climate and Satellites, Earth System Science Interdisciplinary Center, College Park, MD (United States); Cherchi, Annalisa [Centro Euro-Mediterraneo per i Cambiamenti Climatici, and Istituto Nazionale di Geofisica e Vulcanologia, Bologna (Italy)

    2010-12-15

    Understanding the historical and future response of the global climate system to anthropogenic emissions of radiatively active atmospheric constituents has become a timely and compelling concern. At present, however, there are uncertainties in: the total radiative forcing associated with changes in the chemical composition of the atmosphere; the effective forcing applied to the climate system resulting from a (temporary) reduction via ocean-heat uptake; and the strength of the climate feedbacks that subsequently modify this forcing. Here a set of analyses derived from atmospheric general circulation model simulations are used to estimate the effective and total radiative forcing of the observed climate system due to anthropogenic emissions over the last 50 years of the twentieth century. They are also used to estimate the sensitivity of the observed climate system to these emissions, as well as the expected change in global surface temperatures once the climate system returns to radiative equilibrium. Results indicate that estimates of the effective radiative forcing and total radiative forcing associated with historical anthropogenic emissions differ across models. In addition estimates of the historical sensitivity of the climate to these emissions differ across models. However, results suggest that the variations in climate sensitivity and total climate forcing are not independent, and that the two vary inversely with respect to one another. As such, expected equilibrium temperature changes, which are given by the product of the total radiative forcing and the climate sensitivity, are relatively constant between models, particularly in comparison to results in which the total radiative forcing is assumed constant. Implications of these results for projected future climate forcings and subsequent responses are also discussed. (orig.)

  17. Numerical Study of the Effects of Topography and Urbanization on the Local Atmospheric Circulations over the Beijing-Tianjin-Hebei, China

    Directory of Open Access Journals (Sweden)

    Yucong Miao

    2015-01-01

    Full Text Available The effects of the topography and urbanization on the local atmospheric circulations over the Beijing-Tianjin-Hebei (BTH region were studied by the weather research and forecasting (WRF model, as well as the interactions among these local atmospheric circulations. It was found that, in the summer day time, the multiscale thermally induced local atmospheric circulations may exist and interact in the same time over the BTH region; the topography played a role in the strengthening of the sea breeze circulations; after sunset, the inland progress of sea breeze was slowed down by the opposite mountain breeze; when the land breeze circulation dominated the Bohai bay, the mountain breeze circulation can couple with the land breeze circulation to form a large circulation ranging from the coastline to the mountains. And the presence of cities cannot change the general state of the sea-land breeze (SLB circulation and mountain-valley breeze (MVB circulation but acted to modify these local circulations slightly. Meanwhile, the development of the urban heat island (UHI circulation was also strongly influenced by the nearby SLB circulation and MVB circulation.

  18. Reconstruction of Early Pleistocene climate in southern Australia, and implications for Southern Hemisphere atmospheric circulation

    Science.gov (United States)

    Sniderman, K.; Porch, N.

    2009-12-01

    Southern Australia today experiences a winter-dominated rainfall regime, governed by the seasonal migration of the Southern Hemisphere subtropical anticyclone. The history of this rainfall seasonality regime is poorly understood, because well dated, late Neogene climate records are scarce, both in Australia and in the Southern Hemisphere more generally. However, it has been assumed that the initiation of this rainfall regime was linked to the onset of extensive Northern Hemisphere glaciation, around 2.6 Ma. Here, we use fossil beetle remains from an upland southeastern Australian palaeolake record to quantitatively reconstruct regional climate during ~280 kyr of the Early Pleistocene, between 1.84-1.56 Ma. Our results, based on coexistence of extant fossil beetle taxa, indicate that temperatures were consistently 1-3°C warmer than present, and annual rainfall as high as or higher than today, but summer rainfall was 2-2.4 times higher than today, throughout the period of our record. This is consistent with the presence in the associated pollen record of diverse rainforest plant taxa, many of which are now extinct regionally or Australia-wide. Our results indicate that the modern, winter-dominated rainfall regime was not yet in place by 1.5 Ma, at least one million years later than previously thought. In as much as the modern climate regime is a function of the intensity of atmospheric circulation driven by hemispheric temperature gradients, this implies that Southern Hemisphere anticyclonic circulation may have been much less intense than today during the Early Pleistocene, and that a major regional climate reorganisation (Ravelo et al., 2004) occurred sometime after 1.5 Ma, perhaps associated with further growth of the Antarctic cryosphere (Raymo et al., 2006).

  19. 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.)

  20. The Improvement of The Absorption Process Using A Computational Optimization in An Atmospheric General Circulation Model

    Science.gov (United States)

    Sekiguchi, Miho; Nakajima, Teruyuki

    2009-03-01

    This study improves the gaseous absorption process scheme of the broadband radiative transfer code "mstrnX" that was developed by the Center for Climate System Research (CCSR) for efficient calculation of atmospheric radiative transfer in the general circulation models. This scheme is adopted the optimization method to decrease the number of quadrature points for wavenumber integration by using the correlated k-distribution method and to increase the computational efficiency in each spectral band. The objective function of the standard version is defined as the sum of errors in radiation fluxes and heating rate in six standard atmospheres, and we added six other atmospheric profiles in the doubling CO2 condition for the doubling CO2 version. The preferable errors of radiative flux is thought about 1-2 W/m2, however, it is desirable that the errors of radiative forcing of CO2 is less than 0.3 W/m2. So, we improve the doubling CO2 version to calculate the radiative forcings precisely. When integration points and weights are determined in each band, we select the results whose errors of the instantaneous radiative forcing at TOA, troposphere and surface are under 0.2 W/m2. Moreover, radiative forcings of other WMGHGs are considered as same as CO2. Then, we build a global warming version with 29 bands and 111 integration points. In this version, the maximum radiation flux error is less than 0.6 W/m2 in LW and 0.45 W/m2 in SW at all altitude, and the maximum heating rate error is less than 0.2 K/day in the troposphere and the stratosphere for any standard atmosphere. The radiative forcing can be evaluated with small errors not exceeding one standard deviation of samples of forcings from the AOGCMs except for the changes of N2O+CFCs case in the RTMIP experiment. It is found that the proposed optimization method is effective in maintaining a low computational cost with accuracy good enough for dynamical simulations with a GCM. MstrnX is now available from the Open

  1. 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.

  2. Interdecadal Variability of the East Asian Summer Monsoon and Associated Atmospheric Circulations

    Institute of Scientific and Technical Information of China (English)

    ZENG Gang; SUN Zhaobo; Wei-Chyung WANG; MIN Jinzhong

    2007-01-01

    Based on the National Centers for Environmental Prediction and National Center for Atmospheric Research (NCEP/NCAR) reanalysis data from 1950-1999, interdecadal variability of the East Asian Summer Monsoon (EASM) and its associated atmospheric circulations are investigated. The EASM exhibits a distinct interdecadal variation, with stronger (weaker) summer monsoon maintained from 1950-1964 (1976-1997).In the former case, there is an enhanced Walker cell in the eastern Pacific and an anti-Walker cell in the western Pacific. The associated ascending motion resides in the central Pacific, which flows eastward and westward in the upper troposphere, descending in the eastern and western ends of the Pacific basin. At the same time, an anomalous East Asian Hadley Cell (EAHC) is found to connect the low-latitude and mid-latitude systems in East Asia, which strengthens the EASM. The descending branch of the EAHC lies in the west part of the anti-Walker cell, flowing northward in the lower troposphere and then ascending at the south of Lake Baikal (40°-50°N, 95°-115°E) before returning to low latitudes in the upper troposphere,thus strengthening the EASM.The relationship between the EASM and SST in the eastern tropical Pacific is also discussed. A possible mechanism is proposed to link interdecadal variation of the EASM with the eastern tropical Pacific SST. A warmer sea surface temperature anomaly (SSTA) therein induces anomalous ascending motion in the eastern Pacific, resulting in a weaker Walker cell, and at the same time inducing an anomalous Walker cell in the western Pacific and an enhanced EAHC, leading to a weaker EASM. Furthermore, the interdecadal variation of summer precipitation over North China is found to be strongly regulated by the velocity potential over the south of Lake Baikal through enhancing and reducing the regional vertical motions.

  3. 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

  4. THOR: A New and Flexible Global Circulation Model to Explore Planetary Atmospheres

    Science.gov (United States)

    Mendonça, João M.; Grimm, Simon L.; Grosheintz, Luc; Heng, Kevin

    2016-10-01

    We have designed and developed, from scratch, a global circulation model (GCM) named THOR that solves the three-dimensional nonhydrostatic Euler equations. Our general approach lifts the commonly used assumptions of a shallow atmosphere and hydrostatic equilibrium. We solve the “pole problem” (where converging meridians on a sphere lead to increasingly smaller time steps near the poles) by implementing an icosahedral grid. Irregularities in the grid, which lead to grid imprinting, are smoothed using the “spring dynamics” technique. We validate our implementation of spring dynamics by examining calculations of the divergence and gradient of test functions. To prevent the computational time step from being bottlenecked by having to resolve sound waves, we implement a split-explicit method together with a horizontally explicit and vertically implicit integration. We validate our GCM by reproducing the Earth and hot-Jupiter-like benchmark tests. THOR was designed to run on graphics processing units (GPUs), which allows for physics modules (radiative transfer, clouds, chemistry) to be added in the future, and is part of the open-source Exoclimes Simulation Platform (www.exoclime.org).

  5. Extreme Associated Functions: Optimally Linking Local Extremes to Large-scale Atmospheric Circulation Structures

    CERN Document Server

    Panja, Debabrata

    2007-01-01

    We present a new statistical method to optimally link local weather extremes to large-scale atmospheric circulation structures. The method is illustrated using July-August daily mean temperature at 2m height (T2m) time-series over the Netherlands and 500 hPa geopotential height (Z500) time-series over the Euroatlantic region of the ECMWF reanalysis dataset (ERA40). The method identifies patterns in the Z500 time-series that optimally describe, in a precise mathematical sense, the relationship with local warm extremes in the Netherlands. Two patterns are identified; the most important one corresponds to a blocking high pressure system leading to subsidence and calm, dry and sunny conditions over the Netherlands. The second one corresponds to a rare, easterly flow regime bringing warm, dry air into the region. The patterns are robust; they are also identified in shorter subsamples of the total dataset. The method is generally applicable and might prove useful in evaluating the performance of climate models in s...

  6. MJO prediction skill, predictability, and teleconnection impacts in the Beijing Climate Center Atmospheric General Circulation Model

    Science.gov (United States)

    Wu, Jie; Ren, Hong-Li; Zuo, Jinqing; Zhao, Chongbo; Chen, Lijuan; Li, Qiaoping

    2016-09-01

    This study evaluates performance of Madden-Julian oscillation (MJO) prediction in the Beijing Climate Center Atmospheric General Circulation Model (BCC_AGCM2.2). By using the real-time multivariate MJO (RMM) indices, it is shown that the MJO prediction skill of BCC_AGCM2.2 extends to about 16-17 days before the bivariate anomaly correlation coefficient drops to 0.5 and the root-mean-square error increases to the level of the climatological prediction. The prediction skill showed a seasonal dependence, with the highest skill occurring in boreal autumn, and a phase dependence with higher skill for predictions initiated from phases 2-4. The results of the MJO predictability analysis showed that the upper bounds of the prediction skill can be extended to 26 days by using a single-member estimate, and to 42 days by using the ensemble-mean estimate, which also exhibited an initial amplitude and phase dependence. The observed relationship between the MJO and the North Atlantic Oscillation was accurately reproduced by BCC_AGCM2.2 for most initial phases of the MJO, accompanied with the Rossby wave trains in the Northern Hemisphere extratropics driven by MJO convection forcing. Overall, BCC_AGCM2.2 displayed a significant ability to predict the MJO and its teleconnections without interacting with the ocean, which provided a useful tool for fully extracting the predictability source of subseasonal prediction.

  7. Impacts of atmospheric circulations on aerosol distributions in autumn over eastern China: observational evidences

    Science.gov (United States)

    Zheng, X.-Y.; Fu, Y.-F.; Yang, Y.-J.; Liu, G.-S.

    2015-02-01

    Regional heavy pollution events in East China (110-122° E, 28-40° N) are the main environmental problems recently because of the high urbanization and rapid economic development connected with too much emissions of pollutants. However, appropriate weather condition is another factor which cannot be ignored for these events. In this study, the relationship between regional pollution status and larger scale atmospheric circulations over East China in October is investigated using ten-year (2001-2010) MODIS/Terra aerosol optical depth (AOD) product and the NCEP reanalysis data together with case analysis and composite analysis. Generally, statistics in East China show values of mean AOD vary from 0.3 to 0.9 in October over the region, and larger AOD variances are accompanied with the distribution of higher average AOD. Eighteen pollution episodes (regional mean AOD > 0.6) and ten clean episodes (regional mean AOD China or steady straight westerly in middle troposphere, particularly the rear of anticyclone at 850 hPa, are typical weather patterns responsible for heavy pollution events, while clean episodes occur when strong southeastward cold air advection prevails below the middle troposphere or air masses are transported from sea to the mainland. The above studies are especially useful to the government decision make on balance of economic activities and pollution mitigations.

  8. Effects of Variations in East Asian Snow Cover on Modulating Atmospheric Circulation over the North Pacific Ocean.

    Science.gov (United States)

    Clark, Martyn P.; Serreze, Mark C.

    2000-10-01

    At least four different modeling studies indicate that variability in snow cover over Asia may modulate atmospheric circulation over the North Pacific Ocean during winter. Here, satellite data on snow extent for east Asia for 1971-95 along with atmospheric fields from the National Centers for Environmental Prediction-National Center for Atmospheric Research reanalysis are used to examine whether the circulation signals seen in model results are actually observed in nature. Anomalies in snow extent over east Asia exhibit a distinct lack of persistence. This suggests that understanding the effects of east Asian snow cover is more germane for short- to medium-range weather forecasting applications than for problems on longer timescales. While it is impossible to attribute cause and effect in the empirical study, analyses of composite fields demonstrate relationships between snow cover extremes and atmospheric circulation downstream remarkably similar to those identified in model results. Positive snow cover extremes in midwinter are associated with a small decrease in air temperatures over the transient snow regions, a stronger east Asian jet, and negative geopotential height anomalies over the North Pacific Ocean. Opposing responses are observed for negative snow cover extremes. Diagnosis of storm track feedbacks shows that the action of high-frequency eddies does not reinforce circulation anomalies in positive snow cover extremes. However, in negative snow cover extremes, there are significant decreases in high-frequency eddy activity over the central North Pacific Ocean, and a corresponding decrease in the mean cyclonic effect of these eddies on the geopotential tendency, contributing to observed positive height anomalies over the North Pacific Ocean. The circulation signals over the North Pacific Ocean are much more pronounced in midwinter (January-February) than in the transitional seasons (November-December and March-April).

  9. Future Changes Projections of Atmospheric Circulation and Precipitation and Temperature Patterns Over South America in Austral Summer

    Science.gov (United States)

    Shimizu, M. H.; Cavalcanti, I. F.

    2012-12-01

    Atmospheric circulation is primarily driven by temperature gradients across the globe due to differential heating of Earth's surface which leads to a surplus of energy in the tropics and a deficit in the high latitudes. However, due to global warming, changes in atmospheric circulation are expected, which could result in modifications also in precipitation pattern. There are some evidences of changes in atmospheric circulation, such as the expansion of tropical belt and the poleward shift of large-scale atmospheric circulation systems, such as jet streams. These changes can be enhanced in a scenario with increasing greenhouse gases concentration. The objective of this study was to analyze future changes of atmospheric circulation and precipitation and temperature patterns in the austral summer over South America under Representative Pathway Concentration 8.5 (RCP 8.5) emission scenario. This evaluation was made according to model projections based on the coordinated climate change experiments defined by Coupled Model Intercomparison Project phase 5 (CMIP5). Historical simulations were used to evaluate model performance in reproduce main climatic features over South America in the Austral Summer. This analysis showed that some models perform better than others, with a wide range of difference between simulations and Global Precipitation Climatology Project (GPCP) and European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-Interim data sets. In general, the models captured the main features of Austral Summer such as the northwest-southeast precipitation band associated with the South Atlantic Convergence Zone (SACZ) and the anticyclonic circulation at high levels related to Bolivian High. The projections from different models pointed out in general to a reduction of precipitation, however the signal was not the same over all the continent and for all models. For example, Met Office's HadGEM2-ES projection indicated a reduction of precipitation in most of

  10. Analysing and combining atmospheric general circulation model simulations forced by prescribed SST. Northern extra tropical response

    Energy Technology Data Exchange (ETDEWEB)

    Moron, V. [Universite' de Provence, UFR des sciences geographiques et de l' amenagement, Aix-en-Provence (France); Navarra, A. [Istituto Nazionale di Geofisica e Vulcanologia, Bologna (Italy); Ward, M. N. [University of Oklahoma, Cooperative Institute for Mesoscale Meteorological Studies, Norman OK (United States); Foland, C. K. [Hadley Center for Climate Prediction and Research, Meteorological Office, Bracknell (United Kingdom); Friederichs, P. [Meteorologisches Institute des Universitaet Bonn, Bonn (Germany); Maynard, K.; Polcher, J. [Paris Universite' Pierre et Marie Curie, Paris (France). Centre Nationale de la Recherche Scientifique, Laboratoire de Meteorologie Dynamique, Paris

    2001-08-01

    The ECHAM 3.2 (T21), ECHAM 4 (T30) and LMD (version 6, grid-point resolution with 96 longitudes x 72 latitudes) atmospheric general circulation models were integrated through the period 1961 to 1993 forced with the same observed Sa 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 geo potential 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 sam 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 nd 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 tripote 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 heterogenous correlations for SLP relative to the Z500 ones). The time evolution of the SST-forced mode is moderately to strongly related to the ENSO/LNSO events but the spread amongst the ensemble of runs is not systematically related at all to

  11. 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

  12. A three-dimensional general circulation model with coupled chemistry for the middle atmosphere

    Science.gov (United States)

    Rasch, P. J.; Boville, B. A.; Brasseur, G. P.

    1995-05-01

    We document a new middle atmosphere general circulation model that includes ozone photochemistry. The dynamical model component is based on the NCAR middle atmosphere version of the Community Climate Model. The chemistry model component simulates the evolution of 24 chemically reactive gases. The horizontal resolution is approximately 3° in latitude and 6° in longitude. It includes 44 levels, with a maximum vertical grid spacing of about 2.5 km and a top level at around 75 km. The chemical model distinguishes between species where we judge transport to be critical and those for which it may be neglected. Nine longer-lived species (N2O, CH4, H2O, HNO3, N2O5, CO, ClONO2, HCl, and HOCl) and four chemical families (NOy, NOx, Ox and Clx) are advected. Concentrations of 15 species which are typically shorter-lived or are members of the chemical families are diagnosed using quasi-equilibrium assumptions ( O(1D), OH, Cl, O(3P), O3, HO2, NO2, ClO, NO, HNO4, NO3, N, OClO, Cl2O2, H2O2). Distributions for a number of other species are prescribed. Results are presented from a 2-year simulation, which include only gas phase photochemical reactions and in which the ozone distribution forecast from the chemistry module does not affect the radiative forcing of the dynamical fields. The calculated distributions of trace species and their seasonal evolution are often quite realistic, particularly in the northern hemisphere extratropics. Distributions of long-lived species such as N2O and CH4 correspond well to satellite observations. Some features, such as the double peak structure occurring during equinoxes, are not reproduced. The latitudinal variation and seasonal evolution of the ozone column abundance is quite realistic. The calculated vertical distribution of the ozone mixing ratio exhibits significant differences from measured values. The model underestimates significantly the ozone in the upper stratosphere (40 km) and in the extratropics, where the maximum values occur at

  13. The Effect of Surface Ice and Topography on the Atmospheric Circulation and Distribution of Nitrogen Ice on Pluto

    Science.gov (United States)

    Rafkin, Scot C. R.; Soto, Alejandro; Michaels, Timothy I.

    2016-10-01

    A newly developed general circulation model (GCM) for Pluto is used to investigate the impact of a heterogeneous distribution of nitrogen surface ice and large scale topography on Pluto's atmospheric circulation. The GCM is based on the GFDL Flexible Modeling System (FSM). Physics include a gray model radiative-conductive scheme, subsurface conduction, and a nitrogen volatile cycle. The radiative-conductive model takes into account the 2.3, 3.3 and 7.8 μm bands of CH4 and CO, including non-local thermodynamic equilibrium effects. including non-local thermodynamic equilibrium effects. The nitrogen volatile cycle is based on a vapor pressure equilibrium assumption between the atmosphere and surface. Prior to the arrival of the New Horizons spacecraft, the expectation was that the volatile ice distribution on the surface of Pluto would be strongly controlled by the latitudinal temperature gradient. If this were the case, then Pluto would have broad latitudinal bands of both ice covered surface and ice free surface, as dictated by the season. Further, the circulation, and the thus the transport of volatiles, was thought to be driven almost exclusively by sublimation and deposition flows associated with the volatile cycle. In contrast to expectations, images from New Horizon showed an extremely complex, heterogeneous distribution of surface ices draped over substantial and variable topography. To produce such an ice distribution, the atmospheric circulation and volatile transport must be more complex than previously envisioned. Simulations where topography, surface ice distributions, and volatile cycle physics are added individually and in various combinations are used to individually quantify the importance of the general circulation, topography, surface ice distributions, and condensation flows. It is shown that even regional patches of ice or large craters can have global impacts on the atmospheric circulation, the volatile cycle, and hence, the distribution of

  14. Spatiotemporal variability of the latest frosts in Korean Peninsula and causes of atmospheric circulation

    Science.gov (United States)

    Kim, Jin-Ah; Byun, Hi-Ryong

    2016-10-01

    The spatiotemporal distributions of latest frost dates (LFDs) on the Korean Peninsula and the atmospheric circulation patterns that resulted in the latest frosts (LFs) were investigated through the use of historical records and modern weather observation data. During the modern observation period since 1904, the most recent record of LF was April 28, 2013 at Daegwallyeong. On average, the LF occurred in Korea between March 17 (at Wando) and May 10 (at Daegwallyeong). Positive correlations were found between LFD and altitude and latitude. Additionally, inter- annual variation of LFD showed a trend of progressively earlier dates at 32 of the 48 stations at which data were available. The historic data set consists of the following: 39 records of frosts during the Three-States Period (57 BC-998 AD): 34 records during the Goryeo Dynasty (998-1391), among which the latest record was in July of the lunar calendar: and 498 during the Joseon Dynasty (1392-1928) with one LF dated August 31, 1417 on the solar calendar. Regarding LFD from The Annals of the Joseon Dynasty, April has 11 records, May has 55, June has 46, July has 21, and August has 5 LFD records. Various meteorological causes of the latest LF were then established. Firstly, a cold and humid north-easterly current that originates from high latitudes of more than 50°N and passes through the East Sea is considered one of the dominant causes of LF. Secondly, strong radiative cooling under clear skies is suspected as another important cause. Thirdly, a specific pressure pattern, called the `inverted-S contour' or `North High and South Low (NHSL) pattern' was found to be a favorable condition for LF. Finally the latest LF was not found to be related to monthly or longer-term cold climate, but are instead linked to the abrupt development of a strong ridge over inland Asia and the unusual southward movement of the tall polar cyclone over the North Pacific Ocean.

  15. 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.)

  16. An atmospheric general circulation model for Pluto with predictions for New Horizons temperature profiles

    Science.gov (United States)

    Zalucha, Angela M.

    2016-06-01

    Results are presented from a 3D Pluto general circulation model (GCM) that includes conductive heating and cooling, non-local thermodynamic equilibrium (non-LTE) heating by methane at 2.3 and 3.3 μm, non-LTE cooling by cooling by methane at 7.6 μm, and LTE CO rotational line cooling. The GCM also includes a treatment of the subsurface temperature and surface-atmosphere mass exchange. An initially 1 m thick layer of surface nitrogen frost was assumed such that it was large enough to act as a large heat sink (compared with the solar heating term) but small enough that the water ice subsurface properties were also significant. Structure was found in all three directions of the 3D wind field (with a maximum magnitude of the order of 10 m s-1 in the horizontal directions and 10-5 microbar s-1 in the vertical direction). Prograde jets were found at several altitudes. The direction of flow over the poles was found to very with altitude. Broad regions of up-welling and down-welling were also found. Predictions of vertical temperature profiles are provided for the Alice and Radio science Experiment instruments on New Horizons, while predictions of light curves are provided for ground-based stellar occultation observations. With this model methane concentrations of 0.2 per cent and 1.0 per cent and 8 and 24 microbar surface pressures are distinguishable. For ground-based stellar occultations, a detectable difference exists between light curves with the different methane concentrations, but not for different initial global mean surface pressures.

  17. Recent Trends in the Arctic Navigable Ice Season and Links to Atmospheric Circulation

    Science.gov (United States)

    Maslanik, J.; Drobot, S.

    2002-12-01

    One of the potential effects of Arctic climate warming is an increase in the navigable ice season, perhaps resulting in development of the Arctic as a major shipping route. The distance from western North American ports to Europe through the Northwest Passage (NWP) or the Northern Sea Route (NSR) is typically 20 to 60 percent shorter than travel through the Panama Canal, while travel between Europe and the Far East may be reduced by as much as three weeks compared to transport through the Suez Canal. An increase in the navigable ice season would also improve commercial opportunities within the Arctic region, such as mineral and oil exploration and tourism, which could potentially expand the economic base of Arctic residents and companies, but which would also have negative environmental impacts. Utilizing daily passive-microwave derived sea ice concentrations, trends and variability in the Arctic navigable ice season are examined from 1979 through 2001. Trend analyses suggest large increases in the length of the navigable ice season in the Kara and Barents seas, the Sea of Okhotsk, and the Beaufort Sea, with decreases in the length of the navigable ice season in the Bering Sea. Interannual variations in the navigable ice season largely are governed by fluctuations in low-frequency atmospheric circulation, although the specific annular modes affecting the length of the navigable ice season vary by region. In the Beaufort and East Siberian seas, variations in the North Atlantic Oscillation/Arctic Oscillation control the navigable ice season, while variations in the East Pacific anomaly play an important role in controlling the navigable ice season in the Kara and Barents seas. In Hudson Bay, the Canadian Arctic Archipelago, and Baffin Bay, interannual variations in the navigable ice season are strongly related to the Pacific Decadal Oscillation.

  18. 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.

  19. Integration of ice core, marine and terrestrial records: new insights into Holocene atmospheric circulation dynamics over NW Europe

    Science.gov (United States)

    Muschitiello, F.; Hammarlund, D.; Wohlfarth, B.

    2012-12-01

    We analyzed the oxygen (δ18O) and carbon (δ13C) isotope composition of lacustrine carbonates (Chara sp. and Bithynia tentaculata) from a lake sediment sequence (Lake Bjärsträsk) on the island of Gotland, southern Sweden. Our new isotopic records show a significant consistency with existing regional climatic reconstructions, as well as with paleorecords reflecting large-scale circulation dynamics. By comparing our data to ice core records from Greenland and to regional- and global-scale terrestrial and marine climate records, we explore potential couplings of Mid- and Late Holocene extreme summer climate conditions in northwestern Europe to orbital forcing and low-latitude atmospheric circulation dynamics. Specifically, we discuss the relationship between long-term changes in the position of the North Atlantic subtropical front and the frequency of summer blocking anticyclones over southern Sweden. Furthermore, we tentatively outline the spatial structure of predominant modes of atmospheric variability over the North Atlantic sector throughout the Holocene.

  20. The Atmospheric Circulation of the Hot Jupiter WASP-43b: Comparing Three-Dimensional Models to Spectrophotometric Data

    CERN Document Server

    Kataria, Tiffany; Fortney, Jonathan J; Stevenson, Kevin B; Line, Michael R; Kreidberg, Laura; Bean, Jacob L; Désert, Jean-Michel

    2014-01-01

    The hot Jupiter WASP-43b has now joined the ranks of transiting hot Jupiters HD 189733b and HD 209458b as an exoplanet with a large array of observational constraints on its atmospheric properties. Because WASP-43b receives a similar stellar flux as HD 209458b but has a rotation rate 4 times faster and a much higher gravity, studying WASP-43b serves as a test of the effect of rotation rate and gravity on the circulation when stellar irradiation is held approximately constant. Here we present 3D atmospheric circulation models of WASP-43b using the SPARC/MITgcm, a coupled radiation and circulation model, exploring the effects of composition, metallicity, and frictional drag. We find that the circulation regime of WASP-43b is not unlike other hot Jupiters, with equatorial superrotation that yields an eastward-shifted hotspot and large day-night temperature variations (~600 K at photospheric pressures). We then compare our model results to observations from Stevenson et al. which utilize HST/WFC3 to collect spect...

  1. Possible influence of atmospheric circulations on winter hazy pollution in Beijing-Tianjin-Hebei region, northern China

    Directory of Open Access Journals (Sweden)

    Z. Zhang

    2015-08-01

    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 hazy pollutions (indicated by the mean visibility and number of hazy days in Beijing-Tianjin-Hebei (BTH region during the period 1981 to 2015 and its relationship to the atmospheric circulations in middle-high latitude were analyzed in this study. The winter hazy 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. Both the visibility and number of hazy days can be estimated well by using the six indices and fitting and the cross-validation with leave-N-out method, respectively. The high level of the prediction statistics and the reasonable mechanism suggested that the winter hazy pollutions in BTH can be forecasted or estimated credibly based on the optimized atmospheric circulation indices. However, we also noted that the statistic estimation models would be largely influenced by the artificial control of a pollutant discharge. Thus it is helpful for government decision-making departments to take actions in advance in dealing with probably severe hazy pollutions in BTH indicated by the atmospheric circulation conditions.

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

    Science.gov (United States)

    Zhang, Z.; Zhang, X.; Gong, D.; Kim, S.-J.; Mao, R.; Zhao, X.

    2016-01-01

    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 ( pollution in BTH winter, and vice versa. The high level of the prediction statistics and the reasonable mechanism suggested that the winter haze pollution in BTH can be forecasted or estimated credibly based on the optimized atmospheric circulation indices. Thus it is helpful for government decision-making departments to take action in advance in dealing with probably severe haze pollution in BTH indicated by the atmospheric circulation conditions.

  3. Recent accelerating mass loss of southeast Tibetan glaciers and the relationship with changes in macroscale atmospheric circulations

    Science.gov (United States)

    Yang, Wei; Guo, Xiaofeng; Yao, Tandong; Zhu, Meilin; Wang, Yongjie

    2016-08-01

    The mass balance history (1980-2010) of a monsoon-dominated glacier in the southeast Tibetan Plateau is reconstructed using an energy balance model and later interpreted with regard to macroscale atmospheric variables. The results show that this glacier is characterized by significant interannual mass fluctuations over the past three decades, with a remarkably high mass loss during the recent period of 2003-2010. Analysis of the relationships between glacier mass balance and climatic variables shows that interannual temperature variability in the monsoonal season (June-September) is a primary driver of its mass balance fluctuations, but monsoonal precipitation tends to play an accentuated role for driving the observed glacier mass changes due to their covariation (concurrence of warm/dry and cold/wet climates) in the monsoon-influenced southeast Tibetan Plateau. Analysis of the atmospheric circulation pattern reveals that the predominance of anticyclonic/cyclonic circulations prevailing in the southeastern/northern Tibetan Plateau during 2003-2010 contributes to increased air temperature and decreased precipitation in the southeast Tibetan Plateau. Regionally contrasting atmospheric circulations explain the distinct mass changes between in the monsoon-influenced southeast Tibetan Plateau and in the north Tibetan Plateau/Tien Shan Mountains during 2003-2010. The macroscale climate change seems to be linked with the Europe-Asia teleconnection.

  4. Relationships of surface air temperature anomalies over Europe to persistence of atmospheric circulation patterns conducive to heat waves

    Directory of Open Access Journals (Sweden)

    J. Kyselý

    2008-04-01

    Full Text Available Heat waves are among natural hazards with the most severe consequences for human society, including pronounced mortality impacts in mid-latitudes. Recent studies have hypothesized that the enhanced persistence of atmospheric circulation may affect surface climatic extremes, mainly the frequency and severity of heat waves. In this paper we examine relationships between the persistence of the Hess-Brezowsky circulation types conducive to summer heat waves and air temperature anomalies at stations over most of the European continent. We also evaluate differences between temperature anomalies during late and early stages of warm circulation types in all seasons. Results show that more persistent circulation patterns tend to enhance the severity of heat waves and support more pronounced temperature anomalies. Recent sharply rising trends in positive temperature extremes over Europe may be related to the greater persistence of the circulation types, and if similar changes towards enhanced persistence affect other mid-latitudinal regions, analogous consequences and implications for temperature extremes may be expected.

  5. The 1958-2009 Greenland ice sheet surface melt and the mid-tropospheric atmospheric circulation

    NARCIS (Netherlands)

    Fettweis, X.; Mabille, G.; Erpicum, M.; Nicolay, S.; van den Broeke, M.R.

    2010-01-01

    In order to assess the impact of the mid-tropospheric circulation over the Greenland ice sheet (GrIS) on surface melt, as simulated by the regional climate model MAR, an automatic Circulation type classification (CTC) based on 500 hPa geopotential height from reanalyses is developed. General circula

  6. Five centuries of U.S. West Coast drought: Occurrence, spatial distribution, and associated atmospheric circulation patterns

    Science.gov (United States)

    Wise, Erika K.

    2016-05-01

    The U.S. West Coast drought commencing in 2012 developed in association with a large, persistent high-pressure ridge linked to internal atmospheric variability. This study places the occurrence, spatial patterns, and associated circulation features of West Coast drought into a paleoclimate context through a synoptic dendroclimatology approach linking atmospheric circulation to surface hydroclimate patterns. Spatial reconstructions of upper atmosphere pressure patterns and cool-season drought show that West Coast-wide drought, although relatively rare compared to north-south dipole drought, has occurred periodically since 1500 Common Era and is consistently associated with a strong ridge centered along the Pacific Northwest coast. Atmospheric blocking is also linked to north-dry dipole droughts, while south-dry and wider Western droughts indicate La Niña-type patterns. The transition latitude between the northern and southern sides of the western precipitation dipole, important for California hydroclimate patterns, has had frequent year-to-year fluctuations but remained centered on 40°N over the past five centuries.

  7. On the Linkage between the Extreme Drought and Pluvial Patterns in China and the Large-Scale Atmospheric Circulation

    Directory of Open Access Journals (Sweden)

    Zengxin Zhang

    2016-01-01

    Full Text Available China is a nation that is affected by a multitude of natural disasters, including droughts and floods. In this paper, the variations of extreme drought and pluvial patterns and their relations to the large-scale atmospheric circulation have been analyzed based on monthly precipitation data from 483 stations during the period 1958–2010 in China. The results show the following: (1 the extreme drought and pluvial events in China increase significantly during that period. During 1959–1966 timeframe, more droughts occur in South China and more pluvial events are found in North China (DSC-PNC pattern; as for the period 1997–2003 (PSC-DNC pattern, the situation is the opposite. (2 There are good relationships among the extreme drought and pluvial events and the Western Pacific Subtropical High, meridional atmospheric moisture flux, atmospheric moisture content, and summer precipitation. (3 A cyclone atmospheric circulation anomaly occurs in North China, followed by an obvious negative height anomaly and a southern wind anomaly at 850 hPa and 500 hPa for the DSC-PNC pattern during the summer, and a massive ascending airflow from South China extends to North China at ~50∘N. As for the PSC-DNC pattern, the situation contrasts sharply with the DSC-PNC pattern.

  8. 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.

  9. Analysing and combining atmospheric general circulation model simulations forced by prescribed SST. Tropical response

    Energy Technology Data Exchange (ETDEWEB)

    Moron, V. [Universite' de Provence, UFR des sciences geographiques et de l' amenagement, Aix-en-Provence (France); Navarra, A. [Istituto Nazionale di Geofisica e Vulcanologia, Bologna (Italy); Ward, M. N. [University of Oklahoma, Cooperative Institute for Mesoscale Meteorological Studies, Norman OK (United States); Foland, C. K. [Hadley Center for Climate Prediction and Research, Meteorological Office, Bracknell (United Kingdom); Friederichs, P. [Meteorologisches Institute des Universitaet Bonn, Bonn (Germany); Maynard, K.; Polcher, J. [Paris Universite' Pierre et Marie Curie, Paris (France). Centre Nationale de la Recherche Scientifique, Laboratoire de Meteorologie Dynamique, Paris

    2001-08-01

    The ECHAM 3.2 (T21), ECHAM (T30) and LMD (version 6, grid-point resolution with 96 longitudes x 72 latitudes) atmospheric general circulation models were integrated through the period 1961 to 1993 forces 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 large-scale tropical inter-annual variability is analysed to give a picture of a skill of each model and of some sort of combination of the three models. To analyse the similarity of model response averaged over the same key regions, several widely-used indices are calculated: Southern Oscillation Index (SOI), large-scale wind shear indices of the boreal summer monsoon in Asia and West Africa and rainfall indices for NE Brazil, Sahel and India. Even for the indices where internal noise is large, some years are consistent amongst all the runs, suggesting inter-annual variability of the strength of SST forcing. Averaging the ensemble mean of the three models (the super-ensemble mean) yields improved skill. When each run is weighted according to its skill, taking three runs from different models instead of three runs of the same model improves the mean skill. There is also some indication that one run of a given model could be better than another, suggesting that persistent anomalies could change its sensitivity to SST. The index approach lacks flexibility to assess whether a model's response to SST has been geographically displaced. It can focus on the first mode in the global tropics, found through singular value decomposition analysis, which is clearly related to El Nino/Southern Oscillation (ENSO) in all seasons. The Observed-Model and Model-Model analyses lead to almost the same patterns, suggesting that the dominant pattern of model response is also the most skilful mode. Seasonal modulation of both skill and spatial patterns (both model and observed) clearly exists with highest skill

  10. Atmospheric circulation controls on the inter-annual variability in precipitation isotope ratio in Japan

    Directory of Open Access Journals (Sweden)

    N. Kurita

    2014-10-01

    in winter. Therefore, isotope-based proxy records archived in central Japan may enable us to examine past atmospheric circulation changes in East Asia in response to climate variability.

  11. A Monthly Atmospheric Circulation Classification and Its Relationship with Climate in Harbin

    Institute of Scientific and Technical Information of China (English)

    JIA Liwei; LI Weijing; CHEN Deliang; AN Xiaocun

    2006-01-01

    In this study, the classification scheme developed by Jenkinson and Collison (1977) based on a typing scheme of Lamb (1950) is applied to obtain circulation types from the mean sea-level pressure on a monthly basis. Monthly mean sea-level pressure data from 1951 to 2002 are used to derive six circulation indices and to provide a circulation catalogue with 27 circulation types. Five major types (N, NW, C, CSW, and SW)which occurred most frequently are analyzed to reveal their relationships with the temperature of Harbin on various time scales. Stepwise multiple regression is used to reconstruct temperature anomaly. The monthly mean rainfall of all types occurring and the composite maps of three major types (C, CSW, and SW) relevant to Harbin's precipitation are studied. In this study, the classification scheme developed by Jenkinson and Collison (1977) based on a typing scheme of Lamb (1950) is applied to obtain circulation types from the mean sea-level pressure on a monthly basis. Monthly mean sea-level pressure data from 1951 to 2002 are used to derive six circulation indices and to provide a circulation catalogue with 27 circulation types. Five major types (N, NW, C, CSW, and SW)which occurred most frequently are analyzed to reveal their relationships with the temperature of Harbin on various time scales. Stepwise multiple regression is used to reconstruct temperature anomaly. The monthly mean rainfall of all types occurring and the composite maps of three major types (C, CSW, and SW) relevant to Harbin's precipitation are studied.

  12. A 290-a record of atmospheric circulation over the North Pacific from a Mt. Logan ice core, Yukon Territory

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Calibrations between sodium (Na+) concentrations from a Mt. Logan ice core and sea level pressure (SLP) series show that Na+ concentrations are closely correlated with the autumn-time (SeptemberOctober-November) Aleutian low (AleuLow). A deepening of the AleuLow strengthens the transport of sea-salt aerosols from the North Pacific to the Mt. Logan region. The Mt. Logan Na+ record is used to develop a 292 a (1688~1979) reconstruction of the AleuLow revealing a dramatic intensification of atmospheric circulation over the North Pacific region since the 20th century. Mean SLP of the AleuLow was about 1 hPa lower during the 20th century than during prior periods. The strongest deepening of the AleuLow appeared in the 1950s. Significant correlations are also found between the Mt. Logan AleuLow proxy series and the Pacific decadal oscillation (PDO) and Pacific circulation (PC) index during the 20th century. Evolutionary spectral analysis of the proxy record shows significant periodicities from 15 to 30 a consistent with PDO fluctuations and the bidecadal oscillation of North Pacific atmosphere-ocean circulation. A period of 11 a in the AleuLow record may be associated with the Schwabe 11-a cycle of sunspot activity. Additional longer ice core records from this region will aid in the efforts to further understand the climatic change over the North Pacific region.

  13. A Distinct Change in Atmospheric Circulation on the Central Tibetan Plateau at 16,800 Years Ago

    Science.gov (United States)

    Zhu, L.; Lü, X.; Wang, J.; Peng, P.; Wang, Y.; Li, Q.; Kasper, T.; Daut, G.; Haberzettl, T.; Frenzel, P.; Schwalb, A.; Maeusbacher, R.

    2014-12-01

    The Tibetan Plateau (TP) has experienced similar environmental and climatic events as the Realm of North Atlantic Ocean (NA) since the Last Glacial Maximum (LGM). However, previous studies have not discussed in detail whether the influence is transported through the westerly crossing the Eurasian continent or by the thermohaline circulation influencing the Indian Summer Monsoon (ISM). Using observations in the transition zone between the westerly and the ISM on the TP, pollen assemblage variations from a lacustrine sediment record indicate changes in circulations patterns. Before 16.8 ka BP, climate on the TP was controlled by the southward westerly and the dipole-shaped tropical Atlantic sea surface temperature (SST) and rainfall anomaly due to sub-polar ice sheet expanding in the NA areas. After 16.8 ka BP, the Atlantic meridional overturning circulation (AMOC) exerted more influence to the Indian Ocean currents and then to the ISM, which was the dominant atmospheric circulation on the TP areas during the whole period.

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

    Science.gov (United States)

    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. PMID:28178351

  15. Model evidence for low-level cloud feedback driving persistent changes in atmospheric circulation and regional hydroclimate

    Science.gov (United States)

    Burgman, Robert J.; Kirtman, Ben P.; Clement, Amy C.; Vazquez, Heather

    2017-01-01

    Recent studies suggest that low clouds in the Pacific play an important role in the observed decadal climate variability and future climate change. In this study, we implement a novel modeling experiment designed to isolate how interactions between local and remote feedbacks associated with low cloud, SSTs, and the large-scale circulation play a significant role in the observed persistence of tropical Pacific SST and associated North American drought. The modeling approach involves the incorporation of observed patterns of satellite-derived shortwave cloud radiative effect (SWCRE) into the coupled model framework and is ideally suited for examining the role of local and large-scale coupled feedbacks and ocean heat transport in Pacific decadal variability. We show that changes in SWCRE forcing in eastern subtropical Pacific alone reproduces much of the observed changes in SST and atmospheric circulation over the past 16 years, including the observed changes in precipitation over much of the Western Hemisphere.

  16. Atmospheric circulation of hot Jupiters: Coupled radiative-dynamical general circulation model simulations of HD 189733b and HD 209458b

    CERN Document Server

    Showman, Adam P; Lian, Yuan; Marley, Mark S; Freedman, Richard S; Knutson, Heather A; Charbonneau, David

    2008-01-01

    We present global, three-dimensional numerical simulations of HD 189733b and HD 209458b that couple the atmospheric dynamics to a realistic representation of non-gray cloud-free radiative transfer. The model, which we call the Substellar and Planetary Atmospheric Radiation and Circulation (SPARC) model, adopts the MITgcm for the dynamics and uses the radiative model of McKay, Marley, Fortney, and collaborators for the radiation. Like earlier work with simplified forcing, our simulations develop a broad eastward equatorial jet, mean westward flow at higher latitudes, and substantial flow over the poles at low pressure. For HD 189733b, our simulations without TiO and VO opacity can explain the broad features of the observed 8 and 24-micron light curves, including the modest day-night flux variation and the fact that the planet/star flux ratio peaks before the secondary eclipse. Our simulations also provide reasonable matches to the Spitzer secondary-eclipse depths at 4.5, 5.8, 8, 16, and 24 microns and the grou...

  17. THE ATMOSPHERIC CIRCULATION OF THE HOT JUPITER WASP-43b: COMPARING THREE-DIMENSIONAL MODELS TO SPECTROPHOTOMETRIC DATA

    Energy Technology Data Exchange (ETDEWEB)

    Kataria, Tiffany; Showman, Adam P. [Department of Planetary Sciences and Lunar and Planetary Laboratory, The University of Arizona, Tucson, AZ 85721 (United States); Fortney, Jonathan J.; Line, Michael R. [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Stevenson, Kevin B.; Kreidberg, Laura; Bean, Jacob L. [Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL 60637 (United States); Désert, Jean-Michel, E-mail: tkataria@astro.ex.ac.uk [CASA, Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, CO 80309 (United States)

    2015-03-10

    The hot Jupiter WASP-43b (2 M{sub J}, 1 R{sub J}, T {sub orb} = 19.5 hr) has now joined the ranks of transiting hot Jupiters HD 189733b and HD 209458b as an exoplanet with a large array of observational constraints. Because WASP-43b receives a similar stellar flux as HD 209458b but has a rotation rate four times faster and a higher gravity, studying WASP-43b probes the effect of rotation rate and gravity on the circulation when stellar irradiation is held approximately constant. Here we present three-dimensional (3D) atmospheric circulation models of WASP-43b, exploring the effects of composition, metallicity, and frictional drag. We find that the circulation regime of WASP-43b is not unlike other hot Jupiters, with equatorial superrotation that yields an eastward-shifted hotspot and large day-night temperature variations (∼600 K at photospheric pressures). We then compare our model results to Hubble Space Telescope (HST)/WFC3 spectrophotometric phase curve measurements of WASP-43b from 1.12 to 1.65 μm. Our results show the 5× solar model light curve provides a good match to the data, with a peak flux phase offset and planet/star flux ratio that is similar to observations; however, the model nightside appears to be brighter. Nevertheless, our 5× solar model provides an excellent match to the WFC3 dayside emission spectrum. This is a major success, as the result is a natural outcome of the 3D dynamics with no model tuning. These results demonstrate that 3D circulation models can help interpret exoplanet atmospheric observations, even at high resolution, and highlight the potential for future observations with HST, James Webb Space Telescope, and other next-generation telescopes.

  18. Impacts of SST anomalies on the North Atlantic atmospheric circulation: a case study for the northern winter 1995/1996

    Energy Technology Data Exchange (ETDEWEB)

    Losada, T.; Rodriguez-Fonseca, B. [Universidad Complutense de Madrid, Departmento de Geofisica y Meteorologia, Madrid (Spain); Mechoso, C.R.; Ma, H.Y. [University of California Los Angeles, Department of Atmospheric and Oceanic Sciences, Los Angeles, CA (United States)

    2007-12-15

    The present paper selects the northern winter of December 1995-February 1996 for a case study on the impact of sea surface temperature (SST) anomalies on the atmospheric circulation over the North Atlantic and Western Europe. In the Atlantic, the selected winter was characterized by positive SST anomalies over the northern subtropics and east of Newfoundland, and negative anomalies along the US coast. A weak La Nina event developed in the Pacific. The North Atlantic Oscillation (NAO) index was low, precipitation over the Iberian Peninsula and northern Africa was anomalously high, and precipitation over northern Europe was anomalously low. The method of study consists of assessing the sensitivity of ensemble simulations by the UCLA atmospheric general circulation model (UCLA AGCM) to SST anomalies from the observation, which are prescribed either in the World Oceans, the Atlantic Ocean only, or the subtropical North Atlantic only. The results obtained are compared with a control run that uses global, time-varying climatological SST. The ensemble simulations with global and Atlantic-only SST anomalies both produce results that resemble the observations over the North Atlantic and Western Europe. It is suggested that the anomalous behavior of the atmosphere in the selected winter over those regions, therefore, was primarily determined by conditions within the Atlantic basin. The simulated fields in the tropical North Atlantic show anomalous upward motion and lower (upper) level convergence (divergence) in the atmosphere overlying the positive SST anomalies. Consistently, the subtropical jet intensifies and its core moves equatorward, and precipitation increases over northern Africa and southern Europe. The results also suggest that the SST anomalies in the tropical North Atlantic only do not suffice to produce the atmospheric anomalies observed in the basin during the selected winter. The extratropical SST anomalies would provide a key contribution through increased

  19. Description of the atmospheric circulation in the boundary layer over a tropical island: Case study of Guadeloupe Archipelago

    Science.gov (United States)

    Plocoste, Thomas; Dorville, Jean-François; Jacoby-Koaly, Sandra; Roussas, André

    2016-04-01

    Over past two decades the use of atmospheric sounding methods as Sodars, Lidar equipped drones increased sharply. Compare to weather balloon, these modern methods allow measure of profile at constant heights during long period. There are few studies using this type of equipment in tropical climates and lesser on small island. Wind regime on island of diameter less than 50 km are mostly considered as oceanic. Many author consider that thermal effect are negligible in land. But recent observations and simulations show importance of the thermal circulation at small- and meso- scales particularly in atmospheric pollution process. Up to 2009 no wind profile data were available continuously to study atmospheric circulation in Guadeloupe Archipelago (GA) which is one of the islands of the Lesser Antilles Arc. In first approximation wind was evaluated based on measures done at the most upwind island of the GA for many application as wind power and atmospheric pollution. From 2009 to 2012 a measurement campaign of the Atmospheric Boundary Layer (ABL) have been performed by the University of Antilles (UA) in GA. To assess effects of dynamic of ABL on air quality in sub urban area, particularly during the sunset and sunrise, UA monitored two sites with a weather station and a doppler sodar (REMTECH PAO). Both sites are close to the sea with one in a coastal area and the other in an open landfill surrounded by densely populated building and a mangrove swamp. Thermal and chemical measurements with a portable mass spectrometer were made in the vicinity of the landfill and showed the existence of urban heat islands. This study presents the first Doppler Sodar long measurements campaign in GA. Statistical analysis of the three year of doppler sodar data (i.e. wind components and its fluctuations) allow to identified and characterized the complex circulations on the two sites in the ABL between 25 and 500m above the sea level. Orographic and thermal effects due to urban area were

  20. 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

  1. Abrupt Late Holocene Shift in Atmospheric Circulation Recorded by Mineral Dust in the Siple Dome Ice Core, Antarctica

    Science.gov (United States)

    Koffman, B. G.; Goldstein, S. L.; Kaplan, M. R.; Winckler, G.; Bory, A. J. M.; Biscaye, P.

    2015-12-01

    Atmospheric dust directly influences Earth's climate by altering the radiative balance and by depositing micronutrients in the surface ocean, affecting global biogeochemical cycling. In addition, mineral dust particles provide observational evidence constraining past atmospheric circulation patterns. Because dust can originate from both local and distant terrestrial sources, knowledge of dust provenance can substantially inform our understanding of past climate history, atmospheric transport pathways, and differences in aerosol characteristics between glacial and interglacial climate states. Dust provenance information from Antarctic ice cores has until now been limited to sites in East Antarctica. Here we present some of the first provenance data from West Antarctica. We use Sr-Nd isotopes to characterize dust extracted from late Holocene ice (~1000-1800 C.E.) from the Siple Dome ice core. The data form a tight array in Sr-Nd isotope space, with 87Sr/86Sr ranging between ~0.7087 and 0.7102, and ɛNd ranging between ~ -7 and -16. This combination is unique for Antarctica, with low Nd and low Sr isotope ratios compared to high-elevation East Antarctic sites, requiring a dust source from ancient (Archean to early Proterozoic) and unweathered continental crust, which mixes with young volcanic material. Both components are likely sourced from Antarctica. We also observe significant, systematic variability in Sr and Nd isotopic signatures through time, reflecting changes in the mixing ratio of these sources, and hypothesize that these changes are driven by shifts in circulation patterns. A large change occurs over about 10 years at ca. 1125 C.E. (ΔɛNd = +3 and Δ87Sr/86Sr = -0.0014). This shift coincides with changes in climate proxies in Southern Hemisphere paleoclimate records reflecting variability in the Westerlies. We therefore interpret the shift in dust provenance at Siple Dome to be related to larger-scale circulation changes. In general, the observed shifts

  2. Ideas and perspectives: Southwestern tropical Atlantic coral growth response to atmospheric circulation changes induced by ozone depletion in Antarctica

    Science.gov (United States)

    Evangelista, Heitor; Wainer, Ilana; Sifeddine, Abdelfettah; Corrège, Thierry; Cordeiro, Renato C.; Lamounier, Saulo; Godiva, Daniely; Shen, Chuan-Chou; Le Cornec, Florence; Turcq, Bruno; Lazareth, Claire E.; Hu, Ching-Yi

    2016-04-01

    Recent Southern Hemisphere (SH) atmospheric circulation, predominantly driven by stratospheric ozone depletion over Antarctica, has caused changes in climate across the extratropics. Here, we present evidence that the Brazilian coast (southwestern Atlantic) may have been impacted from both wind and sea-surface temperature changes derived from this process. Skeleton analysis of massive coral species living in shallow waters off Brazil are very sensitive to air-sea interactions, and seem to record this impact. Growth rates of Brazilian corals show a trend reversal that fits the ozone depletion evolution, confirming that ozone impacts are far reaching and potentially affect coastal ecosystems in tropical environments.

  3. A global view of gravity waves in the Martian atmosphere inferred from a high-resolution general circulation model

    CERN Document Server

    Kuroda, Takeshi; Yiğit, Erdal; Hartogh, Paul

    2015-01-01

    Global characteristics of the small-scale gravity wave (GW) field in the Martian atmosphere obtained from a high-resolution general circulation model (GCM) are presented for the first time. 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. 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 while 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 body forces of tens of m~s$^{-1}$~sol$^{-1}$, which tend to close the simulated jets. The results represent a realistic surrogate for missing observations, which can be used for constraining GW parameterizations and validating GCM si...

  4. Impacts of Multi-Scale Solar Activity on Climate.Part Ⅰ:Atmospheric Circulation Patterns and Climate Extremes

    Institute of Scientific and Technical Information of China (English)

    Hengyi WENG

    2012-01-01

    The impacts of solar activity on climate are explored in this two-part study.Based on the principles of atmospheric dynamics,Part Ⅰ propose an amplifying mechanism of solar impacts on winter climate extremes through changing the atmospheric circulation patterns.This mechanism is supported by data analysis of the sunspot number up to the predicted Solar Cycle 24,the historical surface temperature data,and atmospheric variables of NCEP/NCAR Reanalysis up to the February 2011 for the Northern Hemisphere winters.For low solar activity,the thermal contrast between the low- and high-latitudes is enhanced,so as the mid-latitude baroclinic ultra-long wave activity.The land-ocean thermal contrast is also enhanced,which amplifies the topographic waves.The enhanced mid-latitude waves in turn enhance the meridional heat transport from the low to high latitudes,making the atmospheric “heat engine” more efficient than normal. The jets shift southward and the polar vortex is weakened.The Northern Annular Mode (NAM) index tends to be negative.The mid-latitude surface exhibits large-scale convergence and updrafts,which favor extreme weather/climate events to occur.The thermally driven Siberian high is enhanced,which enhances the East Asian winter monsoon (EAWM).For high solar activity,the mid-latitude circulation patterns are less wavy with less meridional transport.The NAM tends to be positive,and the Siberian high and the EAWM tend to be weaker than normal.Thus the extreme weather/climate events for high solar activity occur in different regions with different severity from those for low solar activity.The solar influence on the midto high-latitude surface temperature and circulations can stand out after renoving the influence from the El Ni(n)o-Southern Oscillation.The atmospheric amplifying mechanism indicates that the solar impacts on climate should not be simply estimated by the magnitude of the change in the solar radiation over solar cycles when it is compared with

  5. Sensitivity of boreal-summer circulation and precipitation to atmospheric aerosols in selected regions – Part 2: The Americas

    Directory of Open Access Journals (Sweden)

    G. Walker

    2009-10-01

    Full Text Available Aerosol perturbations over selected land regions are imposed in Version-4 of the Goddard Earth Observing System (GEOS-4 general circulation model (GCM to assess the influence of increasing aerosol concentrations on regional circulation patterns and precipitation in four selected regions: India, Africa, and North and South America. Part 1 of this paper addresses the responses to aerosol perturbations in India and Africa. This paper presents the same for aerosol perturbations over the Americas. GEOS-4 is forced with prescribed aerosols based on climatological data, which interact with clouds using a prognostic scheme for cloud microphysics including aerosol nucleation of water and ice cloud hydrometeors. In clear-sky conditions the aerosols interact with radiation. Thus the model includes comprehensive physics describing the aerosol direct and indirect effects on climate (hereafter ADE and AIE respectively. Each simulation is started from analyzed initial conditions for 1 May and was integrated through June-July-August of each of the six years: 1982–1987 to provide a 6-ensemble set. Results are presented for the difference between simulations with double the climatological aerosol concentration and one-half the climatological aerosol concentration for three experiments: two where the ADE and AIE are applied separately and one in which both the ADE and AIE are applied. The ADE and AIE both yield reductions in net radiation at the top of the atmosphere and surface while the direct absorption of shortwave radiation contributes a net radiative heating in the atmosphere. A large net heating of the atmosphere is also apparent over the subtropical North Atlantic Ocean that is attributable to the large aerosol perturbation imposed over Africa. This atmospheric warming and the depression of the surface pressure over North America contribute to a northward shift of the inter-Tropical Convergence Zone over northern South America, an increase in

  6. 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.

  7. 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 simu

  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. Role of the Atmospheric General Circulation on the Temporal Variability of the Aerosol Distribution over Dakar (Senegal)

    Science.gov (United States)

    Senghor, Habib; Machu, Eric; Hourdin, Frederic; Thierno Gaye, Amadou; Gueye, Moussa; Simina Drame, Mamadou

    2016-04-01

    The natural or anthropogenic aerosols play an important role on the climate system and the human health through their optical and physical properties. To evaluate the potential impacts of these aerosols, it is necessary to better understand their temporal variability in relation with the atmospheric ciculation. Some previous case studies have pointed out the influence of the sea-breeze circulation on the vertical distribution of the aerosols along the Western African coast. In the present work, Lidar (Ceilometer CL31; located at Dakar) data are used for the period 2012-2014 together with Level-3 data from CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) between 2007 and 2014 for studying the seasonal cycle of the vertical distribution of aerosols over Dakar (17.5°W, 14.74°N). Both instruments show strong seasonal variability with a maximum of aerosol occurrence in May over Dakar. The CL31 shows a crucial impact of sea-breeze circulation on the diurnal cycle of the Mixed Atmospheric Boundary Layer and a strong dust signal in spring in the nocturnal low-level jet (LLJ) located between 500 and 1000 m altitudes over Dakar.

  10. Seasonal variability of diurnal temperature range in Egypt with links to atmospheric circulations and sea surface temperature

    Science.gov (United States)

    El Kenawy, A.; Lopez Moreno, J. I.; Vicente-Serrano, S.

    2010-09-01

    The diurnal temperature range (DTR) is an important climate-change variable. Seasonal and annual variability of DTR in Egypt was investigated based on a monthly dataset of 40 observatories distributing across the country. The trends were calculated using the Rho spearman rank test at the 95 % level of significance. The trends at the independent individual scale were compared with a regional series created for the whole country following the Thiessen polygon approach. A cross-tabulation analysis was performed between the trends of the DTR and the trends of maximum and minimum temperatures to account for directional causes of variability of the DTR at seasonal and annual scales. The physical processes controlling the DTR variability were also assessed in terms of large atmospheric circulations representing in the indices of the North Atlantic Oscillation (NAO), the East Atlantic (EA) pattern, El Niño Southern Oscillation (ENSO) index and the EAWR (East Atlantic/West Russia) Pattern. Also, the variability of the DTR was linked with anomaly of Sea Surface Temperature (SST). A cooling trend was observed in Egypt with strong behavior in winter and summer rather than fall and spring. The upwarding trend of the mean minimum temperature was mainly responsible for variability of the DTR rather than the mean maximum temperature. Also, the EA and the EAWR indices were the main indices accounted for most of variation in the DTR in Egypt, particularly in summer. Key words: trend analysis, temperature variability, Diurnal temperature range, atmospheric circulation, sea surface temperature, Egypt.

  11. Anomalous mid-twentieth century atmospheric circulation change over the South Atlantic compared to the last 6000 years

    Science.gov (United States)

    Turney, Chris S. M.; Jones, Richard T.; Lister, David; Jones, Phil; Williams, Alan N.; Hogg, Alan; Thomas, Zoë A.; Compo, Gilbert P.; Yin, Xungang; Fogwill, Christopher J.; Palmer, Jonathan; Colwell, Steve; Allan, Rob; Visbeck, Martin

    2016-06-01

    Determining the timing and impact of anthropogenic climate change in data-sparse regions is a considerable challenge. Arguably, nowhere is this more difficult than the Antarctic Peninsula and the subantarctic South Atlantic where observational records are relatively short but where high rates of warming have been experienced since records began. Here we interrogate recently developed monthly-resolved observational datasets from the Falkland Islands and South Georgia, and extend the records back using climate-sensitive peat growth over the past 6000 years. Investigating the subantarctic climate data with ERA-Interim and Twentieth Century Reanalysis, we find that a stepped increase in precipitation across the 1940s is related to a change in synoptic atmospheric circulation: a westward migration of quasi-permanent positive pressure anomalies in the South Atlantic has brought the subantarctic islands under the increased influence of meridional airflow associated with the Amundsen Sea Low. Analysis of three comprehensively multi-dated (using 14C and 137Cs) peat sequences across the two islands demonstrates unprecedented growth rates since the mid-twentieth century relative to the last 6000 years. Comparison to observational and reconstructed sea surface temperatures suggests this change is linked to a warming tropical Pacific Ocean. Our results imply ‘modern’ South Atlantic atmospheric circulation has not been under this configuration for millennia.

  12. Association between atmospheric circulation patterns and firn-ice core records from the Inilchek glacierized area, central Tien Shan, Asia

    Science.gov (United States)

    Aizen, V.B.; Aizen, E.M.; Melack, J.M.; Kreutz, K.J.; Cecil, L.D.

    2004-01-01

    Glacioclimatological research in the central Tien Shan was performed in the summers of 1998 and 1999 on the South Inilchek Glacier at 5100-5460 m. A 14.36 m firn-ice core and snow samples were collected and used for stratigraphic, isotopic, and chemical analyses. The firn-ice core and snow records were related to snow pit measurements at an event scale and to meteorological data and synoptic indices of atmospheric circulation at annual and seasonal scales. Linear relationships between the seasonal air temperature and seasonal isotopic composition in accumulated precipitation were established. Changes in the ??18O air temperature relationship, in major ion concentration and in the ratios between chemical species, were used to identify different sources of moisture and investigate changes in atmospheric circulation patterns. Precipitation over the central Tien Shan is characterized by the lowest ionic content among the Tien Shan glaciers and indicates its mainly marine origin. In seasons of minimum precipitation, autumn and winter, water vapor was derived from the and and semiarid regions in central Eurasia and contributed annual maximal solute content to snow accumulation in Tien Shan. The lowest content of major ions was observed in spring and summer layers, which represent maximum seasonal accumulation when moisture originates over the Atlantic Ocean and Mediterranean and Black Seas. Copyright 2004 by the American Geophysical Union.

  13. Acceleration technique for Milankovitch type forcing in a coupled atmosphere-ocean circulation model: method and application for the Holocene

    Energy Technology Data Exchange (ETDEWEB)

    Lorenz, Stephan J. [Modelle und Daten, Max-Planck-Institut fuer Meteorologie, Hamburg (Germany); Lohmann, Gerrit [Universitaet Bremen, Fachbereich Geowissenschaften und DFG Forschungszentrum Ozeanraender, Postfach 330440, Bremen (Germany)

    2004-12-01

    A method is introduced which allows the calculation of long-term climate trends within the framework of a coupled atmosphere-ocean circulation model. The change in the seasonal cycle of incident solar radiation induced by varying orbital parameters has been accelerated by factors of 10 and 100 in order to allow transient simulations over the period from the mid-Holocene until today, covering the last 7,000 years. In contrast to conventional time-slice experiments, this approach is not restricted to equilibrium simulations and is capable to utilise all available data for validation. We find that opposing Holocene climate trends in tropics and extra-tropics are a robust feature in our experiments. Results from the transient simulations of the mid-Holocene climate at 6,000 years before present show considerable differences to atmosphere-alone model simulations, in particular at high latitudes, attributed to atmosphere-ocean-sea ice effects. The simulations were extended for the time period 1800-2000 AD, where, in contrast to the Holocene climate, increased concentrations of greenhouse gases in the atmosphere provide for the strongest driving mechanism. The experiments reveal that a Northern Hemisphere cooling trend over the Holocene is completely cancelled by the warming trend during the last century, which brings the recent global warming into a long-term context. (orig.)

  14. Use of coupled ozone fields in a 3-D circulation model of the middle atmosphere

    Directory of Open Access Journals (Sweden)

    T. Reddmann

    Full Text Available With a detailed chemistry scheme for the middle atmosphere up to 70 km which has been added to the 3-D Karlsruhe simulation model of the middle atmosphere (KASIMA, the effects of coupling chemistry and dynamics through ozone are studied for the middle atmosphere. An uncoupled version using an ozone climatology for determining heating rates and a coupled version using on-line ozone are compared in a 10-month integration with meteorological analyses for the winter 1992/93 as the lower boundary condition. Both versions simulate the meteorological situation satisfactorily, but exhibit a too cold lower stratosphere. The on-line ozone differs from the climatological data between 20 and 40 km by exhibiting too high ozone values, whereas in the lower mesosphere the ozone values are too low. The coupled model version is stable and differs only above 40 km significantly from the uncoupled version. Direct heating effects are identified to cause most of the differences. The well-known negative correlation between temperature and ozone is reproduced in the model. As a result, the coupled version slightly approaches the climatological ozone field. Further feedback effects are studied by using the on-line ozone field as a basis for an artificial climatology. For non-disturbed ozone conditions realistic monthly and zonally averaged ozone data are sufficient to determine the heating rates for modelling the middle atmosphere.

    Key words. Atmospheric composition and structure (middle atmosphere · composition and chemistry · Meteorology and atmospheric dynamics (middle atmosphere dynamics.

  15. 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.

  16. 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

  17. Large-scale atmospheric circulation and local particulate matter concentrations in Bavaria - from current observations to future projections

    Science.gov (United States)

    Beck, Christoph; Weitnauer, Claudia; Brosy, Caroline; Hald, Cornelius; Lochbihler, Kai; Siegmund, Stefan; Jacobeit, Jucundus

    2016-04-01

    Particulate matter with an aerodynamic diameter of 10 μm or less (PM10) may have distinct adverse effects on human health. Spatial and temporal variations in PM10 concentrations reflect local emission rates, but are as well influenced by the local and synoptic-scale atmospheric conditions. Against this background, it can be furthermore argued that potential future climate change and associated variations in large-scale atmospheric circulation and local meteorological parameters will probably provoke corresponding changes in future PM10 concentration levels. The DFG-funded research project „Particulate matter and climate change in Bavaria" aimed at establishing quantitative relationships between daily and monthly PM10 indices at different Bavarian urban stations and the corresponding large-scale atmospheric circulation as well as local meteorological conditions. To this end, several statistical downscaling approaches have been developed for the period 1980 to 2011. PM10 data from 19 stations from the air quality monitoring network (LÜB) of the Bavarian Environmental Agency (LfU) have been utilized as predictands. Large-scale atmospheric gridded data from the NCEP/NCAR reanalysis data base and local meteorological observational data provided by the German Meteorological Service (DWD) served as predictors. The downscaling approaches encompass the synoptic downscaling of daily PM10 concentrations and several multivariate statistical models for the estimation of daily and monthly PM10, i.e.monthly mean and number of days exceeding a certain PM10 concentration threshold. Both techniques utilize objective circulation type classifications, which have been optimized with respect to their synoptic skill for the target variable PM10. All downscaling approaches have been evaluated via cross validation using varying subintervals of the 1980-2011 period as calibration and validation periods respectively. The most suitable - in terms of model skill determined from cross

  18. Climate sensitivity due to increased CO2: experiments with a coupled atmosphere and ocean general circulation model

    Science.gov (United States)

    Washington, Warren M.; Meehl, Gerald A.

    1989-06-01

    A version of the National Center for Atmospheric Research community climate model — a global, spectral (R15) general circulation model — is coupled to a coarse-grid (5° latitude-] longitude, four-layer) ocean general circulation model to study the response of the climate system to increases of atmospheric carbon dioxide (CO2). Three simulations are run: one with an instantaneous doubling of atmospheric CO2 (from 330 to 660 ppm), another with the CO2 concentration starting at 330 ppm and increasing linearly at a rate of 1% per year, and a third with CO2 held constant at 330 pm. Results at the end of 30 years of simulation indicate a globally averaged surface air temperature increase of 1.6° C for the instantaneous doubling case and 0.7°C for the transient forcing case. Inherent characteristics of the coarse-grid ocean model flow sea-surface temperatures (SSTs) in the tropics and higher-than-observed SSTs and reduced sea-ice extent at higher latitudes] produce lower sensitivity in this model after 30 years than in earlier simulations with the same atmosphere coupled to a 50-m, slab-ocean mixed layer. Within the limitations of the simulated meridional overturning, the thermohaline circulation weakens in the coupled model with doubled CO2 as the high-latitude ocean-surface layer warms and freshens and westerly wind stress is decreased. In the transient forcing case with slowly increasing CO2 (30% increase after 30 years), the zonal mean warming of the ocean is most evident in the surface layer near 30° 50° S. Geographical plots of surface air temperature change in the transient case show patterns of regional climate anomalies that differ from those in the instantaneous CO2 doubling case, particularly in the North Atlantic and northern European regions. This suggests that differences in CO2 forcing in the climate system are important in CO2 response in regard to time-dependent climate anomaly regimes. This confirms earlier studies with simple climate models

  19. Covarying modes of the Pacific SST and northern hemispheric midlatitude atmospheric circulation anomalies during winter

    Institute of Scientific and Technical Information of China (English)

    Yimin Zhu; Xiuqun Yang; Qian Xie; Yongqiang Yu

    2008-01-01

    The interannual-to-interdecadal relationship between the Pacific sea surface temperature (SST) and the northern hemispheric midlatitude's atmosphere represented by the circumpolar vortex was documented with the global oceanic and atmospheric reanalysis data of recent 50 years.Two covarying modes of the Pacific SST and northern circumpolar vortex anomalies during winter were examined using the singular value decomposition and wavelet analysis techniques.One is the interannual,ENSO-related mode and the other is the interdecadal,North Pacific SST-related mode with a period of around 20 years.The two modes exhibit distinct spatial structures.For the interannual mode,the SST anomaly is characterized by a typical ENSO pattern with the principal signature in the tropical eastern Pacific and secondary one in the central North Pacific,while the atmospheric anomaly is regional,characterized by a Pacific-North American pattern.For the interdecadal mode,large SST anomaly is located in the central North Pacific,while the atmospheric anomaly is zonally global,associated with the midlatitute's standing long-wave variations.When the central North Pacific is colder,the long-wave is stronger,and vice versa.Further investigations suggest that the interdecadal mode could involve an interaction between "two oceans and an atmosphere".

  20. Atmospheric Circulation of Hot Jupiters: Dayside–Nightside Temperature Differences. II. Comparison with Observations

    Science.gov (United States)

    Komacek, Thaddeus D.; Showman, Adam P.; Tan, Xianyu

    2017-02-01

    The full-phase infrared light curves of low-eccentricity hot Jupiters show a trend of increasing fractional dayside–nightside brightness temperature difference with increasing incident stellar flux, both averaged across the infrared and in each individual wavelength band. The analytic theory of Komacek & Showman shows that this trend is due to the decreasing ability with increasing incident stellar flux of waves to propagate from day to night and erase temperature differences. Here, we compare the predictions of this theory with observations, showing that it explains well the shape of the trend of increasing dayside–nightside temperature difference with increasing equilibrium temperature. Applied to individual planets, the theory matches well with observations at high equilibrium temperatures but, for a fixed photosphere pressure of 100 {mbar}, systematically underpredicts the dayside–nightside brightness temperature differences at equilibrium temperatures less than 2000 {{K}}. We interpret this as being due to the effects of a process that moves the infrared photospheres of these cooler hot Jupiters to lower pressures. We also utilize general circulation modeling with double-gray radiative transfer to explore how the circulation changes with equilibrium temperature and drag strengths. As expected from our theory, the dayside–nightside temperature differences from our numerical simulations increase with increasing incident stellar flux and drag strengths. We calculate model phase curves using our general circulation models, from which we compare the broadband infrared offset from the substellar point and dayside–nightside brightness temperature differences against observations, finding that strong drag or additional effects (e.g., clouds and/or supersolar metallicities) are necessary to explain many observed phase curves.

  1. 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.

  2. 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

  3. Possible Impacts of Barents Sea Ice on the Eurasian Atmospheric Circulation and the Rainfall of East China in the Beginning of Summer

    Institute of Scientific and Technical Information of China (English)

    王嘉; 郭裕福

    2004-01-01

    Possible influences of the Barents Sea ice anomalies on the Eurasian atmospheric circulation and the East China precipitation distribution in the late spring and early summer (May-June) are investigated by analyzing the observational data and the output of an atmospheric general circulation model (AGCM).The study indicates that the sea ice condition of the Barents Sea from May to July may be interrelated with the atmospheric circulation of June. When there is more than average sea ice in the Barents Sea, the local geopotential height of the 500-hPa level will decrease, and the same height in the Lake Baikal and Okhotsk regions will increase and decrease respectively to form a wave-chain structure over North Eurasia.This kind of anomalous height pattern is beneficial to more precipitation in the south part of East China and less in the north.

  4. Monthly to seasonal trends of streamflow in Romania and their connection with large-scale atmospheric circulation

    Science.gov (United States)

    Chelcea, Silvia; Ionita, Monica; Scholz, Patrick

    2016-04-01

    Water resources management has become a challenging issue in the southern Europe, an area under a recurrent water stress. It is widely known that hydrologic variables, such as streamflow, are significantly influenced by various large-scale atmospheric circulation patterns. The identification of relationships between the climate conditions given by these patterns and the seasonal streamflow may provide a valuable tool for long-range streamflow forecasting, adding helpful information for developing efficient water-management policies. As such, the aim of this study is to detect the trends in observed hydrological data and to look for the physical mechanisms responsible for the seasonal modes of inter-annual variability of mean streamflow over Romania in connection with teleconnections indices and atmospheric circulation patterns. The trend detection is performed for the monthly, seasonal and annual mean streamflow and the Standardized Streamflow Index (SSI) for an accumulation period of 1 month at 46 stations located over the whole Romanian territory, over the period 1935 - 2010. The results of the trend analysis show increasing trends (95% confidence level) in winter, spring, autumn and at annual time scale over the north-western part of the country and decreasing trends (95% confidence level) in spring over the southern part of the country. To identify the physical mechanisms responsible for the relationships between the annual and seasonal time series of the mean streamflow and large-scale atmospheric circulation patterns, the potential impact of large-scale climate patterns of the Arctic Oscillation (AO), North Atlantic Oscillation (NAO), El Niño Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO) and Atlantic Multidecadal Oscillation in modulating streamflow variability at country level is assessed. The correlation map analysis between the annual and seasonal streamflow time series and the Northern Hemisphere teleconnection patterns emphasize that AO

  5. Evapotranspiration and runoff from large land areas: Land surface hydrology for atmospheric general circulation models

    Science.gov (United States)

    Famiglietti, J. S.; Wood, Eric F.

    1993-01-01

    A land surface hydrology parameterization for use in atmospheric GCM's is presented. The parameterization incorporates subgrid scale variability in topography, soils, soil moisture and precipitation. The framework of the model is the statistical distribution of a topography-soils index, which controls the local water balance fluxes, and is therefore taken to represent the large land area. Spatially variable water balance fluxes are integrated with respect to the topography-soils index to yield our large topography-soils distribution, and interval responses are weighted by the probability of occurrence of the interval. Grid square averaged land surface fluxes result. The model functions independently as a macroscale water balance model. Runoff ratio and evapotranspiration efficiency parameterizations are derived and are shown to depend on the spatial variability of the above mentioned properties and processes, as well as the dynamics of land surface-atmosphere interactions.

  6. The effect of clear-air turbulence on a model of the general circulation of the atmosphere

    Science.gov (United States)

    Heck, W. J.; Panofsky, H. A.; Bender, M. A.

    1977-01-01

    Mixing coefficients due to clear-air turbulence are estimated from turbulence observations from aircraft, and from large-scale dissipation estimates from the large-scale energy budgets. Maximum coefficients occur near middle-latitude jet streams, and eddy viscosity there is of order of 10 sq m/sec; eddy conductivity is estimated to be about ten times smaller. These coefficients are introduced into the 12-layer general circulation model of the National Center of Atmospheric Research. They produce an apparently significant, though small reduction in maximum speed of the jet, and a reduction in eddy energy. Further, the stratospheric polar-night jet is produced at about the correct location with about the correct intensity.

  7. Butterflies, Black swans and Dragon kings: How to use the Dynamical Systems Theory to build a "zoology" of mid-latitude circulation atmospheric extremes?

    Science.gov (United States)

    Faranda, D.; Yiou, P.; Alvarez-Castro, M. C. M.

    2015-12-01

    A combination of dynamical systems and statistical techniques allows for a robust assessment of the dynamical properties of the mid-latitude atmospheric circulation. Extremes at different spatial and time scales are not only associated to exceptionally intense weather structures (e.g. extra-tropical cyclones) but also to rapid changes of circulation regimes (thunderstorms, supercells) or the extreme persistence of weather structure (heat waves, cold spells). We will show how the dynamical systems theory of recurrence combined to the extreme value theory can take into account the spatial and temporal dependence structure of the mid-latitude circulation structures and provide information on the statistics of extreme events.

  8. Response of atmosphere circulation on global and regional scales to the two El Niño flavors

    Science.gov (United States)

    Zheleznova, Irina; Gushchina, Daria

    2015-04-01

    El Niño - Southern Oscillation (ENSO) is one of the most striking anomalies in the climate system of our planet. Recently it has been established [Ashok et al., 2007; Kug et al., 2009] that El Niño appears in two different flavors: the canonical El Niño, which is characterized by the maximum SST anomalies in the eastern Pacific, and El Niño Modoki with maximum anomalies localized in the center of the Pacific Ocean, near the date line. Recent studies demonstrated [Ashok et al., 2007; Weng et al., 2009; Mo, 2010 et al.] that the remote response to the two types of El Niño is drastically different, being opposite in some areas. Based on the regression analysis the air temperature and precipitation anomalies observed during canonical and Modoki El Niño were defined. However, the structure and mechanisms of this response are fairly understood. A comprehensive analysis of the atmospheric circulation anomalies resulted from two types of El Niño may emerge the causes of different remote response associated to the two types of El Niño. The large-scale zonal atmospheric circulation response to El Niño is characterized by the poleward propagation of the signal from the equatorial and tropical latitudes. El Niño is associated with the intensification of western currents in mid latitudes and equatorial belt in the low troposphere and decreasing of the easterlies in tropics. The global circulation response is more intensive during El Niño Modoki as compare to the canonical El Niño. However, the spatial structure of the response is similar for the both types of El Niño. El Niño induces drastic anomalies in vertical circulation. It is shown that Hadley and Walker circulation anomalies associated to the Canonical and Modoki El Niño have different space localization and timing. Canonical El Niño is characterized by anomalous ascending motion in central and eastern Pacific localized near the equator and in the equatorial regions of the Southern Hemisphere. Over

  9. THREE-DIMENSIONAL ATMOSPHERIC CIRCULATION OF WARM AND HOT JUPITERS: EFFECTS OF ORBITAL DISTANCE, ROTATION PERIOD, AND NONSYNCHRONOUS ROTATION

    Energy Technology Data Exchange (ETDEWEB)

    Showman, Adam P. [Department of Planetary Sciences and Lunar and Planetary Laboratory, University of Arizona, 1629 University Blvd., Tucson, AZ 85721 (United States); Lewis, Nikole K. [Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Fortney, Jonathan J., E-mail: showman@lpl.arizona.edu [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States)

    2015-03-10

    Efforts to characterize extrasolar giant planet (EGP) atmospheres have so far emphasized planets within 0.05 AU of their stars. Despite this focus, known EGPs populate a continuum of orbital separations from canonical hot Jupiter values (0.03–0.05 AU) out to 1 AU and beyond. Unlike typical hot Jupiters, these more distant EGPs will not generally be synchronously rotating. In anticipation of observations of this population, we here present three-dimensional atmospheric circulation models exploring the dynamics that emerge over a broad range of rotation rates and incident stellar fluxes appropriate for warm and hot Jupiters. We find that the circulation resides in one of two basic regimes. On typical hot Jupiters, the strong day–night heating contrast leads to a broad, fast superrotating (eastward) equatorial jet and large day–night temperature differences. At faster rotation rates and lower incident fluxes, however, the day–night heating gradient becomes less important, and baroclinic instabilities emerge as a dominant player, leading to eastward jets in the midlatitudes, minimal temperature variations in longitude, and, often, weak winds at the equator. Our most rapidly rotating and least irradiated models exhibit similarities to Jupiter and Saturn, illuminating the dynamical continuum between hot Jupiters and the weakly irradiated giant planets of our own solar system. We present infrared (IR) light curves and spectra of these models, which depend significantly on incident flux and rotation rate. This provides a way to identify the regime transition in future observations. In some cases, IR light curves can provide constraints on the rotation rate of nonsynchronously rotating planets.

  10. Impact of Arctic sea ice loss on large-scale atmospheric circulation based on fully-coupled sensitivity experiments

    Science.gov (United States)

    Oudar, Thomas; Sanchez, Emilia; Terray, Laurent; Chauvin, Fabrice

    2016-04-01

    Arctic sea ice decline in the recent decades has been reported in observational studies. Modeling studies have confirmed that this downward trend in Arctic sea ice is mainly caused by increasing Greenhouse Gases (GHGs) concentrations into the atmosphere. The IPCC-AR5 report concluded that Arctic sea ice will continue to decrease and is projected to disappear in the middle of the 21st century, yielding to a ice-free region during boreal summer season. Arctic sea ice loss is expected to strongly impact the climate system. Recently, the climate community has conducted a number of studies to evaluate and understand the Arctic sea ice loss implications on climate. While some studies have shown that Arctic sea ice decline can significantly affect the large-scale atmospheric dynamics at high and mid-latitudes of the Northern Hemisphere, by altering the storm-tracks, the jet stream (position and strength) and the planetary waves, large uncertainties remain due to a low signal-to-noise ratio and experimental protocol differences leading to a large inter-model spread. In this work, we investigate the respective roles of Arctic sea ice loss and GHGs increase on the atmospheric dynamics by means of an idealized experimental set-up that uses the coupled model CNRM-CM5. The experimental set-up, based on a flux correction technique, will allow separating the contributions of Arctic sea ice loss from the GHGs increasing. We will focus mainly on the atmospheric circulation response in the Northern Hemisphere and on the associated synoptic variability, represented by the storm-tracks. We show that Arctic sea ice loss is responsible for an equatorward shift of the northern hemisphere jet, which is opposed to the GHGs effect. Finally we show that these shifts are consistent with the storm-tracks response.

  11. NUMERICAL STUDY ON INFLUENCE OF QINGHAI-XIZANG (TIBETAN) PLATEAU ON SEASONAL TRANSITION OF GLOBAL ATMOSPHERIC CIRCULATION

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    It is a worthwhile attempt to address the role of the Qinghai-Xizang Plateau in the seasonal transition of general circulation from a global prospective. In this paper, the CCM1 (R15L7) - LNWP spectral model is used to study the influences of the Qinghai-Xizang Plateau on the seasonal transfer of the general circulation, with the objective analysis form the State Meteorological Center for March 17, 1996 as the initial field. A mid-level heating source in regions on the same latitudes is shown to cause a warming center of 224 K to form on the level of 200 hPa that warms up the atmosphere by more than 7 K and a drop of temperature by about 6 K on most of the 200-hPa layer over the Antarctic continent, with the largest negative center being -8.28 K. It is favorable to the deepening and widening of the polar vortexes in the course of transition from summer to winter. The topographic effect of the plateau plays a vital role in forming and maintaining the mean troughs and ridges of the atmospheric circulation in Northern Hemisphere such that it strengthens (weakens) the south-north positive gradient of temperature on the northern (southern) side of the latitude zone in which the plateau sits and increases the north-south gradient of temperature near 30° N. The seasonal transition is thus favored so that the bulk travel of global westerly at the middle latitudes and the formation of Asian monsoon in early summer are made possible. In the equatorial and low-latitude areas where the geopotential is increased, the effect of the plateau terrain is also evident in that it is favorable for the northern withdrawal of the tropical high ridge in Southern Hemisphere and the northern shift of the subtropical high in Northern Hemisphere. In addition, the effect also helps increase the polar easterly over the Southern Hemisphere and weaken the low zone at 500 hPa. It acts as an increasing factor for the polar vortex around the Ross Sea and contributes to the genesis of the Somali Jet

  12. THE IMPACT OF PRECEDING ATMOSPHERIC CIRCULATION AND SST VARIATION ON FLOOD SEASON RAINFALL IN YUNNAN

    Institute of Scientific and Technical Information of China (English)

    YAN Hua-sheng; LU Ya-bin; CHENG Jian-gang; DUAN He; YANG Su-yu

    2005-01-01

    Spatial and temporal distribution characteristics and scale range of two significant areas were obtained by analyzing the relationship among summer rainfall in Yunnan province, height field and SST field (40°S - 40°N, 30 °E - 70°W) across the North Hemisphere at 200 hPa, 500 hPa and 850 hPa for Jan. to May and correlation, and field wave structure. Remote key regions among summer rainfall in Yunnan province, height field and SST field (40°S - 40°N, 30°E - 70°W) across the North Hemisphere at 200 hPa, 500 hPa and 850 hPa were studied through further analyzing of the circulation system and its climate / weather significance. The result shows that the forecast has dependable physical basis when height and SST fields were viewed as predictors and physical models of impacts on rainy season precipitation in Yunnan are preliminarily concluded.

  13. 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

    2015-12-01

    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.

  14. Atmospheric circulation of tidally-locked exoplanets: a suite of benchmark tests for dynamical solvers

    CERN Document Server

    Heng, Kevin; Phillipps, Peter J

    2010-01-01

    The complexity of atmospheric modelling and its inherent non-linearity, together with the limited amount of data of exoplanets available, motivate model intercomparisons and benchmark tests. In the geophysical community, the Held-Suarez test is a standard benchmark for comparing dynamical core simulations of the Earth's atmosphere with different solvers, based on statistically-averaged flow quantities. In the present study, we perform analogues of the Held-Suarez test for tidally-locked exoplanets with the GFDL-Princeton Flexible Modeling System (FMS) by subjecting both the spectral and finite difference dynamical cores to a suite of tests, including the standard benchmark for Earth, a hypothetical tidally-locked Earth, a "shallow" hot Jupiter model and a "deep" model of HD 209458b. We find qualitative and quantitative agreement between the solvers for the Earth, tidally-locked Earth and shallow hot Jupiter benchmarks, but the agreement is less than satisfactory for the deep model of HD 209458b. Further inves...

  15. Greenland accumulation and its connection to the large-scale atmospheric circulation in ERA-Interim and paleo-climate simulations

    Directory of Open Access Journals (Sweden)

    N. Merz

    2013-07-01

    Full Text Available Accumulation and aerosol chemistry records from Greenland ice cores offer the potential to reconstruct variability in Northern Hemisphere atmospheric circulation over the last millennia. However, an important prerequisite for a reconstruction is the stable relationship between local accumulation at the ice core site with the respective circulation pattern throughout the reconstruction period. We address this stability issue by using a comprehensive climate model and performing time-slice simulations for the present, the pre-industrial, the early Holocene and the last glacial maximum (LGM. The relationships between accumulation, precipitation and atmospheric circulation are investigated on on various time-scales. The analysis shows that the relationship between local accumulation on the Greenland ice sheet and the large-scale circulation undergoes a significant seasonal cycle. As the weights of the individual seasons change, annual mean accumulation variability is not necessarily related to the same atmospheric circulation patterns during the different climate states. Within a season, local Greenland accumulation variability is indeed linked to a consistent circulation pattern, which is observed for all studied climate periods, even for the LGM, however these circulation patterns are specific for different regions on the Greenland ice sheet. The simulated impact of orbital forcing and changes in the ice-sheet topography on accumulation exhibits strong spatial variability emphasizing that accumulation records from different ice core sites cannot be expected to look alike since they include a distinct local signature. Accumulation changes between different climate periods are dominated by changes in the amount of snowfall and are driven by both thermodynamic and dynamic factors. The thermodynamic impact determines the strength of the hydrological cycle, and warmer temperatures are generally accompanied by an increase in Greenland precipitation

  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

    2017-02-01

    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. Impacts of changes in North Atlantic atmospheric circulation on particulate matter and human health in Europe

    Science.gov (United States)

    Pausata, Francesco S. R.; Pozzoli, Luca; Van Dingenen, Rita; Vignati, Elisabetta; Cavalli, Fabrizia; Dentener, Frank J.

    2013-08-01

    In this study we use a global climate model to assess particulate matter (PM) variability induced by the North Atlantic Oscillation (NAO) in Europe during winter and the potential impact on human health of a future shift in the NAO mean state. Our study shows that extreme NAO phases in the 1990s modulated most of the interannual variability of winter PM concentrations in several European countries. Increased PM concentrations as a result of a positive shift in the mean winter NAO of one standard deviation would lead to about 5500 additional premature deaths in Mediterranean countries, compared to the simulated average PM health impact for the year 2000. In central-northern Europe, instead, higher wind speed and increased PM removal by precipitation lead to negative PM concentration anomalies with associated health benefits. We suggest that the NAO index is a useful indicator for the role of interannual atmospheric variability on large-scale pollution-health impacts.

  18. 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

  19. 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

  20. 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

  1. A fast stratospheric chemistry solver: the E4CHEM submodel for the atmospheric chemistry global circulation model EMAC

    Directory of Open Access Journals (Sweden)

    A. J. G. Baumgaertner

    2010-02-01

    Full Text Available The atmospheric chemistry general circulation model ECHAM5/MESSy (EMAC and the atmospheric chemistry box model CAABA are extended by a computationally very efficient submodel for atmospheric chemistry, E4CHEM. It focuses on stratospheric chemistry but also includes background tropospheric chemistry. It is based on the chemistry of MAECHAM4-CHEM and is intended to serve as a simple and fast alternative to the flexible but also computationally more demanding submodel MECCA. In a model setup with E4CHEM, EMAC is now also suitable for simulations of longer time scales. The reaction mechanism contains basic O3, CH4, CO, HOx, NOx and ClOx gas phase chemistry. In addition, E4CHEM includes optional fast routines for heterogeneous reactions on sulphate aerosols and polar stratospheric clouds (substituting the existing submodels PSC and HETCHEM, and scavenging (substituting the existing submodel SCAV. We describe the implementation of E4CHEM into the MESSy structure of CAABA and EMAC. For some species the steady state in the box model differs by up to 100% when compared to results from CAABA/MECCA due to different reaction rates. After an update of the reaction rates in E4CHEM the mixing ratios in both boxmodel and 3-D model simulations are in satisfactory agreement with the results from a simulation where MECCA with a similar chemistry scheme was employed. Finally, a comparison against a simulation with a more complex and already evaluated chemical mechanism is presented in order to discuss shortcomings associated with the simplification of the chemical mechanism.

  2. 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

  3. 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

  4. THREE-DIMENSIONAL ATMOSPHERIC CIRCULATION MODELS OF HD 189733b AND HD 209458b WITH CONSISTENT MAGNETIC DRAG AND OHMIC DISSIPATION

    Energy Technology Data Exchange (ETDEWEB)

    Rauscher, Emily [Lunar and Planetary Laboratory, University of Arizona, 1629 East University Blvd., Tucson, AZ 85721 (United States); Menou, Kristen [Department of Astronomy, Columbia University, 550 West 120th St., New York, NY 10027 (United States)

    2013-02-10

    We present the first three-dimensional circulation models for extrasolar gas giant atmospheres with geometrically and energetically consistent treatments of magnetic drag and ohmic dissipation. Atmospheric resistivities are continuously updated and calculated directly from the flow structure, strongly coupling the magnetic effects with the circulation pattern. We model the hot Jupiters HD 189733b (T {sub eq} Almost-Equal-To 1200 K) and HD 209458b (T {sub eq} Almost-Equal-To 1500 K) and test planetary magnetic field strengths from 0 to 30 G. We find that even at B = 3 G the atmospheric structure and circulation of HD 209458b are strongly influenced by magnetic effects, while the cooler HD 189733b remains largely unaffected, even in the case of B = 30 G and super-solar metallicities. Our models of HD 209458b indicate that magnetic effects can substantially slow down atmospheric winds, change circulation and temperature patterns, and alter observable properties. These models establish that longitudinal and latitudinal hot spot offsets, day-night flux contrasts, and planetary radius inflation are interrelated diagnostics of the magnetic induction process occurring in the atmospheres of hot Jupiters and other similarly forced exoplanets. Most of the ohmic heating occurs high in the atmosphere and on the dayside of the planet, while the heating at depth is strongly dependent on the internal heat flux assumed for the planet, with more heating when the deep atmosphere is hot. We compare the ohmic power at depth in our models, and estimates of the ohmic dissipation in the bulk interior (from general scaling laws), to evolutionary models that constrain the amount of heating necessary to explain the inflated radius of HD 209458b. Our results suggest that deep ohmic heating can successfully inflate the radius of HD 209458b for planetary magnetic field strengths of B {>=} 3-10 G.

  5. 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

  6. 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.

  7. 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.

  8. Evaluating the skills of isotope-enabled general circulation models against in situ atmospheric water vapor isotope observations

    Science.gov (United States)

    Steen-Larsen, H. C.; Risi, C.; Werner, M.; Yoshimura, K.; Masson-Delmotte, V.

    2017-01-01

    The skills of isotope-enabled general circulation models are evaluated against atmospheric water vapor isotopes. We have combined in situ observations of surface water vapor isotopes spanning multiple field seasons (2010, 2011, and 2012) from the top of the Greenland Ice Sheet (NEEM site: 77.45°N, 51.05°W, 2484 m above sea level) with observations from the marine boundary layer of the North Atlantic and Arctic Ocean (Bermuda Islands 32.26°N, 64.88°W, year: 2012; south coast of Iceland 63.83°N, 21.47°W, year: 2012; South Greenland 61.21°N, 47.17°W, year: 2012; Svalbard 78.92°N, 11.92°E, year: 2014). This allows us to benchmark the ability to simulate the daily water vapor isotope variations from five different simulations using isotope-enabled general circulation models. Our model-data comparison documents clear isotope biases both on top of the Greenland Ice Sheet (1-11‰ for δ18O and 4-19‰ for d-excess depending on model and season) and in the marine boundary layer (maximum differences for the following: Bermuda δ18O = 1‰, d-excess = 3‰; South coast of Iceland δ18O = 2‰, d-excess = 5‰; South Greenland δ18O = 4‰, d-excess = 7‰; Svalbard δ18O = 2‰, d-excess = 7‰). We find that the simulated isotope biases are not just explained by simulated biases in temperature and humidity. Instead, we argue that these isotope biases are related to a poor simulation of the spatial structure of the marine boundary layer water vapor isotopic composition. Furthermore, we specifically show that the marine boundary layer water vapor isotopes of the Baffin Bay region show strong influence on the water vapor isotopes at the NEEM deep ice core-drilling site in northwest Greenland. Our evaluation of the simulations using isotope-enabled general circulation models also documents wide intermodel spatial variability in the Arctic. This stresses the importance of a coordinated water vapor isotope-monitoring network in order to discriminate amongst these model

  9. Validation of Atmospheric Dynamics (VADY) - representation of circulation types/dynamical modes in the decadal-prediction model system of MPI-ESM

    Science.gov (United States)

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

    2016-04-01

    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 improve a climate model system (MPI-ESM) in such a way that it 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 (DLR) and circulation dynamics (IGUA). 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. The present contribution provides results of the model validation concerning circulation types/dynamical modes. Results are shown for both the frequency of occurrence and internal characteristics (e. g. persistence or intensity), and for different classification methods (e. g. based on PCA or clustering techniques). The representation of circulation types/dynamical modes will be compared for different generations of the MPI-ESM decadal-prediction model (baseline0, baseline1, prototype) in order to clarify both advances and limitations in the development of the model. Furthermore

  10. Evaluation of North Eurasian snow-off dates in the ECHAM5.4 atmospheric general circulation model

    Directory of Open Access Journals (Sweden)

    P. Räisänen

    2014-12-01

    Full Text Available The timing of springtime end of snowmelt (snow-off date in northern Eurasia in version 5.4 of the ECHAM5 atmospheric general circulation model (GCM is evaluated through comparison with a snow-off date data set based on space-borne microwave radiometer measurements and with Russian snow course data. ECHAM5 reproduces well the observed gross geographical pattern of snow-off dates, with earliest snow-off (in March in the Baltic region and latest snow-off (in June in the Taymyr Peninsula and in northeastern parts of the Russian Far East. The primary biases are (1 a delayed snow-off in southeastern Siberia (associated with too low springtime temperature and too high surface albedo, in part due to insufficient shielding by canopy; and (2 an early bias in the western and northern parts of northern Eurasia. Several sensitivity experiments were conducted, where biases in simulated atmospheric circulation were corrected through nudging and/or the treatment of surface albedo was modified. While this alleviated some of the model biases in snow-off dates, 2 m temperature and surface albedo, especially the early bias in snow-off in the western parts of northern Eurasia proved very robust and was actually larger in the nudged runs. A key issue underlying the snow-off biases in ECHAM5 is that snowmelt occurs at too low temperatures. Very likely, this is related to the treatment of the surface energy budget. On one hand, the surface temperature Ts is not computed separately for the snow-covered and snow-free parts of the grid cells, which prevents Ts from rising above 0 °C before all snow has vanished. Consequently, too much of the surface net radiation is consumed in melting snow and too little in heating the air. On the other hand, ECHAM5 does not include a canopy layer. Thus, while the albedo reduction due to canopy is accounted for, the shielding of snow on ground by the overlying canopy is not considered, which leaves too much solar radiation available for

  11. Simulations of the Tropical Intraseasonal Oscillation by the Atmospheric General Circulation Model of the Beijing Climate Center

    Institute of Scientific and Technical Information of China (English)

    DONG Min; WU Tongwen; WANG Zaizhi; ZHANG Fang

    2010-01-01

    The performance of BCC (Beijing Climate Center) AGCM 2.0.1 (Atmospheric General Circulation Model version 2.0.1) in simulating the tropical intraseasonal oscillation (TIO) is examined in this paper.The simulations are validated against observation and compared with the NCAR CAM3 (Community Atmosphere Model version 3) results.The BCC AGCM2.0.1 is developed based on the original BCC AGCM (version 1) and NCAR CAM3.New reference atmosphere and reference pressure are introduced into the model.Therefore,the original prognostic variables of temperature and surface pressure become their departures from the reference atmosphere.A new Zhang-McFarlane convective parameterization scheme is incorporated into the model with a few modifications.Other modifications include those in the boundary layer process and snow cover calculation.All simulations are run for 52 yr from 1949 to 2001 under the lower boundary conditions of observed monthly SST.The TIOs from the model are analyzed.The comparison shows that the NCAR CAM3 has a poor ability in simulating the TIO.The simulated strength of the TIO is very weak.The energy of the eastward moving waves is similar to that of the westward moving waves in CAM3.While in observation the former is much larger than the latter.The seasonal variation and spatial distribution of the TIO produced by CAM3 are also much different from the observation.The ability of the BCC AGCM2.0.1 in simulating the TIO is significantly better.The simulated TIO is evident.The strength of the TIO produced by the BCC AGCM2.0.1 is close to the observation.The energy of eastward moving.waves is much stronger than that of the westward moving waves,which is consistent with the observation.There is no significant difference in the seasonal variation and spatial distribution of the TIO between the BCC model simulation and the observation.In general,the BCC model performs better than CAM3 in simulating the TIO.

  12. 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

    2010-09-01

    Full Text Available We study the initiation of a Marinoan Snowball Earth (635 million years before present with the most sophisticated atmosphere-ocean general circulation model ever used for this purpose, ECHAM5/MPI-OM. 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 quadrupling 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. In summary, our results contradict previous claims that Snowball Earth initiation would require "extreme" forcings.

  13. 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.

  14. Influence of LGM boundary conditions on the global water isotope distribution in an atmospheric general circulation model

    Directory of Open Access Journals (Sweden)

    T. Tharammal

    2012-04-01

    Full Text Available A series of experiments was conducted using a water isotope tracers-enabled atmospheric general circulation model (Community Atmosphere Model version 3.0, CAM3.0-Iso, by changing the individual boundary conditions (greenhouse gases, ice sheet albedo and topography, sea-surface temperature each at a time to Last Glacial Maximum (LGM values. In addition, a combined simulation with all the boundary conditions being set to LGM values was carried out. A pre-industrial (PI simulation with boundary conditions taken according to the PMIP2 (Paleoclimate Modelling Intercomparison Project protocol was performed as the control experiment. The experiments were designed in order to analyze the temporal and 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 highly correlated with the temperature decrease over them. The SST and ice sheet topography changes were found to be responsible for most of the changes in the climate and hence the δ18Oprecip distribution among the simulations.

  15. Simulation of the Atlantic meridional overturning circulation in an atmosphere-ocean global coupled model. Part II: weakening in a climate change experiment: a feedback mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Guemas, Virginie [Meteo-France, CNRS, Centre National de Recherches Meteorologiques/Groupe d' Etude de l' Atmosphere Meteorologique (CNRM/GMGEC), Toulouse Cedex (France); CEA-CNRS-UVSQ, Laboratoire des Sciences du Climat et de l' Environnement, UMR 1572, Gif-sur-Yvette (France); Salas-Melia, David [Meteo-France, CNRS, Centre National de Recherches Meteorologiques/Groupe d' Etude de l' Atmosphere Meteorologique (CNRM/GMGEC), Toulouse Cedex (France)

    2008-06-15

    Most state-of-the art global coupled models simulate a weakening of the Atlantic meridional overturning circulation (MOC) in climate change scenarios but the mechanisms leading to this weakening are still being debated. The third version of the CNRM (Centre National de Recherches Meteorologiques) global atmosphere-ocean-sea ice coupled model (CNRM-CM3) was used to conduct climate change experiments for the Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC AR4). The analysis of the A1B scenario experiment shows that global warming leads to a slowdown of North Atlantic deep ocean convection and thermohaline circulation south of Iceland. This slowdown is triggered by a freshening of the Arctic Ocean and an increase in freshwater outflow through Fram Strait. Sea ice melting in the Barents Sea induces a local amplification of the surface warming, which enhances the cyclonic atmospheric circulation around Spitzberg. This anti-clockwise circulation forces an increase in Fram Strait outflow and a simultaneous increase in ocean transport of warm waters toward the Barents Sea, favouring further sea ice melting and surface warming in the Barents Sea. Additionally, the retreat of sea ice allows more deep water formation north of Iceland and the thermohaline circulation strengthens there. The transport of warm and saline waters toward the Barents Sea is further enhanced, which constitutes a second positive feedback. (orig.)

  16. Changes in annual accumulation retrieved from Geladaindong ice core and its relationship to atmospheric circulation over the Tibetan Plateau

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Annual accumulation records covering 1935 to 2004 were reconstructed using Geladaindong ice core in the source of Yangtze River. A significant positive correlation between annual accumulation and precipitation from nearby meteorological stations was found, suggesting ice core accumulation could be taken as a precipitation proxy in the region. In the past 70 years, precipitation in the Geladaindong region was low from 1930s to early 1960s, and the lowest value occurred in the later 1950s. Since 1960s, precipitation increased dramatically and reached the maximum around 1980s, then decreased slightly in 1990s. By using Mann-Kendall rank statistical test method, a change point for precipitation was determined in 1967. Analysis of the atmospheric circulation over the Tibetan Plateau suggested that, compared with the southwest wind during the low precipitation period (before 1967), it extended about 2 latitudes northward during high precipitation period (after 1967). Moreover, during the high precipitation, the trough over the Bal Karshi Lake was also enhanced, and both the meridional wind and vapor transporting displayed a remarkable aggrandizement.

  17. Moisture transport into the Arctic: Source-receptor relationships and the roles of atmospheric circulation and evaporation

    Science.gov (United States)

    Vázquez, M.; Nieto, R.; Drumond, A.; Gimeno, L.

    2016-11-01

    Hydrological processes play a key role in the Arctic, as well as being an important part of the response of this region to climate change. The origin of the moisture arriving (and then precipitating) in the Arctic is a crucial question in our understanding of the Arctic hydrological cycle. In an attempt to answer this, the present study uses the Lagrangian diagnosis model FLEXPART (FLEXible PARTicle dispersion model) to localize the main sources of moisture for the Arctic region, to analyze their variability and their contribution to precipitation, and to consider the implications of any changes in the transport of moisture from particular sources within the system. From this analysis, four major moisture sources appear as the most important moisture supplies into the system: the subtropical and southern extratropical Pacific and Atlantic Oceans, North America, and Siberia. Oceanic sources play an important role throughout the year, whereas continental ones only take effect in summer. The sink areas associated with each source have been shown to be moderately influenced by changes in atmospheric circulation, mainly associated with the East Atlantic pattern for the Atlantic source and related to West Pacific and Pacific/North American (PNA) teleconnection patterns for the Pacific one. On the other hand, the variability over the sinks does not seem to be significantly related to changes in evaporation at an interannual scale.

  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. Impacts of Atlantic multi-decadal oscillation to summer atmospheric circulation in the northern mid-latitude

    Science.gov (United States)

    Lin, Jianshe

    2016-04-01

    Previous studies indicated that Atlantic multi-decadal oscillation (AMO) has significant impacts on regional and global climate. The impacts of the AMO on the summertime atmospheric circulation over the mid latitudes of the Northern Hemisphere and possible mechanisms were investigated througal observational analysis and numerical experiments by AGCMs. The results show that the interdecadal oscillation pattern of land surface temperature in the mid-latitudes are highly associated with the AMO. The eastern Europe, East Asia and the United States were warmer, while central Asia and northwest of the North America were cold during the positive phase of the AMO. Associated geopotential height anomalies is dominated by a barotropic wave train propagating along the jet stream, with zonal wavenumber 4 or 5. Basically, positive (negative) geopotential height anomalies correspond to warm (cold) anomalies of land surface temperature. The wave train pattern is called as interdecadal circumglobal teleconnection pattern Idealized numerical experiment by AGCMs indicates that the AMO-related SST anomalies tend to induce the teleconnection pattern, which was primarily forced by extratropical component of the AMO.

  20. Assessing the tangent linear behaviour of common tracer transport schemes and their use in a linearised atmospheric general circulation model

    Directory of Open Access Journals (Sweden)

    Daniel Holdaway

    2015-09-01

    Full Text Available 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 non-linear 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.

  1. Interannual Variability of Autumn Precipitation over South China and its Relation to Atmospheric Circulation and SST Anomalies

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The interannual variability of autumn precipitation over South China and its relationship with atmospheric circulation and SST anomalies are examined using the autumn precipitation data of 160 stations in China and the NCEP-NCAR reanalysis dataset from 1951 to 2004. Results indicate a strong interannual variability of autumn precipitation over South China and its positive correlation with the autumn western Pacific subtropical high (WPSH). In the flood years, the WPSH ridge line lies over the south of South China and the strengthened ridge over North Asia triggers cold air to move southward. Furthermore, there exists a significantly anomalous updraft and cyclone with the northward stream strengthened at 850 hPa and a positive anomaly center of meridional moisture transport strengthening the northward warm and humid water transport over South China. These display the reverse feature in drought years. The autumn precipitation interannual variability over South China correlates positively with SST in the western Pacific and North Pacific, whereas a negative correlation occurs in the South Indian Ocean in July. The time of the strongest lag-correlation coefficients between SST and autumn precipitation over South China is about two months, implying that the SST of the three ocean areas in July might be one of the predictors for autumn precipitation interannual variability over South China. Discussion about the linkage among July SSTs in the western Pacific, the autumn WPSH and autumn precipitation over South China suggests that SST anomalies might contribute to autumn precipitation through its close relation to the autumn WPSH.

  2. Changes of Atmospheric Circulation since the Last Interstadial as Indicated by. the Lake-status Record in China

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The effective precipitation and the frame of atmospheric circulation in the past three key periods, i.e.30 ka BP, 18 ka BP and 6 ka BP, have been analyzed on the basis of the palaeolake status record produced by the Chinese Lake Status Data Base. The results show that the west-central paty of China was characterized by high lakelevels at 30 ka BP, resulting from strengthened southwest monsoons; whereas the high lake stand, occurring in the west-central part of China at 18 ka BP, was caused by the southward shift and the strengthening of westerlies although the high-stand distribution was reduced. Meanwhile, the east-central part of China was under the control of strong winter monsoons at 18 ka BP. The high lake-levels, which occurred in the east-central part of China at 6 ka BP,are related to the enhanced East-Asian summer monsoons; while the lowering of the lake-level in the west-central part of China at 6 ka BP was due to the northward shift and corresponding shrink of the westerlies. A comparison between the lake status and the palaeoclimate models has shown that there do exist discrepancies between the geological evidence and the model simulations. The agreement between them provides a possible mechanical explanation on the geological phenomena, but the discrepancy shows that the model needs to be revised to a great extent.

  3. 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.

  4. Simulating the Effects of the 1991 Mount Pinatubo Volcanic Eruption Using the ARPEGE Atmosphere General Circulation Model

    Institute of Scientific and Technical Information of China (English)

    Odd Helge OTTER(A)

    2008-01-01

    The climate changes that occured following the volcanic eruption of Mount Pinatubo in the Phillippines on 15 June 1991 have been simulated using the ARPEGE atmosphere general circulation model (AGCM).The model was forced by a reconstructed spatial-time distribution of stratospheric aerosols intended for use in long climate simulations.Four statistical ensembles of the AGCM simulations with and without volcanic aerosols over a period of 5 years following the eruption have been made,and the calculated fields have been compared to available observations.The model is able to reproduce SOme of the observed features after the eruption,such as the winter warming pattern that was observed over the Northern Hemisphere(NH)during the following winters.This pattern Was caused by an enhanced Equator-to-pole temperature gradient in the stratosphere that developed due to aerosol heating of the tropics.This in turn led to a strengthening of the polar vortex,which tends to modulate the planetary wave field in such a way that an anomalously positive Arctic Oscillation Pattern is produced in the troposphere and at the surface,favouring warm conditions over the NH.During the summer.the model produced a more uniform cooling over the NH.

  5. Study of the behaviour of artificial radioactive aerosols. Applications to some problems of atmospheric circulation (1963); Etude du comportement dcs aerosols radioactifs artificiels. Applications a quelques problemes de circulation atmospherique (1963)

    Energy Technology Data Exchange (ETDEWEB)

    Lambert, G. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1963-11-15

    The aim of this work, consists in the examination of the behaviour of radioactive aerosols produced in the atmosphere by nuclear explosions, in order to deduce the most general laws governing atmospheric circulation and diffusion. After having given a general table of the radioactive aerosols present the authors consider the validity and the precision of the measurement methods and the concentration of the aerosols at ground level and in the upper atmosphere, as well as their deposition on the ground. The existence is thus demonstrated of a tropospheric equatorial barrier and of discontinuous and seasonal aspects of stratosphere-troposphere transfers. The role is shown of precipitations and dry auto-filtration in the lower atmosphere cleaning processes. This work makes it possible to describe the general behaviour of dust from the stratosphere, and to improve the total radioactive contamination of the globe. (author) [French] L'objectif de ce travail consiste a examiner le comportement des aerosols radioactifs introduits dans l'atmosphere par les explosions nucleaires, pour en deduire les lois les plus generals de la circulation et diffusion atmospheriques. Apres avoir dresse un tableau d'ensemble des aerosols radioactifs presents, on examine la validite et la precision des methodes de mesure de leur concentration, au niveau du sol et en haute atmosphere, ainsi que de leur depot a la surface du sol. On met ainsi en evidence l'existence d'une barriere equatoriale tropospherique; l'aspect discontinu et saisonnier des transferts stratosphere-troposphere; le role des precipitations et de l'auto-filtration seche, dans les processus de nettoyage de la basse atmosphere. Ces etudes permettent de decrire le comportement general des poussieres d'origine stratospherique et d'ameliorer le bilan de la contamination radioactive du globe. (auteur)

  6. Intercomparsion of regional biases and doubled CO{sub 2}-sensitivity of coupled atmosphere-ocean general circulation model experiments

    Energy Technology Data Exchange (ETDEWEB)

    Kittel, T.G.F. [Nat. Center for Atmos. Res., Boulder, CO (United States). Climate and Global Dynamics Div.]|[Climate System Modeling Program, University Corporation for Atmospheric Research, Boulder, CO 80307-3000 (United States); Giorgi, F.; Meehl, G.A. [Nat. Center for Atmos. Res., Boulder, CO (United States). Climate and Global Dynamics Div.

    1998-01-01

    We compared regional biases and transient doubled CO{sub 2} sensitivities of nine coupled atmosphere-ocean general circulation models (GCMs) from six international climate modeling groups. We evaluated biases and responses in winter and summer surface air temperatures and precipitation for seven subcontinental regions, including those in the 1990 intergovernmental panel on climate change (IPCC) scientific assessment. Regional biases were large and exceeded the variance among four climatological datasets, indicating that model biases were not primarily due to uncertainty in observations. Model responses to altered greenhouse forcing were substantial (average temperature change=2.7{+-}0.9 C, range of precipitation change =-35 to +120% of control). While coupled models include more climate system feedbacks than earlier GCMs implemented with mixed-layer ocean models, inclusion of a dynamic ocean alone did not improve simulation of long-term mean climatology nor increase convergence among model responses to altered greenhouse gas forcing. On the other hand, features of some of the coupled models including flux adjustment (which may have simply masked simulation errors), high horizontal resolution, and estimation of screen height temperature contributed to improved simulation of long-term surface climate. The large range of model responses was partly accounted for by inconsistencies in forcing scenarios and transient-simulation averaging periods. Nonetheless, the models generally had greater agreement in their sensitivities than their controls did with observations. This suggests that consistent, large-scale response features from an ensemble of model sensitivity experiments may not depend on details of their representation of present-day climate. (orig.) With 4 figs., 2 tabs., 65 refs.

  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. Interdecadal Variations of Precipitation and Temperature in China Around the Abrupt Change of Atmospheric Circulation in 1976

    Institute of Scientific and Technical Information of China (English)

    LI Chunhui; WAN Qilin; LIN Ailan; GU Dejun; ZHENG Bin

    2009-01-01

    The interdecadal characteristics of rainfall and temperature in China before and after the abrupt change of the general circulation in 1976 are analyzed using the global 2.5°×2.5° monthly mean reanalysis data from the National Centers for Environmental Prediction of US and the precipitation and temperature data at the 743 stations of China from the National Climate Center of China. The results show that after 1976, springtime precipitation and temperature were anomalously enhanced and reduced respectively in South China, while the reverse was true in the western Yangtze River basin. In summer, precipitation was anomalously less in South China, more in the Yangtze River basin, less again in North China and more again in Northeast China, showing a distribution pattern alternating with negative and positive anomalies ("-, +, -, +"). Meanwhile, temperature shows a distribution of warming in South China, cooling in the Yangtze and Huaihe River basins, and warming again in northern China. In autumn, precipitation tended to decrease and temperature tended to increase in most parts of the country. In winter, precipitation increased moderately in South China and warming was the trend across all parts of China. The interdecadal decline of mean temperature in spring and summer in China was mainly due to the daily maximum temperature variation, while the interdecadal increase was mainly the result of the minimum temperature change. The overall warming in autumn (winter) was mostly influenced by the minimum (maximum) temperature variation. These changes were closely related to the north-south shifts of the ascending and descending branches of the Hadley cell, the strengthening and north-south progression of the westerly jet stream, and the atmospheric stratification and water vapor transport conditions.

  9. Contrasts of Atmospheric Circulation and Associated Tropical Convection between Huaihe River Valley and Yangtze River Valley Mei-yu Flooding

    Institute of Scientific and Technical Information of China (English)

    HONG Jieli; LIU Yimin

    2012-01-01

    The significant differences of atmospheric circulation between flooding in the Huaihe and Yangtze River valleys during early mei-yu (i.e.,the East Asian rainy season in June) and the related tropical convection were investigated.During the both flooding cases,although the geopotential height anomalies always exhibit equivalent barotropic structures in middle to high latitudes at middle and upper troposphere,the phase of the Rossby wave train is different over Eurasian continent.During flooding in the Huaihe River valley,only one single blocking anticyclone is located over Baikal Lake.In contrast,during flooding in the Yangtze River valley,there are two blocking anticyclones.One is over the Ural Mountains and the other is over Northeast Asia.In the lower troposphere a positive geopotential height anomaly is located at the western ridge of subtropical anticyclone over Western Pacific (SAWP) in both flooding cases,but the location of the height anomaly is much farther north and west during the Huaihe River mei-yu flooding.Furthermore,abnormal rainfall in the Huaihe River valley and the regions north of it in China is closely linked with the latent heating anomaly over the Arabian Sea and Indian peninsula.However,the rainfall in the Yangtze River valley and the regions to its south in China is strongly related to the convection over the western tropical Pacific.Numerical experiments demonstrated that the enhanced latent heating over the Arabian Sea and Indian peninsula causes water vapor convergence in the region south of Tibetan Plateau and in the Huaihe River valley extending to Japan Sea with enhanced precipitation; and vapor divergence over the Yangtze River valley and the regions to its south with deficient precipitation.While the weakened convection in the tropical West Pacific results in moisture converging over the Yangtze River and the region to its south,along with abundant rainfall.

  10. Variation in Summer Rainfall in North China during the Period 1956-2007 and Links with Atmospheric Circulation

    Institute of Scientific and Technical Information of China (English)

    LIANG Feng; TAO Shiyan; WEI Jie; BUEH Cholaw

    2011-01-01

    Using gauge precipitation data and NCEP-NCAR reanalysis data, the interdecadal changes in summer precipitation during the period 1956-2007 in North China and the link with atmospheric circulation change over Eurasia are studied. Results show that precipitation amounts decreased by 16.2 mm per decade, which was attributable to a significant reduction in precipitation frequency. Contrary wave trains were found in the subtropical westerly jet (wave guide) over Eurasia for the wet and dry years of North China. When the wave trains had a ridge (trough) around the Korean Peninsula, conditions favored (disfavored) the westward and northward extension of the West Pacific subtropical high. The westward and northward extension of the West Pacific subtropical high is, and was, beneficial to rainfall in North China. The downstream propagation of Rossby waves was found to favor the maintenance of these wave trains. Sensible heating in the south of Lake Baikal and latent heating from the Korean Peninsula to the south of Japan increased during the period 1980-2007, as compared to that during 1957-1979, the wet period. These changes had positive influences on the maintenance of Anticyclonic-Cyclonic anomaly centers in the wave trains. Furthermore, northerly winds were prevalent in the lower troposphere during the dry period (1980-2007), which prohibited the transportation of water vapor to North China from the seas and thereby led to a decrease in rainfall in North China. The weakening of the Indian Monsoon during the dry period might be one of reasons for the reduction in water vapor transportation.

  11. The atmospheric circulation on the synoptic scale during the culmination phase of the El-Niño − Southern Oscillation events (1997−1998

    Directory of Open Access Journals (Sweden)

    E. V. Sokolikhina

    2006-01-01

    Full Text Available For the classification of the synoptic processes in the tropical Pacific using daily data, criteria were proposed for identifying the different evolutional phases of the equatorial westerly wind zone. The criteria are based on the location, extent and activity of the westerly wind zone on the 850 hPa isobaric surface. According to this classification all the observed variants of the westerly wind regime above the tropical Pacific can be divided into three classes: normal, active, and break. For each class one specific pattern of tropical atmospheric circulation centers and divergent wind velocity potential in the lower and upper troposphere are found. Using the singular value decomposition method (SVD the connection between the atmospheric circulation and sea surface temperature (SST of equatorial Pacific is investigated.

  12. The circulation pattern and day-night heat transport in the atmosphere of a synchronously rotating aquaplanet: Dependence on planetary rotation rate

    Science.gov (United States)

    Noda, S.; Ishiwatari, M.; Nakajima, K.; Takahashi, Y. O.; Takehiro, S.; Onishi, M.; Hashimoto, G. L.; Kuramoto, K.; Hayashi, Y.-Y.

    2017-01-01

    In order to investigate a possible variety of atmospheric states realized on a synchronously rotating aquaplanet, an experiment studying the impact of planetary rotation rate is performed using an atmospheric general circulation model (GCM) with simplified hydrological and radiative processes. The entire planetary surface is covered with a swamp ocean. The value of planetary rotation rate is varied from zero to the Earth's, while other parameters such as planetary radius, mean molecular weight and total mass of atmospheric dry components, and solar constant are set to the present Earth's values. The integration results show that the atmosphere reaches statistically equilibrium states for all runs; none of the calculated cases exemplifies the runaway greenhouse state. The circulation patterns obtained are classified into four types: Type-I characterized by the dominance of a day-night thermally direct circulation, Type-II characterized by a zonal wave number one resonant Rossby wave over a meridionally broad westerly jet on the equator, Type-III characterized by a long time scale north-south asymmetric variation, and Type-IV characterized by a pair of mid-latitude westerly jets. With the increase of planetary rotation rate, the circulation evolves from Type-I to Type-II and then to Type-III gradually and smoothly, whereas the change from Type-III to Type-IV is abrupt and discontinuous. Over a finite range of planetary rotation rate, both Types-III and -IV emerge as statistically steady states, constituting multiple equilibria. In spite of the substantial changes in circulation, the net energy transport from the day side to the night side remains almost insensitive to planetary rotation rate, although the partition into dry static energy and latent heat energy transports changes. The reason for this notable insensitivity is that the outgoing longwave radiation over the broad area of the day side is constrained by the radiation limit of a moist atmosphere, so that the

  13. 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

  14. 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

  15. Seasonal sensitivity of the eddy-driven jet to tropospheric heating in an idealized atmospheric general circulation model

    Science.gov (United States)

    McGraw, Marie C.

    A dry dynamical core is used to investigate the seasonal sensitivity of the circulation to two idealized thermal forcings--a tropical upper tropospheric forcing, and a polar lower tropospheric forcing. The circulation is modified using a set of perpetual simulations to simulate each month of the year, while the thermal forcings are held constant. The circu- lation responses to tropical warming and polar warming are studied separately, and then the response to the simultaneously applied forcings is analyzed. Finally, the seasonality of the internal variability of the circulation is explored as a possible mechanism to explain the seasonality of the responses. The primary results of these experiments are: 1) There is a seasonal sensitivity in the circulation response to both the tropical and polar forcings. 2) The jet position response to each forcing is greatest in the transition seasons, and the jet speed response exhibits a seasonal sensitivity to both forcings although the seasonal sensi- tivities are not the same. 3) The circulation response is nonlinear in the transition seasons, but approximately linear in the summer and winter months. 4) The internal variability of the unforced circulation exhibits a seasonal sensitivity that may partly explain the seasonal sensitivity of the forced response. The seasonality of the internal variability of daily MERRA reanalysis data is compared to that of the model, demonstrating that the broad conclusions drawn from this idealized modeling study may be useful for understanding the jet response to anthropogenic forcing.

  16. A New Precipitation Index for the Spatiotemporal Distribution of Drought and Flooding in the Reaches of the Yangtze and Huaihe Rivers and Related Characteristics of Atmospheric Circulation

    Institute of Scientific and Technical Information of China (English)

    ZONG Haifeng; ZHANG Qingyun

    2011-01-01

    Characteristics of the spatiotemporal distributions of precipitation anomalies in the reaches of the Yangtze River and Huaihe River (YHR) were studied using EOF method. Four main precipitation patterns for the YHR in summer identified by the first two modes: a region-wide flood over the entire YHR (RWF); a region-wide drought over the entire YHR (RWD); a flood in the south with a drought in the northern region of the Yangtze River (FS-DN); and a drought in the south with a flood in the northern region of the Yangtze River (DS-FN). Based on the first two modes and the actual precipitation departure percentage, a new precipitation index is defined in this paper. The typical flood/drought years associated with the various rainfall patterns defined by this precipitation index are more representative and closer to reality compared to some existing precipitation indexes which just use the area-mean precipitation or the EOF time components individually.The characteristics of atmospheric circulation in summer corresponding to the four main precipitation patterns over the YHR in summer show the features of atmospheric circulation differ in different precipitation pattern years. Although the different patterns share a common main influential circulation system, such as the blocking high over northeastern Asia, the low trough of westerly flows in the mid latitudes, the West Pacific Subtropical High (WPSH), and the high ridge over the Tibet Plateau, the difference in location and intensity of these systems can lead to different distributions of precipitation anomalies.

  17. 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

  18. The Change of North China Climate in Transient Simulations Using the IPCC SRES A2 and B2 Scenarios with a Coupled Atmosphere-Ocean General Circulation Model

    Institute of Scientific and Technical Information of China (English)

    BUHE Cholaw(布和朝鲁); Ulrich CUBASCH; LIN Yonghui(林永辉); JI Liren(纪立人)

    2003-01-01

    This paper applies the newest emission scenarios of the sulfur and greenhouse gases, namely IPCCSRES A2 and B2 scenarios, to investigate the change of the North China climate with an atmosphere-oceancoupled general circulation nodel. In the last three decades of the 21st century, the global warming enlargesthe land-sea thermal contrast, and hence, causes the East Asian summer (winter) monsoon circulation tobe strengthened (weakened). The rainfall seasonality strengthens and the summer precipitation increasessignificantly in North China. It is suggested that the East Asian rainy area would expand northward toNorth China in the last three decades of the 21st century. In addition, the North China precipitationwould increase significantly in September. In July, August, and September, the interannual variability ofthe precipitation enlarges evidently over North China, implying a risk of flooding in the future.

  19. Numerical simulation for the coupling effect of local atmospheric circulations over the area of Beijing,Tianjin and Hebei Province

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Using the model system MM5.V3 and multi-layer grid nesting technique, we have done a multi-scale numerical simulation over the area of Beijing, Tianjin and Hebei Province to analyze the temperature and wind field there and study its local circulations. The results show a coupling effect of Urban Heat Island Circulation (UHIC), Mountain Valley Breeze (MVB) and Sea Land Breeze (SLB) occurs in this area when the synoptic system is weak. The SLB can penetrate deep into the mainland for about 200 km when it is blooming. MVB can extend to south and cover almost the whole plain area in Beijing. Both MVB and SLB are diurnal periodical; meanwhile the phase of MVB drops behind that of SLB for about six hours. As a local circulation, the UHIC weakens the two circulations above, and it also has a diurnal period. As a result, the coupling effect of circulations reveals not only different features in spring-summer period and autumn-winter period in a year but also the difference between early morn- ing to noonday and afternoon to night in a day. We noted the diffusion of contamination over the area around Beijing, and found the steady presence of a transport routine of contamination over North-China throughout the year caused by the Coupling Effect mentioned above. This find is important for studying the environment pollution in this area.

  20. Heat engines and heat pumps in a hydrostatic atmosphere: How surface pressure and temperature control wind power output and circulation cell size

    CERN Document Server

    Makarieva, A M; Nefiodov, A V; Sheil, D; Nobre, A D; Shearman, P L; Li, B -L

    2015-01-01

    The gross spatial features of the atmospheric kinetic energy budget are analytically investigated. Kinetic energy generation is evaluated in a hydrostatic atmosphere where the axisymmetric circulation cells are represented by Carnot cycles. The condition that kinetic energy generation is positive in the lower atmosphere is shown to limit the poleward cell extension via a relationship between the meridional differences in surface pressure and temperature $\\Delta p_s$ and $\\Delta T_s$: an upper limit to cell size exists when $\\Delta p_s$ increases sublinearly with $\\Delta T_s$. This is the case for the Hadley cells as demonstrated here using data from MERRA re-analysis. The limited cell size necessitates the appearance of heat pumps -- circulation cells with negative work output where the low-level air moves towards colder areas. These cells consume the positive work output of heat engines -- cells where the low-level air moves towards the warmer areas -- and can in principle drive the global efficiency of atmo...

  1. Brief communication "Important role of the mid-tropospheric atmospheric circulation in the recent surface melt increase over the Greenland ice sheet"

    Science.gov (United States)

    Fettweis, X.; Hanna, E.; Lang, C.; Belleflamme, A.; Erpicum, M.; Gallée, H.

    2013-02-01

    Since 2007, there has been a series of surface melt records over the Greenland ice sheet (GrIS), continuing the trend towards increased melt observed since the end of the 1990's. The last two decades are characterized by an increase of negative phases of the North Atlantic Oscillation (NAO) favouring warmer and drier summers than normal over GrIS. In this context, we use a circulation type classification based on daily 500 hPa geopotential height to evaluate the role of atmospheric dynamics in this surface melt acceleration for the last two decades. Due to the lack of direct observations, the interannual melt variability is gauged here by the summer (June-July-August) mean temperature from reanalyses at 700 hPa over Greenland; analogous atmospheric circulations in the past show that ~70% of the 1993-2012 warming at 700 hPa over Greenland has been driven by changes in the atmospheric flow frequencies. Indeed, the occurrence of anticyclones centred over the GrIS at the surface and at 500 hPa has doubled since the end of 1990's, which induces more frequent southerly warm air advection along the western Greenland coast and over the neighbouring Canadian Arctic Archipelago (CAA). These changes in the NAO modes explain also why no significant warming has been observed these last summers over Svalbard, where northerly atmospheric flows are twice as frequent as before. Therefore, the recent warmer summers over GrIS and CAA cannot be considered as a long-term climate warming but are more a consequence of NAO variability affecting atmospheric heat transport. Although no global model from the CMIP5 database projects subsequent significant changes in NAO through this century, we cannot exclude the possibility that the observed NAO changes are due to global warming.

  2. 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)

  3. Primary study on pattern of general circulation of atmos-phere before uplift of the Tibetan Plateau in eastern Asia

    Institute of Scientific and Technical Information of China (English)

    JIANG; Xinsheng

    2001-01-01

    [1]Manabe, S., Terpstra, T. B., The effects of mountains on the general circulation of the atmosphere as identified by numeri-cal experiments, J. Atmos. Sci., 1974(31): 1-42.[2]Ruddiman, W. F., Kutzbach, J. E., Forcing of Late Cenozoic Northern Hemisphere climate by plateau uplift in Southern Asia and the American West, J. of Geophysical Research, 1989, 94(D15): 18409-18427.[3]Wang Hongzhen, Atla of the Paleogeography of China, Beijing: China Map Press, 1985.[4]Editorial Board of "Natural Geography of China" of the Chinese Academy of Sciences, Natural Geography of China, Pa-leogeography, Part one, Beijing: Science Press, 1984.[5]Editorial Board of "Natural Geography of China" of the Chinese Academy of Sciences, Natural Geography of China, Cli-mate, Beijing: Science Press, 1984.[6]Jiang Xinsheng, Chen Leyao, Li Yuwen, Cretaceous-Tertiary deserts in southwestern China and desert sedimentology, Sedimentary Facies and Palaeogeography, 1992, (5): 1-66.[7]Jiang Xinsheng, Li Yuwen, Fu Qingping, Temporal and spatial distribution of Cretaceous deserts in middle and eastern China and its climatic significance, Proc. 30th International Geological Congress, 1997, 8: 73-80.[8]Jiang Xinsheng, Li Yuwen, Sapto-temporal distribution of the Cretaceous deserts in central and eastern China and its cli-matic significance, Sedimentary Facies and Palaeogeography, 1996, 16(2): 42-51.[9]Cooke, R., Warren, A., Goudie, A., Desert Geomorphology, Landon: UCL Press, 1993.[10]Zhang Linyuan, The formation process of Qinghai-Xizang Plateau and stage division of Cenozoic climate evolution in China, in The study on the formation, evolution, environmental change and ecosystem of Qinghai-Xizang Plateau, Beijing: Science Press, 1995, 267-281.[11]Liu Dongsheng, Zhang Xinshi, Yuan Baoying, The compact of the uplifting of the Plateau to the surrounding regions, in The Formation, Evolution and Development of the Qinghai-Xizang Plateau, Guangzhou: Guangdong

  4. 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.

    2016-11-01

    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

  5. 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.

  6. 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

  7. The Role of Circulation Features on Black Carbon Transport into the Arctic in the Community Atmosphere Model Version 5 (CAM5)

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Po-Lun; Rasch, Philip J.; Wang, Hailong; Zhang, Kai; Easter, Richard C.; Tilmes, S.; Fast, Jerome D.; Liu, Xiaohong; Yoon, Jin-Ho; Lamarque, Jean-Francois

    2013-05-28

    Current climate models generally under-predict the surface concentration of black carbon (BC) in the Arctic due to the uncertainties associated with emissions, transport, and removal. This bias is also present in the Community Atmosphere Model Version 5.1 (CAM5). In this study, we investigate the uncertainty of Arctic BC due to transport processes simulated by CAM5 by configuring the model to run in an “offline mode” in which the large-scale circulations are prescribed. We compare the simulated BC transport when the offline model is driven by the meteorology predicted by the standard free-running CAM5 with simulations where the meteorology is constrained to agree with reanalysis products. Some circulation biases are apparent: the free-running CAM5 produces about 50% less transient eddy transport of BC than the reanalysis-driven simulations, which may be attributed to the coarse model resolution insufficient to represent eddies. Our analysis shows that the free-running CAM5 reasonably captures the essence of the Arctic Oscillation (AO), but some discernable differences in the spatial pattern of the AO between the free-running CAM5 and the reanalysis-driven simulations result in significantly different AO modulation of BC transport over Northeast Asia and Eastern Europe. Nevertheless, we find that the overall climatological circulation patterns simulated by the free-running CAM5 generally resembles those from the reanalysis products, and BC transport is very similar in both simulation sets. Therefore, the simulated circulation features regulating the long-range BC transport is unlikely the most important cause of the large under-prediction of surface BC concentration in the Arctic.

  8. Investigation of the relationship between very warm days in Romania and large-scale atmospheric circulation using multiple linear regression approach

    Science.gov (United States)

    Barbu, N.; Cuculeanu, V.; Stefan, S.

    2016-10-01

    The aim of this study is to investigate the relationship between the frequency of very warm days (TX90p) in Romania and large-scale atmospheric circulation for winter (December-February) and summer (June-August) between 1962 and 2010. In order to achieve this, two catalogues from COST733Action were used to derive daily circulation types. Seasonal occurrence frequencies of the circulation types were calculated and have been utilized as predictors within the multiple linear regression model (MLRM) for the estimation of winter and summer TX90p values for 85 synoptic stations covering the entire Romania. A forward selection procedure has been utilized to find adequate predictor combinations and those predictor combinations were tested for collinearity. The performance of the MLRMs has been quantified based on the explained variance. Furthermore, the leave-one-out cross-validation procedure was applied and the root-mean-squared error skill score was calculated at station level in order to obtain reliable evidence of MLRM robustness. From this analysis, it can be stated that the MLRM performance is higher in winter compared to summer. This is due to the annual cycle of incoming insolation and to the local factors such as orography and surface albedo variations. The MLRM performances exhibit distinct variations between regions with high performance in wintertime for the eastern and southern part of the country and in summertime for the western part of the country. One can conclude that the MLRM generally captures quite well the TX90p variability and reveals the potential for statistical downscaling of TX90p values based on circulation types.

  9. A new tool for evaluating the physics of coupled atmosphere-ocean variability in nature and in general circulation models

    Energy Technology Data Exchange (ETDEWEB)

    Roberts, William H.G. [University of Washington, Department of Atmospheric Sciences, Seattle, WA (United States); University of Bristol, School of Geographical Sciences, Bristol (United Kingdom); Battisti, David S. [University of Washington, Department of Atmospheric Sciences, Seattle, WA (United States)

    2011-03-15

    Intermediate models of the coupled tropical atmosphere-ocean system have been used to illuminate the physics of interannual climate phenomenon such as El Nino Southern Oscillation (ENSO) in the tropical Pacific and to explore how the tropics might respond to a forcing such as changing insolation (Milankovitch) or atmospheric carbon dioxide. Importantly, most of the intermediate models are constructed as anomaly models: models that evolve on a prescribed climatological mean state, which is typically prescribed and done so on a rather ad hoc basis. Here we show how the observed climatological mean state fields [ocean currents and upwelling, sea surface temperature (SST) and atmospheric surface winds] can be incorporated into a linearized intermediate model of the tropical coupled atmosphere-ocean system: called Linear Ocean-Atmosphere Model (LOAM), it is a linearized version of the Zebiak and Cane model. With realistic, seasonally varying mean state fields, we find that the essential physics of the ENSO mode is very similar to that in the original model and to that in the observations and that the observed mean fields support an ENSO mode that is stable to perturbations. Thus, our results provide further evidence that ENSO is generated and maintained by stochastic (uncoupled) perturbations. The method that we have outlined can be used to assimilate any set of ocean and atmosphere climatological data into the linearized atmosphere-ocean model. In a companion paper, we apply this same method to incorporate mean field output from two global climate models into the linearised model. We use the latter to diagnose the physics of the leading coupled mode (ENSO) that is supported by the climate models, and to illuminate why the structure and variance in the ENSO mode changes in the models when they are forced by early Holocene and Last Glacial Maximum boundary conditions. (orig.)

  10. Global environmental cycling of gamma-HCH and DDT in the 1980s--a study using a coupled atmosphere and ocean general circulation model.

    Science.gov (United States)

    Guglielmo, Francesca; Lammel, Gerhard; Maier-Reimer, Ernst

    2009-09-01

    A coupled atmosphere-ocean general circulation model, ECHAM5-MPIOM, was used to study the multicompartmental cycling and long-range transport of persistent and semivolatile organics. Multiphase systems in air and ocean are covered by submodels for atmospheric aerosols, HAM, and marine biogeochemistry, HAMOCC5, respectively. The model, furthermore, encompasses 2D surface compartments, i.e. top soil, vegetation surfaces and sea-ice. The total environmental fate of gamma-hexachlorocyclohexane (gamma-HCH, lindane) and dichlorophenyltrichloroethane (DDT) in agriculture were studied. DDT is mostly present in the soils, the water-soluble gamma-HCH in soils and ocean. DDT has the longest residence time in almost all compartments. Quasi-steady state with regard to substance accumulation is reached within a few years in air and vegetation surfaces. In seawater the partitioning to suspended and sinking particles contributes to the vertical transport of substances. On the global scale deep water formation is, however, found to be more efficient. Up to 30% of DDT but only less than 0.2% of gamma-HCH in seawater are stored in particulate matter. On the time scale studied (1 decade) and on global scale substance transport in the environment is determined by the fast atmospheric circulation. The meridional transport mechanism, for both compounds, is significantly enhanced by multi-hopping. Net meridional transport in the ocean is effective only regionally, mostly by currents along the western boundaries of Africa and the Americas. The total environmental burdens of the substances experience a net northward migration from their source regions, which is more pronounced for DDT than for gamma-HCH. Due to the application distribution, however, after 10 years of simulation 21% of the global environmental burden of gamma-HCH and 12% of DDT have accumulated in the Arctic.

  11. The impact of changes in parameterizations of surface drag and vertical diffusion on the large-scale circulation in the Community Atmosphere Model (CAM5)

    Science.gov (United States)

    Lu, Feiyu; Liu, Zhengyu; Liu, Yun; Zhang, Shaoqing; Jacob, Robert

    2016-08-01

    Simulations with the Community Atmosphere Model version 5 (CAM5) are used to analyze the sensitivity of the large-scale circulation to changes in parameterizations of orographic surface drag and vertical diffusion. Many GCMs and NWP models use enhanced turbulent mixing in stable conditions to improve simulations, while CAM5 cuts off all turbulence at high stabilities and instead employs a strong orographic surface stress parameterization, known as turbulent mountain stress (TMS). TMS completely dominates the surface stress over land and reduces the near-surface wind speeds compared to simulations without TMS. It is found that TMS is generally beneficial for the large-scale circulation as it improves zonal wind speeds, Arctic sea level pressure and zonal anomalies of the 500-hPa stream function, compared to ERA-Interim. It also alleviates atmospheric blocking frequency biases in the Northern Hemisphere. Using a scheme that instead allows for a modest increase of turbulent diffusion at higher stabilities only in the planetary boundary layer (PBL) appears to in some aspects have a similar, although much smaller, beneficial effect as TMS. Enhanced mixing throughout the atmospheric column, however, degrades the CAM5 simulation. Evaluating the simulations in comparison with detailed measurements at two locations reveals that TMS is detrimental for the PBL at the flat grassland ARM Southern Great Plains site, giving too strong wind turning and too deep PBLs. At the Sodankylä forest site, the effect of TMS is smaller due to the larger local vegetation roughness. At both sites, all simulations substantially overestimate the boundary layer ageostrophic flow.

  12. An East Asian land-sea atmospheric heat source difference index and its relation to general circulation and summer rainfall over China

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Using a monthly precipitation dataset of 160 stations over China and a daily and monthly National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis dataset from 1961 to 2006, we here define an East Asian land-sea atmospheric heat source difference index ILSQD and investigate its relationship to summer rainfall in China and East Asian general circulation. The results show that ILSQD more closely reflects the anomalous variations in summer monsoon phenomena; in the high-index (HI) cases, the strong low-level southerlies over East China and the strong high-level westerlies over middle latitudes indicate an active summer monsoon, and vice versa in the low-index (LI) cases. This index also reflects summer rainfall anomalies over East China; in the HI (LI) cases rainfall increases (decreases) over North China and at the same time decreases (increases) over the mid-lower Yangtze River valley and the southern Yangtze River. Hence, ILSQD can be utilized as a summer monsoon index. There is also remarkable correlation between ILSQD in March and the following summer rainfall over the mid-lower Yangtze River valley. Finally, the Community Atmospheric Model Version 3.1 (CAM3.1) of NCAR is used to run numerical experiments, which verify that the anomalous summer precipitation in simulations is similar to that of diagnosis analysis based on the anomalous summer atmospheric heating forcing. Similarly, the atmospheric heating rate in March can force summer rainfall anomalies in the simulations just as observed in the data.

  13. An investigation of a GJ 1214b-like exoplanet with a water vapor atmosphere using a simple general circulation model

    CERN Document Server

    Zalucha, Angela M; Madhusudhan, Nikku

    2012-01-01

    We present results from a simple general circulation model (GCM) of a GJ 1214b-like super-Earth exoplanet. The dynamical core of our model is a scaled-up version of a shallow atmosphere, terrestrial planet GCM that has previously been used for Mars and therefore employs different boundary conditions and physical processes than downsized gas giant models. We assume the planet is tidally locked and has the observed characteristics of GJ-1214b [Charbonneau et al. 2009] for surface mass, surface radius, orbital period, and surface gravitational acceleration. We assume the atmosphere is composed entirely of water vapor. We assume the planet has a surface (i.e., a density discontinuity at depth), which will provide a mechanical drag and affect the radiative balance at the bottom boundary. We assume a gray atmosphere in the IR. We find that a westerly jet is present aloft at the equator and that the longitude of maximum temperature is shifted eastward of the substellar point. A wavenumber-1 feature is present in the...

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

    Directory of Open Access Journals (Sweden)

    P. S. Bhattacharjee

    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

  15. Sensitivity of boreal-summer circulation and precipitation to atmospheric aerosols in selected regions. Pt. 1. Africa and India

    Energy Technology Data Exchange (ETDEWEB)

    Sud, Y.C.; Wilcox, E.; Lau, W.K.M. [NASA/Goddard Space Flight Center, Greenbelt, MD (United States). Lab. for Atmospheres; Walker, G.K. [SAIC/General Sciences Operation, Beltsville, MD (United States); Liu, X.H. [Pacific Northwest National Laboratory, Richland, WA (United States); Nenes, A. [Georgia Institute of Technology, Atlanta, GA (United States). School of Earth and Atmospheric Sciences; Lee, D. [Seoul National Univ. (Korea); Kim, K.M.; Zhou, Y. [GEST/Maryland Univ., Balitmore, MD (United States); Bhattacharjee, P.S. [George Mason Univ., VA (United States). Dept. of Geography and GeoInformation Sciences

    2009-07-01

    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 rationally in climate

  16. Seasonal variation of local atmospheric circulations and boundary layer structure in the Beijing-Tianjin-Hebei region and implications for air quality

    Science.gov (United States)

    Miao, Yucong; Hu, Xiao-Ming; Liu, Shuhua; Qian, Tingting; Xue, Ming; Zheng, Yijia; Wang, Shu

    2015-12-01

    The Beijing-Tianjin-Hebei (BTH) region experiences frequent heavy haze pollution in fall and winter. Pollution was often exacerbated by unfavorable atmospheric boundary layer (BL) conditions. The topography in this region impacts the BL processes in complex ways. Such impacts and implications on air quality are not yet clearly understood. The BL processes in all four seasons in BTH are thus investigated in this study using idealized simulations with the WRF-Chem model. Results suggest that seasonal variation of thermal conditions and synoptic patterns significantly modulates BL processes. In fall, with a relatively weak northwesterly synoptic forcing, thermal contrast between the mountains and the plain leads to a prominent mountain-plain breeze circulation (MPC). In the afternoon, the downward branch of the MPC, in addition to northwesterly warm advection, suppresses BL development over the western side of BTH. In the eastern coastal area, a sea-breeze circulation develops late in the morning and intensifies during the afternoon. In summer, southeasterly BL winds allow the see-breeze front to penetrate farther inland (˜150 km from the coast), and the MPC is less prominent. In spring and winter, with strong northwesterly synoptic winds, the sea-breeze circulation is confined in the coastal area, and the MPC is suppressed. The BL height is low in winter due to strong near-surface stability, while BL heights are large in spring due to strong mechanical forcing. The relatively low BL height in fall and winter may have exacerbated the air pollution, thus contributing to the frequent severe haze events in the BTH region.

  17. Surface water and atmospheric underway carbon data obtained during the World Ocean Circulation Experiment Indian Ocean survey cruises (R/V Knorr, December 1998--January 1996)

    Energy Technology Data Exchange (ETDEWEB)

    Kozyr, A. [Univ. of Tennessee, Knoxville, TN (United States). Energy, Environment, and Resources Center; Allison, L. [Oak Ridge National Lab., TN (United States). Carbon Dioxide Information Analysis Center

    1997-11-01

    This data documentation presents the results of the surface water and atmospheric underway measurements of mole fraction of carbon dioxide (xCO{sub 2}), sea surface salinity, and sea surface temperature, obtained during the World Ocean Circulation Experiment (WOCE) Indian Ocean survey cruises (December 1994--January 1996). Discrete and underway carbon measurements were made by members of the CO{sub 2} survey team. The survey team is a part of the Joint Global Ocean Flux Study supported by the US Department of Energy to make carbon-related measurements on the WOCE global survey cruises. Approximately 200,000 surface seawater and 50,000 marine air xCO{sub 2} measurements were recorded.

  18. The balance of kinetic and total energy simulated by the OSU two-level atmospheric general circulation model for January and July

    Science.gov (United States)

    Wang, J.-T.; Gates, W. L.; Kim, J.-W.

    1984-01-01

    A three-year simulation which prescribes seasonally varying solar radiation and sea surface temperature is the basis of the present study of the horizontal structure of the balances of kinetic and total energy simulated by Oregon State University's two-level atmospheric general circulation model. Mechanisms responsible for the local energy changes are identified, and the energy balance requirement's fulfilment is examined. In January, the vertical integral of the total energy shows large amounts of external heating over the North Pacific and Atlantic, together with cooling over most of the land area of the Northern Hemisphere. In July, an overall seasonal reversal is found. Both seasons are also characterized by strong energy flux divergence in the tropics, in association with the poleward transport of heat and momentum.

  19. Present and future connection of Asian-Pacific Oscillation to large-scale atmospheric circulations and East Asian rainfall: results of CMIP5

    Science.gov (United States)

    Zhou, Botao; Xu, Ying; Shi, Ying

    2017-03-01

    The summer Asian-Pacific oscillation (APO), one of the major modes of climate variability over the Asian-Pacific sector, has a pronounced effect on variations of large-scale atmospheric circulations and climate. This study evaluated the capability of 30 state-of-the-art climate models among the Coupled Model Intercomparison Project Phase 5 (CMIP5) in simulating its association with the atmospheric circulations over the Asian-Pacific region and the precipitation over East Asia. Furthermore, their future connections under the RCP8.5 scenario were examined. The evaluation results show that 5 out of 30 climate models can well capture the observed APO-related features in a comprehensive way, including the strengthened South Asian high (SAH), deepened North Pacific trough (NPT) and northward East Asian jet (EAJ) in the upper troposphere; an intensification of the Asian low and the North Pacific subtropical high (NPSH) as well as a northward shift of the western Pacific subtropical high (WPSH) in the lower troposphere; and a decrease in East Asian summer rainfall (EASR) under the positive APO phase. Based on the five CMIP5 models' simulations, the dynamic linkages of the APO to the SAH, NPT, AL, and NPSH are projected to maintain during the second half of the twenty-first century. However, its connection with the EASR tends to reduce significantly. Such a reduction might result from the weakening of the linkage of the APO to the meridional displacement of the EAJ and WPSH as a response to the warming scenario.

  20. Global distribution of gravity wave fields and their seasonal dependence in the Martian atmosphere simulated in a high-resolution general circulation model

    Science.gov (United States)

    Kuroda, Takeshi; Medvedev, Alexander; Yiğit, Erdal; Hartogh, Paul

    2016-10-01

    Gravity waves (GWs) are small-scale atmospheric waves generated by various geophysical processes, such as topography, convection, and dynamical instability. On Mars, several observations and simulations have revealed that GWs strongly affect temperature and wind fields in the middle and upper atmosphere. We have worked with a high-resolution Martian general circulation model (MGCM), with the spectral resolution of T106 (horizontal grid interval of ~67 km), for the investigations of generation and propagation of GWs. We analyzed for three kinds of wavelength ranges, (1) horizontal total wavenumber s=21-30 (wavelength λ~700-1000 km), (2) s=31-60 (λ~350-700 km), and (3) s=61-106 (λ~200-350 km). Our results show that shorter-scale harmonics progressively dominate with height during both equinox and solstice. We have detected two main sources of GWs: mountainous regions and the meandering winter polar jet. In both seasons GW energy in the troposphere due to the shorter-scale harmonics is concentrated in the low latitudes in a good agreement with observations. Orographically-generated GWs contribute significantly to the total energy of disturbances, and strongly decay with height. Thus, the non-orographic GWs of tropospheric origin dominate near the mesopause. The vertical fluxes of wave horizontal momentum are directed mainly against the larger-scale wind. Mean magnitudes of the drag in the middle atmosphere are tens of m s-1 sol-1, while instantaneously they can reach thousands of m s-1 sol-1, which results in an attenuation of the wind jets in the middle atmosphere and in tendency of their reversal.

  1. The middle atmospheric circulation of a tidally locked Earth-like planet and the role of the sea surface temperature

    Science.gov (United States)

    Proedrou, Elisavet; Hocke, Klemens; Wurz, Peter

    2016-12-01

    We investigate the influence of the sea surface temperature (SST) changes on the middle atmosphere of a tidally locked Earth-like planet orbiting a G star using the coupled 3D chemistry-climate model CESM1(WACCM). We perform three 90 day simulations. The first simulation is a present-day Earth (PDE) simulation, the second is a simulation of a tidally locked Earth-like planet with a tidally locked aquaplanet sea surface temperature (cold TLE (CLTE)) and the third is a hybrid simulation of a tidally locked Earth-like planet with a present-day Earth sea surface temperature (warm TLE (WTLE)). Our results show that changes in the SST have an influence on the lower stratospheric temperature and the secondary ozone layer. Both atmospheres exhibit a dayside upwelling and a nightside downwelling extending from the surface to the mesosphere. They are also characterised by comparable lower and middle stratospheric horizontal winds and relatively different mesospheric horizontal winds. The temperature of the WTLE atmosphere is altered as a result of the SST changes, compared to the CTLE. Specifically, the WTLE lower tropospheric temperature is increased by 3.7 K on average, due to the absorption of the increased upwelling longwave radiation and the increased sensible and latent heat. The WTLE upper troposphere temperature is decreased by 4 K on average, is adiabatic in nature, and is generated by the increased WTLE upwelling. The WLTE lower stratospheric temperature is increased by 3.8 K on average due to the absorption of the increased upwelling longwave radiation. The lower mesospheric temperature is decreased by 1.13 K on average due to increased mesospheric wave breaking. The upper mesospheric temperature is increased by 4.3 K, and its generation mechanism is currently unknown. Furthermore, the secondary ozone volume mixing ratio is increased by 40.5 %. The occurrence of large-scale vortices and variable jet streams depends, to some extent, on the SST distribution.

  2. Progress Toward a New/Modern Nonhydrostatic Mars General Circulation Model: Adapting MPAS-A to Study the Atmosphere of Mars

    Science.gov (United States)

    Tyler, Daniel; Barnes, Jeffrey R.

    2016-10-01

    As the database of observations of the Martian atmosphere grows to considerable size and depth, atmospheric modeling becomes more constrained. Improved models and modeling techniques are needed to maintain the scientifically productive interaction between the two specialities. We have begun a process of adapting the nonhydrostatic state-of-the-art atmospheric model for prediction across scales (MPAS-A) to study the atmosphere of Mars. Useful descriptions and references can be found at ( https://mpas-dev.github.io/ ). The key features of this model are: 1) it is global and nonhydrostatic, 2) in its basic configuration it has isotropic spatial resolution that is not hindered by a 'pole problem' as are many GCMs, 3) it is designed to be and is typically run with regions of refined resolution (allowing for true mesoscale simulations, without nest boundary issues, while being forced globally in a fully consistent fashion). Initial testing of the model under Mars conditions has been performed: with Mars topography and surface pressure, at a spatial resolution of ~60 km, and with air temperatures relaxed to a 3-D temperature field for a moderately high dust loading at winter solstice in either hemisphere. Results are fascinatingly complex, and depict a good overall agreement with the expected zonal-mean circulation under these conditions. The model is being run on Pleiades at the NAS supercomputing facility at NASA/Ames, where tests using various numbers of processor cores reveal a near-linear scalability (the decrease in elapsed wall-clock time to the number of cores). Having completed this initial testing phase, we expect to present results where the model is being run: 1) with a simple atmospheric radiation scheme, 2) with realistic surface properties and a soil model, and 3) with a capable PBL scheme. Upon reaching that point in development, we will be able to compare and contrast results from our mission-support modeling efforts for both the Mars 2020 and Insight

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

    Directory of Open Access Journals (Sweden)

    A. Pozzer

    2007-05-01

    Full Text Available 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 simulation and apply a statistical analysis using data from numerous field campaigns. The results serve as a basis for future improvements of the model system. ECHAM5/MESSy1 generally reproduces the spatial distribution and the seasonal cycle of carbon monoxide (CO very well. However, for the background in the Northern Hemisphere we obtain a negative bias (mainly due to an underestimation of emissions from fossil fuel combustion, and in the high latitude Southern Hemisphere a yet unexplained positive bias. The model results agree well with observations of alkanes, whereas severe problems in the simulation of alkenes and isoprene are present. For oxygenated compounds the results are ambiguous: The model results are in good agreement with observations of formaldehyde, but systematic biases are present for methanol and acetone. The discrepancies between the model results and the observations are explained (partly by means of sensitivity studies.

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

    Directory of Open Access Journals (Sweden)

    A. Pozzer

    2007-01-01

    Full Text Available 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 simulation and apply a statistical analysis using data from numerous field campaigns. The results serve as a basis for future improvements of the model system. ECHAM5/MESSy1 generally reproduces the spatial distribution and the seasonal cycle of carbon monoxide (CO very well. However, for the background in the northern hemisphere we obtain a negative bias (mainly due to an underestimation of emissions from fossil fuel combustion, and in the high latitude southern hemisphere a yet unexplained positive bias. The model results agree well with observations of alkanes, whereas severe problems in the simulation of alkenes are present. For oxygenated compounds the results are ambiguous: The model results are in good agreement with observations of formaldehyde, but systematic biases are present for methanol and acetone. The discrepancies between the model results and the observations are explained (partly by means of sensitivity studies.

  5. Model Evaluation and Projection on the Linkage between Hadley Circulation and Atmospheric Background Related to the Tropical Cyclone Frequency over the Western North Pacific

    Institute of Scientific and Technical Information of China (English)

    ZHOU Bo-Tao

    2012-01-01

    The performance of climate models in simulating the linkage of the spring Hadley circulation (HC) to the vertical zonal wind shear and atmospheric divergence in the lower and upper troposphere, which are related to the tropical cyclone frequency over the western North Pacific (WNPTCF) during June–September (JJAS), is evaluated on the basis of the 20th century climate simulations (20C3M). It is found that four models can simulta-neously reproduce the pattern revealed in the observation, with the spring HC in the Northern Hemisphere being positively correlated to the vertical zonal wind shear in the major tropical cyclone (TC) genesis region and negatively (positively) correlated to the atmospheric diver- gence in the upper (lower) troposphere over the western North Pacific (WNP) in the following JJAS. These four models are further used to project their relationship in the late 21st century under the A1B scenario. The results show that the association of spring HC with the vertical zonal wind shear and the upper-and lower-tropospheric divergence over the WNP will weaken in the late 21st century, thereby resulting in a weak relationship between the spring HC and the JJAS WNPTCF.

  6. 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.

  7. 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

  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. Stable isotopic evidence of El Niño-like atmospheric circulation in the Pliocene Western United States

    Directory of Open Access Journals (Sweden)

    M. J. Winnick

    2012-10-01

    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.

  10. 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.

  11. A 1,000-year ice core record of interannual to multidecadal variations in atmospheric circulation over the North Atlantic

    Energy Technology Data Exchange (ETDEWEB)

    Fischer, Hubertus; Mieding, Birgit [Alfred Wegener Institute for Polar and Marine Research, Bremerhaven (Germany)

    2005-07-01

    Interannual to multidecadal modes in ocean/atmosphere dynamics in the North Atlantic region have been identified using sea salt aerosol proxy records from northern Greenland ice cores over the last 1,000 years. Sea salt concentrations show a consistent relationship with anomalies in the meridional pressure gradient over the North Atlantic region over all considered time scales. These pressure anomalies are connected to shifts in storm tracks, leading to lower pressure and higher storm activity, hence, higher sea salt export over the Greenland ice sheet. Two modes of long-term variability with a period of 10.4 years and 62 years could be identified. The latter is connected to long-term changes in sea surface temperature (SST) as documented by a high correlation of North Atlantic SST with our sea salt record over the last 150 years. Long-term reconstruction of these modes shows that the 10.4-year cycle has been a phenomenon persistent over the last millennium while the 62-year cycle has been mainly active after 1700. Accordingly, the longer-term persistence of this multidecadal variability in sea salt points also to significant variations in SST over the last 300 years. (orig.)

  12. 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.

  13. A Proposed Link Between Atmospheric Circulation and Stable Oxygen Isotope Values From Tree-Ring Cellulose, Fayetteville Green Lake, New York.

    Science.gov (United States)

    Kirby, M. E.; Anderson, W.; Mullins, H.; Burnett, A.

    2002-12-01

    Very few paleoclimate proxy records exist which highlight the relationship between atmospheric circulation patterns and stable oxygen isotopes of precipitation for the Northeastern United States. Here, we present the initial stable oxygen isotope results (n=55) from cellulose extracted from a 140-yr tree-ring record (Yellow-Poplar; Liriodendron tulipifera). Located within the drainage basin of Fayetteville Green Lake (Fayetteville, NY), this specimen was felled during a wind-storm on Labor Day 1998. A whole-diameter tree-slab was removed for tree-ring counts and cellulose extraction. Comparison of the tree-ring cellulose stable oxygen isotope values to spring average temperature and mean latitude of the spring season polar vortex (measured at the 500 hPa geopotential height between 85W and 60W longitude) reveal intriguing relationships. d18O cellulose values are correlated to both the latitude of the spring season vortex (r=0.61; alpha=0.1) and the spring season average temperature (r=0.47; alpha=0.1). The correlation between spring season latitude and the average spring season temperature is also statistically significant (r=0.74; alpha=0.1). From these data, we propose an atmospheric circulation-water stress hypothesis to explain the d18O cellulose values between 1943 and 1998 AD. A contracted (i.e., higher latitudes) spring season vortex produces warmer average spring season temperatures by reducing the frequency of excursions of cold air masses into the middle latitudes. As the temperature of the spring season increases, the rate of evapotranspiration similarly increases leading to the preferential removal of 16O from the tree leaf via increased water stress. As a result, the cellulose subsequently produced has higher average oxygen isotope values. Comparison of the cellulose d18O data to calcite d18O values obtained from nearby Fayetteville Green Lake (about 100m NE from the tree site) for overlapping intervals show intriguing similarities and dissimilarities

  14. 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.

  15. Simulated changes in vegetation distribution, land carbon storage, and atmospheric CO{sub 2} in response to a collapse of the North Atlantic thermohaline circulation

    Energy Technology Data Exchange (ETDEWEB)

    Koehler, Peter [Alfred Wegener Institute for Polar and Marine Research, Bremerhaven (Germany); Joos, Fortunat [University of Bern (Switzerland). Climate and Environmental Physics Institute; Gerber, Stefan [University of Bern (Switzerland). Climate and Environmental Physics Institute; Princeton University, NJ (United States); Knutti, Reto [University of Bern (Switzerland). Climate and Environmental Physics Institute; National Center for Atmospheric Research, Boulder, CO (United States)

    2005-12-01

    It is investigated how abrupt changes in the North Atlantic (NA) thermohaline circulation (THC) affect the terrestrial carbon cycle. The Lund-Potsdam-Jena Dynamic Global Vegetation Model is forced with climate perturbations from glacial freshwater experiments with the ECBILT-CLIO ocean-atmosphere-sea ice model. A reorganisation of the marine carbon cycle is not addressed. Modelled NA THC collapses and recovers after about a millennium in response to prescribed freshwater forcing. The initial cooling of several Kelvin over Eurasia causes a reduction of extant boreal and temperate forests and a decrease in carbon storage in high northern latitudes, whereas improved growing conditions and slower soil decomposition rates lead to enhanced storage in mid-latitudes. The magnitude and evolution of global terrestrial carbon storage in response to abrupt THC changes depends sensitively on the initial climate conditions. These were varied using results from time slice simulations with the Hadley Centre model HadSM3 for different periods over the past 21 kyr. Changes in terrestrial storage vary between -67 and +50 PgC for the range of experiments with different initial conditions. Simulated peak-to-peak differences in atmospheric CO{sub 2} are 6 and 13 ppmv for glacial and late Holocene conditions. Simulated changes in {delta}{sup 13}C are between 0.15 and 0.25 permille. These simulated carbon storage anomalies during a NA THC collapse depend on their magnitude on the CO{sub 2} fertilisation feedback mechanism. The CO{sub 2} changes simulated for glacial conditions are compatible with available evidence from marine studies and the ice core CO{sub 2} record. The latter shows multi-millennial CO{sub 2} variations of up to 20 ppmv broadly in parallel with the Antarctic warm events A1 to A4 in the South and cooling in the North. (orig.)

  16. An Atmospheric General Circulation Model with Chemistry for the CRAY T3E: Design, Performance Optimization and Coupling to an Ocean Model

    Science.gov (United States)

    Farrara, John D.; Drummond, Leroy A.; Mechoso, Carlos R.; Spahr, Joseph A.

    1998-01-01

    The design, implementation and performance optimization on the CRAY T3E of an atmospheric general circulation model (AGCM) which includes the transport of, and chemical reactions among, an arbitrary number of constituents is reviewed. The parallel implementation is based on a two-dimensional (longitude and latitude) data domain decomposition. Initial optimization efforts centered on minimizing the impact of substantial static and weakly-dynamic load imbalances among processors through load redistribution schemes. Recent optimization efforts have centered on single-node optimization. Strategies employed include loop unrolling, both manually and through the compiler, the use of an optimized assembler-code library for special function calls, and restructuring of parts of the code to improve data locality. Data exchanges and synchronizations involved in coupling different data-distributed models can account for a significant fraction of the running time. Therefore, the required scattering and gathering of data must be optimized. In systems such as the T3E, there is much more aggregate bandwidth in the total system than in any particular processor. This suggests a distributed design. The design and implementation of a such distributed 'Data Broker' as a means to efficiently couple the components of our climate system model is described.

  17. Influence of runoff, high frequency atmospheric forcing and model resolution on deep water mass formation regions and Atlantic Meridional Overturning Circulation, from a numerical model.

    Science.gov (United States)

    Garcia Quintana, Yarisbel; Courtois, Peggy; Hu, Xianmin; Pennelly, Clark; Myers, Paul G.

    2016-04-01

    Water mass formation regions act as windows to the deep ocean where surface waters are transformed to intermediate and deep waters. Within the North Atlantic, Labrador Sea Water (LSW) is convectively produced in the Labrador Sea while in the Nordic Seas the source waters for Denmark Strait Overflow Water (DSOW) and Iceland-Scotland Overflow Water (NEADW) are formed. They are the main components of the North Atlantic Deep Water (NADW) which forms the lower limb of the Atlantic Meridional Overturning Circulation (AMOC). We explore the changes of the LSW formation rates and in AMOC strength as consequence of runoff glacial melt, high frequency atmospheric forcing influence and variations in model's resolution. We use 1/4° resolution Arctic and Northern Hemisphere Atlantic (ANHA4) configuration from the Nucleus for European Modelling of the Ocean (NEMO) model. A nest using ANHA4 and the Adaptive Grid Refinement in FORTRAN (AGRIF) package was used to increase the resolution to 1/12° in the sub-polar gyre. The formation rate is calculated based upon a kinematic subduction approach where the exchange through the dynamic mixed layer base is calculated based on shallowing and deepening in the mixed layer, and convergence of horizontal transport into or out of the mixed layer. Lastly we use a Lagrangian tool (Ariane) to track the path of the DSOW and the NEADW from their formation source.

  18. An 80-year summer temperature history from the Xiao Dongkemadi ice core in the central Tibetan Plateau and its association with atmospheric circulation

    Science.gov (United States)

    Li, Xiangying; Ding, Yongjian; Yu, Zhongbo; Mika, Sillanpää; Liu, Shiyin; Shangguan, Donghui; Lu, Chengyang

    2015-02-01

    The climate significance of oxygen isotopes from the central Tibetan Plateau (cTP) ice cores is a debated issue because of large scale atmospheric circulation. A high-resolution δ18O record was recovered from the Xiao Dongkemadi (XD) ice core, which expanded the spatial coverage of δ18O data in this region. Annual average δ18O correlated significantly with nearby MJJAS air temperatures, suggesting the δ18O can be used as a proxy to reconstruct regional climate change. The reconstructed temperature anomaly is related to the regional and global warming trends, and the greater warming amplitude since 1970s is related to the elevation dependency of the warming signal. The close relationship of the warming to variations in glacier mass balances and discharge reveal that recent warming has led to obvious glacier shrinkage and runoff increase. Correlation analysis suggests that monsoon and westerly moisture substantially influence the cTP ice core records, along with an increase in their level of contribution to the XD core accumulation in recent decades, and confirms a teleconnection of regional climate of the cTP ice cores with climate parameters in the Indian and North Atlantic Oceans.

  19. Responses of the summer Asian-Pacific zonal thermal contrast and the associated evolution of atmospheric circulation to transient orbital changes during the Holocene

    Science.gov (United States)

    Xiao, Dong; Zhao, Ping; Wang, Yue; Zhou, Xiuji

    2016-01-01

    This study investigates the response of large-scale atmospheric circulation over the Asian-Pacific sector and precipitation over eastern China to transient orbital changes during the Holocene summer using an intermediate-complexity climate model. Corresponding to variations in the incoming solar radiation, the eddy sea level pressure (SLP) exhibited an out-of-phase relationship between the North Pacific and the Eurasian landmass that was similar to the present-day Asia-Pacific Oscillation (APO) pattern and was defined as the paleo-APO. Its index presented an increasing trend, which implies the enhancement of a zonal thermal contrast between Asia and the North Pacific. Associated with the strengthening of the paleo-APO was the westward shift in North Pacific high pressure. Accordingly, there was less/more summer precipitation over both the middle reach of the Yangtze River and Southwest China/over North China. The high-resolution stalagmite δ18O records further support this decrease in the model precipitation. Along with the strengthening of paleo-APO from the early Holocene to the present, the eddy SLP anomalies exhibited a decreasing/increasing trend over the Eurasian landmass/the North Pacific, with a phase change of approximately 4.5 ka BP, and they both moved westward. Meanwhile, a less rainfall belt over eastern China exhibited northward propagation from southern China. PMID:27779217

  20. 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

  1. Analysis of the August 2011 Atmospheric Circulation and Weather%2011年8月大气环流和天气分析

    Institute of Scientific and Technical Information of China (English)

    吕心艳

    2011-01-01

    2011年8月环流特征如下:极涡呈现2个中心,强度偏弱。北半球中高纬度环流呈4波型分布,副热带高压脊线偏南,中旬西伸脊线点偏西,强度略偏强。2011年8月,全国平均气温为21.3℃,较常年同期(20.3℃)偏高1.0℃。全国平均降水量为85.7 mm.平均降水量偏少16.5%。月内出现了10次降水过程,西北太平洋有4个热带风暴活动,其中"南玛都"登陆我国台湾省和福建省,超强台风梅花对我国东部大范围沿海造成了较大影响。江南大部、华南北部及重庆、四川东部等地持续高温天气。%The following are the main characteristics of the general atmospheric circulation in August 2011. There are two polar vortex centers in the Northern Hemisphere and the intensity of the polar vortex is much weaker than normal.The circulation presents a four-wave pattern in the middle-high latitudes.In comparison with the states of normal years,the ridge of the subtropical high is further south,while the western ridge spot is further west and the intensity of the subtropical high is a little stronger in August 2011.The monthly mean temperature(21.3℃) is 1.0℃higher than the same period of normal years.The nationwide mean precipitation(85.7 mm) is 16.5%less than normal.There are 10 precipitation processes and 4 tropical storms occurring in the western North Pacific,the typhoon "Nanmadol" landed Taiwan and Fujian and super typhoon "Muifa" affected the larger region of eastern China.The high temperature is continuing for many days in south of the Yangtze River,the northern South China,east of Sichuan and Chongqing.

  2. 2012年8月大气环流和天气分析%Analysis of the August 2012 Atmospheric Circulation and Weather

    Institute of Scientific and Technical Information of China (English)

    陶亦为

    2012-01-01

    2012年8月环流特征如下:北半球极涡呈单极型分布,中心略偏于东半球,强度较常年偏强;北半球高纬度环流呈5波型分布;西太平洋副热带高压较常年偏北偏西。2012年8月,全国平均气温为21.4℃,较常年同期(20.8℃)偏高0.6℃。全国平均降水量92.1mm,较常年同期(105.1mm)偏少12.4%。月内共出现8次降水过程;西北太平洋有7个热带气旋活动,有5个热带气旋登陆我国,另外,热带气旋布拉万对我国东北地区造成严重影响;江南、华南、江汉、四川盆地及新疆等地出现高温天气;19个省(市、区)遭受风雹灾害。%The following are the main characteristics of the general atmospheric circulation in August 2012. There was one polar vortex center in the Northern Hemisphere and its intensity is stronger than normal. The circulation presents a five-wave pattern in the middle-high latitudes. In comparison with the sates of normal years, the western ridge spot of West Pacific subtropical high is further west and north. The monthly mean temperature is 21.4℃, and is 0.6℃ higher than normal (20.8℃). The monthly mean pre- cipitation is 92.1 rnm, and is 12.4% less than normal (105.1 mm). There are 8 precipitation processes, and 7 tropical cyclones have acted in the western North Pacific. There are 5 tropical cyclones landed China. Besides, tropical cyclone "Bolaven" seriously affected Northeast of China. Extreme high temperature weather occurred in areas of Jiangnan, Huanan, Jianghan, Sichuan Basin and Xinjiang. The hail storm dis- asters happened in 19 provinces, regions and cities in China.

  3. 2012年9月大气环流和天气分析%Analysis of the September 2012 Atmospheric Circulation and Weather

    Institute of Scientific and Technical Information of China (English)

    钱奇峰

    2012-01-01

    2012年9月环流特征如下:北半球高纬度地区极涡呈单极型分布,中心略偏于西半球,北半球高纬度环流呈5波型分布,槽区分别位于亚洲西部、亚洲东部、太平洋中部、北美洲东部和欧洲西部。月内,西太平洋副热带高压西脊点位置变化较大,强度比常年同期偏强。9月,全国平均气温为16.6℃,与常年同期持平,全国平均降水量73.8mm,较常年同期(65.2mm)偏多13.2%。月内共出现6次降水过程,西北太平洋有3个热带气旋活动,没有热带气旋在我国登陆。北方多地出现低温冷冻灾害,16个省(区)遭受风雹灾害。%The following are the main characteristics of the general atmospheric circulation in September 2012. The polar center over the Northern Hemisphere is a single-vortex pattern and deviated to the West- ern Hemisphere. The circulation presents a five-wave pattern in the middle-high latitudes and the trough areas are over the east part of Asia, the west part of Asia, the middle part of the Pacific, the east part of North America and the west part of Europe, respectively. The intensity of the subtropical high is slightly stronger than normal years, and its western ridge spot has large variation during September. The monthly mean temperature (16.6℃) is nearly the same as the value of normal years. The mean precipitation (73.8 mm) is 13.2% more than normal (65.2 mm). There are six precipitation processes and three tropical cy- clones generated in the western North Pacific with none landed in China. In this month, freezing calamity occurred in several northern provinces of China and sixteen provinces (regions, cities) suffered from strong wind and hail disasters.

  4. Dynamics of large-scale atmospheric circulation over Siberia using NCEP/DOE AMIP-II reanalysis data and synoptic maps

    Science.gov (United States)

    Podnebesnykh, Nataliya

    2014-05-01

    Dynamics of large-scale atmospheric circulation over Siberia using NCEP/DOE AMIP-II reanalysis data and synoptic maps Podnebesnykh N.V., Ippolitov I.I. Institute of Monitoring of Climatic and Ecological Systems SB RAS 634055, Tomsk, 10/3 Academichesky Ave. In this paper a comparative analysis of cyclones and anticyclones characteristics, which defined circulation conditions over Siberia (50-70°W, 60-110°N) in the period of 1976-2011 was carried out using synoptic maps and NCEP/DOE AMIP II reanalysis data. The analysis has shown the ambiguous relationships in the results of the comparison. The number of cyclones and anticyclones, obtained from synoptic maps exceeds on an average by 1.2 times the number of pressure formations, determined from reanalysis data. This tendency is, probably, due to the fact that in general NCEP/DOE AMIP-II reanalysis data, like other reanalysis datasets, represents large pressure systems better than small systems. Such result is in a good agreement with studies of other authors. The pressure in the cyclonic centers varies from 996.7 to 1006.0 hPa using synoptic maps and from 992.4 to 1000.3 hPa using reanalysis data. As for anticyclones the pressure in the centers varies from 1026.3 to 1034.2 hPa and 1022.9-1028.1 hPa according to synoptic maps and reanalysis data, respectively. The average pressure in the cyclonic centers for the period of 1976-2006 was 1000.9 hPa (σ = 2.0 hPa) according to synoptic maps, and 996.6 hPa (σ = 1.9 hPa) according to reanalysis data. The average pressure in the anticyclonic centers was 1029.9 hPa (σ = 1.8 hPa) and 1026.0 hPa (σ = 1.4 hPa), respectively. Therefore, cyclones, obtained by synoptic maps, are not deep and anticyclones are more intensive in comparison with pressure formations from reanalysis data. The average annual number of days with cyclones over the territory of under study is less than that with anticyclones, i.e. during the period of 1976-2006 anticyclonic weather conditions dominated

  5. Tsengwen Reservoir Watershed Hydrological Flood Simulation Under Global Climate Change Using the 20 km Mesh Meteorological Research Institute Atmospheric General Circulation Model (MRI-AGCM

    Directory of Open Access Journals (Sweden)

    Nobuaki Kimura

    2014-01-01

    Full Text Available Severe rainstorms have occurred more frequently in Taiwan over the last decade. To understand the flood characteristics of a local region under climate change, a hydrological model simulation was conducted for the Tsengwen Reservoir watershed. The model employed was the Integrated Flood Analysis System (IFAS, which has a conceptual, distributed rainfall-runoff analysis module and a GIS data-input function. The high-resolution rainfall data for flood simulation was categorized into three terms: 1979 - 2003 (Present, 2015 - 2039 (Near-future, and 2075 - 2099 (Future, provided by the Meteorological Research Institute atmospheric general circulation model (MRI-AGCM. Ten extreme rainfall (top ten events were selected for each term in descending order of total precipitation volume. Due to the small watershed area the MRI-AGCM3.2S data was downsized into higher resolution data using the Weather Research and Forecasting Model. The simulated discharges revealed that most of the Near-future and Future peaks caused by extreme rainfall increased compared to the Present peak. These ratios were 0.8 - 1.6 (Near-future/Present and 0.9 - 2.2 (Future/Present, respectively. Additionally, we evaluated how these future discharges would affect the reservoir¡¦s flood control capacity, specifically the excess water volume required to be stored while maintaining dam releases up to the dam¡¦s spillway capacity or the discharge peak design for flood prevention. The results for the top ten events show that the excess water for the Future term exceeded the reservoir¡¦s flood control capacity and was approximately 79.6 - 87.5% of the total reservoir maximum capacity for the discharge peak design scenario.

  6. 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.

  7. Evaluation of the efficiency and accuracy of new methods for atmospheric opacity and radiative transfer calculations in planetary general circulation model simulations

    Science.gov (United States)

    Zube, Nicholas Gerard; Zhang, Xi; Natraj, Vijay

    2016-10-01

    General circulation models often incorporate simple approximations of heating between vertically inhomogeneous layers rather than more accurate but computationally expensive radiative transfer (RT) methods. With the goal of developing a GCM package that can model both solar system bodies and exoplanets, it is vital to examine up-to-date RT models to optimize speed and accuracy for heat transfer calculations. Here, we examine a variety of interchangeable radiative transfer models in conjunction with MITGCM (Hill and Marshall, 1995). First, for atmospheric opacity calculations, we test gray approximation, line-by-line, and correlated-k methods. In combination with these, we also test RT routines using 2-stream DISORT (discrete ordinates RT), N-stream DISORT (Stamnes et al., 1988), and optimized 2-stream (Spurr and Natraj, 2011). Initial tests are run using Jupiter as an example case. The results can be compared in nine possible configurations for running a complete RT routine within a GCM. Each individual combination of opacity and RT methods is contrasted with the "ground truth" calculation provided by the line-by-line opacity and N-stream DISORT, in terms of computation speed and accuracy of the approximation methods. We also examine the effects on accuracy when performing these calculations at different time step frequencies within MITGCM. Ultimately, we will catalog and present the ideal RT routines that can replace commonly used approximations within a GCM for a significant increase in calculation accuracy, and speed comparable to the dynamical time steps of MITGCM. Future work will involve examining whether calculations in the spatial domain can also be reduced by smearing grid points into larger areas, and what effects this will have on overall accuracy.

  8. Fetal Circulation

    Science.gov (United States)

    ... Peripheral Artery Disease Venous Thromboembolism Aortic Aneurysm More Fetal Circulation Updated:Oct 18,2016 click to enlarge The ... fetal heart. These two bypass pathways in the fetal circulation make it possible for most fetuses to survive ...

  9. 2011年9月大气环流和天气分析%Analysis of the September 2011 Atmospheric Circulation and Weather

    Institute of Scientific and Technical Information of China (English)

    曹越男

    2011-01-01

    The following are the main characteristics of the general circulation of atmosphere in September 2011.The polar center over the Northern Hemisphere is a single-vortex pattern and deviated to the Western Hemisphere.The circulation presents a five-wave pattern in middle-high latitudes and the trough areas are over the northeast part of North Pacific,the east part of North America,the north part of North Atlantic, the east part of Europe and the northeast part of Asia,respectively.A negative anomaly with more than 160 gpm difference is found over the northeast part of North Pacific on the 500 hPa geopotential height field.The intensity of the subtropical high over the Northwest Pacific is weaker than the corresponding period of normal years.The location of west ridge spot is further east and north than normal years.The monthly mean temperature(16.4℃) is 0.4℃higher than the same period of normal years and the mean precipitation(65.0 mm) is nearly the same as the value(65.3 mm) of normal years.In this month,there were 3 obvious cold air processes and 7 precipitation processes,7 tropical cyclones generated, in which typhoon Nesat landed in China and resulted in heavy damages.%2011年9月大气环流主要特征如下:极涡呈单极型,中心略偏向西半球,中高纬度环流呈5波形分布,槽区分别位于北太平洋东北部、北美洲东部、北大西洋北部、欧洲东部、亚洲东北部。北太平洋东北部上空500 hPa高度场上有160 gpm的负距平。西北太平洋副热带高压面积较常年同期偏小,强度偏弱,西脊点位置偏东,脊线偏北。2011年9月全国平均气温16.4℃,比常年同期(16.0℃)偏高0.4℃;全国降水量为65.0 mm,接近常年同期(65.3 mm)。月内出现了3次较明显的冷空气过程和7次降水过程,有7个台风生成,其中"纳沙"登陆我国,造成重大灾害。

  10. 2013年11月大气环流和天气分析%Analysis of the November 2013 Atmospheric Circulation and Weather

    Institute of Scientific and Technical Information of China (English)

    赖芬芬; 何立富

    2014-01-01

    The main characteristics of the general atmospheric circulation in November 2013 are as follows. There is one polar vortex center located in the Arctic Circle in the Northern Hemisphere with stronger strength than normal years.The circulation presents latitudinal patterns in middle and high latitudes.The average south branch trough is located around 80°E.The subtropical high is stronger than normal years, located more westward and northward.The monthly mean precipitation is 22.5 mm,19.7%more than the normal (18.8 mm).The monthly mean temperature is 3.6℃,0.7℃ higher than the normal (2.9℃). There are three cold air processes and six heavier rainfall processes during this month.The Northeast Re-gion suffers from extreme snows twice and some places are hit by snowstorm or blizzards.Tropical cyclone“Haiyan”brings gale and heavy rains to South China.There are obvious rainfalls in the northern winter wheat region and the Jiangnan Region.Meanwhile,the fog and the haze appear in the central and eastern China due to the weak cold airs.The monthly mean fog and haze days are 4.3 days,which is the maximum record since 1 9 6 1 .%提2013年11月大气环流主要特征是:北半球极涡呈单极型分布,主体位于北极圈内,强度较常年同期偏强;欧亚中高纬环流经向度较小;南支槽平均位置大致位于80°E附近,同时,副热带高压较常年同期偏强,位置偏西、偏北。11月,全国平均降水量为22.5 mm,较常年同期(18.8 mm)偏多19.7%。全国平均气温为3.6℃,较常年同期(2.9℃)偏高0.7℃。月内,我国出现3次冷空气过程和6次较强降水过程。东北地区出现了两次强降雪过程,部分地区出现暴雪到大暴雪;台风海燕给华南地区带来较大风雨影响;北方冬麦区及江南大部出现明显降水,干旱缓解;由于冷空气势力弱,中东部地区雾霾天气频发,全国平均雾霾日数为4.3天,为1961年以来历史同期最多。

  11. Analysis of dry/wet conditions in the Gan River Basin, China, and their association with large-scale atmospheric circulation

    Science.gov (United States)

    Zhang, Yuqing; You, Qinglong; Lin, Houbo; Chen, Changchun

    2015-10-01

    Droughts and floods are natural phenomena that occur when water availability is significantly below or above normal levels over a specific period. In recent years, the Gan River Basin has frequently been threatened by droughts and floods, and it is important to evaluate the characteristics of dry/wet conditions for better water resource management and disaster mitigation in this region. On the basis of precipitation and temperature data for the period 1964-2013 from 40 meteorological stations across the basin, the variability of dry/wet conditions was analyzed using the standardized precipitation evapotranspiration index (SPEI). In addition, the standardized streamflow index (SSI) and large-scale atmospheric circulation patterns calculated from NCEP/NCAR reanalysis data were used to further explore and evaluate temporal variations, spatial patterns, and possible mechanism responsible for the formation of dry/wet conditions in the basin. The results indicated that robust coefficients between monthly SSI and SPEI exist at multiple timescales. The best correlation coefficients were found at timescales of 2-3 months, which better reflect the intensity and magnitude of seasonal dry/wet conditions. Application of a 3-month SPEI for the dry (July-September) and wet (April-June) seasons indicated that severe dry/wet episodes were easy to occur in the northern part of the basin. The difference between composites of anomalous dry/wet seasons shows that both a positive height anomaly at 500 hPa and a very little water vapor flux influence the basin during the dry season of anomalous years, which can lead to the occurrence of drought events in the basin. However, during the wet season of anomalous years, geopotential height anomalies caused by areas of high pressure in the south (South China Sea) and areas of low pressure in the north (Mongolia), are responsible for the transport of copious amounts of water vapor from both the Bay of Bengal and the South China Sea. Under these

  12. 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

  13. 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

  14. 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.

  15. Nearshore circulation

    NARCIS (Netherlands)

    Battjes, J.A.; Sobey, R.J.; Stive, M.J.F.

    1990-01-01

    Shelf circulation is driven primarily by wind- and tide-induced forces. It is laterally only weakly constrained so that the geostrophic (Coriolis) acceleration is manifest in the response. Nearshore circulation on the other hand is dominated by wave-induced forces associated with shallow-water. wave

  16. The role of large-scale atmospheric circulation in the formation of temperature anomalies in surface waters as illustrated by the northern part of the Pacific Ocean

    Science.gov (United States)

    Sorkina, A. I.

    1975-01-01

    One important reason for thermal anomalies in the ocean is the dynamic action of anomalous wind systems that set masses of surface water in motion; predominant longitudinal transport of water and air leads to a significant redistribution of cold and warm waters. Heat exchange between the ocean and atmosphere plays an additional role in the formation of water temperature anomalies.

  17. TROPICAL METEOROLOGY & Climate: Hadley Circulation

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Jian; Vecchi, Gabriel A.

    2015-01-30

    The Hadley circulation, a prominent circulation feature characterized by rising air near the Equator and sinking air in the subtropics, defines the position of dry subtropical areas and is a fundamental regulator of the earth’s energy and momentum budgets. The character of the Hadley circulation, and its related precipitation regimes, exhibits variation and change in response to both climate variability and radiative forcing changes. The strength and position of the Hadley circulation change from year to year paced by El Niño and La Niña events. Over the last few decades of the twentieth century, the Hadley cell has expanded poleward in both hemispheres, with changes in atmospheric composition (including stratospheric ozone depletion and greenhouse gas increases) thought to have contributed to its expansion. This article introduces the basic phenomenology and driving mechanism of the Hadley circulation and discusses its variations under both natural and anthropogenic climate forcings.

  18. Weak response of the Atlantic thermohaline circulation to an increase of atmospheric carbon dioxide in IAP/LASG Climate System Model

    Institute of Scientific and Technical Information of China (English)

    ZHOU Tianjun; YU Rucong; LIU Xiying; GUO Yufu; YU Yongqiang; ZHANG Xuehong

    2005-01-01

    Response of the Atlantic thermohaline circula- tion (THC) to global warming is examined by using the climate system model developed at IAP/LASG. The evidence indicates that the gradually warming climate associated with the increased atmospheric carbon dioxide leads to a warmer and fresher sea surface water at the high latitudes of the North Atlantic Ocean, which prevents the down-welling of the surface water. The succedent reduction of the pole-to- equator meridional potential density gradient finally results in the decrease of the THC in intensity. When the atmospheric carbon dioxide is doubled, the maximum value of the Atlantic THC decreases approximately by 8%. The associated poleward oceanic heat transport also becomes weaker. This kind of THC weakening centralizes mainly in the northern part of the North Atlantic basin, indicating briefly a local scale adjustment rather than a loop oscillation with the whole Atlantic "conveyor belt" decelerating.

  19. Chemistry-Climate Interactions in the Goddard Institute for Space Studies General Circulation Model. 2; New Insights into Modeling the Pre-Industrial Atmosphere

    Science.gov (United States)

    Grenfell, J. Lee; Shindell, D. T.; Koch, D.; Rind, D.; Hansen, James E. (Technical Monitor)

    2002-01-01

    We investigate the chemical (hydroxyl and ozone) and dynamical response to changing from present day to pre-industrial conditions in the Goddard Institute for Space Studies General Circulation Model (GISS GMC). We identify three main improvements not included by many other works. Firstly, our model includes interactive cloud calculations. Secondly we reduce sulfate aerosol which impacts NOx partitioning hence Ox distributions. Thirdly we reduce sea surface temperatures and increase ocean ice coverage which impact water vapor and ground albedo respectively. Changing the ocean data (hence water vapor and ozone) produces a potentially important feedback between the Hadley circulation and convective cloud cover. Our present day run (run 1, control run) global mean OH value was 9.8 x 10(exp 5) molecules/cc. For our best estimate of pre-industrial conditions run (run 2) which featured modified chemical emissions, sulfate aerosol and sea surface temperatures/ocean ice, this value changed to 10.2 x 10(exp 5) molecules/cc. Reducing only the chemical emissions to pre-industrial levels in run 1 (run 3) resulted in this value increasing to 10.6 x 10(exp 5) molecules/cc. Reducing the sulfate in run 3 to pre-industrial levels (run 4) resulted in a small increase in global mean OH (10.7 x 10(exp 5) molecules/cc). Changing the ocean data in run 4 to pre-industrial levels (run 5) led to a reduction in this value to 10.3 x 10(exp 5) molecules/cc. Mean tropospheric ozone burdens were 262, 181, 180, 180, and 182 Tg for runs 1-5 respectively.

  20. Empirical relationships between summertime oceanic heat anomalies in the Nordic seas and large-scale atmospheric circulation in the following winter

    Science.gov (United States)

    Schlichtholz, Pawel

    2016-09-01

    A lagged regression analysis between an index of observed summertime Atlantic water temperature (AWT) variability at the entrance to the Barents Sea in the period 1982-2005 and year-round atmospheric (NCEP/NCAR) reanalysis data is used to show that subsurface oceanic heat anomalies in high latitudes are significant precursors of wintertime atmospheric variability in middle latitudes. In particular, positive AWT anomalies precede predominantly westerly wind anomalies in high latitudes and easterly wind anomalies in middle latitudes. The mid-latitude wind anomalies, while being generally equivalent barotropic in the upper troposphere, have a strong low-level baroclinic contribution over Eurasia. The near-surface easterly wind anomalies in this area are locally deflected southward, maintaining cold spots near orography. The summertime oceanic anomalies explain about 40 % of the variance in the surface air temperature averaged over Eurasia from 35° to 45°N and about 50 % of the variance in surface winds over the Far East Asia in the following winter. We suggest that the remote connections arise from reorganization of the mid-latitude storm tracks. The AWT anomalies explain about 60 % of the variance in the upper-tropospheric storm track activity averaged over the Pacific and Eurasia from 35° to 55°N and in the lower-tropospheric poleward synoptic eddy heat flux over western Eurasia. Finally, we show that the AWT-associated wintertime atmospheric anomalies appear in quadrature with the concurrent anomalies associated with the North Atlantic Oscillation. These findings suggest that oceanic heat anomalies in high latitudes may be a useful predictor of atmospheric variability.

  1. Atmospheric circulation patterns, cloud-to-ground lightning, and locally intense convective rainfall associated with debris flow initiation in the Dolomite Alps of northeastern Italy

    OpenAIRE

    Underwood, S. Jeffrey; Schultz, Michael D.; Berti, Metteo; Gregoretti, Carlo; Simoni, Alessandro; Mote, Thomas L.; Saylor, Anthony M.

    2016-01-01

    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 ...

  2. Atmospheric circulation patterns, cloud-to-ground lightning, and locally intense convective rainfall associated with debris flow initiation in the Dolomite Alps of northeastern Italy

    OpenAIRE

    S. J. Underwood; Schultz, M D; Berti, M; C. Gregoretti; Simoni, A.; T. L. Mote; A. M. Saylor

    2015-01-01

    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 hydrogeologic events. In the past debris flow events have been studied primarily in the context of their geologic and geomorphic characteristics. The atmospheric contribution to th...

  3. On the mechanisms in a tropical ocean-global atmosphere coupled general circulation model. Pt. I. Mean state and the seasonal cycle

    Energy Technology Data Exchange (ETDEWEB)

    Vintzileos, A. [Paris-6 Univ., 75 (France). Lab. de Meteorologie Dynamique; Delecluse, P. [Laboratoire d`Oceanographie Dynamique et de Climatologie, UMR: CNRS/ORSTOM/Universite Pierre et Marie Curie, Universite Pierre et Marie Curie, Tour 26, etage 4, 4, place Jussieu, 75252 Paris Cedex 05 (France); Sadourny, R. [Laboratoire de Meteorologie Dynamique du CNRS, Ecole Normale Superieure, 24, rue Lhomond, 75231 Paris Cedex 05 (France)

    1999-01-01

    The mechanisms responsible for the mean state and the seasonal and interannual variations of the coupled tropical Pacific-global atmosphere system are investigated by analyzing a thirty year simulation, where the LMD global atmospheric model and the LODYC tropical Pacific model are coupled using the delocalized physics method. No flux correction is needed over the tropical region. The coupled model reaches its regime state roughly after one year of integration in spite of the fact that the ocean is initialized from rest. Departures from the mean state are characterized by oscillations with dominant periodicities at annual, biennial and quadriennial time scales. In our model, equatorial sea surface temperature and wind stress fluctuations evolved in phase. In the central Pacific during boreal autumn, the sea surface temperature is cold, the wind stress is strong, and the intertropical convergence zone (ITCZ) is shifted northwards. The northward shift of the ITCZ enhances atmospheric and oceanic subsidence between the equator and the latitude of organized convention. In turn, the stronger oceanic subsidence reinforces equatorward convergence of water masses at the thermocline depth which, being not balanced by equatorial upwelling, deepens the equatorial thermocline. An equivalent view is that the deepening of the thermocline proceeds from the weakening of the meridional draining of near-surface equatorial waters. The inverse picture prevails during spring, when the equatorial sea surface temperatures are warm. Thus temperature anomalies tend to appear at the thermocline level, in phase opposition to the surface conditions. (orig.) With 28 figs., 2 tabs., 60 refs.

  4. The impact of upper tropospheric friction and Gill-type heating on the location and strength of the Tropical Easterly Jet: Idealized physics in a dry Atmospheric General Circulation Model

    CERN Document Server

    Rao, Samrat

    2015-01-01

    An atmospheric general circulation model (AGCM) with idealized and complete physics has been used to evaluate the Tropical Easterly Jet (TEJ) jet. In idealized physics, the role of upper tropospheric friction has been found to be important in getting realistic upper tropospheric zonal wind patterns in response to heating. In idealized physics, the location and strength of the TEJ as a response to Gill heating has been studied. Though the Gill model is considered to be widely successful in capturing the lower tropospheric response, it is found to be inadequate in explaining the location and strength of the upper level TEJ. Heating from the Gill model and realistic upper tropospheric friction does not lead to the formation of a TEJ.

  5. Simulation of the Atlantic meridional overturning circulation in an atmosphere-ocean global coupled model. Part I: a mechanism governing the variability of ocean convection in a preindustrial experiment

    Energy Technology Data Exchange (ETDEWEB)

    Guemas, Virginie [Meteo-France, CNRS, Centre National de Recherches Meteorologiques/Groupe d' Etude de l' Atmosphere Meteorologique, Toulouse Cedex (France); UMR 1572, CEA-CNRS-UVSQ, Laboratoire des Sciences du Climat et de l' Environnement, Gif-sur-Yvette (France); Salas-Melia, David [Meteo-France, CNRS, Centre National de Recherches Meteorologiques/Groupe d' Etude de l' Atmosphere Meteorologique, Toulouse Cedex (France)

    2008-07-15

    A preindustrial climate experiment was conducted with the third version of the CNRM global atmosphere-ocean-sea ice coupled model (CNRM-CM3) for the Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC AR4). This experiment is used to investigate the main physical processes involved in the variability of the North Atlantic ocean convection and the induced variability of the Atlantic meridional overturning circulation (MOC). Three ocean convection sites are simulated, in the Labrador, Irminger and Greenland-Iceland-Norwegian (GIN) Seas in agreement with observations. A mechanism linking the variability of the Arctic sea ice cover and convection in the GIN Seas is highlighted. Contrary to previous suggested mechanisms, in CNRM-CM3 the latter is not modulated by the variability of freshwater export through Fram Strait. Instead, the variability of convection is mainly driven by the variability of the sea ice edge position in the Greenland Sea. In this area, the surface freshwater balance is dominated by the freshwater input due to the melting of sea ice. The ice edge position is modulated either by northwestward geostrophic current anomalies or by an intensification of northerly winds. In the model, stronger than average northerly winds force simultaneous intense convective events in the Irminger and GIN Seas. Convection interacts with the thermohaline circulation on timescales of 5-10 years, which translates into MOC anomalies propagating southward from the convection sites. (orig.)

  6. Link between large scale atmospheric circulation and heat waves for seasonal forecasting and climate change impact studies; Le lien entre circulation atmospherique de grande echelle et canicules pour la prevision a longue echeance et l'impact du changement climatique

    Energy Technology Data Exchange (ETDEWEB)

    Boe, J.; Cassou, Ch.; Terray, L. [CERFACS, 31 - Toulouse (France); Parey, S.; Dubus, L. [EDF/R and D/MFEE, 78 - Chatou (France)

    2010-07-01

    Climate models are designed to reproduce the average behaviour of the climatic parameters over quite large geographical areas, and the large scale atmospheric circulation. Large scale atmospheric circulation shows some stable and recurrent patterns, called weather regimes, whose succession can explain the local observed meteorological conditions. These structures are then identified for the summer season and their link with hot and dry days in France are studied. From the 4 identified summer regimes, 2 are associated with an increased occurrence of hot and dry conditions over France. Although this link does not explain the total summer variability, it can help to anticipate hot and dry conditions and it is used here for seasonal forecast perspectives and to analyse the impact of climate change on the occurrence of heat waves. Regarding seasonal forecast, an influence of anomalous tropical conditions (a northern shift of the Inter Tropical Convergence Zone) has been identified as susceptible to increase the occurrence frequency of the 2 regimes linked to hot and dry conditions in France in summer. Thus, if this link can be confirmed and if climate models are able to re-produce it correctly, then it could lead to an interesting anticipation of the possible occurrence of an heat wave in the next summer. As far as climate change is concerned, the study shows that in the future, one of the 2 hot and dry regimes could be more frequent, while the most cold and wet one becomes less frequent. Thus, globally, hot and dry days should occur more frequently. There are however still many uncertainties, as on the one hand, models show different results concerning the future occurrence of the regimes, and on the other hand, the other local mechanisms linked to the heat wave occurrence, like soil moisture content and evolution, are sometimes poorly represented. (authors)

  7. A global numerical study of radon-222 and lead-210 in the atmosphere using the AES and York University CDT General Circulation Model (AYCG)

    Science.gov (United States)

    Beagley, Stephen R.; Degrandpre, Jean; Mcconnell, John C.; Laprise, Rene; Mcfarlane, Norman

    1994-01-01

    The Canadian Climate Center (CCC) GCM has been modified to allow its use for studies in atmospheric chemistry. The initial experiments reported here have been run to test and allow sensitivity studies of the new transport module. The impact of different types of parameterization for the convective mixing have been studied based on the large scale evolution of Rn-222 and Pb-210. Preliminary results have shown that the use of a scheme, which mixes unstable columns over a very short time scale, produces a global distribution of lead that agrees in some aspects with observations. The local impact of different mixing schemes on a short lived tracer like the radon is very important.

  8. Boreal lakes moderate seasonal and diurnal temperature variation and perturb atmospheric circulation: Analyses in the Community Earth System Model 1 (CESM1)

    Energy Technology Data Exchange (ETDEWEB)

    Subin, Zachary M. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Earth Sciences Div.; Murphy, Lisa N. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Earth Sciences Div.; Li, Fiyu [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Earth Sciences Div.; Bonfils, Celine [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Program for Climate Model Diagnosis and Intercomparison; Riley, William J. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Earth Sciences Div.

    2012-01-15

    We used a lake thermal physics model recently coupled into the Community Earth System Model 1 (CESM1) to study the effects of lake distribution in present and future climate. Under present climate, correcting the large underestimation of lake area in CESM1 (denoted CCSM4 in the configuration used here) caused 1 °C spring decreases and fall increases in surface air temperature throughout large areas of Canada and the US. Simulated summer surface diurnal air temperature range decreased by up to 4 °C, reducing CCSM4 biases. These changes were much larger than those resulting from prescribed lake disappearance in some present-day permafrost regions under doubled-CO2 conditions. Correcting the underestimation of lake area in present climate caused widespread high-latitude summer cooling at 850 hPa. Significant remote changes included decreases in the strength of fall Southern Ocean westerlies. We found significantly different winter responses when separately analysing 45-yr subperiods, indicating that relatively long simulations are required to discern the impacts of surface changes on remote conditions. We also investigated the surface forcing of lakes using idealised aqua-planet experiments which showed that surface changes of 2 °C in the Northern Hemisphere extra-tropics could cause substantial changes in precipitation and winds in the tropics and Southern Hemisphere. Shifts in the Inter-Tropical Convergence Zone were opposite in sign to those predicted by some previous studies. Zonal mean circulation changes were consistent in character but much larger than those occurring in the lake distribution experiments, due to the larger magnitude and more uniform surface forcing in the idealised aqua-planet experiments.

  9. Boreal lakes moderate seasonal and diurnal temperature variation and perturb atmospheric circulation: analyses in the Community Earth System Model 1 (CESM1

    Directory of Open Access Journals (Sweden)

    William J. Riley

    2012-02-01

    Full Text Available We used a lake thermal physics model recently coupled into the Community Earth System Model 1 (CESM1 to study the effects of lake distribution in present and future climate. Under present climate, correcting the large underestimation of lake area in CESM1 (denoted CCSM4 in the configuration used here caused 1 °C spring decreases and fall increases in surface air temperature throughout large areas of Canada and the US. Simulated summer surface diurnal air temperature range decreased by up to 4 °C, reducing CCSM4 biases. These changes were much larger than those resulting from prescribed lake disappearance in some present-day permafrost regions under doubled-CO2 conditions. Correcting the underestimation of lake area in present climate caused widespread high-latitude summer cooling at 850 hPa. Significant remote changes included decreases in the strength of fall Southern Ocean westerlies. We found significantly different winter responses when separately analysing 45-yr subperiods, indicating that relatively long simulations are required to discern the impacts of surface changes on remote conditions. We also investigated the surface forcing of lakes using idealised aqua-planet experiments which showed that surface changes of 2 °C in the Northern Hemisphere extra-tropics could cause substantial changes in precipitation and winds in the tropics and Southern Hemisphere. Shifts in the Inter-Tropical Convergence Zone were opposite in sign to those predicted by some previous studies. Zonal mean circulation changes were consistent in character but much larger than those occurring in the lake distribution experiments, due to the larger magnitude and more uniform surface forcing in the idealised aqua-planet experiments.

  10. An Overview: Experimental Characterization of Biomass Burning Aerosols during EFEU[EFEU - Impact of vegetation fires on composition and circulation of the atmosphere

    Energy Technology Data Exchange (ETDEWEB)

    Massling, A.; Iinuma, Y.; Zeromskiene, K.; Herrmann, H.; Wiedensohler, A. [Leibniz-Inst. for Tropospheric Research, Leipzig (Germany); Schmid, O.; Dusek, U.; Helas, G.; Chand, D.; Parmar, R.S.; Andreae, M.O. [Max Planck Inst. for Chemistry, Mainz (Germany). Biogeochemistry Dept.

    2005-07-01

    Vegetation fires are a significant source for atmospheric trace gases and aerosol particles on local, regional, and global scales. Vast fires regularly occur in the tropics as well as in the mid latitudes and boreal regions. Fire emissions and their reaction products are transported by convection into the free troposphere and therefore affect the energy budget of the atmosphere by direct and indirect radiation effects. Up to now there is only limited information on the physical and chemical properties of biomass burning aerosols which are partly responsible for the large uncertainties in quantifying the climatic impact of aerosols generally. Especially, the microphysical properties of the emitted aerosol particles have received little attention to date. This work gives detailed information of the methodology applied to experimentally characterize the physical and chemical properties of fresh (age: <10 minutes) biomass burning aerosols from various biomass fuels. In general, the chemical analysis of the samples show equal results for different fuel types. Submicrometer particles were mainly composed of organic carbon rather than by inorganic ions. Consequently, the hygroscopicity measurements performed at 85 % at various diameters show only slightly hygroscopic behaviour (about 5 to 15 % diameter growth) of the examined smoke particles. Furthermore, our observations show that the humidification growth in scattering properties of the fresh aerosols is relatively low (<15%) compared to ambient aerosols in natural vegetations fires. These results go along with relatively low CCN efficiencies (the ratio of CCN to total particle number concentration). The CCN efficiency from typical wood smoke particles gradually increased with particle size at a given S and particles of 250 nm or larger are normally completely activated at S = 0.2%. It was found that changes in aerosol properties were strongly dependent on the burning conditions. These conditions were characterized by

  11. 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...

  12. 2010年夏季北极冰情变化及大气环流场演变%STATUS OF ARCTIC SEA ICE AND ATMOSPHERIC CIRCULATION IN SUMMER 2010

    Institute of Scientific and Technical Information of China (English)

    隋翠娟; 张占海; 凌铁军; 吴辉碇; 于乐江

    2011-01-01

    Based on data from the National Sea Ice Data Center (NSIDC) , we present the Arctic sea ice extent and concentration during the Fourth Chinese Arctic Research Expedition of 2010, and analyze the corresponding atmospheric circulation using NCEP/NCAR reanalysis data. It is found that the positive dipole anomaly increased ice melt rates in June and August. The ice extent in June reached the minimum of historical records. The melt rate was reduced in July because of the control of low pressure. In August, leads and polynyas appeared in the central Arctic area spanning the North Pole, from Pacific Ocean to Atlantic Ocean, where ice concentration was less than 80%.We therefore conclude that ice extent and concentration were significantly affected by the atmospheric circulation. Additionally, the earlier clearing of sea ice along the Northwest Passage was caused by abnormally high springtime temperatures in the Canadian Arctic area.%利用美国冰雪中心(NSIDC)资料分析2010年夏季中国第4次北极科学考察期间北极海冰的冰情变化,并通过NCEP再分析资料对同时期的大气环流演变进行分析,发现6月与8月环流形势为偶极子正异常,加速了海冰的融化,其中2010年6月的海冰覆盖范围达到有历史记录以来的6月最低值;7月为低压控制,减缓了海冰覆盖范围的进一步减少;2010年8月北极区域出现冰间水道和冰间湖,跨越极点由太平洋一侧到大西洋一侧,大范围区域内海冰密集度小于80%.由此可见,2010年夏季海冰覆盖范围及密集度变化主要受同期大气环流场的影响.此外,简单指出西北通道北线冰提前融化是由春季北极加拿大区域气温异常偏高引起.

  13. North Atlantic Circulation

    Science.gov (United States)

    Molinari, R.; Bryan, K.; Schott, F.

    The intensity of the North Atlantic winddriven and thermohaline circulation and the close proximity of many oceanographic installations make the North Atlantic a particularly favored region of the world ocean from the standpoint of research in ocean circulation. Recent increases in available data and advances in numerical modeling techniques served as the impetus to convene a joint workshop of modelers and observers working on the North Atlantic with the Scientific Committee on Oceanic Research (SCOR) Working Group (WG) 68 (“North Atlantic Circulation”). Goals of the workshop were to provide an update on data sets and models and to discuss the poleward heat flux problem and possible monitoring strategies. The joint Workshop/SCOR WG-68 meeting was convened by F. Schott (chairman of the working group; Rosenstiel School of Marine and Atmospheric Science, Miami, Fla.), K. Bryan (National Oceanic and Atmospheric Administration/ Geophysical Fluid Dynamics Laboratory (NOAA/GFDL)), and R. Molinari (NOAA/Atlantic Oceanographic and Meteorological Laboratory (NOAA/AOML)).

  14. Circulation economics

    DEFF Research Database (Denmark)

    Ingebrigtsen, Stig; Jakobsen, Ove

    2006-01-01

    Purpose - This paper is an attempt to advance the critical discussion regarding environmental and societal responsibility in economics and business. Design/methodology/approach - The paper presents and discusses as a holistic, organic perspective enabling innovative solutions to challenges...... concerning the responsible and efficient use of natural resources and the constructive interplay with culture. To reach the goal of sustainable development, the paper argues that it is necessary to make changes in several dimensions in mainstream economics. This change of perspective is called a turn towards...... presupposes a perspective integrating economic, natural and cultural values. Third, to organize the interplay between all stakeholders we introduce an arena for communicative cooperation. Originality/value - The paper concludes that circulation economics presupposes a change in paradigm, from a mechanistic...

  15. Roles of Arctic sea ice and the preceding summer Arctic atmospheric circulation anomalies in the at-mospheric circulations anomalies of 2011/2012 and 2015/2016 winters%从2011/2012和2015/2016年冬季大气环流异常看北极海冰以及前期夏季北极大气环流异常的作用

    Institute of Scientific and Technical Information of China (English)

    武炳义; 杨琨

    2016-01-01

    Using the NCEP/NCAR re-analysis data (re-analysis I),the ERA-Interim re-analysis data,and Hadley Center Arc-tic sea ice concentration data,main characteristics of atmospheric circulation anomalies in the winters of 2011/2012 and 2015/2016 were investigated based on diagnostic analysis and numerical simulations,and the possible causes were revealed.The re-sults indicate that although sea surface temperature anomalies in the tropical Pacific in the two winters corresponded to a weak La Ni~na and a strong El Ni~no event respectively and were distinctly different,the Siberian high was very strong in both win-ters,ranking the highest and the 5th highest since 1979,respectively.Autumn Arctic sea ice loss is a major reason that causes strong Siberian high in both winters.More important,anticyclonic surface winds in the preceding summer season over the Arc-tic Ocean and higher than normal air temperatures in the mid-and low-troposphere aloft strengthen the negative feedback of Arctic sea ice loss on the winter atmospheric variability,which further enhances the Siberian high and thereby favors the occur-rence of extreme cold events in East Asia.Apparently the dynamic and thermal dynamic conditions of summer Arctic atmos-pheric circulation not only influence Arctic sea ice in the summer and autumn,but also modulate the effects of Arctic sea ice loss on winter atmospheric variability.The strong El Ni~no event in the winter of 2015/2016 couldn't offset effects of Arctic sea ice loss and atmospheric circulation anomalies on the winter atmospheric variability over East Asia.%利用美国 NCEP/NCAR、欧洲中心 ERA-Interim 再分析资料,以及英国哈得来中心海冰密集度资料,通过诊断分析和数值模拟试验,研究了2011/2012和2015/2016年两个冬季大气环流异常的主要特征和可能原因。结果表明,尽管热带太平洋海温背景截然不同(分别为弱的拉尼娜事件和强厄尔尼诺事件),但这两个冬季西伯

  16. Regional variations in provenance and abundance of ice-rafted clasts in Arctic Ocean sediments: Implications for the configuration of late Quaternary oceanic and atmospheric circulation in the Arctic

    Science.gov (United States)

    Phillips, R.L.; Grantz, A.

    2001-01-01

    the last glacial maximum on the North Slope of Alaska, suggests that atmospheric circulation in the western Arctic during late Quaternary was similar to that of the present. ?? 2001 Elsevier Science B.V.

  17. Atmospheric Diabatic Heating and Summertime??Circulation in Asia-Africa Area%亚——非季风区非绝热加热与夏季环流关系的诊断研究

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    基于热力适应理论,本文利用NCEP/NCAR再分析资料对撒哈拉沙漠、青藏高原和孟加拉湾地区的非绝热加热与夏季环流进行了诊断研究。在非洲撒哈拉沙漠地区,以感热输送为主的加热仅局限于近地面层,边界层以上的大气则以辐射冷却占优势。因而除了边界层内存在着浅薄的正涡度和微弱的上升运动以外,整个对流层几乎都维持负涡度并盛行下沉运动。对于青藏高原地区,强大的表面感热通量引起的垂直扩散是近地面大气加热的主要分量,与大尺度上升运动相关的凝结潜热对低层大气的加热也有一定的贡献。长波辐射造成的对流层中、上层大气的冷却则主要由深对流潜热释放来补偿。夏季高原地区总非绝热加热是正值,且最大加热率出现在边界层内。低空大气辐合产生正涡度,而中、高层大气辐散伴有较强的负涡度。因而高原盛行上升运动,最大上升运动位于近地面层。夏季孟加拉湾地区的深对流凝结潜热释放远大于长波辐的冷却作用,因而整个对流层几乎都保持较强的非绝热加热。400hPa层附近的最大加热率引起300-400hPa最强的上升运动。对流层上层是负涡度区,而中、低层为正涡度区。结果还表明,垂直和水平辐散环流与大气的热源和热汇区密切相联:在高层,辐散气流从热源区流向热汇区;在低层则相反,气流从热汇区流向热源区。%Utilizing data from NCEP/NCAR reanalysis, the summertime atmospheric diabatic heating due to different physical processes is investigated over the Sahara desert, the Tibetan Plateau, and the Bay of Bengal. Atmospheric circulation systems in summer over these three areas are also studied. Thermal adaptation theory is employed to explain the relationship between the circulation and the atmospheric diabatic heating. 牋牋燨ver the Sahara desert, heating resulting from the

  18. NUCLA Circulating Atmospheric Fluidized Bed Demonstration Project

    Energy Technology Data Exchange (ETDEWEB)

    1992-02-01

    The report summarizes unit operating experience and test program progress for 1989 on Colorado-Ute Electric Association's Nucla CFB Demonstration Program. During this period, the objectives of the Nucla Station operating group were to correct problems with refractory durability, resolve primary air fan capacity limitations, complete the high ash and high sulfur coal tests, switch to Salt Creek coal as the operating fuel, and make the unit available for testing without capacity restrictions. Each of these objectives was addressed and accomplished, to varying degrees, except for the completion of the high sulfur coal acceptance tests. (VC)

  19. Predictability in models of the atmospheric circulation.

    NARCIS (Netherlands)

    Houtekamer, P.L.

    1992-01-01

    It will be clear from the above discussions that skill forecasts are still in their infancy. Operational skill predictions do not exist. One is still struggling to prove that skill predictions, at any range, have any quality at all. It is not clear what the statistics of the analysis error are. The

  20. Anomalies of Ocean and Atmospheric Circulation in 2013 and Their Impacts on Climate in China%2013年海洋和大气环流异常及对中国气候的影响

    Institute of Scientific and Technical Information of China (English)

    司东; 袁媛; 崔童; 孙冷; 王东阡; 柳艳菊; 郭艳君; 王遵娅

    2014-01-01

    本文对2013年海洋和大气环流异常特征进行分析,讨论这些异常特征对中国气温和降水的主要影响。结果表明:2012/2013年冬季,北极涛动持续维持负位相,500 hPa位势高度场上,欧亚大陆中高纬环流呈“两槽一脊”的环流形势,乌拉尔山的高压脊持续偏强,而东亚槽也异常偏强,导致全国平均气温较常年同期偏低。季内,西伯利亚高压强度变化显著,与之相对应,我国气温季内阶段性变化大,前冬冷、后冬暖。进一步研究表明,前秋北极海冰的大幅偏少是造成东亚冬季风偏强的重要原因。2013年冬季至夏季,赤道中东太平洋海温异常偏低而海洋性大陆至西太平洋海温异常偏高,受此影响,夏季西太平洋副热带高压位置明显偏北,导致我国北方夏季多雨。与此同时,受西太平洋副热带高压下沉气流的控制,我国南方大部高温持续。2013年南海夏季风爆发偏早两候,结束偏晚4候,强度偏弱。%Anomalies of oceanic and atmospheric circulations are analyzed and their impacts on temperature and precipitation anomalies of 2013 in China are discussed.The results show that the Arctic Oscillation (AO)experienced negative phase during the 2012/2013 winter.At 500 hPa,a“two troughs and one ridge”anomalous geopotential height pattern dominated the mid-high latitudes in Eurasia,leading to an enhanced ridge and trough over Urals and East Asia,respectively,and further leading to be colder than normal situ-ation over China.While the Siberian high exhibited strong intra-seasonal variations,the temperature over China had two-stage variations last winter,warmer in the early winter and colder in the late winter.Fur-ther research indicates that the reduced Arctic sea ice extent in the last autumn was responsible for the stronger East Asian winter monsoon.During the period from winter to summer 2013,the anomalous low sea surface temperature

  1. 2012年盛夏我国多台风特征及环流背景初步分析%Tentative analysis on multi-typhoon characteristics and atmospheric circulation background in the midsummer of 2012

    Institute of Scientific and Technical Information of China (English)

    张春艳; 王力; 孙明明; 张建海

    2012-01-01

    利用西太平洋编号台风资料、NOAA卫星观测的地球向外长波辐射(OLR)资料、全球海表温度(SST)资料以及NCEP/NCAR逐日再分析资料,对2012年7—8月西太平洋地区生成并登陆或影响我国的台风特征及大尺度环流背景进行了初步分析。结果表明:7月中旬至8月底是当年台风生成和登陆的高度集中期,登陆比例之高、对我国影响范围之大等特征实属罕见;南亚高压偏强,中高纬"两脊一槽"环流型,东北地区为高压脊区,副热带高压稳定、强度增强且偏西偏北是这一时期的大气环流特征;副热带高压脊线位置在30°N以北有利台风初生,其南界位置偏北时,有利于部分台风生成于较高纬度,西伸指数持续偏高有利于台风集中登陆;夏季风明显增强和季风槽(ITCZ)位置变化、7—8月西太平洋SST正异常和OLR负异常可能是造成台风多发的原因,异常区域北界偏北也许是造成台风生成纬度偏北的原因。%Tentative analysis on multi-typhoon characteristics and atmospheric circulation background in China between July and August in 2012 is performed with the data of serially numbered typhoons in northwestern Pacific,outgoing long-wave radiation(OLR) data from NOAA,sea surfer temperature(SST) data and NCEP/NCAR reanalysis dataset.Conclusions are drawn that the typhoons originated and landed mainly in the period from mid-July to the end of August in China,and it is unusual that the percentage of typhoon landing is high and the area affected by typhoon is large.Atmospheric circulation characteristics in the period mainly show the stronger South Asian High,the two ridges and one trough pattern with a ridge in the Northeast China over the mid-and high-latitudes and the western Pacific subtropical high(WPSH) stabilized with increased intensity and more westward and more northward location.The ridge of WPSH locating in the north of 30°N is in favor of the genesis of

  2. El Nino, from 1870 to 2014, and other Atmospheric Circulation Forcing by Extreme Apparitions of the Eight Annual, Continental Scale, Aerosol Plumes in the Satellite Era which Point to a Possible Cause for the Current Californian Drought

    Science.gov (United States)

    Potts, K. A.

    2015-12-01

    Eight continental scale aerosol plumes exist each year as the enclosed image shows. Apparitions of seven plumes only exist for a few months in the same season each year whilst the East Asian Plume is visible all year. The aerosol optical depth (AOD) of all the plumes varies enormously interannually with two studies showing the surface radiative forcing of the South East Asian Plume (SEAP) as -150W/m2 and -286W/m2/AOD. I show that the SEAP, created by volcanic aerosols (natural) and biomass burning and gas flares in the oil industry (anthropogenic), is the sole cause of all El Nino events, the greatest interannual perturbation of the atmospheric circulation system. The SEAP creates an El Nino by absorbing solar radiation at the top of the plume which heats the upper atmosphere and cools the surface. This creates a temperature inversion compared to periods without the plume and reduces convection. With reduced convection in SE Asia, the Maritime Continent, the Trade Winds blowing across the Pacific are forced to relax as their exit into the Hadley and Walker Cells is constrained and the reduced Trade Wind speed causes the Sea Surface Temperature (SST) to rise in the central tropical Pacific Ocean as there is a strong negative correlation between wind speed and SST. The warmer SST in the central Pacific creates convection in the region which further reduces the Trade Wind speed and causes the Walker Cell to reverse - a classic El Nino. Having established the ability of such extreme aerosol plumes to create El Nino events I will then show how the South American, West African, Middle East and SEAP plumes create drought in the Amazon, Spain, Darfur and Australia as well as causing the extremely warm autumn and winter in Europe in 2006-07. All these effects are created by the plumes reducing convection in the region of the plume which forces the regional Hadley Cells into anomalous positions thereby creating persistent high pressure cells in the mid latitudes. This

  3. Quantitative reconstruction of sea-surface conditions over the last ~150 yr in the Beaufort Sea based on dinoflagellate cyst assemblages: the role of large-scale atmospheric circulation patterns

    Directory of Open Access Journals (Sweden)

    L. Durantou

    2012-06-01

    Full Text Available Dinoflagellate cyst (dinocyst assemblages have been widely used over the Arctic Ocean to reconstruct sea-surface parameters on a quantitative basis. Such reconstructions provide insights into the role of anthropogenic vs natural forcings in the actual climatic trend. Here, we present the palynological analysis of a 36 cm-long core collected from the Mackenzie Through in the Canadian Beaufort Sea. Dinocyst assemblages were used to quantitatively reconstruct the evolution of sea surface conditions (temperature, salinity, sea ice and freshwater palynomorphs influxes were used as local paleo-river discharge indicators over the last ~150 yr. Dinocyst assemblages are dominated by autotrophic taxa (68 to 96 %. Pentapharsodinium dalei is the dominant specie throughout most of the core, except at the top where the assemblages are dominated by Operculodinium centrocarpum. Quantitative reconstructions of sea surface parameters display a serie of relatively warm, lower sea ice and saline episodes in surface waters, alternately with relatively cool and low salinity episodes. The warm episodes are characterized with high dinocyst productivity. Variations of dinocyst influxes and reconstructed sea surface conditions are closely linked to large scale atmospheric circulation patterns such as the Pacific Decadal Oscillation (PDO and to a lesser degree, the Arctic Oscillation (AO. Positive phases of the PDO correspond to increases of dinocyst influxes, warmer and saltier surface waters, which we associate with upwelling events of warm and relatively saline water from Pacific origin. Freshwater palynomorph influxes increased in three phases from AD 1857 until reaching maximum values in AD 1991, suggesting that the Mackenzie River discharge followed the same trend when its discharge peaked between AD 1989 and AD 1992. The PDO mode seems to dominate the climatic variations at multi-annual to decadal timescales in the Western Canadian Arctic and Beaufort

  4. Quantitative reconstruction of sea-surface conditions over the last 150 yr in the Beaufort Sea based on dinoflagellate cyst assemblages: the role of large-scale atmospheric circulation patterns

    Directory of Open Access Journals (Sweden)

    L. Durantou

    2012-12-01

    Full Text Available Dinoflagellate cyst (dinocyst assemblages have been widely used over the Arctic Ocean to reconstruct sea-surface parameters on a quantitative basis. Such reconstructions provide insights into the role of anthropogenic vs natural forcings in the actual climatic trend. Here, we present the palynological analysis of a dated 36 cm-long core collected from the Mackenzie Trough in the Canadian Beaufort Sea. Dinocyst assemblages were used to quantitatively reconstruct the evolution of sea-surface conditions (temperature, salinity, sea ice and freshwater palynomorphs fluxes were used as local paleo-river discharge indicators over the last ~ 150 yr. Dinocyst assemblages are dominated by autotrophic taxa (68 to 96%. Cyst of Pentapharsodinium dalei is the dominant species throughout most of the core, except at the top where the assemblages are dominated by Operculodinium centrocarpum. Quantitative reconstructions of sea-surface parameters display a series of relatively warm, lower sea ice and saline episodes in surface waters, alternately with relatively cool and low salinity episodes. Variations of dinocyst fluxes and reconstructed sea-surface conditions may be closely linked to large scale atmospheric circulation patterns such as the Pacific Decadal Oscillation (PDO and to a lesser degree, the Arctic Oscillation (AO. Positive phases of the PDO correspond to increases of dinocyst fluxes, warmer and saltier surface waters, which we associate with upwelling events of warm and relatively saline water from Pacific origin. Freshwater palynomorph fluxes increased in three phases from AD 1857 until reaching maximum values in AD 1991, suggesting that the Mackenzie River discharge followed the same trend when its discharge peaked between AD 1989 and AD 1992. The PDO mode seems to dominate the climatic variations at multi-annual to decadal timescales in the western Canadian Arctic and Beaufort Sea areas.

  5. 与西澳州西南部冬季降水相联系的大气环流特征分析%The Characteristics of Atmospheric Circulation Associated with Austral Winter Rainfall in Southwest Western Australia

    Institute of Scientific and Technical Information of China (English)

    李建平; 李艳杰; 冯娟

    2011-01-01

    known modes, which may have impacts on the Australian rainfall, El Nino-Southern Oscillation (ENSO), Indian Ocean Dipole (IOD), ENSO Modoki (EM), and Southern Hemisphere Annular Mode (SAM) on the SWR are analyzed. It is found that they all cannot explain the long term rainfall variation of the SWR in neither early (May to July, MJJ) nor late (August to October, ASO) austral winter. Particularly, the reported significant inverse relationship between the SAM and SWR is caused by an extreme year. Based on the investigation on rainfall distribution over SWWA, seasonal march of the circulation features, dynamical and thermal structures of the atmospheric circulation, and thermal contrast between land and sea over wider southwest Australia, the authors find that the circulation over SWWA shows strong seasonally, and exhibits monsoonal characteristics, that is, alternate wet and dry seasons, seasonal reversal of prevailing winds, and an evident land-sea thermal contrast. Taking account of these monsoonal characteristics, the authors propose the concept of monsoon-like southwest Australian circulation (SWAC), and discuss the relationship between the SWAC and the SWR. The result indicates that the variability of SWAC contributes to the variation of SWR, whose weakening is a possible reason for the SWR decreasing.

  6. Interannual variability of the Adriatic Sea circulation

    Science.gov (United States)

    Beg Paklar, Gordana; Sepic, Jadranka; Grbec, Branka; Dzoic, Tomislav; Kovac, Zarko; Ivatek-Sahdan, Stjepan

    2016-04-01

    The Regional Ocean Modeling System (ROMS) was implemented in order to reproduce interannual variability of the Adriatic Sea circulation. Simulations and model result analysis were performed for a three-year period from 1st January 2011 to 31st December 2013. ROMS model run was forced with realistic atmospheric fields obtained from meteorological model Aladin, climatological river discharges, tides and Mediterranean circulation imposed at the southern open boundary. Atmospheric forcing included momentum, heat and water fluxes calculated interactively from the Aladin surface fields during ROMS model simulations. Model results were compared with available CTD and ADCP measurements and discussed in the light of the climatological circulation and thermohaline properties of the Adriatic Sea and its coastal areas. Interannual variability in the Adriatic circulation is related to the prevailing atmospheric conditions, changes in the hydrological conditions and water mass exchange at the Otranto Strait. Basic features of the Adriatic circulation - basin-wide cyclonic circulation with several embedded smaller cyclonic gyres around main pits - are well reproduced by ROMS model. Modelled temperatures and salinities are within corresponding seasonal intervals, although measured profiles generally indicate stronger stratification than modelled ones. Summer circulation in 2011 with current reversal obtained along the eastern Adriatic coast was related to the sampling results of the early fish stages as well as to ARGO drifter movements. Simulated fields from the Adriatic scale model were used to prescribe the initial and open boundary conditions for the interannual simulation in the middle Adriatic coastal domain.

  7. 江苏暴雨事件中大气环流类型初步分析%Preliminary analysis of the atmospheric circulation type of rainstorm events in Jiangsu Province

    Institute of Scientific and Technical Information of China (English)

    秦成云; 吴洪军; 汤洁; 封洋; 夏网萍

    2013-01-01

    选取江苏省近49年(1960-2008年)来64个台站暴雨资料,结合NCEP/NCAR再分析资料,选取111个典型暴雨天气过程,通过对500 hPa高度距平场进行EOF分型.结果表明近49年有影响的江苏省暴雨过程可以分为3种类型,即:两脊一槽型、纬向型和双阻型.并进一步分析各类型暴雨过程出现前一日和当日的500 hPa和700 hPa高度场、850 hPa风场和海平面气压场.分析结果表明:(1)两脊一槽型暴雨.500 hPa高度场是深厚的贝加尔湖大槽,700 hPa高度场两脊一槽的形势明显且有阶梯槽存在,高度场上等高线密集,850 hPa高度场水汽充沛,地面图上四川有低压且有东移发展成倒槽之势.此类型暴雨持续时间以一天居多.(2)纬向型暴雨.500 hPa高度场上环流较平直,多小槽活动,西南气流强盛,等高线稀疏.850 hPa高度场在苏北有风速和风向辐合区,此类型暴雨天气形势易产生持续性大范围暴雨.(3)双阻型暴雨.500 hPa高度场上中高纬度存在2个阻塞高压,贝加尔湖低槽深厚,且槽线分成南北二段,700 hPa高度场上中纬度多小槽活动,850 hPa高度场水汽输送通畅,此类型暴雨天气形势易出现持续性暴雨.%Using the precipitation data at 64 stations of Jiangsu province during 1960-2008 and the reanalysis data of The National Centers for Environmental Prediction and National Center For Atmospheric Research ( NCEP/ NCAR) , the pattern of typical rainstorm and the anomalies of associated atmospheric circulation were analyzed from EOF pattern of 500 hPa geopotential height. The results showed that there were three types of circulations through EOF method, the type with two ridge and one trough, zonal type and the type with two blocking, in the rainstorm e-vents. Further analysis were performed on the current day and the day before at 500 hPa, 700 hPa height field, 850 hPa wind field and sea level pressure field in the various types of rainstorm. The results were as

  8. 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.)

  9. 春季中国南方雨带年际变动与大气环流异常%The interannual variability of spring rainy belt over southern China and the associated atmospheric circulation anomalies

    Institute of Scientific and Technical Information of China (English)

    蒋品平; 赵平

    2012-01-01

    Using the daily accumulated precipitation data from Chinese 693 rain gauge stations and the daily National Centers for Environmental Prediction-National Center for Atmospheric Research (NCAR/NCEP) reanalysis data during 1960- 2008, the interannual variations of spring rainy-season precipitation in intensity and position over southern China and the associated atmospheric circulation anomalies were investigated by means of the statistical analysis methods. The results show that on the interdecadal time scale, the spring rainy-season precipitation to the south of the lower valley of the Yangtze River was less in the middle and late 1960s and was more in the middle 1970s to the early 1980s. It began decreasing from the early 1990s again. On the interannual time scale, when the subtropical high over the western North Pacific and the low-level low-pressure system to the east of the Tibetan Plateau strengthen and their anomalous centers appear to the south of 20°N and 30°N in spring respectively, anomalous southwesterly winds mainly prevail to the south of the Yangtze River valley. Remarkable convergence of air mass appears over the region where southwesterly winds gradually weaken, accompanying the local strengthened tow-level convergence of air mass, the tropospheric ascending motion, and the low-level convergence of water vapor. These anomalies lead to the increase of precipitation over there. At this time, the water vapor coming from the western North Pacific arrives at the South China Sea, not causes the local convergence, and turns northwards into southern China. While both the subtropical high and the low-pressure system strengthen and their anomalous centers appear to the north of 30° N, anomalous southwesterly winds prevail over most of eastern China, with the anomalies of low-level convergences of air mass and water vapor flux and of the tropospheric ascending motion shifting northward to the valleys of the Yangtze-Huai Rivers. Accordingly, more precipitation

  10. Modelled Circulation In Storfjorden

    Science.gov (United States)

    Skogseth, R.; Asplin, L.

    The model area Storfjorden is situated between the islands Spitsbergen, Barentsöya and Edgeöya at the Svalbard Archipelago. The entrance of Storfjorden is defined by a shallow bank Storfjordbanken and some small islands Tusenöyane in southeast, and by an 115m deep sill at about 76 45' N in the south. Maximum depth in Storfjorden is 190m, which is surrounded by gradually shallower shelves in the north, the east and southeast. A steep bottom slope is present on the western side of Storfjorden. He- leysundet and Freemansundet, two sounds between respectively Spitsbergen and Bar- entsöya, and Barentsöya and Edgeöya, define two narrow and shallow entrances in the north and northeast connecting Storfjorden with the northwestern Barents Sea. Strong tidal currents exist in Heleysundet (4-5ms-1) and Freemansundet (2-3ms-1), but the general circulation in Storfjorden is not well known. The coastal current in Storfjor- den is cyclonic directed into Storfjorden south of Edgeöya from the East Spitsbergen Current and out of Storfjorden south of Spitsbergen where it is called Sørkappstrøm- men. A three-dimensional sigma layered numerical ocean model called Bergen Ocean Model (BOM) was used to simulate the circulation in Storfjorden with Freemansundet opened. Two simulations were carried out, one with heat flux (100 Wm-2) and one without heat flux from the ocean to the atmosphere. The heat flux was applied only in the proper fjord area north of the sill and not outside as a crude approximation of the effects of a polynya in the sea ice cover during winter. Both simulations had a 4km horizontal resolution and 21 sigma layers. The model is forced by winds (from the NCEP reanalyzed fields) and tides. Initial fields are from the DNMI/IMR climatol- ogy. The model simulation without heat flux gave a circulation heavily dependent on tidal forcing, showing strong tidal currents up to 2ms-1 in Freemansundet, between Tusenöyane and on Storfjordbanken southwest of Edgeöya. Earlier

  11. 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.

  12. Response of the Atlantic Thermohaline Circulation to Changes of Atmospheric Green House Gases%北大西洋热盐环流对温室气体浓度变化的响应

    Institute of Scientific and Technical Information of China (English)

    朱江; 杨海军

    2012-01-01

    The equilibrium response of the thermohaline circulation (THC) to changes of atmospheric Green House Gases is simulated using a fully coupled climate model. The strength of the North Atlantic THC decreases about 20% when the concentration of atmospheric CO2 doubles and increases about 13% when the concentration halves. The response of the THC is divided into two different stages: the transient stage and the equilibrium stage. The transient response is mainly attributable to the changes of local surface heat flux and freshwater flux in the high latitude of North Atlantic, while the equilibrium response is also relevant to the non-local transport of heat and freshwater by THC itself, with the former acting as a positive feedback and the later as a negative feedback. The slow recovery of THC in the doubled CO2 experiment implies the role of the positive feedback overwhelms that of negative feedback, while the equilibrium behavior of THC in the halved CO2 experiment suggests that they cancel each other. In addition, the nonlinear relationship between density and temperature of seawater leads to the nonlinear behavior of the THC responses in doubled and halved CO2 experiments.%利用海-气耦合模式模拟了北大西洋热盐环流对外强迫的平衡响应。大气中CO2浓度加倍后,热盐环流强度将减弱约20%;大气中CO2浓度减半后,热盐环流将增强约13%。研究结果表明,热盐环流对外强迫的响应有两个阶段:瞬变阶段和平衡阶段。瞬变响应主要取决于局地海表热通量和淡水通量的变化,平衡响应还与非局地热量输送和淡水输送过程有关,两个过程作用相互竞争。在CO2加倍实验中,与淡水输送相关联的正反馈作用更强,导致热盐环流略有恢复;在CO2减半实验中,热量输送与淡水输送作用相抵,热盐环流没有明显的恢复。此外,海水密度与其温度的非线性关系导致CO2加倍和减半实验中热盐环

  13. Effect of vegetation on the Late Miocene ocean circulation

    Directory of Open Access Journals (Sweden)

    G. Lohmann

    2006-08-01

    Full Text Available A weak and shallow thermohaline circulation in the North Atlantic Ocean is related to an open Central American gateway and exchange with fresh Pacific waters. We estimate the effect of vegetation on the ocean general circulation using the atmospheric circulation model simulations for the Late Miocene climate. Caused by an increase in net evaporation in the Miocene North Atlantic, the North Atlantic water becomes more saline which enhances the overturning circulation and thus the northward heat transport. This effect reveals a potentially important feedback between the ocean circulation, the hydrological cycle and the land surface cover for Cenozoic climate evolution.

  14. Parallel Computing of Ocean General Circulation Model

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    This paper discusses the parallel computing of the thirdgeneration Ocea n General Circulation Model (OGCM) from the State Key Laboratory of Numerical Mo deling for Atmospheric Science and Geophysical Fluid Dynamics(LASG),Institute of Atmosphere Physics(IAP). Meanwhile, several optimization strategies for paralle l computing of OGCM (POGCM) on Scalable Shared Memory Multiprocessor (S2MP) are presented. Using Message Passing Interface (MPI), we obtain super linear speedup on SGI Origin 2000 for parallel OGCM(POGCM) after optimization.

  15. Microwave circulator design

    CERN Document Server

    Linkhart, Douglas K

    2014-01-01

    Circulator design has advanced significantly since the first edition of this book was published 25 years ago. The objective of this second edition is to present theory, information, and design procedures that will enable microwave engineers and technicians to design and build circulators successfully. This resource contains a discussion of the various units used in the circulator design computations, as well as covers the theory of operation. This book presents numerous applications, giving microwave engineers new ideas about how to solve problems using circulators. Design examples are provided, which demonstrate how to apply the information to real-world design tasks.

  16. 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.

  17. Mountains and Tropical Circulation

    Science.gov (United States)

    Naiman, Z.; Goodman, P. J.; Krasting, J. P.; Malyshev, S.; Russell, J. L.; Stouffer, R. J.

    2015-12-01

    Observed tropical convection exhibits zonal asymmetries that strongly influence spatial precipitation patterns. The drivers of changes to this zonally-asymmetric Walker circulation on decadal and longer timescales have been the focus of significant recent research. Here we use two state-of-the-art earth system models to explore the impact of earth's mountains on the Walker circulation. When all land-surface topography is removed, the Walker circulation weakens by 33-59%. There is a ~30% decrease in global, large-scale upward vertical wind velocities in the middle of the troposphere, but only minor changes in global average convective mass flux, precipitation, surface and sea-surface temperatures. The zonally symmetric Hadley circulation is also largely unchanged. Following the spatial pattern of changes to large-scale vertical wind velocities, precipitation becomes less focused over the tropics. The weakening of the Walker circulation, but not the Hadley circulation, is similar to the behavior of climate models during radiative forcing experiments: in our simulations, the weakening is associated with changes in vertical wind velocities, rather than the hydrologic cycle. These results indicate suggest that mountain heights may significantly influence the Walker circulation on geologic time scales, and observed changes in tropical precipitation over millions of years may have been forced by changes in tropical orography.

  18. Ensemble meteorological reconstruction using circulation analogues of 1781–1785

    Directory of Open Access Journals (Sweden)

    P. Yiou

    2013-09-01

    Full Text Available This paper uses a method of atmospheric flow analogues to reconstruct an ensemble of atmospheric variables (namely sea-level pressure, surface temperature and wind speed between 1781 and 1785. The properties of this ensemble are investigated and tested against observations of temperature. The goal of the paper is to assess whether the atmospheric circulation during the Laki volcanic eruption (in 1783 and the subsequent winter were similar to the conditions that prevailed in the winter 2009/2010 and during spring 2010. We find that the three months following the Laki eruption in June 1783 barely have analogues in 2010. The cold winter of 1783/1784 yields circulation analogues in 2009/2010. Our analysis suggests that it is unlikely that the Laki eruption was responsible for the cold winter of 1783/1784, of the relatively short memory of the atmospheric circulation.

  19. FORMATION AND PLASMA CIRCULATION OF SOLAR PROMINENCES

    OpenAIRE

    Xia, Chun; Keppens, Rony

    2016-01-01

    Solar prominences are long-lived cool and dense plasma curtains in the hot and rarefied outer solar atmosphere or corona. The physical mechanism responsible for their formation and especially for their internal plasma circulation has been uncertain for decades. The observed ubiquitous down flows in quiescent prominences are difficult to interpret as plasma with high conductivity seems to move across horizontal magnetic field lines. Here we present three-dimensional numerical simulations of pr...

  20. Learning Circulant Sensing Kernels

    Science.gov (United States)

    2014-03-01

    learned dictionaries. Examples of analytic dictionaries include the discrete cosine basis, various wavelets bases , as well as tight frames. Some of them...Compressive sensing based high resolution channel estimation for OFDM system. To appear in IEEE Journal of Selected Topics in Signal Processing, Special...theoretical and computational properties to a (partial) circulant matrix of the same size, our discussions below are based exclusively on the circulant

  1. Study on mechanism of interdecadal Atlantic thermohaline circulation variability Ⅲ.Influences of inter-decadal variations by ocean-atmosphere elements%大西洋热盐环流年代际变化机制研究Ⅲ.北大西洋海气要素对热盐环流年代际振荡的影响

    Institute of Scientific and Technical Information of China (English)

    牟林; 陈学恩; 宋军; 李欢; 李琰; 姜晓轶; 李海; 陈幸荣

    2011-01-01

    Using the advanced climate ocean-atmosphere coupled model described in the first paper of this series of studies, response analyses of inter-decadal variations of the Atlantic thermohaline circulation by ocean-atmosphere elements were deliberated. For studying the relationship between the ocean elements of the North Atlantic and inter-decadal variations of Atlantic thermohaline circulation, subpolar sea-surface-density index (SSI) and North-Atlantic-Current Strength Index (NSI) were defined and analyzed. The results of analyses indicate that SSI changes 7 years earlier than Atlantic meridional overturning circulation (MOO while NSI changing 4 years earlier than MOC. The strength of water overflows from Greenland-Scotland sea ridge (including Denmark Strait and Faro Strait), which is an important water resource ofNorth Atlantic deep water, changes 3 years ahead MOC. The inter-decadal variations of Atlantic thermohaline circulation THC are influenced by North Atlantic atmosphere elements significantly. 2 years before subpolar current and North Atlantic Current (NAC) reaching their full strength, High-latitude atmosphere is abnormal in the pattern of cyclonic circulation and middle-latitude atmosphere is abnormal in the pattern of anticyclonic circulation. Meanwhile, the sea surface heat flux in Atlantic subpolar sea area is negative anomaly. All of those abnormal conditions enhance the strength of subpolar current and NAC. More water with higher salinity intruding into Greenland-Icelandic-Norwegian Sea (GIN) brings higher sea surface density of GIN. This weakens the stability of water stratification and increases the probability of occurrence of deep convection. Meanwhile, the variation of atmosphere influences the deep water generating process in GIN by the curl of wind stress and sea surface heat flux. Then the strength of water overflows from Greenland-Scotland sea ridge is strengthened.%基于该系列文章前文研究中构建的海气耦合气候模式和所

  2. Variability in warm-season atmospheric circulation and precipitation patterns over subtropical South America: relationships between the South Atlantic convergence zone and large-scale organized convection over the La Plata basin

    Science.gov (United States)

    Mattingly, Kyle S.; Mote, Thomas L.

    2017-01-01

    Warm-season precipitation variability over subtropical South America is characterized by an inverse relationship between the South Atlantic convergence zone (SACZ) and precipitation over the central and western La Plata basin of southeastern South America. This study extends the analysis of this "South American Seesaw" precipitation dipole to relationships between the SACZ and large, long-lived mesoscale convective systems (LLCSs) over the La Plata basin. By classifying SACZ events into distinct continental and oceanic categories and building a logistic regression model that relates LLCS activity across the region to continental and oceanic SACZ precipitation, a detailed account of spatial variability in the out-of-phase coupling between the SACZ and large-scale organized convection over the La Plata basin is provided. Enhanced precipitation in the continental SACZ is found to result in increased LLCS activity over northern, northeastern, and western sections of the La Plata basin, in association with poleward atmospheric moisture flux from the Amazon basin toward these regions, and a decrease in the probability of LLCS occurrence over the southeastern La Plata basin. Increased oceanic SACZ precipitation, however, was strongly related to reduced atmospheric moisture and decreased probability of LLCS occurrence over nearly the entire La Plata basin. These results suggest that continental SACZ activity and large-scale organized convection over the northern and eastern sections of the La Plata basin are closely tied to atmospheric moisture transport from the Amazon basin, while the warm coastal Brazil Current may also play an important role as an evaporative moisture source for LLCSs over the central and western La Plata basin.

  3. Variability in warm-season atmospheric circulation and precipitation patterns over subtropical South America: relationships between the South Atlantic convergence zone and large-scale organized convection over the La Plata basin

    Science.gov (United States)

    Mattingly, Kyle S.; Mote, Thomas L.

    2016-03-01

    Warm-season precipitation variability over subtropical South America is characterized by an inverse relationship between the South Atlantic convergence zone (SACZ) and precipitation over the central and western La Plata basin of southeastern South America. This study extends the analysis of this "South American Seesaw" precipitation dipole to relationships between the SACZ and large, long-lived mesoscale convective systems (LLCSs) over the La Plata basin. By classifying SACZ events into distinct continental and oceanic categories and building a logistic regression model that relates LLCS activity across the region to continental and oceanic SACZ precipitation, a detailed account of spatial variability in the out-of-phase coupling between the SACZ and large-scale organized convection over the La Plata basin is provided. Enhanced precipitation in the continental SACZ is found to result in increased LLCS activity over northern, northeastern, and western sections of the La Plata basin, in association with poleward atmospheric moisture flux from the Amazon basin toward these regions, and a decrease in the probability of LLCS occurrence over the southeastern La Plata basin. Increased oceanic SACZ precipitation, however, was strongly related to reduced atmospheric moisture and decreased probability of LLCS occurrence over nearly the entire La Plata basin. These results suggest that continental SACZ activity and large-scale organized convection over the northern and eastern sections of the La Plata basin are closely tied to atmospheric moisture transport from the Amazon basin, while the warm coastal Brazil Current may also play an important role as an evaporative moisture source for LLCSs over the central and western La Plata basin.

  4. Gaussian Fibonacci Circulant Type Matrices

    Directory of Open Access Journals (Sweden)

    Zhaolin Jiang

    2014-01-01

    Full Text Available Circulant matrices have become important tools in solving integrable system, Hamiltonian structure, and integral equations. In this paper, we prove that Gaussian Fibonacci circulant type matrices are invertible matrices for n>2 and give the explicit determinants and the inverse matrices. Furthermore, the upper bounds for the spread on Gaussian Fibonacci circulant and left circulant matrices are presented, respectively.

  5. Geophysical Plasmas and Atmospheric Modeling.

    Science.gov (United States)

    1982-01-01

    will be submitted to the Journal of the Atmospheric Sciences. 32 - .- I. LIMITATIONS ON STRATOSPHERIC DYNAMICS We have performed an investigation of...Amplitudes" which will be submitted to the Journal of the Atmospheric Sciences. 1i 33 A& J. GENERAL CIRCULATION MODEL STUDIES Comparison computer runs...In tis case, as clearly shov.i by Petvia-mensona. I ths cseas ceary sou byPetia- cavities requires a local theory going beyond the limitshvilli,’ the

  6. Circulant Double Coverings of a Circulant Graph of Valency Five

    Institute of Scientific and Technical Information of China (English)

    Rong Quan FENG; Jin Ho KWAK

    2007-01-01

    Enumerating the isomorphism classes of several types of graph covering projections is one of the central research topics in enumerative topological graph theory. A covering of G is called circulant if its covering graph is circulant. Recently, the authors [Discrete Math., 277, 73-85 (2004)]enumerated the isomorphism classes of circulant double coverings of a certain type, called a typicalcovering, and showed that no double covering of a circulant graph of valency three is circulant. Also, in [Graphs and Combinatorics, 21, 386-400 (2005)], the isomorphism classes of circulant double coverings of a circulant graph of valency four are enumerated. In this paper, the isomorphism classes of circulant double coverings of a circulant graph of valency five are enumerated.

  7. Kernels in circulant digraphs

    Directory of Open Access Journals (Sweden)

    R. Lakshmi

    2014-06-01

    Full Text Available A kernel $J$ of a digraph $D$ is an independent set of vertices of $D$ such that for every vertex $w,in,V(D,setminus,J$ there exists an arc from $w$ to a vertex in $J.$ In this paper, among other results, a characterization of $2$-regular circulant digraph having a kernel is obtained. This characterization is a partial solution to the following problem: Characterize circulant digraphs which have kernels; it appeared in the book {it Digraphs - theory, algorithms and applications}, Second Edition, Springer-Verlag, 2009, by J. Bang-Jensen and G. Gutin.

  8. Walker circulation in a transient climate

    Science.gov (United States)

    Plesca, Elina; Grützun, Verena; Buehler, Stefan A.

    2016-04-01

    response (temperature change by the time of CO2 doubling), which in turn might be related to a decreased ocean heat uptake. This uncertainty across the models we attribute to the multitude of factors controlling ocean and atmosphere heat exchange, both at global and regional scales, as well as to the present capabilities of GCMs in simulating this exchange. References: England, M. H., McGregor, S., Spence, P., Meehl, G. A., Timmermann, A., Cai, W., Gupta, A. S., McPhaden, M. J., Purich, A., and Santoso, A., 2014. Recent intensification of wind-driven circulation in the Pacific and the ongoing warming hiatus. Nature Climate Change 4 (3): 222-227. Ma, J., and Xie, S. P., 2013. Regional Patterns of Sea Surface Temperature Change: A Source of Uncertainty in Future Projections of Precipitation and Atmospheric Circulation*. Journal of Climate, 26 (8): 2482-2501

  9. Observations of Exoplanet Atmospheres

    CERN Document Server

    Crossfield, Ian J M

    2015-01-01

    Detailed characterization of an extrasolar planet's atmosphere provides the best hope for distinguishing the makeup of its outer layers, and the only hope for understanding the interplay between initial composition, chemistry, dynamics & circulation, and disequilibrium processes. In recent years, some areas have seen rapid progress while developments in others have come more slowly and/or have been hotly contested. This article gives an observer's perspective on the current understanding of extrasolar planet atmospheres prior to the considerable advances expected from the next generation of observing facilities. Atmospheric processes of both transiting and directly-imaged planets are discussed, including molecular and atomic abundances, cloud properties, thermal structure, and planetary energy budgets. In the future we can expect a continuing and accelerating stream of new discoveries, which will fuel the ongoing exoplanet revolution for many years to come.

  10. Response of Atmospheric General Circulation to Oceanic Temperature's Reemergence in the Gulf Stream in North Atlantic%大气环流对北大西洋湾流区海温"再现"的响应

    Institute of Scientific and Technical Information of China (English)

    屈丽玮; 李春; 马浩

    2010-01-01

    利用全球海洋-大气快速耦合模式(Fast Ocean-Atmosphere Model,FOAM),采用模式中的初值方法,研究了湾流区海温再现过程及其对北半球大气环流和气候的影响.FOAM模式很好地模拟了北大西洋湾流区的海温"再现"过程,模式中海面热通量异常与SST异常表现出不同步的响应特征.海面热通量异常在初冬季节达到最大值,而SST异常滞后,在冬季晚期达到最大值,从而在初冬和晚冬对北半球大气环流造成不同的影响.初冬季节北半球大气环流主要受海洋热通量异常的强迫,在北大西洋和北太平洋上空呈现相当正压的异常低压槽响应,北极地区为异常高压脊,类似北极涛动的负位相,可能造成欧洲南部和北非大陆气温偏高,亚洲大陆气温偏低.而晚冬季节北半球大气环流主要受SST异常的驱动,在北大西洋和北太平洋上空表现为相当正压的异常高压脊响应,北极地区为异常低压槽,类似北极涛动的正位相,可能造成欧洲南部和北非大陆气温偏低,亚洲大陆气温偏高,中国东部降水异常偏多30%左右.北太平洋大气环流的异常由北大西洋湾流区海洋热通量和SST异常强迫下游大气环流所激发,进一步通过Rossby驻波的能量频散东传至北太平洋而造成的.

  11. Seasonal Evolution of Titan's Atmospheric Polar Vortices

    Science.gov (United States)

    Teanby, Nicholas A.; Irwin, P. G.; Nixon, C. A.; de Kok, R.; Vinatier, S.; Coustenis, A.; Sefton-Nash, E.; Calcutt, S. B.; Flasar, F. M.

    2013-10-01

    Titan is the largest satellite of Saturn and is the only moon in our solar system to have a significant atmosphere. Titan's middle-atmosphere circulation usually comprises a single hemisphere-to-hemisphere meridional circulation cell, with upwelling air in the summer hemisphere and subsiding air at the winter pole with an associated winter polar vortex. Titan has an axial tilt (obliquity) of 26.7degrees, so during its 29.5 Earth year annual cycle pronounced seasonal effects are expected as the relative solar insolation in each hemisphere changes. The most dramatic of these changes is predicted to be the reversal in global meridional circulation as the peak solar heating switches hemispheres after an equinox. Since northern spring equinox in mid-2009, Titan's atmosphere has demonstrated dramatic changes in temperature, composition, and aerosol distribution. These changes indicate major changes to the atmospheric circulation pattern have indeed occurred. Here we use nine years of Cassini/CIRS infrared spectra to determine the temperature and composition evolution of the atmosphere through northern-fall to northern-spring. Particularly dramatic changes are observed at the poles, where a new south polar hot-spot/vortex has been forming. The north polar vortex also appears to be weakening throughout this period. Furthermore, the meridional circulation reversal, predicted by numerical models, occurred a mere six months after equinox, showing that despite Titan's long annual cycle, rapid changes are possible. This gives us new insight into vortex formation processes and atmospheric dynamics.

  12. Formation and plasma circulation of solar prominences

    CERN Document Server

    Xia, Chun

    2016-01-01

    Solar prominences are long-lived cool and dense plasma curtains in the hot and rarefied outer solar atmosphere or corona. The physical mechanism responsible for their formation and especially for their internal plasma circulation has been uncertain for decades. The observed ubiquitous down flows in quiescent prominences are difficult to interpret as plasma with high conductivity seems to move across horizontal magnetic field lines. Here we present three-dimensional numerical simulations of prominence formation and evolution in an elongated magnetic flux rope as a result of in-situ plasma condensations fueled by continuous plasma evaporation from the solar chromosphere. The prominence is born and maintained in a fragmented, highly dynamic state with continuous reappearance of multiple blobs and thread structures that move mainly downward dragging along mass-loaded field lines. The prominence plasma circulation is characterized by the dynamic balance between the drainage of prominence plasma back to the chromos...

  13. Decadal Variation of Summer Dryness/Wetness over the Middle and Lower Reaches of the Yangtze River and the Evolution of Atmospheric Circulation in the Last 52 Years%近52年长江中下游地区夏季年代际尺度干湿变化及其环流演变分析

    Institute of Scientific and Technical Information of China (English)

    李淑萍; 侯威; 封泰晨

    2015-01-01

    2012, provided by the National Climate Center of the China Meteorological Administration, were used to calculate the Standardized Precipitation Index in summer. The Mann–Kendall (MK) statistical test was applied to detect the trend in the number of stations at which summer SPI reached a value of−1.0 or less. According to the MK test results, the whole time series could be divided into three stages, separated by abrupt change points. Furthermore, based on National Centers for Environmental Prediction/National Center for Atmospheric Research reanalysis data and National Oceanic and Atmospheric Administration extended reconstructed sea surface temperature (SST) data, the evolution of the large-scale atmospheric circulation was analyzed from pre-winter to summer, and a conceptual model established for each stage. The results showed that: (1) the first stage (1961–1973) was in an obvious state of drought, the second stage (1974–1986) was a dry-to-wet transition phase, and the third stage (1987–2012) was basically wet; (2) the atmospheric circulation changed notably in the second stage, leading to an opposite phase of the circulation anomaly between the first and third stages; and (3) global SST remained abnormally cold from pre-winter to summer, and Indian Ocean SST was especially colder in summer, which led to a dramatically weaker South Asian high and western Pacific subtropical high. The high pressure ridge over the northern Tibetan Plateau was weaker, resulting in weaker high pressure over Mongolia in pre-winter. Low pressure over India was stronger, the southern branch of the trough deepened, and southerly moisture transported by the summer monsoon prevailed over eastern China. Meanwhile, there was straight westerly wind over the mid-high latitudes of Asia, which was unfavorable for the cold air to extend into southern China. Under the above evolution and configuration of the atmospheric circulation, the middle and lower reaches of the Yangtze River were

  14. The fetal circulation.

    Science.gov (United States)

    Kiserud, Torvid; Acharya, Ganesh

    2004-12-30

    Accumulating data on the human fetal circulation shows the similarity to the experimental animal physiology, but with important differences. The human fetus seems to circulate less blood through the placenta, shunt less through the ductus venosus and foramen ovale, but direct more blood through the lungs than the fetal sheep. However, there are substantial individual variations and the pattern changes with gestational age. The normalised umbilical blood flow decreases with gestational age, and, at 28 to 32 weeks, a new level of development seems to be reached. At this stage, the shunting through the ductus venosus and the foramen ovale reaches a minimum, and the flow through the lungs a maximum. The ductus venosus and foramen ovale are functionally closely related and represent an important distributional unit for the venous return. The left portal branch represents a venous watershed, and, similarly, the isthmus aorta an arterial watershed. Thus, the fetal central circulation is a very flexible and adaptive circulatory system. The responses to increased afterload, hypoxaemia and acidaemia in the human fetus are equivalent to those found in animal studies: increased ductus venosus and foramen ovale shunting, increased impedance in the lungs, reduced impedance in the brain, increasingly reversed flow in the aortic isthmus and a more prominent coronary blood flow.

  15. Warm World Ocean Thermohaline Circulation Model

    Science.gov (United States)

    Zimov, N.; Zimov, S. A.

    2014-12-01

    Modern day ocean circulation is dominated by thermal convection with cold waters subsiding in the Northern Atlantic, filling the ocean interior with cold and heavy water. However, ocean circulation diminished during the last glaciation and consequently the downwelling of the cold. Therefore interior ocean water temperatures must have been affected by other mechanisms which are negligible in the current state. We propose that the submergence of highly saline water from warm seas with high rates of evaporation (like the Red or Mediterranean Sea) was a major factor controlling ocean circulation during the last glaciation. Even today, waters in these poorly connected seas are the heaviest waters in the World ocean (1.029 g/cm3). The second mechanism affecting ocean temperature is the geothermal heat flux. With no heat exchange between the atmosphere and the ocean, geothermal heat flux through the ocean floor is capable of increasing ocean temperature by tens of degrees C over a 100 thousand year glacial cycle. To support these hypotheses we present an ocean box model that describes thermohaline circulation in the World Ocean. According to the model parameters, all water circulation is driven by the water density gradient. Boxes include high-latitude seas, high salinity seas, surface ocean, glaciers, and rift and lateral zones of the ocean interior. External heat sources are radiative forcing, affected by Milankovich cycles, and geothermal heat flux. Additionally this model accounts for the heat produced by organic rain decay. Taking all input parameters close to currently observed values, the model manages to recreate the glacial-interglacial cycles. During the glacial periods only haline circulation takes place, the ocean is strongly stratified, and the interior ocean accumulates heat while high-latitudes accumulate ice. 112,000 years after glaciation starts, water density on the ocean bottom becomes equal to the density of water in high-latitude seas, strong thermal

  16. 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 coup

  17. 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.)

  18. Cereral Circulation in Preeclampsia

    Directory of Open Access Journals (Sweden)

    A. A. Ivshin

    2008-01-01

    Full Text Available Objective: to evaluate the possibilities of using transcranial Doppler study in pregnant women and pueperas with preeclamp-sia. Subjects and methods. Two hundred and thirty-two pregnant women diagnosed as having varying preeclampsia were prospectively studied. A comparison group comprised 90 apparently healthy women in the third trimester of pregnancy. All the respondents underwent transcranial duplex scanning of the medial cerebral artery with the linear velocity values being determined. A number of the values reflecting the level of perfusion and intracranial pressures, hydrodynamic resistance in the system, cerebrovascular responsiveness and the state of the vascular wall were calculated. Correlation analysis was made between the parameters of cerebral circulation and the severity of preeclampsia, proteinuria, the severity of hydrops, and the parameters of central and peripheral hemodynamics. Results. The findings suggest that there is impaired cerebral perfusion in pregnant women and puerperas with varying preeclampsia, the severity of cerebral circulatory disorders being in proportion with that of preeclampsia. There is a close correlation between cerebral circulation and the individual criteria determining the severity of preeclampsia. The linear values of the Doppler spectrum, namely linear flow characteristics, are prognos-tically most significant. Conclusion. The introduction of transcranial Doppler study into obstetric care has permitted the authors not only to study cerebral circulatory disorders in healthy and pregnant women and puerperas with preeclampia in detail, but also to establish a number of highly significant prognostic criteria for the severity of this life-threatening complication of gestation. The results of transcranial Doppler study assist practitioners in timely and accurately solving the problems in the diagnosis of preeclampsia and in evaluating its severity. Cerebral circulatory values may be successfully used to

  19. Resolvability in Circulant Graphs

    Institute of Scientific and Technical Information of China (English)

    Muhammad SALMAN; Imran JAVAID; Muhammad Anwar CHAUDHRY

    2012-01-01

    A set W of the vertices of a connected graph G is called a resolving set for G if for every two distinct vertices u,v ∈ V(G) there is a vertex w ∈ W such that d(u,w) ≠ d(v,w).A resolving set of minimum cardinality is called a metric basis for G and the number of vertices in a metric basis is called the metric dimension of G,denoted by dim(G).For a vertex u of G and a subset S of V(G),the distance between u and S is the number mins∈s d(u,s).A k-partition H ={S1,S2,...,Sk} of V(G) is called a resolving partition if for every two distinct vertices u,v ∈ V(G) there is a set Si in Π such that d(u,Si) ≠ d(v,Si).The minimum k for which there is a resolving k-partition of V(G) is called the partition dimension of G,denoted by pd(G).The circulant graph is a graph with vertex set Zn,an additive group ofintegers modulo n,and two vertices labeled i and j adjacent if and only if i - j (mod n) ∈ C,where C C Zn has the property that C =-C and 0(∈) C.The circulant graph is denoted by Xn,△ where A =|C|.In this paper,we study the metric dimension of a family of circulant graphs Xn,3 with connection set C ={1,-n/2,n - 1} and prove that dim(Xn,3) is independent of choice of n by showing that 3 for all n =0 (mod 4),dim(X,n,3) ={ 4 for all n =2 (mod 4).We also study the partition dimension of a family of circulant graphs Xn,4 with connection set C ={±1,±2} and prove that pd(Xn,4) is independent of choice of n and show that pd(X5,4) =5 and 3 forall odd n≥9,pd(Xn,4) ={ 4 for all even n ≥ 6 and n =7.

  20. Staging atmospheres

    DEFF Research Database (Denmark)

    Bille, Mikkel; Bjerregaard, Peter; Sørensen, Tim Flohr

    2015-01-01

    The article introduces the special issue on staging atmospheres by surveying the philosophical, political and anthropological literature on atmosphere, and explores the relationship between atmosphere, material culture, subjectivity and affect. Atmosphere seems to occupy one of the classic...... localities of tensions between matter and the immaterial, the practical and the ideal, and subject and object. In the colloquial language there can, moreover, often seem to be something authentic or genuine about atmosphere, juxtaposing it to staging, which is implied to be something simulated or artificial....... This introduction seeks to outline how a number of scholars have addressed the relationship between staged atmospheres and experience, and thus highlight both the philosophical, social and political aspects of atmospheres...

  1. The response of Mediterranean thermohaline circulation to climate change: a minimal model

    OpenAIRE

    Meijer, P.Th.; H. A. Dijkstra

    2009-01-01

    Physics-based understanding of the effects of paleoclimate and paleogeography on the thermohaline circulation of the Mediterranean Sea requires an ocean model capable of long integrations and involving a minimum of assumptions about the atmospheric forcing. Here we examine the sensitivity of the deep circulation in the eastern Mediterranean basin to changes in atmospheric forcing, considered a key factor in the deposition of organic-rich sediments (sapropels). To this extent we explore the se...

  2. Twentieth century Walker Circulation change: data analysis and model experiments

    Energy Technology Data Exchange (ETDEWEB)

    Meng, Qingjia [Leibniz-Institut fuer Meereswissenschaften, Kiel (Germany); Chinese Research Academy of Environmental Sciences, River and Coastal Environment Research Center, Beijing (China); Chinese Academy of Sciences, Key Laboratory of Ocean Circulation and Waves, Institute of Oceanology, Qingdao (China); Latif, Mojib; Park, Wonsun; Keenlyside, Noel S.; Martin, Thomas [Leibniz-Institut fuer Meereswissenschaften, Kiel (Germany); Semenov, Vladimir A. [Leibniz-Institut fuer Meereswissenschaften, Kiel (Germany); A.M. Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences, Moscow (Russian Federation)

    2012-05-15

    Recent studies indicate a weakening of the Walker Circulation during the twentieth century. Here, we present evidence from an atmospheric general circulation model (AGCM) forced by the history of observed sea surface temperature (SST) that the Walker Circulation may have intensified rather than weakened. Observed Equatorial Indo-Pacific Sector SST since 1870 exhibited a zonally asymmetric evolution: While the eastern part of the Equatorial Pacific showed only a weak warming, or even cooling in one SST dataset, the western part and the Equatorial Indian Ocean exhibited a rather strong warming. This has resulted in an increase of the SST gradient between the Maritime Continent and the eastern part of the Equatorial Pacific, one driving force of the Walker Circulation. The ensemble experiments with the AGCM, with and without time-varying external forcing, suggest that the enhancement of the SST gradient drove an anomalous atmospheric circulation, with an enhancement of both Walker and Hadley Circulation. Anomalously strong precipitation is simulated over the Indian Ocean and anomalously weak precipitation over the western Pacific, with corresponding changes in the surface wind pattern. Some sensitivity to the forcing SST, however, is noticed. The analysis of twentieth century integrations with global climate models driven with observed radiative forcing obtained from the Coupled Model Intercomparison Project (CMIP) database support the link between the SST gradient and Walker Circulation strength. Furthermore, control integrations with the CMIP models indicate the existence of strong internal variability on centennial timescales. The results suggest that a radiatively forced signal in the Walker Circulation during the twentieth century may have been too weak to be detectable. (orig.)

  3. Thermohaline circulations and global climate change. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Hanson, H.P.

    1996-10-01

    This report discusses results from the project entitled Thermohaline Circulations and Global Climate Change. Results are discussed in three sections related to the development of the Miami Isopycnic Coordinate Ocean Model (MICOM), surface forcing of the ocean by the atmosphere, and experiments with the MICOM related to the problem of the ocean`s response to global climate change. It will require the use of a global, coupled ocean-atmospheric climate model to quantify the feedbacks between ocean and atmosphere associated with climate changes. The results presented here do provide guidance for such studies in the future.

  4. Circulation of Stars

    Science.gov (United States)

    Boitani, P.

    2016-01-01

    Since the dawn of man, contemplation of the stars has been a primary impulse in human beings, who proliferated their knowledge of the stars all over the world. Aristotle sees this as the product of primeval and perennial “wonder” which gives rise to what we call science, philosophy, and poetry. Astronomy, astrology, and star art (painting, architecture, literature, and music) go hand in hand through millennia in all cultures of the planet (and all use catasterisms to explain certain phenomena). Some of these developments are independent of each other, i.e., they take place in one culture independently of others. Some, on the other hand, are the product of the “circulation of stars.” There are two ways of looking at this. One seeks out forms, the other concentrates on the passing of specific lore from one area to another through time. The former relies on archetypes (for instance, with catasterism), the latter constitutes a historical process. In this paper I present some of the surprising ways in which the circulation of stars has occurred—from East to West, from East to the Far East, and from West to East, at times simultaneously.

  5. Formation and Plasma Circulation of Solar Prominences

    Science.gov (United States)

    Xia, C.; Keppens, R.

    2016-05-01

    Solar prominences are long-lived cool and dense plasma curtains in the hot and rarefied outer solar atmosphere or corona. The physical mechanism responsible for their formation and especially for their internal plasma circulation has been uncertain for decades. The observed ubiquitous downflows in quiescent prominences are difficult to interpret because plasma with high conductivity seems to move across horizontal magnetic field lines. Here we present three-dimensional numerical simulations of prominence formation and evolution in an elongated magnetic flux rope as a result of in situ plasma condensations fueled by continuous plasma evaporation from the solar chromosphere. The prominence is born and maintained in a fragmented, highly dynamic state with continuous reappearance of multiple blobs and thread structures that move mainly downward, dragging along mass-loaded field lines. The circulation of prominence plasma is characterized by the dynamic balance between the drainage of prominence plasma back to the chromosphere and the formation of prominence plasma via continuous condensation. Plasma evaporates from the chromosphere, condenses into the prominence in the corona, and drains back to the chromosphere, establishing a stable chromosphere-corona plasma cycle. Synthetic images of the modeled prominence with the Solar Dynamics Observatory Atmospheric Imaging Assembly closely resemble actual observations, with many dynamical threads underlying an elliptical coronal cavity.

  6. Paleoclimate and Amerindians: evidence from stable isotopes and atmospheric circulation.

    Science.gov (United States)

    Lovvorn, M B; Frison, G C; Tieszen, L L

    2001-02-27

    Two Amerindian demographic shifts are attributed to climate change in the northwest plains of North America: at approximately 11,000 calendar years before present (yr BP), Amerindian culture apparently split into foothills-mountains vs. plains biomes; and from 8,000-5,000 yr BP, scarce archaeological sites on the open plains suggest emigration during xeric "Altithermal" conditions. We reconstructed paleoclimates from stable isotopes in prehistoric bison bone and relations between weather and fractions of C(4) plants in forage. Further, we developed a climate-change model that synthesized stable isotope, existing qualitative evidence (e.g., palynological, erosional), and global climate mechanisms affecting this midlatitude region. Our isotope data indicate significant warming from approximately 12,400 to 11,900 yr BP, supporting climate-driven cultural separation. However, isotope evidence of apparently wet, warm conditions at 7,300 yr BP refutes emigration to avoid xeric conditions. Scarcity of archaeological sites is best explained by rapid climate fluctuations after catastrophic draining of the Laurentide Lakes, which disrupted North Atlantic Deep Water production and subsequently altered monsoonal inputs to the open plains.

  7. Levoglucosan on Tibetan glaciers under different atmospheric circulations

    Science.gov (United States)

    You, Chao; Yao, Tandong; Xu, Chao; Song, Lili

    2017-03-01

    Tibetan glaciers are natural documents of the specific biomass burning biomarker levoglucosan from regions around. However, knowledge about the characteristics of levoglucosan distributions on Tibetan glaciers under the different climate systems is poorly understood. In this study, we detected levoglucosan in snow samples from the Zuoqiupu (ZQP) Glacier affected by the Indian summer monsoon and the Muji (MJ) Glacier dominated by the westerlies. Results found that the ZQP Glacier was more heavily affected by fire emissions than the MJ Glacier, caused by stronger emission sources on the windward direction and shorter transport distances. Elevations for the appearance of levoglucosan maxima on glacier surfaces are roughly around the equilibrium line altitudes. However, levoglucosan displays a wider distribution range on the MJ glacier than on the ZQP glacier due to weaker summer melt. Injection height of fire smokes and glacial melt can affect the altitudinal distribution of levoglucosan. Black carbon and levoglucosan show different temporal variations in snow-pit samples on those two glaciers. The post-depositional effects, e.g. the melting and refreezing processes, can modulate the vertical distribution of levoglucosan in snow/ice layers. Our results are helpful for understanding the geochemical behaviors of levoglucosan happened on Tibetan glacier surfaces.

  8. Exoplanet Atmospheres

    CERN Document Server

    Seager, S

    2010-01-01

    At the dawn of the first discovery of exoplanets orbiting sun-like stars in the mid-1990s, few believed that observations of exoplanet atmospheres would ever be possible. After the 2002 Hubble Space Telescope detection of a transiting exoplanet atmosphere, many skeptics discounted it as a one-object, one-method success. Nevertheless, the field is now firmly established, with over two dozen exoplanet atmospheres observed today. Hot Jupiters are the type of exoplanet currently most amenable to study. Highlights include: detection of molecular spectral features; observation of day-night temperature gradients; and constraints on vertical atmospheric structure. Atmospheres of giant planets far from their host stars are also being studied with direct imaging. The ultimate exoplanet goal is to answer the enigmatic and ancient question, "Are we alone?" via detection of atmospheric biosignatures. Two exciting prospects are the immediate focus on transiting super Earths orbiting in the habitable zone of M-dwarfs, and u...

  9. Atmospheric Neutrinos

    OpenAIRE

    Takaaki Kajita

    1994-01-01

    Atmospheric neutrinos are produced as decay products in hadronic showers resulting from collisions of cosmic rays with nuclei in the atmosphere. Electron-neutrinos and muon-neutrinos are produced mainly by the decay chain of charged pions to muons to electrons. Atmospheric neutrino experiments observed zenith angle and energy-dependent deficit of muon-neutrino events. It was found that neutrino oscillations between muon-neutrinos and tau-neutrinos explain these data well. This paper discusses...

  10. Articulating Atmospheres

    DEFF Research Database (Denmark)

    Kinch, Sofie

    2011-01-01

    This paper presents an architectural approach to designing computational interfaces by articulating the notion of atmosphere in the field of interaction design. It draws upon the concept of kinesthetic interaction and a philosophical notion on atmosphere emphasizing the importance of bodily...... experience in space, presented as middle ground experience. In the field of HCI, middle ground experiences complete the unarticulated spectrum between designing for foreground of attention or background awareness. When “Articulating Atmospheres through Middle Ground Experiences in Interaction Design...

  11. Lost circulation technology development status

    Energy Technology Data Exchange (ETDEWEB)

    Glowka, D.A.; Schafer, D.M.; Loeppke, G.E.; Scott, D.D.; Wernig, M.D.; Wright, E.K.

    1992-07-01

    Lost circulation is the loss of drilling fluid from the wellbore to fractures or pores in the rock formation. In geothermal drilling, lost circulation is often a serious problem that contributes greatly to the cost of the average geothermal well. The Lost Circulation Technology Development Program is sponsored at Sandia National Laboratories by the US Department of Energy. The goal of the program is to reduce lost circulation costs by 30--50% through the development of mitigation and characterization technology. This paper describes the technical progress made in this program during the period April 1991--March 1992. 8 refs.

  12. Percutaneous interventions in Fontan circulation

    Directory of Open Access Journals (Sweden)

    Eduardo Franco

    2015-09-01

    Conclusions: Interventional catheterization procedures are often necessary to reach and maintain the fragile Fontan circulation, mainly in patients with right morphology systemic ventricles and fenestrated Fontan conduits.

  13. Atmospheric Neutrinos

    Directory of Open Access Journals (Sweden)

    Takaaki Kajita

    2012-01-01

    Full Text Available Atmospheric neutrinos are produced as decay products in hadronic showers resulting from collisions of cosmic rays with nuclei in the atmosphere. Electron-neutrinos and muon-neutrinos are produced mainly by the decay chain of charged pions to muons to electrons. Atmospheric neutrino experiments observed zenith angle and energy-dependent deficit of muon-neutrino events. It was found that neutrino oscillations between muon-neutrinos and tau-neutrinos explain these data well. This paper discusses atmospheric neutrino experiments and the neutrino oscillation studies with these neutrinos.

  14. Atmospheric electricity

    CERN Document Server

    Chalmers, J Alan

    1957-01-01

    Atmospheric Electricity brings together numerous studies on various aspects of atmospheric electricity. This book is composed of 13 chapters that cover the main problems in the field, including the maintenance of the negative charge on the earth and the origin of the charges in thunderstorms. After a brief overview of the historical developments of atmospheric electricity, this book goes on dealing with the general principles, results, methods, and the MKS system of the field. The succeeding chapters are devoted to some aspects of electricity in the atmosphere, such as the occurrence and d

  15. On the atmosphere of a moving body

    DEFF Research Database (Denmark)

    Pedersen, Johan Rønby; Aref, Hassan

    2010-01-01

    We explore whether a rigid body moving freely with no circulation around it in a two-dimensional ideal fluid can carry a fluid "atmosphere" with it in its motion. Somewhat surprisingly, the answer appears to be "yes." When the body is elongated and the motion is dominated by rotation, we...... demonstrate numerically that, indeed, regions of fluid follow the body in its motion. We see this as an example of the stability of Kolmogorov-Arnold-Moser tori. These observations of an atmosphere around a moving body with no circulation around it appear to be new. (C) 2010 American Institute of Physics...

  16. A probabilistic method of calculating circulation-induced trends

    Science.gov (United States)

    Brox Nilsen, Irene; Stagge, James Howard; Merete Tallaksen, Lena

    2015-04-01

    The water cycle in Europe has changed substantially over the past three decades. Increasing runoff is observed during winter and at northern latitudes in particular. Spring and summer months, as well as southern latitudes, are facing drier conditions. To understand what is driving large-scale changes in runoff, we look into changes in precipitation and temperature and link these to changes in atmospheric circulation. Previous studies have used the method of trend ratios (Cahynová and Huth, 2009) to attribute precipitation and temperature trends to changes in the frequency of circulation types. A trend ratio is the ratio of hypothetical trend, i.e., the trend that would result due to changes in circulation type frequency only, to the observed trend. However, the method of trend ratios has two drawbacks. First, if the observed trend is small, division by a very low value results in a meaningless trend ratio and thus requires a cut-off value to keep the trend ratio within meaningful boundaries. Second, the method does not allow a comparison of the observed trend to the spread of possible outcomes, because the method of hypothetical trends is based on a deterministic model. We propose a new, more robust method for detecting the importance of circulation-induced changes in explaining the observed trends, which has the benefit of being a non-parametric statistical test that assesses the entire range of hypothetical trends. Instead of creating a hypothetical series by replacing the observation on a given day with the long-term climatic mean of a certain month and circulation type (as in the existing trend ratio method), the new approach replaces the observation on a given day with a random sample from the distribution of the variable for the given month and circulation type. The method introduces the possibility to assign a rejection rate, thus allowing statistical significance to be assessed. We apply the method on time series of precipitation and temperature from the

  17. Minor effect of meltwater on the ocean circulation during deglaciation

    Directory of Open Access Journals (Sweden)

    G. Lohmann

    2012-08-01

    Full Text Available Decaying Northern Hemisphere ice sheets during deglaciation affect the high latitude hydrological balance in the North Atlantic and therefore the ocean circulation after the Last Glacial Maximum. Surprisingly, geological data suggest that meltwater fluxes of about 14–20 m sea-level equivalent flushed into the North Atlantic without significantly influencing the Atlantic meridional overturning circulation. Using a three-dimensional ocean circulation model coupled to an energy balance model of the atmosphere, we investigate the response of the ocean circulation to spatio-temporal variable deglacial freshwater discharges. Freshwater inputs are simulated by a three-dimensional thermo-mechanical ice sheet model of the Northern Hemisphere. In our experiments, we find a strong sensitivity of the ocean circulation when the deglacial meltwater is injected into the surface layers yielding a quasi shut-down. On the other hand, the parameterization of huge sub-glacial outbursts as so-called hyperpycnal flows are mimicked through bottom injections in ocean models leading to a reduced sensitivity of the overturning circulation against freshwater perturbations and providing a consistent representation of the deglacial climate evolution.

  18. 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.

  19. Sino-Danish Brain Circulation

    DEFF Research Database (Denmark)

    Bertelsen, Rasmus Gjedssø; Du, Xiangyun; Søndergaard, Morten Karnøe

    2014-01-01

    China is faced with urgent needs to develop an economically and environmentally sustainable economy based on innovation and knowledge. Brain circulation and research and business investments from the outside are central for this development. Sino-American brain circulation and research...... and investment by overseas researchers and entrepreneurs are well described. In that case, the US is the center of global R&D and S&T. However, the brain circulation and research and investments between a small open Scandinavian economy, such as Denmark, and the huge developing economy of China are not well...... understood. In this case, Denmark is very highly developed, but a satellite in the global R&D and S&T system. With time and the growth of China as a R&D and S&T power house, both Denmark and China will benefit from brain circulation between them. Such brain circulation is likely to play a key role in flows...

  20. 典型南涝(旱)北旱(涝)梅雨大气环流特征差异及动力诊断分析%The Difference of the Atmospheric Circulation Features and Dynamical Diagnosis about the Typical Meiyu Patterns of Southern Flood (Drought) and Northern Drought (Flood)

    Institute of Scientific and Technical Information of China (English)

    牛若芸; 苏爱芳; 马杰; 吕学东

    2011-01-01

    By using NCEP reanalysis data and composition analysis and dynamical diagnosis, this paper compares the difference of the atmospheric circulation features about the typical Meiyu patterns of southern flood (drought) and northern drought (flood), and investigate the performance of dynamic identification of nearly 20 kinds of physical quantities for the main rain belt. The results show that: for the typical Meiyu pattern of southern flood (drought) and northern drought (flood) the polar vortex is stronger (weaker), the amplitudes of roughs and ridges in the middle-high latitudes of Asia - Europe are larger (smaller), the geopotential height in the middle latitudes during 110°E- 150°E is lower obviously, the above differences indicate the power of cold air is stronger (weaker); correspondingly the east part of main body of the South Asia high is more southward (northward); the main body of the western Pacific Ocean subtropical high is more eastward (westward) and its western ridge line is more southward (northward); the Indian monsoon trough is weaker (stronger); both the upper divergence and the lower convergence over the Changjiang - Huaihe River valley caused by the upper and lower level jets are weaker (stronger); the water vapor transport flux over the Changjiang- Huaihe River valley is smaller (larger) which is mainly originated from the southwestern monsoon current (from the southwestern monsoon current and the easterly current on the south side of the western Pacific Ocean subtropical high). It is in good agreement with the main rain belt, such as the strong gradient convergence region of meridional wind on the left side of the low level jet axis, the center of vertical ascending motion at 500 hPa, the high value band of total transfiguration at 925 hPa and 300 hPa, the strong gradient convergence region of meridional vapor flux in the lower atmosphere, the convergence center of Q vector in the middle atmosphere.%利用NCEP逐日再分析资料,采用合成

  1. Atmospheric materiality

    DEFF Research Database (Denmark)

    Wieczorek, Izabela

    2016-01-01

    experience and, consequently, to the conceptual and methodological shifts in the production of space, and hence in the way we think about materiality. In this context, architectural space is understood as a contingent construction – a space of engagement that appears to us as a result of continuous...... characteristics of atmosphere as a spatial phenomenon, the aim of this text is to illustrate these associations and draw out design protocols, focusing on ways in which atmosphere can be conditioned architecturally. In other words, the objective is to trace the conceptual contours of ‘atmospheric materiality’....

  2. Current components, physical, ocean circulation, wind circulation, and other data from moored buoys, CTD casts, drifting buoys, and in situ wind recorders from AIRCRAFT and other platforms from the North Atlantic Ocean and other locations as part of the Seasonal Response of the Equatorial Atlantic Experiment/Francais Ocean Et Climat Dans L'Atlantique Equatorial (SEQUAL/FOCAL) project from 25 January 1980 to 18 December 1985 (NODC Accession 8700111)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current components, physical, ocean circulation, wind circulation, and other data were collected from moored buoys, CTD casts, drifting buoys, and in situ wind...

  3. 江淮入梅前后大气环流的演变特征和西太平洋副高北跳西伸的可能机制%THE FEATURES OF ATMOSPHERIC CIRCULATION DURING MEIYU ONSET AND POSSIBLE MEHANISMS FOR WESTWARD EXTENSION (NORTHWARD SHIFT) OF PACIFIC SUBTROPICAL HIGH

    Institute of Scientific and Technical Information of China (English)

    徐海明; 何金海; 周兵

    2001-01-01

    该文首先采用合成分析的方法研究了江淮入梅前后大尺度大气环流的演变特征和西太平洋副热带高压西伸北跳的可能机制。研究结果表明,江淮入梅前期的最显著的特征是:副热带高压首先在太平洋中部增强北跳,而后向西扩展导致太平洋副高西部脊(120°E)的增强北跳。进一步分析表明,在太平洋中部副热带高压的增强北跳和西伸之前,副热带高压南侧ITCZ中对流和孟加拉湾北部的对流活动明显并且都经历了一次增强活跃过程,这意味着热带ITCZ和孟加拉湾北部对流的异常活跃可能对副热带高压的增强北跳西伸产生影响。全球大气环流模式模拟结果表明,赤道中太平洋ITCZ中对流异常活跃不仅可导致副热带高压的增强北移,而且还可导致副热带高压西伸,与诊断分析结果相一致。%Through composite analysis, the features of the atmospheric circulation during Meiyu onset and possible mechanisms responsible for the westward extension and northward shift of the western Pacific Subtropical High are investigated. Results indicate that the most pronounced characteristics of the circulation evolution prior to the Meiyu onset are: the subtropical High intensifies first, jumps northward in the middle Pacific, and then extends westward, thus resulting in the reinforcement (northward migration) of the western part of the Pacific Subtropical High ridge at 120°E. The further study reveals that the enhancement (northward movement) and westward shift of the Subtropical High over the middle Pacific are closely related to the abnormally active convection in the ITCZ to the south and over the northern Bay of Bengal. A GCM simulation is performed to study the effects of abnormal convection over the middle equatorial Pacific on the Subtropical High and results show that the abnormal convection can result in both the enhancement (northward migration) of the Subtropical High

  4. Atmospheric Dispositifs

    DEFF Research Database (Denmark)

    Wieczorek, Izabela

    2015-01-01

    , the conceptual foundations and protocols for the production of atmosphere in architecture might be found beneath the surface of contemporary debates. In this context, the notion of atmospheric dispositif – illustrated through an oeuvre of the German architect Werner Ruhnau and its theoretical and historical...... as a spatial phenomenon, exploring a multiplicity of conditions that constitute their resonant origins – i.e. the production sites from and within they have emerged. The intention is also to argue that despite the fact that atmosphere as an aesthetic category has crystallised over the last few decades...... contextualisation – provides a platform for revealing productive entanglements between heterogeneous elements, disciplines and processes. It also allows rendering atmosphere as a site of co-production open to contingencies and affective interplay on multiples levels: at the moment of its conceptualisation...

  5. Atmospheric composition

    Science.gov (United States)

    Daniels, G. E.

    1973-01-01

    The earth's atmosphere is made up of a number of gases in different relative amounts. Near sea level and up to about 90 km, the amount of these atmospheric gases in clean, relatively dry air is practically constant. Four of these gases, nitrogen, oxygen, argon, and carbon dioxide, make up 99.99 percent by volume of the atmosphere. Two gases, ozone and water vapor, change in relative amounts, but the total amount of these two is very small compared to the amount of the other gases. The atmospheric composition shown in a table can be considered valid up to 90 km geometric altitude. Above 90 km, mainly because of molecular dissociation and diffusive separation, the composition changes.

  6. 春季黑潮延伸体海洋锋区经向位移与东亚大气环流的关系%The relationship between meridional displacement of the oceanic front in Kuroshio extension during spring and atmospheric circulation in East Asia

    Institute of Scientific and Technical Information of China (English)

    马静; 徐海明

    2012-01-01

    Index of the meridional displacement of the oceanic front in Kuroshio extension region during spring is defined based on high-resolution sea surface temperature dataset. We investigate its relations with the jet stream, storm track and later stage of rainfall in East Asia. Our analysis shows that there exist significantly mterannual and interdeeadal changes in north-south position of the oceanic front in Kuroshio extension during spring. A close relationship is found between north-south position of the oceanic front and the storm track in Pacific region, jet stream in East Asia. As the oceanic front is inclinable In the north in spring, storm track and jet stream shift northward in June accordingly, and vice versa. Further research also reveals that atmospheric circulation in East Asia can he influenced by the displacement of oceanic front,resulting in precipitation anomaly in June. In correspondence with the northerly (southerly) position of oceanic front, rain band migrates northward (southward) perceptibly.%采用高分辨率的海表温度资料定义了春季黑潮延伸体北侧海洋锋区的南北位置,并采用EOF分析、相关分析、合成分析、带通滤波等方法,探讨了其南北句位置变动与高空急流、风暴轴以及后期东亚降水之间的关系.结果表明,春季黑潮延伸体北侧海洋锋区位置的南北变动存在明显的年际、年代际变化,其与6月东亚高空急流、太平洋区域风暴轴的南北位置具有很好的对应关 系.当春季黑潮延伸体海洋锋区偏北时.6月东亚高空急流、太平洋区域风暴轴偏北,反之亦然.进一步的研究还表明,春季黑潮延伸体海洋锋区经向位置的变动可通过影响东亚大气环流对6月东亚地区的降水产生影响,黑潮延伸体海洋锋区偏北(南)年,6月雨带有显著的北(南)移.

  7. Numerical model experiments on the variation of the ocean-atmosphere carbon cycle during the last 2100 years: The impact of variations of the thermahaline oceanic circulation; Numerische Modellexperimente zur Veraenderung des Ozean-Atmosphaere-Kohlenstoffkreislaufes waehrend der letzten 21000 Jahre: Der Einfluss von Variationen der thermohalinen Ozeanzirkulation

    Energy Technology Data Exchange (ETDEWEB)

    Schulz, M.

    1998-03-01

    In order to quantify the variability of the ocean-atmosphere carbon-cycle on glacial-interglacial time scales numerical biogeochemical models are required. In this work, a modeling approach consisting of a coupling between a newly developed biogeochemical box model (16 oceanic boxes) and a three-dimensional (3D) ocean general circulation model (OGCM) was pursued. The simulation of biogeochemical processes by the box model is almost identical to state of the art 3D-models. The global OGCM (4 x 6 , 12 layers) is forced by temperature and salinity fields obtained from paleoceanographic time-slice reconstructions, and model-derived wind fields. This model setup offers several advantages: (1) The box model is driven by waterfluxes that are diagnosed from the OGCM-fields. This approach results in hydrodynamically consistent water-fluxes for the box model. (2) The OGCM results guide the selection of appropriate box-configurations for time-slices having water-mass distributions that differ from the present-day situation. (3) The high numerical efficiency of the biogeochemical model component allows for a sufficient number of sensitivity experiments. (4) Based on paleoceanographic information, the boundary conditions of the box model can be combined as a function of time in order to conduct time-dependent experiments with the box model. (orig.) [Deutsch] Die globale Quantifizierung von Veraenderungen des Ozean-Atmosphaere-Kohlenstoffkreislaufes auf glazial-interglazialen Zeitskalen erfordert den Einsatz numerischer biogeochemischer Modelle. Im Rahmen dieser Arbeit wurde hierzu ein Modellansatz gewaehlt, der aus der Kopplung eines neu entwickelten biogeochemischen Boxmodells (16 ozeanische Boxen) an ein dreidimensionales (3D) allgemeines Ozean-Zirkulationsmodell (OGCM) besteht. Die Simulation biogeochemischer Prozesse erfolgt im Boxmodell analog zu hochentwickelten 3D-Modellen. Das globale (4 x 6 , 12 Schichten) Ozeanmodell wird mit Temperatur- und Salzgehaltsfeldern, die

  8. Circulation and Dissipation on Hot Jupiters

    CERN Document Server

    Li, Jason

    2010-01-01

    Many global circulation models predict supersonic zonal winds and large vertical shears in the atmospheres of short-period jovian exoplanets. Using linear analysis and nonlinear local simulations, we investigate hydrodynamic dissipation mechanisms to balance the thermal acceleration of these winds. The adiabatic Richardson criterion remains a good guide to linear stability, although thermal diffusion allows some modes to violate it at very long wavelengths and very low growth rates. Nonlinearly, wind speeds saturate at Mach numbers $\\approx 2$ and Richardson numbers $\\lesssim 1/4$ for a broad range of plausible diffusivities and forcing strengths. Turbulence and vertical mixing, though accompanied by weak shocks, dominate the dissipation, which appears to be the outcome of a recurrent Kelvin-Helmholtz instability. An explicit shear viscosity, as well as thermal diffusivity, is added to ZEUS to capture dissipation outside of shocks. The wind speed is not monotonic nor single valued for shear viscosities larger...

  9. Atmospheric changes from solar eclipses

    CERN Document Server

    Aplin, Karen; Gray, Suzanne

    2016-01-01

    This article reviews atmospheric changes associated with 44 solar eclipses, beginning with the first quantitative results available, from 1834 (earlier qualitative, accounts also exist). Eclipse meteorology attracted relatively few publications until the total solar eclipse of 16 February 1980, with the 11 August 1999 eclipse producing the most papers. Eclipses passing over populated areas such as Europe, China and India now regularly attract scientific attention, whereas atmospheric measurements of eclipses at remote locations remain rare. Many measurements and models have been used to exploit the uniquely predictable solar forcing provided by an eclipse. In this paper we compile the available publications and review a sub-set of them chosen on the basis of importance and novelty. Beyond the obvious reduction in incoming solar radiation, atmospheric cooling from eclipses can induce dynamical changes. Observations and meteorological modelling provide evidence for the generation of a local eclipse circulation ...

  10. Climate Change and the Brewer-Dobson Circulation

    Science.gov (United States)

    Rind, David

    1999-01-01

    Using GCM (General Circulation Model) simulations of the troposphere-stratosphere circulation in different climate regimes, the sensitivity of the Brewer-Dobson Circulation to climate change will be discussed. Included will be simulations of the stratosphere with increasing/doubled CO2 as done with different versions of the GISS (Goddard Institute for Space Studies) Global Climate Middle Atmosphere Model, with and without ozone response. To put the results in a broader perspective, stratospheric circulation changes from several paleoclimate simulations will also be presented, including the Last Glacial Maximum and the Paleocene, each with several different (plausible) latitudinal sea surface temperature gradients. Hence the climate changes investigated will include strong variations in baroclinic and topographic tropospheric planetary wave and gravity wave forcing, as well as global mean temperature and atmospheric CO2 levels. Results will be analyzed in terms of wave driving via E-P flux convergences and gravity wave effects, and will be shown to be strongly dependent on wave propagation characteristics.

  11. The circulation physiology of agroecosystems

    Institute of Scientific and Technical Information of China (English)

    Cao Zhiping; Richard Dawson

    2007-01-01

    This paper represents an effort to enlarge the understanding of the biophysical foundation of agroecosystems by using an analogy with the circulation of the blood in the human body. The circulation function in the human body can be represented as arterial pressure. The factors affecting arterial pressure in the human body have direct counterparts in the cultivation-husbandry system. The relationship between circulation pressure and the factors affecting that pressure in the cultivation-husbandry system are similar to the relationship between the arterial pressure and factors affecting arterial pressure in the human body. Furthermore, circulation resistance in the cultivation-husbandry system can be shown to be analogous to the calculation of peripheral resistance in the human body by Poiseuille's formula.

  12. Ocean circulation and other data from SUBSURFACE FLOATS and other platforms from the TOGA Area - Atlantic as part of the World Ocean Circulation Experiment (WOCE) from 17 May 1991 to 09 June 1993 (NODC Accession 9600064)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Ocean circulation and other data were collected from SUBSURFACE FLOATS and other platforms from the TOGA Area - Atlantic. Data were collected by Woods Hole...

  13. Ocean circulation and other data from SUBSURFACE FLOATS from the NW Atlantic (limit-40 W) and other locations as part of the World Ocean Circulation Experiment (WOCE) from 01 January 1972 to 31 December 1989 (NODC Accession 9200081)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Ocean circulation and other data were collected from SUBSURFACE FLOATS from the NW Atlantic (limit-40 W) and other locations. Data were collected by Woods Hole...

  14. 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.

  15. Snow hydrology in a general circulation model

    Science.gov (United States)

    Marshall, Susan; Roads, John O.; Glatzmaier, Gary

    1994-01-01

    A snow hydrology has been implemented in an atmospheric general circulation model (GCM). The snow hydrology consists of parameterizations of snowfall and snow cover fraction, a prognostic calculation of snow temperature, and a model of the snow mass and hydrologic budgets. Previously, only snow albedo had been included by a specified snow line. A 3-year GCM simulation with this now more complete surface hydrology is compared to a previous GCM control run with the specified snow line, as well as with observations. In particular, the authors discuss comparisons of the atmospheric and surface hydrologic budgets and the surface energy budget for U.S. and Canadian areas. The new snow hydrology changes the annual cycle of the surface moisture and energy budgets in the model. There is a noticeable shift in the runoff maximum from winter in the control run to spring in the snow hydrology run. A substantial amount of GCM winter precipitation is now stored in the seasonal snowpack. Snow cover also acts as an important insulating layer between the atmosphere and the ground. Wintertime soil temperatures are much higher in the snow hydrology experiment than in the control experiment. Seasonal snow cover is important for dampening large fluctuations in GCM continental skin temperature during the Northern Hemisphere winter. Snow depths and snow extent show good agreement with observations over North America. The geographic distribution of maximum depths is not as well simulated by the model due, in part, to the coarse resolution of the model. The patterns of runoff are qualitatively and quantitatively similar to observed patterns of streamflow averaged over the continental United States. The seasonal cycles of precipitation and evaporation are also reasonably well simulated by the model, although their magnitudes are larger than is observed. This is due, in part, to a cold bias in this model, which results in a dry model atmosphere and enhances the hydrologic cycle everywhere.

  16. Atmospheric Photochemistry

    Science.gov (United States)

    Massey, Harrie; Potter, A. E.

    1961-01-01

    The upper atmosphere offers a vast photochemical laboratory free from solid surfaces, so all reactions take place in the gaseous phase. At 30 km altitude the pressure has fallen to about one-hundredth of that at ground level, and we shall, rather arbitrarily, regard the upper atmosphere as beginning at that height. By a little less than 100 km the pressure has fallen to 10(exp -3) mm Hg and is decreasing by a power of ten for every 15 km increase in altitude. Essentially we are concerned then with the photochemistry of a nitrogen-oxygen mixture under low-pressure conditions in which photo-ionization, as well as photodissociation, plays an important part. Account must also be taken of the presence of rare constituents, such as water vapour and its decomposition products, including particularly hydroxyl, oxides of carbon, methane and, strangely enough, sodium, lithium and calcium. Many curious and unfamiliar reactions occur in the upper atmosphere. Some of them are luminescent, causing the atmosphere to emit a dim light called the airglow. Others, between gaseous ions and neutral molecules, are almost a complete mystery at this time. Similar interesting phenomena must occur in other planetary atmospheres, and they might be predicted if sufficient chemical information were available.

  17. The relationship between the thermohaline circulation and climate variability

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The long-term integration with the Global Ocean-Atmosphere-Land System model of the State Key Laboratory of Atmospheric Sciences and Geophysical Fluid Dynamics (LASG), Institute of Atmospheric Physics(IAP), Chinese Academy of Sciences has been used in the investigations on the relationship between the thermohaline circulation and climate variability. The results show that the strength of the North Atlantic Thermohaline circulation (THC) is negatively correlated with the North Atlantic Oscillation (NAO). Based on this kind of relationship, and also the instrument-measured climate record such as air pressure and sea surface temperature, the activity of the thermohaline circulation during the 20th century has been evaluated. The inferred variations of the strength of the THC is that, during two multi-decadal periods of 1867-1903 and 1934-1972, the THC is estimated to have been running stronger, whereas during the two periods of 1904-1933 and 1973-1994, it appears to have been weaker.

  18. Tropospheric circulation during the early twentieth century Arctic warming

    Science.gov (United States)

    Wegmann, Martin; Brönnimann, Stefan; Compo, Gilbert P.

    2016-06-01

    The early twentieth century Arctic warming (ETCAW) between 1920 and 1940 is an exceptional feature of climate variability in the last century. Its warming rate was only recently matched by recent warming in the region. Unlike recent warming largely attributable to anthropogenic radiative forcing, atmospheric warming during the ETCAW was strongest in the mid-troposphere and is believed to be triggered by an exceptional case of natural climate variability. Nevertheless, ultimate mechanisms and causes for the ETCAW are still under discussion. Here we use state of the art multi-member global circulation models, reanalysis and reconstruction datasets to investigate the internal atmospheric dynamics of the ETCAW. We investigate the role of boreal winter mid-tropospheric heat transport and circulation in providing the energy for the large scale warming. Analyzing sensible heat flux components and regional differences, climate models are not able to reproduce the heat flux evolution found in reanalysis and reconstruction datasets. These datasets show an increase of stationary eddy heat flux and a decrease of transient eddy heat flux during the ETCAW. Moreover, tropospheric circulation analysis reveals the important role of both the Atlantic and the Pacific sectors in the convergence of southerly air masses into the Arctic during the warming event. Subsequently, it is suggested that the internal dynamics of the atmosphere played a major role in the formation in the ETCAW.

  19. Mudanças na circulação atmosférica sobre a América do Sul para cenários futuros de clima projetados pelos modelos globais do IPCC AR4 Changes in the atmospheric circulation pattern over South America in future climate scenarios derived from the IPCC AR4 model climate simulations

    Directory of Open Access Journals (Sweden)

    María C Valverde

    2010-03-01

    Full Text Available Neste trabalho são analisadas as mudanças no padrão de circulação que possam vir a acontecer no clima da América do Sul (AS, como conseqüência do aumento nas concentrações dos gases de efeito estufa. Para isto utilizam-se cinco modelos globais do IPCC AR4 (CCCMA, GFDL, HadCM3, MIROC e GISS, para o clima do século XX (1961-1990 - 20C3M e para o cenário futuro SRES_A2 (2011-2100. As características em comum que os modelos apresentaram (a exceção do MIROC para as três climatologias futuras (2011-2040, 2041-2070 e 2071-2100, principalmente, no verão e na primavera, foram o deslocamento da baixa continental (associada à baixa do Chaco para o sudoeste da sua posição climatológica (1961-1990, e da Alta da Bolívia para o noroeste. Além disso, os cinco modelos simularam, para o clima presente, uma Alta do Pacífico Sul (APS menos intensa em relação à Reanálise do NCEP, sugerindo menor subsidência sobre a sua região de atuação. Para cenários futuros os modelos GISS e HadCM3 simularam a APS menos intensa. Por outro lado, para a alta do Atlântico Sul, não existiu um consenso nos modelos. Em geral foi simulada mais intensa (a exceção do GISS, sobretudo no outono e no inverno. O modelo HadCM3 simulou a circulação de verão e primavera mais próxima à Reanálise, com uma ZCAS melhor definida, e uma área menor de anomalias negativas de chuva sobre a Amazônia, em relação aos outros modelos. Já para o cenário futuro este modelo modificou seu padrão de chuvas, e anomalias positivas, sobre a costa norte do Peru e Equador, e negativas sobre o Nordeste e leste da Amazônia, foram observadas, associadas a uma APS enfraquecida e deslocada para o sul, o que reforçou a ZCIT do Pacífico sobre 5ºS. Uma diminuição da convergência de umidade sobre a Amazônia também foi observada.In this paper changes in the atmospheric circulation that may occur in the South America (SA as a consequence of climate change were studied for

  20. Atmospheric changes from solar eclipses.

    Science.gov (United States)

    Aplin, K L; Scott, C J; Gray, S L

    2016-09-28

    This article reviews atmospheric changes associated with 44 solar eclipses, beginning with the first quantitative results available, from 1834 (earlier qualitative accounts also exist). Eclipse meteorology attracted relatively few publications until the total solar eclipse of 16 February 1980, with the 11 August 1999 eclipse producing the most papers. Eclipses passing over populated areas such as Europe, China and India now regularly attract scientific attention, whereas atmospheric measurements of eclipses at remote locations remain rare. Many measurements and models have been used to exploit the uniquely predictable solar forcing provided by an eclipse. In this paper, we compile the available publications and review a subset of them chosen on the basis of importance and novelty. Beyond the obvious reduction in incoming solar radiation, atmospheric cooling from eclipses can induce dynamical changes. Observations and meteorological modelling provide evidence for the generation of a local eclipse circulation that may be the origin of the 'eclipse wind'. Gravity waves set up by the eclipse can, in principle, be detected as atmospheric pressure fluctuations, though theoretical predictions are limited, and many of the data are inconclusive. Eclipse events providing important early insights into the ionization of the upper atmosphere are also briefly reviewed.This article is part of the themed issue 'Atmospheric effects of solar eclipses stimulated by the 2015 UK eclipse'.

  1. Atmospheric thermodynamics

    CERN Document Server

    Iribarne, J V

    1973-01-01

    The thermodynamics of the atmosphere is the subject of several chapters in most textbooks on dynamic meteorology, but there is no work in English to give the subject a specific and more extensive treatment. In writing the present textbook, we have tried to fill this rather remarkable gap in the literature related to atmospheric sciences. Our aim has been to provide students of meteorology with a book that can playa role similar to the textbooks on chemical thermodynamics for the chemists. This implies a previous knowledge of general thermodynamics, such as students acquire in general physics courses; therefore, although the basic principles are reviewed (in the first four chapters), they are only briefly discussed, and emphasis is laid on those topics that will be useful in later chapters, through their application to atmospheric problems. No attempt has been made to introduce the thermodynamics of irreversible processes; on the other hand, consideration of heterogeneous and open homogeneous systems permits a...

  2. Composite circulation index of weather extremes (the example for Poland

    Directory of Open Access Journals (Sweden)

    Zbigniew Ustrnul

    2013-10-01

    Full Text Available The paper describes the implementation of a composite circulation index of weather extremes (CIE. The new index informs about the synoptic conditions favoring the occurrence of extremes on a regional scale. It was evaluated for temperature and precipitation extremes for Poland. Daily homogenized data obtained from 14 weather stations, which cover most of the country, were used. The data used cover the 60-year period from 1951 to 2010. The index is based on relationships between extremes and mesoscale circulation conditions. The core material also included data describing circulation types for the study period. Three different calendars were used (Grosswetterlagen, by Lity?ski, by Nied?wied?. The conditional probability of the occurrence of extremes for particular types was calculated independently using partial indices (Partial Index of weather Extremes ? PIE. The higher the index values, the more favorable the synoptic situation for the occurrence of extremes. The results were grouped by describing the probability of temperature and precipitation extremes on the IPCC likelihood scale. Three thresholds corresponding to the frequency of an occurrence were identified via a seasonal approach. The CIE was validated using basic correlation coefficients as well as contingency tables based on feature-displacement criteria and Bayesian Probability Methods. The results confirmed the significance of atmospheric circulation in the formation of temperature and precipitation extremes in Poland. The CIE proved the relationship by trying to estimate the probability of temperature and precipitation extremes occurrence depending on the circulation type forecasted.

  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. Changes in tropical circulation in a warming climate

    Science.gov (United States)

    Chou, C.

    2013-12-01

    Precipitation is experiencing a great change under global warming. Two major processes induced changes in precipitation are thermodynamic and dynamic contributions. The former is related to changes in water vapor and the latter is associated with changes in vertical velocity. Since water vapor increases almost everywhere, the thermodynamic contribution is determined by the corresponding mean vertical motion: positive for ascents and negative for descents, which creates a 'wet-get-wetter and dry-get-drier' tendency. The dynamic contribution, on the other hand, is much more complicated, especially on a regional basis. For a global average, all climate models in the CMIP3 and CMIP5 show a robust weakening of tropical circulation, while observed changes in tropical circulation are inconsistent among data sets. A fundamental explanation for changes in tropical circulation is related to atmospheric stability. In a warmer climate, the upper troposphere warms up faster than the lower troposphere, so dry static stability increases. Thus, the atmosphere should become more stable and the corresponding tropical circulation weakens. However, a more physically-sound index, moist static stability, shows very scattering changes in global-warming simulations. In other words, the atmosphere can become either more stable or more unstable if considering the effect of water vapor. Here we introduce a new effect associated with convection depth by proposing another index, gross moist stability, to measure changes in atmospheric stability under global warming. The gross moist stability, an effective static stability, is vertical integral of the vertical gradient of moist static energy weighted by pressure velocity. It depends not only on the vertical gradient of dry static energy, which is equivalent to dry static stability, but also on moisture vertical distribution and convection depth. The effects of dry static energy and convection depth stabilize the atmosphere, while the moisture

  5. Atmospheric Refraction

    CERN Document Server

    Nauenberg, Michael

    2016-01-01

    Calculations of atmospheric refraction are generally based on a simplified model of atmospheric density in the troposphere which assumes that the temperature decreases at a constant lapse rate from sea level up to a height equal to eleven km, and that afterwards it remains constant. In this model, the temperature divided by the lapse rate determines the length scale in the calculations for altitudes less than this height. But daily balloon measurements across the U.S.A. reveal that in some cases the air temperature actually increases from sea level up to a height of about one km, and only after reaching a plateau, it decreases at an approximately constant lapse rate. Moreover, in three examples considered here, the temperature does not remain constant at eleven km , but continues to decreases to a minimum at about sixteen kilometers , and then increases at higher altitudes at a lower rate. Calculations of atmospheric refraction based on this atmospheric data is compared with the results of simplified models.

  6. The Invertibility, Explicit Determinants, and Inverses of Circulant and Left Circulant and g-Circulant Matrices Involving Any Continuous Fibonacci and Lucas Numbers

    Directory of Open Access Journals (Sweden)

    Zhaolin Jiang

    2014-01-01

    Full Text Available Circulant matrices play an important role in solving delay differential equations. In this paper, circulant type matrices including the circulant and left circulant and g-circulant matrices with any continuous Fibonacci and Lucas numbers are considered. Firstly, the invertibility of the circulant matrix is discussed and the explicit determinant and the inverse matrices by constructing the transformation matrices are presented. Furthermore, the invertibility of the left circulant and g-circulant matrices is also studied. We obtain the explicit determinants and the inverse matrices of the left circulant and g-circulant matrices by utilizing the relationship between left circulant, g-circulant matrices and circulant matrix, respectively.

  7. Atmospheric dynamics of terrestrial exoplanets over a wide range of orbital and atmospheric parameters

    CERN Document Server

    Kaspi, Yohai

    2014-01-01

    The recent discoveries of terrestrial exoplanets and super Earths extending over a broad range of orbital and physical parameters suggests 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, pattern of relative humidity, and other aspects of the dynamics. Here, using an idealized moist atmospheric general circulation model (GCM) including a hydrological cycle, we study the dynamical principles governing the atmospheric dynamics on such planets. We show how the planetary rotation rate, planetary mass,...

  8. Circulating Fibronectin Controls Tumor Growth

    Directory of Open Access Journals (Sweden)

    Anja von Au

    2013-08-01

    Full Text Available Fibronectin is ubiquitously expressed in the extracellular matrix, and experimental evidence has shown that it modulates blood vessel formation. The relative contribution of local and circulating fibronectin to blood vessel formation in vivo remains unknown despite evidence for unexpected roles of circulating fibronectin in various diseases. Using transgenic mouse models, we established that circulating fibronectin facilitates the growth of bone metastases by enhancing blood vessel formation and maturation. This effect is more relevant than that of fibronectin produced by endothelial cells and pericytes, which only exert a small additive effect on vessel maturation. Circulating fibronectin enhances its local production in tumors through a positive feedback loop and increases the amount of vascular endothelial growth factor (VEGF retained in the matrix. Both fibronectin and VEGF then cooperate to stimulate blood vessel formation. Fibronectin content in the tumor correlates with the number of blood vessels and tumor growth in the mouse models. Consistent with these results, examination of three separate arrays from patients with breast and prostate cancers revealed that a high staining intensity for fibronectin in tumors is associated with increased mortality. These results establish that circulating fibronectin modulates blood vessel formation and tumor growth by modifying the amount of and the response to VEGF. Furthermore, determination of the fibronectin content can serve as a prognostic biomarker for breast and prostate cancers and possibly other cancers.

  9. Atmospheric dynamics of Earth-like tidally locked aquaplanets

    CERN Document Server

    Merlis, Timothy M

    2010-01-01

    We present simulations of atmospheres of Earth-like aquaplanets that are tidally locked to their star, that is, planets whose orbital period is equal to the rotation period about their spin axis, so that one side always faces the star and the other side is always dark. As extreme cases illustrating the effects of slow and rapid rotation, we consider planets with rotation periods equal to one current Earth year and one current Earth day. The dynamics responsible for the surface climate (e.g., winds, temperature, precipitation) and the general circulation of the atmosphere are discussed in light of existing theories of atmospheric circulations. For example, as expected from the increasing importance of Coriolis accelerations relative to inertial accelerations as the rotation rate increases, the winds are approximately isotropic and divergent at leading order in the slowly rotating atmosphere but are predominantly zonal and rotational in the rapidly rotating atmosphere. Free-atmospheric horizontal temperature va...

  10. Ohmic Dissipation in the Atmospheres of Hot Jupiters

    CERN Document Server

    Perna, Rosalba; Rauscher, Emily

    2010-01-01

    Hot Jupiter atmospheres exhibit fast, weakly-ionized winds. The interaction of these winds with the planetary magnetic field generates drag on the winds and leads to ohmic dissipation of the induced electric currents. We study the magnitude of ohmic dissipation in representative, three-dimensional atmospheric circulation models of the hot Jupiter HD 209458b. We find that ohmic dissipation can reach or exceed 1% of the stellar insolation power in the deepest atmospheric layers, in models with and without dragged winds. Such power, dissipated in the deep atmosphere, appears sufficient to slow down planetary contraction and explain the typically inflated radii of hot Jupiters. This atmospheric scenario does not require a top insulating layer or radial currents that penetrate deep in the planetary interior. Circulation in the deepest atmospheric layers may actually be driven by spatially non-uniform ohmic dissipation. A consistent treatment of magnetic drag and ohmic dissipation is required to further elucidate t...

  11. Circulation in blast driven instabilities

    Science.gov (United States)

    Henry de Frahan, Marc; Johnsen, Eric

    2016-11-01

    Mixing in many natural phenomena (e.g. supernova collapse) and engineering applications (e.g. inertial confinement fusion) is often initiated through hydrodynamic instabilities. Explosions in these systems give rise to blast waves which can interact with perturbations at interfaces between different fluids. Blast waves are formed by a shock followed by a rarefaction. This wave profile leads to complex time histories of interface acceleration. In addition to the instabilities induced by the acceleration field, the rarefaction from the blast wave decompresses the material at the interface, further increasing the perturbation growth. After the passage of the wave, circulation circulation generated by the blast wave through baroclinic vorticity continues to act upon the interface. In this talk, we provide scaling laws for the circulation and amplitude growth induced by the blast wave. Numerical simulations of the multifluid Euler equations solved using a high-order accurate Discontinuous Galerkin method are used to validate the theoretical results.

  12. Meteorologically-driven circulation and flushing times of the Bay of Algeciras, Strait of Gibraltar.

    Science.gov (United States)

    Sánchez-Garrido, José C; Lafuente, Jesús García; Sammartino, Simone; Naranjo, Cristina; de los Santos, Francisco J; Álvarez Fanjul, Enrique

    2014-03-15

    A primitive-equation model has been used to investigate the meteorologically-driven circulation of the Bay of Algeciras. It is shown that the mean circulation of Atlantic Water (AW) is characterized by an anticyclonic cell, while Mediterranean Water (MW) follows a preferred cyclonic pathway. Meteorological forcing distorts substantially the AW mean circulation pattern, and only modulates that of the MW. Winds drive a vertical circulation cell in the Atlantic layer consistent with Ekman dynamics, whereas the horizontal circulation pattern is markedly dependent on the swift Atlantic jet entering the Mediterranean and changes from clearly anticyclonic to cyclonic as the jet separates or approaches the strait's northern shoreline. This occurs through atmospheric pressure-driven acceleration/deceleration of the jet, in agreement with internal hydraulics theory predictions. It is also found that the renewal of AW is largely modulated by tides, with meteorological forcing playing a secondary role. The opposite applies to the renewal of MW.

  13. Atmospheric Neutrinos

    CERN Document Server

    Gaisser, Thomas K

    2016-01-01

    In view of the observation by IceCube of high-energy astrophysical neutrinos, it is important to quantify the uncertainty in the background of atmospheric neutrinos. There are two sources of uncertainty, the imperfect knowledge of the spectrum and composition of the primary cosmic rays that produce the neutrinos and the limited understanding of hadron production, including charm, at high energy. This paper is an overview of both aspects.

  14. Meridional overturning circulation: stability and ocean feedbacks in a box model

    CERN Document Server

    Cimatoribus, Andrea A; Dijkstra, Henk A

    2012-01-01

    A box model of the inter-hemispheric Atlantic meridional overturning circulation is developed, including a variable pycnocline depth for the tropical and subtropical regions. The circulation is forced by winds over a periodic channel in the south and by freshwater forcing at the surface. The model is aimed at investigating the ocean feedbacks related to perturbations in freshwater forcing from the atmosphere, and to changes in freshwater transport in the ocean. These feedbacks are closely connected with the stability properties of the meridional overturning circulation, in particular in response to freshwater perturbations.

  15. The global ocean circulation on a retrograde rotating earth

    Directory of Open Access Journals (Sweden)

    V. Kamphuis

    2010-11-01

    Full Text Available To understand the three-dimensional ocean circulation patterns that have occurred in past continental geometries, it is crucial to study the role of the present-day continental geometry and surface (wind stress and buoyancy forcing on the present-day global ocean circulation. This circulation, often referred to as the Conveyor state, is characterized by an Atlantic Meridional Overturning Circulation (MOC with deep water formation at northern latitudes and the absence of such deep water formation in the North Pacific. This MOC asymmetry is often attributed to the difference in surface freshwater flux: the North Atlantic is a basin with net evaporation, while the North Pacific receives net precipitation. This issue is revisited in this paper by considering the global ocean circulation on a retrograde rotating earth, computing an equilibrium state of the coupled atmosphere-ocean-land surface-sea ice model CCSM3. The Atlantic-Pacific asymmetry in surface freshwater flux is indeed reversed but the ocean circulation pattern is not an Inverse Conveyor state (with deep water formation in the North Pacific as there is strong and highly variable deep water formation in the North Atlantic. Using a fully-implicit, global ocean-only model also the stability properties of the Atlantic MOC on a retrograde rotating earth are investigated, showing a similar regime of multiple equilibria as in the present-day case. These results demonstrate that the present-day asymmetry in surface freshwater flux is not a crucial factor for the Atlantic-Pacific asymmetry in the global MOC.

  16. A sustained oscillation in a toy-model of the coupled atmosphere-ocean system

    CERN Document Server

    Bothe, Oliver

    2011-01-01

    Interaction between atmospheric mid-latitude flow and wind-driven ocean circulation is studied coupling two idealized low-order spectral models. The barotropic Charney-DeVore model with three components simulates a bimodal mid-latitude atmospheric circulation in a channel with two stable flow patterns induced by topography. The wind-driven ocean double gyre circulation in a square basin (of half the channel length) is modeled by an equivalent barotropic formulation of the Veronis model with 21 components, which captures Rossby-wave dynamics and nonlinear decadal variability. When coupled, the atmosphere forces the ocean by wind-stress while, simultaneously, the ocean affects the atmosphere by thermal forcing in terms of a vorticity source. Coupled atmosphere-ocean simulations show two stable flow patterns associated with the topographically induced atmospheric bimodality and a sustained oscillation due to interaction between atmospheric bimodality and oceanic Rossby dynamics. The oscillation is of inter-annua...

  17. Venusian Polar Vortex reproduced by a general circulation model

    Science.gov (United States)

    Ando, Hiroki; Sugimoto, Norihiko; Takagi, Masahiro

    2016-10-01

    Unlike the polar vortices observed in the Earth, Mars and Titan atmospheres, the observed Venus polar vortex is warmer than the mid-latitudes at cloud-top levels (~65 km). This warm polar vortex is zonally surrounded by a cold latitude band located at ~60 degree latitude, which is a unique feature called 'cold collar' in the Venus atmosphere [e.g. Taylor et al. 1980; Piccioni et al. 2007]. Although these structures have been observed in numerous previous observations, the formation mechanism is still unknown. In addition, an axi-asymmetric feature is always seen in the warm polar vortex. It changes temporally and sometimes shows a hot polar dipole or S-shaped structure as shown by a lot of infrared measurements [e.g. Garate-Lopez et al. 2013; 2015]. However, its vertical structure has not been investigated. To solve these problems, we performed a numerical simulation of the Venus atmospheric circulation using a general circulation model named AFES for Venus [Sugimoto et al. 2014] and reproduced these puzzling features.And then, the reproduced structures of the atmosphere and the axi-asymmetirc feature are compared with some previous observational results.In addition, the quasi-periodical zonal-mean zonal wind fluctuation is also seen in the Venus polar vortex reproduced in our model. This might be able to explain some observational results [e.g. Luz et al. 2007] and implies that the polar vacillation might also occur in the Venus atmosphere, which is silimar to the Earth's polar atmosphere. We will also show some initial results about this point in this presentation.

  18. VanderLaan Circulant Type Matrices

    Directory of Open Access Journals (Sweden)

    Hongyan Pan

    2015-01-01

    Full Text Available Circulant matrices have become a satisfactory tools in control methods for modern complex systems. In the paper, VanderLaan circulant type matrices are presented, which include VanderLaan circulant, left circulant, and g-circulant matrices. The nonsingularity of these special matrices is discussed by the surprising properties of VanderLaan numbers. The exact determinants of VanderLaan circulant type matrices are given by structuring transformation matrices, determinants of well-known tridiagonal matrices, and tridiagonal-like matrices. The explicit inverse matrices of these special matrices are obtained by structuring transformation matrices, inverses of known tridiagonal matrices, and quasi-tridiagonal matrices. Three kinds of norms and lower bound for the spread of VanderLaan circulant and left circulant matrix are given separately. And we gain the spectral norm of VanderLaan g-circulant matrix.

  19. Conservation of Circulation in Magnetohydrodynamics

    CERN Document Server

    Bekenstein, J D; Bekenstein, Jacob D.; Oron, Asaf

    2000-01-01

    We demonstrate, both at the Newtonian and (general) relativistic levels, theexistence of a generalization of Kelvin's circulation theorem (for pure fluids)which is applicable to perfect magnetohydrodynamics. The argument is based onthe least action principle for magnetohydrodynamic flow. Examples of the newconservation law are furnished. The new theorem should be helpful inidentifying new kinds of vortex phenomena distinct from magnetic ropes or fluidvortices.

  20. Seasonal changes in Titan's middle-atmosphere chemistry and dynamics

    Science.gov (United States)

    Teanby, N. A.; Irwin, P. G. J.; Nixon, C. A.; de Kok, R.; Vinatier, S.; Coustenis, A.; Sefton-Nash, E.; Calcutt, S. B.; Flasar, F. M.

    2013-09-01

    Titan is the largest satellite of Saturn and is the only moon in our solar system with a significant atmo- sphere. Titan's middle-atmosphere (stratosphere and mesosphere) circulation usually comprises a single hemisphere to hemisphere meridional circulation cell, with upwelling air in the summer hemisphere and sub- siding air at the winter pole with an associated winter polar vortex. Titan has an axial tilt (obliquity) of 26.7°, so during its 29.5 Earth year annual cycle pronounced seasonal effects are encountered as the relative solar insolation in each hemisphere changes. The most dramatic of these changes is the reversal in global meridional circulation as the peak solar heating switches hemispheres after an equinox. Titan's northern spring equinox occurred in August 2009, and since then many middle-atmosphere changes have been observed by Cassini that were previously impossible to study (1,2,3,4). Here we present a detailed analysis of the post equinox changes in middle-atmosphere temperature and composition measured with Cassini's Composite InfraRed Spectrometer (CIRS), use these to infer changes in atmospheric circulation, and explore implications for atmospheric photochemical and dynamical processes. Our results show that the meridional circulation has now reversed (1).

  1. Optimal Backward Perturbation Analysis for the Block Skew Circulant Linear Systems with Skew Circulant Blocks

    Directory of Open Access Journals (Sweden)

    Zhaolin Jiang

    2014-01-01

    Full Text Available We first give the block style spectral decomposition of arbitrary block skew circulant matrix with skew circulant blocks. Secondly, we obtain the singular value of block skew circulant matrix with skew circulant blocks as well. Finally, based on the block style spectral decomposition, we deal with the optimal backward perturbation analysis for the block skew circulant linear system with skew circulant blocks.

  2. Alarming atmospheres

    DEFF Research Database (Denmark)

    Højlund, Marie; Kinch, Sofie

    2014-01-01

    . As a response to this situation, our design artefact, the interactive furniture Kidkit, invites children to become accustomed to the alarming sounds sampled from the ward while they are waiting in the waiting room. Our design acknowledges how atmospheres emerge as temporal negotiations between the rhythms......, a familiar relationship with the alarming sounds in the ward, enabling her to focus later more on the visit with the relative. The article discusses the proposed design strategy behind this solution and the potentiality for its use in hospital environments in general....

  3. Balanced and Transient Dynamics of Deep and Shallow Hadley Circulations

    Science.gov (United States)

    Gonzalez, A. O.; Mora Rojas, G.; Taft, R.; Schubert, W. H.

    2014-12-01

    We examine the balanced and transient dynamics of large-scale overturning circulations in the tropical atmosphere using idealized equatorial β-plane models. When deep diabatic heating in the Intertropical Convergence Zone (ITCZ) is prescribed as slowly varying with time, the deep Hadley circulation is of first order importance. In the absence of deep diabatic heating, the interior circulation associated with Ekman pumping cannot penetrate deep into the troposphere because the resistance of fluid parcels to horizontal motion (i.e., inertial stability) is significantly smaller than their resistance to vertical motion (i.e., static stability). In this scenario, only a shallow Hadley circulation exists. The meridional asymmetry between the winter and summer deep and shallow Hadley cells is attributed to the anisotropy of the inertial stability parameter, and as the ITCZ widens meridionally or as the forcing involves higher vertical wavenumbers, the asymmetry between the winter and summer cells increases. When we prescribe both a slow and fast "switch-on" deep diabatic heating, we learn that inertia-gravity waves propagate in the meridional direction away from the ITCZ and bounce back at critical latitutes in the zonally symmetric framework. When the assumption of zonal symmetry is relaxed, we find that inertia-gravity waves propagate away from the ITCZ in not only the meridional direction but also in the zonal direction.

  4. Advances in Researches on the Middle and Upper Atmosphere in 2010-2012

    Institute of Scientific and Technical Information of China (English)

    CHEN Zeyu; CHEN Hongbin; LIU Xiao; HU Xiong; BIAN Jianchu; CHEN Wen; ZHANG Shaodong; XUE Xianghui

    2012-01-01

    This article summarizes the researches on the middle and upper atmosphere by Chinese scientists in 2010--2012. The focuses are placed on the advances in construction of ground-based remote sensing facilities, the mean state and long-term changes in the middle atmosphere circulation, the prevailing dynamical processes, and the coupling of the middle atmospheric layers.

  5. Interannual variability of South American monsoon circulation

    Science.gov (United States)

    Alonso Gan, Manoel; Rafaele Araújo Lima, Jeane

    2016-04-01

    The South America Monsoon System (SAMS) is responsible for influencing the atmospheric circulation and precipitation over most of tropical South America (SA) during the summer season. Studies for aiming to understand the temporal variability of this system have great value to the scientific community, because the processes that control the monsoon climate are not totally clear. Thus, the main objective of this research is to investigate the possible large-scale climatic factors and the remote interaction mechanisms, which may be associated with summer season interannual variability focusing on identifying the main differences between dry and wet extremes rainy season in the South-eastern Amazon Basin (SAB), Central-West (WC) and Southeast (SE) of Brazil, which are areas influenced by the summer monsoon regime. For such analyzes, Pearson correlations, quantile method and composite analysis were used during the period from 1979 to 2014. The correlation between precipitation anomaly in SAB and the sea surface temperature anomaly (SSTA) and wind at 850hPa and 300hPa indicate El Niño-Southern Oscillation (ENSO) influence. Precipitation anomalies in WC did not show significant correlation with SSTA. However, a pattern similar to ENSO Modoki type was observed in the composite analysis. At 850 hPa, the presence of an anomalous cyclonic (anticyclonic) circulation was observed over the central region of SA during wet (dry) summers seasons. Over SE region of Brazil, a dipole SSTA pattern over the South Atlantic was identified, as well the presence of anomalous circulations with an equivalent barotropic structure over these SSTA areas. This pattern is more evident in case of dry summer on the SE. At 300 hPa, the wave train between 30°S-60°S was observed presenting a feature curvature from 120°W reaching SA, similar to the Pacific-South American pattern (PSA). Analysis of the summer interannual variability indicated the manifestation of wet summers more frequently than dry

  6. Wind-driven Circulation and Freshwater Fluxes off Sri Lanka: 4D-Sampling with Autonomous Gliders

    Science.gov (United States)

    2015-09-30

    Wind-driven circulation and freshwater fluxes...riverine freshwater input, precipitation and atmospheric forcing act to govern Bay of Bengal upper ocean variability, water mass formation and...and mixing in the southern Bay of Bengal. 2. Understand how freshwater inflow, atmospheric forcing and the underlying mesoscale variability act to

  7. Synoptic-scale circulation patterns during summer derived from tree rings in mid-latitude Asia

    Science.gov (United States)

    Seim, Andrea; Schultz, Johannes A.; Leland, Caroline; Davi, Nicole; Byambasuren, Oyunsanaa; Liang, Eryuan; Wang, Xiaochun; Beck, Christoph; Linderholm, Hans W.; Pederson, Neil

    2016-11-01

    Understanding past and recent climate and atmospheric circulation variability is vital for regions that are affected by climate extremes. In mid-latitude Asia, however, the synoptic climatology is complex and not yet fully understood. The aim of this study was to investigate dominant synoptic-scale circulation patterns during the summer season using a multi-species tree-ring width (TRW) network comprising 78 sites from mid-latitude Asia. For each TRW chronology, we calculated an atmospheric circulation tree-ring index (ACTI), based on 1000 hPa geopotential height data, to directly link tree growth to 13 summertime weather types and their associated local climate conditions for the period 1871-1993. Using the ACTI, three groups of similarly responding tree-ring sites can be associated with distinct large-scale atmospheric circulation patterns: 1. growth of drought sensitive trees is positively affected by a cyclone over northern Russia; 2. temperature sensitive trees show positive associations to a cyclone over northwestern Russia and an anticyclone over Mongolia; 3. trees at two high elevation sites show positive relations to a zonal cyclone extending from mid-latitude Eurasia to the West Pacific. The identified synoptic-scale circulation patterns showed spatiotemporal variability in their intensity and position, causing temporally varying climate conditions in mid-latitude Asia. Our results highlight that for regions with less pronounced atmospheric action centers during summer such as the occurrence of large-scale cyclones and anticyclones, synoptic-scale circulation patterns can be extracted and linked to the Northern Hemisphere circulation system. Thus, we provide a new and solid envelope for climate studies covering the past to the future.

  8. Mechanisms affecting the composition of Hot Jupiters atmospheres

    Directory of Open Access Journals (Sweden)

    Showman Adam P.

    2013-04-01

    Full Text Available Opacities and thus local chemical composition play a key role when characterizing exoplanet atmospheres from observations. When the gas is in chemical equilibrium the chemical abundances depend strongly on the temperature profile. Grey models tend to overestimate the temperatures in the upper atmosphere. We present a new analytical model with a more realistic description of the radiative cooling in the infrared. Mechanisms like quenching and cold traps can drive the upper atmosphere far from its chemical equilibrium. The efficiency of these mechanisms depends on the strength of the vertical mixing. Using 3D global circulation models of HD209458b including passive tracers, we show that, although Hot Jupiter atmospheres are stably stratified, they are strongly mixed by planetary scale circulation patterns. We provide a rough estimate of the effective vertical mixing coefficient in Hot Jupiter atmosphere which can be used in 1D models.

  9. Titan's Atmospheric Dynamics and Meteorology

    Science.gov (United States)

    Flasar, F. M.; Baines, K. H.; Bird, M. K.; Tokano, T.; West, R. A.

    2008-01-01

    Titan, after Venus, is the second example of an atmosphere with a global cyclostrophic circulation in the solar system, but a circulation that has a strong seasonal modulation in the middle atmosphere. Direct measurement of Titan's winds, particularly observations tracking the Huygens probe at 10degS, indicate that the zonal winds are generally in the sense of the satellites rotation. They become cyclostrophic approx. 35 km above the surface and generally increase with altitude, with the exception of a sharp minimum centered near 75 km, where the wind velocity decreases to nearly zero. Zonal winds derived from the temperature field retrieved from Cassini measurements, using the thermal wind equation, indicate a strong winter circumpolar vortex, with maximum winds at mid northern latitudes of 190 ms-' near 300 km. Above this level, the vortex decays. Curiously, the zonal winds and temperatures are symmetric about a pole that is offset from the surface pole by approx.4 degrees. The cause of this is not well understood, but it may reflect the response of a cyclostrophic circulation to the offset between the equator, where the distance to the rotation axis is greatest, and the solar equator. The mean meridional circulation can be inferred from the temperature field and the meridional distribution of organic molecules and condensates and hazes. Both the warm temperatures in the north polar region near 400 km and the enhanced concentration of several organic molecules suggests subsidence there during winter and early spring. Stratospheric condensates are localized at high northern latitudes, with a sharp cut-off near 50degN. Titan's winter polar vortex appears to share many of the same characteristics of winter vortices on Earth-the ozone holes. Global mapping of temperatures, winds, and composition in he troposphere, by contrast, is incomplete. The few suitable discrete clouds that have bee found for tracking indicate smaller velocities than aloft, consistent with the

  10. Titan's post-equinox circulation revealed using chemical tracers

    Science.gov (United States)

    Teanby, N. A.; Irwin, P. G. J.; Nixon, C. A.; de Kok, R.; Vinatier, S.; Coustenis, A.; Calcutt, S. B.

    2012-04-01

    Titan’s atmosphere harbors a vast array of minor chemical compounds produced by its active photochemical cycle - including many hydrocarbon and nitrile species. These species have a wide range of lifetimes and can be used as chemical tracers of atmospheric motion on a variety of time scales (Teanby et al 2008). Therefore, by measuring how the abundances of these species vary during Cassini’s mission so far, it is possible to probe changes in Titan’s general circulation. Here we use eight years of Cassini Composite InfraRed Spectrometer (CIRS) data to study how the atmospheric circulation behaves during the equinox and post-equinox periods. As northern winter progressed to northern spring, significant changes in the distribution of trace gases were observed. These include an increase in trace gas abundance at the north pole and northward migration of the vortex boundary. The implications of the observed changed will be discussed - including a possible interpretation of the recent changes as a weakening of the north polar vortex accompanied by a reduction in cross-vortex mixing. References: Teanby, N. A., et al. (2008) "Titan's winter polar vortex structure revealed by chemical tracers". JGR-Planets, Vol. 113, E12003. Figure showing the observed variations in temperature and composition from the mission so far.

  11. Physiology of the fetal circulation.

    Science.gov (United States)

    Kiserud, Torvid

    2005-12-01

    Our understanding of fetal circulatory physiology is based on experimental animal data, and this continues to be an important source of new insight into developmental mechanisms. A growing number of human studies have investigated the human physiology, with results that are similar but not identical to those from animal studies. It is time to appreciate these differences and base more of our clinical approach on human physiology. Accordingly, the present review focuses on distributional patterns and adaptational mechanisms that were mainly discovered by human studies. These include cardiac output, pulmonary and placental circulation, fetal brain and liver, venous return to the heart, and the fetal shunts (ductus venosus, foramen ovale and ductus arteriosus). Placental compromise induces a set of adaptational and compensational mechanisms reflecting the plasticity of the developing circulation, with both short- and long-term implications. Some of these aspects have become part of the clinical physiology of today with consequences for surveillance and treatment.

  12. Proper Sizing of Circulation Pumps

    DEFF Research Database (Denmark)

    Tommerup, Henrik M.; Nørgaard, Jørgen

    2007-01-01

    , but the results can be applied to Europe in general. Despite the small sample of houses involved in the test, 15 houses, some rather safe conclusions can be drawn from the results, which showed that newly developed pumps with power consumption around 5-8 W, can perform the task of circulating the water......The paper describes the preliminary results from field tests of replacing various types of old pumps used for circulating water in heating systems in single- and double-family houses with new types of pumps. The tests were carried out in Denmark for the Danish Electricity Savings Trust...... sufficiently to keep the houses satisfactorily warm during the heating season of the test. The old replaced pumps used 5-10 times more power. In Europe alone, a gradual replacement of the present vastly oversized pumps with such small but sufficient pumps can save the construction of 17 large power plants...

  13. Journalism as Cultures of Circulation

    DEFF Research Database (Denmark)

    Bødker, Henrik

    2013-01-01

    The universe of journalism has always consisted of interspersed texts, meanings and practices. Yet, much journalism research has often isolated either texts and/or contexts and as such assumed relations between professional practices, informed (rational) readers and (conceived) core texts...... of journalism. It is, however, more important than ever to shift attention away from texts to the processes through which they are circulated. This is partly because the many cultural forms of journalism (textual, institutional, technological, material, behavioural and imagined) are undergoing significant......, likes, comments, searches, journalist roles, writing and reading positions and identities etc. Such forms will be traced within the mediation of a specific event with the overall aim of beginning a theorization of the landscape of journalism as highly interrelated cultures of circulation....

  14. Ocean circulation generated magnetic signals

    DEFF Research Database (Denmark)

    Manoj, C.; Kuvshinov, A.; Maus, S.

    2006-01-01

    Conducting ocean water, as it flows through the Earth's magnetic field, generates secondary electric and magnetic fields. An assessment of the ocean-generated magnetic fields and their detectability may be of importance for geomagnetism and oceanography. Motivated by the clear identification...... of ocean tidal signatures in the CHAMP magnetic field data we estimate the ocean magnetic signals of steady flow using a global 3-D EM numerical solution. The required velocity data are from the ECCO ocean circulation experiment and alternatively from the OCCAM model for higher resolution. We assume...... of the magnetic field, as compared to the ECCO simulation. Besides the expected signatures of the global circulation patterns, we find significant seasonal variability of ocean magnetic signals in the Indian and Western Pacific Oceans. Compared to seasonal variation, interannual variations produce weaker signals....

  15. Conservation of circulation in magnetohydrodynamics

    Science.gov (United States)

    Bekenstein; Oron

    2000-10-01

    We demonstrate at both the Newtonian and (general) relativistic levels the existence of a generalization of Kelvin's circulation theorem (for pure fluids) that is applicable to perfect magnetohydrodynamics. The argument is based on the least action principle for magnetohydrodynamic flow. Examples of the new conservation law are furnished. The new theorem should be helpful in identifying new kinds of vortex phenomena distinct from magnetic ropes or fluid vortices.

  16. Conservation of Circulation in Magnetohydrodynamics

    OpenAIRE

    Bekenstein, Jacob D.; Oron, Asaf

    2000-01-01

    We demonstrate, both at the Newtonian and (general) relativistic levels, the existence of a generalization of Kelvin's circulation theorem (for pure fluids) which is applicable to perfect magnetohydrodynamics. The argument is based on the least action principle for magnetohydrodynamic flow. Examples of the new conservation law are furnished. The new theorem should be helpful in identifying new kinds of vortex phenomena distinct from magnetic ropes or fluid vortices.

  17. Dynamics of Clouds and Mesoscale Circulations over the Maritime Continent

    Science.gov (United States)

    Jin, Y.; Wang, S.; Xian, P.; Reid, J. S.; Nachamkin, J.

    2010-12-01

    In recent decades Southeast Asia (SEA) has seen rapid economic growth as well as increased biomass burning, resulting in high air pollution levels and reduced air qual-ity. At the same time clouds often prevent accurate air-quality monitoring and analysis using satellite observations. The Seven SouthEast Asian Studies (7SEAS) field campaign currently underway over SEA provides an unprecedented opportunity to study the com-plex interplay between aerosol and clouds. 7SEAS is a comprehensive interdisciplinary atmospheric sciences program through international partnership of NASA, NRL, ONR and seven local institutions including those from Indonesia, Malaysia, the Philippines, Singapore, Taiwan, Thailand, and Vietnam. While the original goal of 7SEAS is to iso-late the impacts of aerosol particles on weather and the environment, it is recognized that better understanding of SEA meteorological conditions, especially those associated with cloud formation and evolution, is critical to the success of the campaign. In this study we attempt to gain more insight into the dynamic and physical processes associated with low level clouds and atmospheric circulation at the regional scale over SEA, using the Navy’s Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS® ), a regional forecast model in operation at FNMOC since 1998. This effort comprises two main components. First, multiple-years of COAMPS operational forecasts over SEA are analyzed for basic climatology of atmospheric fea-tures. Second, mesoscale circulation and cloud properties are simulated at relatively higher resolution (15-km) for selected periods in the Gulf of Tonkin and adjacent coastal areas. Simulation results are compared to MODIS cloud observations and local sound-ings obtained during 7SEAS for model verifications. Atmospheric boundary layer proc-esses are examined in relation to spatial and temporal variations of cloud fields. The cur-rent work serves as an important step toward improving our

  18. Hall Effect Gyrators and Circulators

    Science.gov (United States)

    Viola, Giovanni; DiVincenzo, David P.

    2014-04-01

    The electronic circulator and its close relative the gyrator are invaluable tools for noise management and signal routing in the current generation of low-temperature microwave systems for the implementation of new quantum technologies. The current implementation of these devices using the Faraday effect is satisfactory but requires a bulky structure whose physical dimension is close to the microwave wavelength employed. The Hall effect is an alternative nonreciprocal effect that can also be used to produce desired device functionality. We review earlier efforts to use an Ohmically contacted four-terminal Hall bar, explaining why this approach leads to unacceptably high device loss. We find that capacitive coupling to such a Hall conductor has much greater promise for achieving good circulator and gyrator functionality. We formulate a classical Ohm-Hall analysis for calculating the properties of such a device, and show how this classical theory simplifies remarkably in the limiting case of the Hall angle approaching 90°. In this limit, we find that either a four-terminal or a three-terminal capacitive device can give excellent circulator behavior, with device dimensions far smaller than the ac wavelength. An experiment is proposed to achieve GHz-band gyration in millimeter (and smaller) scale structures employing either semiconductor heterostructure or graphene Hall conductors. An inductively coupled scheme for realizing a Hall gyrator is also analyzed.

  19. Examining Tatooine: Atmospheric Models of Neptune-Like Circumbinary Planets

    CERN Document Server

    May, E M

    2016-01-01

    Circumbinary planets experience a time varying irradiation pattern as they orbit their two host stars. In this work, we present the first detailed study of the atmospheric effects of this irradiation pattern on known and hypothetical gaseous circumbinary planets. Using both a one-dimensional Energy Balance Model and a three-dimensional General Circulation Model, we look at the temperature differences between circumbinary planets and their equivalent single-star cases in order to determine the nature of the atmospheres of these planets. We find that for circumbinary planets on stable orbits around their host stars, temperature differences are on average no more than 1.0% in the most extreme cases. Based on detailed modeling with the General Circulation Model, we find that these temperature differences are not large enough to excite circulation differences between the two cases. We conclude that gaseous circumbinary planets can be treated as their equivalent single-star case in future atmospheric modeling effor...

  20. THE QUASI-BIWEEKLY OSCILLATION OF FLOOD-CAUSING TORRENTIAL RAIN IN XIJIANG RIVER REGION AND ITS ATMOSPHERIC CIRCULATION MODELS%西江流域致洪暴雨的准双周振荡及大气环流模型

    Institute of Scientific and Technical Information of China (English)

    纪忠萍; 胡丽甜; 谷德军; 吴乃庚; 梁健

    2011-01-01

    为了做好西江流域致洪暴雨的中期预报,采用小波分析、Lanczos滤波器分析了1961-2008年西江流域13次致洪暴雨期间降水与850 hPa风场的低频振荡特征,研究了850 hPa风场的10 ~ 30天低频传播对致洪暴雨的影响,并采用合成分析建立了由西风带系统导致的致洪暴雨准双周振荡的大气环流模型.结果表明,致洪暴雨期间降水主要以10~ 20天的准双周振荡为主,它们多数与西江流域850 hPa风场8~35天振荡的正位相有较好的对应关系.来自西江流域以南逐渐向北传播的低频纬向风或来自30°N附近逐渐南传并加强的低频纬向风与多数来自西北太平洋向西传播的低频纬向风在西江流域相遇,是导致致洪暴雨具有准双周振荡的可能原因之一.当500hPa巴尔喀什湖以东的高压脊开始隆起并逐渐东移,我国东北-华北-长江中下游逐渐转为明显的华北低槽控制,华南由青藏高原东部弱的西风槽转为明显的高空槽控制,副高不断加强西伸,同时850 hPa上空来自孟加拉湾穿过中南半岛的西南风不断加强,位于华南急流轴以西弱的气旋性弯曲也不断加强,地面上转为东高西低、等压线经向度明显,西江流域致洪暴雨开始并逐渐达到强盛期.这些特征可作为西江流域致洪暴雨的中期预报提供参考依据.%In order to have better medium-range forecasts of flood-causing torrential rains in the Xijiang river valley, the characteristics of low-frequency oscillations of rainfall in the valley and wind field at 850 hPa are studied, with wavelet transform and Lanczos filter, for 13 cases of such rains since 1961. The effect is studied of low-frequency propagation of 850 hPa wind field on the rains in the region. Using composite analysis, an atmospheric circulation model is constructed of quasi-biweekly oscillation of the rains that are caused by westerly systems. Results show that the rainfall exhibits mainly quasi

  1. The South Asian Monsoon Circulation in Moist Isentropic coordinates

    Science.gov (United States)

    Thazhe Purayil, Sabin; Pauluis, Olivier

    2016-04-01

    The atmospheric circulation and thermodynamic structure during the South Asian Summer Monsoon season is analyzed in isentropic coordinates through the mass transport represented in terms of the potential temperature and equivalent potential temperature. This approach, originally developed to analyze the global meridional circulation, makes it possible to identify the thermodynamic properties of the inflow and outflow of different air mass. To understand the thermodynamic properties of air mass in south Asian monsoon region, we have used three diagnostics; a) the joint distribution of the mass transport as a function of dry and moist entropy, b) the vertical mass flux over the monsoon domain and c) the mass transport and isentropic thickness for different moist ventilation range of tropical atmosphere. The thermodynamic properties of the various air masses, such as the inflow of warm moist air in the boundary layer, upper tropospheric outflow, and midlatitude dry air intrusion are being systematically identified. The isentropic distribution of the vertical mass flux transport in terms of equivalent potential temperature is used to explain the characteristics of ascending and descending air parcels over the Indian subcontinent. Diagnosis based on the isentropic thickness reveals that the regional monsoon circulation and associated precipitation features can be systematically explained by this method. This technique is used to study the evolution of the monsoon flow in the seasonal scale. We used the data from AMIP-type simulations carried out with prescribed Sea Surface Temperature and sea ice for a 25 year period (1981-2005) from the GFDL High-resolution atmospheric model (HiRAM) with an average grid spacing of ~25km over the globe.

  2. Circulation and Dissipation on Hot Jupiters

    Science.gov (United States)

    Li, J.; Goodman, J.

    2010-12-01

    Many global circulation models predict supersonic zonal winds and large vertical shears in the atmospheres of short-period Jovian exoplanets. Using linear analysis and nonlinear local simulations, we investigate hydrodynamic dissipation mechanisms to balance the thermal acceleration of these winds. The adiabatic Richardson criterion remains a good guide to linear stability, although thermal diffusion allows some modes to violate it at very long wavelengths and very low growth rates. Nonlinearly, wind speeds saturate at Mach numbers ≈2 and Richardson numbers lsim1/4 for a broad range of plausible diffusivities and forcing strengths. Turbulence and vertical mixing, though accompanied by weak shocks, dominate the dissipation, which appears to be the outcome of a recurrent Kelvin-Helmholtz instability. An explicit shear viscosity, as well as thermal diffusivity, is added to ZEUS to capture dissipation outside of shocks. The wind speed is neither monotonic nor single valued for a range of shear viscosities larger than about 10-3 of the sound speed times the pressure scale height. Coarsening the numerical resolution can also increase the speed. Hence global simulations that are incapable of representing vertical turbulence and shocks, either because of reduced physics or because of limited resolution, may overestimate wind speeds. We recommend that such simulations include artificial dissipation terms to control the Mach and Richardson numbers and to capture mechanical dissipation as heat.

  3. Antarctic glaciation caused ocean circulation changes at the Eocene-Oligocene transition.

    Science.gov (United States)

    Goldner, A; Herold, N; Huber, M

    2014-07-31

    Two main hypotheses compete to explain global cooling and the abrupt growth of the Antarctic ice sheet across the Eocene-Oligocene transition about 34 million years ago: thermal isolation of Antarctica due to southern ocean gateway opening, and declining atmospheric CO2 (refs 5, 6). Increases in ocean thermal stratification and circulation in proxies across the Eocene-Oligocene transition have been interpreted as a unique signature of gateway opening, but at present both mechanisms remain possible. Here, using a coupled ocean-atmosphere model, we show that the rise of Antarctic glaciation, rather than altered palaeogeography, is best able to explain the observed oceanographic changes. We find that growth of the Antarctic ice sheet caused enhanced northward transport of Antarctic intermediate water and invigorated the formation of Antarctic bottom water, fundamentally reorganizing ocean circulation. Conversely, gateway openings had much less impact on ocean thermal stratification and circulation. Our results support available evidence that CO2 drawdown--not gateway opening--caused Antarctic ice sheet growth, and further show that these feedbacks in turn altered ocean circulation. The precise timing and rate of glaciation, and thus its impacts on ocean circulation, reflect the balance between potentially positive feedbacks (increases in sea ice extent and enhanced primary productivity) and negative feedbacks (stronger southward heat transport and localized high-latitude warming). The Antarctic ice sheet had a complex, dynamic role in ocean circulation and heat fluxes during its initiation, and these processes are likely to operate in the future.

  4. LAND-SEA THERMAL CONTRAST OVER SOUTH ASIA AND ITS INFLUENCES ON TROPICAL MONSOON CIRCULATION

    Institute of Scientific and Technical Information of China (English)

    WANG Tong-mei; WU Guo-xiong

    2008-01-01

    Based on the NCEP/NCAR reanalysis data, the thermodynamic features and the effect of spatially nonuniform heating on the circulation of the tropical monsoon area in South Asia due to the land- sea distribution have been analyzed, The influences of the subcontinent topography on the Asian tropical circulation are mostly characterized by its thermodynamic effects on low-level circulation, of which the strongest is observed in winter and spring but the relatively weak in summer, followed by the weakest in autumn. The thermodynamic difference between the lndo china Peninsula and Indian Peninsula and its influence on the circulation are regulated by the Tibetan Plateau. During the transitional period from spring to early summer, the Tibetan Plateau thermal forcing generates a large-scale cyclonic circulation in low latitudes in the lower troposphere. As a result, the southerlies/northerlies are increased to the east/west of the Bay of Bengal, Therefore latent heating of the atmosphere is strengthened and the surface sensible heating over the Indochina Peninsula is weakened. On the other hand the surface sensible heating over the Indian Peninsula is increased. It is shown that heating with various scales and different kinds can affect the tropical atmosphere in different ways, which lead to the unique characteristics of the tropical Asian circulation.

  5. Atmospheric dynamics of Earth-like tidally locked aquaplanets

    Directory of Open Access Journals (Sweden)

    Tapio Schneider

    2010-12-01

    Full Text Available We present simulations of atmospheres of Earth-like aquaplanets that are tidally locked to their star, that is, planets whose orbital period is equal to the rotation period about their spin axis, so that one side always faces the star and the other side is always dark. Such simulations are of interest in the study of tidally locked terrestrial exoplanets and as illustrations of how planetary rotation and the insolation distribution shape climate. As extreme cases illustrating the effects of slow and rapid rotation, we consider planets with rotation periods equal to one current Earth year and one current Earth day. The dynamics responsible for the surface climate (e.g., winds, temperature, precipitation and the general circulation of the atmosphere are discussed in light of existing theories of atmospheric circulations. For example, as expected from the increasing importance of Coriolis accelerations relative to inertial accelerations as the rotation rate increases, the winds are approximately isotropic and divergent at leading order in the slowly rotating atmosphere but are predominantly zonal and rotational in the rapidly rotating atmosphere. Free-atmospheric horizontal temperature variati