WorldWideScience

Sample records for atmospheric circulation anomalies

  1. The relationship between sea surface temperature anomalies and atmospheric circulation in general circulation model experiments

    International Nuclear Information System (INIS)

    Several multi-year integrations of the Hamburg version of the ECMWF/T21 general circulation model driven by the sea surface temperature (SST) observed in the period 1970-1988 were examined to study the extratropical response of the atmospheric circulation to SST anomalies in the Northern Hemisphere in winter. In the first 19-years run SST anomalies were prescribed globally (GAGO run), and in two others SST variability was limited to extratropical regions (MOGA run) and to tropics (TOGA run), respectively. A canonical correlation analysis was applied to the monthly means to find the best correlated patterns of SST anomalies in the Atlantic and Pacific Oceans and the Northern Hemisphere atmospheric flow. Contrary to expectation, the extratropical response in the GAGO run is not equal to the linear combination of the responses in the MOGA and TOGA runs. In the GAGO integration with globally prescribed SST the best correlated atmospheric pattern is global and is characterized by dipole structures of the same polarity in the North Atlantic and the North Pacific sectors. In the MOGA and TOGA experiments the atmospheric response is more local with main centers in the North Atlantic and North Pacific, respectively. The atmospheric modes found by the CCA were compared with the normal modes of the barotropic vorticity equation linearized about the 500 mb winter climate of the control integration driven by the climatological SST. The normal modes with smallest eigenvalues are similar to the canonical patterns of 500 mb geopotential height. The corresponding eigenvectors of the adjoint operator, which represent an external forcing optimal for exciting normal modes, have a longitudinal structure with maxima in regions characterized by enhanced high frequency baroclinic activity over both oceans. It was suggested that variability of storm tracks could play an important role in variability of the barotropic normal modes. (orig.)

  2. Atmospheric circulation anomalies during two persistent north american droughts: 1932-1939 and 1948-1957

    Science.gov (United States)

    Cook, Benjamin I.; Seager, Richard; Miller, Ron L.

    2011-06-01

    We use an early twentieth century (1908-1958) atmospheric reanalysis, based on assimilation of surface and sea level pressure observations, to contrast atmospheric circulation during two periods of persistent drought in North America: 1932-1939 (the `Dust Bowl') and 1948-1957. Primary forcing for both droughts is believed to come from anomalous sea surface temperatures (SSTs): a warm Atlantic and a cool eastern tropical Pacific. For boreal winter (October-March) in the 1950s, a stationary wave pattern originating from the tropical Pacific is present, with positive centers over the north Pacific and north Atlantic ocean basins and a negative center positioned over northwest North America and the tropical/subtropical Pacific. This wave train is largely absent for the 1930s drought; boreal winter height anomalies are organized much more zonally, with positive heights extending across northern North America. For boreal summer (April-September) during the 1930s, a strong upper level ridge is centered over the Great Plains; this feature is absent during the 1950s and appears to be linked to a weakening of the Great Plains low-level jet (GPLLJ). Subsidence anomalies are co-located over the centers of each drought: in the central Great Plains for the 1930s and in a band extending from the southwest to the southeastern United States for the 1950s. The location and intensity of this subsidence during the 1948-1957 drought is a typical response to a cold eastern tropical Pacific, but for 1932-1939 deviates in terms of the expected intensity, location, and spatial extent. Overall, circulation anomalies during the 1950s drought appear consistent with the expected response to the observed SST forcing. This is not the case for the 1930s, implying some other causal factor may be needed to explain the Dust Bowl drought anomalies. In addition to SST forcing, the 1930s were also characterized by massive alterations to the land surface, including regional-scale devegetation from crop

  3. Relationship between North American winter temperature and large-scale atmospheric circulation anomalies and its decadal variation

    Science.gov (United States)

    Yu, B.; Lin, H.; Wu, Z. W.; Merryfield, W. J.

    2016-07-01

    The interannual relationship between North American (NA) winter temperature and large-scale atmospheric circulation anomalies and its decadal variation are analyzed. NA temperature anomalies are dominated by two leading maximum covariance analysis (MCA) modes of NA surface temperature and Northern Hemisphere 500 hPa geopotential anomalies. A new teleconnection index, termed the Asian-Bering-North American (ABNA) pattern, is constructed from the normalized geopotential field after linearly removing the contribution of the Pacific-North American (PNA) pattern. The ABNA pattern is sustained by synoptic eddy forcing. The first MCA mode of NA surface temperature is highly correlated with the PNA and ABNA teleconnections, and the second mode with the North Atlantic Oscillation (NAO). This indicates that NA temperature is largely controlled by these three large-scale atmospheric patterns, i.e., the PNA, ABNA and NAO. These temperature-circulation relationships appear stationary in the 20th century.

  4. 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".

  5. 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.

  6. RELATION BETWEEN SUMMER TYPHOON FREQUENCY ANOMALIES IN WEST PACIFIC AND ENSO EVENTS AND THE ANOMALOUS ATMOSPHERIC CIRCULATION CHARACTERISTICS

    Institute of Scientific and Technical Information of China (English)

    ZHOU Xue-ming; WEI Ying-zhi; WU Chen-feng

    2006-01-01

    By using data of serially numbered typhoons in northwestern Pacific and NOAA OLR data and NCEP/NCAR reanalysis data of wind field, based on the statistics and study of the relationship between the calendar years with more (or fewer) summer typhoons and ENSO events, we compared the composites of OLR eigenvectors and tropical summer wind fields during El Ni(n)o and La Ni(n)o events with more or fewer than normal summer typhoons, respectively. The results show that, in summer, without remarkable systematic anomalies of Mascarene High and Australia High in South Hemisphere, the anomaly of Walker circulation will dominate and follow the rule of ENSO impacts to atmospheric circulation and typhoon frequency. Otherwise,when systematic anomalies of Australia High appear during the El Ni(n)o events, circulation anomalies in the South Hemisphere will dominate, and many more typhoons will occur. In 1999, which is a special year of La Ni(n)a events, northward and eastward monsoon was induced by the stronger Mascarene High, and fewer typhoons arose. The typhoon source are regions where weak vertical wind shear, warm pool in western Pacific and the area with monsoon troughs are overlapping with each other. Finally, this paper analyzes and compares the source locations and ranges of more (fewer) typhoons in the events of El Ni(n)o and La Ni(n)o, respectively.

  7. Dominant modes of Diurnal Temperature Range variability over Europe and their relationships with large-scale atmospheric circulation and sea surface temperature anomaly patterns

    OpenAIRE

    Ionita, Monica; Lohmann, Gerrit; Rimbu, Norel; Scholz, Patrick

    2012-01-01

    The relationships between the dominant modes of interannual variability of Diurnal Temperature Range (DTR) over Europe and large-scale atmospheric circulation and sea surface temperature anomaly fields are investigated through statistical analysis of observed and reanalysis data. It is shown that the dominant DTR modes as well as their relationship with large-scale atmospheric circulation and sea surface temperature anomaly fields are specific for each season. During winter the first and seco...

  8. 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.

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

    Science.gov (United States)

    Cahynova, Monika; Huth, Radan

    2010-05-01

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

  10. Comparison of month-to-month persistence of anomalies in a general circulation model and in the Earth's atmosphere

    Energy Technology Data Exchange (ETDEWEB)

    van den Dool, H.M.; Chervin, R.M.

    1986-07-15

    The output of a 20-year integration of an annual cycle (AC) version of the NCAR Community Climate Model in which the external conditions went through 20 prescribed identical annual cycles is used to study month-to-month persistence of anomalies in monthly mean atmospheric circulation fields on a global and a hemispheric scale. Of all fields considered, the height fields (1000-300 mb) are the most persistent and the transient eddy flux fields the least persistent. Persistence in height field anomalies is largest in winter and small throughout the rest of the year. For the area north of 20/sup 0/N, a comparison is made with the persistence of monthly mean height and temperature fields observed in the real world (RW) during a 28-year interval. On a pooled all month-pairs basis, RW height anomaly fields are significantly more persistent than those appearing in AC but, from a practical point of view, the difference is small. The differences in persistence are larger for temperature anomalies (500-1000 mb thickness) than for height. Differences between RW and AC monthly persistence over the area north of 20/sup 0/N are largest in summer when the RW has a local maximum in persistence. On the assumption that the model and atmosphere have the same internal dynamics, the differences just described can be attributed to the interaction of the atmosphere with external or boundary conditions (e.g., ocean surface temperatures), which was purposely omitted from the AC integration. Interaction with the lower boundary in summer seems, therefore, to be quite important to explain the observed level of month-to-month persistence in circulation anomalies. In winter, however, the internal dynamics of the atmosphere alone produces the required observed level of month-to-month persistence. 20 references, 6 figures, 7 tables.

  11. Climatic impacts of greenhouse gas concentration changes under glacial and interglacial conditions: polar amplification, land/sea warming ratio, atmospheric circulation anomalies

    International Nuclear Information System (INIS)

    Full text: We study the temperature response of a glacial and an interglacial climate to a greenhouse gas (GHG) concentration change in an ocean-atmosphere coupled model, IPSLCM4. Except for the GHG concentrations which are imposed to different values, the glacial climate is defined from the boundary conditions of the Last Glacial Maximum (LGM) as defined in the second phase of the Paleoclimate Modelling Intercomparasion Project (PMIP2). The interglacial climate consists of modern boundary conditions. The response to a GHG concentration varying from LGM to pre-industrial values is similar for both boundary conditions, but enhanced under modern ones. The model simulates the classical amplification of the temperature response in the northern high latitudes compared to lower latitudes and over the land surfaces compared to the oceanic ones. The physical reasons for the different temperature warmings according to the latitude and to the surface type are studied through an analysis of the energy fluxes anomalies. The high latitudes warm more due to strong sea-ice and snow albedo feedbacks, along with cloud cover increases that result in a radiative warming. Concerning the land-sea warming ratio, our study highlights the role played by the evaporation differential response between the two types of surface. The latitudinal variations of the land/sea warming ratio are due to variations in the anomalies in albedo changes, evaporation, cloud cover change and water vapour air content. The local amplifications or attenuations of the zonally-averaged warming are enhanced under modern boundary conditions compared to glacial ones, due to a greater land albedo feedback, water vapour increase and enhanced air/sea sensible heat fluxes changes in the northern hemisphere and mostly due to oceanic advection processes in the southern hemisphere. The consequences in terms of atmospheric circulation are anomalous stationary waves in the northern hemisphere with lower pressures over lands

  12. 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...

  13. 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...

  14. Atmospheric Circulation of Terrestrial Exoplanets

    OpenAIRE

    Showman, Adam P.; Wordsworth, Robin D.; 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 a...

  15. The general circulation of the atmosphere

    OpenAIRE

    Schneider, Tapio

    2006-01-01

    Theories of how Earth's surface climate may change in the future, of how it may have been in the past, and of how it is related to climates of other planets must build upon a theory of the general circulation of the atmosphere. The view of the atmospheric general circulation presented here focuses not on Earth's general circulation as such but on a continuum of idealized circulations with axisymmetric flow statistics. Analyses of observational data for Earth's atmosphere, simulations with ide...

  16. Variation in the Earth's Angular Velocity Resulting from Fluctuations in Atmospheric and Oceanic Circulation

    OpenAIRE

    Munk, W. H.; Miller, R. L.

    2011-01-01

    Fluctuations in the circulation of the atmosphere are associated with very small anomalies in the angular velocity of the earth. The seasonal component of these anomalies has been computed from weather maps, and is found to agree, with respect to magnitude and phase, with anomalies first reported by STOKYO in 1936 on the basis of astronomic observations. The effects of fluctuations in the oceanic circulation, and of shifting of air and water masses, have been estimated to account for not more...

  17. The observational influence of the North Atlantic SST tripole on the early spring atmospheric circulation

    Science.gov (United States)

    Han, Zhe; Luo, Feifei; Wan, Jianghua

    2016-03-01

    This study investigated the forcing of the North Atlantic sea surface temperature (SST) tripole on the North Atlantic Oscillation (NAO)-like circulation in early spring (February-April) in observations. Corresponding to an SST tripole forcing in early spring, the atmospheric circulation is very weak and insignificant. However, further analyses indicate that the observational effect of the SST anomalies on the NAO-like circulation is disturbed by the concomitant sea ice anomalies. With the linear effects of sea ice anomalies removed, there is an equivalent barotropic NAO-like circulation in early spring related to a North Atlantic SST tripole.

  18. Dipole anomaly in the Arctic atmosphere and winter Arctic sea ice motion

    Institute of Scientific and Technical Information of China (English)

    WU; Bingyi; ZHANG; Renhe

    2005-01-01

    This paper investigates a previously-ignored atmospheric circulation anomaly-di- pole structure anomaly in the arctic atmosphere, and its relationship with the winter sea ice motion, based on analyses of the International Arctic Buoy Programme Data (1979-1998) and datasets from the National Center for Environmental Prediction (NCEP) and the National Center for Atmospheric Research (NCAR) for the period of 1960-2002. The dipole structure anomaly is the second-leading mode of EOF of monthly mean SLP north of 70(N during the winter season (Oct.-Mar.), which accounts for 13% of the variance. One of its two anomaly centers is over the Canadian Archipelago; the other is situated over northern Eurasia and the Siberian marginal seas. Due to the dipole structure anomaly's strong meridionality, it becomes an important mechanism to drive both anomalous sea ice export out of the Arctic Basin and cold air outbreaks into the Barents Sea, the Nordic Seas and northern Europe.

  19. Southern Meridional Atmospheric Circulation Associated with IOD

    Institute of Scientific and Technical Information of China (English)

    LIU Na; CHEN Hongxia

    2006-01-01

    Using the monthly wind and sea surface temperature (SST) data, southern meridional atmospheric circulation cells associated with the Indian Ocean Dipole Mode (IOD) events in the Indian Ocean are for the first time described and examined. The divergent wind and pressure vertical velocity are employed for the identification of atmospheric circulation cells. During the four different phases of the positive IOD events, the anomalous meridional Hadley circulation over the western Indian Ocean shows that the air rises in the tropics, flows poleward in the upper troposphere, sinks in the subtropics, and returns back to the tropics in the lower troposphere. The anomalous Hadley circulation over the eastern Indian Ocean is opposite to that over the western Indian Ocean. During positive IOD events, the meridional Hadley circulation over the eastern Indian Ocean is weakened while it is strengthened over the western Indian Ocean. Correlation analysis between the IOD index and the indices of the Hadley cells also proves that, the atmospheric circulation patterns are evident in every IOD event over the period of record.

  20. An analysis of the relationship between cloud anomalies and sea surface temperature anomalies in a global circulation model

    Science.gov (United States)

    Peterson, Thomas C.; Barnett, Tim P.; Roeckner, Erich; Vonder Haar, Thomas H.

    1992-01-01

    The relationship between the sea surface temperature anomalies (SSTAs) and the anomalies of the monthly mean cloud cover (including the high-level, low-level, and total cloud cover), the outgoing longwave radiation, and the reflected solar radiation was analyzed using a least absolute deviations regression at each grid point over the open ocean for a 6-yr period. The results indicate that cloud change in association with a local 1-C increase in SSTAs cannot be used to predict clouds in a potential future world where all the oceans are 1-C warmer than at present, because much of the observed cloud changes are due to circulation changes, which in turn are related not only to changes in SSTAs but to changes in SSTA gradients. However, because SSTAs are associated with changes in the local ocean-atmosphere moisture and heat fluxes as well as significant changes in circulation (such as ENSO), SSTAs can serve as a surrogate for many aspects of global climate change.

  1. Circulation anomalies associated with winter temperature extremes in Athens during the period 1900-2004

    Energy Technology Data Exchange (ETDEWEB)

    Founda, D. [National Observatory of Athens (Greece). Inst. for Environmental Research and Sustainable Development; Loon, H. van [Colorado Univ., Boulder, CO (United States)

    2008-02-15

    We use the long series of temperature observed at the National Observatory of Athens, Greece, to examine the extremes of this element together with associated anomalies in the general circulation of the atmosphere. The 13 extreme-cold and 20 extreme-warm winters during the period 1900-2004 (equal to or below minus one standard deviation, and equal to or above plus one standard deviation respectively) had opposite pressure anomalies, mainly over the North Atlantic and Eurasia. The temperature extremes at Athens were representative of most of the Mediterranean and the Balkans, and their associated pressure anomalies were robust. The extremes of the Index of the North Atlantic Oscillation (the pressure difference between Gibraltar and Iceland) were not a good indicator of the temperature extremes in the Mediterranean. Rather the extreme temperature anomalies over the Mediterranean region are to a large extent controlled by a bipolar pattern of SLP (see level pressure) anomalies with centers over the British Isles and the Arctic. (orig.)

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

    Science.gov (United States)

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

    2001-01-01

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

  3. The atmospheric response to North Atlantic SST anomalies in seasonal prediction experiments

    OpenAIRE

    Lin, Hai; DEROME, JACQUES

    2011-01-01

    Seasonal forecasts performed over a 26 yr period as part of the Historical Seasonal Forecasting Project (HFP) are used to analyze the influence of North Atlantic sea surface temperature (SST) anomalies on the atmospheric circulation, its seasonality, and model dependence. The signals related to the El Ni˜no events are first removed from both the SST and the atmospheric data. The North Atlantic SST and the ensemble mean forecast are then correlated over the 26 yr to identify the model response...

  4. Potential ocean–atmosphere preconditioning of late autumn Barents-Kara sea ice concentration anomaly

    Directory of Open Access Journals (Sweden)

    Martin P. King

    2016-02-01

    Full Text Available Many recent studies have revealed the importance of the climatic state in November on the seasonal climate of the subsequent winter. In particular, it has been shown that interannual variability of sea ice concentration (SIC over the Barents-Kara (BK seas in November is linked to winter atmospheric circulation anomaly that projects on the North Atlantic Oscillation. Understanding the lead–lag processes involving the different components of the climate system from autumn to winter is therefore important. This note presents dynamical interpretation for the ice-ocean–atmosphere relationships that can affect the BK SIC anomaly in late autumn. It is found that cyclonic (anticyclonic wind anomaly over the Arctic in October, by Ekman drift, can be responsible for positive (negative SIC in the BK seas in November. The results also suggest that ocean heat transport via the Barents Sea Opening in September and October can contribute to BK SIC anomaly in November.

  5. The influence of atmospheric circulation on the mid-Holocene climate of Europe: a data-model comparison

    Directory of Open Access Journals (Sweden)

    A. Mauri

    2013-10-01

    Full Text Available The atmospheric circulation is a key area of uncertainty in climate model simulations of future climate change, especially in mid-latitude regions such as Europe where atmospheric dynamics have a significant role in climate variability. It has been proposed that the mid-Holocene was characterized in Europe by a stronger westerly circulation in winter comparable with a more positive AO/NAO, and a weaker westerly circulation in summer caused by anti-cyclonic blocking near Scandinavia. Model simulations indicate at best only a weakly positive AO/NAO, whilst changes in summer atmospheric circulation have not been widely investigated. Here we use a new pollen-based reconstruction of European mid-Holocene climate to investigate the role of atmospheric circulation in explaining the spatial pattern of seasonal temperature and precipitation anomalies. We find that the footprint of the anomalies is entirely consistent with those from modern analogue atmospheric circulation patterns associated with a strong westerly circulation in winter (positive AO/NAO and a weak westerly circulation in summer (positive SCAND. We find little agreement between the reconstructed anomalies and those from a climate model simulation, which as with most model simulations shows a much greater sensitivity to local radiative forcing from top-of-the-atmosphere changes in solar insolation. Our findings are consistent with data-model comparisons on contemporary timescales that indicate that models underestimate the role of atmospheric circulation in climate change, whilst also highlighting the importance of atmospheric dynamics in explaining interglacial warming.

  6. Fluctuation Theorem in an Atmospheric Circulation Model

    CERN Document Server

    Schalge, Bernd; Wouters, Jeroen; Fraedrich, Klaus; Lunkeit, Frank

    2012-01-01

    Evidence for the validity of the Fluctuation Theorem (FT) in an atmospheric Global Circulation Model is found. The model is hydrostatic with variable numbers of vertical levels and different horizontal resolutions. For finite time intervals the largest local Lyapunov exponent (LLLE) is found to be negative consistent with predictions of the FT. The effect is present for resolutions up to wave numbers l=42 (~ 250km) and 10 levels.

  7. The transient atmospheric response to midlatitude SST anomalies

    OpenAIRE

    Ferreira, David; Frankignoul, Claude

    2005-01-01

    To study the transient atmospheric response to midlatitude SST anomalies, a three-layer quasigeostrophic (QG) model coupled to a slab oceanic mixed layer in the North Atlantic is used. As diagnosed from a coupled run in perpetual winter conditions, the first two modes of SST variability are linked to the model North Atlantic Oscillation (NAO) and eastern Atlantic pattern (EAP), respectively, the dominant atmospheric modes in the Atlantic sector. The two SST anomaly patterns are then prescribe...

  8. Potential ocean–atmosphere preconditioning of late autumn Barents-Kara sea ice concentration anomaly

    OpenAIRE

    King, Martin P.; García-Serrano, Javier

    2016-01-01

    Many recent studies have revealed the importance of the climatic state in November on the seasonal climate of the subsequent winter. In particular, it has been shown that interannual variability of sea ice concentration (SIC) over the Barents-Kara (BK) seas in November is linked to winter atmospheric circulation anomaly that projects on the North Atlantic Oscillation. Understanding the lead lag processes involving the different components of the climate system from autumn to winter is therefo...

  9. Tropical Atmospheric Circulations with Humidity Effects

    CERN Document Server

    Hsia, Chun-Hsiung; Ma, Tian; Wang, Shouhong

    2011-01-01

    The main objective of this article is to study the effect of the moisture on the planetary scale atmospheric circulation over the tropics. The modeling we adopt is the Boussinesq equations coupled with a diffusive equation of humidity and the humidity dependent heat source is modeled by a linear approximation of the humidity. The rigorous mathematical analysis is carried out using the dynamic transition theory. In particular, we obtain the same types of transitions and hence the scenario of the El Ni\\~no mechanism as described in \\cite{MW2,MW3}. The effect of the moisture only lowers slightly the magnitude of the critical thermal Rayleigh number.

  10. Particle pollution changes the atmospheric circulation

    International Nuclear Information System (INIS)

    Industrial emissions and combustion of fossil fuels create large amounts of sulfate- and carbon containing soot particles. These mix with natural particles to change the natural aerosols. Such anthropogenic changes in the aerosols may have a great impact on the climate of the earth. Altered properties of the aerosols may change the atmosphere's absorption and reflection of solar radiation and contribute to heating or cooling. This is the direct effect. Changes in the properties of aerosols may also affect the number and size of recently formed cloud droplets. This may change the ability of the clouds to reflect solar radiation and to produce precipitation. This is the indirect effect. Recent research at the University of Oslo shows that anthropogenic particles significantly change the atmospheric circulation, in particular in the tropics, but also at European latitudes

  11. 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

  12. Nucla circulating atmospheric fluidized bed demonstration project

    Energy Technology Data Exchange (ETDEWEB)

    Keith, Raymond E.

    1991-10-01

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

  13. Atmospheric multidecadal variations in the North Atlantic realm: proxy data, observations, and atmospheric circulation model studies

    Directory of Open Access Journals (Sweden)

    K. Grosfeld

    2007-01-01

    Full Text Available We investigate the spatial and temporal characteristics of multidecadal climate variability in the North Atlantic realm, using observational data, proxy data and model results. The dominant pattern of multidecadal variability of SST depicts a monopolar structure in the North Atlantic during the instrumental period with cold (warm phases during 1900–1925 and 1970–1990 (1870–1890 and 1940–1960. Two atmospheric general circulation models of different complexity forced with global SST over the last century show SLP anomaly patterns from the warm and cold phases of the North Atlantic similar to the corresponding observed patterns. The analysis of a sediment core from Cariaco Basin, a coral record from the northern Red Sea, and a long-term sea level pressure (SLP reconstruction reveals that the multidecadal mode of the atmospheric circulation characterizes climate variability also in the pre-industrial era. The analyses of SLP reconstruction and proxy data depict a persistent atmospheric mode at least over the last 300 years, where SLP shows a dipolar structure in response to monopolar North Atlantic SST, in a similar way as the models' responses do. The combined analysis of observational and proxy data with model experiments provides an understanding of multidecadal climate modes during the late Holocene. The related patterns are useful for the interpretation of proxy data in the North Atlantic realm.

  14. Atmospheric multidecadal variations in the North Atlantic realm: proxy data, observations, and atmospheric circulation model studies

    Directory of Open Access Journals (Sweden)

    K. Grosfeld

    2006-08-01

    Full Text Available We investigate the spatial and temporal characteristics of multidecadal climate variability in the North Atlantic realm, using observational data, proxy data and model results. The dominant pattern of multidecadal variability of SST depicts a monopolar structure in the North Atlantic during the instrumental period with cold (warm phases during 1900–1925 and 1970–1990 (1870–1890 and 1940–1960. Two atmospheric general circulation models of different complexity forced with global SST over the last century show SLP anomaly patterns from the warm and cold phases of the North Atlantic similar to the corresponding observed patterns. The analysis of a sediment core from Cariaco Basin, a coral record from the northern Red Sea, and a long-term sea level pressure (SLP reconstruction reveals that the multidecadal mode of the atmospheric circulation characterizes climate variability also in the pre-industrial era. The analyses of SLP reconstruction and proxy data depict a persistent atmospheric mode at least over the last 300 years, where SLP shows a dipolar structure in response to monopolar North Atlantic SST, in a similar way as the models' responses do. The combined analysis of observational and proxy data with model experiments provides an understanding of multidecadal climate modes during the late Holocene. The related patterns are useful for the interpretation of proxy data in the North Atlantic realm.

  15. The Empirical Forcing Function as a tool for the diagnosis of large-scale atmospheric anomalies

    Directory of Open Access Journals (Sweden)

    C. Andrade

    2010-01-01

    Full Text Available The time-mean quasi-geostrophic potential vorticity equation of the atmospheric flow on isobaric surfaces can explicitly include an atmospheric (internal forcing term of the stationary-eddy flow. In fact, neglecting some non-linear terms in this equation, this forcing can be mathematically expressed as a single function, called Empirical Forcing Function (EFF, which is equal to the material derivative of the time-mean potential vorticity. Furthermore, the EFF can be decomposed as a sum of seven components, each one representing a forcing mechanism of different nature. These mechanisms include diabatic components associated with the radiative forcing, latent heat release and frictional dissipation, and components related to transient eddy transports of heat and momentum. All these factors quantify the role of the transient eddies in forcing the atmospheric circulation. In order to assess the relevance of the EFF in diagnosing large-scale anomalies in the atmospheric circulation, the relationship between the EFF and the occurrence of strong North Atlantic ridges over the Eastern North Atlantic is analyzed, which are often precursors of severe droughts over Western Iberia. For such events, the EFF pattern depicts a clear dipolar structure over the North Atlantic; cyclonic (anticyclonic forcing of potential vorticity is found upstream (downstream of the anomalously strong ridges. Results also show that the most significant components are related to the diabatic processes. Lastly, these results highlight the relevance of the EFF in diagnosing large-scale anomalies, also providing some insight into their interaction with different physical mechanisms.

  16. Seasonal modes of dryness and wetness variability over Europe and their connections with large scale atmospheric circulation and global sea surface temperature

    OpenAIRE

    Ionita, Monica; Boroneant, Constanta; Chelcea, Silvia

    2015-01-01

    The relationship between the seasonal modes of interannual variability of a multiscalar drought index over Europe and the large-scale atmospheric circulation and sea surface temperature (SST) anomaly fields is investigated through statistical analysis of observed and reanalysis data. It is shown that the seasonal modes of dryness and wetness variability over Europe and their relationship with the large-scale atmospheric circulation and global SST anomaly fields differ from one season to anoth...

  17. Global thermohaline circulation. Part II: Sensitivity with interactive atmospheric transports

    OpenAIRE

    Wang, X.; Stone, P.; Marotzke, J.

    1999-01-01

    A hybrid coupled ocean-atmosphere model is used to investigate the stability of the thermohaline circulation (THC) to an increase in the surface freshwater forcing in the presence of interactive meridional transports in the atmosphere. The ocean component is the idealized global general circulation model used in Part I. The atmospheric model assumes fixed latitudinal structure of the heat and moisture transports, and the amplitudes are calculated separately for each hemisphere from the large-...

  18. The Role of Rossby Wave Breaking in Shaping the Equilibrium Atmospheric Circulation Response to North Atlantic Boundary Forcing

    OpenAIRE

    Strong, Courtenay; Magnusdottir, Gudrun

    2010-01-01

    The role of Rossby wave breaking (RWB) is explored in the transient response of an atmospheric general circulation model to boundary forcing by sea ice anomalies related to the North Atlantic Oscillation (NAO). When the NCAR Community Climate Model, version 3, was forced by an exaggerated sea ice extent anomaly corresponding to one arising from a positive NAO, a localized baroclinic response developed and evolved into a larger-scale equivalent barotropic pattern resembling the negative polari...

  19. Variation in summer surface air temperature over Northeast Asia and its associated circulation anomalies

    Science.gov (United States)

    Chen, Wei; Hong, Xiaowei; Lu, Riyu; Jin, Aifen; Jin, Shizhu; Nam, Jae-Cheol; Shin, Jin-Ho; Goo, Tae-Young; Kim, Baek-Jo

    2016-01-01

    This study investigates the interannual variation of summer surface air temperature over Northeast Asia (NEA) and its associated circulation anomalies. Two leading modes for the temperature variability over NEA are obtained by EOF analysis. The first EOF mode is characterized by a homogeneous temperature anomaly over NEA and therefore is called the NEA mode. This anomaly extends from southeast of Lake Baikal to Japan, with a central area in Northeast China. The second EOF mode is characterized by a seesaw pattern, showing a contrasting distribution between East Asia (specifically including the Changbai Mountains in Northeast China, Korea, and Japan) and north of this region. This mode is named the East Asia (EA) mode. Both modes contribute equivalently to the temperature variability in EA. The two leading modes are associated with different circulation anomalies. A warm NEA mode is associated with a positive geopotential height anomaly over NEA and thus a weakened upper-tropospheric westerly jet. On the other hand, a warm EA mode is related to a positive height anomaly over EA and a northward displaced jet. In addition, the NEA mode tends to be related to the Eurasian teleconnection pattern, while the EA mode is associated with the East Asia-Pacific/Pacific-Japan pattern.

  20. A coupled, zonally averages atmosphere-ocean model: Variability of the thermohaline circulation

    International Nuclear Information System (INIS)

    Two experiments with a recently developed zonally averaged climate model which includes the ocean's thermohaline circulation are performed. The first experiment simulates a global thermohaline circulation in which deep water is formed in the North Atlantic, flows as a deep current into the Pacific basin and then upwells. The water is returned as a near-surface flow through the Indian Ocean into the South Atlantic. The present model reproduces a global deep circulation under present-day forcing and shows that the zonal atmospheric water vapor transport is of importance. The second experiment studies the effect of glacial meltwater runoff at different latitudes on the thermohaline circulation, meridional heat flux and surface air temperature. Depending on the strength and position of the forcing anomaly, severe cooling can be observed in high northern latitudes. The mechanism may provide further insight into the Younger Dryas climate event

  1. Global climate and ocean circulation on an aquaplanet ocean-atmosphere general circulation model

    OpenAIRE

    Smith, R.; Dubois, C.; Marotzke, J.

    2006-01-01

    A low-resolution coupled ocean–atmosphere general circulation model (OAGCM) is used to study the characteristics of the large-scale ocean circulation and its climatic impacts in a series of global coupled aquaplanet experiments. Three configurations, designed to produce fundamentally different ocean circulation regimes, are considered. The first has no obstruction to zonal flow, the second contains a low barrier that blocks zonal flow in the ocean at all latitudes, creating a single enclosed ...

  2. 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.

  3. 黄土高原中部秋季干湿的年际和年代际环流异常特征及与海温的多尺度相关性研究%Interannual and interdecadal atmospheric circulation anomalies of autumn dry/wet over the loess plateau and its multi-scalar correlation to SST

    Institute of Scientific and Technical Information of China (English)

    刘晓云; 王劲松; 李栋梁; 岳平; 李耀辉; 姚玉璧

    2013-01-01

    The ecological environment is vulnerable and extremely sensitive to climate change in the loess plateau. The interannual and interdecadal variations of dry/wet index are particularly obvious in this region. Up to now, the analisis of the dry/wet variation in the loess plateau has been basically understood during summer, but the autumn dry/wet evolution of the loess plateau and the atmospheric circulation characteristic are still laking in its knowledge. Based on the monthly mean rainfall and temperature of 589 China weather stations, the NCEP/NCAR reanalysis dataset and NOAA extended reconstructed sea surface temperature (SST) data from 1961 to 2010, using the EOF/REOF, bandpass filtering, wavelet technique and regression methods, the autumn dry/wet evolution of the loess plateau and the atmospheric circulation characteristic associated with them, and the multi-scale relationship between dry/wet index and SST were analyzed on the basis of classification of dry/wet over China region in autumn. The continuous wavelet transform shows that the autumn wet/dry index exists has∼4 a and 8 a period over the loess plateau, and the∼8 year oscillation from 1970-1990 is rather obvious. On the interannual scales, the atmospheric circulation anomalies of 500 hPa associated with the wet years exhibit a‘double-blocking’ in the mid-high latitude, and the westerly jet stream turns to be weakened and the jet axis moves to the north significantly. Japan-Okhotsk Sea is featured with anticyclone, and the east wind at the bottom of the anticyclone provides favorable moisture for the middle Loess plateau. On the interdecadal scales, the atmospheric circulation anomalies associated with the wet years show the negative geopotential height anomaly over East Asian, and the East Asian subtropical westerly jet stream of 200 hPa is weakened and moves north too. The vapour of the middle Loess plateau comes from two paths, one is the westerly water vapor transport in the middle latitude

  4. Combinations of large-scale circulation anomalies conducive to precipitation extremes in the Czech Republic

    Czech Academy of Sciences Publication Activity Database

    Kašpar, Marek; Müller, Miloslav

    2014-01-01

    Roč. 138, March 2014 (2014), s. 205-212. ISSN 0169-8095 R&D Projects: GA ČR(CZ) GAP209/11/1990 Institutional support: RVO:68378289 Keywords : precipitation extreme * synoptic-scale cause * re-analysis * circulation anomaly Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 2.844, year: 2014 http://www.sciencedirect.com/science/article/pii/S0169809513003372

  5. 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.

  6. 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...

  7. Atmospheric Circulation of Brown Dwarfs: Jets, Vortices, and Time Variability

    CERN Document Server

    Zhang, Xi

    2014-01-01

    A variety of observational evidence demonstrates that brown dwarfs exhibit active atmospheric circulations. In this study we use a shallow-water model to investigate the global atmospheric dynamics in the stratified layer overlying the convective zone on these rapidly rotating objects. We show that the existence and properties of the atmospheric circulation crucially depend on key parameters including the energy injection rate and radiative timescale. Under conditions of strong internal heat flux and weak radiative dissipation, a banded flow pattern comprising east-west jet streams spontaneously emerges from the interaction of atmospheric turbulence with the planetary rotation. In contrast, when the internal heat flux is weak and/or radiative dissipation is strong, turbulence injected into the atmosphere damps before it can self-organize into jets, leading to a flow dominated by isotropic turbulence and vortices instead. Based on the location of the transition, we suggest that many brown dwarfs may exhibit at...

  8. Development of newly designed VHF interferometer system for observing earthquake-related atmospheric anomalies

    OpenAIRE

    YAMAMOTO, Isao; Fujiwara, Hironobu; Kamogawa, Masashi; Iyono, Atsushi; Kroumov, Valeri; Azakami, Takashi

    2009-01-01

    Temporal correlation between atmospheric anomalies and earthquakes has recently been verified statistically through measuring VHF FM radio waves transmitted beyond the line-of-sight. In order to locate the sources of such atmospheric anomalies, we developed a VHF interferometer system (bistatic-radar type) capable of finding the arrival direction of FM radio waves scattered possibly by earthquake-related atmospheric anomalies. In general, frequency modulation of FM radio waves produces ambigu...

  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. Isotopic composition of precipitation during different atmospheric circulation patterns

    Science.gov (United States)

    Brenčič, Mihael; Kononova, Nina; Vreča, Polona

    2016-04-01

    Precipitation generating processes depend on atmospheric circulation patterns and consequently it is expected that its water stable isotopic composition of hydrogen and oxygen is related to them. Precipitation generated at similar atmospheric circulation patterns should have similar empirical distribution of δ2H and δ18O values. There are several approaches in which atmospheric circulation patterns are classified as elementary air circulation mechanisms - ECM; in our approach we have applied Dzerdzeevskii classification. Two types of models of relation between ECM and isotopic composition of precipitation are proposed; first is based on the linear combination of δ2H and δ18O values with precipitation amount weighted average (Brenčič et al., 2015) and the second new one is based on the multiple regression approach. Both approaches make possible also to estimate empirical distributions' dispersion parameters. Application of the models is illustrated on the precipitation records from Ljubljana and Portorož GNIP stations, Slovenia. Estimated values of the parameters for empirical distributions of δ2H and δ18O of each ECM subtype have shown that calculated estimates are reasonable. Brenčič, M., Kononova, N.K., Vreča, P., 2015: Relation between isotopic composition of precipitation and atmospheric circulation patterns. Journal of Hydrology 529, 1422-1432: doi: 10.1016/j.jhydrol.2015.08.040

  11. Relation between isotopic composition of precipitation and atmospheric circulation patterns

    Science.gov (United States)

    Brenčič, Mihael; Kononova, Nina K.; Vreča, Polona

    2015-10-01

    Precipitation generating processes depend on atmospheric circulation patterns and consequently it is expected that its water stable isotopic composition of hydrogen and oxygen is related to them. Precipitation generated at similar atmospheric circulation patterns should have similar empirical distribution of δ2H and δ18O values. Mathematical model based on the linear combination of δ2H and δ18O values and on precipitation amount weighted average related to elementary air circulation mechanisms - ECM is proposed. The model enables estimation of average δ2H and δ18O values and their standard deviation for the precipitation generated at distinctive atmospheric circulation patterns. Approach in which atmospheric circulation patterns were classified as ECM based on the Dzerdzeevskii classification was applied. Application of the model is illustrated on the long term precipitation record from Ljubljana GNIP station Slovenia. Estimated values of the parameters for empirical distributions of δ2H and δ18O of each ECM subtype have shown that calculated estimates are reasonable. Further applications of the proposed model enable new insight into the understanding of isotopes spatial and temporal distribution in precipitation important also for better understanding of climate proxies.

  12. Decadal variability in snow depth anomaly over Eurasia and its association with all India summer monsoon rainfall and seasonal circulations

    International Nuclear Information System (INIS)

    The Historical Soviet Daily Snow Depth (HSDSD) version II data set has been used in the computation of winter and spring snow depth anomalies over west (25 deg. E to 70 deg. E, 35 deg. N to 65 deg. N) and east (70 deg. E to 160 deg. E, 35 deg. N to 65 deg. N) Eurasia. It is noticed that winter snow depth anomaly over east Eurasia is positively correlated while west Eurasia is negatively correlated with subsequent Indian summer monsoon rainfall (ISMR). The DJF snow depth anomaly shows highest and inverse correlation coefficient (CC) with ISMR over a large area of west Eurasia in a recent period of study i.e. 1975-1995. On the basis of standardised winter (mean of December, January and February) snow depth anomaly over west Eurasia, the years 1966, 1968, 1979 and 1986 are identified as high snow years and the years 1961 and 1975 as low snow years. The characteristics of seasonal monsoon circulation features have been studied in detail during contrasting years of less (more) snow depth in winter/spring seasons followed by excess (deficient) rainfall over India using National Center for Environmental Prediction (NCEP) / National Center for Atmospheric Research (NCAR) reanylised data for the period 1948-1995. The composite difference of temperature, wind, stream function and velocity potential during the years of high and low snow years at upper and lower levels have been studied in detail. The temperature at lower level shows maximum cooling up to 6 deg. C during DJF and this cooling persists up to 500hPa by 2 deg. C which gives rise to anomalous cyclonic circulation over the Caspian Sea and this may be one of the causes of the weakening of the summer monsoon circulation over Indian sub-continent. The stream function difference fields show westerly dominated over Arabian Sea at upper level in weak monsoon years. Velocity potential difference field shows complete phase reversal in the dipole structure from the deficient to excess Indian summer monsoon rainfall. (author)

  13. Structure and dynamics of decadal anomalies in the wintertime midlatitude North Pacific ocean-atmosphere system

    Science.gov (United States)

    Fang, Jiabei; Yang, Xiu-Qun

    2015-12-01

    The structure and dynamics of decadal anomalies in the wintertime midlatitude North Pacific ocean-atmosphere system are examined in this study, using the NCEP/NCAR atmospheric reanalysis, HadISST SST and Simple Ocean Data Assimilation data for 1960-2010. The midlatitude decadal anomalies associated with the Pacific Decadal Oscillation are identified, being characterized by an equivalent barotropic atmospheric low (high) pressure over a cold (warm) oceanic surface. Such a unique configuration of decadal anomalies can be maintained by an unstable ocean-atmosphere interaction mechanism in the midlatitudes, which is hypothesized as follows. Associated with a warm PDO phase, an initial midlatitude surface westerly anomaly accompanied with intensified Aleutian low tends to force a negative SST anomaly by increasing upward surface heat fluxes and driving southward Ekman current anomaly. The SST cooling tends to increase the meridional SST gradient, thus enhancing the subtropical oceanic front. As an adjustment of the atmospheric boundary layer to the enhanced oceanic front, the low-level atmospheric meridional temperature gradient and thus the low-level atmospheric baroclinicity tend to be strengthened, inducing more active transient eddy activities that increase transient eddy vorticity forcing. The vorticity forcing that dominates the total atmospheric forcing tends to produce an equivalent barotropic atmospheric low pressure north of the initial westerly anomaly, intensifying the initial anomalies of the midlatitude surface westerly and Aleutian low. Therefore, it is suggested that the midlatitude ocean-atmosphere interaction can provide a positive feedback mechanism for the development of initial anomaly, in which the oceanic front and the atmospheric transient eddy are the indispensable ingredients. Such a positive ocean-atmosphere feedback mechanism is fundamentally responsible for the observed decadal anomalies in the midlatitude North Pacific ocean-atmosphere

  14. Weird Weather Tales of Astronomical and Atmospheric Anomalies

    CERN Document Server

    Seargent, David A J

    2012-01-01

    Have you ever heard the story of the tornado that lifted a man’s wallet right from his pants pocket? What about the myth of the Min-Min light in Australia?  Do you have a story about seeing the “Green Flash” or want an explanation of the mysterious Sun Dogs? Weird Weather: Tales of Astronomical and Atmospheric Anomalies is about the strange, unusual, and inexplicable events that take place in the air and sky. These include meteors that appear inside a darkened house, ghost lights that follow lone travelers, lightning emerging from patches of fog, and much more. Many of these climatic brainteasers occur within Earth’s skies, but there are parallel curiosities on other worlds, including: lightning on Venus, methane spouts on Titan, thunderstorms twice the size of Earth on Saturn, whirlwinds and dust storms on Mars , and auroras on Jupiter! Just as atmosphere and outer space are not separated by a sharp boundary, so the subject of this book is not confined to the skies. Earth is the way it is because of...

  15. Relationship Between Atmospheric circulation and Snowpack in theWestern United States

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Jiming; Miller, Norman L.; Sorooshian, Soroosh; Gao, Xiaogang

    2004-06-02

    Snow anomalies in the western United States (U.S.) have beenwidely investigated by many researchers due to its impact on wateravailability. This study focuses on how anomalous atmospheric circulationaffects snowpack accumulation in the western U.S. using observations andoutput from the National Center for Atmospheric Research (NCAR) CommunityClimate Model version 3 (CCM3). Our results indicate that themid-latitude atmospheric circulation anomalies induced by the ElNino-Southern Oscillation (ENSO) tend to drive winter precipitationshifts, leading to an anomalous snowpack distribution in the western U.S.The warm phase of ENSO produces increased snowpack in the Southwest,while the cold phase of ENSO generates increased snowpack in theNorthwest. Temperature has a secondary impact on the anomalous snowpackdistribution during ENSO episodes. Additionally, the non-linearatmospheric dynamics-related Pacific-North American (PNA) pattern isfound to strongly affect snow anomalies in the western U.S. independentfrom ENSO. The positive phase of the PNA pattern produces coldertemperature and stronger precipitation due to the lower pressure in theregion, leading to an above normal snowpack. Conversely, the negativephase of the PNA pattern generates warmer temperature and weakerprecipitation resulting from the higher pressure, producing a below thannormal snowpack in the western U.S. In general, the NCAR-CCM3 reproducesthe observed processes. However, model biases are identified andreported. The information provided in this study strengthens ourunderstanding of climate and water supply variability in the westernU.S.

  16. 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.

  17. Atmospheric Circulation and Composition of GJ1214b

    CERN Document Server

    Menou, Kristen

    2011-01-01

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

  18. 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...

  19. Winter season variability in North American Prairie SWE distribution and atmospheric circulation

    Science.gov (United States)

    Derksen, C.; Ledrew, E.; Walker, A.; Goodison, B.

    2000-12-01

    Passive-microwave derived observations of snow cover show potential to provide synoptically sensitive hydrologically and climatologically significant information because of all-weather imaging capabilities, rapid scene revisit time, and the ability to derive quantitative estimates of snow water equivalent (SWE). In this study, 10 winter seasons (December, January, February 1988/89 to 1997/98) of five day averaged (pentad) passive-microwave derived SWE imagery are utilized to examine the seasonal snow cover characteristics of a ground-validated North American Prairie study area. Principal components analysis (PCA) is used to identify the dominant spatial patterns through time for three passive-microwave derived datasets: (1) pentad SWE, (2) pentad SWE anomalies based on the 10 season mean and standard deviation, and (3) change-in-pentad SWE (SWE) calculated by subtracting each SWE pattern from the previous. Interpretation of the component loading patterns indicates that the SWE time series is best suited for the climatological application of identifying associations between snow cover and atmospheric circulation. Two dominant patterns are identified within the SWE time series: the positive (negative) phase of principal component 1 captures a pattern of widespread SWE ablation (accumulation) in the south with accumulation (ablation) to the north. The positive (negative) phase of principal component two characterizes a meridional accumulation (ablation) zone oriented from the northwest to southeast of the study area. The National Center for Environmental Prediction (NCEP) gridded atmospheric data (500 mb geopotential height; 700 mb temperature) are investigated in conjunction with the first two SWE principal components to identify whether consistency exists in the atmospheric patterns associated, at no time lag, with these dominant SWE modes. An investigation of composite and anomaly atmospheric fields illustrates that unique and consistent atmospheric circulation

  20. 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

  1. Anomalies.

    Science.gov (United States)

    Online-Offline, 1999

    1999-01-01

    This theme issue on anomalies includes Web sites, CD-ROMs and software, videos, books, and additional resources for elementary and junior high school students. Pertinent activities are suggested, and sidebars discuss UFOs, animal anomalies, and anomalies from nature; and resources covering unexplained phenonmenas like crop circles, Easter Island,…

  2. Autoregressive logistic regression applied to atmospheric circulation patterns

    Science.gov (United States)

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

    2014-01-01

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

  3. European rain rate modulation enhanced by changes in the NAO and atmospheric circulation regimes

    Science.gov (United States)

    Pokrovsky, Oleg M.

    2009-05-01

    The aim of this study is to classify the circulation patterns in the Atlantic-European sector and to reveal linkages between anomalies in the pressure field over the North Atlantic (e.g. North Atlantic Oscillation (NAO)) and its respective circulation pattern occurrence over continents on the one hand and rain fields on the other hand. Changes in atmospheric circulation over Europe during the past 50 years were examined using both objective (modes of low-frequency variability inferred by regression analysis and objective cluster classification of circulation types—fuzzy logic) and subjective (Hess-Brezowsky classification of weather types) methods. The grid monthly geopotential (H700), wind zonal and meridional velocity components (U850 and V850) as well as the surface atmosphere pressure (SAP) and precipitation fields acquired from the NCEP/NCAR reanalysis dataset (for 1948-1998) were employed in this study. Joint regression analysis and fuzzy logic classification of these fields was a basic tool for finding major circulation regimes. The fuzzy set analysis of these fields revealed that the major circulation regimes over eastern North Atlantic and Europe were determined in summer by three vorticity poles: (1) North-western (Scandinavia), (2) Western Mediterranean and (3) Caucasian. It is worth noting that an anticyclone occurred in the western part of the North Atlantic for both seasons. The Scandinavia cyclone area explains rain rate maximums located in the 50-60° latitude European area and the lower rain rate in Southern Europe because of hot and dry African air inflow. In late fall and winter the vorticity system consists of three other poles: (1) North-western, (2) Northern Africa and (3) Northern Russia (Kara Sea). A zonal circulation type dominates in this case and more precipitation is delivered from the Atlantic. Rain rate is more uniformly distributed in the winter in various latitude belts across Europe than in summer, but more intensive precipitation

  4. The response of oxygen isotope ratios in precipitation to changes in global atmospheric circulation

    International Nuclear Information System (INIS)

    Full text: Stable isotopes of oxygen and hydrogen present in water are known to undergo fractionation at phase transitions, with heavy isotopes tending to evaporate less readily and to undergo condensation more readily than lighter isotopes. The combination of fractionation processes for a given air parcel therefore produces the known relationships between precipitation amount, surface temperature and the isotopic ratio in precipitation. An additional factor in determining the isotopic ratio is the effect of changes in vapour source region and vapour path due to changes in atmospheric circulation. In order to explore the effect of changes in circulation related to El Nino/Southern Oscillation (ENSO) events, an atmospheric general circulation model fitted with a diagnostic module to predict the stable isotopic ratios of meteoric water (both HDO and H218O) is used to investigate the effect of warm sea surface temperature (SST) anomalies on moisture transport and hence on isotopic ratios in precipitation. Observed isotopic ratios obtained from the Global Network of Isotopes in Precipitation (GNIP) are also correlated with Troup SOI values and compared with the model results. Copyright (1999) Geological Society of Australia

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

    Science.gov (United States)

    Komacek, Thaddeus D.; Showman, Adam P.

    2016-04-01

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

  6. 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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1996-02-01

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

  8. 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.

  9. 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.

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

    Science.gov (United States)

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

    2015-04-01

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

  11. 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.

  12. 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...

  13. Amplification of El Niño by cloud longwave coupling to atmospheric circulation

    Science.gov (United States)

    Raedel, Gaby; Mauritsen, Thorsten; Stevens, Bjorn; Dommenget, Dietmar; Matei, Daniela; Bellomo, Katinka; Clement, Amy

    2016-04-01

    The El Niño/Southern Oscillation(ENSO) is the dominant mode of inter-annual variability, with major impacts on social and ecological systems through its influence on extreme weather, droughts and floods. The ability to forecast El Niño, as well as anticipate how it may change with warming, requires an understanding of the underlying physical mechanisms that drive it. Among these, the role of atmospheric processes remains poorly understood. Here we present numerical experiments with an Earth system model, with and without coupling of cloud radiative effects to the circulation, suggesting that clouds enhance ENSO variability by a factor of two or more. Clouds induce heating in the mid and upper troposphere associated with enhanced high-level cloudiness over the El Niño region, and low-level clouds cool the lower troposphere in the surrounding regions. Together, these effects enhance the coupling of the atmospheric circulation to El Niño surface temperature anomalies, and thus strengthen the positive Bjerknes feedback mechanism between west Pacific zonal wind stress and sea surface temperature gradients. Behaviour consistent with the proposed mechanisms robustly represented in other global climate models and in satellite observations. The mechanism suggests that the response of ENSO amplitude to climate change will in part be determined by a balance between increasing cloud long wave feedback and a possible reduction in the area covered by upper-level clouds.

  14. Amplification of El Niño by cloud longwave coupling to atmospheric circulation

    Science.gov (United States)

    Rädel, Gaby; Mauritsen, Thorsten; Stevens, Bjorn; Dommenget, Dietmar; Matei, Daniela; Bellomo, Katinka; Clement, Amy

    2016-02-01

    The El Niño/Southern Oscillation (ENSO) is the dominant mode of inter-annual variability, with major impacts on social and ecological systems through its influence on extreme weather, droughts and floods. The ability to forecast El Niño, as well as anticipate how it may change with warming, requires an understanding of the underlying physical mechanisms that drive it. Among these, the role of atmospheric processes remains poorly understood. Here we present numerical experiments with an Earth system model, with and without coupling of cloud radiative effects to the circulation, suggesting that clouds enhance ENSO variability by a factor of two or more. Clouds induce heating in the mid and upper troposphere associated with enhanced high-level cloudiness over the El Niño region, and low-level clouds cool the lower troposphere in the surrounding regions. Together, these effects enhance the coupling of the atmospheric circulation to El Niño surface temperature anomalies, and thus strengthen the positive Bjerknes feedback mechanism between west Pacific zonal wind stress and sea surface temperature gradients. Behaviour consistent with the proposed mechanism is robustly represented in other global climate models and in satellite observations. The mechanism suggests that the response of ENSO amplitude to climate change will in part be determined by a balance between increasing cloud longwave feedback and a possible reduction in the area covered by upper-level clouds.

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

    Czech Academy of Sciences Publication Activity Database

    Cahynová, Monika; Huth, Radan

    -, - (2016). ISSN 0899-8418 Institutional support: RVO:68378289 ; RVO:67179843 Keywords : atmospheric circulation * classification * circulation type * climatic trends * Europe * COST733 Impact factor: 3.157, year: 2014 http://onlinelibrary.wiley.com/doi/10.1002/joc.4003/abstract

  16. Decadal Periodicities in a Venus Atmosphere General Circulation Model

    Science.gov (United States)

    Parish, Helen; Schubert, G.; Covey, C.; Walterscheid, R.; Grossman, A.; Lebonnois, S.

    2010-10-01

    We have modified a 3-dimensional Earth-based climate model, CAM (Community Atmosphere Model), to simulate the dynamics of Venus' atmosphere. We have removed Earth-related processes and introduced parameters appropriate for Venus. We use a simplified Newtonian cooling approximation for the radiation scheme, without seasonal or diurnal cycles or topography. We use a high resolution (1 degree in latitude and longitude) to take account of small-scale dynamical processes that might be important on Venus. Rayleigh friction is used to represent surface drag and to prevent upper boundary wave reflection. The simulations generate superrotation at cloud heights with wind velocities comparable to those found in measurements. We find a significant decadal oscillation in the zonal winds at cloud top heights and below. A vacillation cycle is seen in the cloud top mid-latitude zonal jets which wax and wane on an approximate 10 year cycle. The decadal oscillations we find may be excited by an instability near the surface, possibly a symmetric instability. Analyses of angular momentum transport show that the jets are built up by poleward transport by a meridional circulation while angular momentum is redistributed to lower latitudes primarily by transient eddies. Observations suggest that a cyclic variation similar to that found in the model might occur in the real Venus atmosphere. Observations by Mariner 10, Pioneer Venus, and Venus Express reveal variability in cloud top wind magnitudes and in the structure of Venus' cloud level mid-latitude jets with timescales of 5 to 10 years. Oscillations in CO composition and in temperature above the cloud tops also exhibit a periodicity around 10 years and changes in the atmospheric SO2 content over 40 years show a periodicity around 20 to 25 years. Venus' atmosphere must be observed over multi-year time scales and below the clouds if we are to understand its dynamics.

  17. Global atmospheric temperature anomaly monitoring with passive microwave radiometers

    Science.gov (United States)

    Spencer, Roy W.; Christy, John R.

    1990-01-01

    The potential of microwave sounding units (MSU) for augmenting the surface-based thermometer record by providing a measurement representing a significant depth of the troposphere is considered. These radiometers measure the thermal emission by molecular oxygen in the atmosphere at different spectral intervals in the oxygen absorption complex near 60 GHz. Brightness temperature variations measured by NOAA-6 and NOAA-7 MSUs during a near-two year period are analyzed and compared with monthly averaged surface air temperature data. It is demonstrated that MSUs, while of limited use for vertical profiling of the atmosphere, provide stable measurements of vertically average atmospheric temperatures, centered at a constant pressure level.

  18. Effects of the equatorial ionosphere anomaly on the interhemispheric circulation in the thermosphere

    Science.gov (United States)

    Qian, Liying; Burns, Alan G.; Wang, Wenbin; Solomon, Stanley C.; Zhang, Yongliang; Hsu, V.

    2016-03-01

    We investigate the interhemispheric circulation at the solstices, in order to understand why O/N2 is larger in the northern hemisphere winter than in the southern hemisphere winter. Our studies reveal that the equatorial ionosphere anomaly (EIA) significantly impacts the summer-to-winter wind through plasma-neutral collisional heating, which changes the summer-to-winter pressure gradient, and ion drag. Consequently, the wind is suppressed in the summer hemisphere as it encounters the EIA but accelerates after it passes the EIA in the winter hemisphere. The wind then converges due to an opposing pressure gradient driven by Joule heating in auroral regions and produces large O/N2 at subauroral latitudes. This EIA effect is stronger near the December solstice than near the June solstice because the ionospheric annual asymmetry creates greater meridional wind convergence near the December solstice, which in turn produces larger O/N2 in the northern hemisphere winter than in the southern hemisphere winter.

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

    Energy Technology Data Exchange (ETDEWEB)

    1991-10-01

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

  20. Atmospheric multidecadal variations in the North Atlantic realm: proxy data, observations, and atmospheric circulation model studies

    OpenAIRE

    Grosfeld, K.; G. Lohmann; N. Rimbu; Fraedrich, K.; F. Lunkeit

    2007-01-01

    We investigate the spatial and temporal characteristics of multidecadal climate variability in the North Atlantic realm, using observational data, proxy data and model results. The dominant pattern of multidecadal variability of SST depicts a monopolar structure in the North Atlantic during the instrumental period with cold (warm) phases during 1900–1925 and 1970–1990 (1870–1890 and 1940–1960). Two atmospheric general circulation models of different com...

  1. Physically-Derived Dynamical Cores in Atmospheric General Circulation Models

    Science.gov (United States)

    Rood, Richard B.; Lin, Shian-Kiann

    1999-01-01

    The algorithm chosen to represent the advection in atmospheric models is often used as the primary attribute to classify the model. Meteorological models are generally classified as spectral or grid point, with the term grid point implying discretization using finite differences. These traditional approaches have a number of shortcomings that render them non-physical. That is, they provide approximate solutions to the conservation equations that do not obey the fundamental laws of physics. The most commonly discussed shortcomings are overshoots and undershoots which manifest themselves most overtly in the constituent continuity equation. For this reason many climate models have special algorithms to model water vapor advection. This talk focuses on the development of an atmospheric general circulation model which uses a consistent physically-based advection algorithm in all aspects of the model formulation. The shallow-water model of Lin and Rood (QJRMS, 1997) is generalized to three dimensions and combined with the physics parameterizations of NCAR's Community Climate Model. The scientific motivation for the development is to increase the integrity of the underlying fluid dynamics so that the physics terms can be more effectively isolated, examined, and improved. The expected benefits of the new model are discussed and results from the initial integrations will be presented.

  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. Limitations When Using Proxies of Atmospheric Circulation to Infer Regional Temperature

    Science.gov (United States)

    Kelsey, E. P.; Wake, C. P.; Osterberg, E. C.; Kreutz, K. J.

    2011-12-01

    One objective of ice core paleoclimatology is to reconstruct past variability of climate parameters such as surface air temperature. Stable isotope ratios of ice cores collected from some locations can be used with confidence to reconstruct regional air temperature. Other glaciochemical records (e.g., major ions) have been used as proxies for regional atmospheric circulation patterns, including the Arctic Oscillation and Pacific-North American pattern, typically based on the strength of semi-permanent sea level pressure centers such as the Icelandic Low and Aleutian Low. The Arctic Oscillation and Pacific North American pattern are associated with regional air temperature anomalies, and consequently ice core proxies of these circulation patterns could be used to infer paleotemperature patterns. However, detailed analysis of the 20th Century Reanalysis dataset (1871-2008) for the Northern Hemisphere winter suggests that these atmospheric circulation patterns do not always result in the same regional air temperature anomalies. A principal component analysis of detrended and area-weighted winter (December-March) temperature and sea level pressure was performed, and the leading eigenmodes were compared, along with the winter mean positions of the Icelandic and Aleutian Lows. Robust results based on multiple statistical analyses were obtained only when the extreme seasonal values of these variables were examined. Although statistically significant results were obtained when looking at temperature patterns associated with specific sea level pressure patterns and the positions of the Icelandic and Aleutian Lows, more consistent relationships were found when examining sea level pressure patterns associated with the leading eigenmodes of temperature. The seasons of extreme eigenvalues of the leading temperature eigenmodes are associated with mean positions of the Icelandic and Aleutian Lows at climatologically extreme north/south and west/east locations, respectively

  4. Anomalías de circulación atmosférica en 500 y 1000 hpa asociada a la sequía producida en la Argentina durante enero de 2003 a marzo de 2004 Anomalies of the atmospheric circulation at 500 and 1000 hpa associated with the dry period in Argentina from january 2003 to march 2004

    Directory of Open Access Journals (Sweden)

    Adelia Perla Alessandro

    2008-03-01

    anomaly geopotential height fields at 500 and 1000 hPa were analyzed. In 2003, rainfall deficit was mainly associated with geopotential anomalies at 500 hPa. They show a prevailing flow from the SW, which crosses the country diagonally from 45°S approximately to 30°S. At 1000 hPa the Atlantic Subtropical Anticyclone is weakened, displaced to the north and away from the continent. The Pacific Subtropical Anticyclone is intensified and located to the east with respect to its normal position. The drought in the first quarter of 2004 is mainly due to a ridge at 500 hPa in the center north of the country. Mean temperature anomalies in the period analyzed are positive throughout the country. High temperatures in 2003 are caused by the input of a N-NE flow from the north of the country, subsidence due to the Pacific Anticyclone shift towards the continent and orography. During the first quarter of 2004 they are generated by a flow from the north and the frequent anticyclonic circulation over the Atlantic to the south of 35°S.

  5. Modelling Martian dust storms: feedbacks between dust and atmospheric circulation at a hierarchy of scales

    OpenAIRE

    Lewis, S.; Spiga, A.; Mulholland, D.

    2010-01-01

    We employ numerical models of Mars at spatial scales ranging from global to a few metres in order to investigate both the impact of increasing dust loading on atmospheric circulations and the role of different atmospheric circulation components on dust lifting, transport and on dust storm decay.

  6. Active-active and active-sterile neutrino oscillation solutions to the atmospheric neutrino anomaly

    CERN Document Server

    González-Garciá, M Concepción; Peres, O L G; Valle, José W F

    1999-01-01

    We perform a fit to the full data set corresponding to 25.5 kt-yr of data of the Super-Kamiokande experiment as well as to all other experiments in order to compare the two most likely solutions to the atmospheric neutrino anomaly in terms of oscillations in the $\

  7. Methane as a diagnostic tracer of changes in the net circulation of the middle atmosphere

    Directory of Open Access Journals (Sweden)

    E. E. Remsberg

    2014-09-01

    Full Text Available This study makes use of time series of methane (CH4 data from the Halogen Occultation Experiment (HALOE to determine whether there were any statistically significant changes of the net circulation within the stratosphere and lower mesosphere during 1992–2005. HALOE CH4 profiles in terms of mixing ratio vs. pressure-altitude are binned into subtropical and extratropical latitude zones of the southern and of the Northern Hemisphere, and their separate time series are then analyzed using multiple linear regression (MLR techniques. A positive trend in the subtropics and a negative trend in the extratropics is interpreted as indicating an acceleration of the net circulation. A significant acceleration is found in the Northern Hemisphere from 20 hPa to 7 hPa, a likely indication of changes from the effects of wave activity during those years. No similar acceleration is found in the Southern Hemisphere. The trends from HALOE H2O are analyzed and compared with those from CH4 for consistency because H2O is a primary product in the upper stratosphere of the chemical conversion of CH4. The CH4 and H2O trends have a ratio of nearly 2 : 1, and they are anti-correlated most clearly near the stratopause in the southern extratropics. Seasonal anomalies are found in the HALOE CH4 time series of the lower mesosphere, and they are ascribed to wave-driven, secondary residual circulation cells associated with the descent of the SAO westerlies. The time series residuals for CH4 of the lower mesosphere also exhibit aperiodic structure, and it is anti-correlated with that of the tracer-like species HCl. Such structure indicates the effects of variations in the wave forcing. It is concluded that multi-year, global-scale distributions of CH4 are very useful for diagnosing large-scale changes of the net transport within the middle atmosphere.

  8. Near Real Time website for IASI observations of atmospheric anomalies

    Science.gov (United States)

    Hayer, Catherine; Grainger, Don; Marsh, Kevin; Carboni, Elisa; Ventress, Lucy; Smith, Andrew

    2014-05-01

    Rapid analysis of satellite observations of the state of the atmosphere and the contaminant levels within it can be used for pollution monitoring, forest fire detection and volcanic activity monitoring. There are numerous operational satellite instruments for which this is possible. The IASI instruments, currently flying on board the MetOp-A and MetOp-B satellite platforms, are used to produce Near Real Time (NRT) data using analysis algorithms developed by Oxford University. The data is then displayed on a website within 3 hours of measurement. This allows for the semi-continuous monitoring of the state of the atmosphere over most of the globe, both in daylight and at night. Global coverage is achieved 4 times per day, which is a significant advantage over most of the alternatives, either geostationary, giving limited spatial coverage, or UV instruments which are only able to observe during the daylight side of the orbit. The website includes flags for atmospheric contaminants detectable by IASI, including dust, biomass burning-derived species and volcanic ash and SO2. In the near future, the website will be developed to also include a quantitative estimate of the mass loading of SO2 contained within any volcanic cloud. Emissions of volcanic products, such as ash and SO2, are useful indicators of a change in the activity level of a volcano. Since many volcanoes are only monitored by remote sensing methods, such as satellite instruments, this can be the only such indicator available. These emissions are also dangerous to passing aircraft, causing damage to external surfaces of the plane and to the engines, sometimes leading to failure. Evacuation of regions surrounding volcanoes, and cessation or diversion of air traffic around actively erupting volcanoes is costly and highly disruptive but is sometimes required. Up to date information is of critical importance as to when to make these sensitive decisions. An archive of data will be available to allow for easy

  9. 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

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

    Czech Academy of Sciences Publication Activity Database

    Cahynová, Monika; Huth, R.

    -, - (2016). ISSN 0899-8418 R&D Projects: GA ČR GAP209/10/2265; GA ČR(CZ) GPP209/12/P811 Institutional support: RVO:67179843 ; RVO:68378289 Keywords : atmospheric circulation * classification * circulation type * climatic trends * Europe * COST733 Subject RIV: EH - Ecology, Behaviour; DG - Athmosphere Sciences, Meteorology (UFA-U) Impact factor: 3.157, year: 2014

  11. The characteristics of local atmospheric circulation around the Wolsung NPP in Korea

    International Nuclear Information System (INIS)

    The transport of air pollutants in coastal regions has been known to be strongly affected by the mesoscale atmospheric circulations such as sea-land breezes. These mesoscale atmospheric circulations depend on synoptic weather conditions. In this study, a three-dimensional sea-land breeze model was developed to evaluate the effects of the sea and land breezes on the atmospheric dispersion of radioactive materials released from nuclear power plants in Korea. In the model, the hydrostatic primitive equations in the terrain-following coordinate system were used. The mesoscale atmospheric circulation simulation were carried out under various synoptic weather conditions for all seasons around the Wolsung nuclear power plant site

  12. 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.

  13. Decadal variability in snow depth anomaly over Eurasia and its association with all India summer monsoon rainfall and seasonal circulations

    CERN Document Server

    Singh, G P

    2003-01-01

    The Historical Soviet Daily Snow Depth (HSDSD) version II data set has been used in the computation of winter and spring snow depth anomalies over west (25 deg. E to 70 deg. E, 35 deg. N to 65 deg. N) and east (70 deg. E to 160 deg. E, 35 deg. N to 65 deg. N) Eurasia. It is noticed that winter snow depth anomaly over east Eurasia is positively correlated while west Eurasia is negatively correlated with subsequent Indian summer monsoon rainfall (ISMR). The DJF snow depth anomaly shows highest and inverse correlation coefficient (CC) with ISMR over a large area of west Eurasia in a recent period of study i.e. 1975-1995. On the basis of standardised winter (mean of December, January and February) snow depth anomaly over west Eurasia, the years 1966, 1968, 1979 and 1986 are identified as high snow years and the years 1961 and 1975 as low snow years. The characteristics of seasonal monsoon circulation features have been studied in detail during contrasting years of less (more) snow depth in winter/spring seasons f...

  14. 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

  15. Summertime land-sea thermal contrast and atmospheric circulation over East Asia in a warming climate—Part I: Past changes and future projections

    Science.gov (United States)

    Kamae, Youichi; Watanabe, Masahiro; Kimoto, Masahide; Shiogama, Hideo

    2014-11-01

    Land-sea surface air temperature (SAT) contrast, an index of tropospheric thermodynamic structure and dynamical circulation, has shown a significant increase in recent decades over East Asia during the boreal summer. In Part I of this two-part paper, observational data and the results of transient warming experiments conducted using coupled atmosphere-ocean general circulation models (GCMs) are analyzed to examine changes in land-sea thermal contrast and the associated atmospheric circulation over East Asia from the past to the future. The interannual variability of the land-sea SAT contrast over the Far East for 1950-2012 was found to be tightly coupled with a characteristic tripolar pattern of tropospheric circulation over East Asia, which manifests as anticyclonic anomalies over the Okhotsk Sea and around the Philippines, and a cyclonic anomaly over Japan during a positive phase, and vice versa. In response to CO2 increase, the cold northeasterly winds off the east coast of northern Japan and the East Asian rainband were strengthened with the circulation pattern well projected on the observed interannual variability. These results are commonly found in GCMs regardless of future forcing scenarios, indicating the robustness of the East Asian climate response to global warming. The physical mechanisms responsible for the increase of the land-sea contrast are examined in Part II.

  16. Longitudinal biases in the Seychelles Dome simulated by 35 ocean-atmosphere coupled general circulation models

    Science.gov (United States)

    Nagura, Motoki; Sasaki, Wataru; Tozuka, Tomoki; Luo, Jing-Jia; Behera, Swadhin K.; Yamagata, Toshio

    2013-02-01

    Seychelles Dome refers to the shallow climatological thermocline in the southwestern Indian Ocean, where ocean wave dynamics efficiently affect sea surface temperature, allowing sea surface temperature anomalies to be predicted up to 1-2 years in advance. Accurate reproduction of the dome by ocean-atmosphere coupled general circulation models (CGCMs) is essential for successful seasonal predictions in the Indian Ocean. This study examines the Seychelles Dome as simulated by 35 CGCMs, including models used in phase five of the Coupled Model Intercomparison Project (CMIP5). Among the 35 CGCMs, 14 models erroneously produce an upwelling dome in the eastern half of the basin whereas the observed Seychelles Dome is located in the southwestern tropical Indian Ocean. The annual mean Ekman pumping velocity in these models is found to be almost zero in the southern off-equatorial region. This result is inconsistent with observations, in which Ekman upwelling acts as the main cause of the Seychelles Dome. In the models reproducing an eastward-displaced dome, easterly biases are prominent along the equator in boreal summer and fall, which result in shallow thermocline biases along the Java and Sumatra coasts via Kelvin wave dynamics and a spurious upwelling dome in the region. Compared to the CMIP3 models, the CMIP5 models are even worse in simulating the dome longitudes.

  17. How Large is the Mass Independent O-17 Anomaly in the Atmosphere?

    Science.gov (United States)

    Luz, B.; Angert, A.; Barkan, E.; Bender, M. L.

    2002-12-01

    The isotopic composition of atmospheric oxygen is controlled by biological mechanisms, the hydrological cycle and stratospheric photochemistry. The biological mechanisms include photosynthetic oxygen production of identical isotopic composition as the substrate water and oxygen uptake by various mechanisms with mass dependent fractionation. Fractionation in the hydrological cycle is also mass dependent. In contrast, stratospheric photochemistry also removes oxygen, but fractionates the isotopic composition of the remaining gas in a mass-independent way. As a result atmospheric oxygen becomes anomalous (O-17 depleted) with respect to oxygen of the global atmosphere that would have been produced in the absence of stratospheric photochemistry. For estimating the magnitude of this anomaly, it is necessary to know the triple isotope fractionations of the relevant global processes. In the present research we carried out experiments in order to determine the ratio between the discriminations against O-17 and O-18 in dark respiration and in photorespiration. The obtained values are 0.518 and 0.506 respectively, and are different than in meteoric water fractionation (0.525). Assuming that the latter value applies to leaf-water (the substrate of all terrestrial photosynthesis), we estimate the magnitude of the anomaly as 258 permeg. This figure is significantly larger than 117 permeg estimated from stratospheric mass balance. Alternatively, by talking the 117 permeg value as representative of the anomaly, we calculate the ratio between the discriminations against O-17 and O-18 in leaf water as 0.511. Clearly, if we are to correctly estimate the atmospheric anomaly, careful determination of the triple isotope composition of global leaf-water is a prerequisite.

  18. Interannual Variability of Heat Wave in South Korea and theirs Connection with Large-Scale Atmospheric Circulation Pattern

    Science.gov (United States)

    Lee, Woo-Seop; Lee, Myong-In

    2016-04-01

    This study investigates the interannual variation of heat wave frequency (HWF) in South Korea during the past 42 years (1973-2014) and examines its connection with large-scale atmospheric circulation changes. Korean heat waves tend to develop most frequently in late summer during July and August. The leading Empirical Orthogonal Function (EOF) accounting for 50% of the total variance shows a mono-signed pattern over South Korea, suggesting that the dominant mechanisms responsible for the heat wave are linked in a spatial scale much larger than the nation. It also exhibits a regional variation with more occurrences in the southeastern inland area. The regression of the leading principal component (PC) time series of HWF with large-scale atmospheric circulation identifies a north-south dipole pattern between the South China Sea and Northeast Asia. When this large-scale circulation mode facilitates deep convection in South China Sea, it tends to weaken moisture transport from the South China Sea to Northeast Asia. Enhanced deep convection in the South China Sea triggers a source of Rossby wave train along southerly wind that generates positive geopotential height anomalies around Korea. The anomalous high pressure pattern is accompanied by large-scale subsidence in Korea, thereby providing a favorable condition for extreme hot and dry days in Korea. This study highlights that there is a decadal change of the relationship between Korean heat waves and large-scale atmospheric circulation patterns. The tropical forcing tends to be weakened in the recent decade, with more influences from the Arctic variability from the mid-1990s.

  19. Daily atmospheric circulation indices and types in European regions since the mid-19th century

    Czech Academy of Sciences Publication Activity Database

    Cahynová, Monika

    Washington: Association of American Geographers, 2014. [AAG Annual Meeting /59./. 08.04.2014-12.04.2014, Tampa] Institutional support: RVO:68378289 Keywords : atmospheric circulation * classification * circulation types,trends,reanalysis,Europe * trends * reanalysis * Europe Subject RIV: DG - Athmosphere Sciences, Meteorology http://meridian.aag.org/callforpapers/program/AbstractDetail.cfm?AbstractID=58707

  20. Large scale atmospheric tropical circulation changes and consequences during global warming

    International Nuclear Information System (INIS)

    The changes of the tropical large scale circulation during climate change can have large impacts on human activities. In a first part, the meridional atmospheric tropical circulation was studied in the different coupled models. During climate change, we find, on the one hand, that the Hadley meridional circulation and the subtropical jet are significantly shifted poleward, and on the other hand, that the intensity of the tropical circulation weakens. The slow down of the atmospheric circulation results from the dry static stability changes affecting the tropical troposphere. Secondly, idealized simulations are used to explain the tropical circulation changes. Ensemble simulation using the model LMDZ4 are set up to study the results from the coupled model IPSLCM4. The weakening of the large scale tropical circulation and the poleward shift of the Hadley cells are explained by both the uniform change and the meridional gradient change of the sea surface temperature. Then, we used the atmospheric model LMDZ4 in an aqua-planet configuration. The Hadley circulation changes are explained in a simple framework by the required poleward energy transport. In a last part, we focus on the water vapor distribution and feedback in the climate models. The Hadley circulation changes were shown to have a significant impact on the water vapour feedback during climate change. (author)

  1. Recent Northern Hemisphere stratospheric HCl increase due to atmospheric circulation changes.

    Science.gov (United States)

    Mahieu, E; Chipperfield, M P; Notholt, J; Reddmann, T; Anderson, J; Bernath, P F; Blumenstock, T; Coffey, M T; Dhomse, S S; Feng, W; Franco, B; Froidevaux, L; Griffith, D W T; Hannigan, J W; Hase, F; Hossaini, R; Jones, N B; Morino, I; Murata, I; Nakajima, H; Palm, M; Paton-Walsh, C; Russell, J M; Schneider, M; Servais, C; Smale, D; Walker, K A

    2014-11-01

    The abundance of chlorine in the Earth's atmosphere increased considerably during the 1970s to 1990s, following large emissions of anthropogenic long-lived chlorine-containing source gases, notably the chlorofluorocarbons. The chemical inertness of chlorofluorocarbons allows their transport and mixing throughout the troposphere on a global scale, before they reach the stratosphere where they release chlorine atoms that cause ozone depletion. The large ozone loss over Antarctica was the key observation that stimulated the definition and signing in 1987 of the Montreal Protocol, an international treaty establishing a schedule to reduce the production of the major chlorine- and bromine-containing halocarbons. Owing to its implementation, the near-surface total chlorine concentration showed a maximum in 1993, followed by a decrease of half a per cent to one per cent per year, in line with expectations. Remote-sensing data have revealed a peak in stratospheric chlorine after 1996, then a decrease of close to one per cent per year, in agreement with the surface observations of the chlorine source gases and model calculations. Here we present ground-based and satellite data that show a recent and significant increase, at the 2σ level, in hydrogen chloride (HCl), the main stratospheric chlorine reservoir, starting around 2007 in the lower stratosphere of the Northern Hemisphere, in contrast with the ongoing monotonic decrease of near-surface source gases. Using model simulations, we attribute this trend anomaly to a slowdown in the Northern Hemisphere atmospheric circulation, occurring over several consecutive years, transporting more aged air to the lower stratosphere, and characterized by a larger relative conversion of source gases to HCl. This short-term dynamical variability will also affect other stratospheric tracers and needs to be accounted for when studying the evolution of the stratospheric ozone layer. PMID:25373680

  2. Influence of the North Atlantic SST Variability on the Atmospheric Circulation during the Twentieth Century

    OpenAIRE

    Gastineau, Guillaume; Frankignoul, Claude

    2015-01-01

    International audience The ocean–atmosphere coupling in the North Atlantic is investigated during the twentieth century using maximum covariance analysis of sea surface temperature (SST) and 500-hPa geopotential height analyses and performing regressions on dynamical diagnostics such as Eady growth rate, wave activity flux, and velocity potential. The North Atlantic Oscillation (NAO) generates the so-called SST anomaly tripole. A rather similar SST anomaly tripole, with the subpolar anomal...

  3. 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....

  4. Atmospheric circulation patterns associated with strong wind events in Catalonia

    Science.gov (United States)

    Aran, M.; Peña, J. C.; Amaro, J.

    2009-09-01

    Although the advance of powerful computers has improved the outputs of meteorological models, a good synoptic classification (SC) can be very useful for long-range forecasting. In this way, the Servei Meteorològic de Catalunya (SMC) is working on elaborating an accurate SC for extreme events. Catalonia is a region affected by high impact weather, mainly strong wind (SW) and heavy rain events. Not far from now, this last winter happened one of the worst wind events with high social impact. Within the framework of MEDEX project SMC has been collaborating in improving the knowledge of these events. Following this line of work, the aim of this study is to characterise the SW events in Catalonia. According to the guidelines of MEDEX project we have used its strong wind event database for the period June 1995 to May 2004. The used methodology is based on principal component analysis (PCA) and clustering techniques. In this study it was applied the PCA technique based on S-mode for SLP, temperature 850 hPa and geopotential 500 hPa. The semi-objective classification was carried out using the NCEP-NCAR reanalysis. Furthermore, a wind velocity matrix was also used to take into account some mesoscale aspects. These data were obtained from the automatic weather stations of SMC network. Then, cluster analysis was applied to the component scores to obtain the atmospheric patterns. At the end, a discriminant analysis was applied to the clusters to improve the classification and to evaluate its goodness. This methodology was applied to two geographical domains: the MEDEX domain (30N-48N; 9W-15E) and a synoptic domain (30N-70N; 30W-20E). The obtained results showed that the small domain was not enough suitable to discern the main low and high centres. On the other hand, the synoptic domain resolved better the main situation for each season. The results obtained working with the synoptic domain show seven patterns. The strongest event is related to the Alps cyclogenesis and an

  5. The Atmospheric Circulation of the Super Earth GJ 1214b: Dependence on Composition and Metallicity

    Science.gov (United States)

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

    2014-04-01

    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 (MMW; i.e., H2-dominated) and a high MMW (i.e., water- and CO2-dominated). We find that atmospheres with a low MMW 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 MMW have larger day-night and equator-to-pole temperature variations than low MMW atmospheres, but differences in opacity structure and energy budget lead to differences in jet structure. The circulation of a water-dominated atmosphere is dominated by equatorial superrotation, while the circulation of a CO2-dominated atmosphere is instead dominated by high-latitude jets. By comparing emergent flux spectra and light curves for 50× solar and water-dominated compositions, we show that observations in emission can break the degeneracy in determining the atmospheric composition of GJ 1214b. The variation in opacity with wavelength for the water-dominated atmosphere leads to large phase variations within water bands and small phase variations outside of water bands. The 50× solar atmosphere, however, yields small variations within water bands and large phase variations at other characteristic wavelengths. These observations would be much less sensitive to clouds, condensates, and hazes than transit observations.

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

    Energy Technology Data Exchange (ETDEWEB)

    Kataria, T.; Showman, A. P. [Department of Planetary Sciences and Lunar and Planetary Laboratory, The University of Arizona, Tucson, AZ 85721 (United States); Fortney, J. J. [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Marley, M. S.; Freedman, R. S., E-mail: tkataria@lpl.arizona.edu [NASA Ames Research Center 245-3, Moffett Field, CA 94035 (United States)

    2014-04-20

    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 (MMW; i.e., H{sub 2}-dominated) and a high MMW (i.e., water- and CO{sub 2}-dominated). We find that atmospheres with a low MMW 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 MMW have larger day-night and equator-to-pole temperature variations than low MMW atmospheres, but differences in opacity structure and energy budget lead to differences in jet structure. The circulation of a water-dominated atmosphere is dominated by equatorial superrotation, while the circulation of a CO{sub 2}-dominated atmosphere is instead dominated by high-latitude jets. By comparing emergent flux spectra and light curves for 50× solar and water-dominated compositions, we show that observations in emission can break the degeneracy in determining the atmospheric composition of GJ 1214b. The variation in opacity with wavelength for the water-dominated atmosphere leads to large phase variations within water bands and small phase variations outside of water bands. The 50× solar atmosphere, however, yields small variations within water bands and large phase variations at other characteristic wavelengths. These observations would be much less sensitive to clouds, condensates, and hazes than transit observations.

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

    International Nuclear Information System (INIS)

    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 (MMW; i.e., H2-dominated) and a high MMW (i.e., water- and CO2-dominated). We find that atmospheres with a low MMW 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 MMW have larger day-night and equator-to-pole temperature variations than low MMW atmospheres, but differences in opacity structure and energy budget lead to differences in jet structure. The circulation of a water-dominated atmosphere is dominated by equatorial superrotation, while the circulation of a CO2-dominated atmosphere is instead dominated by high-latitude jets. By comparing emergent flux spectra and light curves for 50× solar and water-dominated compositions, we show that observations in emission can break the degeneracy in determining the atmospheric composition of GJ 1214b. The variation in opacity with wavelength for the water-dominated atmosphere leads to large phase variations within water bands and small phase variations outside of water bands. The 50× solar atmosphere, however, yields small variations within water bands and large phase variations at other characteristic wavelengths. These observations would be much less sensitive to clouds, condensates, and hazes than transit observations.

  8. Analysis of tropical sea surface temperature and atmospheric circulation anomalies and their relationship with abnormal precipitation in Yunnan during rainy season%云南雨季降水异常的热带海温和大气环流异常分析

    Institute of Scientific and Technical Information of China (English)

    谭晶; 王彰贵; 黄荣辉; 陈幸荣; 蔡怡; 黄勇勇

    2015-01-01

    Based on seven stations’ monthly precipitation data in Yunnan and the NCEP/NCAR monthly atmospheric circulation data, as well as ERSST V3b monthly sea surface temperature (SST) data, the Indian-Pacific SST mode that impacts Yunnan precipitation during rainy season was investigated using composite and correlation analysis. Of El Niño-Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) mode, which plays a more important role on Yunnan precipitation in rainy season? Finally, the physical mechanism through which Indian-Pacific SST mode impacts Yunnan precipitation in rainy season was discussed. The results are as follows. Both ENSO and IOD have influences on Yunnan precipitation in rainy season, but the IOD plays a more important role. When the western India Ocean’s SST is warmer (positive IOD), the easterly wind appears in the tropical Indian Ocean and a cyclonic anomalous circulation is in the western Indian Ocean. The warm and moist airflow in the western Indian Ocean enters the Mainland China along the west side of the Tibet Plateau, then goes around the Tibet Plateau and from the north to the south, and finally enters the Bay of Bengal, which limits the development of the trough over the Bay of Bengal. So, the water vapor transportation to Yunnan is less. Yunnan is in the water vapor flux divergence area and has less precipitation. When the tropical Indian Ocean has lower SST (negative IOD), no easterly wind is in the tropical Indian Ocean, the trough over the Bay of Bengal is strong, and the water vapor transportation to Yunnan is more; Yunnan is in the water vapor flux convergence area and has more precipitation.%利用云南地区32个站日降水量资料、NCEP/NCAR月平均大气环流资料和ERSST V3b的海表温度资料,利用合成分析、相关分析等方法,研究了影响云南雨季降水的太平洋-印度洋海温分布模态,并讨论了 ENSO 和热带印度洋偶极子(IOD)对云南雨季降水多寡影响的相对重要性

  9. Response of the Adriatic Sea to the atmospheric anomaly in 2003

    Directory of Open Access Journals (Sweden)

    B. Grbec

    2007-05-01

    Full Text Available Unusual weather conditions over the southern Europe and the Mediterranean area in 2003 significantly impacted the oceanographic properties of the Adriatic Sea. To document these changes, both in the atmosphere and the sea, anomalies from the normal climate were calculated. The winter 2003 was extremely cold, whereas the spring/summer period was extremely warm. The air temperature in June was more than 3 standard deviations above the average. On the other hand, precipitation and river runoff were extremely low between February and August. The response of the sea was remarkable, especially in surface salinity during spring and summer, with values at least one standard deviation above the average. Analysis of thermohaline properties in the middle Adriatic showed the importance of two phenomena responsible for the occurrence of exceptionally high salinity: (1 enhanced inflow of saline Levantine Intermediate Water (LIW in the Adriatic, and (2 extremely low precipitation and river runoff, accompanied with strong evaporation. Two large-scale atmospheric indices: NAOI (North Atlantic Oscillation Index and MOI (Mediterranean Oscillation Index, although generally correlated to the Adriatic climate, failed to describe anomalies in 2003. The air pressure gradients used for the definition of both indices significantly decreased in 2003 due to the presence of the high pressure areas over most of Europe and the northern Atlantic, and were actually responsible for the observed anomalies above and in the Adriatic.

  10. Sea surface height anomaly and geostrophic circulation variations in the South China Sea from TOPEX/POSEIDON altimetry

    Institute of Scientific and Technical Information of China (English)

    刘克修; 马继瑞; 许建平; 韩桂军; 范振华

    2002-01-01

    --The sea surface height anomaly (SSHA) and geostrophic circulation in the South ChinaSea (SCS) are studied using TOPEX/POSEIDON (T/P) altimetry data. The SSHA, which is obtained after tidal correction based on the tidal results from T/P data, is predominated by seasonal alternating monsoons. The results reveal that the SSHA in the central part of the SCS is positive in spring and summer, but negative in autumn and winter. It is also found that the SSHA in the SCS can be approached with the sum of tidal constituents SA and SSA. The geostrophic circulations in the SCS are calculated according to sea surface dynamic topography, which is the sum of SSHA and mean sea surface height. It is suggested that the circulation in the upper layer of the SCS is generally cyclonic and notably western intensified during autumn and winter, while the western intensification is weak during spring and summer. It is also indicated that the Kuroshio intrudes into the northeastern SCS throuth the Luzon Strait in winter. But there is no indication of Kuroshio intruding into the SCS in summer.

  11. Variations in Regional Mean Daily Precipitation Extremes and Related Circulation Anomalies over Central China During Boreal Summer

    Institute of Scientific and Technical Information of China (English)

    柯丹; 管兆勇

    2014-01-01

    The variations of regional mean daily precipitation extreme (RMDPE) events in central China and associated circulation anomalies during June, July, and August (JJA) of 1961-2010 are investigated by using daily in-situ precipitation observations and the NCEP/NCAR reanalysis data. The precipitation data were collected at 239 state-level stations distributed throughout the provinces of Henan, Hubei, and Hunan. During 1961-2010, the 99th percentile threshold for RMDPE is 23.585 mm day-1. The number of RMDPE events varies on both interannual and interdecadal timescales, and increases significantly after the mid 1980s. The RMDPE events happen most frequently between late June and mid July, and are generally associated with anomalous baroclinic tropospheric circulations. The supply of moisture to the southern part of central China comes in a stepping way from the outer-region of an abnormal anticyclone over the Bay of Bengal and the South China Sea. Fluxes of wave activity generated over the northeastern Tibetan Plateau converge over central China, which favors the genesis and maintenance of wave disturbances over the region. RMDPE events typically occur in tandem with a strong heating gradient formed by net heating in central China and the large-scale net cooling in the surrounding area. The occurrence of RMDPE events over central China is tied to anomalous local cyclonic circulations, topographic forcing over the northeast Tibetan Plateau, and anomalous gradients of diabatic heating between central China and the surrounding areas.

  12. On the characteristics of atmospheric circulation associated with snowfall in NW Greece

    Science.gov (United States)

    Houssos, E. E.; Lolis, C. J.; Bartzokas, A.

    2009-09-01

    In this work the main atmospheric circulation types, associated with snowfall events in NW Greece, are examined. Also, a validation procedure is followed in order to investigate to what extent the circulation types revealed are related with snowfall in NW Greece. For this purpose, two datasets are used. The first one consists of 6-hourly values of mean sea level pressure, temperature at 850hPa level and 500hPa height in 273 grid-points covering Europe and the Mediterranean, for the 45-year period 1/9/1957 to 31/8/2002. The second one comprises all the 6-hourly observations at the meteorological station of Ioannina (NW Greece). From the first dataset and for each meteorological parameter a data matrix is constructed consisting of 65,744 rows and 273 columns. Each column represents the time series of the parameter at each grid point and each row represents the space series (map) of the parameter at the time of each observation (4 observations per day for the 45-year period). Then, a new matrix is created by merging the matrices of MSL pressure, T-850hPa and Z-500hPa in a united matrix of 65,744 rows x 819 columns. In this way, each row represents the 3-dimensional structure of the atmosphere (based on the 3 parameters used) at the time of each observation. Next, Factor Analysis is applied on this united matrix in order to reduce the dimensionality of the data set. The 819 columns are reduced to 8 (uncorrelated Factors), describing satisfactorily the 3-dimensional structure of the atmosphere, as they explain approximately 86% of the total variance. From the second data set the observations reporting snowfall in Ioannina are found out and then a new data matrix is constructed consisting of the Factor scores rows corresponding to these observations only. In the new matrix (235 rows x 8 columns) each row describes the structure of the atmosphere over Europe and the Mediterranean in the cases of snowfall in Ioannina. Cluster Analysis (K-Means) is applied in this final

  13. On the differences between early and middle winter atmospheric responses to sea surface temperature anomalies in the northwest Atlantic

    International Nuclear Information System (INIS)

    Using an atmospheric global spectral model at RPN with T42 horizontal resolution, we have shown that the winter atmosphere in the mid-latitude is capable of reacting to the SST anomalies prescribed in the northwest Atlantic with two different responses. The nature of the response is determined by the climatological conditions of the winter system. Experiments are conducted using either the perpetual November or January conditions, with or without the SST anomalies prescribed. Six 50-day integrations, with positive (or negative) SST anomalies prescribed, initialized from independent November analyses and similarly, four runs initialized from January analyses, have been examined in comparison with their control runs

  14. A zonally symmetric model for volcanic influence upon atmospheric circulation

    Science.gov (United States)

    Schatten, K. H.; Mayr, H. G.; Harris, I.; Taylor, H. A., Jr.

    1984-01-01

    The effects of volcanic activity upon zonal wind flow in a model atmosphere are considered. A low latitude volcanic eruption could lower the tropospheric pole to equator temperature difference and thereby affect the atmospheric motions. When the temperature contrast decreases, the zonal wind velocities at high altitudes are reduced. To conserve angular momentum, the velocities in the lower atmosphere near the surface must increase, thus providing a momentum source for ocean currents. It is suggested that this momentum source may have played a role as a trigger for inducing the 1982-83 anomalous El Nino and possibly other climate changes.

  15. 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.

  16. Electron Density and Temperature Measurements, and Abundance Anomalies in the Solar Atmosphere

    Indian Academy of Sciences (India)

    Anita Mohan; Bhola N. Dwivedi; Enrico Landi

    2000-09-01

    Using spectra obtained from the SUMER (Solar Ultraviolet Measurements of Emitted Radiation) spectrograph on the spacecraft SOHO (Solar and Heliospheric Observatory), we investigate the height dependence of electron density, temperature and abundance anomalies in the solar atmosphere. In particular, we present the behaviour of the solar FIP effect (the abundance enhancement of elements with first ionization potential < 10 eV in the corona with respect to photospheric values) with height above an active region observed at the solar limb, with emphasis on the so-called transition region lines.

  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. 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)

  19. The effects of North Atlantic SST and sea ice anomalies on the winter circulation in CCM3. Part II: Direct and indirect components of the response

    OpenAIRE

    Deser, C.; Magnusdottir, G.; Saravanan, R.; Phillips, A.

    2004-01-01

    The wintertime atmospheric circulation responses to observed patterns of North Atlantic sea surface temperature and sea ice cover trends in recent decades are studied by means of experiments with an atmospheric general circulation model. Here the relationship between the forced responses and the dominant pattern of internally generated atmospheric variability is focused on. The total response is partioned into a portion that projects onto the leading mode of internal variability (the indirect...

  20. Impacts of SST and SST Anomalies on Low-Frequency Oscillation in the Tropical Atmosphere

    Institute of Scientific and Technical Information of China (English)

    HE Jinhai; YU Jingjing; SHEN Xinyong

    2007-01-01

    Considering the multiscale character of LFO (low-frequency oscillation) in the tropical atmosphere, the effects of SST on LFO in the tropical atmosphere are discussed by using an absolute ageostrophic, baroclinic model. Here, SST effects include sea surface heating and forcing of SST anomalies (SSTAs). Studies of the influences of sea surface heating on LFO frequency and stability show that sea surface heating can slow the speed of waves and lower their frequency when SST is comparatively low; while higher SST leads to unstable waves and less periods of LFO. Since the impact of a SSTA on ultra-long waves is more evident than that on kilometer-scale waves, long-wave approximation is used when we continue to study the effect of SSTAs. Results indicate that SSTAs can lead to a longer period of LFO, and make waves unstable. In other words,positive (negative) SSTAs can make waves decay (grow).

  1. Strong Water Isotopic Anomalies in the Martian Atmosphere: Probing Current and Ancient Reservoirs

    Science.gov (United States)

    Villanueva, G. L.; Mumma, M. J.; Novak, R. E.; Käufl, H. U.; Hartogh, P.; Encrenaz, T.; Tokunaga, A.; Khayat, A.; Smith, M. D.

    2015-01-01

    We measured maps of atmospheric water (H2O) and its deuterated form (HDO) across the martian globe, showing strong isotopic anomalies and a significant high deuterium/hydrogen (D/H) enrichment indicative of great water loss. The maps sample the evolution of sublimation from the north polar cap, revealing that the released water has a representative D/H value enriched by a factor of about 7 relative to Earth's ocean [Vienna standard mean ocean water (VSMOW)]. Certain basins and orographic depressions show even higher enrichment, whereas high-altitude regions show much lower values (1 to 3 VSMOW). Our atmospheric maps indicate that water ice in the polar reservoirs is enriched in deuterium to at least 8 VSMOW, which would mean that early Mars (4.5 billion years ago) had a global equivalent water layer at least 137 meters deep.

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

    NARCIS (Netherlands)

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

    2012-01-01

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

  3. The atmospheric circulation and dust activity in different orbital epochs on Mars

    OpenAIRE

    Newman, Claire E.; Lewis, Stephen R.; Read, Peter L.

    2005-01-01

    A general circulation model is used to evaluate changes to the circulation and dust transport in the martian atmosphere for a range of past orbital conditions. A dust transport scheme, including parameterized dust lifting, is incorporated within the model to enable passive or radiatively active dust transport. The focus is on changes which relate to surface features, as these may potentially be verified by observations. Obliquity variations have the largest impact, as they affect the latitudi...

  4. Could circulation anomalies cause the strong water deficit of Lake Balaton in 2000-2003?

    Science.gov (United States)

    Mika, János; Varga, György; Pálfy, László; Bonta, Imre; Bálint, Gábor

    Lake Balaton has the largest freshwater surface in Central Europe. The water budget of this shallow water body is characterised in most of the years with significant water excess, expressed in regular releases from the Lake through a partly artificial stream, Sio. Unexpectedly, negative annual values of natural water budget occurred in the period 2000-2003, virtually without any release from the lake following May 2000. This happened first time since 1921, i.e. the start of instrumentally measured water budget elements. The extreme situation has been manifested by quick drop of water levels. Water levels recovered during 2004, but the first release through control gates could be started only in September 2005. Components of the water budget are compared with the normal situation, and different exceedance probabilities, based on the previous 80 years. Besides the given analysis, an attempt is made to answer the question in the title by presenting a quantitative methodology and three parallel macro-circulation classifications. The lack of precipitation during the 4-year period could not be sufficiently explained by shifted frequency of the circulation types combined by conditional average precipitation. However anomalous behaviour of meso-scale processes strongly contributed to the given extreme situation, endangering not only tourism of the lake, but its flora and fauna.

  5. Persistent Heavy Rainfall over South China During May-August:Subseasonal Anomalies of Circulation and Sea Surface Temperature

    Institute of Scientific and Technical Information of China (English)

    洪伟; 任雪娟

    2013-01-01

    This study investigates the relationship between subseasonal variations of the circulation and sea surface temperature (SST) over the South China-East Asian coastal region (EACR) in association with the persistent heavy rainfall (PHR) events over South China during May-August through statistical analysis. Based on the intensity threshold and duration criterion of the daily rainfall, a total of 63 May-June (MJ) and 59 July-August (JA) PHR events are selected over South China from 1979 to 2011. The lower-level circulation anomalies on subseasonal timescale exhibit an anomalous cyclone over South China and an anomalous anticyclone shaped like a tongue over the South China Sea (SCS) during the PHR events for MJ group. The anomalous cyclone over South China in MJ originates from low-value systems in the mid-high latitudes before the rainfall. The anomalous anticyclone over the SCS is due to the westward extension of the western Pacific subtropical high (WPSH) and the southeastward propagation of the anomalous anticyclone from South China before the rainfall. For JA group, the lower-level anomalous circulation pattern is similar to that for MJ over the South China-EACR, but with different features of propagation. The subseasonal anomalous anticyclone is also related to the westward stretch of the WPSH, while the anomalous cyclone is traced back to the weak anomalous cyclone over the Philippine Sea several days before the rainfall events. Positive SST anomaly (SSTA) is observed over the SCS and the Philippine Sea during the MJ PHR events on the subseasonal timescale. It is closely linked with the variation of local anomalous anticyclone. In contrast, negative SSTA occupies the South China coastal region for the JA PHR events, and it is driven by the anomalous cyclone which propagates northwestward from the Philippine Sea. The subseasonal positive (negative) SSTAs are generated via the local processes of above (below)-normal incident solar radiation and below (above

  6. Projections of Southern Hemisphere atmospheric circulation interannual variability

    Science.gov (United States)

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

    2016-05-01

    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.

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

    OpenAIRE

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

    2012-01-01

    Large changes in solar ultraviolet radiation can indirectly affect climate by inducing atmospheric changes. Specifically, it has been suggested that centennial-scale climate variability during the Holocene epoch was controlled by the Sun. However, the amplitude of solar forcing is small when compared with the climatic effects and, without reliable data sets, it is unclear which feedback mechanisms could have amplified the forcing. Here we analyse annually laminated sediments of Lake Meerfelde...

  8. 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...

  9. 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 ...

  10. 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...

  11. 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

  12. 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

  13. A parallel Atmosphere-Ocean Global Circulation Model of intermediate complexity for Earth system climate research

    Science.gov (United States)

    Silva, T. A.; Schmittner, A.

    2007-12-01

    We present the evolution of an Earth System model of intermediate complexity featuring an ocean global circulation model to include a fully coupled 3D primitive equations atmospheric model. The original Earth System climate model, UVic ESCM (Weaver et al. 2001), uses an ocean global circulation model coupled to a one layer atmospheric energy-moisture balance model. It also comprises a viscous-plastic rheology sea ice model, a mechanical land ice model, land surface, oceanic and terrestrial carbon models and a simple 3D marine ecosystem model (Schmittner et al. 2005). A spectral atmospheric, model, PUMA (Fraedrich et al. 2005), was coupled to the UVic ESCM to provide an atmosphere with nonlinear dynamics in target resolutions of T21, T31 and T42, as required. The coupling with the atmosphere, which involves data transfer, preprocessing and interpolation, is done through the OASIS3 coupler. During a run there are 2 + 2N parallel processes: the UVic ESCM, the Oasis3 coupler and the PUMA model with its domain split across 2N processes. The choice of N allows to balance more or less complex configurations of UVic model (e.g. higher level marine ecosystem model or number of biogeochemical tracers) with the atmospheric model at different resolutions, in order to maintain computational efficiency. The relatively simple parameterizations make this new atmosphere-ocean global circulation model much faster than a state-of-the-art Atmosphere-Ocean Global Circulation Model, and so optimally geared for decadal to millennial scale integrations. The latter require special care with the conservation of fluxes during coupling. A second order conservative interpolation method was applied (Jones 1999) and this is compared with the use of typical non-conservative methods.

  14. Changing correlation structures of the Northern Hemisphere atmospheric circulation from 1000 to 2100 AD

    OpenAIRE

    C. C. Raible; Lehner, F.; J. F. Gonzalez Rouco; L. Fernandez Donado

    2013-01-01

    Atmospheric circulation modes are important concepts to understand the variability of atmospheric dynamics. Assuming their spatial patterns to be fixed, such modes are often described by simple indices derived from rather short observational data sets. The increasing length of reanalysis products allows scrutinizing these concepts and assumptions. Here we investigate the stability of spatial patterns of Northern Hemisphere teleconnections by using the Twentieth Century Reanalysis as well as s...

  15. Changing correlation structures of the Northern Hemisphere atmospheric circulation from 1000 to 2100 AD

    OpenAIRE

    C. C. Raible; Lehner, F.; González-Rouco, J. F.; L. Fernández-Donado

    2014-01-01

    Atmospheric circulation modes are important concepts in understanding the variability of atmospheric dynamics. Assuming their spatial patterns to be fixed, such modes are often described by simple indices from rather short observational data sets. The increasing length of reanalysis products allows these concepts and assumptions to be scrutinised. Here we investigate the stability of spatial patterns of Northern Hemisphere teleconnections by using the Twentieth Century Reanalysis as well as s...

  16. Mechanisms Determining the Winter Atmospheric Response to the Atlantic Overturning Circulation

    OpenAIRE

    Gastineau, Guillaume; L’Hévéder, B.; Codron, Francis; Frankignoul, Claude

    2016-01-01

    International audience In climate models, an intensification of the Atlantic meridional overturning circulation (AMOC) precedes a warming in the North Atlantic subpolar basin by a few years. In the IPSL-CM5A-LR model, this warming may explain the atmospheric response to the AMOC observed in winter, which resembles a negative phase of the North Atlantic Oscillation (NAO). To firmly establish the causality links between the ocean and the atmosphere and illustrate the underlying mechanisms in...

  17. The Influence of Glacial Ice Sheets on Atlantic Meridional Overturning Circulation Through Atmospheric Circulation Change under Glacial Climate

    Science.gov (United States)

    Sherriff-Tadano, S.; Abe-Ouchi, A.; Yoshimori, M.; Oka, A.; Chan, W. L.

    2014-12-01

    It is well known that glacial ice sheets (Laurentide, Fennoscandian and Antarctic ice sheets) exert a large influence on the climate including the atmospheric circulation. Moreover, recent climate modeling studies suggest that glacial ice sheets have a large impact on the Atlantic meridional overturning circulation (AMOC). However, the process by which the ice sheets impact on the AMOC is not yet fully understood. On the other hand, recent studies showed that surface wind changes play a crucial role on changes to the AMOC under glacial climate. Therefore, in this study, we investigate in detail, the process by which the ice sheet modifies the AMOC through surface wind change. Here we conduct numerical experiments using an atmospheric general circulation model (AGCM) and an ocean general circulation model (OGCM) separately. Our method consists of 2 steps. First, from AGCM experiments, we evaluate the effect of glacial ice sheets on the surface wind. Second, from OGCM experiments, we evaluate the influence of the wind stress change on the AMOC by applying the surface wind change as a boundary condition, while leaving other boundary conditions (surface heat and water fluxes) unchanged. In addition, we conduct several sensitivity experiments. Using the AGCM, we explore individual ice sheet effect, ice sheet topography effect and albedo effect on surface wind change. Moreover, using the OGCM, we change the surface wind gradually or apply the surface wind change only at a specific region in order to explore the wind change effect in detail. We find that glacial ice sheets largely intensify the AMOC by surface wind change under glacial climate. Compare to other regions, it reveals that the wind change at the North Atlantic (NA) is a key region. There, the northern glacial ice sheet topography intensifies the Icelandic Low and anti-cyclonic circulation over the Laurentide ice sheet. However, this wind effect is effective only when the NA is not widely covered by sea ice

  18. Study of X-rays at the atmosphere of the South Atlantic Magnetic Anomaly

    International Nuclear Information System (INIS)

    A study of X-rays at the atmosphere of the South Atlantic Magnetic Anomaly is presented in this work, in which an analysis of all existing balloon measurements carried out at this region has been done. It is concluded that the X-ray flux due to electron precipitation depends strongly on geomagnetic activity, reaching at Sao Jose dos Campos a maximum doward flux of 10-2 photons/cm2.sec.KeV for 4g/cm2 and for the energy range of 30-150KeV. The related flux of precipitating electrons was computed by Monte Carlo method with values of about 500 electrons/cm2.sec and energy espectra of the type e-T/200. This electron flux is shown to represent the main ionization flux for the atmosphere at about 60 Km height. Furthermore, the atmospheric and diffuse components were determined at balloon altitudes (approximately 5g/cm2) of Sao Jose dos campos (λm = 110S) to be of the same order. (author)

  19. Middle atmospheric electrodynamic modification by particle precipitation at the South Atlantic magnetic anomaly

    Science.gov (United States)

    Gonzalez, W. D.; Dutra, S. L. G.; Pinto, O., Jr.

    1987-01-01

    Evidence for a localized middle atmospheric electrodynamic modification at low latitudes (southern Brazilian coast) of the South Atlantic Magnetic Anomaly (SAMA), in association with enhanced geomagnetic activity, are presented in a unified way combining recent observational efforts and related numerical studies. They involve a distortion effect in the fair weather electric field at balloon altitudes. This effect is attributed to a local intensification of energetic electron precipitation through a related middle atmospheric ionization enhancement and is elucidated by numeric simulation. From the electric field measurements and the numeric simulation, the intensification of precipitation is considered to occur in fairly narrow regions at the observed low L values (around L = 1.13) of the SAMA, with horizontal extensions of the order of a few hundred kilometers. A physical mechanism that could be responsible for this sort of intensification is suggested. Furthermore, a comparison of the phenomenon of middle atmospheric electrodynamic modification at the SAMA with a similar one at auroral latitudes, in response to enhanced solar and geomagnetic activity, is also given.

  20. Differential rotation in a solar-driven quasi-axisymmetric circulation. [of planetary atmospheres

    Science.gov (United States)

    Mayr, H. G.; Harris, I.; Chan, K. L.

    1984-01-01

    The concept of a quasi-axisymmetric circulation is used to explore the global scale dynamics of planetary atmospheres. A numerical circulation model applicable to Jupiter is presented, and an analytical study is performed elucidating the conditions leading to differential rotation in an atmosphere which is convectively unstable. A linear system forced by solar differential heating is considered, with nonlinear effects arising from advection being represented in the form of eddy diffusion. An empirical, latitudinal spectrum of the observed zonal wind field on Jupiter is discussed. Numerical solutions are presented which reveal banded wind fields with alternating and equatorial zonal jets and a multicellular Ferrel-Thomson meridional circulation consistent with the observed cloud striations on Jupiter. The vertical derivatives are parameterized to construct a simplified one-layer model.

  1. Atmospheric Diabatic Heating in Different Weather States and the General Circulation

    Science.gov (United States)

    Rossow, William B.; Zhang, Yuanchong; Tselioudis, George

    2016-01-01

    Analysis of multiple global satellite products identifies distinctive weather states of the atmosphere from the mesoscale pattern of cloud properties and quantifies the associated diabatic heating/cooling by radiative flux divergence, precipitation, and surface sensible heat flux. The results show that the forcing for the atmospheric general circulation is a very dynamic process, varying strongly at weather space-time scales, comprising relatively infrequent, strong heating events by ''stormy'' weather and more nearly continuous, weak cooling by ''fair'' weather. Such behavior undercuts the value of analyses of time-averaged energy exchanges in observations or numerical models. It is proposed that an analysis of the joint time-related variations of the global weather states and the general circulation on weather space-time scales might be used to establish useful ''feedback like'' relationships between cloud processes and the large-scale circulation.

  2. Cloudiness and weather variation in central Svalbard in July 2013 as related to atmospheric circulation

    Czech Academy of Sciences Publication Activity Database

    Láska, K.; Chládová, Zuzana; Ambrožová, K.; Husák, J.

    2013-01-01

    Roč. 3, č. 2 (2013), s. 184-195. ISSN 1805-0689 Institutional support: RVO:68378289 Keywords : atmospheric circulation * climate * cloudiness * weather * Svalbard * Arctic Subject RIV: DO - Wilderness Conservation http://www.sci.muni.cz/CPR/6cislo/Laska.pdf

  3. 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...

  4. The Atmospheric Circulation of a Nine-hot-Jupiter Sample: Probing Circulation and Chemistry over a Wide Phase Space

    Science.gov (United States)

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

    2016-04-01

    We present results from an atmospheric circulation study of nine hot Jupiters that compose 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, suggesting 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 kelvin, which could imply large variations in Na, K, CO and {{{CH}}}4 abundances in those regions. These chemical variations can be large enough to be observed in transmission with high-resolution spectrographs, such as ESPRESSO on VLT, METIS on the E-ELT, or MIRI and NIRSpec aboard JWST. We also compare theoretical emission spectra generated from our models to available Spitzer eclipse depths for each planet and find that the outputs from our solar-metallicity, cloud-free models generally provide a good match to many of the data sets, even without additional model tuning. Although these models are cloud-free, we can use their results to understand the chemistry and dynamics that drive cloud formation in their atmospheres.

  5. 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.

  6. 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.

  7. The role of atmospheric radiation in the generation and maintenance of circulations of different scales

    International Nuclear Information System (INIS)

    It is well known that the radiation budget of the atmosphere is an important component of the earth's climate system. On shorter time scales, radiative transfer affects the evolution of atmospheric circulation, principally through interaction with cloud and storm systems, and destabilizes the atmosphere continuously. This destabilization is important for subsequent development of clouds and storm systems. The clouds and storm systems feed back to the radiation budget, as clouds significantly alter both shortwave and longwave radiative transfer. It is important to understand the role that radiative transfer plays in the evolution of these circulation systems to accurately quantify the radiation budget. The results presented here are from modeling studies designed to isolate the effect of radiative transfer on the generation of circulation systems of different spatial and temporal scales. Two different numerical weather prediction models were used and will be described briefly in the next section. Following that, the radiative transfer model that was used with both circulation models will be described. Finally, results from the modeling studies will be presented, and conclusions and future research efforts will be discussed

  8. A USCLVAR Multi-Model Assessment of the Impact of SST Anomalies and Land-Atmosphere Feedbacks on Drought

    Science.gov (United States)

    Schubert, Siegfried

    2009-01-01

    The USCLIVAR working group on drought recently initiated a series of global climate model simulations forced with idealized SST anomaly patterns, designed to address a number of uncertainties regarding the impact of SST forcing and the role of land-atmosphere feedbacks on regional drought. Specific questions that the runs are designed to address include, What are the mechanisms that maintain drought across the seasonal cycle and from one year to the next? What is the role of the leading patterns of SST variability, and what are the physical mechanisms linking the remote SST forcing to regional drought, including the role of land-atmosphere coupling? The runs were carried out with five different atmospheric general circulation models (AGCMs), and one coupled atmosphere-ocean model in which the model was continuously nudged to the imposed SST forcing. This talk provides an overview of the experiments and some initial results focusing on the responses to the leading patterns of annual mean SST variability consisting of a Pacific El Nino/Southern Oscillation (ENSO)-like pattern, a pattern that resembles the Atlantic Multi-decadal Oscillation (AMO), and a global trend pattern. One of the key findings is that all the AGCMs produce broadly similar (though different in detail) precipitation responses to the Pacific forcing pattern, with a cold Pacific leading to reduced precipitation and a warm Pacific leading to enhanced precipitation over most of the United States. While the response to the Atlantic pattern is less robust, there is general agreement among the models that the largest precipitation response over the U.S. tends to occur when the two oceans have anomalies of opposite sign. That is, a cold Pacific and warm Atlantic tend to produce the largest precipitation reductions, whereas a warm Pacific and cold Atlantic tend to produce the greatest precipitation enhancements. Further analysis of the response over the U.S. to the Pacific forcing highlights a number of

  9. Enhanced lifetime of atmospheric circulation types over Europe: fact or fiction?

    Czech Academy of Sciences Publication Activity Database

    Cahynová, Monika; Huth, Radan

    2009-01-01

    Roč. 61, č. 3 (2009), s. 407-416. ISSN 0280-6495 R&D Projects: GA MŠk OC 115; GA AV ČR IAA300420506 Grant ostatní: COST(XE) 733 Institutional research plan: CEZ:AV0Z30420517 Keywords : atmospheric circulation * classification * circulation types * persistence * synoptic climatology Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 2.214, year: 2009 http://www3.interscience.wiley.com/cgi-bin/fulltext/121645997/PDFSTART

  10. Recent changes in air temperature, heat waves occurrences, and atmospheric circulation in Northern Africa

    Science.gov (United States)

    Fontaine, Bernard; Janicot, Serge; Monerie, Paul-Arthur

    2013-08-01

    study documents the time evolution of air temperature and heat waves occurrences over Northern Africa for the period 1979-2011. A significant warming (1°-3°C), appearing by the mid-1960s over Sahara and Sahel, is associated with higher/lesser frequency of warm/cold temperatures, as with longer duration and higher occurrences of heat waves. Heat waves episodes of at least 4 day duration have been examined after removing the long-term evolution. These episodes are associated with specific anomalies: (i) in spring, positive low-level temperature anomalies over the Sahel and Sahara; low and midlevel cyclonic rotation over Morocco associated with a Rossby wave pattern, lessening the Harmattan; more/less atmospheric moisture westward/eastward to 0°; upward/downward anomalies above the western/eastern regions associated with the Rossby wave pattern; (ii) in summer, a similar but weaker positive low-level temperature anomaly (up to 3°C); less moisture westward to 10°W, a cyclonic anomaly in central Sahel favoring the monsoon eastward to 0° and a midlevel anticyclonic anomaly over the Western Sahara, increasing southward the flux divergence associated with the African Easterly Jet. In March-May, two to three heat waves propagate eastward. They are preceded by an abnormal warm cell over Libya and southwesterlies over the West Sahara. A large trough stands over North Atlantic while midtropospheric subsidence and anticyclonic rotation reinforce over the continent, then migrates toward the Arabian peninsula in breaking up. These signals are spatially coherent and might suggest the role of short Rossby waves with an eastward group velocity and a baroclinic mode, possibly associated with jet stream deformation.

  11. Ability of the CCSR-NIES atmospheric general circulation model in the stratosphere. Chapter 3

    International Nuclear Information System (INIS)

    A quantitative evaluation of climate change such as global warming is impossible without a high-quality numerical model which describes the dynamics of the climate system and the circulation of energy and materials. The Center for Climate Research - National Institute for Environmental Studies (CCSR-NIES) atmospheric general circulation model (hereafter, GCM for a general circulation model) has been developed to obtain such a high-quality model. The emphasis of the development has been laid on the troposphere and the lower stratosphere below about 30 km altitude. This is natural because human beings live on the Earth's surface and the condition of the lower atmosphere directly affects human life. However, the stratosphere and the upper atmosphere beyond it have recently been the focus even in investigations of climate change, because they are relevant to many issues which relate closely to tropospheric climate change, such as the ozone hole, material exchange between the stratosphere and the troposphere, and physical interaction between the stratosphere and troposphere. This study extended the region of the CCSR-NIES GCM to the lower mesosphere (about 70 km from the surface). This is our first attempt to investigate this GCM's climatology in the upper atmosphere, although some studies for QBO in the middle and lower stratosphere had been done with the GCM

  12. From cold to warm gas giants: A three-dimensional atmospheric general circulation modeling

    Science.gov (United States)

    Medvedev, Alexander S.; Sethunadh, Jisesh; Hartogh, Paul

    2013-07-01

    We present a three-dimensional general circulation model suitable for simulating the atmospheric dynamics of giant gas planets. It was applied to studying the changes induced by an increased heating due to stellar radiation absorption compared to a Saturn-like planet. Such gravitationally unlocked "warm" extrasolar planets exist in large quantities at distances intermediate between those for cold and hot transiting giants, for instance, HD 155358b and HD 96063b. Our simulations indicate that inclusion of a moderate meridional temperature gradient in the troposphere significantly alter the circulation in the stratosphere, especially the zonal wind, which becomes superrotating on the entire planet. Thermal tides, which are almost certain on strong-lit and fast-rotating planets, changes mostly the meridional circulation, and, given its weakness, may reverse it. The analysis show that many of these changes are due to the momentum deposited by vertically propagating tides, and smaller-scale eddies trapped in the troposphere.

  13. 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...

  14. Study of the behaviour of artificial radioactive aerosols. Applications to some problems of atmospheric circulation (1963)

    International Nuclear Information System (INIS)

    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)

  15. LINKS BETWEEN ATMOSPHERIC CIRCULATION AND SURFACE AIR TEMPERATURE IN REGIONAL CLIMATE MODELS

    Czech Academy of Sciences Publication Activity Database

    Plavcová, Eva; Kyselý, Jan

    Patras: University of Patras, 2010 - (Argiriou, A.; Kazantzidis, A.), s. 825-832 ISBN 978-960-99254-0-2. [International Conference of Meteorology, Climatology and Atmospheric Physics (COMECAP2010) /10./. Patras (GR), 25.05.2010-28.05.2010] R&D Projects: GA ČR GAP209/10/2265 Grant ostatní: ENSEMBLES(XE) 505539 Institutional research plan: CEZ:AV0Z30420517 Keywords : regional climate model * daily air temperature * atmospheric circulation * Central Europe Subject RIV: DG - Athmosphere Sciences, Meteorology

  16. Investigating atmospheric predictability on Mars using breeding vectors in a general-circulation model

    OpenAIRE

    Newman, C. E.; P. L. Read; Lewis, S R

    2004-01-01

    A breeding vectors approach is used to investigate the hypothesis that the Martian atmosphere is predictable at certain times of year, by identifying the fastest-growing modes of instability at different times in a Mars general-circulation model. Results indicate that the period from northern mid-spring until mid-autumn is remarkably predictable, with negative global growth rates for a range of conditions, in contrast to the situation on the earth. From northern late autumn to early spring...

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

    OpenAIRE

    Xi Xi

    2014-01-01

    Stable water isotopologues, mainly ^1H_2O, ^1H^2HO (HDO), and ^1H_2 ^(18)O, 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 accomplis...

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

    OpenAIRE

    Camargo, Suzana J.; 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...

  19. Land surface hydrology parameterization for atmospheric general circulation models including subgrid scale spatial variability

    Science.gov (United States)

    Entekhabi, D.; Eagleson, P. S.

    1989-01-01

    Parameterizations are developed for the representation of subgrid hydrologic processes in atmospheric general circulation models. Reasonable a priori probability density functions of the spatial variability of soil moisture and of precipitation are introduced. These are used in conjunction with the deterministic equations describing basic soil moisture physics to derive expressions for the hydrologic processes that include subgrid scale variation in parameters. The major model sensitivities to soil type and to climatic forcing are explored.

  20. The effect of topography-enhanced diapycnal mixing on ocean and atmospheric circulation and marine biogeochemistry

    OpenAIRE

    Friedrich, T.; Timmermann, A.; Decloedt, T.; Luther, D.S.; Mouchet, A.

    2011-01-01

    The impact of topographically catalysed diapycnal mixing on ocean and atmospheric circulation as well as marine biogeochemistry is studied using an earth system model of intermediate complexity. The results of a model run in which diapycnal mixing depends on seafloor roughness are compared to a control run that uses a simple depth-dependent parametrization for vertical background diffusivity. A third model run is conducted that uses the horizontal mean of the topographically catalysed mixing ...

  1. Characterizing the Atmospheric Circulation over the Colombian Orinoquia through Lagrangian Back-Trajectory Analysis

    Science.gov (United States)

    Orjuela, H. R.; Leon, G. E.; Jimenez-Pizarro, R.

    2012-12-01

    The ongoing transformation of the Colombian Orinoquia (Eastern Plains) due to the rapid expansion of the agricultural frontier and oil production implies a series of new atmospheric emissions, which might negatively impact human health and ecosystems in different ways. Some air pollutants have already been detected in the region. This is the case of Persistent Organic Pollutants (POPs), which are sampled in a site of the Global Atmospheric Passive Sampling (GAPS) network located in Arauca, Colombia. The current understanding on the origin and transport of pollutants is limited due to the lack of information on the atmospheric circulation in the Colombian Orinoquia. This research aims at generating new knowledge on the meteorology of this region mainly for weather forecasting and atmospheric pollution impact assessment. We present a conceptual model of the atmospheric circulation in the Colombian Orinoquia, including the main synoptic and mesoscale factors governing its meteorology. In order to identify the source of air masses and synoptic scale disturbances, we used Lagrangian back trajectories obtained with the model HYSPLIT 4.9 over the period 2000-2010. NCEP/NCAR and Global Data Assimilation System (GDAS) reanalysis results were used as meteorological input to HYSPLIT. Prior to the Lagrangian simulation, these global datasets were evaluated for their capability to reproduce meteorological observations in the region, particularly for rain and flood-triggering conditions. The observational data included satellite images and ground level network measurements by the Colombian Institute of Hydrology, Meteorology and Environmental Research (IDEAM). Windgridds and other data analysis tools were used.

  2. 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.

  3. Regional atmospheric circulation over Europe during the Last Glacial Maximum and its links to precipitation

    Science.gov (United States)

    Ludwig, Patrick; Schaffernicht, Erik J.; Shao, Yaping; Pinto, Joaquim G.

    2016-03-01

    The Last Glacial Maximum (LGM) exhibits different large-scale atmospheric conditions compared to present-day climate due to altered boundary conditions. The regional atmospheric circulation and associated precipitation patterns over Europe are characterized for the first time with a weather typing approach (circulation weather types, CWT) for LGM paleoclimate simulations. The CWT approach is applied to four representative regions across Europe. While the CWTs over Western Europe are prevailing westerly for both present-day and LGM conditions, considerable differences are identified elsewhere: Southern Europe experienced more frequent westerly and cyclonic CWTs under LGM conditions, while Central and Eastern Europe was predominantly affected by southerly and easterly flow patterns. Under LGM conditions, rainfall is enhanced over Western Europe but is reduced over most of Central and Eastern Europe. These differences are explained by changing CWT frequencies and evaporation patterns over the North Atlantic Ocean. The regional differences of the CWTs and precipitation patterns are linked to the North Atlantic storm track, which was stronger over Europe in all considered models during the LGM, explaining the overall increase of the cyclonic CWT. Enhanced evaporation over the North Atlantic leads to higher moisture availability over the ocean. Despite the overall cooling during the LGM, this explains the enhanced precipitation over southwestern Europe, particularly Iberia. This study links large-scale atmospheric dynamics to the regional circulation and associated precipitation patterns and provides an improved regional assessment of the European climate under LGM conditions.

  4. The 1991-1992 atmospheric methane anomaly: Southern hemisphere 13C decrease and growth rate fluctuations

    Science.gov (United States)

    Lowe, David C.; Manning, Martin R.; Brailsford, G. W.; Bromley, A. M.

    Measurements of atmospheric methane from 1989-1996 at Baring Head, New Zealand, and at Scott Base, Antarctica show a seasonal cycle in the mixing ratio with a peak to peak amplitude of 28 ppb. This is superposed on a trend varying between 16 ppb yr-1 and near zero. δ13C values also show a seasonal cycle, with an amplitude of 0.1-0.3‰, approximately 6 months out of phase with the mixing ratio cycle. A pronounced negative anomaly in δ13C occurred in 1992 with annual average values dropping from -47.08‰ to -47.28‰. From 1992 to 1996, average δ13C values recovered slowly at an average rate of about 0.04‰ yr-1. The simultaneous changes in the mixing ratio growth rate and δ13C together with the rapid drop and slow recovery in the latter provide a stringent test of possible causes. Although a combination of causes cannot be ruled out, decreased emissions from an isotopically heavy source such as biomass burning best meet the constraints of the data.

  5. 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.

  6. Impact of oceanic circulation changes on atmospheric δ13CO2

    Science.gov (United States)

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

    2015-11-01

    δ13CO2 measured in Antarctic ice cores provides constraints on oceanic and terrestrial carbon cycle processes linked with millennial-scale changes in atmospheric CO2. However, the interpretation of δ13CO2 is not straightforward. Using carbon isotope-enabled versions of the LOVECLIM and Bern3D models, 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 oceanic 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 transport 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. This results from complex interplay between global climate, carbon cycle, and the formation rate of NADW, a water body characterized by relatively high δ13C.

  7. 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...

  8. Reduction of thermohaline circulation during deglaciation: The effect on atmospheric radiocarbon and CO2

    International Nuclear Information System (INIS)

    A two-box ocean reservoir model is employed to examine the combined effects of vertical ocean circulation, organic matter extraction and cosmic ray production on the 14C/12C in the atmosphere, ocean and sediment. In this model, dissolution of deep-sea calcium carbonate sediment is assumed to respond to the supply of particulate carbonate from the surface ocean and to the dissolved carbonate-ion concentration of the deep-sea. If the vertical ocean circulation decreased by 50% during the maximum rate of deglaciation, the atmospheric 14C/12C would have increased concurrently by 10% relative to the pre-bomb present. Further, if cosmic ray production of 14C was 50% greater than present at about 7800 years B.P. as suggested by archeomagnetic measurements, a double maximum of 10% occurs. The first is at about 10.5 ka and the second at 6.5 ka. This result is similar to the variation of 14C/12C over the last 10,000 years calculated from the 14C dates measured by Stuiver on the varved Lake of the Clouds. The result is not sensibly altered if 1017 moles of organic carbon is extracted from the ocean during sea-level rise. Reduction of the thermohaline ocean circulation by 50% over a one- to two-thousand-year interval would not be sensibly detected in the dating of deep-sea sediment. If Broecker's organic nutrient extraction occurs in conjugation with reduction of vertical circulation, a decrease in the atmospheric Psub(CO2) will precede the eventual rise. (orig.)

  9. Response of thermohaline circulation to higher atmospheric CO2 concentration and absence of ice sheets

    Science.gov (United States)

    Motoi, T.; Chan, W.-L.; Yih, H.

    2003-04-01

    Response of thermohaline circulation to higher CO2 concentration in the atmosphere and absence of large ice sheets are investigated by using a coupled ocean-atmosphere model. Two runs, named C run and x4CNIS run are carried out. The C run is control run with standard atmospheric CO2 concentration of 300 ppm and Greenland and Antarctic ice sheets. The x4CNIS run has atmospheric CO2 concentration of 1200 ppm, which is 4 times that of the standard value, and no ice sheet. Both the C run and x4CNIS run are integrated for more than 10000 years until equilibrium response is completed. The intensity of thermohaline circulation in the North Atlantic Ocean in x4CNIS run decreases to 3 Sv from 17 Sv during the first two hundred years and turns to gradually increasing phase from 3 Sv to 8 Sv for about 2000 years. It then increases rapidly from 8 Sv to 30 Sv within 200 years and reaches stable level of 24 Sv, which is larger than that of 17 Sv at begining, with larger oscillations. The temperatures of surface and deep waters in the sub-antarctic region and of deep tropical water are about 6.5 deg. warmer in the x4CNIS run than in the C run.

  10. An advanced method for classifying atmospheric circulation types based on prototypes connectivity graph

    Science.gov (United States)

    Zagouras, Athanassios; Argiriou, Athanassios A.; Flocas, Helena A.; Economou, George; Fotopoulos, Spiros

    2012-11-01

    Classification of weather maps at various isobaric levels as a methodological tool is used in several problems related to meteorology, climatology, atmospheric pollution and to other fields for many years. Initially the classification was performed manually. The criteria used by the person performing the classification are features of isobars or isopleths of geopotential height, depending on the type of maps to be classified. Although manual classifications integrate the perceptual experience and other unquantifiable qualities of the meteorology specialists involved, these are typically subjective and time consuming. Furthermore, during the last years different approaches of automated methods for atmospheric circulation classification have been proposed, which present automated and so-called objective classifications. In this paper a new method of atmospheric circulation classification of isobaric maps is presented. The method is based on graph theory. It starts with an intelligent prototype selection using an over-partitioning mode of fuzzy c-means (FCM) algorithm, proceeds to a graph formulation for the entire dataset and produces the clusters based on the contemporary dominant sets clustering method. Graph theory is a novel mathematical approach, allowing a more efficient representation of spatially correlated data, compared to the classical Euclidian space representation approaches, used in conventional classification methods. The method has been applied to the classification of 850 hPa atmospheric circulation over the Eastern Mediterranean. The evaluation of the automated methods is performed by statistical indexes; results indicate that the classification is adequately comparable with other state-of-the-art automated map classification methods, for a variable number of clusters.

  11. Estimate of the largest Lyapunov characteristic exponent of a high dimensional atmospheric global circulation model: a sensitivity analysis

    International Nuclear Information System (INIS)

    In this report the largest Lyapunov characteristic exponent of a high dimensional atmospheric global circulation model of intermediate complexity has been estimated numerically. A sensitivity analysis has been carried out by varying the equator-to-pole temperature difference, the space resolution and the value of some parameters employed by the model. Chaotic and non-chaotic regimes of circulation have been found.

  12. 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.

  13. 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...

  14. The atmospheric circulation and observable properties of non-synchronously rotating hot Jupiters

    International Nuclear Information System (INIS)

    We study the feasibility of observationally constraining the rotation rate of hot Jupiters, planets that are typically assumed to have been tidally locked into synchronous rotation. We use a three-dimensional General Circulation Model to solve for the atmospheric structure of two hot Jupiters (HD 189733b and HD 209458b), assuming rotation periods that are 0.5, 1, or 2 times their orbital periods (2.2 and 3.3 days, respectively), including the effect of variable stellar heating. We compare two observable properties: (1) the spatial variation of flux emitted by the planet, measurable in orbital phase curves, and (2) the net Doppler shift in transmission spectra of the atmosphere, which is tantalizingly close to being measurable in high-resolution transit spectra. Although we find little difference between the observable properties of the synchronous and non-synchronous models of HD 189733b, we see significant differences when we compare the models of HD 209458b. In particular, the slowly rotating model of HD 209458b has an atmospheric circulation pattern characterized by westward flow and an orbital phase curve that peaks after secondary eclipse (in contrast to all of our other models), while the quickly rotating model has a net Doppler shift that is more strongly blueshifted than the other models. Our results demonstrate that the combined use of these two techniques may be a fruitful way to constrain the rotation rate of some planets and motivate future work on this topic.

  15. 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

  16. The genesis and predictability of persistent Pacific–North American anomalies in a model atmosphere

    OpenAIRE

    Lin, Hai; DEROME, JACQUES

    2011-01-01

    The setup process of Pacific–North American (PNA) pattern anomalies that last more than10 days and the role played therein by synoptic-scale transients are investigated using a T21,3-level quasi-geostrophic model. As there is no time-dependent forcing in the model, the lowfrequencyPNA anomalies are generated entirely by the internal dynamics. From a 300-winterintegration, 100 cases of positive PNA anomalies and 118 cases of negative PNA anomalieslasting at least 10 days are identified. The PN...

  17. 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

  18. Subseasonal temperature trends in Europe (1961-2000) and their links to atmospheric circulation

    Czech Academy of Sciences Publication Activity Database

    Cahynová, Monika; Pokorná, L.

    Brno: Global change research centre, Academy of Sciences of the Czech Republic, v. v. i, 2013 - (Stojanov, R.; Žalud, Z.; Cudlín, P.; Farda, A.; Urban, O.; Trnka, M.), s. 90-94 ISBN 978-80-904351-8-6. [ Global Change and Resilience. Brno (CZ), 22.05.2013-24.05.2013] R&D Projects: GA MŠk(CZ) ED1.1.00/02.0073 Institutional support: RVO:67179843 Keywords : air temperature * daily temperature range * trend * atmospheric circulation * classification Subject RIV: EH - Ecology, Behaviour

  19. Subseasonal temperature trends in Europe (1961-2000) and their links to atmospheric circulation

    Czech Academy of Sciences Publication Activity Database

    Cahynová, Monika; Pokorná, Lucie

    Brno: Global change research centre, Academy of Sciences of the Czech Republic, v. v. i, 2013 - (Stojanov, R.; Žalud, Z.; Cudlín, P.; Farda, A.; Urban, O.; Trnka, M.), s. 100-104 ISBN 978-80-904351-8-6. [ Global Change and Resilience. Brno (CZ), 22.05.2013-24.05.2013] R&D Projects: GA ČR(CZ) GPP209/12/P811 Institutional support: RVO:68378289 Keywords : air temperature * daily temperature range * trend * atmospheric circulation * classification Subject RIV: DG - Athmosphere Sciences, Meteorology

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

    Science.gov (United States)

    Evangelista, H.; Wainer, I.; Sifeddine, A.; Corrège, T.; Cordeiro, R. C.; Lamounier, S.; Godiva, D.; Shen, C.-C.; Le Cornec, F.; Turcq, B.; Lazareth, C. E.; Hu, C.-Y.

    2015-08-01

    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.

  1. Precipitation-climate sensitivity to initial conditions in an atmospheric general circulation model

    Energy Technology Data Exchange (ETDEWEB)

    Covey, C., LLNL

    1997-03-01

    Atmospheric climate, in contrast to weather, is traditionally considered to be determined by boundary conditions such as sea surface temperature (SST). To test this hypothesis, we examined annual mean precipitation from an ensemble of 20 general circulation model (GCM) simulations. Ensemble members were forced with identical 10-year series of SST and sea ice, but they began with slightly differing initial conditions. A surprisingly small proportion of the variance in the output is attributable to the effects of boundary forcing. This result-and similar evidence from smaller ensembles of other GCM simulations-implies that long-term precipitation variations are mostly unpredictable, even if SST forecasts are `perfect.`

  2. Simulation of sea surface temperatures with the surface heat fluxes from an atmospheric circulation model

    OpenAIRE

    Karaca, Mehmet; MÜLLER, DETLEV

    2011-01-01

    The global fields of the surface heat fluxes for the December-February period are calculated with the UCLA atmospheric circulation model (ACM). This model operates on a global grid net. The planetary boundary layer (PBL), as the decisive subsystem for the surface fluxes, is parameterized in terms of its bulk properties. For several locations in the north Atlantic, the model heat fluxes are incorporated into the forcing of a simple ocean mixed-layer (OML) model. The OML-model uses a slight gen...

  3. A System of Conservative Regridding for Ice-Atmosphere Coupling in a General Circulation Model (GCM)

    Science.gov (United States)

    Fischer, R.; Nowicki, S.; Kelley, M.; Schmidt, G. A.

    2014-01-01

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

  4. Discrepancies in tropical upper tropospheric warming between atmospheric circulation models and satellites

    Science.gov (United States)

    Po-Chedley, Stephen; Fu, Qiang

    2012-12-01

    Recent studies have examined tropical upper tropospheric warming by comparing coupled atmosphere-ocean global circulation model (GCM) simulations from Phase 3 of the Coupled Model Intercomparison Project (CMIP3) with satellite and radiosonde observations of warming in the tropical upper troposphere relative to the lower-middle troposphere. These studies showed that models tended to overestimate increases in static stability between the upper and lower-middle troposphere. We revisit this issue using atmospheric GCMs with prescribed historical sea surface temperatures (SSTs) and coupled atmosphere-ocean GCMs that participated in the latest model intercomparison project, CMIP5. It is demonstrated that even with historical SSTs as a boundary condition, most atmospheric models exhibit excessive tropical upper tropospheric warming relative to the lower-middle troposphere as compared with satellite-borne microwave sounding unit measurements. It is also shown that the results from CMIP5 coupled atmosphere-ocean GCMs are similar to findings from CMIP3 coupled GCMs. The apparent model-observational difference for tropical upper tropospheric warming represents an important problem, but it is not clear whether the difference is a result of common biases in GCMs, biases in observational datasets, or both.

  5. 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.

  6. Interannual drought index variations in Central Europe related to large-scale atmospheric circulation

    Science.gov (United States)

    Beck, Christoph; Philipp, Andreas; Jacobeit, Jucundus

    2014-05-01

    This contribution investigates the relationship between large-scale atmospheric circulation and interannual variations of the standardized precipitation index (SPI) in central Europe. To this end occurrence frequencies of circulation types (CT) derived from a variety of circulation type classifications (CTC) applied to daily sea level pressure (SLP) data and mean circulation indices of vorticity (V), zonality (Z) and meridionality (M) have been utilized as predictors within multiple regression models (MRM) for the estimation of gridded 3-month SPI values over central Europe for the period 1950 to 2010. CTC based MRMs used in the analyses comprise variants concerning the basic method for CT classification, the number of CTs, the size and location of the spatial domain used for CTCs and the exclusive use of CT frequencies or the combined use of CT frequencies and mean circulation indices as predictors. Adequate MRM predictor combinations have been identified by applying stepwise multiple regression analyses within a resampling framework. The performance (robustness) of the resulting MRMs has been quantified based on a leave-one out cross-validation procedure applying several skill scores. Furthermore the relative importance of individual predictors has been estimated for each MRM. From these analyses it can be stated that i.) the consideration of vorticity characteristics within CTCs, ii.) a relatively small size of the spatial domain to which CTCs are applied and iii.) the inclusion of mean circulation indices appear to improve model skill. However model skill exhibits distinct variations between seasons and regions. Whereas promising skill can be stated for the western and northwestern parts of the central European domain only unsatisfactorily skill is reached in the more continental regions and particularly during summer. Thus it can be concluded that the here presented approaches feature the potential for the downscaling of central European drought index

  7. Intensified anticyclonic anomaly over the western North Pacific during El Niño decaying summer under a weakened Atlantic thermohaline circulation

    OpenAIRE

    Chen, Wei; Lu, Riyu; Dong, Buwen

    2014-01-01

    It has been well documented that there is an anticyclonic anomaly over the western North Pacific (WNPAC, hereafter) during El Niño decaying summer. This El Niño-WNPAC relationship is greatly useful for the seasonal prediction of summer climate in the WNP and East Asia. In this study, we investigate the modification of the El Niño-WNPAC relationship induced by a weakened Atlantic thermohaline circulation (THC) in a water-hosing experiment. The results suggest that the WNPAC during the El Niño ...

  8. 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.

  9. 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...

  10. A search for short-term meteorological effects of solar variability in an atmospheric circulation model

    Science.gov (United States)

    Somerville, R. C. J.; Quirk, W. J.; Hansen, J. E.; Lacis, A. A.; Stone, P. H.

    1976-01-01

    A set of numerical experiments is carried out to test the short-range sensitivity of the Goddard Institute for Space Studies global atmospheric general-circulation model to changes in solar constant and ozone amount. These experiments consist of forecasts initiated with actual atmospheric data. One set of forecasts is made with a standard version of the model; another set uses the model modified by very different values of the solar constant (two-thirds and three-halves of the standard value) and of the ozone amount (zero and twice the standard amount). Twelve-day integrations with these very large variations show such small effects that the effects of realistic variations would almost certainly be insignificant meteorologically on this time scale.

  11. 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...

  12. Snow cover setting-up dates in the north of Eurasia: relations and feedback to the macro-scale atmospheric circulation

    Directory of Open Access Journals (Sweden)

    V. V. Popova

    2014-01-01

    Full Text Available Variations of snow cover onset data in 1950–2008 based on daily snow depth data collected at first-order meteorological stations of the former USSR compiled at the Russia Institute of Hydrometeorological Information are analyzed in order to reveal climatic norms, relations with macro-scale atmospheric circulation and influence of snow cover anomalies on strengthening/weakening of westerly basing on observational data and results of simulation using model Planet Simulator, as well. Patterns of mean snow cover setting-up data and their correlation with temperature of the Northern Hemisphere extra-tropical land presented in Fig. 1 show that the most sensible changes observed in last decade are caused by temperature trend since 1990th. For the most portion of the studied territory variations of snow cover setting-up data may be explained by the circulation indices in the terms of Northern Hemisphere Teleconnection Patterns: Scand, EA–WR, WP and NAO (Fig. 2. Role of the Scand and EA–WR (see Fig. 2, а, в, г is recognized as the most significant.Changes of snow cover extent calculated on the base of snow cover onset data over the Russia territory, and its western and eastern parts as well, for the second decade of October (Fig. 3 demonstrate significant difference in variability between eastern and western regions. Eastern part of territory essentially differs by lower both year-to-year and long-term variations in the contrast to the western part, characterized by high variance including long-term tendencies: increase in 1950–70th and decrease in 1970–80 and during last six years. Nevertheless relations between snow cover anomalies and Arctic Oscillation (AO index appear to be significant exceptionally for the eastern part of the territory. In the same time negative linear correlation revealed between snow extent and AO index changes during 1950–2008 from statistically insignificant values (in 1950–70 and 1996–2008 to coefficient

  13. Role of Ice Sheets in Thermohaline Circulation Changes Under High Atmospheric Carbon Dioxide Concentration

    Science.gov (United States)

    Yih, H.; Oh, I. S.; Chan, W.; Motoi, T.

    2007-12-01

    Thermohaline circulation (THC) changes are considered for two experimental settings of Antarctic and Greenland ice sheets with the atmospheric carbon dioxide of 1200 ppm in GFDL atmosphere-ocean coupled model. The experimental settings are to figure out the role of the ice sheets in global climate system, in which they are present and completely removed. The coupled model consists of the atmosphere and oceans, as well as simple models of land surfaces and sea ice. Atmospheric distribution of predicted variables is represented by Rhomboidal 15 configuration and nine vertical levels. Oceanic variables in 12 vertical levels have horizontal resolution of 4.5 degree latitude and 3.75 degree longitude. Streamfunctions of zonal mean meridional circulation in model oceans are used as representing fields of the THC, which are constructed after reaching statistical equilibrium state at 3000 model years. Same restart file is used for the two runs, which is at approximately 10000 model years of integration with atmospheric carbon dioxide concentration of 300 ppm provided from GFDL/NOAA. The THC appears again, after weakening, strengthening, and rapid-increasing during the first 3000 model years. Analysis periods of the equilibrium state are from 3000 to 10000 model years. Streamfunctions of the two runs show in general similar pattern of circulation cells of North Atlantic Deep Water (NADW) and Antarctic Bottom Water (AABW). The cell of NADW occupies upper 2000 m mainly in north of 10 degree South, but the cell of AABW extends up to 50 degree North from the Antarctic continent in the layer below the deeper part of the NADW, while covering up to the surface in the south of 60 degree South. Difference-field of streamfunction between the two runs shows two core-regions. One core is located in the deeper part of Southern Ocean (i.e., the depth range of 2500-4000 m), and the other in the upper part, 500-2000 m depths, in the Northern Hemisphere. Latitudinal ranges of the two cores

  14. 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

  15. 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...

  16. Atmospheric effects of nuclar war aerosols in general circulation model simulations: Influence of smoke optical properties

    International Nuclear Information System (INIS)

    A global atmospheric general circulation model (GCM) is modified to include radiative transfer parameterizations for the absorption and scattering of solar radiation and the absorption of thermal infrared (IR) radiation by smoke aerosols. The solar scattering modifications include a parameterization for diagnosing smoke optical properties as a function of the time- and space-dependent smoke particle radii. The aerosol IR modifications allow for both the ''grey'' absorber approximation and a broadband approximation that resolves the aerosol absorption in four spectral intervals. We examine the sensitivity of some GCM-simulated atmospheric and climatic effects to the optical properties and radiative transfer parameterizations used in studies of massive injections of smoke. Specifically, we test the model response to solar scattering versus nonscattering smoke, variations in prescribed smoke single scattering albedo and IR specific absorption, and interactive versus fixed smoke optical properties. Hypothetical nuclear war created smoke scenarios assume the July injection of 60 or 180 Tg of smoke over portions of the mid-latitude land areas of the northern hemisphere. Atmospheric transport and scavenging of the smoke are included. Nonscattering smoke cases produce roughly 40 Wm/sup -2/ more Earth-atmosphere solar irradiance absorption over the northern hemisphere, when compared to scattering smoke cases having equivalent specific absorption efficiencies. Varying the elemental carbon content of smoke over a plausible range produces a 40--6 0C change in average mid-latitude land surface temperature, and a variation of about 0.1 in zonally averaged planetary albedo in the northern hemisphere

  17. Neutrino physics and the mirror world: how exact parity symmetry explains the solar neutrino deficit, the atmospheric neutrino anomaly and the LSND experiment

    International Nuclear Information System (INIS)

    Evidence for ν-barμ → ν-bare oscillations has been reported at LAMPF using the LSND detector. Further evidence for neutrino mixing comes from the solar neutrino deficit and the atmospheric neutrino anomaly. All of these anomalies require new physics. It is shown that all of these anomalies can be explained if the standard model is enlarged so that an unbroken parity symmetry can be defined. This explanation holds independently of the actual model for neutrino masses. Thus, it is argued that parity symmetry is not only a beautiful candidate for a symmetry beyond the standard model, but it can also explain the known neutrino physics anomalies. 41 refs

  18. Neutrino physics and the mirror world: How exact parity symmetry explains the solar neutrino deficit, the atmospheric neutrino anomaly, and the LSND experiment

    International Nuclear Information System (INIS)

    Important evidence for neutrino oscillations comes from the solar neutrino deficit and the atmospheric neutrino anomaly. Further evidence for bar νμ→ bar νe oscillations has been reported at LAMPF using the LSND detector. All of these anomalies require new physics. We show that all of these anomalies can be explained if the standard model is enlarged so that an unbroken parity symmetry can be defined. This explanation holds independently of the actual model for neutrino masses. Thus, we argue that parity symmetry is not only a beautiful candidate for a symmetry beyond the standard model, but it can also explain the known neutrino physics anomalies

  19. 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.

  20. 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.

  1. 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.

  2. Changing correlation structures of the Northern Hemisphere atmospheric circulation from 1000 to 2100 AD

    Directory of Open Access Journals (Sweden)

    C. C. Raible

    2013-08-01

    Full Text Available Atmospheric circulation modes are important concepts to understand the variability of atmospheric dynamics. Assuming their spatial patterns to be fixed, such modes are often described by simple indices derived from rather short observational data sets. The increasing length of reanalysis products allows scrutinizing these concepts and assumptions. Here we investigate the stability of spatial patterns of Northern Hemisphere teleconnections by using the Twentieth Century Reanalysis as well as several control and transient millennium-scale simulations with coupled models. The observed and simulated centers of action of the two major teleconnection patterns, the North Atlantic Oscillation (NAO and to some extent the Pacific North American (PNA, are not stable in time. The currently observed dipole pattern of the NAO with its center of action over Iceland and the Azores split into a North-South dipole pattern in the western Atlantic and a wave train pattern in the eastern part connecting the British Isles with West Greenland and the Eastern Mediterranean in the period 1940–1969 AD. The PNA centers of action over Canada are shifted southwards and over Florida into the Gulf of Mexico in the period 1915–1944 AD. The analysis further shows that shifts in the centers of action of either telconnection pattern are not related to changes in the external forcing applied in transient simulations of the last millennium. Such shifts in their centers of action are associated with changes in the relation of local precipitation and temperature to the overlying atmospheric mode. These findings further undermine the assumption of stationarity between local climate/proxy variability and large-scale dynamics inherent in proxy-based reconstructions of atmospheric modes and call for a more robust understanding of atmospheric variability on decadal time scales.

  3. 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.;

    2015-01-01

    . Consequently, simultaneous occurrence of extreme water level and precipitation events is expected to increase in the future as a result of change in LCC frequencies. The RCM projections for LCC frequencies are uncertain because the representation of current LCCs is poor; a large number of days cannot......The aim of this study is to enhance the understanding of the occurrence of flood generating events in urban areas by analyzing the relationship between large-scale atmospheric circulation and extreme precipitation events, extreme sea water level events and their simultaneous occurrence......, 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...

  4. 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. PMID:27450248

  5. Vertical resolution dependence of gravity wave momentum flux simulated by an atmospheric general circulation model

    Directory of Open Access Journals (Sweden)

    S. Watanabe

    2014-11-01

    Full Text Available The dependence of the gravity wave spectra of energy and momentum flux on the horizontal resolution and time step of atmospheric general circulation models (AGCMs has been thoroughly investigated in the past. In contrast, much less attention has been given to the dependence of these gravity wave parameters on models' vertical resolutions. The present study demonstrates the dependence of gravity wave momentum flux in the stratosphere and mesosphere on the model's vertical resolution, which is evaluated using an AGCM with a horizontal resolution of about 0.56°. We performed a series of sensitivity test simulations changing only the model's vertical resolution above a height of 8 km, and found that inertial gravity waves with short vertical wavelengths simulated at higher vertical resolutions likely play an important role in determining the gravity wave momentum flux in the stratosphere and mesosphere.

  6. Thermohaline circulation stability: a box model study - Part II: coupled atmosphere-ocean model

    CERN Document Server

    Lucarini, V; Lucarini, Valerio; Stone, Peter H.

    2004-01-01

    A thorough analysis of the stability of a coupled version of an inter-hemispheric 3-box model of Thermohaline Circulation (THC) is presented. This study follows a similarly structured analysis on an uncoupled version of the same model presented in Part I. We study how the strength of THC changes when the system undergoes forcings representing global warming conditions. Each perturbation to the initial equilibrium is characterized by the total radiative forcing realized, by the rate of increase, and by the North-South asymmetry. The choice of suitably defined metrics allows us to determine the boundary dividing the set of radiative forcing scenarios that lead the system to equilibria characterized by a THC pattern similar to the present one, from those that drive the system to equilibria where the THC is reversed. We also consider different choices for the atmospheric transport parameterizations and for the ratio between the high latitude to tropical radiative forcing. We generally find that fast forcings are ...

  7. Anomalies of Pulmonary Circulation as a Cause of Hemoptysis: A Series of Unusual Cases and Review of the Literature

    Directory of Open Access Journals (Sweden)

    Kamini Gupta

    2015-05-01

    Full Text Available The expectoration of blood originating from the lower respiratory tract, called hemoptysis, is a common clinical condition with many potential etiologies. Massive hemoptysis is life threatening and needs urgent intervention. Multidetector computed tomography (MDCT is a useful non-invasive imaging modality for the initial assessment of hemoptysis. Using MDCT with multiplanar reformatted images has improved the diagnosis and management of hemoptysis by providing a more precise depiction of bronchial and non-bronchial systemic arteries than conventional computed tomography (CT. In 95% of hemoptysis cases, the systemic arterial system is the origin of bleeding and pulmonary vascular anomalies are a rare cause. Among these, pulmonary arteriovenous malformation, hereditary hemorrhagic telangiectasia, and Osler-Weber-Rendu disease are well known entities. However, primary anomalies affecting pulmonary vessels in the mediastinum or diseases secondarily affecting the pulmonary vessels are unusual causes. Here we present three cases where patients had pulmonary vascular anomalies causing hemoptysis. These patients had decreased pulmonary arterial pressures leading to bronchial and systemic arterial hypertrophy and development of bronchopulmonary collaterals. Secondary CT signs in the parenchyma and mediastinum (mosaic attenuation, ground glass haze, subpleural interstitial thickening, and hypertrophied bronchial arteries were similar in all patients. Hence, evaluation of the MDCT images for primary abnormality led to the diagnosis.

  8. Mid-Brunhes climatic event: long-term changes in global atmosphere and ocean circulation

    Energy Technology Data Exchange (ETDEWEB)

    Jansen, J.H.F.; Kuijpers, A.; Troelstra, S.R.

    1986-05-02

    A long-term climatic change 4.0 x 10/sup 5/ to 3.0 x 10/sup 5/ years ago is recorded in deep sea sediments of the Angola and Canary basins in the eastern Atlantic Ocean. In the Angola Basin (Southern Hemisphere) the climatic signal shows a transition to more humid (interglacial) conditions in equatorial Africa, and in the Canary Basin (Northern Hemisphere) to more glacial oceanic conditions. This trend is confirmed by comparison with all well-documented marine and continental records from various latitudes available; in the Northern Hemisphere, in the Atlantic north of 20/sup 0/N, climate merged into more glacial conditions and in equatorial regions and in the Southern Hemisphere to more interglacial conditions. The data point to a more northern position of early Brunhes oceanic fronts and to an intensified atmosphere and ocean surface circulation in the Southern Hemisphere during that time, probably accompanied by a more zonal circulation in the Northern Hemisphere. The mid-Brunhes climatic change may have been forced by the orbital eccentricity cycle of 4.13 x 10/sup 5/ years. 42 references, 4 figures.

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

    Science.gov (United States)

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

    2015-12-01

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

  10. 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

    2016-01-01

    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. PMID:27198665

  11. 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.

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

    Directory of Open Access Journals (Sweden)

    X.-Y. Zheng

    2015-02-01

    Full Text Available 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 < 0.4 are selected and then categorized into six polluted types and three clean types, respectively. Each type represents different weather pattern associated with the combination of lower and upper atmospheric circulation. Generally, the uniform surface pressure field in East 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.

  13. Impact of atmospheric circulations on aerosol distributions in autumn over eastern China: observational evidence

    Science.gov (United States)

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

    2015-11-01

    Regional heavy pollution events in eastern China (110-122° E, 28-40° N) are causing serious environmental problems. In this study, the relationship between the degree of regional pollution and the patterns of large-scale atmospheric circulation over eastern China in October is investigated using 10-year (2001-2010) Terra/MODIS aerosol optical depth and NCEP reanalysis data by both case study and composite analysis. Eighteen polluted and 10 clean episodes are selected and categorised into six polluted types and three clean types respectively. Generally speaking, weather patterns such as a uniform surface pressure field in eastern China or a steady straight westerly in the middle troposphere, particularly when being at the rear of the anticyclone at 850 hPa, are typically responsible for heavy pollution events. Meanwhile, clean episodes occur when strong southeastward cold air advection prevails below the middle troposphere or air masses are transported from sea to land. Uniform descending motion prevails over the study region, trapping pollutants in the lower atmosphere. Therefore, the value of vertical velocity averaged from 1000 to 100 hPa and divergence of wind field in the lower troposphere are used in this study to quantify the diffusion conditions in each circulation type. The results reveal that it is often a clean episode when both the mean downward motion (larger than 2.56 × 10-2 Pa s-1) and the divergence of low-level winds (larger than 1.79 × 10-2 s-1) are strong. Otherwise, it is more likely to be a polluted episode.

  14. The east-west effect of the muon charge ratio at energies relevant to the atmospheric neutrino anomaly

    International Nuclear Information System (INIS)

    The measurements of the muon charge ratio representing the ratio of positive to negative atmospheric muons are performed using a small compact device, WILLI, by detecting the life time of the muons in different materials. Avoiding the difficulties of measurements with magnetic spectrometers, this method gives precise results on muon charge ratio especially in the low energy range relevant for the atmospheric neutrino anomaly. In the present configuration the detector is constructed as a rotatable device which permits measurements on different azimuthal directions. The preliminary results for the energy of incident muon in the range of 0.3-0.5 GeV/c, at mean zenith angle of 35 angle, evidence the east-west effect similarly found in neutrino measurements. (authors)

  15. Middle-atmospheric Ozone and HCl anomalies during the polar stratospheric warming 2010 observed by JEM/SMILES

    Science.gov (United States)

    Esmaeili Mahani, M.; Kreyling, D.; Sagawa, H.; Murata, I.; Kasaba, Y.; Kasai, Y.

    2012-12-01

    In this study we focused on investigating ozone and HCl variations and anomalies in the middle atmosphere due to the Stratospheric Sudden Warming (SSW) event of Arctic winter 2009-2010 using JEM/SMILES data. HCl anomalies in evolution of a SSW have been studied for the first time. SSWs are dramatic events in the winter stratosphere of the Northern Hemisphere where the deceleration or reversal of the eastward winds is accompanied by an increase of temperature by several tens of degrees. The main cause of this phenomenon is known to be the interaction of zonal mean flow with upward propagating transient planetary waves from the troposphere in mid-winter leading to a vortex displacement or break down. SSWs are dynamical disturbances found to affect both dynamics and chemical compositions of the middle atmosphere still having several different atmospheric features and behaviors to be studied. The Superconducting sub-Millimeter Limb Emission Sounder (SMILES) is a highly sensitive radiometer to observe various atmospheric compositions from upper troposphere to the mesosphere. SMILES was developed by the Japanese Aerospace eXploration Agency (JAXA) and the National Institute of Communications and Technology (NICT) located at the Japanese Experiment Module (JEM) on board the International Space Station (ISS). From October 2009 to April 2010, SMILES has accurately measured the vertical distributions and the diurnal variations of for example ozone and HCl with the accuracy of less than 8% and 5% in the middle atmosphere respectively. By using SMILES data the SSW event of 2010 was confirmed on 25-January categorized as a major, vortex displacement warming. After the SSW, ozone values enhanced up to 15-20% in mid-stratosphere due to the meridional transport from lower latitudes and weakening of the polar vortex. The mesospheric ozone response will also be demonstrated and discussed. For HCl, the total increase of 10% in Upper Stratosphere Lower Mesosphere (USLM) before the

  16. On the effect of nuclear interactions in neutrino reactions with oxygen targets and its role in atmospheric neutrino anomaly

    International Nuclear Information System (INIS)

    Atmospheric neutrinos are produced by interactions of the cosmic rays with the atmosphere's nuclei. The observed ratio of muonic to electronic neutrinos is smaller than the theoretical one (up to a factor 2), this is the so-called atmospheric anomaly. This anomaly could be linked to that observed in the solar neutrino experiments. The aim of this work is to evaluate the effects of nuclear correlations upon the interaction of the atmospheric neutrinos with the oxygen nuclei of the water Cherenkov detectors. The products of these interactions are detected and identified thanks to the light ring the produce. The events are classified according to the number of produced rings which is computed from the neutrino-oxygen event rates in each exclusive reaction channel. The interpretation of the experimental results has been up to now limited to the quasi-elastic nucleon and Δ channels but other reaction channels exist which can lead to identification problems. A special role is played by the non-pionic decay channels of the Δ resonance which induce single ring events that have not been considered so far. To calculate them we adopted the nuclear response formalism and started with a semi-classical approximation. This allowed us to take into account the nuclear correlations by solving exactly the RPA equations in the ring approximation. It was found that these correlations strongly modify the inclusive and exclusive neutrino-oxygen cross sections and absolute interaction rates while the ratio of the interaction rates μ/e is not very much affected. The analysis in the exclusive channels leads to the result that the number of pions predicted in the simulations is overestimated. In conclusion, this work has shown the importance of the nuclear correlations in the neutrino-oxygen interaction and its impact on the atmospheric neutrino anomaly. It goes beyond the usual quasi-elastic approximations and can be moreover extended to other target nuclei, such as iron, used in earlier

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

    Science.gov (United States)

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

    2015-12-01

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

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

    Science.gov (United States)

    Pokorná, Lucie; Pecho, Jozef; Faško, Pavol

    2013-04-01

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

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

    Directory of Open Access Journals (Sweden)

    Jia-Yuh Yu

    2010-01-01

    Full Text Available In this pa per, Asian dust storm activity from 1995 to 2006 and the associated atmospheric circulation are examined using SYNOP data and the NCEP/NCAR reanalysis atmospheric data. Observations show that the Gobi Desert is the most frequent birth place for severe dust events in Asia, accounting for pproximately 58% of the total percent age, followed by about 32% from the Taklamakan Desert and nearly 10% from the Loess Plateau. Climatologically, the existence of a large-scale dry zone over mid-latitudes of Asia during the Spring pro vides a favor able environment for the frequent occurrences of dust events and subsequent dust transport across Asia. To provide aquantitative measure of Asian dust storm activity, a _ activity _ (DAI is defined in this study. The time series of yearly DAI shows that Asian dust storm activity manifested marked interannual variations during 1995 ~ 2006. For an active year such as 2001, the magnitude of DAI (26986 is about a factor of 5 ~ 6 larger than that in 1997 (4569. Our analyses show that such variations are closely connected to the position of EAT (East Asian Trough, rather than to its strength. In a year when the EAT was shifted west ward (e.g., 2001, an east-west oriented low-high dipole appeared over Asia. This anomalous pressure dipole enhanced the prevailing north westerly flows over Mongolia and northern China, resulting in a drier-than-nor mal at mo sphere in favor of dust storm activity. On the contrary, in a year when the EAT was shifted east ward (e.g., 1997, a reverse dipole occurred, resulting in a wetter-than-nor mal at mo sphere disfavoring dust storm activity. A SVD (singular value decomposition analysis of the Asian synoptic circulation has shown that the connection between the pressure dipoles and the position of EAT is rather robust when dust storm activity is particularly strong (e.g., 2001, 2002, and 2006 or weak (e.g., 1997 and 1999. Analyzing a large number of trajectories de rived from the

  20. 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

    2015-08-01

    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.

  1. Aspects on interactions between mid- to high latitude atmospheric circulation and some surface processes

    International Nuclear Information System (INIS)

    The Arctic is a hot topic in Climate Research. A large number of signs of a warming Arctic Climate have been identified the latest years. This is of major concern in light of the increasing atmospheric content of greenhouse gases. The climate research community projects future warming of the climate in the high latitudes as a response to increased amounts of anthropogenic release of greenhouse gases since the pre-industrial era. The overall objectives of this work has been to study the mid- and high latitude climate and climate variability, and to evaluate how well some climate processes that contribute to determine the Arctic climate and variability are represented and simulated in climate models. A new data set of storm tracks trajectories and statistics over the Northern Hemisphere for the period 1948-2002 has been developed. The variability of the cyclones extending to the Nordic Seas is studied in particular, and it is found that both the number of storms and their intensity exhibits a strong decadal and interannual variability. The ocean volume transports into and out of the Nordic Seas shows a relatively close relation to the wintertime cyclone intensity and cyclone count. To have confidence in future projections of climate, it is necessary to evaluate how the model behaves in a climate regime different from modern day. To do this two model simulations of the last glacial maximum (LGM) was performed. The reconstructions of sea surface temperatures in the Nordic Seas in LGM differ from perennial sea ice cover to having open ocean during the summer. The large scale atmospheric circulation patterns of the two different climate reconstructions are studied. It is found that the perennial sea ice cover produces a circulation pattern which may be too zonal to support the existence of the large north Eurasian ice sheets. In the case with seasonally open ocean the air masses carries larger amounts of heat and moisture towards the ice sheets and represents a larger

  2. The Atmospheric Circulation and Observable Properties of Non-Synchronously Rotating Hot Jupiters

    CERN Document Server

    Rauscher, E

    2014-01-01

    We study the feasibility of observationally constraining the rotation rate of hot Jupiters, planets that are typically assumed to have been tidally locked into synchronous rotation. We use a three-dimensional General Circulation Model to solve for the atmospheric structure of two hot Jupiters (HD 189733b and HD 209458b), assuming rotation periods that are 0.5, 1, or 2 times their orbital periods (2.2 and 3.3 days, respectively), including the effect of variable stellar heating. We compare two observable properties: 1) the spatial variation of flux emitted by the planet, measurable in orbital phase curves, and 2) the net Doppler shift in transmission spectra of the atmosphere, which is tantalizingly close to being measurable in high-resolution transit spectra. Although we find little difference between the observable properties of the synchronous and non-synchronous models of HD 189733b, we see significant differences when we compare the models of HD 209458b. In particular, the slowly rotating model of HD 2094...

  3. 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.

  4. Climate-Induced Variability of Sea Level in Stockholm: Influence of Air Temperature and Atmospheric Circulation

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    This study is focused on climate-induced variation of sea level in Stockholm during 1873-1995. After the effect of the land uplift is removed, the residual is characterized and related to large-scale temperature and atmospheric circulation. The residual shows an overall upward trend, although this result depends on the uplift rate used. However, the seasonal distribution of the trend is uneven. There are even two months (June and August) that show a negative trend. The significant trend in August may be linked to fresh water input that is controlled by precipitation. The influence of the atmospheric conditions on the sea level is mainly manifested through zonal winds, vorticity and temperature. While the wind is important in the period January-May, the vorticity plays a main role during June and December. A successful linear multiple-regression model linking the climatic variables (zonal winds, vorticity and mean air temperature during the previous two months) and the sea level is established for each month. An independent verification of the model shows that it has considerable skill in simulating the variability.

  5. Discrepancies in tropical upper tropospheric warming between atmospheric circulation models and satellites

    International Nuclear Information System (INIS)

    Recent studies have examined tropical upper tropospheric warming by comparing coupled atmosphere–ocean global circulation model (GCM) simulations from Phase 3 of the Coupled Model Intercomparison Project (CMIP3) with satellite and radiosonde observations of warming in the tropical upper troposphere relative to the lower-middle troposphere. These studies showed that models tended to overestimate increases in static stability between the upper and lower-middle troposphere. We revisit this issue using atmospheric GCMs with prescribed historical sea surface temperatures (SSTs) and coupled atmosphere–ocean GCMs that participated in the latest model intercomparison project, CMIP5. It is demonstrated that even with historical SSTs as a boundary condition, most atmospheric models exhibit excessive tropical upper tropospheric warming relative to the lower-middle troposphere as compared with satellite-borne microwave sounding unit measurements. It is also shown that the results from CMIP5 coupled atmosphere–ocean GCMs are similar to findings from CMIP3 coupled GCMs. The apparent model-observational difference for tropical upper tropospheric warming represents an important problem, but it is not clear whether the difference is a result of common biases in GCMs, biases in observational datasets, or both. (letter)

  6. 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.

  7. Short ensembles: an efficient method for discerning climate-relevant sensitivities in atmospheric general circulation models

    Science.gov (United States)

    Wan, H.; Rasch, P. J.; Zhang, K.; Qian, Y.; Yan, H.; Zhao, C.

    2014-09-01

    This paper explores the feasibility of an experimentation strategy for investigating sensitivities in fast components of atmospheric general circulation models. The basic idea is to replace the traditional serial-in-time long-term climate integrations by representative ensembles of shorter simulations. The key advantage of the proposed method lies in its efficiency: since fewer days of simulation are needed, the computational cost is less, and because individual realizations are independent and can be integrated simultaneously, the new dimension of parallelism can dramatically reduce the turnaround time in benchmark tests, sensitivities studies, and model tuning exercises. The strategy is not appropriate for exploring sensitivity of all model features, but it is very effective in many situations. Two examples are presented using the Community Atmosphere Model, version 5. In the first example, the method is used to characterize sensitivities of the simulated clouds to time-step length. Results show that 3-day ensembles of 20 to 50 members are sufficient to reproduce the main signals revealed by traditional 5-year simulations. A nudging technique is applied to an additional set of simulations to help understand the contribution of physics-dynamics interaction to the detected time-step sensitivity. In the second example, multiple empirical parameters related to cloud microphysics and aerosol life cycle are perturbed simultaneously in order to find out which parameters have the largest impact on the simulated global mean top-of-atmosphere radiation balance. It turns out that 12-member ensembles of 10-day simulations are able to reveal the same sensitivities as seen in 4-year simulations performed in a previous study. In both cases, the ensemble method reduces the total computational time by a factor of about 15, and the turnaround time by a factor of several hundred. The efficiency of the method makes it particularly useful for the development of high

  8. An efficient method for discerning climate-relevant sensitivities in atmospheric general circulation models

    Science.gov (United States)

    Wan, H.; Rasch, P. J.; Zhang, K.; Qian, Y.; Yan, H.; Zhao, C.

    2014-04-01

    This paper explores the feasibility of an experimentation strategy for investigating sensitivities in fast components of atmospheric general circulation models. The basic idea is to replace the traditional serial-in-time long-term climate integrations by representative ensembles of shorter simulations. The key advantage of the proposed method lies in its efficiency: since fewer days of simulation are needed, the computational cost is less, and because individual realizations are independent and can be integrated simultaneously, the new dimension of parallelism can dramatically reduce the turnaround time in benchmark tests, sensitivities studies, and model tuning exercises. The strategy is not appropriate for exploring sensitivity of all model features, but it is very effective in many situations. Two examples are presented using the Community Atmosphere Model version 5. The first example demonstrates that the method is capable of characterizing the model cloud and precipitation sensitivity to time step length. A nudging technique is also applied to an additional set of simulations to help understand the contribution of physics-dynamics interaction to the detected time step sensitivity. In the second example, multiple empirical parameters related to cloud microphysics and aerosol lifecycle are perturbed simultaneously in order to explore which parameters have the largest impact on the simulated global mean top-of-atmosphere radiation balance. Results show that in both examples, short ensembles are able to correctly reproduce the main signals of model sensitivities revealed by traditional long-term climate simulations for fast processes in the climate system. The efficiency of the ensemble method makes it particularly useful for the development of high-resolution, costly and complex climate models.

  9. The east-west effect of the muon charge ratio at energies relevant to the atmospheric neutrino anomaly

    International Nuclear Information System (INIS)

    During the propagation of cosmic rays in the atmosphere, pions and kaons are produced by the interactions with atmospheric nuclei, pions and kaons are produced, which subsequently decay in muons and neutrinos. Considering the decay chains, it is obviously that the ratio of positive to negative atmospheric muons, called the muon charge ratio: Rν = μ+/μ-, maps the neutrino production and carries information on the hadronic interactions, used in the calculations of atmospheric neutrino. Measurements of the charge ratio of atmospheric muons at low energy reveal information of interest for the atmospheric neutrino anomaly. Measurements of East-West effect of the muon charge ratio allow to check different models for the hadronic interaction and investigate the influence of the Earth's magnetic field. The WILLI detector, built in IFIN-HH (Horia Hulubei National Institute for Physics and Nuclear Engineering) Bucharest measures the charge ratio by the effective life-time of the stopped muons. While positive muons undergo a free decay with natural lifetime, negative muons form muonic atoms, leading to a shorter lifetime of negative muons. The measured decay curve of all muons is a superposition of several decay laws, containing 3 detector dependent constants, accounting for the stopping power in the materials and the detection efficiencies, which are determined by extensive detector simulations using GEANT. The investigation of the directional dependence of the muon charge ratio has been started with measurements in the East and West direction at a mean zenithal angle of 35 angle. Introducing the azimuthal anisotropy AEW = (RW - RE) / ( RW + RE) with RW and RE being the muon charge ratios measured in East and West direction, the preliminary results show a pronounced East-West effect. (authors)

  10. 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.)

  11. Variable-resolution frameworks for the simulation of tropical cyclones in global atmospheric general circulation models

    Science.gov (United States)

    Zarzycki, Colin

    The ability of atmospheric General Circulation Models (GCMs) to resolve tropical cyclones in the climate system has traditionally been difficult. The challenges include adequately capturing storms which are small in size relative to model grids and the fact that key thermodynamic processes require a significant level of parameterization. At traditional GCM grid spacings of 50-300 km tropical cyclones are severely under-resolved, if not completely unresolved. This thesis explores a variable-resolution global model approach that allows for high spatial resolutions in areas of interest, such as low-latitude ocean basins where tropical cyclogenesis occurs. Such GCM designs with multi-resolution meshes serve to bridge the gap between globally-uniform grids and limited area models and have the potential to become a future tool for regional climate assessments. A statically-nested, variable-resolution option has recently been introduced into the Department of Energy/National Center for Atmospheric Research (DoE/NCAR) Community Atmosphere Model's (CAM) Spectral Element (SE) dynamical core. Using an idealized tropical cyclone test, variable-resolution meshes are shown to significantly lessen computational requirements in regional GCM studies. Furthermore, the tropical cyclone simulations are free of spurious numerical errors at the resolution interfaces. Utilizing aquaplanet simulations as an intermediate test between idealized simulations and fully-coupled climate model runs, climate statistics within refined patches are shown to be well-matched to globally-uniform simulations of the same grid spacing. Facets of the CAM version 4 (CAM4) subgrid physical parameterizations are likely too scale sensitive for variable-resolution applications, but the newer CAM5 package is vastly improved in performance at multiple grid spacings. Multi-decadal simulations following 'Atmospheric Model Intercomparison Project' protocols have been conducted with variable-resolution grids. Climate

  12. Atmospheric Circulation Characteristics Associated with the Onset of Asian Summer Monsoon

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The onset of the Asian summer monsoon has been a focus in the monsoon study for many years. In this paper, we study the variability and predictability of the Asian summer monsoon onset and demonstrate that this onset is associated with specific atmospheric circulation characteristics. The outbreak of the Asian summer monsoon is found to occur first over the southwestern part of the South China Sea (SCS)and the Malay Peninsula region, and the monsoon onset is closely related to intra-seasonal oscillations in the lower atmosphere. These intra-seasonal oscillations consist of two low-frequency vortex pairs, one located to the east of the Philippines and the other over the tropical eastern Indian Ocean. Prior to the Asian summer monsoon onset, a strong low-frequency westerly emerges over the equatorial Indian Ocean and the low-frequency vortex pair develops symmetrically along the equator. The formation and evolution of these low-frequency vortices are important and serve as a good indicator for the Asian summer monsoon onset. The relationship between the northward jumps of the westerly jet over East Asia and the Asian summer monsoon onset over SCS is investigated. It is shown that the northward jump of the westerly jet occurs twice during the transition from winter to summer and these jumps are closely related to the summer monsoon development. The first northward jump (from 25°-28°N to around 30°N) occurs on 8 May on average, about 7 days ahead of the summer monsoon onset over the SCS. It is found that the reverse of meridional temperature gradient in the upper-middle troposphere (500-200 hPa) and the enhancement and northward movement of the subtropical jet in the Southern Hemispheric subtropics are responsible for the first northward jump of the westerly jet.

  13. Atmospheric radiation measurement: A program for improving radiative forcing and feedback in general circulation models

    International Nuclear Information System (INIS)

    The Atmospheric Radiation Measurement (ARM) Program is a key element of the Department of Energy's (DOE's) global change research strategy. ARM represents a long-term commitment to conduct comprehensive studies of the spectral atmospheric radiative energy balance profile for a wide range of cloud conditions and surface types, and to develop the knowledge necessary to improve parameterizations of radiative processes under various cloud regimes for use in general circulation models (GCMs) and related models. The importance of the ARM program is a apparent from the results of model assessments of the impact on global climate change. Recent studies suggest that radiatively active trace gas emissions caused by human activity can lead to a global warming of 1.5 to 4.5 degrees Celsius and to important changes in water availability during the next century (Cess, et al. 1989). These broad-scale changes can be even more significant at regional levels, where large shifts in temperature and precipitation patterns are shown to occur. However, these analyses also indicate that considerable uncertainty exists in these estimates, with the manner in which cloud radiative processes are parameterized among the most significant uncertainty. Thus, although the findings have significant policy implications in assessment of global and regional climate change, their uncertainties greatly influence the policy debate. ARM's highly focused observational and analytical research is intended to accelerate improvements and reduce key uncertainties associated with the way in which GCMs treat cloud cover and cloud characteristics and the resulting radiative forcing. This paper summarizes the scientific context for ARM, ARM's experimental approach, and recent activities within the ARM program

  14. An Atmospheric General Circulation Model for Pluto with Predictions for New Horizons

    CERN Document Server

    Zalucha, Angela M

    2015-01-01

    Results are presented from a 3-D Pluto general circulation model (PGCM) that includes a subsurface model and volatile cycle. Conductive heating and cooling are present, as is non-local thermodynamic equilibrium (non-LTE) heating by methane at 2.3 and 3.3 microns, non-LTE cooling by heating by methane at 7.6 microns, and LTE CO rotational line cooling. This model is novel in that it has both detailed subsurface and atmospheric model components. Yet, there is little dependence of the model results on surface albedo, emissivity, or conductivity. Predictions are also provided for the Alice and REX instruments on New Horizons and for ground-based stellar occultations. Due to the weak temperature gradients, Alice (both solar and background star consultations) and REX are predicted to observe nearly the same temperature profiles on immersion and emersion. In the stratosphere, differences of up to 20 K are possible, while at higher altitudes (100-350 km), the differences are as large as 10 K. For both methane concent...

  15. Estimates of runoff using water-balance and atmospheric general circulation models

    Science.gov (United States)

    Wolock, D.M.; McCabe, G.J.

    1999-01-01

    The effects of potential climate change on mean annual runoff in the conterminous United States (U.S.) are examined using a simple water-balance model and output from two atmospheric general circulation models (GCMs). The two GCMs are from the Canadian Centre for Climate Prediction and Analysis (CCC) and the Hadley Centre for Climate Prediction and Research (HAD). In general, the CCC GCM climate results in decreases in runoff for the conterminous U.S., and the HAD GCM climate produces increases in runoff. These estimated changes in runoff primarily are the result of estimated changes in precipitation. The changes in mean annual runoff, however, mostly are smaller than the decade-to-decade variability in GCM-based mean annual runoff and errors in GCM-based runoff. The differences in simulated runoff between the two GCMs, together with decade-to-decade variability and errors in GCM-based runoff, cause the estimates of changes in runoff to be uncertain and unreliable.

  16. The role of aerosol in altering North Atlantic atmospheric circulation in winter and air-quality feedbacks

    Directory of Open Access Journals (Sweden)

    F. S. R. Pausata

    2014-09-01

    Full Text Available Numerical model scenarios of future climate depict a global increase in temperatures and changing precipitation patterns, driven by increasing greenhouse gas (GHG concentrations. Aerosol concentrations also play an important role in altering Earth's radiation budget and consequently surface temperature. Here, we use the general circulation aerosol model ECHAM5-HAM, coupled to a mixed layer ocean model, to investigate the impacts of future air pollution mitigation strategies in Europe on winter atmospheric circulation over the North Atlantic. We analyze the extreme case of a maximum feasible end-of-pipe reduction of aerosols in the near future (2030, in combination with increasing GHG concentrations. Our results show a more positive North Atlantic Oscillation (NAO mean state in the near future, together with a significant eastward shift of the southern centre of action of the sea level pressure (SLP. Moreover, we show a significantly increased blocking frequency over the western Mediterranean. By separating the aerosol and GHG impacts, our study suggests that the aerosol abatement in the near future may be the primary driver of such circulation changes. All these concomitant modifications of the atmospheric circulation over the Euro-Atlantic sector lead to more stagnant weather conditions that favor air pollutant accumulation in the Mediterranean, especially in the western sector. These changes in atmospheric circulation should be included in future air pollution mitigation assessments. Our results suggest that an evaluation of NAO changes in individual climate model simulations will allow an objective assessment of the role of changes in wintertime circulation on future air quality.

  17. Large-scale impact of Saharan dust on the North Atlantic Ocean circulation

    OpenAIRE

    Serra, N; Martínez Avellaneda, N.; Stammer, D.

    2014-01-01

    The potential for a dynamical impact of Saharan mineral dust on the North Atlantic Ocean large-scale circulation is investigated. To this end, an ocean general circulation model forced by atmospheric fluxes is perturbed by an idealized, seasonally varying, net shortwave flux anomaly, as it results from remote sensing observations of aerosol optical thickness representing Saharan dust load in the atmosphere. The dust dynamical impact on the circulation is assessed through a comparison between ...

  18. Supernovae and Single-Year Anomalies in the Atmospheric Radiocarbon Record

    CERN Document Server

    Dee, Michael; Miles, Daniel; Manning, Sturt; Miyake, Fusa

    2016-01-01

    Single-year spikes in radiocarbon production are caused by intense bursts of radiation from space. Supernovae emit both high-energy particle and electromagnetic radiation, but it is the latter that is most likely to strike the atmosphere all at once and cause a surge in 14C production. In the 1990s, it was claimed that the supernova in 1006 CE produced exactly this effect. With the 14C spikes in the years 775 and 994 CE now attributed to extreme solar events, attention has returned to the question of whether historical supernovae are indeed detectable using annual 14C measurements. Here, we combine new and existing measurements over six documented and putative supernovae, and conclude that no such astrophysical event has yet left a distinct imprint on the past atmospheric 14C record.

  19. Atmospheric forcing intensifies the effects of regional ocean warming on reef-scale temperature anomalies during a coral bleaching event

    Science.gov (United States)

    Zhang, Zhenlin; Falter, James; Lowe, Ryan; Ivey, Greg; McCulloch, Malcolm

    2013-09-01

    We investigate how local atmospheric conditions and hydrodynamic forcing contributed to local variations in water temperature within a fringing coral reef-lagoon system during the peak of a marine heat wave in 2010-2011 that caused mass coral bleaching across Western Australia. A three-dimensional circulation model Regional Ocean Modeling System (ROMS) with a built-in air-sea heat flux exchange module Coupled Ocean Atmosphere Experiment (COARE) was coupled with a spectral wave model Simulating Waves Nearshore (SWAN) to resolve the surface heat exchange and wave-driven reef circulation in Coral Bay, Ningaloo Reef. Using realistic oceanic and atmospheric forcing, the model predictions were in good agreement with measured time series of water temperature at various locations in the coral reef system during the bleaching event. Through a series of sensitivity analyses, we found that the difference in temperature between the reef and surrounding offshore waters (ΔT) was predominantly a function of both the daily mean net heat flux (Qnet>¯) and residence time, whereas diurnal variations in reef water temperature were dependent on the diurnal fluctuation in the net heat flux. We found that reef temperatures were substantially higher than offshore in the inner lagoon under normal weather conditions and over the entire reef domain under more extreme weather conditions (0.7°C-1.5°C). Although these temperature elevations were still less than that caused by the regional ocean warming (2°C-3°C), the arrival of peak seasonal temperatures in the summer of 2010-2011 (when net atmospheric heat fluxes were positive and abnormally high) caused substantially higher thermal stresses than would have otherwise occurred if offshore temperatures had reached their normal seasonal maxima in autumn (when net atmospheric heat fluxes were negative or cooling). Therefore, the degree heating weeks calculated based on offshore temperature substantially underestimated the thermal stresses

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

    Science.gov (United States)

    Rafkin, Scot; Soto, Alejandro; Michaels, Timothy

    2016-04-01

    A newly developed general circulation model (GCM) for Pluto is used to investigate the unexpected and highly heterogeneous distribution of nitrogen surface ice imaged by the New Horizons spacecraft on the surface of Pluto. The GCM is based on the GFDL Flexible Modeling System (FMS) dynamical core, solved on a discretized latitude/longitude horizontal grid and a pressure-based hybrid vertical coordinate. Model physics include a 3-band radiative scheme, molecular thermal conduction within the atmosphere, subsurface thermal 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, including non-local thermodynamic equilibrium effects. The subsurface conduction model assumes a water ice regolith. In the case of nitrogen surface ice deposition, additional super-surface layers are added above the water ice regolith to properly account for conductive energy flow through the nitrogen ice. 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 surface ice distribution on the surface of Pluto would be strongly controlled by the latitudinal temperature gradient resulting primarily from the slow seasonal variations of radiative-conductive equilibrium. 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. Furthermore, the circulation, and thus the transport of volatiles, was thought to be driven almost exclusively by sublimation and deposition flows (so-called "condensation 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 topography of substantial geologic diversity. To maintain such an ice distribution, the atmospheric circulation and

  1. Mechanisms for concurrent low-latitude circulation anomalies responsible for persistent extreme precipitation in the Yangtze River Valley

    Science.gov (United States)

    Chen, Yang; Zhai, Panmao

    2016-08-01

    Concurrent position shifts of the mid-level western Pacific subtropical high (WPSH) and the upper-level South Asia high (SAH) are regarded as significant precursors for persistent extreme precipitation events (PEPEs) in the Yangtze River Valley (YRV). By performing composite analyses, accountable vorticity genesis and dissipation are diagnosed based on a potential vorticity-diabatic heating theory. The results indicate that about 1 week preceding precipitation onset, a wave-like pattern of anomalous diabatic heating (Q) initiates its northwestward propagation from equatorial central Pacific. Subsequently, this wave-like pattern induces substantial changes in both horizontal and vertical structure of local Q along the propagating route. Forced negative vorticities in key areas result in the zonal approach between the SAH and the WPSH. During PEPEs, two thermal-induced vertical circulation cells take shape, with common strong ascent centered in the YRV. These anomalous cells are capable of self-maintaining for a few days via positive feedback processes. The WPSH and the SAH are therefore anchored in respective favorable positions for PEPEs. Simultaneously, descending motion of these two cells increases local solar radiation and decreases upward latent heat flux from surface, facilitating warmer underlying surface and swift accumulation of lower-level moisture. Correspondingly, enhanced heating to the north and rapid developing cyclone over warmer sea surface to the south combine to terminate above positive feedback processes. Finally, both the WPSH and the SAH retreat to their normal positions, accompanied by a quick decay of PEPEs.

  2. Physical conditions and nature of chemical anomalies in the atmosphere of Sirius A

    Science.gov (United States)

    Leushin, V. V.; Topilskaya, G. P.; Musaev, F. A.

    On the basis of the analysis of the observed equivalent line widths of Fe I, Fe II, Ti II in the spectra of alpha CMa and o Peg and calculation of abundances of these elements, oscillator strengths of the lines used are refined. With the improved oscillator strengths the iron and titanium abundances in the atmosphere of Sirius A are obtained with a higher accuracy than previously: lg N(Fe I) = 7.899 +/- 0.011, lg N(Fe II) = 7.908 +/- 0.010, lg N(Ti II) = 5.289 +/- 0.020. The improved accuracy allowed one to conclude that the surface magnetic field is absent in the atmosphere of Sirius A: H_s = 0+/-100 G. The equivalent widths of helium carbon and nitrogen lines of the red region of the spectrum are measured. The calculations of these lines with allowance for their blending with lines of other elements show normal helium abundance. From a comparison of features of alpha CMa and o Peg an assumption is made on possible reasons for the existence of the phenomenon of Am stars.

  3. Evaluation of Cloud Parameterizations in a High Resolution Atmospheric General Circulation Model Using ARM Data

    Energy Technology Data Exchange (ETDEWEB)

    Govindasamy, B; Duffy, P

    2002-04-12

    Typical state of the art atmospheric general circulation models used in climate change studies have horizontal resolution of approximately 300 km. As computing power increases, many climate modeling groups are working toward enhancing the resolution of global models. An important issue that arises when resolution of a model is changed is whether cloud and convective parameterizations, which were developed for use at coarser resolutions, will need to be reformulated or re-tuned. We propose to investigate this issue and specifically cloud statistics using ARM data. The data streams produced by highly instrumented sections of Cloud and Radiation Testbeds (CART) of ARM program will provide a significant aid in the evaluation of cloud and convection parameterization in high-resolution models. Recently, we have performed multiyear global-climate simulations at T170 and T239 resolutions, corresponding to grid cell sizes of 0.7{sup 0} and 0.5{sup 0} respectively, using the NCAR Community Climate Model. We have also a performed climate change simulation at T170. On the scales of a T42 grid cell (300 km) and larger, nearly all quantities we examined in T170 simulation agree better with observations in terms of spatial patterns than do results in a comparable simulation at T42. Increasing the resolution to T239 brings significant further improvement. At T239, the high-resolution model grid cells approach the dimensions of the highly instrumented sections of ARM Cloud and Radiation Testbed (CART) sites. We propose to form a cloud climatology using ARM data for its CART sites and evaluate cloud statistics of the NCAR Community Atmosphere Model (CAM) at higher resolutions over those sites using this ARM cloud climatology. We will then modify the physical parameterizations of CAM for better agreement with ARM data. We will work closely with NCAR in modifying the parameters in cloud and convection parameterizations for the high-resolution model. Our proposal to evaluate the cloud

  4. THREE-DIMENSIONAL ATMOSPHERIC CIRCULATION OF HOT JUPITERS ON HIGHLY ECCENTRIC ORBITS

    Energy Technology Data Exchange (ETDEWEB)

    Kataria, T.; Showman, A. P.; Lewis, N. K. [Department of Planetary Sciences and Lunar and Planetary Laboratory, The University of Arizona, Tucson, AZ 85721 (United States); Fortney, J. J. [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Marley, M. S.; Freedman, R. S., E-mail: tkataria@lpl.arizona.edu [NASA Ames Research Center 245-3, Moffett Field, CA 94035 (United States)

    2013-04-10

    Of the over 800 exoplanets detected to date, over half are on non-circular orbits, with eccentricities as high as 0.93. Such orbits lead to time-variable stellar heating, which has major implications for the planet's atmospheric dynamical regime. However, little is known about the fundamental dynamical regime of such planetary atmospheres, and how it may influence the observations of these planets. Therefore, we present a systematic study of hot Jupiters on highly eccentric orbits using the SPARC/MITgcm, a model which couples a three-dimensional general circulation model (the MITgcm) with a plane-parallel, two-stream, non-gray radiative transfer model. In our study, we vary the eccentricity and orbit-average stellar flux over a wide range. We demonstrate that the eccentric hot Jupiter regime is qualitatively similar to that of planets on circular orbits; the planets possess a superrotating equatorial jet and exhibit large day-night temperature variations. As in Showman and Polvani, we show that the day-night heating variations induce momentum fluxes equatorward to maintain the superrotating jet throughout its orbit. We find that as the eccentricity and/or stellar flux is increased (corresponding to shorter orbital periods), the superrotating jet strengthens and narrows, due to a smaller Rossby deformation radius. For a select number of model integrations, we generate full-orbit light curves and find that the timing of transit and secondary eclipse viewed from Earth with respect to periapse and apoapse can greatly affect what we see in infrared (IR) light curves; the peak in IR flux can lead or lag secondary eclipse depending on the geometry. For those planets that have large temperature differences from dayside to nightside and rapid rotation rates, we find that the light curves can exhibit 'ringing' as the planet's hottest region rotates in and out of view from Earth. These results can be used to explain future observations of eccentric

  5. 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.

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

    Science.gov (United States)

    Kim, Jin-Ah; Byun, Hi-Ryong

    2016-02-01

    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.

  7. 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.)

  8. Influence of high-resolution surface databases on the modeling of local atmospheric circulation systems

    Science.gov (United States)

    Paiva, L. M. S.; Bodstein, G. C. R.; Pimentel, L. C. G.

    2013-12-01

    Large-eddy simulations are performed using the Advanced Regional Prediction System (ARPS) code at horizontal grid resolutions as fine as 300 m to assess the influence of detailed and updated surface databases on the modeling of local atmospheric circulation systems of urban areas with complex terrain. Applications to air pollution and wind energy are sought. These databases are comprised of 3 arc-sec topographic data from the Shuttle Radar Topography Mission, 10 arc-sec vegetation type data from the European Space Agency (ESA) GlobCover Project, and 30 arc-sec Leaf Area Index and Fraction of Absorbed Photosynthetically Active Radiation data from the ESA GlobCarbon Project. Simulations are carried out for the Metropolitan Area of Rio de Janeiro using six one-way nested-grid domains that allow the choice of distinct parametric models and vertical resolutions associated to each grid. ARPS is initialized using the Global Forecasting System with 0.5°-resolution data from the National Center of Environmental Prediction, which is also used every 3 h as lateral boundary condition. Topographic shading is turned on and two soil layers with depths of 0.01 and 1.0 m are used to compute the soil temperature and moisture budgets in all runs. Results for two simulated runs covering the period from 6 to 7 September 2007 are compared to surface and upper-air observational data to explore the dependence of the simulations on initial and boundary conditions, topographic and land-use databases and grid resolution. Our comparisons show overall good agreement between simulated and observed data and also indicate that the low resolution of the 30 arc-sec soil database from United States Geological Survey, the soil moisture and skin temperature initial conditions assimilated from the GFS analyses and the synoptic forcing on the lateral boundaries of the finer grids may affect an adequate spatial description of the meteorological variables.

  9. Effect of East Asia summer blocking on the atmospheric circulation over the region

    Science.gov (United States)

    Ahn, Joong-Bae; Park, Yong-Jun

    2015-04-01

    The influence of the boreal summer blocking on atmospheric circulation in East Asia was examined. The summer blocking occurred mostly in North Europe, Ural region, Sea of Okhotsk (OK), and northeastern Pacific. The summer blocking was the major mode in these four regions according to principal component analysis using 500 hPa geopotential heights. Among the four blocking regions, OK blocking frequencies (OK BFs) showed negative and positive correlations with summer temperature and precipitation of Northeast Asia centered around the East Sea/Sea of Japan, respectively. In particular, the OK BF had a statistically significant correlation coefficient of -0.54 with summer temperatures in the Korean Peninsula. This indicates that the summer temperature and precipitation in this region were closely related to the OK blocking. According to the composite analysis for the years of higher-than-average BF (positive BF years), the OK High became stronger and expanded, while the North Pacific High was weakened over the Korean Peninsula and Japan and an anomalously deep trough was developed in the upper layer (200 hPa). As the cool OK High expanded, the temperature decreased over Northeast Asia centered around the East Sea/Sea of Japan and the lower level (850 hPa) air converged cyclonically, resulting in the increased precipitation, which induced the divergence in the upper layer and thereby strengthened the jet stream. Thus, the boreal summer OK blocking systematically influencing the area as the most dominant mode. Acknowledgements This work was carried out with the support of Rural Development Administration Cooperative Research Program for Agriculture Science and Technology Development under grant project PJ009353 and Korea Meteorological Administration Research and Development Program under grant CATER 2012-3100, Republic of Korea.

  10. Reconstructions of spring/summer precipitation for the Eastern Mediterranean from tree-ring widths and its connection to large-scale atmospheric circulation

    Energy Technology Data Exchange (ETDEWEB)

    Touchan, Ramzi; Funkhouser, Gary; Hughes, Malcolm K. [The University of Arizona, Laboratory of Tree-Ring Research, Tucson, AZ (United States); Xoplaki, Elena; Luterbacher, Juerg [University of Bern, Institute of Geography and NCCR Climate, Bern (Switzerland); Erkan, Nesat [Southwest Anatolia Forest Research Institute (SAFRI), Antalya (Turkey); Akkemik, Uenal [University of Istanbul, Faculty of Forestry, Department of Forest Botany, Bahcekoey-Istanbul (Turkey); Stephan, Jean [Ministry of Agriculture, Forestry Department, Beirut (Lebanon)

    2005-07-01

    This study represents the first large-scale systematic dendroclimatic sampling focused on developing chronologies from different species in the eastern Mediterranean region. Six reconstructions were developed from chronologies ranging in length from 115 years to 600 years. The first reconstruction (1885-2000) was derived from principal components (PCs) of 36 combined chronologies. The remaining five, 1800-2000, 1700-2000, 1600-2000, 1500-2000 and 1400-2000 were developed from PCs of 32, 18, 14, 9, and 7 chronologies, respectively. Calibration and verification statistics for the period 1931-2000 show good levels of skill for all reconstructions. The longest period of consecutive dry years, defined as those with less than 90% of the mean of the observed May-August precipitation, was 5 years (1591-1595) and occurred only once during the last 600 years. The longest reconstructed wet period was 5 years (1601-1605 and 1751-1755). No long term trends were found in May-August precipitation during the last few centuries. Regression maps are used to identify the influence of large-scale atmospheric circulation on regional precipitation. In general, tree-ring indices are influenced by May-August precipitation, which is driven by anomalous below (above) normal pressure at all atmospheric levels and by convection (subsidence) and small pressure gradients at sea level. These atmospheric conditions also control the anomaly surface air temperature distribution which indicates below (above) normal values in the southern regions and warmer (cooler) conditions north of around 40 N. A compositing technique is used to extract information on large-scale climate signals from extreme wet and dry summers for the second half of the twentieth century and an independent reconstruction over the last 237 years. Similar main modes of atmospheric patterns and surface air temperature distribution related to extreme dry and wet summers were identified both for the most recent 50 years and the last

  11. Links between atmospheric circulation and surface air temperature in climate models in control climate and future scenarios

    Czech Academy of Sciences Publication Activity Database

    Plavcová, Eva; Kyselý, Jan

    Bern: Swiss Climate Research, 2011, s. 84-85. [International NCCR Climate Summer School "Climate Change, Extremes and Ecosystem Services" /10./. Grindelwald (CH), 04.09.2001-09.09.2011] R&D Projects: GA ČR GAP209/10/2265 Institutional research plan: CEZ:AV0Z30420517 Keywords : regional climate models * air temperature * atmospheric circulation * future climate change scenarios Subject RIV: DG - Athmosphere Sciences, Meteorology

  12. Long-term trends of atmospheric circulation over Europe: Comparison of three secular datasets and six recent reanalyses

    Czech Academy of Sciences Publication Activity Database

    Cahynová, Monika

    Prague: International Union of Geodesy and Geophysics, 2015. M13p-191. [Earth and Environmental Sciences for Future Generations. General Assembly of International Union of Geodesy and Geophysics /26./. 22.06.2015-02.07.2015, Prague] Institutional support: RVO:68378289 Keywords : atmospheric circulation * climatic trends Subject RIV: DG - Athmosphere Sciences, Meteorology http://www.iugg2015prague.com/abstractcd/data/HtmlApp/main.html#0

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

    Science.gov (United States)

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

    2015-08-01

    Using the daily records derived from the synoptic weather stations and the NCEP/NCAR and ERA-Interim reanalysis data, the variability of the winter 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.

  14. Atmospheric circulation patterns associated with the variability of River Ammer floods: evidence from observed and proxy data

    Science.gov (United States)

    Rimbu, Norel; Czymzik, Markus; Ionita, Monica; Lohmann, Gerrit; Brauer, Achim

    2016-02-01

    The relationship between the frequency of River Ammer floods (southern Germany) and atmospheric circulation variability is investigated based on observational Ammer River discharge data back to 1926 and a flood layer time series from varved sediments of the downstream Lake Ammer for the pre-instrumental period back to 1766. A composite analysis reveals that, at synoptic timescales, observed River Ammer floods are associated with enhanced moisture transport from the Atlantic Ocean and the Mediterranean towards the Ammer region, a pronounced trough over western Europe as well as enhanced potential vorticity at upper levels. We argue that this synoptic-scale configuration can trigger heavy precipitation and floods in the Ammer region. Interannual to multidecadal increases in flood frequency, as detected in the instrumental discharge record, are associated with a wave train pattern extending from the North Atlantic to western Asia, with a prominent negative center over western Europe. A similar atmospheric circulation pattern is associated with increases in flood layer frequency in the Lake Ammer sediment record during the pre-instrumental period. We argue that the complete flood layer time series from Lake Ammer sediments covering the last 5500 years contains information about atmospheric circulation variability on interannual to millennial timescales.

  15. The atmospheric circulation patterns influencing the frequency of spring sand-dust storms in the Tarim Basin

    Institute of Scientific and Technical Information of China (English)

    HongJun Li; XinHua Yang; Yong Zhao; MinZhong Wang; Wen Huo

    2014-01-01

    Using NCEP/NCAR reanalysis data and the sand-storm frequency data from 37 weather stations in the Tarim Basin for the period 1961-2009, the relationship between the frequency of spring sandstorms in the Tarim Basin and the associated atmospheric circu-lation patterns is analyzed in this study. We found significantly negative correlations between sandstorm frequency and the 500-hPa geopotential height over the Paris Basin and midwestern Mongolia, while there were positive correlations over the Ural River region. The rising of the 500-hPa geopotential height in midwestern Mongolia and its falling over the Ural region corre-spond to a weakening of the large-scale wave patterns in the Eurasian region, which directly causes the frequency of the sand-dust storms in the Tarim Basin to decline. Also, the abrupt decline in the spring sandstorm frequency in the Tarim Basin observed in the last half-century is associated with profound changes in the atmospheric circulation in these key regions. At the interannual scale, the strengthened cyclonic atmospheric circulation patterns in the western part of Mongolia and the anticyclonic patterns over the East European plains at 500-hPa geopotential height, are responsible for frequent sandstorm occurrences in the Tarim Basin.

  16. A global satellite view of the seasonal distribution of mineral dust and its correlation with atmospheric circulation

    Science.gov (United States)

    Alizadeh-Choobari, O.; Sturman, A.; Zawar-Reza, P.

    2014-12-01

    Aerosols make a considerable contribution to the climate system through their radiative and cloud condensation nuclei effects, which underlines the need for understanding the origin of aerosols and their transport pathways. Seasonal distribution of mineral dust around the globe and its correlation with atmospheric circulation is investigated using satellite data, and meteorological data from ECMWF. The most important sources of dust are located in North Africa, the Middle East and Southwest Asia with an observed summer maximum, and East Asia with a spring peak. Maximum dust activity over North Africa and the Middle East in summer is attributed to dry convection associated with the summertime low-pressure system, while unstable weather and dry conditions are responsible for the spring peak in dust emission in East Asia. Intercontinental transport of mineral dust by atmospheric circulation has been observed, including trans-Atlantic transport of North African dust, trans-Pacific transport of Asian dust, and transport of dust from the Middle East across the Indian Ocean. The extent of African dust over the Atlantic Ocean and its latitudinal variation with season is related to the large-scale atmospheric circulation, including seasonal changes in the position of the intertropical convergence zone (ITCZ) and variation of wind patterns. North African aerosols extend over longer distances across the North Atlantic in summer because of greater dust emission, an intensified easterly low level jet (LLJ) and strengthening of the Azores-Bermuda anticyclonic circulation. Transport of East Asian aerosol is facilitated by the existence of a LLJ that extends from East Asia to the west coast of North America.

  17. 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.

  18. Methane anomalies in seawaters of the Ragay Gulf, Philippines: methane cycling and contributions to atmospheric greenhouse gases

    International Nuclear Information System (INIS)

    The vertical distribution of methane has been measured in the water column of a semi-enclosed basin, the Ragay Gulf, in the Philippines archipelago. The methane distribution is characterised by unusual mid-water and bottom-water plumes, between 80 and 100 m thick. The plumes are confined to water depths between about 100 and 220 m. where the temperature-depth (a proxy for seawater density) gradient is steepest. Plumes of high methane are 'trapped' within the main thermocline; these are local features, persisting over kilometre-scale distances. Geochemical and geological evidence suggests that the elevated methane concentrations are thermogenic in origin (although an oxidised biogenic origin cannot be ruled out for some of the methane anomalies), and have migrated from the sea floor into the overlying water. The mid and bottom-water methane maxima support fluxes of methane from depth into surface waters and, subsequently, from the oceans to the atmosphere. The average supersaturation of methane in the top 5 m of the sea, at nine locations, was 206±16.5%; range 178-237%. The average estimated sea-air flux was 101 nmole.cm-2.y-1 and probably represents a minimum flux, because of low wind speeds of <10 knots. These fluxes, we suggest, are supported by seepage from the sea floor and represent naturally occurring fluxes of mostly fossil methane (in contrast to anthropogenic fossil methane), from the sea to the atmosphere. The estimated minimum fluxes of naturally occurring fossil methane are comparable to those biogenic fluxes measured elsewhere in the surface oceans, but are less than those naturally occurring methane inputs from sediments of the Barents Sea. Ragay Gulf fluxes are also less than anthropogenic fluxes measured in areas of petroleum exploration and development, such as the Texas and Louisiana, USA shelf areas

  19. 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.

  20. Atmospheric response in summer linked to recent Arctic sea ice loss

    OpenAIRE

    Petrie, Ruth E.; Shaffrey, Len C.; Sutton, Rowan T.

    2015-01-01

    Since 2007 a large decline in Arctic sea ice has been observed. The large-scale atmospheric circulation response to this decline is investigated in ERA-Interim reanalyses and HadGEM3 climate model experiments. In winter, post-2007 observed circulation anomalies over the Arctic, North Atlantic and Eurasia are small compared to interannual variability. In summer, the post-2007 observed circulation is dominated by an anticyclonic anomaly over Greenland which has a large signal-to-noise ratio. Cl...

  1. 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.

  2. The main characteristics of atmospheric circulation over East-Central Europe from 1871 to 2010

    Science.gov (United States)

    Bartoszek, Krzysztof

    2016-05-01

    The main objective of the paper concerns the determination of the annual and multi-annual variability of air flow over East-Central Europe in the period 1871-2010. Daily mean sea-level pressure and values of physical quantities provided the basis for distinguishing 27 circulation types, i.e., eight directional cyclonic, transitional, and anticyclonic types, and one non-directional cyclonic, anticyclonic, and an undefined type. Over the area of East-Central Europe, the highest frequency is recorded for air flow from the western sector, with a maximum in the period from December to January. In spring, a higher than average frequency of cyclonic and easterly circulation is observed, and in summer—anticyclonic and northerly. Increased zonal circulation was recorded in the years 1910-1930, and particularly after 1970, and eastern at the end of the nineteenth century and in the 1930s and 1940s. An increase in the frequency of days with non-directional anticyclonic type and westerly air flow, and a simultaneous decrease in frequency of days with south-easterly and easterly circulation were observed throughout the study period. Among the three classes of circulation types, the highest persistence (particularly in winter) was recorded for anticyclonic types, i.e., when the high pressure system occurred over the Scandinavian Peninsula or East Europe.

  3. Sensitivity of the sea circulation to the atmospheric forcing in the Sicily Channel

    Science.gov (United States)

    Omrani, Hiba; Arsouze, Thomas; Béranger, Karine; Boukthir, Moncef; Drobinski, Philippe; Lebeaupin-Brossier, Cindy; Mairech, Hanen

    2016-01-01

    We investigate the sensitivity of the sea surface circulation in the Sicily Channel to surface winds, using a 15-year long (1994-2008) air-sea coupled numerical simulation. Analysis is based on the clustering of six main wind regimes over the Sicily Channel domain. The analysis of the corresponding sea current clusters shows that sea circulation in this area is sensitive to surface wind patterns. This wind modulates the strength of the two main branches of the sea circulation in the Sicily Channel (i.e. the Atlantic Tunisian Current and the Atlantic Ionian Stream). The modulation of these two currents depends on the wind regime, and displays a strong seasonal variability. It is also shown that the sea circulation in the Sicily Channel is strongly controlled by the thermohaline circulation and the bathymetry (geostrophic current). However, the contribution to the total current of its ageostrophic component forced by the surface winds is significant, with a correlation coefficient varying from 0.3 to 0.7.

  4. The influence of atmospheric circulation on the air pollution concentration and temperature inversion in Sosnowiec. Case study

    Directory of Open Access Journals (Sweden)

    Widawski Artur

    2015-06-01

    Full Text Available Sosnowiec is located in the Katowice Region, which is the most urbanized and industrialized region in Poland. Urban areas of such character favor enhancement of pollution concentration in the atmosphere and the consequent emergence of smog. Local meteorological and circulation conditions significantly influence not only on the air pollution level but also change air temperature considerably in their centers and immediate vicinities. The synoptic situation also plays the major role in dispersal and concentration of air pollutants and changes in temperature profile. One of the most important are the near-ground (100 m inversions of temperature revealed their highest values on clear winter days and sometimes stay still for the whole day and night. Air temperature inversions in Sosnowiec occur mainly during anticyclone stagnation (Ca-anticyclone centre and Ka-anticyclonic ridge and in anticyclones with air advection from the south and southwest (Sa and SWa which cause significantly increase of air pollution values. The detailed evaluation of the influence of circulation types on the appearance of a particular concentration of pollutants carried out in this work has confirmed the predominant influence of individual circulation types on the development of air pollution levels at the Katowice region. This paper presents research case study results of the thermal structure of the near-ground atmospheric layer (100 m and air pollution parameters (PM10, SO2, NO, NO2 changes in selected days of 2005 year according to regional synoptic circulation types. The changes in urban environment must be taken into account in analyses of multiyear trends of air temperature and air conditions on the regional and global scales.

  5. Long-term trends in the frequency of atmospheric circulation types in European regions

    Science.gov (United States)

    Cahynová, M.; Huth, R.

    2009-04-01

    We have analyzed long-term linear trends in the seasonal frequency of circulation types in the period 1957-2002 using 73 circulation classifications arising from the COST733 Action: 65 objective catalogues in Europe and 11 European regions, and 8 subjective and "objectivized" catalogues in Central Europe. The objective catalogues are based on the same gridded climatic data (ECMWF ERA40), but they differ in the classification method used and in the number of circulation types. In the objective catalogues the proportion of days that belong to circulation types with significant trends in seasonal frequency is mostly very low except for Central and Eastern Europe in winter and the Mediterranean in winter and summer. Generally, the magnitude of trends is the highest in winter. In the Mediterranean in summer the types with significant trends in frequency are the prevailing ones, whereas in other seasons and regions there is no such preference for the total occurrence of the circulation type to have a significant trend. In the subjective catalogues there is a substantial proportion of circulation types with significant trends in frequency in all seasons. The magnitude of trends is also very similar within the four seasons. Whether these long-term trends in the subjective catalogues reflect real climatic changes or result from manual data evaluation is still an open question. The research is conducted within the COST733 Action "Harmonisation and Applications of Weather Types Classifications for European Regions". The Czech participation in it is supported by the Ministry of Education, Youth, and Sports of the Czech Republic, contract OC115.

  6. Seasonal variations in the frequency of atmospheric circulation types in European regions

    Science.gov (United States)

    Cahynova, Monika; Huth, Radan

    2010-05-01

    We propose two versions of an "index of seasonality" to study the annual course in the relative frequency of circulation types in several objective and subjective classifications from the COST733 database. The objective classifications have been developed for twelve European regions (domains D00-D11) in the period 1957-2002 and have fixed numbers of types (9, 18, and 27). Both indices are based on the long-term monthly relative frequency of individual circulation types. For each type we indicate the months with the highest and the lowest relative frequency and calculate their difference (range). The first index - "average seasonality" - is an average of the ranges of all types within a given classification. It is anti-correlated with the number of types - a higher number of types means a lower average seasonality. The second index - "maximum seasonality" - only takes into account the circulation type with the highest range (that is, the type with the most pronounced annual course). This index removes the dependence on the number of circulation types in some of the used classifications. Seasonal variations in the relative frequency of circulation types based on the two indices are generally the highest in the eastern Mediterranean (D11) and in whole Europe (D00). The lowest seasonality is found over the British Isles (D04) and Iceland (D01). There are large differences in the seasonality in the individual classifications, because the degree to which the classification identifies the natural seasonal circulation patterns strongly depends on the classification algorithm used. The research is conducted within the COST733 Action "Harmonisation and Applications of Weather Types Classifications for European Regions". The Czech participation in it is supported by the Ministry of Education, Youth, and Sports of the Czech Republic, contract OC115.

  7. 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

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

    OpenAIRE

    Voigt, A.; D. S. Abbot; Pierrehumbert, R. T.; J. Marotzke

    2011-01-01

    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 t...

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

    Czech Academy of Sciences Publication Activity Database

    Plavcová, Eva; Kyselý, Jan

    2012-01-01

    Roč. 39, 7-8 (2012), s. 1681-1695. ISSN 0930-7575 R&D Projects: GA ČR GAP209/10/2265 Grant ostatní: ENSEMBLES: EU-FP6(XE) 505539 Institutional support: RVO:68378289 Keywords : Regional climate models * Global climate models * Atmospheric circulation * Surface air temperature * ENSEMBLES * Central Europe Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 4.231, year: 2012 http://link.springer.com/article/10.1007%2Fs00382-011-1278-8#

  10. 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.

  11. Interpreting the atmospheric circulation trend during the last half of the 20th century: Application of an adjoint model

    OpenAIRE

    S. Blessing; Greatbatch, Richard; K. Fraedrich; Lunkeit, F.

    2008-01-01

    A tangent linear adjoint for a low-resolution dynamical model of the atmosphere is used to derive the optimal forcing perturbations for all state variables such that after a specified lead time the model response has a given projection, in terms of an energy norm, on the pattern associated with the 51-yr trend in the Northern Hemisphere winter tropospheric circulation, 1948/49–1998/99. A feature of the derived forcing sensitivity is a Rossby wave–like feature that emanates from the western tr...

  12. 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 ( level, and is then accompanied by a reduction (increase) of horizontal advection and vertical convection (relative humidity) in the lowest troposphere and a reduced boundary layer height in BTH and its neighboring areas, which are favorable for the formation of haze 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.

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

    Directory of Open Access Journals (Sweden)

    Dörthe Handorf

    2012-11-01

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

  14. Synoptic-climatological evaluation of the classifications of atmospheric circulation patterns over Europe

    Czech Academy of Sciences Publication Activity Database

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

    -, - (2016). ISSN 0899-8418 R&D Projects: GA ČR(CZ) GPP209/12/P811 Institutional support: RVO:68378289 Keywords : circulation types * classification * synoptic climatology * COST733 Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 3.157, year: 2014 http://onlinelibrary.wiley.com/doi/10.1002/joc.4546/full

  15. Response in atmospheric circulation and sources of Greenland precipitation to glacial boundary conditions

    DEFF Research Database (Denmark)

    Langen, Peter Lang; Vinther, Bo Møllesøe

    cooler tropics and less sea ice. The occurrence of such a shift depends chiefly on the SST reconstruction and not on the existence of the large northern hemisphere glacial ice sheets. The influence of these circulation changes on important factors for ice core interpretation such as precipitation...

  16. Documentation of a ground hydrology parameterization for use in the GISS atmospheric general circulation model

    Science.gov (United States)

    Lin, J. D.; Aleano, J.; Bock, P.

    1978-01-01

    The moisture transport processes related to the earth's surface relevant to the ground circulation model GCM are presented. The GHM parametrizations considered are: (1) ground wetness and soil parameters; (2) precipitation; (3) evapotranspiration; (4) surface storage of snow and ice; and (5) runout. The computational aspects of the GHM using computer programs and flow charts are described.

  17. 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...

  18. 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

  19. 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

  20. Statistical Analysis of Categorical Time Series of Atmospheric Elementary Circulation Mechanisms - Dzerdzeevski Classification for the Northern Hemisphere

    Science.gov (United States)

    Brenčič, Mihael

    2016-01-01

    Northern hemisphere elementary circulation mechanisms, defined with the Dzerdzeevski classification and published on a daily basis from 1899–2012, are analysed with statistical methods as continuous categorical time series. Classification consists of 41 elementary circulation mechanisms (ECM), which are assigned to calendar days. Empirical marginal probabilities of each ECM were determined. Seasonality and the periodicity effect were investigated with moving dispersion filters and randomisation procedure on the ECM categories as well as with the time analyses of the ECM mode. The time series were determined as being non-stationary with strong time-dependent trends. During the investigated period, periodicity interchanges with periods when no seasonality is present. In the time series structure, the strongest division is visible at the milestone of 1986, showing that the atmospheric circulation pattern reflected in the ECM has significantly changed. This change is result of the change in the frequency of ECM categories; before 1986, the appearance of ECM was more diverse, and afterwards fewer ECMs appear. The statistical approach applied to the categorical climatic time series opens up new potential insight into climate variability and change studies that have to be performed in the future. PMID:27116375

  1. The variability of extreme temperatures and their relationship with atmospheric circulation: the contribution of applying linear and quadratic models

    Science.gov (United States)

    Savić, Stevan; Milovanović, Boško; Lužanin, Zorana; Lazić, Lazar; Dolinaj, Dragan

    2015-08-01

    This paper presents an analysis of the homogenised mean maximum ( T max) and minimum ( T min) temperatures. The data used in the analysis were collected at eight stations in the Autonomous Province of Vojvodina (Serbia) during the 1949-2008 period. The trends obtained from the slopes of the regression lines using the least square method show 0.9 °C/60 years for T max and 1.1 °C/60 years for T min; the non-parametric Mann-Kendall test was used to determine the statistically significant increasing trends of these two extreme parameters. In this paper, we analyse the influence of the Vangengeim-Girs classification of atmospheric circulation on the T max and T min trends in the Autonomous Province of Vojvodina (Serbia) using linear and quadratic models based on the least square method. Linear stepwise regression and the forward method reveal the highest dependence of T max and T min when the W or E circulation types are included in the model. Non-linear models show a greater contribution of T max and T min at W, E and C circulation types, respectively. The correction of the variance contribution of quadratic models ranges from approximately 16 to 44 % for T max and 32 to 38 % for T min.

  2. 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.

  3. 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.

  4. 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.

  5. 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

    2008-05-01

    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 yr and show that the model, which is predominantly driven by solar insolation patterns, fails to produce the reconstructed mid-Holocene dry and warm period in Scandinavia. As an alternative explanation for the reconstructed climate, we hypothesize 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 hypothesis 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. It is concluded 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.

  6. 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.

  7. 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

  8. On the feedback of the winter NAO‑driven sea ice anomalies

    OpenAIRE

    García-Serrano, Javier; Frankignoul, C.

    2015-01-01

    Satellite-derived sea-ice concentration (SIC) and re-analysed atmospheric data are used to analyse the potential feedback of the North Atlantic Oscillation (NAO)-driven sea-ice anomalies in winter onto the atmosphere during 1979–2013. A maximum covariance analysis shows that this feedback can be detected with monthly data. When SIC leads, the covariability between Atlantic SIC and the Euro-Atlantic atmospheric circulation in February is statistically significant, but shows intraseasonal diffe...

  9. Influence of SST from Pacific and Atlantic Ocean and atmospheric circulation in the precipitation regime of basin from Brazilian SIN

    Science.gov (United States)

    Custodio, M. D.; Ramos, C. G.; Madeira, P.; de Macedo, A. L.

    2013-12-01

    The South American climate presents tropical, subtropical and extratropical features because of its territorial extension, being influenced by a variety of dynamical systems with different spatial and temporal scales which result in different climatic regimes in their subregions. Furthermore, the precipitation regime in South America is influenced by low-frequency phenomena as El Niño-Southern Oscillation (ENSO), the Atlantic dipole and the Madden Julian Oscilation (MJO), in other words, is directly influenced by variations of the Sea Surface Temperature (SST). Due to the importance of the precipitation for many sectors including the planning of productive activities, such as agriculture, livestock and hydropower energy, many studies about climate variations in Brazil have tried to determine and explain the mechanisms that affect the precipitation regime. However, because of complexity of the climate system, and consequently of their impacts on the global precipitation regime, its interactions are not totally understood and therefore misrepresented in numerical models used to forecast climate. The precipitation pattern over hydrographic basin which form the Brasilian National Interconnected System (Sistema Interligado Nacional-SIN) are not yet known and therefore the climate forecast of these regions still presents considerable failure that need to be corrected due to its economic importance. In this context, the purpose here is to determine the precipitation patterns on the Brazilian SIN, based on SST and circulation observed data. In a second phase a forecast climate model for these regions will be produced. In this first moment 30 years (1983 to 2012) of SST over Pacific and Atlantic Ocean were analyzed, along with wind in 850 and 200 hPa and precipitation observed data. The precipitation patterns were analyzed through statistical analyses for interannual (ENSO) and intraseasonal (MJO) anomalies for these variables over the SIN basin. Subsequently, these

  10. 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

  11. 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.

  12. The influence of solar activity on action centres of atmospheric circulation in North Atlantic

    Czech Academy of Sciences Publication Activity Database

    Sfîcă, L.; Voiculescu, M.; Huth, Radan

    2015-01-01

    Roč. 33, č. 2 (2015), s. 207-215. ISSN 0992-7689 R&D Projects: GA MŠk LD12053 Institutional support: RVO:68378289 Keywords : meteorology and atmospheric dynamics * sea-level pressure * Maunder minimum * climate-change * decadal scale * variability * hemisphere * winter * cycle * stratosphere * troposphere Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 1.709, year: 2014

  13. Associations between spatially autocorrelated patterns of SSM/I-derived prairie snow cover and atmospheric circulation

    International Nuclear Information System (INIS)

    Passive-microwave derived observations of snow cover show potential to provide synoptically sensitive, and hydrologically and climatologically significant, information because of all-weather imaging capabilities, rapid scene revisit time and the ability to derive quantitative estimates of snow water equivalent (SWE). In this study, we seek to identify the dominant patterns of clustering in SWE imagery using the Getis statistic, a local indicator of spatial association. The SWE data were derived from five day-averaged Special Sensor Microwave/Imager (SSM/I) brightness temperatures using the Canadian Atmospheric Environment Service dual channel algorithm. The analysed data span one winter season (December–February 1988–1989) and are limited to a ground-validated prairie scene. National Center for Environmental Prediction (NCEP) gridded atmospheric data (500 mb geopotential height; 700 mb temperature) were incorporated into the study to investigate whether the spatial orientation of the Getis statistic clusters provides information on interaction between snow cover and the atmosphere. Results show that the direction of atmospheric airflow as expressed by the 500 mb geopotential height field corresponds strongly to the orientation of surface snow cover clusters with no time lag. The 700 mb temperature field is also a controlling influence on the snow cover clusters both through modifying cluster orientation and reinforcing cluster magnitude. (author)

  14. 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

  15. Circulation features driven by diurnal heating in the lower atmospheric layers of the Po Valley

    International Nuclear Information System (INIS)

    Some meteorological situations with clear sky and without dynamic circulation were considered during summer diurnal heating over the Po Valley and surrounding regions. The pressure field distribution at sea level and the structure of the anemometric field seem to justify the hypothesis of the existence of breeze winds on the synoptic scale, due to the differential heating among mountains and plain and among plain and sea basins. In particular the behaviour was examined of the wind along the vertical at Milano-Linate, during several period of 24 hours favourable to the development of synoptic breezes, which occur among mountains and the Po Valley. The intensity of the breezes was evaluated also by the assessment of the thermic causes involved. (author)

  16. Neutrino anomalies without oscillations

    Indian Academy of Sciences (India)

    Sandip Pakvasa

    2000-01-01

    I review explanations for the three neutrino anomalies (solar, atmospheric and LSND) which go beyond the `conventional' neutrino oscillations induced by mass-mixing. Several of these require non-zero neutrino masses as well.

  17. 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.

  18. Global atmospheric effects of massive smoke injections from a nuclear war: results from general circulation model simulations

    International Nuclear Information System (INIS)

    The paper reports three-dimensional calculations of regional and global climatic effects of smoke generated by a large-scale nuclear war. Tropospheric aerosols of absorption optical depth 3, when injected into Northern Hemisphere mid-latitudes and maintained for 1-3 weeks, cause intense radiative heating of the mid-troposphere with substantial surface cooling over land. Mid-latitude surface temperatures in continental interiors can drop well below freezing in a matter of days regardless of season. The results, although based on several assumptions, suggest that circulation changes caused by aerosol-induced atmospheric radiative heating could spread the aerosols well beyond the altitude and latitude zones in which the smoke was initially generated. (author)

  19. A wavelet-based approach to detect climate change on the coherent and turbulent component of the atmospheric circulation

    Science.gov (United States)

    Faranda, Davide; Defrance, Dimitri

    2016-06-01

    The modifications of atmospheric circulation induced by anthropogenic effects are difficult to capture because wind fields feature a complex spectrum where the signal of large-scale coherent structures (planetary, baroclinic waves and other long-term oscillations) is mixed up with turbulence. Our purpose is to study the effects of climate changes on these two components separately by applying a wavelet analysis to the 700 hPa wind fields obtained in climate simulations for different forcing scenarios. We study the coherent component of the signal via a correlation analysis to detect the persistence of large-scale or long-lasting structures, whereas we use the theory of autoregressive moving-average stochastic processes to measure the spectral complexity of the turbulent component. Under strong anthropogenic forcing, we detect a significant climate change signal. The analysis suggests that coherent structures will play a dominant role in future climate, whereas turbulent spectra will approach a classical Kolmogorov behaviour.

  20. Physical and Mathematical Properties of a Quasi-Geostrophic Model of Intermediate Complexity of the Mid-Latitudes Atmospheric Circulation

    CERN Document Server

    Lucarini, V; VItolo, R; Itolo, Renato V; Lucarini, Valerio; Speranza, Antonio

    2005-01-01

    A quasi-geostrophic intermediate complexity model is considered, providing a schematic representation of the baroclinic conversion processes which characterize the physics of the mid-latitudes atmospheric circulation. The model is relaxed towards a given latitudinal temperature profile, which acts as baroclinic forcing, controlled by a parameter TE determining the forced equator-to-pole temperature gradient. As TE increases, a transition takes place from a stationary regime to a periodic regime, and eventually to an earth-like chaotic regime where evolution takes place on a strange attractor. The dependence of the attractor dimension, metric entropy, and bounding box volume in phase space is studied by varying both TE and model resolution. The statistical properties of observables having physical relevance, namely the total energy of the system and the latitudinally averaged zonal wind, are also examined. It is emphasized that while the attractor's properties are quite sensitive to model resolution, the globa...

  1. Atmospheric HT and HTO: V. distribution and large-scale circulation

    International Nuclear Information System (INIS)

    The two major chemical forms of atmospheric tritium are water vapour (HTO) and hydrogen gas (HT). These forms have quite different sources, distributions and sinks. The chemical conversion from HT to HTO in the atmosphere proceeds with a characteristic time of 6.5 years. Combined with the radioactive decay, a net lifetime of 4.8 years is estimated for atmospheric HT. HT is released predominately at the surface in mid- to high latitudes in the northern hemisphere. A negative gradient southward has been found from aircraft transects and from sampling at surface stations. After many years of a relatively constant global inventory of 1.1 kg of tritium gas, the HT mixing ratios decreased during 1977, with the sharpest drop at high latitudes. The estimated decline in annual production was 100 g. At the end of 1977, the atmospheric HT burden was 1.0 kg, and the estimated annual release was 200 g. An unknown portion is present as T2 gas. The effect of T2 is to decrease the net lifetime to 3.7 years. In the troposphere, the cycle of HTO has been treated exhaustively by others. The stratospheric distribution of HTO has been sampled from aircraft, and found to increase rapidly with height above the troposphere. An annual cycle has been observed, in which the lower stratosphere is depleted during the spring, and replenished by subsidence from higher levels during summer and fall. The effects of a nuclear test by the People's Republic of China in November 1976 have been clearly observed in the stratospheric HTO; however, no HT deposition was found. Presumably, the HTO at higher levels was originally deposited by the large nuclear weapons tests of the 1960s. An estimated 5 kg of tritium are now present in the stratosphere below 19 km. (author)

  2. Recent Northern Hemisphere stratospheric HCl increase due to atmospheric circulation changes

    OpenAIRE

    Mahieu, Emmanuel; M. P. Chipperfield; Notholt, J.; T. Reddmann; J. Anderson; Bernath, P. F.; Blumenstock, T.; M. T. Coffey; S. S. Dhomse; W. Feng; Franco, Bruno; Froidevaux, L.; D. W. T. Griffith; Hannigan, J.W.; F. Hase

    2014-01-01

    The abundance of chlorine in the Earth’s atmosphere increased considerably during the 1970s to 1990s, following large emissions of anthropogenic long-lived chlorine-containing source gases, notably the chlorofluorocarbons. The chemical inertness of chlorofluorocarbons allows their transport and mixing throughout the troposphere on a global scale[1], before they reach the stratosphere where they release chlorine atoms that cause ozone depletion[2]. The large ozone loss over Antarctica[3] was t...

  3. Long-term evolution of daily atmospheric circulation indices and types in European regions since 1850

    Czech Academy of Sciences Publication Activity Database

    Cahynová, Monika

    Alphabet: Crete University Press & Maria Kanakidou, 2014. s. 177-177. ISBN 978-960-524-430-9. [COMECAP 2014 - International Conference of Meteorology, Climatology and Physics of the Atmosphere /12./. 28.05.2014–31.05.2014, Heraklion] Institutional support: RVO:68378289 Subject RIV: DG - Athmosphere Sciences, Meteorology http://comecap2014.chemistry.uoc.gr/COMECAP-ISBN-978-960-524-430-9-vol.%201.pdf

  4. The global distribution of natural tritium in precipitation simulated with an Atmospheric General Circulation Model and comparison with observations

    Science.gov (United States)

    Cauquoin, A.; Jean-Baptiste, P.; Risi, C.; Fourré, É.; Stenni, B.; Landais, A.

    2015-10-01

    The description of the hydrological cycle in Atmospheric General Circulation Models (GCMs) can be validated using water isotopes as tracers. Many GCMs now simulate the movement of the stable isotopes of water, but here we present the first GCM simulations modelling the content of natural tritium in water. These simulations were obtained using a version of the LMDZ General Circulation Model enhanced by water isotopes diagnostics, LMDZ-iso. To avoid tritium generated by nuclear bomb testing, the simulations have been evaluated against a compilation of published tritium datasets dating from before 1950, or measured recently. LMDZ-iso correctly captures the observed tritium enrichment in precipitation as oceanic air moves inland (the so-called continental effect) and the observed north-south variations due to the latitudinal dependency of the cosmogenic tritium production rate. The seasonal variability, linked to the stratospheric intrusions of air masses with higher tritium content into the troposphere, is correctly reproduced for Antarctica with a maximum in winter. LMDZ-iso reproduces the spring maximum of tritium over Europe, but underestimates it and produces a peak in winter that is not apparent in the data. This implementation of tritium in a GCM promises to provide a better constraint on: (1) the intrusions and transport of air masses from the stratosphere, and (2) the dynamics of the modelled water cycle. The method complements the existing approach of using stable water isotopes.

  5. Inter-annual temperature and precipitation variations over the Litani Basin in response to atmospheric circulation patterns

    Science.gov (United States)

    Ramadan, H. H.; Ramamurthy, A. S.; Beighley, R. E.

    2012-05-01

    This study examines the sensitivity of a mid-size basin's temperature and precipitation response to different global and regional climate circulation patterns. The implication of the North Atlantic Oscillation (NAO), El Niño Southern Oscillation (ENSO), Indian Monsoon and ten other teleconnection patterns of the Northern Hemisphere are investigated. A methodology to generate a basin-scale, long-term monthly surface temperature and precipitation time series has been established using different statistical tests. The Litani River Basin is the focus of this study. It is located in Lebanon, east of the Mediterranean Basin, which is known to have diverse geophysical and environmental characteristics. It was selected to explore the influence of the diverse physical and topographical features on its hydroclimatological response to global and regional climate patterns. We also examine the opportunity of conducting related studies in areas with limited long-term measured climate and/or hydrological data. Litani's monthly precipitation and temperature data have been collected and statistically extrapolated using remotely sensed data products from satellites and as well as in situ gauges. Correlations between 13 different teleconnection indices and the basin's precipitation and temperature series are investigated. The study shows that some of the annual and seasonal temperature and precipitation variance can be partially associated with many atmospheric circulation patterns. This would give the opportunity to relate the natural climate variability with the watershed's hydroclimatology performance and thus differentiate it from other anthropogenic induced climate change outcomes.

  6. Seasonal flows of international British Columbia-Alaska rivers: The nonlinear influence of ocean-atmosphere circulation patterns

    Science.gov (United States)

    Fleming, S. W.; Hood, E.; Dahlke, H. E.; O'Neel, S.

    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.

  7. 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.

  8. The implementation and validation of improved land-surface hydrology in an atmospheric general circulation model

    Science.gov (United States)

    Johnson, Kevin D.; Entekhabi, Dara; Eagleson, Peter S.

    1993-01-01

    New land-surface hydrologic parameterizations are implemented into the NASA Goddard Institute for Space Studies (GISS) General Circulation Model (GCM). These parameterizations are: 1) runoff and evapotranspiration functions that include the effects of subgrid-scale spatial variability and use physically based equations of hydrologic flux at the soil surface and 2) a realistic soil moisture diffusion scheme for the movement of water and root sink in the soil column. A one-dimensional climate model with a complete hydrologic cycle is used to screen the basic sensitivities of the hydrological parameterizations before implementation into the full three-dimensional GCM. Results of the final simulation with the GISS GCM and the new land-surface hydrology indicate that the runoff rate, especially in the tropics, is significantly improved. As a result, the remaining components of the heat and moisture balance show similar improvements when compared to observations. The validation of model results is carried from the large global (ocean and land-surface) scale to the zonal, continental, and finally the regional river basin scales.

  9. The implementation and validation of improved landsurface hydrology in an atmospheric general circulation model

    Science.gov (United States)

    Johnson, Kevin D.; Entekhabi, Dara; Eagleson, Peter S.

    1991-01-01

    Landsurface hydrological parameterizations are implemented in the NASA Goddard Institute for Space Studies (GISS) General Circulation Model (GCM). These parameterizations are: (1) runoff and evapotranspiration functions that include the effects of subgrid scale spatial variability and use physically based equations of hydrologic flux at the soil surface, and (2) a realistic soil moisture diffusion scheme for the movement of water in the soil column. A one dimensional climate model with a complete hydrologic cycle is used to screen the basic sensitivities of the hydrological parameterizations before implementation into the full three dimensional GCM. Results of the final simulation with the GISS GCM and the new landsurface hydrology indicate that the runoff rate, especially in the tropics is significantly improved. As a result, the remaining components of the heat and moisture balance show comparable improvements when compared to observations. The validation of model results is carried from the large global (ocean and landsurface) scale, to the zonal, continental, and finally the finer river basin scales.

  10. 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

  11. 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.

  12. ENSO cycle and climate anomaly in China

    Institute of Scientific and Technical Information of China (English)

    CHEN Yongli; ZHAO Yongping; FENG Junqiao; WANG Fan

    2012-01-01

    The inter-annual variability of the tropical Pacific Subsurface Ocean Temperature Anomaly (SOTA) and the associated anomalous atmospheric circulation over the Asian North Pacific during the El Ni(n)o-Southern Oscillation (ENSO) were investigated using National Centers for Environmental Prediction/ National Center for Atmospheric Research (NCEP/NCAR) atmospheric reanalysis data and simple ocean data simulation (SODA).The relationship between the ENSO and the climate of China was revealed.The main results indicated the following:1) there are two ENSO modes acting on the subsurface tropical Pacific.The first mode is related to the mature phase of ENSO,which mainly appears during winter.The second mode is associated with a transition stage of the ENSO developing or decaying,which mainly occurs during summer; 2) during the mature phase of El Ni(n)o,the meridionality of the atmosphere in the mid-high latitude increases,the Aleutian low and high pressure ridge over Lake Baikal strengthens,northerly winds prevail in northern China,and precipitation in northern China decreases significantly.The ridge of the Ural High strengthens during the decaying phase of El Ni(n)o,as atmospheric circulation is sustained during winter,and the northerly wind anomaly appears in northern China during summer.Due to the ascending branch of the Walker circulation over the western Pacific,the western Pacific Subtropical High becomes weaker,and south-southeasterly winds prevail over southern China.As a result,less rainfall occurs over northern China and more rainfall over the Changjiang River basin and the southwestern and eastern region of Inner Mongolia.The flood disaster that occurred south of Changjiang River can be attributed to this.The La Ni(n)a event causes an opposite,but weaker effect; 3) the ENSO cycle can influence climate anomalies within China via zonal and meridional heat transport.This is known as the "atmospheric-bridge",where the energy anomaly within the tropical Pacific

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

    Directory of Open Access Journals (Sweden)

    I. V. Mingalev

    2006-09-01

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

  14. Ocean-atmosphere pollutant circulation processes: The Heligoland Bight ecosystem (PRISMA). 2. interim report (1991)

    International Nuclear Information System (INIS)

    The PRISMA BMFT project is an important stage on the way to a comprehensive knowledge of the impacts of pollutants on the North Sea/Heligoland Bight ecosystem. The overall project is dedicated to the development, verification and application of a complex shelf-sea model which provides qualitative and quantitative data about the causal interactions between the basic atmospheric conditions, the hydrodynamics and thermodynamics of the water, the chemical reactons in the air, in the water and the sediments, and the activity of organisms. The model comprises a compact set of formulae, process formulations, initial and marginal conditions and empirical parameters which serves to describe the origin, transport, reactions and final deposition of pollutants in the North Sea, helps to analyze and elucidate the present condition of the ecosystem and its spatial and temporal variability, and provides forecasts in accordance with the changing natural and anthropogenic environmental conditions. (orig.)

  15. Coastal atmospheric circulation assessment for emergency off-site dose considerations

    International Nuclear Information System (INIS)

    More than 40 nuclear facilities are located near large bodies of water and are influenced by seasonal and diurnal lake/sea breeze phenomena. Atmospheric transport in the vicinity of the Shoreham nuclear power plant is affected, in part, by the sound breeze generated by Long Island Sound and/or the ocean breeze generated by the Atlantic Ocean. The sound and ocean breeze phenomena produce spatial discrepancies in the wind field within the Shoreham Emergency Planning Zone (EPZ) during the morning to early evening hours throughout the spring to early autumn. In addition, there is a potential trajectory reversal to the sound/ocean breeze front. Two simple, easy-to-use procedures were developed that could be used by plant personnel to determine in real time (a) the presence of a sound and/or ocean breeze front located within the Shoreham EPZ and (b) the significant plume impact region resulting from an unscheduled release during this condition

  16. 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.

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

    Directory of Open Access Journals (Sweden)

    P. Jöckel

    2006-01-01

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

  18. Atmospheric Circulation Influence on the Winter Thermal Conditions in Poland in 2021-2050 Based on the RACMO2 Model

    Science.gov (United States)

    Jędruszkiewicz, Joanna; Piotrowski, Piotr

    2012-01-01

    Thermal conditions are largely determined by atmospheric circulation. Therefore, projection of future temperature changes should be considered in relation to changes in circulation patterns. This paper assess to what extent changes in circulation correspond to spatial variability of the winter temperature increase in Poland in 2021-2050 period based on the RACMO2 model. The daily data of the mean temperature and sea level pressure (SLP) from selected regional climate model and observations were used. SLP data were used to determine the advection types and circulation character. Firstly, changes in frequency of circulation types between 2021-2050 and 1971-2000 periods were examined. Then changes in air temperature for specific circulation type in relation to reference period were studied. Finally, the influence of atmospheric circulation on spatial temperature variation was discussed. Considerably high increase in cyclonic situation of more than 18%, especially from the west and south-west direction, and decrease in anticyclonic situation mainly from the west and northwest in winter was noticed. Changes in frequency of circulation types result in temperature growth. For some types it is predicted that warming can reach even 3-4°C. The cyclonic (Ec, SEc, Sc) and anticylonic (SEa, Sa, Ea) types are likely to foster the highest warming in the scenario period. Polska charakteryzuje się znacznym zróżnicowaniem przestrzennym w rozkładzie temperatury powietrza w porze zimowej. W sezonie zimowym przeważa południkowy układ izoterm co świadczy o silnym oddziaływaniu z jednej strony ciepłych, wilgotnych mas powietrza napływających znad Atlantyku, a z drugiej chłodniejszych i bardziej suchych znad kontynentu azjatyckiego. Regionalne modele klimatu opracowane dla obszaru Europy wskazują jednoznacznie na wzrost temperatury w okresie zimy na obszarze całego kontynentu, szczególnie a wschodzie i północnym-wschodzie kontynentu, nawet o 3°C. Projekcje te s

  19. 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.

  20. Heavy rainfall episodes in Ecuador during El Niño events and associated regional atmospheric circulation and SST patterns

    Directory of Open Access Journals (Sweden)

    A. Bendix

    2006-01-01

    Full Text Available To date very little is known about the relation between regional circulation patterns and sea surface temperature development in the Niño 1,2 region and the occurrence of heavy precipitation in Ecuador and northern Peru. The current study uses a comprehensive data set of 2544 Meteosat-3 imagery to investigate the dynamics of heavy precipitation during El Niño in 1991/92. Rainfall maps are retrieved by means of an adjusted version of the Convective Stratiform Technique (CST and Cloud Motion Winds (CMW are extracted from image sequences by using a special cross-correlation approach. A spatial factor analysis is applied to extract specific weather situations with heavy precipitation during El Niño events. The factor analysis yielded 16 factors. It has been proven that the factor patterns with the highest variance explanation also occur during the rainy season of non-El Niño years. However, 6 El Niño-specific situations could be derived which cause heavy rainfall, especially in coastal Ecuador and northern Peru. Multi-channel Sea Surface Temperatures (MCSST and cloud motion winds are used to describe atmospheric and oceanic dynamics for these specific weather situations. The analysis shows that high SSTs in combination with strong SST gradients off the coast and warm SST bubbles lead to regional differences in moist instability and heavy rainfall. Both large scale circulation (reversal of the Walker cell and regional dynamics (extended land-sea-breeze system have been proven to contribute to El Niño rainfall.

  1. 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

  2. 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.

  3. 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

  4. North Atlantic SST anomalies and the cold North European weather events of winter 2009/10 and December 2010

    OpenAIRE

    Buchan, Jian; Hirschi, Joel; Blaker, Adam; Sinha, Bablu

    2014-01-01

    Northern Europe experienced consecutive periods of extreme cold weather in the winter of 2009/2010 and in late 2010. These periods were characterised by a tripole pattern in North Atlantic sea surface temperature (SST) anomalies and exceptionally negative phases of the North Atlantic Oscillation (NAO). A global Ocean-Atmosphere General Circulation Model (OAGCM) is used to investigate the ocean’s role in influencing North Atlantic and European climate. Observed SST anomalies are used to force ...

  5. New directions in hydro-climatic histories: observational data recovery, proxy records and the atmospheric circulation reconstructions over the earth (ACRE) initiative in Southeast Asia

    Science.gov (United States)

    Williamson, Fiona; Allan, Rob; Switzer, Adam D.; Chan, Johnny C. L.; Wasson, Robert James; D'Arrigo, Rosanne; Gartner, Richard

    2015-12-01

    The value of historic observational weather data for reconstructing long-term climate patterns and the detailed analysis of extreme weather events has long been recognized (Le Roy Ladurie, 1972; Lamb, 1977). In some regions however, observational data has not been kept regularly over time, or its preservation and archiving has not been considered a priority by governmental agencies. This has been a particular problem in Southeast Asia where there has been no systematic country-by-country method of keeping or preserving such data, the keeping of data only reaches back a few decades, or where instability has threatened the survival of historic records. As a result, past observational data are fragmentary, scattered, or even absent altogether. The further we go back in time, the more obvious the gaps. Observational data can be complimented however by historical documentary or proxy records of extreme events such as floods, droughts and other climatic anomalies. This review article highlights recent initiatives in sourcing, recovering, and preserving historical weather data and the potential for integrating the same with proxy (and other) records. In so doing, it focuses on regional initiatives for data research and recovery - particularly the work of the international Atmospheric Circulation Reconstructions over the Earth's (ACRE) Southeast Asian regional arm (ACRE SEA) - and the latter's role in bringing together disparate, but interrelated, projects working within this region. The overarching goal of the ACRE SEA initiative is to connect regional efforts and to build capacity within Southeast Asian institutions, agencies and National Meteorological and Hydrological Services (NMHS) to improve and extend historical instrumental, documentary and proxy databases of Southeast Asian hydroclimate, in order to contribute to the generation of high-quality, high-resolution historical hydroclimatic reconstructions (reanalyses) and, to build linkages with humanities researchers

  6. 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.

  7. 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.

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

    Directory of Open Access Journals (Sweden)

    T. Tharammal

    2013-03-01

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

  9. 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.

  10. Impact of southern and central European land surface heating induced by greenhouse warming on the atmospheric circulation

    International Nuclear Information System (INIS)

    Full text: A robust result of greenhouse warming runs with global climate models is the depletion of soil moisture in southern and central Europe in summer. This leads to a strong increase in surface temperatures as a result of the accompanying reduction of the surface cooling by evaporation. In a series of sensitivity experiments with the EC-EARTH climate model we investigate the effect of this enhanced warming on the atmospheric circulation. EC-EARTH is a coupled climate model jointly developed by the EC-EARTH consortium and is based on the integrated forecast model of the ECMWF. The sensitivity experiments are designed to test the hypothesis that the enhanced summer surface easterlies over central Europe that are found in many recent climate scenario simulations are mainly due to the development of a heat low over the Mediterranean region in response to the enhanced warming of North Africa and Southern Europe. In the experiments with EC-EARTH the land surface temperature is artificially enhanced by increasing the downward surface solar radiation. This is done in order to enable the soil moisture to respond in a dynamically consistent way to the increase in surface land temperature. A similar approach has been successfully used in a previous study to show that an enhanced Sahara heating results in a deepening of the Sahara low with consequences for the Sahel rainfall. (author)

  11. Convectively Generated Gravity Waves In The Tropical Stratosphere: Case Studies And Importance For The Circulation Of The Middle Atmosphere

    Science.gov (United States)

    Pfister, Leonhard; Chan, Kwoklong R.; Gary, Bruce; Singh, Hanwant B. (Technical Monitor)

    1995-01-01

    The advent of high altitude aircraft measurements in the stratosphere over tropical convective systems has made it possible to observe the mesoscale disturbances in the temperature field that these systems excite. Such measurements show that these disturbances have horizontal scales comparable to those of the underlying anvils (about 50-100 km) with peak to peak theta surface variations of about 300-400 meters. Moreover, correlative wind measurements from the tropical phase of the Stratosphere-Troposphere Exchange Project (STEP) clearly show that these disturbances are gravity waves. We present two case studies of anvil-scale gravity waves over convective systems. Using steady and time-dependent linear models of gravity wave propagation in the stratosphere, we show: (1) that the underlying convective systems are indeed the source of the observed phenomena; and (2) that their generating mechanism can be crudely represented as flow over a time-dependent mountain. We will then discuss the effects gravity waves of the observed amplitudes have on the circulation of the middle atmosphere, particularly the quasi-biennial, and semiannual oscillations.

  12. Atmospheric teleconnections and regional-scale atmospheric anomalies over the Northern Hemisphere%北半球大气遥相关型与区域尺度大气扰动

    Institute of Scientific and Technical Information of China (English)

    钱维宏; 梁浩原

    2012-01-01

    Atmospheric teleconnections in the Northern Hemisphere such as Arctic Oscillation (AO). North Atlantic Oscillation (NAO) and Pacific-North American (PNA) teleconnection can be explained by the physical decomposition of geopotential height. The result shows that the AO reflects planetary-scale zonal-mean anomalies in the Arctic region; the PNA results from persistent regional-scale atmospheric anomaliesj NAO is a combined result of both planetary-scale zonal-mean and regional-scale anomalies. The rotated empirical orthogonal function (REOF) of planetary-scale zonal-mean and regional-scale anomalies riot only confirms the already known regional oscillations and wave trains, but also discovers new patterns, such as "twin dipole oscillations" in the Arctic region, Euro-Asia Oscillation (EAO) and Atlantic-Euro-Asia (AEA) wave-train pattern. These oscillations or wave trains are linked to adjacent regional weather anomalies and climate anomalies.%北极涛动(AO)、北大西洋涛动(NAO)和太平洋—北美型(PNA)等北半球大气遥相关型,可以用大气位势高度的物理分解扰动分量解释.结果发现,AO反映的是北极地区行星尺度纬圈平均扰动分量的变化,PNA与持续性天气尺度扰动分量相联系,NAO是行星尺度纬圈平均扰动与天气尺度扰动共同作用的结果.对行星尺度纬圈平均扰动分量和天气尺度扰动分量用旋转经验正交函数(REOF)展开,不但可以证实人们已经命名的区域性大气涛动,还新发现了北极地区的两对偶极涛动、欧亚涛动(EAO)和“大西洋-欧亚型”(AEA)波列.这些涛动连接了相邻地区的异常天气和异常气候.

  13. Local and remote impacts of a tropical Atlantic salinity anomaly

    Energy Technology Data Exchange (ETDEWEB)

    Mignot, Juliette; Frankignoul, Claude [UPMC/CNRS/IRD/MNHN, Universite Pierre et Marie Curie, IPSL/LOCEAN, Paris (France)

    2010-12-15

    The climatic impacts of an enhanced evaporation prescribed during 50 years in the tropical Atlantic are investigated in a coupled ocean-atmosphere general circulation model. Locally, the salinity increase leads to a rapid deepening and cooling of the surface mixed layer. This induces a deepening of the equatorial undercurrent and an intensification of the south equatorial current. A remote atmospheric response to the tropical Atlantic perturbation is detected in the North Atlantic sector after ten years. It has the form of a robust wave-like tropospheric perturbation seemingly excited by the weakening of atmospheric deep convection over the Amazonian basin. Meanwhile, the salt anomaly is carried northward by the mean oceanic circulation. It is traced up to the convection sites and then on its return path at depth towards lower latitudes. Consistent with the density increase, deep convection is enhanced after the arrival of the salt anomaly and the Atlantic meridional overturning circulation (AMOC) intensifies about 20 years after the beginning of the perturbation. The adjustment of the tropical Atlantic to the AMOC intensification then modifies its initial response to the freshwater forcing, leading to a weaker cooling in the northern tropical Atlantic than in the southern tropical Atlantic, a slight northward shift of the tropical Atlantic precipitation pattern and an intensification of the North Brazil current. On the other hand, no significant anomalous precipitations are found in the Pacific. The initial remote atmospheric response is also modulated, by an NAO-like response to the AMOC intensification. (orig.)

  14. Changes in daily climate extremes in China and their connection to the large scale atmospheric circulation during 1961-2003

    Energy Technology Data Exchange (ETDEWEB)

    You, Qinglong [Institute of Tibetan Plateau Research, Chinese Academy of Sciences (CAS), Laboratory of Tibetan Environment Changes and Land Surface Processes, Beijing (China); Friedrich-Schiller University Jena, Department of Geoinformatics, Jena (Germany); Graduate University of Chinese Academy of Sciences, Beijing (China); Kang, Shichang [Institute of Tibetan Plateau Research, Chinese Academy of Sciences (CAS), Laboratory of Tibetan Environment Changes and Land Surface Processes, Beijing (China); State Key Laboratory of Cryospheric Science, Chinese Academy of Sciences, Lanzhou (China); Aguilar, Enric [Universitat Rovirai Virgili de Tarragona, Climate Change Research Group, Geography Unit, Tarragona (Spain); Pepin, Nick [University of Portsmouth, Department of Geography, Portsmouth (United Kingdom); Fluegel, Wolfgang-Albert [Friedrich-Schiller University Jena, Department of Geoinformatics, Jena (Germany); Yan, Yuping [National Climate Center, Beijing (China); Xu, Yanwei; Huang, Jie [Institute of Tibetan Plateau Research, Chinese Academy of Sciences (CAS), Laboratory of Tibetan Environment Changes and Land Surface Processes, Beijing (China); Graduate University of Chinese Academy of Sciences, Beijing (China); Zhang, Yongjun [Institute of Tibetan Plateau Research, Chinese Academy of Sciences (CAS), Laboratory of Tibetan Environment Changes and Land Surface Processes, Beijing (China)

    2011-06-15

    negative magnitudes. This is inconsistent with changes of water vapor flux calculated from NCEP/NCAR reanalysis. Large scale atmospheric circulation changes derived from NCEP/NCAR reanalysis grids show that a strengthening anticyclonic circulation, increasing geopotential height and rapid warming over the Eurasian continent have contributed to the changes in climate extremes in China. (orig.)

  15. 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。

  16. 长江口外近岸环流对厄尔尼诺事件的响应%Anomaly response to El Ni?o events of nearshore circulation off Yangtze Estuary

    Institute of Scientific and Technical Information of China (English)

    张雯燕; 张长宽; 龚政; 谭伟

    2014-01-01

    建立了东中国海环流大模型,在此基础上建立包含长江口、杭州湾及邻近海域在内的区域环流模型,较准确地刻画东中国海外海流系和沿岸流系,以及长江口外精细的流系结构。选择典型厄尔尼诺年,模拟长江口外近岸环流的异常变化,探讨长江口外近岸环流与厄尔尼诺事件的响应关系。研究表明:长江口外近岸环流与厄尔尼诺事件存在强烈的响应关系,冬季厄尔尼诺现象发生时长江口及邻近海域的环流明显减弱;台湾暖流受厄尔尼诺事件影响程度显著,流速减小、流幅变窄,台湾暖流对长江口外近岸环流的影响也因此减弱。%In this study, an East China Sea circulation model was built. Based on this, a small-scale circulation model including the domain of the Yangtze Estuary, Hangzhou Bay, and adjacent water areas was built. With this model, the oceanic current system and coastal current system of the East China Sea, and the flow structure off the Yangtze Estuary were accurately simulated. In order to study the anomalies, typical El Niño years were chosen to analyze the response relationship between the nearshore circulation off the Yangtze Estuary and El Niño events. The results show that there was a significantly responsive relationship between the nearshore circulation off the Yangtze Estuary and El Niño events. In the winter, the circulation at the Yangtze Estuary and adjacent water areas weakened significantly when the El Niño phenomenon occurred. The Taiwan warm current was greatly affected, with decreased flow velocity and narrowed flow amplitude, which weakened the impact of the Taiwan warm current on the nearshore circulation off the Yangtze Estuary.

  17. 月尺度环流对SST强迫的响应特征及机理分析%Response Characteristics and Mechanism Analyses on Monthly Circulation to SST Anomaly Force

    Institute of Scientific and Technical Information of China (English)

    王秋良; 张立凤; 关吉平

    2012-01-01

    利用全球中期数值预报谱模式,通过在海表温度气候态上叠加不同扰动的方法,研究了不同季节月尺度大气环流对海表温度变化的响应特征及机理。结果表明,大气响应首先出现海表温度的高值区和海温扰动变化的大值区,其发展和演变还与大气环流的背景场有关,大气响应发展达到稳定的状态是沿南、北半球西风急流附近的纬向波状分布;在不同季节,对不同分布的海表温度变化,大气环流响应的速度不同,但在月尺度内大气响应都能达到最大值;相对于夏季,冬季大气响应最大值达到的高度更高,大气响应对扰动的形态更敏感。%Using the spectral forecast model with the global medium range, the response characteristics of monthly atmospheric circulation to SSTA (sea surface temperature anomaly) and the mechanism are in- vestigated. In order to detect the model response characteristic in different seasons, two sets of sensitivity numerical simulations are conducted. For each experiment, except for the control experiment that is per formed with climatological SST (sea surface temperature) for ocean boundary conditions, the other two in- tegrations forced with prescribed and random SSTA added to climatological SST. The simulated results show that atmospheric responses firstly generate in areas with high SST oceans and large disturbed SSTA oceans, and the development and evolution of atmospheric responses are related to the background of at- mospheric circulation. Furthermore, when the atmospheric responses in model come to a steady state, the simulated atmospheric responses are in zonal wavy distribution along westerly jet. During the different seasons, the speeds of atmospheric circulation response have the dissimilar SST distribution. However, both in winter and in summer, the size of responses can reach maximum within monthly time scale. In gen- eral, atmospheric responses are

  18. 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.

    2015-09-01

    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.

  19. Interannual variability of summer sea ice thickness in the Siberian and central Arctic under different atmospheric circulation regimes

    Science.gov (United States)

    Haas, Christian; Eicken, Hajo

    2001-03-01

    Extensive drill hole and electromagnetic induction measurements of sea ice thickness in the Siberian and central Arctic Seas in the summers of 1993, 1995, and 1996 reveal significant interannual variability. In the Laptev Sea, minimum and maximum modal first-year ice thicknesses amounted to 1.25 and 1.85 m in 1995 and 1996, respectively. Ice thickness correlates with ice extent, which reached a record minimum in August 1995 and was well above average in 1996. These differences are explained by the strength and location of a summer cyclonic atmospheric circulation pattern affecting both ice advection and surface melt. From drifting buoys deployed in 1995 and satellite radar backscatter data, first- and second-year ice regimes are delineated. Differences in first-year ice backscatter coefficients between 1993, 1995, and 1996 are explained by differences in level ice surface roughness. The Lagrangian evolution of ice thickness between 1995 and 1996 is studied. While the shape of the thickness distribution does not change significantly, the mean (modal) ice thickness of the ice field increases from 1.80 m (1.25 m) in 1995 to 2.86 m (2.25 m) in 1996. The thickness distribution of second-year ice in 1996 closely agrees with that of level multiyear ice downstream in the Transpolar Drift obtained in 1991. In 1996, mean level ice thickness increases at 0.23 and 0.16 m deg-1 with latitude in the Kara and Laptev Sea sectors of the Arctic Ocean, respectively.

  20. Thermodynamic and economic analysis of polygeneration system integrating atmospheric pressure coal pyrolysis technology with circulating fluidized bed power plant

    International Nuclear Information System (INIS)

    Highlights: • A lignite pyrolysis-based polygeneration plant was proposed and modeled. • Polygeneration plant has a 9.04% point higher efficiency than CFB power plant. • Polygeneration plant increases ca. 14% point of IRR based on CFB power plant. • Electricity price rise makes polygeneration plant less competitive. - Abstract: Lignite-based polygeneration system has been considered as a feasible technology to realize clean and efficient utilization of coal resources. A newly polygeneration system has been proposed, featuring the combination of a 2 × 300 MW circulating fluidized bed (CFB) power plant and atmospheric pressure fluidized bed pyrolyzers. Xiaolongtan lignite is pyrolyzed in pyrolyzers. Pyrolyzed volatiles are further utilized for the co-generation of methanol, oil, and electricity, while char residues are fired in CFB boilers to maintain the full load condition of boilers. Detailed system models were built, and the optimum operation parameters of the polygeneration plant were sought. Technical and economic performances of optimum design of the polygeneration plant were analyzed and compared with those of the conventional CFB power plant based on the evaluation of energy and exergy efficiency, internal rate of return (IRR), and payback period. Results revealed that system efficiency and the IRR of the polygeneration plant are ca. 9% and 14% points higher than those of the power plant, respectively. The study also analyzed the effects of market fluctuations on the economic condition of the polygeneration plant, and found that prices of fuel, material, and products have great impacts on the economic characteristics of the polygeneration plant. Polygeneration plant is more economic than CFB power plant even when prices fluctuate within a wide range. This paper provides a thorough evaluation of the polygeneration plant, and the study indicates that the proposed polygeneration plant has a bright prospect

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

    Science.gov (United States)

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

    2016-04-01

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

  2. The East-West effect of the muon charge ratio at energies relevant to the atmospheric neutrino anomaly

    International Nuclear Information System (INIS)

    The charge ratio of atmospheric muons is rather sensitive to effects of the geomagnetic field and to the hadronic interaction. Experimental information about this quantity is very useful for tuning the ingredients of models used for calculations of atmospheric neutrino fluxes. For experimental observations, and in particular regarding the asymmetry in the charge ratio of muons from the east and West directions (East-West effect) a rotatable device has been installed in NIPNE-HH (National Institute of Physics and Nuclear Engineering -- Horia Hulubei) Bucharest (44 deg. 26'N, 26 deg. 04' E, 85 m above sea-level at a vertical cut-off rigidity of 5.6 GV). The detector is mounted in a rotatable frame, consisting of a stack of 16 modules, 90 x 90 cm2, formed by plastic scintillator layers (3 cm thick) and aluminum support (1.2 cm thick), surrounded by 4 lateral veto counters. The measurements are based on observation of the life time of muons stopped in the absorber layers of the detector. At a mean zenith angle of 35 deg. the East West asymmetry in the ratio has been found to decrease from 0.25 to 0.20, in the momentum range 0.35 - 0.50 GeV/c

  3. The unified model, a fully-compressible, non-hydrostatic, deep atmosphere global circulation model, applied to hot Jupiters. ENDGame for a HD 209458b test case

    Science.gov (United States)

    Mayne, Nathan J.; Baraffe, Isabelle; Acreman, David M.; Smith, Chris; Browning, Matthew K.; Skålid Amundsen, David; Wood, Nigel; Thuburn, John; Jackson, David R.

    2014-01-01

    We are adapting the global circulation model (GCM) of the UK Met Office, the so-called unified model (UM), for the study of hot Jupiters. In this work we demonstrate the successful adaptation of the most sophisticated dynamical core, the component of the GCM which solves the equations of motion for the atmosphere, available within the UM, ENDGame (Even Newer Dynamics for General atmospheric modelling of the environment). Within the same numerical scheme ENDGame supports solution to the dynamical equations under varying degrees of simplification. We present results from a simple, shallow (in atmospheric domain) hot Jupiter model (SHJ), and a more realistic (with a deeper atmosphere) HD 209458b test case. For both test cases we find that the large-scale, time-averaged (over the 1200 days prescribed test period), dynamical state of the atmosphere is relatively insensitive to the level of simplification of the dynamical equations. However, problems exist when attempting to reproduce the results for these test cases derived from other models. For the SHJ case the lower (and upper) boundary intersects the dominant dynamical features of the atmosphere meaning the results are heavily dependent on the boundary conditions. For the HD 209458b test case, when using the more complete dynamical models, the atmosphere is still clearly evolving after 1200 days, and in a transient state. Solving the complete (deep atmosphere and non-hydrostatic) dynamical equations allows exchange between the vertical and horizontal momentum of the atmosphere, via Coriolis and metric terms. Subsequently, interaction between the upper atmosphere and the deeper more slowly evolving (radiatively inactive) atmosphere significantly alters the results, and acts over timescales longer than 1200 days. Figures 1, 4-8, 10 and 11 are available in electronic form at http://www.aanda.org

  4. The effects of North AtlanticSST and sea-ice anomalies in CCM3. Part I: Main features and storm-track characteristics of the response

    OpenAIRE

    Magnusdottir, G.; Deser, C.; Saravanan, R.

    2004-01-01

    Observed multidecadal trends in extratropical atmospheric flow, such as the positive trend in the North Atlantic Oscillation (NAO) index, may be attributable to a number of causes. This study addresses the question of whether the atmospheric trends may be caused by observed trends in oceanic boundary forcing. Experiments were carried out using the NCAR atmospheric general circulation model with specified sea surface temperature (SST) and sea ice anomalies confined to the North Atlantic sector...

  5. Role of sea surface temperature, Arctic sea ice and Siberian snow in forcing the atmospheric circulation in winter of 2012–2013

    OpenAIRE

    Peings, Y.; Magnusdottir, G.

    2015-01-01

    © 2014 Springer-Verlag Berlin Heidelberg During the 2012–2013 winter, the negative phase of the North Atlantic Oscillation (NAO) predominated, resulting in a cold winter over Europe and northern Asia punctuated by episodes of frigid weather. This climate anomaly is part of a recent trend towards negative values of the NAO index that has occurred over recent winters. The negative trend of the NAO may be related to atmospheric internal variability but it may also be partly forced by slowly vary...

  6. The tropical Pacific-Indian Ocean temperature anomaly mode and its effect

    Institute of Scientific and Technical Information of China (English)

    YANG Hui; JIA Xiaolong; LI Chongyin

    2006-01-01

    Temperature anomaly in the Indian Ocean is closely related to that in the Pacific Ocean because of the Walker circulation and the Indonesian throughflow. So only the El Ni(n)o/Southern Oscillation (ENSO) in the Pacific cannot entirely explain the influence of sea surface temperature anomaly (SSTA)on climate variation. The tropical Pacific-Indian Ocean temperature anomaly mode (PIM) is presented based on the comprehensive research on the pattern and feature of SSTA in both Indian Ocean and Pacific Ocean. The features of PIM and ENSO mode and their influences on the climate in China and the rainfall in India are further compared. For proving the observation results, numerical experiments of the global atmospheric general circulation model are conducted. The results of observation and sensitivity experiments show that presenting PIM and studying its influence are very important for short-range climate prediction.

  7. 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

  8. Bolivian Bouguer Anomaly Grid

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — A 1 kilometer Bouguer anomaly grid for the country of Bolivia.Number of columns is 550 and number of rows is 900. The order of the data is from the lower left to...

  9. Plant wax δD values record changing Eastern Mediterranean atmospheric circulation patterns during the 8.2 kyr B.P. climatic event

    Science.gov (United States)

    Schemmel, Fabian; Niedermeyer, Eva M.; Schwab, Valérie F.; Gleixner, Gerd; Pross, Jörg; Mulch, Andreas

    2016-02-01

    Throughout the Holocene, the climate of the Mediterranean region has been strongly influenced by variability in the atmospheric circulation of the high and low latitudes. A prominent example for such Holocene climate perturbations is the '8.2 kyr B.P. climatic event'. Reorganization of Northern Hemisphere atmospheric circulation patterns resulted in variations of temperature and precipitation distribution across the Mediterranean. The effects of changing high- and low-latitude atmospheric circulation on Mediterranean climate in relation to the 8.2 kyr B.P. climatic event are, however, not well understood. Here we present a high-resolution record of stable hydrogen isotope composition of plant-wax n-alkanes (δDwax) across the 8.2 kyr B.P. climatic event from the Tenaghi Philippon peat deposit (NE Greece) in order to characterize patterns of precipitation and changes in atmospheric circulation in the Eastern Mediterranean region. Our record reveals pronounced changes in δDwax that correlate closely with previously published palynological data. A long-term decline in δDwax values characterizes the lower part of the section. The 8.2 kyr B.P. climatic event itself is connected to two distinct positive δDwax excursions: a minor shift in δDwax around 8.2 kyr B.P. and a major shift in δDwax between ca. 8.1 and 8.0 kyr B.P.. The upper part of the section shows a progressive trend towards higher δDwax values. We link shifts in δDwax to changes in Mediterranean air mass trajectories supplying precipitation to NE Greece caused by variations in the relative contributions of northerly-derived, D-depleted moisture and southerly-derived, D-enriched moisture. Possible control mechanisms for alternating air mass trajectories include changes in the influence of the Siberian High and differences in the influence of the African and Asian monsoon circulation on anticyclonic conditions in the Mediterranean region as well as regional inflow of moist air masses from the Aegean Sea.

  10. Role of the Indian Ocean on the southern oscillation, atmospheric circulation indices and monsoon rainfall over India

    Digital Repository Service at National Institute of Oceanography (India)

    Sadhuram, Y.; Wells, N.C.

    African sectors are strongly correlated with the November SST of the previous year. The influence of SST anomalies in the study area on SOI is seen at a lag of 25 months. A sharp fall in SST from September to December in the Eastern Equatorial Indian Ocean...

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

    Science.gov (United States)

    Huth, Radan; Cahynová, Monika; Kyselý, Jan

    2010-05-01

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

  12. Interannual drought index variations in Central Europe related to the large-scale atmospheric circulation—application and evaluation of statistical downscaling approaches based on circulation type classifications

    Science.gov (United States)

    Beck, Christoph; Philipp, Andreas; Jacobeit, Jucundus

    2015-08-01

    This contribution investigates the relationship between the large-scale atmospheric circulation and interannual variations of the standardized precipitation index (SPI) in Central Europe. To this end, circulation types (CT) have been derived from a variety of circulation type classifications (CTC) applied to daily sea level pressure (SLP) data and mean circulation indices of vorticity ( V), zonality ( Z) and meridionality ( M) have been calculated. Occurrence frequencies of CTs and circulation indices have been utilized as predictors within multiple regression models (MRM) for the estimation of gridded 3-month SPI values over Central Europe, for the period 1950 to 2010. CTC-based MRMs used in the analyses comprise variants concerning the basic method for CT classification, the number of CTs, the size and location of the spatial domain used for CTCs and the exclusive use of CT frequencies or the combined use of CT frequencies and mean circulation indices as predictors. Adequate MRM predictor combinations have been identified by applying stepwise multiple regression analyses within a resampling framework. The performance (robustness) of the resulting MRMs has been quantified based on a leave-one-out cross-validation procedure applying several skill scores. Furthermore, the relative importance of individual predictors has been estimated for each MRM. From these analyses, it can be stated that model skill is improved by (i) the consideration of vorticity characteristics within CTCs, (ii) a relatively small size of the spatial domain to which CTCs are applied and (iii) the inclusion of mean circulation indices. However, model skill exhibits distinct variations between seasons and regions. Whereas promising skill can be stated for the western and northwestern parts of the Central European domain, only unsatisfactory skill is reached in the more continental regions and particularly during summer. Thus, it can be concluded that the presented approaches feature the

  13. Interior Alaska Bouguer Gravity Anomaly

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — A 1 kilometer Complete Bouguer Anomaly gravity grid of interior Alaska. Only those grid cells within 10 kilometers of a gravity data point have gravity values....

  14. Interior Alaska Bouguer Gravity Anomaly

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — A 1 kilometer Complete Bouguer Anomaly gravity grid of interior Alaska. All grid cells within the rectangular data area (from 61 to 66 degrees North latitude and...

  15. 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.

  16. 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)

    LIU ShuHua; LIU ZhenXin; LI Ju; WANG YinChun; MA YanJun; SHENG Li; LIU HePing; LIANG FuMing; XIN GuoJun

    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 morning 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.

  17. 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.

  18. 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)

  19. 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...

  20. 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.

  1. 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

  2. An Observed Connection Between Wintertime Temperature Anomalies over Northwest China and Weather Regime Transitions in North Atlantic

    Institute of Scientific and Technical Information of China (English)

    李超; 张庆云

    2015-01-01

    In this study, the association between wintertime temperature anomalies over Northwest China and the weather regime transitions in North Atlantic on synoptic scale is analyzed by using observational surface air temperature (SAT) data and atmospheric reanalysis data. Daily SAT anomaly and duration time are used in order to defi ne SAT anomaly cases. Diff erences with regard to the circulation anomalies over the Ural Mountains and the upstream North Atlantic area are evident. It is found that the colder than normal SAT is caused by the enhanced Ural high and associated southward fl ow over Northwest China. Time-lagged composites reveal possible connections between the SAT anomalies and the diff erent development phases of the North Atlantic Oscillation (NAO). The Ural highs tend to be strengthened during the negative phase of NAO (NAO–) to Atlantic ridge transition, which are closely related to the downstream-propagating Rossby wave activity. The opposite circulation patterns are observed in the warm SAT cases. A cyclonic circulation anomaly is distinctly enhanced over the Urals during the positive phase of NAO (NAO+) to Scandinavian blocking transition, which would cause warmer SAT over Northwest China. Further analyses suggest that the intensifi ed zonal wind over North Atlantic would favor the NAO–to Atlantic ridge transition, while the weakened zonal wind may be responsible for the transition between NAO+and Scandinavian blocking.

  3. 夏季乌拉尔地区大气环流持续异常的形成与维持%On the Formation and Maintenance of the Persistent Anomalies of Summertime Circulation over the Ural Mountains

    Institute of Scientific and Technical Information of China (English)

    李双林; 纪立人; 林万涛

    2001-01-01

    The formation and maintenance of the persistent anomalies (PA hereafter) of summertime circulation over the Ural Mountains are studied, and a two-way interaction of transient eddies and time-mean flow that may be involved in the evolution of the positive anomaly is demonstrated. Firstly the feature of synoptic-scale transient activity during the PA period is investigated based on composite, and the results suggest a significant enhancement of transient activity over the sector from the central North Atlantic to the coastal western Europe for the positive cases whereas a weakening is for the negative. Numerical simulations are conducted using a barotropic primitive equation model linearized about two time-mean flows, the com posite of positive cases and the climatological July mean respectively. The results show that the enhanced transient activity upstream will favor positive height anomalies over the Ural Mountains. A barotropic stormtrack model is developed, by which the role of time-mean flow in organization and modulation of transient eddies is studied. It is shown that the growth of ridge over the Ural Mountains tends to organize transient eddies into the region upstream from the central North Atlantic to the coastal western Europe. Combining the two aspects, a positive feedback mechanism through two-direction interaction of transient eddies and basic flow is proposed, which can be responsible for the formation and maintenance of the per sistent positive anomalies over the Ural Mountains.%从天气尺度瞬变涡旋与时间平均基本气流双向相互作用建立异常型的角度,研究了夏季乌拉尔地区大气环流持续异常的形成与维持.首先基于合成分析,研究了持续异常期间的天气尺度瞬变波活动情况,结果表明:正异常时,在上游地区,从北大西洋中部到西欧沿岸,瞬变活动明显增强。负异常过程时相反,该地区瞬变活动减弱。利用线性正压原始方程模

  4. Using in-situ observations of atmospheric water vapor isotopes to benchmark and isotope-enabled General Circulation Models and improve ice core paleo-climate reconstruction

    Science.gov (United States)

    Steen-Larsen, Hans Christian; Sveinbjörnsdottir, Arny; Masson-Delmotte, Valerie; Werner, Martin; Risi, Camille; Yoshimura, Kei

    2016-04-01

    We have since 2010 carried out in-situ continuous water vapor isotope observations on top of the Greenland Ice Sheet (3 seasons at NEEM), in Svalbard (1 year), in Iceland (4 years), in Bermuda (4 years). The expansive dataset containing high accuracy and precision measurements of δ18O, δD, and the d-excess allow us to validate and benchmark the treatment of the atmospheric hydrological cycle's processes in General Circulation Models using simulations nudged to reanalysis products. Recent findings from both Antarctica and Greenland have documented strong interaction between the snow surface isotopes and the near surface atmospheric water vapor isotopes on diurnal to synoptic time scales. In fact, it has been shown that the snow surface isotopes take up the synoptic driven atmospheric water vapor isotopic signal in-between precipitation events, erasing the precipitation isotope signal in the surface snow. This highlights the importance of using General or Regional Climate Models, which accurately are able to simulate the atmospheric water vapor isotopic composition, to understand and interpret the ice core isotope signal. With this in mind we have used three isotope-enabled General Circulation Models (isoGSM, ECHAM5-wiso, and LMDZiso) nudged to reanalysis products. We have compared the simulations of daily mean isotope values directly with our in-situ observations. This has allowed us to characterize the variability of the isotopic composition in the models and compared it to our observations. We have specifically focused on the d-excess in order to characterize why both the mean and the variability is significantly lower than our observations. We argue that using water vapor isotopes to benchmark General Circulation Models offers an excellent tool for improving the treatment and parameterization of the atmospheric hydrological cycle. Recent studies have documented a very large inter-model dispersion in the treatment of the Arctic water cycle under a future global

  5. Evaluation of CMIP5 coupled atmosphere-ocean general circulation models over the Southeast Asian winter monsoon in the 20th century

    Science.gov (United States)

    Siew, Jing Huey; Tangang, Fredolin T.; Juneng, Liew

    2014-09-01

    The objective of this present study is to evaluate the performance of ten coupled atmosphere-ocean general circulation models (AOGCMs) from the fifth phase of the Coupled Model Intercomparison Project (CMIP5) based on their capability to simulate the present-day climatology winter monsoon (December-January-February) sea surface temperature (SST) from 1961 to 2000 over the Southeast Asia (SEA) region. The domain of interest covers 11°S-19°N and 92°-132°E. All models simulated the broad features of winter monsoon SST spatial pattern with small spread of bias magnitudes. All models are able to capture the shape of SST annual cycle for both the northern and southern SEA, as the relative peaks and the troughs of the annual cycle of SST were well represented. All models simulated the observed seasonal variation of the surface circulation in the SEA region. The simulated salinity also agrees with the observation except IPSL, CanESM2 and CNRM that gave lower salinity over the South China Sea (SCS). Overall, three AOGCMs, namely CNRM-CM5, MPI-ESM-LR and NorESM1-M simulated the most realistic present-day SST, salinity and surface circulation.

  6. Intensified impact of tropical Atlantic SST on the western North Pacific summer climate under a weakened Atlantic thermohaline circulation

    Science.gov (United States)

    Chen, Wei; Lee, June-Yi; Lu, Riyu; Dong, Buwen; Ha, Kyung-Ja

    2015-10-01

    The tropical North Atlantic (TNA) sea surface temperature (SST) has been identified as one of regulators on the boreal summer climate over the western North Pacific (WNP), in addition to SSTs in the tropical Pacific and Indian Oceans. The major physical process proposed is that the TNA warming induces a pair of cyclonic circulation anomaly over the eastern Pacific and negative precipitation anomalies over the eastern to central tropical Pacific, which in turn lead to an anticyclonic circulation anomaly over the western to central North Pacific. This study further demonstrates that the modulation of the TNA warming to the WNP summer climate anomaly tends to be intensified under background of the weakened Atlantic thermohaline circulation (THC) by using a water-hosing experiment. The results suggest that the weakened THC induces a decrease in thermocline depth over the TNA region, resulting in the enhanced sensitivity of SST variability to wind anomalies and thus intensification of the interannual variation of TNA SST. Under the weakened THC, the atmospheric responses to the TNA warming are westward shifted, enhancing the anticyclonic circulation and negative precipitation anomaly over the WNP. This study supports the recent finding that the negative phase of the Atlantic multidecadal oscillation after the late 1960s has been favourable for the strengthening of the connection between TNA SST variability and WNP summer climate and has important implications for seasonal prediction and future projection of the WNP summer climate.

  7. Rainfall hotspots over the southern tropical Andes : spatial distribution, rainfall intensity, and relations with large-scale atmospheric circulation

    OpenAIRE

    J. C. Espinoza; Chavez, S.; Ronchail, J.; Junquas, Clémentine; K. Takahashi; W. Lavado

    2015-01-01

    The Andes/Amazon transition is among the rainiest regions of the world and the interactions between large-scale circulation and the topography that determine its complex rainfall distribution remain poorly known. This work provides an in-depth analysis of the spatial distribution, variability, and intensity of rainfall in the southern Andes/Amazon transition, at seasonal and intraseasonal time scales. The analysis is based on comprehensive daily rainfall data sets from meteorological stations...

  8. Parameter estimation using data assimilation in an atmospheric general circulation model: From a perfect toward the real world

    OpenAIRE

    Schirber, Sebastian; Klocke, Daniel; Pincus, Robert; Quaas, Johannes; Anderson, Jeffrey L.

    2013-01-01

    This study explores the viability of parameter estimation in the comprehensive general circulation model ECHAM6 using ensemble Kalman filter data assimilation techniques. Four closure parameters of the cumulus-convection scheme are estimated using increasingly less idealized scenarios ranging from perfect-model experiments to the assimilation of conventional observations. Updated parameter values from experiments with real observations are used to assess the error of the model state on short ...

  9. An investigation of a super-Earth exoplanet with a greenhouse-gas atmosphere using a general circulation model

    OpenAIRE

    Zalucha, Angela M.; Michaels, Timothy I.; Madhusudhan, Nikku

    2012-01-01

    We use the Massachusetts Institute of Technology general circulation model (GCM) dynamical core, in conjunction with a Newtonian relaxation scheme that relaxes to a gray, analytical solution of the radiative transfer equation, to simulate a tidally locked, synchronously orbiting super-Earth exoplanet. This hypothetical exoplanet is simulated under the following main assumptions: (1) the size, mass, and orbital characteristics of GJ 1214b (Charbonneau et al., 2009), (2) a greenhouse-gas domina...

  10. 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

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

    OpenAIRE

    M. J. Winnick; J. M. Welker; Chamberlain, C. P.

    2012-01-01

    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 curre...

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

    OpenAIRE

    M. J. Winnick; J. M. Welker; Chamberlain, C. P.

    2013-01-01

    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 e...

  13. Interdecadal Changes in Atmospheric Low-Frequency Variability with and without Boundary Forcing

    OpenAIRE

    Robertson, A.W.; M. Ghil; Latif, Mojib

    2000-01-01

    The response of the Max Planck Institutes ECHAM3 atmospheric general circulation model to a prescribed decade-long positive anomaly in sea surface temperatures (SSTs) over the North Atlantic is investigated. Two 10-yr realizations of the anomaly experiment are compared against a 100-yr control run of the model with seasonally varying climatological SST using a model spatial resolution of T42. In addition to the time-mean response, particular attention is paid to changes in intraseasonal varia...

  14. Heavy rainfall episodes in Ecuador during El Niño events and associated regional atmospheric circulation and SST patterns

    OpenAIRE

    Bendix, A.; Bendix, J.

    2006-01-01

    To date very little is known about the relation between regional circulation patterns and sea surface temperature development in the Niño 1,2 region and the occurrence of heavy precipitation in Ecuador and northern Peru. The current study uses a comprehensive data set of 2544 Meteosat-3 imagery to investigate the dynamics of heavy precipitation during El Niño in 1991/92. Rainfall maps are retrieved by means of an adjusted version of the Convective Stratiform Technique (CST) and Clou...

  15. Low-frequency variability of the atmospheric circulation: a comparison of statistical properties in both hemispheres and extreme seasons

    International Nuclear Information System (INIS)

    A statistical investigation is presented of the main variables characterizing the tropospheric general circulation in both hemispheres and extreme season, Winter and Summer. This gives up the opportunity of comparing four distinct realizations of the planetary circulation, as function of different orographic and thermal forcing conditions. Our approach is made possible by the availability of 6 years of global daily analyses prepared by ECMWF (European Centre for Medium-range Weather Forecast). The variables taken into account are the zonal geostrophic wind, the zonal thermal wind and various large-scala wave components, averaged over the tropospheric depth between 1000 and 200 hPa. The mean properties of the analysed quantities in each hemisphere and season are compared and their principal characteristics are discussed. The probability density estimates for the same variables, filtered in order to eliminate the seasonal cycle and the high frequency 'noise', are then presented. The distributions are examined, in particular, with respect of their unimodal or multimodal nature and with reference to the recent discussion in the literature on the bimodality which has been found for some indicators of planetary wave activity in the Nothern Hemisphere Winter. Our results indicate the presence of nonunimodally distributed wave and zonal flow components in both hemispheres and extreme season. The most frequent occurrence of nonunimodal behaviour is found for those wave components which exhibit an almost vanishing zonal phase speed and a larger 'response' to orographic forcing

  16. 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...

  17. The Role of Warm North Atlantic SST in the Formation of Positive Height Anomalies over the Ural Mountains during January 2008

    Institute of Scientific and Technical Information of China (English)

    HAN Zhe; LI Shuanglin; MU Mu

    2011-01-01

    The most severe snowstorm and freezing-rain event in the past 50 years hit central and southern China in January 2008. One of the nain reasons for the anomalous climate event was the occurrence of atmospheric circulation anomalies over middle and high latitudes, particularly the persistent blocking that occurred over the Ural Mountains. Along with atmospheric anomalies, a strong La Nifia event in the Pacific and warm sea surface temperature anomalies (SSTAs) in the North Atlantic were the most significant in the lower boundary. Since a brief analysis suggests that La Nifia exerts no significant impact on the Urals, the key point of focus in this study is on the role of the warmer SSTAs in the North Atlantic. Based on an observational composite, North Atlantic SSTAs pattern when the height anomaly over the Urals is strongly positive is found similar to that in January 2008, but no significant SSTAs occurred elsewhere, such as the Pacific. Using an atmospheric general circulation model, ECHAM5, the impact of North Atlantic SSTAs on the extratropical atmosphere circulation in the event was investigated. The results show that the warm SSTAs strengthened the blocking high over the Urals, through anomalous transient eddies. The consistency between the study model and the observational composite indicates that the warm SSTAs in the North Atlantic were indeed an important factor in the formation of the snowstorm disaster of January 2008.

  18. 大气环流影响下有机氯农药传输的推断%Inferring Atmospheric Circulation Impact of Organochlorine Pesticides Transmission

    Institute of Scientific and Technical Information of China (English)

    许峰; 祁士华

    2012-01-01

    atmospheric circulation direction, the source of organochlorine pesticides in the atmospheric transmission is also different, and it can not be simply think that it is from low-lying areas to high altitude area. Source and sink of organochlorine pesticides in piateau area would take place because of change of atmospheric circulation.

  19. 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

  20. Montane ecosystem productivity responds more to global circulation patterns than climatic trends

    International Nuclear Information System (INIS)

    Regional ecosystem productivity is highly sensitive to inter-annual climate variability, both within and outside the primary carbon uptake period. However, Earth system models lack sufficient spatial scales and ecosystem processes to resolve how these processes may change in a warming climate. Here, we show, how for the European Alps, mid-latitude Atlantic ocean winter circulation anomalies drive high-altitude summer forest and grassland productivity, through feedbacks among orographic wind circulation patterns, snowfall, winter and spring temperatures, and vegetation activity. Therefore, to understand future global climate change influence to regional ecosystem productivity, Earth systems models need to focus on improvements towards topographic downscaling of changes in regional atmospheric circulation patterns and to lagged responses in vegetation dynamics to non-growing season climate anomalies. (letter)

  1. 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.

  2. 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.

  3. Greenland Ice Sheet influence on Last Interglacial climate: global sensitivity studies performed with an atmosphere-ocean general circulation model

    Science.gov (United States)

    Pfeiffer, Madlene; Lohmann, Gerrit

    2016-06-01

    During the Last Interglacial (LIG, ˜130-115 kiloyears (kyr) before present (BP)), the northern high latitudes were characterized by higher temperatures than those of the late Holocene and a lower Greenland Ice Sheet (GIS). However, the impact of a reduced GIS on the global climate has not yet been well constrained. In this study, we quantify the contribution of the GIS to LIG warmth by performing various sensitivity studies based on equilibrium simulations, employing the Community Earth System Models (COSMOS), with a focus on height and extent of the GIS. We present the first study on the effects of a reduction in the GIS on the surface temperature (TS) on a global scale and separate the contribution of astronomical forcing and changes in GIS to LIG warmth. The strong Northern Hemisphere summer warming of approximately 2 °C (with respect to pre-industrial) is mainly caused by increased summer insolation. Reducing the height by ˜ 1300 m and the extent of the GIS does not have a strong influence during summer, leading to an additional global warming of only +0.24 °C compared to the purely insolation-driven LIG. The effect of a reduction in the GIS is, however, strongest during local winter, with up to +5 °C regional warming and with an increase in global average temperature of +0.48 °C. In order to evaluate the performance of our LIG simulations, we additionally compare the simulated TS anomalies with marine and terrestrial proxy-based LIG temperature anomalies derived from three different proxy data compilations. Our model results are in good agreement with proxy records with respect to the warming pattern but underestimate the magnitude of temperature change when compared to reconstructions, suggesting a potential misinterpretation of the proxy records or deficits in our model. However, we are able to partly reduce the mismatch between model and data by additionally taking into account the potential seasonal bias of the proxy record and/or the uncertainties

  4. Long-term precipitation forecast for drought relief using atmospheric circulation factors: a study on the Maharloo Basin in Iran

    Science.gov (United States)

    Sigaroodi, S. K.; Chen, Q.; Ebrahimi, S.; Nazari, A.; Choobin, B.

    2014-05-01

    Long-term precipitation forecasts can help to reduce drought risk through proper management of water resources. This study took the saline Maharloo Lake, which is located in the north of Persian Gulf, southern Iran, and is continuously suffering from drought disaster, as a case to investigate the relationships between climatic indices and precipitation. Cross-correlation in combination with stepwise regression technique was used to determine the best variables among 40 indices and identify the proper time lag between dependent and independent variables for each month. The monthly precipitation was predicted using an artificial neural network (ANN) and multi-regression stepwise methods, and results were compared with observed rainfall data. Initial findings indicated that climate indices such as NAO (North Atlantic Oscillation), PNA (Pacific North America) and El Niño are the main indices to forecast drought in the study area. According to R2, root mean square error (RMSE) and Nash-Sutcliffe efficiency, the ANN model performed better than the multi-regression model, which was also confirmed by classification results. Moreover, the model accuracy to forecast the rare rainfall events in dry months (June to October) was higher than the other months. From the findings it can be concluded that there is a relationship between monthly precipitation anomalies and climatic indices in the previous 10 months in Maharloo Basin. The highest and lowest accuracy of the ANN model were in September and March, respectively. However, these results are subject to some uncertainty due to a coarse data set and high system complexity. Therefore, more research is necessary to further elucidate the relationship between climatic indices and precipitation for drought relief. In this regard, consideration of other climatic and physiographic factors (e.g., wind and physiography) can be helpful.

  5. A multidecadal simulation of Atlantic tropical cyclones using a variable-resolution global atmospheric general circulation model

    Science.gov (United States)

    Zarzycki, Colin M.; Jablonowski, Christiane

    2014-09-01

    Using a variable-resolution option within the National Center for Atmospheric Research/Department of Energy Community Atmosphere Model (CAM) Spectral Element (SE) global model, a refined nest at 0.25° (˜28 km) horizontal resolution located over the North Atlantic is embedded within a global 1° (˜111 km) grid. The grid is designed such that fine grid cells are located where tropical cyclones (TCs) are observed to occur during the Atlantic TC season (June-November). Two simulations are compared, one with refinement and one control case with no refinement (globally uniform 1° grid). Both simulations are integrated for 23 years using Atmospheric Model Intercomparison Protocols. TCs are tracked using an objective detection algorithm. The variable-resolution simulation produces significantly more TCs than the unrefined simulation. Storms that do form in the refined nest are much more intense, with multiple storms strengthening to Saffir-Simpson category 3 intensity or higher. Both count and spatial distribution of TC genesis and tracks in the variable-resolution simulation are well matched to observations and represent significant improvements over the unrefined simulation. Some degree of interannual skill is noted, with the variable-resolution grid able to reproduce the observed connection between Atlantic TCs and the El Niño-Southern Oscillation (ENSO). It is shown that Genesis Potential Index (GPI) is well matched between the refined and unrefined simulations, implying that the introduction of variable-resolution does not affect the synoptic environment. Potential "upscale" effects are noted in the variable-resolution simulation, suggesting stronger TCs in refined nests may play a role in meridional transport of momentum, heat, and moisture.

  6. 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.

  7. 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.

  8. 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

    2012-05-01

    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. They are most important for congeners of medium hydrophobicity (5–6 chlorine atoms. Their levels are predicted to decrease slowest. Congeners' fractionation is characterized both geographically and temporally. It causes enrichment of the lighter, less persistent congeners and more delayed decreasing levels in high latitudes in response to decreasing emissions. Delivery of 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: trends of decline in abiotic environmental media do not only vary with latitude (slow in high latitudes, but do also show longitudinal gradients

  9. 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.

  10. A new formulation of the atmospheric spectral energy budget, with application to two high-resolution general circulation models

    CERN Document Server

    Augier, Pierre

    2012-01-01

    A new formulation of the spectral energy budget of kinetic and available potential energies of the atmosphere is derived, with spherical harmonics as base functions. Compared to previous formulations, there are three main improvements: (i) the topography is taken into account, (ii) the exact three-dimensional advection terms are considered and (iii) the vertical flux is separated from the energy transfer between different spherical harmonics. Using this formulation, results from two different high resolution GCMs are analyzed: the AFES T639L24 and the ECMWF IFS T1279L91. The spectral fluxes show that the AFES, which reproduces realistic horizontal spectra with a $k^{-5/3}$ inertial range at the mesoscales, simulates a strong downscale energy cascade. % In contrast, neither the $k^{-5/3}$ vertically integrated spectra nor the downscale energy cascade are produced by the ECMWF IFS.

  11. Improved predictability of stratospheric sudden warming events in an atmospheric general circulation model with enhanced stratospheric resolution

    Science.gov (United States)

    Marshall, Andrew G.; Scaife, Adam A.

    2010-08-01

    The impact of stratospheric resolution on the predictability of stratospheric sudden warming (SSW) events and their effect on European climate is cleanly assessed in two versions of the Hadley Center's atmospheric climate model, Hadley Center global environmental model. The standard 38-level version of the model extends to an altitude of 39 km (˜3 mbar) while the extended 60-level version has enhanced stratospheric resolution and reaches 84 km altitude (˜0.004 mbar). We show that the L60 model captures SSW events earlier than the L38 model (12 days before an event compared with 8 days) and influences the simulation of European surface winter cold spells at seasonal time scales, highlighting the benefit of high vertical resolution and daily initialization for seasonal forecasting. This is likely due to earlier initialization of the downward-propagating SSW signal in the higher-top L60 model. We suggest however that the increased lead time for predicting SSW events is unlikely to be improved much further by raising the model lid above the L60 model domain.

  12. Simulated Atlantic Meridional Overturning Circulation in the 20th century with an ocean model forced by reanalysis-based atmospheric data sets

    Science.gov (United States)

    He, Yan-Chun; Drange, Helge; Gao, Yongqi; Bentsen, Mats

    2016-04-01

    Global ocean hindcast simulations for the period 1871-2009 have been run with the ocean-sea ice component of the Norwegian Earth System Model (NorESM-O), forced by an adjusted version of the Twentieth Century Reanalysis version 2 data set (20CRv2 data set), as well as by the commonly used second version of atmospheric forcing data set for the Coordinated Ocean-ice Reference Experiments phase-II (CORE-II) for the period 1948-2007 (hereafter CORE.v2 data set). The simulated Atlantic Meridional Overturning Circulation (AMOC) in the 20CR and the CORE simulations have comparable variability as well as mean strength during the last three decades of the integration. The simulated AMOC undergoes, however, distinctly different evolutions during the period 1948-1970, with a sharply declining strength in CORE but a gradual increase in 20CR. Sensitivity experiments suggest that differences in the wind forcing between CORE and 20CR have major impact on the simulated AMOCs during this period. It is furthermore found that differences in the air temperature between the two data sets do contribute to the differences in AMOC, but to a much lesser degree than the wind. An additional factor for the diverging AMOC in the two decades following 1948 is the inevitable switching of atmospheric forcing fields in 1948 in the CORE.v2-based runs due to the cyclic spin-up procedure of the ocean model. The latter is a fundamental issue for any ocean hindcast simulation. The ocean initial state mainly influence the actual value but to a lesser degree also the temporal evolution (variability) of AMOC. It may take about two decades for the AMOC to adjust to a new atmospheric state during the spin-up, although a dynamically balanced ocean initial state tends to reduce the adjustment time and the magnitude of the deviation, implying that an ocean model run with atmospheric forcing fields extending back in time, like 20CRv2, can be used to extend the reliable duration of CORE-type of simulations.

  13. Global magnetic anomaly and aurora of Neptune

    Science.gov (United States)

    Cheng, Andrew F.

    1990-01-01

    The large offset and tilt of Neptune's dipole magnetic field combine to create a global magnetic anomaly, analogous to but much more important than earth's South Atlantic Anomaly. Energetic particle precipitation loss within the Neptune anomaly creates 'atmospheric drift shadows' within which particle fluxes are greatly reduced. The energetic particle dropout observed by Voyager near closest approach occurred near the predicted times when Voyager passed within the atmospheric drift shadow. Extremely soft, structured bursts of ions and electrons within the drift shadow may result from plasma wave-induced pitch angle scattering of trapped particles confined near the magnetic equator. The dropout does not necessarily imply that Voyager passed through an earth-like discrete auroral zone, as earlier reported. The ion and electron fluxes observed within the dropout period correspond to particles that must precipitate to Neptune's atmosphere within the anomaly region. This anomaly precipitation can account for a major portion of the ultraviolet emissions previously identified as Neptune aurora.

  14. A study into the effect of the diurnal tide on the structure of the background mesosphere and thermosphere using the new coupled middle atmosphere and thermosphere (CMAT general circulation model

    Directory of Open Access Journals (Sweden)

    M. J. Harris

    Full Text Available A new coupled middle atmosphere and thermosphere general circulation model has been developed, and some first results are presented. An investigation into the effects of the diurnal tide upon the mean composition, dynamics and energetics was carried out for equinox conditions. Previous studies have shown that tides deplete mean atomic oxygen in the upper mesosphere-lower thermosphere due to an increased recombination in the tidal displaced air parcels. The model runs presented suggest that the mean residual circulation associated with the tidal dissipation also plays an important role. Stronger lower boundary tidal forcing was seen to increase the equatorial local diurnal maximum of atomic oxygen and the associated 0(1S 557.7 nm green line volume emission rates. The changes in the mean background temperature structure were found to correspond to changes in the mean circulation and exothermic chemical heating.

    Key words. Atmospheric composition and structure (middle atmosphere – composition and chemistry Meterology and atmospheric dynamics (middle atmosphere dynamics; waves and tides

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

    Science.gov (United States)

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

    2016-02-01

    The Dolomite Alps of northeastern Italy experience debris flows with great frequency during the summer months. An ample supply of unconsolidated material on steep slopes and a summer season climate regime characterized by recurrent thunderstorms combine to produce an abundance of these destructive hydro-geologic events. In the past, debris flow events have been studied primarily in the context of their geologic and geomorphic characteristics. The atmospheric contribution to these mass-wasting events has been limited to recording rainfall and developing intensity thresholds for debris mobilization. This study aims to expand the examination of atmospheric processes that preceded both locally intense convective rainfall (LICR) and debris flows in the Dolomite region. 500 hPa pressure level plots of geopotential heights were constructed for a period of 3 days prior to debris flow events to gain insight into the synoptic-scale processes which provide an environment conducive to LICR in the Dolomites. Cloud-to-ground (CG) lightning flash data recorded at the meso-scale were incorporated to assess the convective environment proximal to debris flow source regions. Twelve events were analyzed and from this analysis three common synoptic-scale circulation patterns were identified. Evaluation of CG flashes at smaller spatial and temporal scales illustrated that convective processes vary in their production of CF flashes (total number) and the spatial distribution of flashes can also be quite different between events over longer periods. During the 60 min interval immediately preceding debris flow a majority of cases exhibited spatial and temporal colocation of LICR and CG flashes. Also a number of CG flash parameters were found to be significantly correlated to rainfall intensity prior to debris flow initiation.

  16. 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. A senstitivity study of the ground hydrologic model using data generated by an atmospheric general circulation model. Ph.D. Thesis

    Science.gov (United States)

    Sun, S. F.

    1985-01-01

    The Ground Hydrologic Model (GHM) developed for use in an atmospheric general circulation model (GCM) has been refined. A series of sensitivity studies of the new version of the GHM were conducted for the purpose of understanding the role played by various physical parameters in the GHM. The following refinements have been made: (1) the GHM is coupled directly with the planetary boundary layer (PBL); (2) a bulk vegetation layer is added with a more realistic large-scale parameterization; and (3) the infiltration rate is modified. This version GHM has been tested using input data derived from a GCM simulation run for eight North America regions for 45 days. The results are compared with those of the resident GHM in the GCM. The daily average of grid surface temperatures from both models agree reasonably well in phase and magnitude. However, large difference exists in one or two regions on some days. The daily average evapotranspiration is in general 10 to 30% less than the corresponding value given by the resident GHM.

  19. Wintertime atmospheric response to Atlantic multidecadal variability: effect of stratospheric representation and ocean-atmosphere coupling

    Science.gov (United States)

    Peings, Yannick; Magnusdottir, Gudrun

    2016-08-01

    The impact of the Atlantic multidecadal variability (AMV) on the wintertime atmosphere circulation is investigated using three different configurations of the Community Atmospheric Model version 5 (CAM5). Realistic SST and sea ice anomalies associated with the AMV in observations are prescribed in CAM5 (low-top model) and WACCM5 (high-top model) to assess the dependence of the results on the representation of the stratosphere. In a third experiment, the role of ocean-atmosphere feedback is investigated by coupling CAM5 to a slab-ocean model in which the AMV forcing is prescribed through oceanic heat flux anomalies. The three experiments give consistent results concerning the response of the NAO in winter, with a negative NAO signal in response to a warming of the North Atlantic ocean. This response is found in early winter when the high-top model is used, and in late winter with the low-top model. With the slab-ocean, the negative NAO response is more persistent in winter and shifted eastward over the continent due to the damping of the atmospheric response over the North Atlantic ocean. Additional experiments suggest that both tropical and extratropical SST anomalies are needed to obtain a significant modulation of the NAO, with small influence of sea ice anomalies. Warm tropical SST anomalies induce a northward shift of the ITCZ and a Rossby-wave response that is reinforced in the mid-latitudes by the extratropical SST anomalies through eddy-mean flow interactions. This modeling study supports that the positive phase of the AMV promotes the negative NAO in winter, while illustrating the impacts of the stratosphere and of the ocean-atmosphere feedbacks in the spatial pattern and timing of this response.

  20. Coral Reef Watch, Temperature Anomaly, 50 km

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA Coral Reef Watch distributes SST anomaly data using a combination of the POES AVHRR Global Area Coverage data, and data from a climatological database. AVHRR...

  1. SEG US Bouguer Gravity Anomaly Grid

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The SEG gravity data are the product of the ad hoc Gravity Anomaly Map (GAM) Committee, sponsored by the Society of Exploration Geophysicists (SEG) and the U.S....

  2. Mexico Terrain Corrected Free Air Anomalies (97)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This 2' gravity anomaly grid for Mexico, North-Central America and the Western Caribbean Sea is NOT the input data set used in the development of the MEXICO97...

  3. Comparision of the evolution of the Hadley Circulation between ECMWF ERA-20C centennial reanalysis and the atmospheric model ensemble ERA-20CM

    Science.gov (United States)

    D'Agostino, Roberta; Lionello, Piero

    2016-04-01

    This study compares the evolution of the Hadley Circulation (HC) during the 20th Century in two recent datasets: ERA-20CM and ERA-20C. ERA-20CM is an ensemble of Atmospheric Model simulations forced by 10 different realizations of prescribed SSTs and by radiative forcing that follow CMIP5 protocol. ERA-20C is a single simulation that is similarly forced by the analyzed SST, but it additionally assimilates surface pressure and marine winds. This comparison allows to highlight the effect of the data assimilation on magnitude of the HC trends, and helps to identify differences in the HC structure between reanalysis and AMIP-simulation. The assimilation introduces relevant differences between ERA-20CM and ERA-20C in characteristics and trends of the HCs. In ERA-20C HCs are weaker and the whole Northern Hemisphere HC is shifted southward than in ERA-20CM. Furthermore, the magnitude of trends is larger and more statistically significant in ERA-20C than in ERA-20CM, and only ERA-20C supports a change of the HC strength. Both datasets show large multidecadal variability across 20th Century, which raises doubts on the interpretation of all recent behaviors as the onset of sustained long term trends. However, while the strengthening of the ERA-20C Southern Hemisphere HC is possibly an artifact introduced by data assimilation, the southward shift of the Southern Edge and widening of the Southern Hemisphere HC are robust features in both datasets. The widening of the whole tropical circulation is primary linked to the expansion of the Southern Hemisphere HC and it has accelerated in the last three decades. width of the Southern Hemisphere HCs throughout the 20th Century is mainly correlated to the mean global temperature, but changes in the meridional temperature gradient and planetary wave activity have a role, as well. Furthermore, we integrated the analysis in a long-term perspective with CMIP5 experiments, to analyze HC sensitivity to surface temperature from Last Glacial

  4. Multidecadal variations in Southern Hemisphere atmospheric 14C: Evidence against a Southern Ocean sink at the end of the Little Ice Age CO2 anomaly

    Science.gov (United States)

    Turney, Chris S. M.; Palmer, Jonathan; Hogg, Alan; Fogwill, Christopher J.; Jones, Richard T.; Bronk Ramsey, Christopher; Fenwick, Pavla; Grierson, Pauline; Wilmshurst, Janet; O'Donnell, Alison; Thomas, Zoë A.; Lipson, Mathew

    2016-02-01

    Northern Hemisphere-wide cooling during the Little Ice Age (LIA; 1650-1775 Common Era, C.E.) was associated with a ~5 ppmv decrease in atmospheric carbon dioxide. Changes in terrestrial and ocean carbon reservoirs have been postulated as possible drivers of this relatively large shift in atmospheric CO2, potentially providing insights into the mechanisms and sensitivity of the global carbon cycle. Here we report decadally resolved radiocarbon (14C) levels in a network of tree-ring series spanning 1700-1950 C.E. located along the northern boundary of, and within, the Southern Ocean. We observe regional dilutions in atmospheric radiocarbon (relative to the Northern Hemisphere) associated with upwelling of 14CO2-depleted abyssal waters. We find the interhemispheric 14C offset approaches zero during increasing global atmospheric CO2 at the end of the LIA, with reduced ventilation in the Southern Ocean and a Northern Hemisphere source of old carbon (most probably originating from deep Arctic peat layers). The coincidence of the atmospheric CO2 increase and reduction in the interhemispheric 14C offset imply a common climate control. Possible mechanisms of synchronous change in the high latitudes of both hemispheres are discussed.

  5. NUMERICAL SIMULATION OF SSTA IMPACTS OVER THE GLOBAL OCEAN ON THE ANOMALOUS CIRCULATION OVER EURASIA IN JANUARY 2008

    Institute of Scientific and Technical Information of China (English)

    LI Yan; ZHU Wei-jun

    2010-01-01

    In this paper,we discussed the features of atmospheric circulations over Eurasia as a response to sea surface temperature anomalies (SSTAs) over the tropical Indian Ocean,the equatorial Pacific,Kuroshio and the North Atlantic.Our results are shown as follows:(1) CAM3.0,driven by the combined SSTAs over the four oceanic regions,can simulate well the features of anomalous atmospheric circulations over Eurasia in January 2008,indicating that the effects of the SSTAs over these four regions were one of the key causes of the anomalous systems over Eurasia.(2) The SSTAs over each key region contributed to the intensification of blocking over the Urals Mountains and a main East Asian trough.However,the influence of the SSTAs over individual oceanic regions differed from one another in other aspects.The SSTAs over the North Atlantic had an impact on the 500-hPa anomalous height (Z500A) over the middle-high latitudes and had a somewhat smaller effect over the low latitudes.For the warm SSTAs over Kuroshio,the subtropical high was much stronger,spread farther north than usual,and had an anomalous easterly that dominated the northwest Pacific Ocean.The warm SSTAs over the tropical Indian Ocean could have caused a negative Z500A from West Asia to Middle Asia,a remarkably anomalous southwesterly from the Indian Ocean to the south of China and an anomalous anticyclone circulation over the South China Sea-Philippine Sea region.Because of the La Ni(n)a event,the winter monsoon was stronger than normal,with an anomalously cooler northerly over the southeastern coastal areas of China.(3) The combined effects of the SSTAs over the four key regions were likely more important to the atmospheric circulation anomalies of January 2008 over Eurasia than the effects of individual or partly combined SSTAS.This unique SSTA distribution possibly led to the circulation anomalies over Eurasia in January 2008,especially the atmospheric circulation anomalies over the subtropics,which were more

  6. 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 _ flood control capacity, specifically the excess water volume required to be stored while maintaining dam releases up to the _ 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 _ flood control capacity and was approximately 79.6 - 87.5% of the total reservoir maximum capacity for the discharge peak design scenario.

  7. Parietaria judaica flowering phenology, pollen production, viability and atmospheric circulation, and expansive ability in the urban environment: impacts of environmental factors

    Science.gov (United States)

    Fotiou, Christina; Damialis, Athanasios; Krigas, Nikolaos; Halley, John M.; Vokou, Despoina

    2011-01-01

    Parietaria judaica (Urticaceae) grows abundantly in urban areas of the Mediterranean region. Its pollen is a major allergy source. We studied the species' distribution and abundance in and around Thessaloniki (Greece), pollen production and pollen season. We also examined how urban pollution affects pollen viability. Our ultimate goal was to obtain an estimate of the species' performance and ability to expand under different environmental conditions related to climate change. We mapped P. judaica and the other Urticaceae species. In a north- and a south-facing population, we recorded the progress of P. judaica flowering and estimated the pollen content per flower, shoot and surface unit. We concurrently assessed atmospheric circulation of Urticaceae pollen. We estimated P. judaica pollen viability and Cu, Pb and Zn concentrations in plants collected from sites differing in traffic intensity. P. judaica is the most abundant Urticaceae species in the area; its occurrence has increased dramatically over the last 100 years. Production of flowers is intense in spring and autumn. Flowering started 12 days earlier in the south-facing population in spring, and 3 days later in autumn. Pollen production was higher in spring and in the south-facing population. Flower and pollen production were positively correlated with the size of the plant and the flower, respectively. Copper and lead concentrations in plants were positively correlated with pollen viability, which was higher for plants collected from high-traffic sites. P. judaica has a high phenotypic plasticity; this is a feature that promotes success of expansive and invasive species. It is also well adapted to warm and polluted urban environments. The climatic change forecast for the Mediterranean region could provoke earlier, longer, and more pronounced flowering and, consequently, more P. judaica pollen in the air. In return, this would result in increased severity of Parietaria pollinosis.

  8. Fetal Circulation

    Science.gov (United States)

    ... Pressure High Blood Pressure Tools & Resources Stroke More Fetal Circulation Updated:Jul 8,2016 click to enlarge The ... fetal heart. These two bypass pathways in the fetal circulation make it possible for most fetuses to survive ...

  9. Atmospheric electric field anomalies associated with solar flare/coronal mass ejection events and solar energetic charged particle "Ground Level Events"

    Directory of Open Access Journals (Sweden)

    E. A. Kasatkina

    2009-10-01

    Full Text Available We discuss the fair weather atmospheric electric field signatures of three major solar energetic charged particle events which occurred in on 15 April 2001, 18 April and 4 November, and their causative solar flares/coronal mass ejections (SF/CMEs. Only the 15 April 2001 shows clear evidence for Ez variation associated to SF/CME events and the other two events may support this hypothesis as well although for them the meteorological data were not available. All three events seem to be associated with relativistic solar protons (i.e. protons with energies >450 MeV of the Ground Level Event (GLE type. The study presents data on variations of the vertical component of the atmospheric electric field (Ez measured at the auroral station Apatity (geomagnetic latitude: 63.8°, the polar cap station Vostok (geomagnetic latitude: −89.3° and the middle latitude stations Voyeikovo (geomagnetic latitude: 56.1° and Nagycenk (geomagnetic latitude: 47.2°. A significant disturbance in the atmospheric electric field is sometimes observed close to the time of the causative solar flare; the beginning of the electric field perturbation at Apatity is detected one or two hours before the flare onset and the GLE onset. Atmospheric electric field records at Vostok and Voyeikovo show a similar disturbance at the same time for the 15 April 2001 event. Some mechanisms responsible for the electric field perturbations are considered.

  10. 西藏高原不同时段雪灾的空间分布及大气环流特征%Spatial Distribution of Snow Disaster and Features of Atmospheric Circulation over Tibetan Plateau during 1960-2008

    Institute of Scientific and Technical Information of China (English)

    黄晓清; 杨勇; 石磊

    2013-01-01

    With daily snow cover data collected at 38 meteorological stations in the Tibetan Plateau from October through next April during 1960-2008, we analyzed the spatial distribution of three degrees of snow disasters, classified according to snow depth and snow covering days, in pre-winter, winter and spring. Result showed that there were 3 high-frequency centers of the snow disaster: the middle Himalayas area centered in Nielamu, the eastern Naqu area centered in Jiali and the eastern Himalayas area centered in Cuona. The snow disaster mainly occurred in pre-winter and winter with different frequency distribution. The moderate snow disaster and severe snow disaster mainly occurred in the middle Himalayas area, Ali area and Naqu. A synthesis analysis with NCEP/NCAR monthly mean height field reanalysis data in regional snow a-nomaly years and no snow years showed that the 500 hPa atmospheric circulation at high-latitude in the Northern Hemisphere appeared similar in pre-winter and winter with significant" +-+-" wave train from the Atlantic eastward coast to the western Pacific, and there was a " -+-+-+" wave train from western Europe in the spring. The Long-wave trough and ridge in the European mainland enhanced significantly and the longitude circulation developed in the 3 period. The Eurasia height anomaly fields in pre-winter and winter appeared higher in the west and lower in the east, and in spring showed on the contrary. The intensity and position of the Polar vortex, the Ural mountain high pressure ridge, the Baikal Lake high pressure ridge and North American trough have significant that differences between snow disaster years and non-snow disaster years. The East Asian trough didn't show significant differences except in spring.%利用西藏高原38个气象站自建站以来至2008年的10月至翌年4月逐日积雪资料,依据积雪深度和积雪持续日数两项要素组合的雪灾等级指标,分析了前冬、隆冬和春季3个时段

  11. Study on Indicating Functions of the Atmospheric Circulation Indices and the Sea Surface Temperature for Annual Precipitation Forecast of Hulun Buir Region%大气环流指数和海温对呼伦贝尔地区年降水预测的指示意义

    Institute of Scientific and Technical Information of China (English)

    孙海滨; 高涛

    2012-01-01

    文章对近50a(1961—2010年)内蒙古呼伦贝尔地区的年、汛期和冬春季降水量和降水距平百分率(R%)作了统计,发现年R%和冬春季R%呈上升趋势,汛期R%略呈下降趋势;通过对年R%与大气环流指数、海温的相关分析发现:前期副热带高压(副高)、北半球极涡、大西洋欧洲环流C型、西藏高原位势高度和印缅槽(南支槽)强度指数等均与年R%密切相关,当北半球极涡收缩、强度减弱,副高扩张、强度加强,西藏高原位势高度偏高,南支槽减弱时,有利于来年呼伦贝尔地区降水,否则,相反。此外,前一年夏季北印度洋海域和赤道东太平洋海域海温对呼伦贝尔地区来年降水有显著影响,这两块海区的海温和上述环流指数可考虑作为呼伦贝尔地区年降水的预测信号使用。%The annual, rain-season and winter-spring precipitation and precipitation anomaly in percentage (R%) of Hulun Buir City (Region) in Inner Mongolia, China during the past 50 years (from 1961 to 2010) were calculated in this study. From the result of the calculation, it has been found that the annual and winter-spring R% display a significant increase trend. In opposite, the rain-season R%, however, shows a slight decrease trend during the 50-year period. Besides, it has been found in outcomes of the correlation analyses between the R% and all atmospheric circulation indices that the precious subtropical high (SH), North Polar vortex (NPV), Atlantic and Europe pattern C (Pattern-C), geopotential high of the Tibetan Plateau (GH-TP) and the India-Burma trough (IBT, also called South branch trough) have close connections with the R%. That indicates when the NPV is small and weak, the atmospheric circulation over the Atlantic and European region exhibits the Pattern-C, the GH-TP changes to higher than normal, the IBT is weak, the SH extends to north-westward and becomes strong in the previous time

  12. Chiral anomalies and differential geometry

    Energy Technology Data Exchange (ETDEWEB)

    Zumino, B.

    1983-10-01

    Some properties of chiral anomalies are described from a geometric point of view. Topics include chiral anomalies and differential forms, transformation properties of the anomalies, identification and use of the anomalies, and normalization of the anomalies. 22 references. (WHK)

  13. Surface salinity fields in the Arctic Ocean and statistical approaches to predicting anomalies and patterns

    CERN Document Server

    Chernyavskaya, Ekaterina A; Golden, Kenneth M; Timokhov, Leonid A

    2014-01-01

    Significant salinity anomalies have been observed in the Arctic Ocean surface layer during the last decade. Using gridded data of winter salinity in the upper 50 m layer of the Arctic Ocean for the period 1950-1993 and 2007-2012, we investigated the inter-annual variability of the salinity fields, attempted to identify patterns and anomalies, and developed a statistical model for the prediction of surface layer salinity. The statistical model is based on linear regression equations linking the principal components with environmental factors, such as atmospheric circulation, river runoff, ice processes, and water exchange with neighboring oceans. Using this model, we obtained prognostic fields of the surface layer salinity for the winter period 2013-2014. The prognostic fields demonstrated the same tendencies of surface layer freshening that were observed previously. A phase portrait analysis involving the first two principal components exhibits a dramatic shift in behavior of the 2007-2012 data in comparison ...

  14. Interannual variability of a precipitation gradient along the semi-arid catchment areas for the metropolitan region of Lima- Peru in relation to atmospheric circulation at the mesoscale

    Science.gov (United States)

    Otto, Marco; Seidel, Jochen; Trachte, Katja

    2013-04-01

    following questions. How is the interannual variability of the observed precipitation gradient related to atmospheric circulation east (Amazon basin) and west (south-east Pacific) of the study region? If those relations are quantifiable, are there any forecast potentials for the characteristics of the precipitation gradient during the raining season? The results of the study provide valuable information needed to understand the generation of rainfall in the frame of a case study for the largest metropolitan area that is located at the arid Pacific coast of Peru. This information may also be useful for local managers in order to optimise water resource management and land use strategies.

  15. Lung Circulation.

    Science.gov (United States)

    Suresh, Karthik; Shimoda, Larissa A

    2016-01-01

    The circulation of the lung is unique both in volume and function. For example, it is the only organ with two circulations: the pulmonary circulation, the main function of which is gas exchange, and the bronchial circulation, a systemic vascular supply that provides oxygenated blood to the walls of the conducting airways, pulmonary arteries and veins. The pulmonary circulation accommodates the entire cardiac output, maintaining high blood flow at low intravascular arterial pressure. As compared with the systemic circulation, pulmonary arteries have thinner walls with much less vascular smooth muscle and a relative lack of basal tone. Factors controlling pulmonary blood flow include vascular structure, gravity, mechanical effects of breathing, and the influence of neural and humoral factors. Pulmonary vascular tone is also altered by hypoxia, which causes pulmonary vasoconstriction. If the hypoxic stimulus persists for a prolonged period, contraction is accompanied by remodeling of the vasculature, resulting in pulmonary hypertension. In addition, genetic and environmental factors can also confer susceptibility to development of pulmonary hypertension. Under normal conditions, the endothelium forms a tight barrier, actively regulating interstitial fluid homeostasis. Infection and inflammation compromise normal barrier homeostasis, resulting in increased permeability and edema formation. This article focuses on reviewing the basics of the lung circulation (pulmonary and bronchial), normal development and transition at birth and vasoregulation. Mechanisms contributing to pathological conditions in the pulmonary circulation, in particular when barrier function is disrupted and during development of pulmonary hypertension, will also be discussed. © 2016 American Physiological Society. Compr Physiol 6:897-943, 2016. PMID:27065170

  16. Stochastically-driven multidecadal variability of the Atlantic meridional overturning circulation in CCSM3

    Energy Technology Data Exchange (ETDEWEB)

    Kwon, Young-Oh [Woods Hole Oceanographic Institution, Physical Oceanography Department, Woods Hole, MA (United States); Frankignoul, Claude [Universite Pierre et Marie Curie, LOCEAN/IPSL, Paris (France)

    2012-03-15

    The Atlantic meridional overturning circulation (AMOC) in the last 250 years of the 700-year-long present-day control integration of the Community Climate System Model version 3 with T85 atmospheric resolution exhibits a red noise-like irregular multi-decadal variability with a persistence longer than 10 years, which markedly contrasts with the preceding {proportional_to}300 years of very regular and stronger AMOC variability with {proportional_to}20 year periodicity. The red noise-like multi-decadal AMOC variability is primarily forced by the surface fluxes associated with stochastic changes in the North Atlantic Oscillation (NAO) that intensify and shift northward the deep convection in the Labrador Sea. However, the persistence of the AMOC and the associated oceanic anomalies that are directly forced by the NAO forcing does not exceed about 5 years. The additional persistence originates from anomalous horizontal advection and vertical mixing, which generate density anomalies on the continental shelf along the eastern boundary of the subpolar gyre. These anomalies are subsequently advected by the mean boundary current into the northern part of the Labrador Sea convection region, reinforcing the density changes directly forced by the NAO. As no evidence was found of a clear two-way coupling with the atmosphere, the multi-decadal AMOC variability in the last 250 years of the integration is an ocean-only response to stochastic NAO forcing with a delayed positive feedback caused by the changes in the horizontal ocean circulation. (orig.)

  17. Intraseasonal variability of wintertime frontal activity and its relationship with precipitation anomalies in the vicinity of South America

    Science.gov (United States)

    Blázquez, Josefina; Solman, Silvina A.

    2016-04-01

    The intraseasonal variability of the frontal activity and its connection with the variability of the atmospheric circulation and precipitation in the Southern Hemisphere is studied. The frontal activity is defined as the relative vorticity times the local temperature gradient. A band-pass filter was applied to retain the intraseasonal timescales. An empirical orthogonal function analysis was applied to the filtered frontal activity anomalies. The two main modes show positive and negative centers located mainly over the southern Pacific Ocean and South American sector and are in quadrature with each other. A similar pattern was found when the main modes of intraseasonal variability of the 500 hPa geopotential height were projected on the frontal activity, suggesting that the variability of fronts are influenced by the variability of the large scale atmospheric circulation. Moreover, the precipitation anomalies projected on the main modes of both frontal activity and 500 hPa geopotential height show similar structures, especially over the southern Pacific Ocean and South America, which may indicate that the variability of fronts controls the variability of precipitation. The lagged regression of the time series of the frontal activity areally-averaged over one of the centers of action against the frontal activity anomaly field shows at lags -8 and 8 a similar pattern, suggesting a period of around 17 days for each mode. Moreover, lagged regression between times series of frontal activity and precipitation anomalies reveals an opposite pattern between southeastern South America and southern Chile, being precipitation anomalies over these two regions anti-correlated due to the frontal activity.

  18. 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

  19. Re-emerging ocean temperature anomalies in late-2010 associated with a repeat negative NAO

    Science.gov (United States)

    Taws, Sarah L.; Marsh, Robert; Wells, Neil C.; Hirschi, Joël

    2011-10-01

    Northern Europe was influenced by consecutive episodes of extreme winter weather at the start and end of the 2010 calendar year. A tripole pattern in North Atlantic sea surface temperature anomalies (SSTAs), associated with an exceptionally negative phase of the North Atlantic Oscillation (NAO), characterized both winter periods. This pattern was largely absent at the surface during the 2010 summer season; however equivalent sub-surface temperature anomalies were preserved within the seasonal thermocline throughout the year. Here, we present evidence for the re-emergence of late-winter 2009/10 SSTAs during the following early winter season of 2010/11. The observed re-emergence contributes toward the winter-to-winter persistence of the anomalous tripole pattern. Considering the active influence of the oceans upon leading modes of atmospheric circulation over seasonal timescales, associated with the memory of large-scale sea surface temperature anomaly patterns, the re-emergence of remnant temperature anomalies may have also contributed toward the persistence of a negative winter NAO, and the recurrence of extreme wintry conditions over the initial 2010/11 winter season.

  20. The Lagrangian structure of ozone mini-holes and potential vorticity anomalies in the Northern Hemisphere

    Directory of Open Access Journals (Sweden)

    P. M. James

    Full Text Available An ozone mini-hole is a synoptic-scale area of strongly reduced column total ozone, which undergoes a growth-decay cycle in association with baroclinic weather systems. The tracks of mini-hole events recorded during the TOMS observation period over the Northern Hemisphere provide a database for building anomaly fields of various meteorological parameters, following each mini-hole center in a Lagrangian sense. The resulting fields provide, for the first time, a complete mean Lagrangian picture of the three-dimensional structure of typical ozone mini-holes in the Northern Hemisphere. Mini-holes are shown to be associated with anomalous warm anticyclonic flow in the upper troposphere and cold cyclonic anomalies in the middle stratosphere. Ascending air columns occur upstream and descent downstream of the mini-hole centers. Band-pass filtering is used to reveal the transient synoptic nature of mini-holes embedded within larger scale circulation anomalies. Significant correlations between ozone and Ertel’s potential vorticity on isentropes (IPV both near the tropopause and in the middle stratosphere are shown and then utilized by reconstructing the Lagrangian analysis to follow local IPV anomalies instead of ozone minima. By using IPV as a proxy for ozone, the geopotential anomaly dipolar structure in the vertical characteristic of mini-holes is shown to result from a superposition of two largely independent dynamical components, stratospheric and tropospheric, typically operating on different time scales. Hence, ozone mini-holes may be viewed primarily as phenomena of coincidence.

    Key words. Meteorology and atmospheric dynamics (middle atmosphere dynamics; synoptic-scale meteorology

  1. Tracheobronchial Branching Anomalies

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Min Ji; Kim, Young Tong; Jou, Sung Shick [Soonchunhyang University, Cheonan Hospital, Cheonan (Korea, Republic of); Park, A Young [Soonchunhyang University College of Medicine, Asan (Korea, Republic of)

    2010-04-15

    There are various congenital anomalies with respect to the number, length, diameter, and location of tracheobronchial branching patterns. The tracheobronchial anomalies are classified into two groups. The first one, anomalies of division, includes tracheal bronchus, cardiac bronchus, tracheal diverticulum, pulmonary isomerism, and minor variations. The second one, dysmorphic lung, includes lung agenesis-hypoplasia complex and lobar agenesis-aplasia complex

  2. 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

  3. Determination of summer monsoon onset and its related large-scale circulation characteristics over Pakistan

    Science.gov (United States)

    Latif, M.; Syed, F. S.

    2016-08-01

    The onset of summer monsoon over the Core Monsoon Region of Pakistan (CMRP) has been investigated in this study using observational daily rainfall and Precipitable Water (PW) data sets. An objective criterion is proposed to define monsoon onset dates by employing Precipitation Index and Normalized Precipitable Water Index techniques. The climatological mean summer monsoon onset dates over CMRP based on daily rainfall data sets are observed to be 1 July and 30 June in the station and gridded data sets, respectively. Whereas the daily PW-based climatological mean onset date is 30 June. The year-wise onset dates determined through station and gridded rainfall data sets are very similar but these dates differ in case of PW-based onsets. The evolution of large-scale circulation anomalies and thermodynamic structure leading monsoon onset over Pakistan shows that a strong positive temperature and geopotential height anomalies appear over the northwestern part of the core region in the upper atmosphere. This warm geopotential height anomaly gets strengthen as the monsoon onset approaches. The temperature anomalies are barotropic whereas the geopotential height anomalies are baroclinic with the presence of low level anticyclone over the Tibetan Plateau. A moisture convergence zone along the foothill of Himalayas and low level moisture convergence zone over the north Arabian Sea set the stage for the moisture carrying monsoon winds to blow inland towards CMRP. The moisture is mainly supplied from the Arabian Sea, as the low pressure system approaches CMRP from the Bay of Bengal.

  4. ON STRONG SIGNALS OF MONTHLY PRECIPITATION ANOMALIES IN EARLY RAINING SEASON OF GUANGDONG AND CONCEPTUAL MODELS OF PREDICTION

    Institute of Scientific and Technical Information of China (English)

    林爱兰

    2002-01-01

    Reanalysis data from NCEP/NCAR are used to systematically study preceding signals of monthly precipitation anomalies in the early raining season of Guangdong province, from the viewpoints of 500-hPa geopotential height field, outgoing longwave radiation (OLR) field, sea surface temperature (SST) and fourteen indexes of general circulation depicting atmosphere activity at high, middle and low latitutes. Being multiple tools of information, a number of conceptual models are formulated that are useful for prediction of the magnitude of monthly precipitation (drought, flood and normal conditionss).

  5. Coupling convectively driven atmospheric circulation to surface rotation: Evidence for active methane weather in the observed spin rate drift of Titan

    OpenAIRE

    Mitchell, Jonathan L.

    2008-01-01

    A large drift in the rotation rate of Titan observed by Cassini provided the first evidence of a subsurface ocean isolating the massive core from the icy crust. Seasonal exchange of angular momentum between the surface and atmosphere accounts for the magnitude of the effect, but observations lag the expected signal by a few years. We argue that this time lag is due to the presence of an active methane weather cycle in the atmosphere. An analytic model of the seasonal cycle of atmospheric angu...

  6. High resolution modeling of the cusp density anomaly

    Science.gov (United States)

    Brinkman, D. G.; Walterscheid, R. L.; Clemmons, J. H.

    2013-12-01

    The Earth's magnetospheric cusp provides direct access of energetic particles to the thermosphere causing an ionization anomaly. The energy from these particles along with Joule heating, and ion drag forcing play a direct role in determining the neutral density structure in the cusp region. Measurements by the CHAMP (390-460 km altitudes) have shown a region of strong enhanced density attributed to upwelling caused by the combination of particle and Joule heating. The Streak mission (325-123 km) observed a relative depletion in density in the cusp which was attributed to soft particle precipitation not being adequate to cause upwelling at the lower altitudes sampled by Streak and relatively harder precipitation in adjacent areas. Recent attempts to model the cusp density anomaly with Global Circulation Models (GCM) have focused on extreme cases with forcing extending over latitudinal cusp widths of 4 degrees or more which are at the extreme upper end of the observations. Even at one degree latitudinal resolution the cusp features are marginally captured. More typical cusps widths of 1-2 degrees in latitude require finer resolution to resolve. We use a high-resolution numerical model of the thermosphere to simulate the atmospheric response to the relevant forcing by realistically specifying the particle heating, Joule heating, and ion drag forcing to examine the dependence of the magnitude of the cusp density anomaly and the corresponding wind structure on the characteristics of the forcing in the cusp. We ran simulations for cusp widths of 4 and 2 degrees latitude using a model resolution of 20 km. We found that reducing the cusp width by half reduced the density response in the cusp by half, but that the wind response was only slightly decreased. We compare the model results to CHAMP and Streak observations and assess the relative contributions of these mechanisms in explaining the distinctive features of the observations. Acknowledgements: This research was

  7. General Circulation Modeling of the Jovian stratosphere

    Science.gov (United States)

    Sethunadh, J.; Medvedev, A. S.; Hartogh, P.

    2014-04-01

    The middle atmosphere of Jupiter (1 bar to 1 μ bar) is primarily driven by the heat generated in the interior and by radiative heating and cooling. The stratosphere of Jupiter is less studied, and the mechanisms behind many observed phenomena (e.g.,QQO) in the middle atmosphere as well as the stratospheric circulation patterns remain unknown. We have developed a new General Circulation Model (GCM) to simulate the middle atmospheres of gas giants, which can give important insights to the stratospheric circulation and to the physical and dynamical processes underlying the observed middle atmospheric phenomena.

  8. Coupling convectively driven atmospheric circulation to surface rotation: Evidence for active methane weather in the observed spin rate drift of Titan

    CERN Document Server

    Mitchell, Jonathan L

    2008-01-01

    A large drift in the rotation rate of Titan observed by Cassini provided the first evidence of a subsurface ocean isolating the massive core from the icy crust. Seasonal exchange of angular momentum between the surface and atmosphere accounts for the magnitude of the effect, but observations lag the expected signal by a few years. We argue this time lag is due to the presence of an active methane weather cycle in the atmosphere. An analytic model of the seasonal cycle of atmospheric angular momentum is developed and compared to time-dependent simulations of Titan's atmosphere with and without methane thermodynamics. The disappearance of clouds at the summer pole suggests the drift rate has already switched direction, signaling the change in season from solstice to equinox.

  9. Spatial-temporal variations of dominant drought/flood modes and the associated atmospheric circulation and ocean events in rainy season over the east of China

    Science.gov (United States)

    Huang, Shaoni; Huang, Fei

    2012-06-01

    By using Season-reliant Empirical Orthogonal Function (S-EOF) analysis, three dominant modes of the spatial-temporal evolution of the drought/flood patterns in the rainy season over the east of China are revealed for the period of 1960-2004. The first two leading modes occur during the turnabout phase of El Niño-Southern Oscillation (ENSO) decaying year, but the drought/flood patterns in the rainy season over the east of China are different due to the role of the Indian Ocean (IO). The first leading mode appears closely correlated with the ENSO events. In the decaying year of El Niño, the associated western North Pacific (WNP) anticyclone located over the Philippine Sea persists from the previous winter to the next early summer, transports warm and moist air toward the southern Yangtze River in China, and leads to wet conditions over this entire region. Therefore, the precipitation anomaly in summer exhibits a `Southern Flood and Northern Drought' pattern over East China. On the other hand, the basin-wide Indian Ocean sea surface temperature anomaly (SSTA) plays a crucial role in prolonging the impact of ENSO on the second mode during the ENSO decaying summer. The Indian Ocean basin mode (IOBM) warming persists through summer and unleashes its influence, which forces a Matsuno-Gill pattern in the upper troposphere. Over the subtropical western North Pacific, an anomalous anticyclone forms in the lower troposphere. The southerlies on the northwest flank of this anticyclone increase the moisture transport onto central China, leading to abundant rainfall over the middle and lower reaches of the Yangtze River and Huaihe River valleys. The anomalous anticyclone causes dry conditions over South China and the South China Sea (SCS). The precipitation anomaly in summer exhibits a `Northern Flood and Southern Drought' pattern over East China. Therefore, besides the ENSO event the IOBM is an important factor to influence the drought/flood patterns in the rainy season over

  10. Conformal Anomalies in Hydrodynamics

    CERN Document Server

    Eling, Christopher; Theisen, Stefan; Yankielowicz, Shimon

    2013-01-01

    We study the effect of conformal anomalies on the hydrodynamic description of conformal field theories in four spacetime dimensions. We consider equilibrium curved backgrounds characterized by a time-like Killing vector and construct a local low energy effective action that captures the conformal anomalies. Using as a special background the Rindler spacetime we derive a formula for the effect of the anomaly on the hydrodynamic pressure.

  11. Familial Poland anomaly.

    OpenAIRE

    David, T J

    1982-01-01

    The Poland anomaly is usually a non-genetic malformation syndrome. This paper reports two second cousins who both had a typical left sided Poland anomaly, and this constitutes the first recorded case of this condition affecting more than one member of a family. Despite this, for the purposes of genetic counselling, the Poland anomaly can be regarded as a sporadic condition with an extremely low recurrence risk.

  12. Timing Anomalies Reloaded

    OpenAIRE

    Gebhard, Gernot

    2010-01-01

    Computing tight WCET bounds in the presence of timing anomalies - found in almost any modern hardware architecture - is a major challenge of timing analysis. In this paper, we renew the discussion about timing anomalies, demonstrating that even simple hardware architectures are prone to timing anomalies. We furthermore complete the list of timing-anomalous cache replacement policies, proving that the most-recently-used replacement policy (MRU) also exhibits a domino effect.

  13. Network Traffic Anomaly Detection

    OpenAIRE

    Huang, Hong; Al-Azzawi, Hussein; Brani, Hajar

    2014-01-01

    This paper presents a tutorial for network anomaly detection, focusing on non-signature-based approaches. Network traffic anomalies are unusual and significant changes in the traffic of a network. Networks play an important role in today's social and economic infrastructures. The security of the network becomes crucial, and network traffic anomaly detection constitutes an important part of network security. In this paper, we present three major approaches to non-signature-based network detect...

  14. Inconsistencies in interpreting the atmospheric neutrino anomaly

    Indian Academy of Sciences (India)

    John M LoSecco

    2004-03-01

    We note a discrepancy between the value of $R$ expected on the basis of the muon neutrino angular distribution and the value actually observed. the energy independence of $R$ leads to a fine-tuning problem. This may be indicative of some unaccounted for new physics.

  15. A satellite retrieval of the shortwave heating of the atmosphere and the surface - Relationship to the general circulation, interannual climate variability, and the cryosphere

    Science.gov (United States)

    Charlock, Thomas P.; Smith, G. L.; Rose, Fred G.

    1990-01-01

    Data from several Nimbus-7 instruments and monthly averaged, multilayer delta-Eddington radiative transfer calculations are used to estimate the full vertical profile of the SW heating in the surface and the atmosphere. The noontime physical profile of clouds, water vapor, and surface albedo is used to compute a daily, monthly averaged top-of-atmosphere albedo (TOA), which was produced with noontime Nimbus-7 data, and a profile of SW heating for the atmosphere and surface. The daily, monthly averaged TOA albedo for July 1983 is compared with the ERBE daily, monthly averaged TOA albedo for July 1985. The sensitivity of the vertical SW heating profiles to the retrieval input assumptions is shown.

  16. 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.

  17. Simulation of rainfall anomalies leading to the 2005 drought in Amazonia using the CLARIS LPB regional climate models

    Science.gov (United States)

    Marengo, J.; Chou, S.; Mourao, C.; Solman, S.; Sanchez, E.; Samuelsson, P.; da Rocha, R. P.; Li, L.; Pessacg, N.; Remedio, A. R. C.; Carril, A. F.; F Cavalcanti, I.; Jacob, D.

    2013-12-01

    capture the response to the forcing from the tropical Atlantic during the drought of 2005 in Amazonia. Moreover, extreme climatic conditions in response to anomalous low-level circulation features are also well captured, since the boundary conditions come from reanalysis and the models are largely constrained by the information provided at the boundaries. The analysis of the 2005 drought suggests that when the forcing leading to extreme anomalous conditions is associated with both local and non-local mechanisms (soil moisture feedbacks and remote SST anomalies, respectively) the models are not fully capable of representing these feedbacks and hence, the associated anomalies. The reason may be a deficient reproduction of the land-atmosphere interactions.

  18. Alaska Terrain Corrected Free Air Anomalies (96)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This 2' x 4' gravity anomaly grid for Alaska is NOT the input data set used in development of the GEOID96 model. This gravity grid models the 1.1 million...

  19. Tropical versus high latitude freshwater influence on the Atlantic circulation

    OpenAIRE

    Goelzer, H.; J. Mignot; Levermann, A; Rahmstorf, S.

    2006-01-01

    We investigate the model sensitivity of the Atlantic meridional overturning circulation (AMOC) to anomalous freshwater flux in the tropical and northern Atlantic. Forcing in both locations leads to the same qualitative response: a positive freshwater anomaly induces a weakening of the AMOC and a negative freshwater anomaly strengthens the AMOC. Strong differences arise in the temporal characteristics and amplitude of the response. The advection of the tropical anomaly up to the deep water for...

  20. Competing Orders and Anomalies

    Science.gov (United States)

    Moon, Eun-Gook

    2016-08-01

    A conservation law is one of the most fundamental properties in nature, but a certain class of conservation “laws” could be spoiled by intrinsic quantum mechanical effects, so-called quantum anomalies. Profound properties of the anomalies have deepened our understanding in quantum many body systems. Here, we investigate quantum anomaly effects in quantum phase transitions between competing orders and striking consequences of their presence. We explicitly calculate topological nature of anomalies of non-linear sigma models (NLSMs) with the Wess-Zumino-Witten (WZW) terms. The non-perturbative nature is directly related with the ’t Hooft anomaly matching condition: anomalies are conserved in renormalization group flow. By applying the matching condition, we show massless excitations are enforced by the anomalies in a whole phase diagram in sharp contrast to the case of the Landau-Ginzburg-Wilson theory which only has massive excitations in symmetric phases. Furthermore, we find non-perturbative criteria to characterize quantum phase transitions between competing orders. For example, in 4D, we show the two competing order parameter theories, CP(1) and the NLSM with WZW, describe different universality class. Physical realizations and experimental implication of the anomalies are also discussed.

  1. Anomalies and topology

    International Nuclear Information System (INIS)

    The lectures given cover the topological effects in gauge field theories, fermionic chiral anomalies, and some relationships between the two. Gauge field theories in three and four space-time dimensions are considered. Topological terms as external U(1) functional gauge potential connections in field space are discussed. Both the structure and physical impact of anomalies are described. 17 refs

  2. Anomalies from Immersions

    CERN Document Server

    Ospina, J F

    2001-01-01

    Two forms of anomalies for chiral spinors living on submanifolds of the spacetime are obtained from the integrality theorem for immersions. The first form of the chiral anomaly is the usual for chiral spinors living on D-brane and O-plane intersections, the second form is exotic.

  3. Hawaiian Islands Terrain Corrected Free Air Anomalies (96)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This 2' gravity anomaly grid for the Principal Hawaiian Islands is NOT the input data set used in development of the GEOID96 model. This gravity grid models the...

  4. PR/VI Terrain Corrected Free Air Anomalies (96)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This 2' gravity anomaly grid for the Puerto Rico and the Virgin Islands is NOT the input data set used in development of the GEOID96 model. This gravity grid models...

  5. On the Origin of Multidecadal to Centennial Greenland Temperature Anomalies Over the Past 800 yr

    Science.gov (United States)

    Kobashi, T.; Shindell, D. T.; Kodera, K.; Box, J. E.; Nakaegawa, T.; Kawamura, K.

    2013-01-01

    The surface temperature of the Greenland ice sheet is among the most important climate variables for assessing how climate change may impact human societies due to its association with sea level rise. However, the causes of multidecadal-to-centennial temperature changes in Greenland temperatures are not well understood, largely owing to short observational records. To examine these, we calculated the Greenland temperature anomalies (GTA[G-NH]) over the past 800 yr by subtracting the standardized northern hemispheric (NH) temperature from the standardized Greenland temperature. This decomposes the Greenland temperature variation into background climate (NH); polar amplification; and regional variability (GTA[G-NH]). The central Greenland polar amplification factor as expressed by the variance ratio Greenland/NH is 2.6 over the past 161 yr, and 3.3-4.2 over the past 800 yr. The GTA[G-NH] explains 31-35%of the variation of Greenland temperature in the multidecadal-to-centennial time scale over the past 800 yr. We found that the GTA[G-NH] has been influenced by solar-induced changes in atmospheric circulation patterns such as those produced by the North Atlantic Oscillation/Arctic Oscillation (NAO/AO). Climate modeling and proxy temperature records indicate that the anomaly is also likely linked to solar-paced changes in the Atlantic meridional overturning circulation (AMOC) and associated changes in northward oceanic heat transport.

  6. On the origin of multidecadal to centennial Greenland temperature anomalies over the past 800 yr

    Directory of Open Access Journals (Sweden)

    T. Kobashi

    2013-03-01

    Full Text Available The surface temperature of the Greenland ice sheet is among the most important climate variables for assessing how climate change may impact human societies due to its association with sea level rise. However, the causes of multidecadal-to-centennial temperature changes in Greenland temperatures are not well understood, largely owing to short observational records. To examine these, we calculated the Greenland temperature anomalies (GTA[G-NH] over the past 800 yr by subtracting the standardized northern hemispheric (NH temperature from the standardized Greenland temperature. This decomposes the Greenland temperature variation into background climate (NH; polar amplification; and regional variability (GTA[G-NH]. The central Greenland polar amplification factor as expressed by the variance ratio Greenland/NH is 2.6 over the past 161 yr, and 3.3–4.2 over the past 800 yr. The GTA[G-NH] explains 31–35% of the variation of Greenland temperature in the multidecadal-to-centennial time scale over the past 800 yr. We found that the GTA[G-NH] has been influenced by solar-induced changes in atmospheric circulation patterns such as those produced by the North Atlantic Oscillation/Arctic Oscillation (NAO/AO. Climate modeling and proxy temperature records indicate that the anomaly is also likely linked to solar-paced changes in the Atlantic meridional overturning circulation (AMOC and associated changes in northward oceanic heat transport.

  7. Relationship between Spring Sandstorm Frequency in the Tarim Basin and Atmospheric Circulation%塔里木盆地春季沙尘暴频次与大气环流的关系

    Institute of Scientific and Technical Information of China (English)

    李红军; 杨兴华; 赵勇; 王敏仲; 霍文

    2012-01-01

    The relationship between spring sandstorm frequency in the Tarim Basin and atmospheric circulation is analyzed based on the NCEP/NCAR reanalysis data during 1961-2009 and the monthly sandstorm frequency data from 37 weather stations in Tarim Basin.Results show that their relationship is close.There is significantly negative relationship between spring sandstorm frequency in the Tarim Basin and the atmospheric circulation at 500 hPa geopotential height in the Paris Basin and the middle-west Mongolia;there is positive relationship with atmospheric circulation in the Ural River.The 500 hPa geopotential height increased in the middle-west Mongolia in recent 50 years,decreased in the Ural River;the decrease of longitude circulation between these two areas caused the decrease of sandstorm frequency in the Tarim Basin.The abrupt change of spring sandstorm frequency in the Tarim Basin is associated with the abrupt change of 500 hPa geopotential height in the west of Mongolia,and their variation trend is almost opposite.The abrupt change of sandstorm frequency happened in 1985,but that of the 500 hPa geopotential height happened in 1980 and 1984.The enhancement of 500 hPa geopotential height cyclone in the west Mongolia and anticyclone in the East Europe Plain is the typical circulation situation of frequent sandstorm events in spring in the Tarim Basin.%使用1961—2009年春季NCEP/NCAR再分析资料和塔里木盆地37个气象站沙尘暴频次资料,分析了塔里木盆地春季沙尘暴频次与大气环流的关系。结果表明:①近40a,在500hPa高度场上,两者在巴黎盆地和蒙古国中西部存在显著负相关,在乌拉尔河附近存在正相关,蒙古国中西部500hPa高度场在升高,而乌拉尔地区的在降低,两地间经向环流的减小引起盆地沙尘暴减少。②塔里木盆地春季沙尘暴频次突变与显著负相关区蒙古国西部500hPa高度场突变相联系,两者的变化趋势基本是相反的,盆地

  8. Inferring the depth of the atmospheric circulation on Jupiter and Saturn through gravity measurements by Juno and Cassini and an adjoint based dynamical model

    Science.gov (United States)

    Galanti, Eli; Kaspi, Yohai

    2014-05-01

    In approximately three years Juno and Cassini will both perform close flybys of Jupiter and Saturn respectively, obtaining a high precision gravity spectrum for these planets. This data can be used to estimate the depth of the observed flows on these planets. Here we use a hierarchy of dynamical models in order to relate the three-dimensional flow to perturbations of the density field, and therefore to the gravity field. The models are set up to allow either zonal flow only, or a full horizontal flow in both zonal and meridional directions based on the observed cloud-level winds. In addition, dynamical perturbations resulting from the the non-spherical shape of the planets are accounted for.In order to invert the gravity field to be measured by Juno and Cassini into the 3D circulation, an adjoint model is constructed for the dynamical model, thus allowing backward integration of the dynamical model. This tool can be used for examination of various scenarios, including cases in which the depth of the winds depend on latitudinal position. We show that given the expected sensitivities of Juno and Cassini, it is possible to use the gravity measurements to derive the depth of the winds, both on Jupiter and Saturn. This hold for a large range of zonal wind possible penetration depths, from ~100km to ~10000km, and for winds depth that vary with latitude. This method proves to be useful also when Incorporating the full horizontal flow, and thus taking into account gravity perturbations that vary with longitude. We show that our adjoint based inversion method allows not only to estimate the depth of the circulation, but allows via iterations with the spacecraft trajectory estimation model to improve the inferred gravity field.

  9. Mechanistic analysis of the suppressed convective anomaly precursor associated with the initiation of primary MJO events over the tropical Indian Ocean

    Science.gov (United States)

    Yong, Yangyang; Mao, Jiangyu

    2016-02-01

    A primary Madden-Julian oscillation (MJO) event is one with no immediately preceding MJO event. Most primary MJO events initiating over the tropical Indian Ocean are preceded by a local suppressed convective anomaly (SCA). Based on daily outgoing longwave radiation and atmospheric circulation reanalysis data, composite analyses are performed to reveal the dynamical and thermodynamical mechanisms responsible for the generation of the precursor SCA associated with anomalous descending motion. During the developing stage, before the maximum SCA, the anomalous descending motion in the upper troposphere is dynamically forced by anomalous convergence over the eastern equatorial Indian Ocean. The anomalous convergent winds result from changes in subtropical circulation structures forced by extratropical disturbances in association with equatorward advection of positive potential vorticity. In the lower troposphere, the anomalous stable boundary layer with a strong thermal inversion is the dominant factor leading to descending motion. The sea surface temperature (SST) perturbations in the tropical Indian Ocean are an external forcing that generates the SCA through surface energy exchange. The negative SST anomalies in the northwestern portion of the tropical Indian Ocean act as a heat sink to cool the lower-tropospheric atmosphere, forcing strong descending motion and forming an anomalous anticyclone north of the equator. Meanwhile, the positive SST anomalies in the southeastern portion act as a heat source that forces anomalous divergent westerlies and northwesterlies toward the warmer SST area. Thus, anomalous descending motion is induced around the equator.

  10. 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.

  11. 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.

  12. Observations, inferences, and mechanisms of the Atlantic Meridional Overturning Circulation: A review

    Science.gov (United States)

    Buckley, Martha W.; Marshall, John

    2016-03-01

    This is a review about the Atlantic Meridional Overturning Circulation (AMOC), its mean structure, temporal variability, controlling mechanisms, and role in the coupled climate system. The AMOC plays a central role in climate through its heat and freshwater transports. Northward ocean heat transport achieved by the AMOC is responsible for the relative warmth of the Northern Hemisphere compared to the Southern Hemisphere and is thought to play a role in setting the mean position of the Intertropical Convergence Zone north of the equator. The AMOC is a key means by which heat anomalies are sequestered into the ocean's interior and thus modulates the trajectory of climate change. Fluctuations in the AMOC have been linked to low-frequency variability of Atlantic sea surface temperatures with a host of implications for climate variability over surrounding landmasses. On intra-annual timescales, variability in AMOC is large and primarily reflects the response to local wind forcing; meridional coherence of anomalies is limited to that of the wind field. On interannual to decadal timescales, AMOC changes are primarily geostrophic and related to buoyancy anomalies on the western boundary. A pacemaker region for decadal AMOC changes is located in a western "transition zone" along the boundary between the subtropical and subpolar gyres. Decadal AMOC anomalies are communicated meridionally from this region. AMOC observations, as well as the expanded ocean observational network provided by the Argo array and satellite altimetry, are inspiring efforts to develop decadal predictability systems using coupled atmosphere-ocean models initialized by ocean data.

  13. A morpho-etiological description of congenital limb anomalies.

    Directory of Open Access Journals (Sweden)

    Tayel S

    2005-01-01

    Full Text Available Background: Limb anomalies rank behind congenital heart disease as the most common birth defects observed in infants. More than 50 classifications for limb anomalies based on morphology and osseous anatomy have been drafted over the past 150 years. The present work aims to provide a concise summary of the most common congenital limb anomalies on a morpho-etiological basis. Patients and Methods: In a retrospective study, 70 newborns with anomalies of the upper and/or lower limbs were ascertained through clinical examination, chromosomal analysis, skeletal surveys and other relevant investigations. Results: Fetal causes of limb anomalies represented 55.8% of the cases in the form of 9 cases (12.9% with chromosomal aberrations (trisomy 13, 18 and 21, duplication 13q and deletion 22q and 30 cases (42.9% with single gene disorders. An environmental etiology for limb anomalies was diagnosed in 11 cases (15.7% as amniotic band disruption, monozygotic twin with abnormal circulation, vascular disruption (Poland sequence, sirenomelia and general vascular disruption and an infant with a diabetic mother. Twenty cases (28.5% had limb anomalies as part of sporadic syndromes of unknown etiology. Conclusions: The morpho-etiological work-up of limb anomalies adopted in the present study is valuable for detecting the cause of the anomaly and is crucial for its prevention. Prevention can be achieved by proper genetic counseling, which includes recurrence risk estimation and prenatal diagnosis.

  14. 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)

  15. Anomalies on orbifolds

    Energy Technology Data Exchange (ETDEWEB)

    Arkani-Hamed, Nima; Cohen, Andrew G.; Georgi, Howard

    2001-03-16

    We discuss the form of the chiral anomaly on an S1/Z2 orbifold with chiral boundary conditions. We find that the 4-divergence of the higher-dimensional current evaluated at a given point in the extra dimension is proportional to the probability of finding the chiral zero mode there. Nevertheless the anomaly, appropriately defined as the five dimensional divergence of the current, lives entirely on the orbifold fixed planes and is independent of the shape of the zero mode. Therefore long distance four dimensional anomaly cancellation ensures the consistency of the higher dimensional orbifold theory.

  16. Effects of tropical cyclones on large-scale circulation and ocean heat transport in the South China Sea

    Science.gov (United States)

    Wang, Xidong; Wang, Chunzai; Han, Guijun; Li, Wei; Wu, Xinrong

    2014-12-01

    In this study, we investigate the influence of tropical cyclones (TCs) on large-scale circulation and ocean heat transport in the South China Sea (SCS) by using an ocean general circulation model at a 1/8° resolution during 2000-2008. The model uses a data assimilation system to assimilate observations in order to improve the representation of SCS circulation. The results reveal an unexpected deep SCS circulation anomaly induced by TCs, which suggests that effects of TC can penetrate deeper into the ocean. This deep effect may result from the near inertial oscillations excited by TCs. The inertial oscillations can propagate downward to the oceanic interior. The analyses confirm that TCs have two effects on ocean heat transport of the SCS. Firstly, the wind stress curl induced by TCs affects the structure of SCS circulation, and then changes heat transport. Secondly, TCs pump surface heat downward to the thermocline, increasing the heat injection from the atmosphere to the ocean. Two effects together amplify the outflow of the surface heat southward away the SCS through the Mindoro and Karimata Straits. The TC-induced heat transports through the Mindoro, Balabac and Karimata Straits account for 20 % of the total heat transport through three straits. An implication of this study is that ocean models need to simulate the TC effect on heat transport in order to correctly evaluate the role of the SCS through flow in regulating upper ocean circulation and climate in the Indonesian maritime continent and its adjacent regions.

  17. A monsoon-like Southwest Australian circulation and its relation with rainfall in Southwest Western Australia

    Science.gov (United States)

    Feng, Juan; Li, Jianping; Li, Yun

    2010-05-01

    Using the NCEP/NCAR, ERA-40 reanalysis, and precipitation data from CMAP and Australian Bureau of Meteorology, the variability and circulation features influencing the southwest Western Australia (SWWA) winter rainfall are investigated. It is found that the climate of southwest Australia bears a strong seasonality in the annual cycle and exhibits a monsoon-like atmospheric circulation, which is termed as the southwest Australian circulation (SWAC) for its several distinct features characterizing a monsoonal circulation: the seasonal reversal of winds, alternate wet and dry seasons, and an evident land-sea thermal contrast. The seasonal march of the SWAC in extended winter (May to October) is demonstrated by pentad data. An index based on the dynamics normalized seasonality was introduced to describe the behavior and variation of the winter SWAC. It is found that the winter rainfall over SWWA has a significant positive correlation with the SWAC index in both early (May to July) and late (August to October) winter. In weaker winter SWAC years there is an anti-cyclonic anomaly over southern Indian Ocean resulting in weaker westerlies and northerlies which are not favorable for more rainfall over SWWA, and the opposite combination is true in the stronger winter SWAC years. The SWAC explains not only a large portion of the interannual variability of SWWA rainfall in both early and late winter, but also the long term drying trend over SWWA in early winter. The well-coupled SWAC-SWWA rainfall relationship seems to be largely independent of the well-known effects of large-scale atmospheric circulations such as the Southern Hemisphere Annular Mode (SAM), El Niño/Southern Oscillation (ENSO), Indian Ocean Dipole (IOD) and ENSO Modoki (EM). The result offers qualified support for the argument that the monsoon-like circulation may contribute to the rainfall decline in early winter over SWWA.

  18. The Arctic Amplification and inter-relation between Arctic Sea-Ice, cloud greenhouse heating and atmospheric circulation in ERA-Interim and EC-Earth

    Science.gov (United States)

    Willen, Ulrika; Bintanja, Richard; Sedlar, Joseph; Königk, Torben

    2014-05-01

    The Arctic is warming faster than the global average especially in autumn and winter and substantial reductions in summer and winter sea-ice have been observed recently. It is also the part of the globe where climate model scenarios show the largest spread. The impact of clouds on sea ice and Arctic amplification is not well understood even though an increase in clouds in winter is expected to have a warming effect due to the initial small amounts of cloud condensate and especially in liquid form. Many recent observational data sets report significant amounts of mixed-phase clouds over the Arctic in all seasons. The frequent occurrence of Arctic mixed-phase clouds has important implications for the cloud radiative forcing at the surface, since mixed-phase clouds tend to be optically thicker than ice-only clouds and emit more downward long-wave flux which increases the surface temperature and sea-ice melt. A number of studies have shown that models underestimate the amount of cloud water in Arctic mixed-phase clouds. In this study we investigate how cloudiness affect the Arctic warming and sea-ice retreat in the global coupled climate model EC-Earth for AMIP and transient experiments. We also investigate how the cloud-radiation and sea-ice interactions affect the circulation in EC-Earth and in ERA-Interim reanalysis data.

  19. Theoretically Optimal Distributed Anomaly Detection

    Data.gov (United States)

    National Aeronautics and Space Administration — A novel general framework for distributed anomaly detection with theoretical performance guarantees is proposed. Our algorithmic approach combines existing anomaly...

  20. Numerical experiments on the atmospheric response to cold Equatorial Pacific conditions ('La Nina') during northern summer

    International Nuclear Information System (INIS)

    The effect of cold conditions in the central and eastern Equatorial Pacific during Northern Summer is examined in a series of numerical experiments with the low resolution (T21) atmospheric general circulation model ECHAM2. Anomalous sea surface temperatures (SST) as observed in June 1988 were prescribed and the effect on the global circulation is examined. In the model atmosphere, the anomalous cold water in the Equatorial Pacific excites a strong and stable response over the tropical Central and East Pacific. From here stationary Rossby waves radiate into both hemispheres. The Northern Hemisphere wave train is weak and affects only the Northeast Pacific area; the Southern Hemisphere wave train arches from the Central Pacific over the southern tip of South America to the South Atlantic. This response is not only present in the basic anomaly experiment with the T21 GCM but also in experiments with SST anomalies confined to the tropics and with an envelope-formulation of the SST anomalies, in experiments with a linear model, and in high resolution (T42) model experiments. The model output is also compared to the actually observed atmospheric state in June 1988. (orig./KW)

  1. Learning about Poland Anomaly

    Science.gov (United States)

    ... performed too early, while the individual is growing, asymmetry can result or be made greater than before. ... Anomaly About.com- Poland Syndrome [rarediseases.about.com] Information about Poland syndrome produced by Mary Kugler, M.S. ...

  2. Anomalies and tadpoles

    International Nuclear Information System (INIS)

    We show that massless RR tadpoles in vacuum configurations with open and unoriented strings are always related to anomalies. RR tadpoles arising from sectors of the internal SCFT with non-vanishing Witten index are in one-to-one correspondence with conventional irreducible anomalies. The anomalous content of the remaining RR tadpoles can be disclosed by considering anomalous amplitudes with higher numbers of external legs. We then provide an explicit parametrization of the anomaly polynomial in terms of the boundary reflection coefficients, i.e. one-point functions of massless RR fields on the disk. After factorization of the reducible anomaly, we extract the relevant WZ couplings in the effective lagrangians. (author)

  3. Anomaly Detection in Sequences

    Data.gov (United States)

    National Aeronautics and Space Administration — We present a set of novel algorithms which we call sequenceMiner, that detect and characterize anomalies in large sets of high-dimensional symbol sequences that...

  4. Skyrmions and anomalies

    International Nuclear Information System (INIS)

    The author summarizes the works presented at the meeting on skyrmions and anomalies. He divides the principal issues of this workshop into five categories: QCD effective lagrangians, chiral bags and the Cheshire cat principle, strangeness problem, phenomenology, mathematical structure

  5. Anomalous circulation patterns in association with two types of daily precipitation extremes over southeastern China during boreal summer

    Science.gov (United States)

    Li, Minggang; Guan, Zhaoyong; Jin, Dachao; Han, Jie; Zhang, Qian

    2016-04-01

    Based on the daily rainfall data from China Meteorological Administration, the tropical cyclone (TC) best track data from Japan Meteorological Agency, and the NCEP-NCAR reanalysis data from NOAA, regional mean daily precipitation extreme (RDPE) events over southeastern China (specifically, the Fujian-Jiangxi region (FJR)) and the associated circulation anomalies are investigated. For the summers of 1979-2011, a total of 105 RDPE events are identified, among which 35 are TC-influenced (TCIn-RDPE) and 70 are TC-free events (TCFr-RDPE). Distinct differences between these two types of RDPEs are found in both their statistical features and the related circulation patterns. TCFr-RDPEs usually occur in June, while TCIn-RDPEs mainly take place during July-August. When TCFr-RDPEs happen, a center of the anomalous cyclonic circulation is observed over the FJR, with an anomalous anticyclonic circulation to the south of this region. The warm/moist air flows from the South China Sea (SCS) and western Pacific meet with colder air from the north, forming a narrow convergent belt of water vapor over the FJR. Simultaneously, positive diabatic forcing anomalies are observed over the FJR, whereas negative anomalies appear over both its south and north sides, facilitating the formation and maintenance of the cyclonic circulation anomaly, as well as the upward motion of the atmosphere, over the FJR. When TCIn-RDPEs occur, southeastern China is dominated by a TC-related stronger anomalous cyclonic circulation. An anomalous anticyclonic circulation in the mid and high latitudes north of the FJR exists in the mid and upper troposphere, opposite to the situation during TCFr-RDPE events. Abundant warm/wet air is carried into the FJR from both the Indian Ocean and the SCS, leading to a large amount of latent heat release over the FJR and inducing strong ascending motion there. Furthermore, large differences are also found in the manifestation of Rossby wave energy propagation between these

  6. Anomalies and entanglement entropy

    OpenAIRE

    Nishioka, Tatsuma; Yarom, Amos(Department of Physics, Technion, Haifa, 32000, Israel)

    2016-01-01

    We initiate a systematic study of entanglement and Renyi entropies in the presence of gauge and gravitational anomalies in even-dimensional quantum field theories. We argue that the mixed and gravitational anomalies are sensitive to boosts and obtain a closed form expression for their behavior under such transformations. Explicit constructions exhibiting the dependence of entanglement entropy on boosts is provided for theories on spacetimes with non-trivial magnetic fluxes and (or) non-vanish...

  7. Congenital laryngeal anomalies,

    OpenAIRE

    Rutter, Michael J.

    2014-01-01

    Introduction: It is essential for clinicians to understand issues relevant to the airway management of infants and to be cognizant of the fact that infants with congenital laryngeal anomalies are at particular risk for an unstable airway. Objectives: To familiarize clinicians with issues relevant to the airway management of infants and to present a succinct description of the diagnosis and management of an array of congenital laryngeal anomalies. Methods: Revision article, in which the ma...

  8. The Pioneer Anomaly

    CERN Document Server

    de Diego, Jose A

    2008-01-01

    Analysis of the radio-metric data from Pioneer 10 and 11 spacecrafts has indicated the presence of an unmodeled acceleration starting at 20 AU, which has become known as the Pioneer anomaly. The nature of this acceleration is uncertain. In this paper we give a description of the effect and review some relevant mechanisms proposed to explain the observed anomaly. We also discuss on some future projects to investigate this phenomenon.

  9. Anomalies and gravity

    CERN Document Server

    Mielke, E W

    2006-01-01

    Anomalies in Yang-Mills type gauge theories of gravity are reviewed. Particular attention is paid to the relation between the Dirac spin, the axial current j_5 and the non-covariant gauge spin C. Using diagrammatic techniques, we show that only generalizations of the U(1)- Pontrjagin four--form F^ F= dC arise in the chiral anomaly, even when coupled to gravity. Implications for Ashtekar's canonical approach to quantum gravity are discussed.

  10. Anomalies and gravity

    International Nuclear Information System (INIS)

    Anomalies in Yang-Mills type gauge theories of gravity are reviewed. Particular attention is paid to the relation between the Dirac spin, the axial current j5 and the non-covariant gauge spin C. Using diagrammatic techniques, we show that only generalizations of the U(1)- Pontrjagin four-form F and F = dC arise in the chiral anomaly, even when coupled to gravity. Implications for Ashtekar's canonical approach to quantum gravity are discussed

  11. Volume anomaly in ferrimagnetism

    OpenAIRE

    Pascard, H.; Globus, A.

    1981-01-01

    The volume anomaly ΔV/V due to the magnetic energy corresponding to the exchange interactions is experimentally determined for YIG. The experimental values (from 77 K to Tc) agree with the values deduced from the theoretical expression based on the Néel's theories of volume anomaly and of ferrimagnetism. These results are compared with those obtained by other authors on ferromagnetic and antiferromagnetic materials with localized magnetic moments : a reduced curve is obtained.

  12. Anomalies and Entanglement Entropy

    CERN Document Server

    Nishioka, Tatsuma

    2015-01-01

    We initiate a systematic study of entanglement and Renyi entropies in the presence of gauge and gravitational anomalies in even-dimensional quantum field theories. We argue that the mixed and gravitational anomalies are sensitive to boosts and obtain a closed form expression for their behavior under such transformations. Explicit constructions exhibiting the dependence of entanglement entropy on boosts is provided for theories on spacetimes with non-trivial magnetic fluxes and (or) non-vanishing Pontryagin classes.

  13. 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.

  14. 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.

  15. Aerosol impact on atmospheric meso-scale circulation over the Baltic region: A HARMONIE model case study and verification versus radar data

    Science.gov (United States)

    Palamarchuk, Iuliia; Mahura, Alexander; Ivanov, Sergiy; Ruban, Igor; Pavlova, Hanna

    2015-04-01

    An important goal in operational weather forecasting is an accurate prediction of precipitation on meso-scales. This demands, among the others, detailed representation of aerosol impact on the troposphere. Various direct, semi-direct and indirect effects of aerosols lead to significant changes in amount and distribution of precipitation, especially for weak patterns. Features of the atmosphere sensitivity to aerosols is studied employing the HARMONIE (Hirlam Aladin Regional/Meso-scale Operational NWP In Europe) model. Numerical experiments are performed for the Baltic region during the BaltRad experiment (August 2010). The focus of the study is the life-time of convective cells along with feedbacks from aerosols toward meteorological parameters, physical and dynamical mechanisms responsible for developing of precipitation forecast features, direct and indirect aerosol effects. Numerical results are verified by comparing model microphysics fields versus radar reflectivity.

  16. The Holographic Supercurrent Anomaly

    CERN Document Server

    Chaichian, Masud

    2004-01-01

    The \\gamma-trace anomaly of supersymmetry current in a supersymmetric gauge theory shares a superconformal anomaly multiplet with the chiral R-symmetry anomaly and the Weyl anomaly, and its holographic reproduction is a valuable test to the AdS/CFT correspondence conjecture. We investigate how the \\gamma-trace anomaly of the supersymmetry current of {\\cal N}=1 four-dimensional supersymmetric gauge theory in an {\\cal N}=1 conformal supergravity background can be extracted out from the ${\\cal N}=2$ gauged supergravity in five dimensions. It is shown that the reproduction of this super-Weyl anomaly originates from the following two facts: First the {\\cal N}=2 bulk supersymmetry transformation converts into {\\cal N}=1 superconformal transformation on the boundary, which consists of {\\cal N}=1 supersymmetry transformation and special conformal supersymmetry (or super-Weyl) transformation; second the supersymmetry variation of the bulk action of five-dimensional gauged supergravity is a total derivative. The non-co...

  17. The Holographic Weyl anomaly

    CERN Document Server

    Henningson, M; Henningson, Mans; Skenderis, Kostas

    1998-01-01

    We calculate the Weyl anomaly for conformal field theories that can be described via the adS/CFT correspondence. This entails regularizing the gravitational part of the corresponding supergravity action in a manner consistent with general covariance. Up to a constant, the anomaly only depends on the dimension d of the manifold on which the conformal field theory is defined. We present concrete expressions for the anomaly in the physically relevant cases d = 2, 4 and 6. In d = 2 we find for the central charge c = 3 l/ 2 G_N in agreement with considerations based on the asymptotic symmetry algebra of adS_3. In d = 4 the anomaly agrees precisely with that of the corresponding N = 4 superconformal SU(N) gauge theory. The result in d = 6 provides new information for the (0, 2) theory, since its Weyl anomaly has not been computed previously. The anomaly in this case grows as N^3, where N is the number of coincident M5 branes, and it vanishes for a Ricci-flat background.

  18. Large-scale circulation classification and its links to observed precipitation in the eastern and central Tibetan Plateau

    Science.gov (United States)

    Liu, Wenbin; Wang, Lei; Chen, Deliang; Tu, Kai; Ruan, Chengqing; Hu, Zengyun

    2016-06-01

    The relationship between the large-scale circulation dynamics and regional precipitation regime in the Tibetan Plateau (TP) has so far not been well understood. In this study, we classify the circulation types using the self-organizing maps based on the daily field of 500 hPa geopotential height and link them to the precipitation climatology in the eastern and central TP. By virtue of an objective determining method, 18 circulation types are quantified. The results show that the large amount of precipitation in summer is closely related to the circulation types in which the enhanced and northward shifted subtropical high (SH) over the northwest Pacific and the obvious cyclconic circulation anomaly over the Bay of Bengal are helpful for the Indian summer monsoon and East Asian summer monsoon to take abundant low-latitude moisture to the eastern and southern TP. On the contrary, the dry winter in the central and eastern Tibet corresponds to the circulation types with divergence over the central and eastern TP and the water vapor transportations of East Asian winter monsoon and mid-latitude westerly are very weak. Some circulation types are associated with some well-known circulation patterns/monsoons influencing the TP (e.g. East Atlantic Pattern, El Niño Southern Oscillation, Indian Summer Monsoon and the mid-latitude westerly), and exhibit an overall good potential for explaining the variability of regional seasonal precipitation. Moreover, the climate shift signals in the late 1970s over the eastern Pacific/North Pacific Oceans could also be reflected by both the variability of some circulation types and their correspondingly composite precipitations. This study extends our understandings for the large-scale atmospheric dynamics and their linkages with regional precipitation and is beneficial for the climate change projection and related adaptation activities in the highest and largest plateau in the world.

  19. 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...

  20. Winter daily precipitation in La Plata Basin and circulation patterns in Southern South America

    Science.gov (United States)

    Bettolli, Maria Laura; Clorinda Penalba, Olga; Andrés Krieger, Pablo

    2013-04-01

    La Plata Basin is one of the most important agriculture and hydropower producing regions worldwide, where temporal and spatial variability of precipitation have a significant socio-economic impact. The aim of this work is to analyze the dependence of the daily precipitation in the south of La Plata Basin region on the large-scale circulation in Southern South America and its future projection. Daily mean sea level pressure (SLP) fields from NCEP reanalysis 2 were used to represent observed circulation for the period 1979-1999. The analyzed season was austral winter (June-July-August) for the spatial domain from 15°S to 60°S and from 42.5°W to 90°W. The circulation types were obtained by combining the Principal Component Analysis with the k-means Cluster Analysis. Daily precipitation data was used from the gridded datasets of the Claris LPB Project ("A Europe-South America Network for Climate Change Assessment and Impact Studies in La Plata Basin"). Precipitation fields conditioned by the observed surface circulation were analysed and compared. The results indicate that specific daily circulation patterns can be identified as responsible for a significant contribution to precipitation anomalies. The synoptic structures identified in this work can be associated with daily rainfall over the region of study. The classification scheme is effective not only in discriminating dry and rainy days and subregions of La Plata Basin, but also in differentiating between different thresholds of rainfall intensities. In this sense, the findings of this research help to improve our understanding of the relationship between rainfall variability and atmospheric circulation as defined by an objective classification of circulation types.

  1. Multi-year analysis of the three-dimensional distribution of clouds using CloudSat data and inferences on atmospheric circulation features over the Indian region

    Science.gov (United States)

    Nair, Anish Kumar M.; Rajeev, Kunjukrishnapillai

    2012-07-01

    Bengal during summer monsoon season (characterised by near-absence of clouds upto 7 km) and, for the first time, hypothesis its genesis from a mini-circulation embedded in the mean monsoon flow. Another remarkable feature observed is the strong north-south contrast in the distribution of low-level clouds on either side of the ITCZ, with the omnipresence of non-precipitating low level clouds in the southern hemispheric Indian ocean throughout the year. Latent heat released by precipitating clouds is investigated using data obtained from the Precipitation Radar onboard TRMM.

  2. Support for global climate reorganization during the ''Medieval Climate Anomaly''

    Energy Technology Data Exchange (ETDEWEB)

    Graham, N.E. [Hydrologic Research Center, San Diego, CA (United States); Scripps Institution of Oceanography, La Jolla, CA (United States); Ammann, C.M. [National Center for Atmospheric Research, Boulder, CO (United States); Fleitmann, D. [University of Bern, Institute of Geological Sciences, Bern (Switzerland); University of Bern, Oeschger Centre for Climatic Change Research, Bern (Switzerland); Cobb, K.M. [Georgia Institute of Technology, Atlanta, GA (United States); Luterbacher, J. [Justus-Liebig-University, Giessen (Germany)

    2011-09-15

    Widely distributed proxy records indicate that the Medieval Climate Anomaly (MCA; {proportional_to}900-1350 AD) was characterized by coherent shifts in large-scale Northern Hemisphere atmospheric circulation patterns. Although cooler sea surface temperatures in the central and eastern equatorial Pacific can explain some aspects of medieval circulation changes, they are not sufficient to account for other notable features, including widespread aridity through the Eurasian sub-tropics, stronger winter westerlies across the North Atlantic and Western Europe, and shifts in monsoon rainfall patterns across Africa and South Asia. We present results from a full-physics coupled climate model showing that a slight warming of the tropical Indian and western Pacific Oceans relative to the other tropical ocean basins can induce a broad range of the medieval circulation and climate changes indicated by proxy data, including many of those not explained by a cooler tropical Pacific alone. Important aspects of the results resemble those from previous simulations examining the climatic response to the rapid Indian Ocean warming during the late twentieth century, and to results from climate warming simulations - especially in indicating an expansion of the Northern Hemisphere Hadley circulation. Notably, the pattern of tropical Indo-Pacific sea surface temperature (SST) change responsible for producing the proxy-model similarity in our results agrees well with MCA-LIA SST differences obtained in a recent proxy-based climate field reconstruction. Though much remains unclear, our results indicate that the MCA was characterized by an enhanced zonal Indo-Pacific SST gradient with resulting changes in Northern Hemisphere tropical and extra-tropical circulation patterns and hydroclimate regimes, linkages that may explain the coherent regional climate shifts indicated by proxy records from across the planet. The findings provide new perspectives on the nature and possible causes of the MCA

  3. Numerical Simulation of Atmosphere-Ocean-Sea Ice Interaction During Interannual Cycle in High Northern Latitudes

    Institute of Scientific and Technical Information of China (English)

    LIU Xiying; LIU Hailong; LI Wei; ZHANG Xuehong; YU Rucong; YU Yongqiang

    2008-01-01

    Pacific Ocean and anomalies of cold advection appear in the region near the Atlantic Ocean. Accompanying with these anomalies of warm and cold advection in these two regions, warm and cold anomalies appear respectively. Accordingly, SHF sent to the atmosphere from the sea surface decreases and increases, and SST increases and decreases, SIC decreases and increases in these two regions. When there is an anomaly of high pressure in the inner part of the Arctic Ocean, the former relationships reverse.From these results, it can be deduced that, during the interannual cycle of the coupled atmosphere-ocean system, the variability of large-scale atmospheric circulation plays a dominant role and variations of SST and SIC are mainly responding to that of atmospheric circulation.

  4. The Role of Forcing and Internal Dynamics in explaining the 'Medieval Climate Anomaly'

    Science.gov (United States)

    Goossee, Hugues; Crespin, Elisabeth; Dubinkina, Svetlana; Loutre, Marie-France; Mann, Michael E.; Renssen, Hans; Shindell, Drew

    2012-01-01

    Proxy reconstructions suggest that peak global temperature during the past warm interval known as the Medieval Climate Anomaly (MCA, roughly 950-1250 AD) has been exceeded only during the most recent decades. To better understand the origin of this warm period, we use model simulations constrained by data assimilation establishing the spatial pattern of temperature changes that is most consistent with forcing estimates, model physics and the empirical information contained in paleoclimate proxy records. These numerical experiments demonstrate that the reconstructed spatial temperature pattern of the MCA can be explained by a simple thermodynamical response of the climate system to relatively weak changes in radiative forcing combined with a modification of the atmospheric circulation, displaying some similarities with the positive phase of the so-called Arctic Oscillation, and with northward shifts in the position of the Gulf Stream and Kuroshio currents. The mechanisms underlying the MCA are thus quite different from anthropogenic mechanisms responsible for modern global warming.

  5. The Impact of Devegetated Dune Fields on North American Climate During the Late Medieval Climate Anomaly

    Science.gov (United States)

    Cook, B. I.; Seager, R.; Miller, R. L.

    2011-01-01

    During the Medieval Climate Anomaly, North America experienced severe droughts and widespread mobilization of dune fields that persisted for decades. We use an atmosphere general circulation model, forced by a tropical Pacific sea surface temperature reconstruction and changes in the land surface consistent with estimates of dune mobilization (conceptualized as partial devegetation), to investigate whether the devegetation could have exacerbated the medieval droughts. Presence of devegetated dunes in the model significantly increases surface temperatures, but has little impact on precipitation or drought severity, as defined by either the Palmer Drought Severity Index or the ratio of precipitation to potential evapotranspiration. Results are similar to recent studies of the 1930s Dust Bowl drought, suggesting bare soil associated with the dunes, in and of itself, is not sufficient to amplify droughts over North America.

  6. Summer air temperature anomalies in Europe during the century 1811-1910

    International Nuclear Information System (INIS)

    Solar cycle, volcanic eruptions, sea surface temperature anomalies (ENSO) and increase of the concentration of the greenhouse gases are the main forcing factors in the evolution of the Earth climate. In the present work a study concerning the behaviour of the summer temperatures over Europe during the century 1811-1910 is carried out. The results show the presence of a volcanic signal in the summer temperature during the year following an eruption, even if the anomalous coldest summers do not seem to be driven by the volcanic activity. Finally, the anomalous summers - both very cold and very warm - can be explained in terms of the atmospheric circulation, since cold events seem to be associated to persistent blocking systems and warm events are associated to persistent high-pressure patterns

  7. 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...

  8. A pluvial episode identified in arid Australia during the Medieval Climatic Anomaly

    Science.gov (United States)

    Cohen, T. J.; Nanson, G. C.; Jansen, J. D.; Gliganic, L. A.; May, J.-H.; Larsen, J. R.; Goodwin, I. D.; Browning, S.; Price, D. M.

    2012-11-01

    Optically stimulated luminescence (OSL) ages from a relict shoreline on Lake Callabonna record a major pluvial episode in southern central Australia between 1050 ± 70 and 1100 ± 60 Common Era (CE), within the Medieval Climatic Anomaly (MCA). During this pluvial interval Lake Callabonna filled to 10-12 times the volume of the largest historical filling (1974) and reached maximum depths of 4-5 m, compared to the 0.5-1.0 m achieved today. Until now there has been no direct evidence for the MCA in the arid interior of Australia. A multi-proxy, analogue-based atmospheric circulation reconstruction indicates that the pluvial episode was associated with an anomalous meridional atmospheric circulation pattern over the Southern extratropics, with high sea-level pressure ridges in the central Indian Ocean and Tasman Sea, and a trough extending from the Southern Ocean into central Australia. A major decline in the mobility of the Australian aboriginal hunter-gatherer coincides with this MCA period, in southern central Australia.

  9. Role of atmospheric heat source/sink over the Qinghai- Xizang Plateau in quasi-4- year oscillation of atmosphere- land-ocean interaction

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Using 1961-1995 monthly atmospheric apparent heat source/sink over the Qinghai-Xizang Plateau (QXP) and reanalysis data of NCEP/NCAR, and 1961-1994 monthly SST of UK/GISST2, the statistical study is undertaken on the QXP heat source/sink in relation to both atmospheric circulation in Asia and El Ni?o/La Ni?a events. It is discovered that there exists noticeable interaction in a quasi-4-year period among the of the QXP, low-level me-ridional winds east of the QXP, low-level zonal winds in the equatorial Pacific, SST in the equatorial eastern Pacific, and the circulation at mid and high latitudes north of the QXP. They have difference in phase. The cold source intensity of the QXP in winter favours a low-level meridional wind anomaly to prevail in the mainland of China and its coast east of the QXP and to last until the subsequent autumn. The wind anomaly can induce a low-level zonal wind anomaly of the tropic Pacific that finally affects an El Ni?o/La Ni?a event in the autumn and subsequent winter. The event in autumn/winter has effect on the deep trough position and cold air track of East Asia in next winter that influences the intensity of the QXP winter cold source.

  10. Modelling the wintertime response to upper tropospheric and lower stratospheric ozone anomalies over the North Atlantic and Europe

    Directory of Open Access Journals (Sweden)

    I. Kirchner

    Full Text Available During boreal winter months, mean longitude-dependent ozone changes in the upper troposphere and lower stratosphere are mainly caused by different ozone transport by planetary waves. The response to radiative perturbation induced by these ozone changes near the tropopause on the circulation is unclear. This response is investigated with the ECHAM4 general circulation model in a sensitivity study. In the simulation two different mean January realizations of the ozone field are implemented in ECHAM4. Both ozone fields are estimated on the basis of the observed mean January planetary wave structure of the 1980s. The first field represents a 14-year average (reference, 1979–1992 and the second one represents the mean ozone field change (anomaly, 1988–92 in boreal extra-tropics during the end of the 1980s. The model runs were carried out pairwise, with identical initial conditions for both ozone fields. Five statistically independent experiments were performed, forced with the observed sea surface temperatures for the period 1988 to 1992. The results support the hypothesis that the zonally asymmetric ozone changes of the 80s triggered a systematic alteration of the circulation over the North Atlantic – European region. It is suggested that this feedback process is important for the understanding of the decadal coupling between troposphere and stratosphere, as well as between subtropics and extra-tropics in winter.

    Key words. Meteorology and atmospheric dynamics (general circulation; radiative processes; synoptic-scale meteorology

  11. What shapes mesoscale wind anomalies in coastal upwelling zones?

    Energy Technology Data Exchange (ETDEWEB)

    Boe, Julien [University of California, Department of Atmospheric and Oceanic Sciences, Los Angeles, CA (United States); CNRS/CERFACS, URA 1875, Toulouse (France); Hall, Alex; Qu, Xin; Kapnick, Sarah B. [University of California, Department of Atmospheric and Oceanic Sciences, Los Angeles, CA (United States); Colas, Francois; McWilliams, James C.; Kurian, Jaison [University of California, Institute of Geophysics and Planetary Physics, Los Angeles, CA (United States)

    2011-06-15

    Observational studies have shown that mesoscale variations in sea surface temperature may induce mesoscale variations in wind. In eastern subtropical upwelling regions such as the California coast, this mechanism could be of great importance for the mean state and variability of the climate system. In coastal regions orography also creates mesoscale variations in wind, and the orographic effect may extend more than 100 km offshore. The respective roles of SST/wind links and coastal orography in shaping mesoscale wind variations in nearshore regions is not clear. We address this question in the context of the California Upwelling System, using a high-resolution regional numerical modeling system coupling the WRF atmospheric model to the ROMS oceanic model, as well as additional uncoupled experiments to quantify and separate the effects of SST/wind links and coastal orography on mesoscale wind variations. After taking into account potential biases in the representation of the strength of SST/wind links by the model, our results suggest that the magnitude of mesoscale wind variations arising from the orographic effects is roughly twice that of wind variations associated with mesoscale SST anomalies. This indicates that even in this region where coastal orography is complex and leaves a strong imprint on coastal winds, the role of SST/winds links in shaping coastal circulation and climate cannot be neglected. (orig.)

  12. Dynamical effect of the zonal wind anomalies over the tropical western Pacific on ENSO cycles

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The circulation and zonal wind anomalies in the lower troposphere over the equatorial western Pacific and their roles in the developing and decaying processes of the 1982-1983, 1986-1987, 1991-1992 and 1997-1998 El Nino events and the occurrence of La Nina events are analyzed by using the observed data in this paper. The results show that before the developing stage of these El Nino events, there were cyclonic circulation anomalies in the lower troposphere over the tropical western Pacific, and the anomalies brought the westerly anomalies over the Indonesia and the tropical western Pacific. However, when the El Nino events developed to their mature phase, there were anticyclonic circulation anomalies in the lower troposphere over the tropical western Pacific, and the anomalies made the easterly anomalies appear over the tropical western Pacific. A simple, dynamical model of tropical ocean is used to calculate the response of the equatorial oceanic waves to the observed anomalies of wind stress near the sea surface of the equatorial Pacific during the 1997/98 ENSO cycle, which was the strongest one in the 20th century.It is shown that the zonal wind stress anomalies have an important dynamical effect on the development and decay of this El Nino event and the occurrence of the following La Nina event.

  13. Anomaly Extraction in Networks

    Directory of Open Access Journals (Sweden)

    Mr. Naushad Mujawar

    2014-03-01

    Full Text Available The application detects anomaly in network using techniques like histogram, cloning voting, filtering. To extract anomalous flows, one could build a model describing normal flow characteristics and use the model to identify deviating flows. We can compare flows of packets on network with previous flows, like new flows that were not previously observed or flows with significant increase/decrease in their volume. Identify an anomalous flow that combines and consolidates information from multiple histogram-based anomaly detectors [1] [4] [8]. Compared to other possible approaches. Build a histogram based detector that (i applies histogram cloning[1][4], i.e., maintains multiple randomized histograms to obtain additional views of network traffic[3]; and (ii uses the Kullback-Leibler (KL distance to detect anomalies.

  14. Inter-annual Variations and Trend Analyses of Precipitation and Vapor Isotopes with a Global Isotope Circulation Model and Observations

    Science.gov (United States)

    Yoshimura, K.; Oki, T.

    2006-12-01

    An atmosphere, land, sea surface, and river-coupled global isotope circulation model has been developed and it successfully reproduced spatial distribution of precipitation and vapor isotopes as well as those of "real" daily to inter-annual cycles provided by GNIP. A relationship between ENSO and simulated isotope ratio anomaly shows significant signals in DJF. They show lows in Greenland, southern USA and center of the Pacific, and highs in the northern North America, South America, and center of Asia in El Nino periods. Mostly vice versa in La Nina periods. In low latitude zones, it corresponds with the anomaly variations of precipitation amount, but in high latitudes, isotopes show original information on complex water circulation. Further investigation will be done by the presentation. Long-term trends of anomaly of precipitation isotopes are interesting, too. The observation show significant increase of precipitation isotope ratio over west Europe and the simulation agrees with it. Very simply speaking, when hydrologic cycle is enhanced, precipitation isotope will be increased, because the residence time of vapor becomes shorter. The trends in GNIP and the model is well agreed with Dirmeyer and Brubaker's (2006) finding the increase trend of recycling ratio in Northern Hemisphere. GNIP, we often regard it as "already understood", still has unknown to be tackled with.

  15. Climate Prediction Center (CPC) Area-average 200-hPa Zonal Wind Anomalies

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This is one of the CPC?s Monthly Atmospheric and SST Indices. It is the 200-hPa zonal wind anomalies averaged over the area 5oN ? 5oS, 165oW-110oW. The anomalies...

  16. Congenital laryngeal anomalies,

    Directory of Open Access Journals (Sweden)

    Michael J. Rutter

    2014-12-01

    Full Text Available Introduction: It is essential for clinicians to understand issues relevant to the airway management of infants and to be cognizant of the fact that infants with congenital laryngeal anomalies are at particular risk for an unstable airway. Objectives: To familiarize clinicians with issues relevant to the airway management of infants and to present a succinct description of the diagnosis and management of an array of congenital laryngeal anomalies. Methods: Revision article, in which the main aspects concerning airway management of infants will be analyzed. Conclusions: It is critical for clinicians to understand issues relevant to the airway management of infants.

  17. Overly persistent circulation in climate models contributes to overestimated frequency and duration of heat waves and cold spells

    Science.gov (United States)

    Plavcová, Eva; Kyselý, Jan

    2016-05-01

    The study examines links of summer heat waves and winter cold spells in Central Europe to atmospheric circulation and specifically its persistence in an ensemble of regional climate models (RCMs). We analyse 13 RCMs driven by the ERA-40 reanalysis and compare them against observations over reference period 1971-2000. Using objective classification of circulation types and an efficiency coefficient with a block resampling test, we identify circulation types significantly conducive to heat waves and cold spells. We show that the RCMs have a stronger tendency to group together days with very high or low temperature and tend to simulate too many heat waves and cold spells, especially those lasting 5 days and more. Circulation types conducive to heat waves in summer are characterized by anticyclonic, southerly and easterly flow, with increasing importance of warm advection during heat waves. Winter cold spells are typically associated with easterly and anticyclonic flow, and the onset of cold spells tends to be linked to northerly and cyclonic flow with cold advection. The RCMs are generally able to reproduce the links between circulation and heat waves or cold spells, including the radiation-to-advection effect for heat waves and the opposite advection-to-radiation effect for cold spells. They capture relatively well also changes of mean temperature anomalies during sequences of given circulation types, namely the tendency towards temperature increase (decrease) during those types conducive to heat waves (cold spells). Since mean lengths of all circulation supertypes are overestimated in the RCMs, we conclude that the overly persistent circulation in climate models contributes to the overestimated frequency of long heat waves and cold spells. As these biases are rather general among the examined RCMs and similar drawbacks are likely to be manifested in climate model simulations for the twenty-first century, the results also suggest that climate change scenarios for

  18. Future changes and uncertainties in Asian precipitation simulated by multiphysics and multi-sea surface temperature ensemble experiments with high-resolution Meteorological Research Institute atmospheric general circulation models (MRI-AGCMs)

    Science.gov (United States)

    Endo, Hirokazu; Kitoh, Akio; Ose, Tomoaki; Mizuta, Ryo; Kusunoki, Shoji

    2012-08-01

    This study focuses on projecting future changes in mean and extreme precipitation in Asia, and discusses their uncertainties. Time-slice experiments using a 20-km-mesh atmospheric general circulation (AGCM) were performed both in the present-day (1979-2003) and the future (2075-2099). To assess the uncertainty of the projections, 12 ensemble projections (i.e., combination of 3 different cumulus schemes and 4 different sea surface temperature (SST) change patterns) were conducted using 60-km-mesh AGCMs. For the present-day simulations, the models successfully reproduced the pattern and amount of mean and extreme precipitation, although the model with the Arakawa-Schubert (AS) cumulus scheme underestimated the amount of extreme precipitation. For the future climate simulations, in South Asia and Southeast Asia, mean and extreme precipitation generally increase, but their changes show marked differences among the projections, suggesting some uncertainty in their changes over these regions. In East Asia, northwestern China and Bangladesh, in contrast, mean and extreme precipitation show consistent increases among the projections, suggesting their increases are reliable for this model framework. Further investigation by analysis of variance (ANOVA) revealed that the uncertainty in the precipitation changes in South Asia and Southeast Asia are derived mainly from differences in the cumulus schemes, with an exception in the Maritime Continent where the uncertainty originates mainly from the differences in the SST pattern.