WorldWideScience

Sample records for atmospheric circulation anomalies

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

    Science.gov (United States)

    2017-01-01

    The persistence of atmospheric circulation anomalies over East Asia shows a winter to winter recurrence (WTWR) phenomenon. Seasonal variations in sea level pressure anomalies and surface wind anomalies display significantly different characteristics between WTWR and non-WTWR years. The WTWR years are characterized by the recurrence of both a strong (weak) anomalous Siberian High and an East Asian winter monsoon over two successive winters without persistence through the intervening summer. However, anomalies during the non-WTWR years have the opposite sign between the current and ensuing winters. The WTWR of circulation anomalies contributes to that of surface air temperature anomalies (SATAs), which is useful information for improving seasonal and interannual climate predictions over East Asia and China. In the positive (negative) WTWR years, SATAs are cooler (warmer) over East Asia in two successive winters, but the signs of the SATAs are opposite in the preceding and subsequent winters during the non-WTWR years. PMID:28178351

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

    Science.gov (United States)

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

    2016-10-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2007-12-15

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

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

    Science.gov (United States)

    Semenov, V. A.; Latif, M.

    2015-05-01

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

  5. 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".

  6. 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.

  7. 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.

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

    Science.gov (United States)

    Sorkina, A. I.

    1975-01-01

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

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

    Science.gov (United States)

    Schlichtholz, Pawel

    2016-09-01

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

  10. 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...

  11. 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...

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

    Institute of Scientific and Technical Information of China (English)

    蒋品平; 赵平

    2012-01-01

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

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

    Institute of Scientific and Technical Information of China (English)

    武炳义; 杨琨

    2016-01-01

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

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

    Institute of Scientific and Technical Information of China (English)

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

    2014-01-01

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

  15. 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.

  16. Linkages between Arctic summer circulation regimes and regional sea ice anomalies

    Science.gov (United States)

    Lynch, Amanda H.; Serreze, Mark C.; Cassano, Elizabeth N.; Crawford, Alex D.; Stroeve, Julienne

    2016-07-01

    The downward trend in overall Arctic summer sea ice extent has been substantial, particularly in the last few decades. Departures in ice extent from year to year can be very large, however, in part due to the high variability in summer atmospheric circulation patterns. Anomalies in the Pacific sector ice cover can be partially compensated by anomalies of opposite sign in the Atlantic sector. An assessment of linkages between summer atmospheric patterns and sectoral anomalies in the area of maximum open water north of 70°N demonstrates that there is asymmetry in the mechanisms. Years with low ice extent and high open water fraction are uniformly associated with positive temperature anomalies and southerly flow in both the Atlantic and Pacific sectors. However, years with high extent and low open water fraction in both sectors reveal two dominant mechanisms. Some years with anomalously low maximum open water fraction are associated with negative temperature anomalies and southerly transport—a cool summer pattern that allows ice to persist over larger areas. However, other low open water years are characterized by an "ice factory" mechanism, whereby—even when melting—ice cover is continually replenished by advection from the north.

  17. Temperature extremes in Western Europe and associated atmospheric anomalies

    Science.gov (United States)

    Carvalho, V. A.; Santos, J. A.

    2009-09-01

    This worḱs focal point is the analysis of temperature extremes over Western Europe in the period 1957-2007 and their relationship to large-scale anomalies in the atmospheric circulation patterns. The study is based on temperature daily time series recorded at a set of meteorological stations covering the target area. The large-scale anomalies are analyzed using data from the National Centers for Environmental Prediction reanalysis project. Firstly, a preliminary statistical analysis was undertaken in order to identify data gaps and erroneous values and to check the homogeneity of the time series, using not only elementary statistical approaches (e.g., chronograms, box-plots, scatter-plots), but also a set of non-parametric statistical tests particularly suitable for the analysis of monthly and seasonal mean temperature time series (e.g., Wald-Wolfowitz serial correlation test, Spearman and Mann-Kendall trend tests). Secondly, based on previous results, a selection of the highest quality time series was carried out. Aiming at identifying temperature extremes, we then proceed to the isolation of months with temperature values above or below pre-selected thresholds based on the empirical distribution of each time series. In particular, thresholds are based on percentiles specifically computed for each individual temperature record (data adaptive) and not on fixed values. As a result, a calendar of extremely high and extremely low monthly mean temperatures is obtained and the large-scale atmospheric conditions during each extreme are analyzed. Several atmospheric fields are considered in this study (e.g., 2-m maximum and minimum air temperature, sea level pressure, geopotential height, zonal and meridional wind components, vorticity, relative humidity) at different isobaric levels. Results show remarkably different synoptic conditions for temperature extremes in different parts of Western Europe, highlighting the different dynamical mechanisms underlying their

  18. Strong impacts of the Gulf Stream anomalies on the large-scale atmospheric state

    Science.gov (United States)

    Nakamura, Mototaka; Yamane, Shozo

    2010-05-01

    Geological data and climate simulation models suggest that the North Atlantic Deep Water (NADW) that plays a critical role in the global thermohaline circulation may have gone through major fluctuations in the past, bringing with them major climatic anomalies around the basin. A future collapse of the NADW formation has been a concern, as theories and climate simulation models suggest freshening of the North Atlantic as a result of the carbon dioxide increase in the atmosphere. Meanwhile, attempts to find strong impacts of SST anomalies in the North Atlantic on the large-scale atmospheric state in the data and simulation experiments had not been very successful, casting some doubt on the extent to which the thermohaline circulation fluctuations affect the Northern Hemispheric climate. In an attempt to find evidence of strong impacts of the SST anomalies along the Gulf Stream on the regional and Northern Hemispheric climates, we analyzed the ERA40 reanalysis data and Hadley Centre SST data with the near-surface baroclinicity as the key parameter that connects the extra-tropical SST anomalies with the large-scale atmospheric anomalies. We first calculated EOFs of the near-surface baroclinicity for the domain that covers the North Atlantic storm track for each month. We then compiled anomaly composites of the SST, net surface heat flux, and various atmospheric fields for the positive and negative phases of the first two EOFs for each month. We also compiled composites of the anomalies for the preceding and following months for the first two EOFs. From the above diagnoses, we identified strong impacts of the SST anomalies in the vicinity of the Gulf Stream on the large-scale atmospheric state, mostly in cold months. The scale of the atmospheric anomalies generated is very large, on the order of 1000km to 10000km, spanning the entire hemisphere. Roughly speaking, there are two patterns of atmospheric anomalies. One is characterized by a meridional shift in the

  19. 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.)

  20. 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.

  1. The modeled atmospheric and oceanic response to the South China Sea SST anomaly

    Science.gov (United States)

    Zhu, Xiande; Wu, Lixin; Zhou, Jun; Gao, Jianjun

    2016-10-01

    The sensitivity of the global atmospheric and oceanic response to sea surface temperature anomaly (SSTA) throughout the South China Sea (SCS) is investigated using the Fast Ocean-Atmosphere Model (FOAM). Forced by a warming SST, the experiment explicitly demonstrates that the responses of surface air temperature (SAT) and SST exhibit positive anomalous center over SCS and negative anomalous center over the Northern Pacific Ocean (NPO). The atmospheric response to the warm SST anomalies is characterized by a barotropical anomaly in middle-latitude, leading to a weak subtropical high in summer and a weak Aleutian low in winter. Accordingly, Indian monsoon and eastern Asian monsoon strengthen in summer but weaken in winter as a result of wind convergence owing to the warm SST. It is worth noting that the abnormal signals propagate poleward and eastward away in the form of Rossby Waves from the forcing region, which induces high pressure anomaly. Owing to action of the wind-driven circulation, an anomalous anti-cyclonic circulation is induced with a primary southward current in the upper ocean. An obvious cooling appears over the North Pacific, which can be explained by anomalous meridional cold advection and mixing as shown in the analysises of heat budget and other factors that affect SST.

  2. 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

  3. Investigation of atmospheric anomalies associated with Kashmir and Awaran Earthquakes

    Science.gov (United States)

    Mahmood, Irfan; Iqbal, Muhammad Farooq; Shahzad, Muhammad Imran; Qaiser, Saddam

    2017-02-01

    The earthquake precursors' anomalies at diverse elevation ranges over the seismogenic region and prior to the seismic events are perceived using Satellite Remote Sensing (SRS) techniques and reanalysis datasets. In the current research, seismic precursors are obtained by analyzing anomalies in Outgoing Longwave Radiation (OLR), Air Temperature (AT), and Relative Humidity (RH) before the two strong Mw>7 earthquakes in Pakistan occurred on 8th October 2005 in Azad Jammu Kashmir with Mw 7.6, and 24th September 2013 in Awaran, Balochistan with Mw 7.7. Multi-parameter data were computed based on multi-year background data for anomalies computation. Results indicate significant transient variations in observed parameters before the main event. Detailed analysis suggests presence of pre-seismic activities one to three weeks prior to the main earthquake event that vanishes after the event. These anomalies are due to increase in temperature after release of gases and physical and chemical interactions on earth surface before the earthquake. The parameter variations behavior for both Kashmir and Awaran earthquake events are similar to other earthquakes in different regions of the world. This study suggests that energy release is not concentrated to a single fault but instead is released along the fault zone. The influence of earthquake events on lightning were also investigated and it was concluded that there is a significant atmospheric lightning activity after the earthquake suggesting a strong possibility for an earthquake induced thunderstorm. This study is valuable for identifying earthquake precursors especially in earthquake prone areas.

  4. Quantitative aspect in circulation type classifications - An example based on evaluation of moisture flux anomalies

    Science.gov (United States)

    Müller, Miloslav; Kašpar, Marek

    This paper is motivated by an effort to add a quantitative aspect to the process of classifying circulation types and to enable the comparison of various regions from the viewpoint of the synoptic-dynamical causes of hydro-meteorologically extreme events. First, we stress and demonstrate the necessity of adding a quantitative aspect to the classification process when extreme weather events are being studied or even forecasted on the basis of the classification. We suggest an approach based on the statistical anomalies of a proper meteorological variable. Three-day grid-related means of the zonal and meridional components of moisture flux were used as the criteria for the suggested circulation type classification. The circulation type is determined independently in individual grid points. The direction of the most significant moisture flux anomaly determines the circulation type; the degree of its extremeness enables us to evaluate the conditions quantitatively. Eight circulation types are introduced, corresponding to the cardinal directions, as well as an indistinct type comprised of three-day periods without significant moisture flux anomalies in the vicinity of the grid point. This method was subsequently applied to heavy rain events that occurred in the warmer half-years during 1958-2002 within selected Central-European river basins. We detected four regions with different circulation types responsible for heavy rains and demonstrated a close relationship between the dominant circulation type and the seasonal distribution of heavy rain events in the regions. Events accompanied by anomalies of the ‘direct’ flux of moisture (from the west or south) typically occur in autumn; they dominate in the southeastern Alps (circulation types SW, S, SE). Precipitation events with ‘overturning’ moisture flux (mainly from the north and northeast) are concentrated in high summer. They dominate in northern Austria, the Czech Republic, western Slovakia, and Saxony

  5. 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.

  6. Three-dimensional decomposition method of global atmospheric circulation

    Institute of Scientific and Technical Information of China (English)

    LIU HaiTao; HU ShuJuan; XU Ming; CHOU JiFan

    2008-01-01

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

  7. Atmospheric circulation classification comparison based on wildfires in Portugal

    Science.gov (United States)

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

    2009-04-01

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

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

    Science.gov (United States)

    Peng, P.

    2015-12-01

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

  9. NUCLA Circulating Atmospheric Fluidized Bed Demonstration Project

    Energy Technology Data Exchange (ETDEWEB)

    1992-02-01

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

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

    Science.gov (United States)

    Wills, Samantha; Thompson, David; Ciasto, Laura

    2016-04-01

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

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

    Science.gov (United States)

    Fang, Jiabei; Yang, Xiu-Qun

    2016-09-01

    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

  12. 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.

  13. 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...

  14. Statistics of locally coupled ocean and atmosphere intraseasonal anomalies in Reanalysis and AMIP data

    Directory of Open Access Journals (Sweden)

    M. Peña

    2003-01-01

    Full Text Available We apply a simple dynamical rule to determine the dominant forcing direction in locally coupled ocean-atmosphere anomalies in the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/ NCAR reanalysis data. The rule takes into account the phase relationship between the low-level vorticity anomalies and the Sea Surface Temperature (SST anomalies. Analysis of the frequency of persistent coupled anomalies for five-day average data shows that, in general, the ocean tends to force the atmosphere in the tropics while the atmosphere tends to force the ocean in the extratropics. The results agree well with those obtained independently using lagged correlations between atmospheric and oceanic variables, suggesting that the dynamical rule is generally valid. A similar procedure carried out using data from the NCEP global model run with prescribed SST (in which the coupling is one-way, with the ocean always forcing the atmosphere produces fewer coupled anomalies in the extratropics. They indicate, not surprisingly, an increase in ocean-driving anomalies in the model. In addition, and very importantly, there is a strong reduction of persistent atmosphere-driving anomalies, indicating that the one-way interaction of the ocean in the model run may provide a spurious negative feedback that damps atmospheric anomalies faster than observed.

  15. 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)

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

    Science.gov (United States)

    Jansen, Malte F.

    2017-01-01

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

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

    Science.gov (United States)

    Guentchev, Galina S.; Winkler, Julie A.

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

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

    Science.gov (United States)

    Tan, Xianyu; Showman, Adam

    2016-10-01

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

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

    Science.gov (United States)

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

    2016-04-01

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

  20. 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,…

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

    Science.gov (United States)

    Clark, Martyn P.; Serreze, Mark C.

    2000-10-01

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

  2. Morning glory disc anomaly, midline cranial defects and abnormal carotid circulation: an association worth looking for

    Energy Technology Data Exchange (ETDEWEB)

    Quah, Boon Long [Kandang Kerbau Women' s and Children' s Hospital, Singapore National Eye Centre, Department of Ophthalmology (Singapore); Hamilton, Jill [Hospital for Sick Children, Department of Paediatrics, Toronto, ON (Canada); Blaser, Susan [Hospital for Sick Children, Department of Diagnostic Imaging, Toronto, ON (Canada); Heon, Elise; Tehrani, Nasrin N. [Hospital for Sick Children, Department of Ophthalmology and Vision Sciences, Toronto, ON (Canada)

    2005-05-01

    We report on a 4-year-old boy who presented to the ophthalmology department for assessment of convergent strabismus. Ophthalmic examination showed a left morning glory optic disc anomaly and retinal detachment. Plain films obtained for investigation of short stature prior to ophthalmic examination revealed delayed bone age. Ophthalmological findings prompted CT and MRI imaging and angiographic investigations. Midline cranial defects and abnormal carotid circulation were identified. These findings may be associated with morning glory optic disc anomaly, and their association is often under-recognized. It is important that clinicians and radiologists be aware of this spectrum of disorders, as the vascular abnormalities may predispose the patient to transient ischemic attacks and strokes. Growth delay may result from hypopituitarism. (orig.)

  3. 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.

  4. 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...

  5. Hemispheric Circulation Regimes Associated with Predominant Anomaly Patterns of Wintertime Temperature Distribution over the Far East

    Science.gov (United States)

    Mukougawa, H.; Mabuchi, M.

    2012-12-01

    Characteristics of extratropical planetary flow regimes in the Northern Hemisphere associated with prevailing spatial patterns of temperature anomaly distribution in the winter season (DJF) over the Far East are examined based on 2D phase space spanned by the leading two EOFs of the Far East low-frequency temperature variation by the use of ERA-40 reanalysis dataset from 1957/58 to 2001/02 winter and NOAA OLR dataset from 1979/80 to 2001/02 winter. The first EOF of 10-day low-pass filtered 850-hPa temperature anomaly in the winter season over the Far East (25°N-50°N, 120°E-150°E) represents a coherent temperature variation over the whole domain while the second EOF corresponds to a meridional dipole pattern with a node around 40°N. These two leading EOFs explain 76% of the total temperature variance over the Far East. Regression analysis of 250-hPa height anomaly with respect to the corresponding PCs shows that EOF1 and EOF2 are related to the Eurasian (EU) and the West Pacific (WP) pattern, respectively. The PDF of 850-hPa low-frequency temperature anomaly is estimated by the kernel density estimation method of Kimoto and Ghil (1993) in 2D phase space spanned by the leading 2 PCs. Inhomogeneity of the observed PDF from the bivariate Gaussianity is evaluated by a nonparametric method, and we find the existence of two distinct regimes with significantly greater PDF than the Gaussianity: One regime (regime A) represents an atmospheric state with low temperature anomaly over the whole Far East region, especially over Western Japan. The other regime (regime B) corresponds to a state with a prevailing weak positive temperature anomaly over the Far East. Finally, a composite analysis of 250-hPa height anomaly associated with regime A based on the 2D phase space reveals its time evolution as follows: Blocking developing over the Alaska 15 days (day -15) before the mature phase of regime A has a retrograde phase velocity and resides over the Sea of Okhotsk. After day

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

    Science.gov (United States)

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

    2009-04-01

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

  7. 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

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

    Directory of Open Access Journals (Sweden)

    S. Zhang

    2006-06-01

    Full Text Available Only recently has specific attention been given to culturable bacteria in Tibetan glaciers, but their relation to atmospheric circulation is less understood yet. Here we investigate the seasonal variation of culturable bacteria preserved in a Himalayan ice core. High concentration of culturable bacteria in glacial ice deposited during the pre-monsoon season is attributed to the transportation of continental dust stirred up by the frequent dust storms in Northwest China during spring. This is also confirmed by the spatial distribution of culturable bacteria in Tibetan glaciers. Culturable bacteria deposited during monsoon season are more diverse than other seasons because they derive from both marine air masses and local or regional continental sources. We suggest that microorganisms in Himalayan ice can be used to reconstruct atmospheric circulation.

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

    Science.gov (United States)

    Yiou, P.

    2015-12-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-04-10

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

  11. Effects of atmospheric pressure fluctuations on hill-side coal fires and surface anomalies

    Institute of Scientific and Technical Information of China (English)

    Song Zeyang; Zhu Hongqing; Xu Jiyuan; Qin Xiaofeng

    2015-01-01

    This paper presents numerical studies on the effects of atmospheric pressure fluctuations on hill-side coal fires and their surface anomalies. Based on the single-particle reaction–diffusion model, a formula to estimate oxygen consumption rate at high temperature controlled by oxygen transport is proposed. Daily fluctuant atmospheric pressure was imposed on boundaries, including the abandoned gallery and cracks. Simulated results show that the effects of atmospheric pressure fluctuations on coal fires and surface anomalies depend on two factors: the fluctuant amplitude and the pressure difference between inlet(s) and outlet(s) of the air ventilation system. If the pressure difference is close to the fluctuant amplitude, atmospheric pressure fluctuations greatly enhance gas flow motion and tempera-tures of the combustion zone and outtake(s). If the pressure difference is much larger than the fluctuant amplitude, atmospheric pressure fluctuations exert no impact on underground coal fires and surface anomalies.

  12. 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

  13. 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.

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

    Directory of Open Access Journals (Sweden)

    Zengxin Zhang

    2016-01-01

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

  15. 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.

  16. The Dynamic Plateau Monsoon Index and Its Association with General Circulation Anomalies

    Institute of Scientific and Technical Information of China (English)

    XUN Xueyi; HU Zeyong; MA Yaoming

    2012-01-01

    Based on monthly ECMWF reanalysis-Interim (ERA-Interim) reanalysis data,along with monthly precipitation and temperature data,the Dynamic Plateau Monsoon Index (DPMI) is defined.The results of a contrast analysis of the DPMI versus the Traditional Plateau Monsoon Index (TPMI) are described.The response of general circulation to northern Qinghai-Xizang Plateau summer monsoon anomalies and the correlation of the DPMI with general circulation anomalies are investigated.The results show that,the DPMI reflected meteorological elements better and depicted climate variation more accurately than the TPMI.In years when the plateau summer monsoon is strong,the low over the plateau and the trough near the eastern coast of Asia are deeper and higher than normal over South China.This correlation corresponds to two anomalous cyclones over the plateau and the eastern coast of Asia and an anomalous anticyclone in South China.The plateau and its adjacent regions are affected by anomalous southwesterly winds that transport more moisture to South China and cause more precipitation.The lower reaches of the Yangtze River appear to receive more precipitation by means of the strong westerly water vapor flow transported from the "large triangle affecting the region".In years when the plateau summer monsoon is weak,these are opposite.The plateau monsoon is closely related to the intensity and position of the South Asian high,and the existence of a teleconnection pattern in the mid-upper levels suggests a possible linl~ge of the East Asian monsoon and the Indian monsoon to the plateau summer monsoon.

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

    Science.gov (United States)

    Wu, Qianru; Hu, Qi

    2015-01-01

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

  18. The stationary wave response to a midlatitude SST anomaly in an idealized GCM. [SST (sea surface temperature); GCM (general circulation model)

    Energy Technology Data Exchange (ETDEWEB)

    Ting, M. (Univ. of Colorado, Boulder, CO (United States))

    1991-05-15

    The atmospheric stationary wave response to a midlatitude sea surface temperature (SST) anomaly is examined with an idealized general circulation model (GCM) as well as steady linear model, in a similar way as Ting and Held, for a tropical SST anomaly. The control climate of the GCM is zonally symmetric; this symmetric climate is then perturbed by a monopole SST anomaly centered at 40[degrees]N. Two experiments, with SST anomalies of opposite sign, have been conducted. The stationary response is roughly linear in the sign of the SST anomaly, despite the fact that precipitation shows strong nonlinearity. The linear model, which is in exact linearization of the GCM equations in use, when forced by anomalous heating and transients, reproduces the GCM's stationary response excellently. The low-level transient eddy heat fluxes act to damp the lower level temperature signal. When this damping effect is mimicked by a horizontal thermal diffusion in the linear model, the response to the diabatic heating alone gives a reasonably good simulation of the GCm's anomaly; the effect of the anomalous transient momentum fluxes is relatively small. A crude latent heat parameterization scheme, using an evaporation anomaly that is proportional to the mean air-sea surface moisture difference and including the effects of mean moisture advection, is developed. When the perturbation mixing ratio is approximated by assuming fixed relative humidity and by linearizing the Clausius-Clapeyron equation, the linear model's response, utilizing this latent heat parameterization scheme, gives a useful fit to the GCM's anomalous flow. 22 refs., 94 figs.

  19. 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.

  20. 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...

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2011-12-15

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

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

    Science.gov (United States)

    Hwang, Yen-Ting

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

  3. Large sulfur-isotope anomaly in nonvolcanic sulfate aerosol and its implications for the Archean atmosphere.

    Science.gov (United States)

    Shaheen, Robina; Abaunza, Mariana M; Jackson, Teresa L; McCabe, Justin; Savarino, Joël; Thiemens, Mark H

    2014-08-19

    Sulfur-isotopic anomalies have been used to trace the evolution of oxygen in the Precambrian atmosphere and to document past volcanic eruptions. High-precision sulfur quadruple isotope measurements of sulfate aerosols extracted from a snow pit at the South Pole (1984-2001) showed the highest S-isotopic anomalies (Δ(33)S = +1.66‰ and Δ(36)S = +2‰) in a nonvolcanic (1998-1999) period, similar in magnitude to Pinatubo and Agung, the largest volcanic eruptions of the 20th century. The highest isotopic anomaly may be produced from a combination of different stratospheric sources (sulfur dioxide and carbonyl sulfide) via SOx photochemistry, including photoexcitation and photodissociation. The source of anomaly is linked to super El Niño Southern Oscillation (ENSO) (1997-1998)-induced changes in troposphere-stratosphere chemistry and dynamics. The data possess recurring negative S-isotope anomalies (Δ(36)S = -0.6 ± 0.2‰) in nonvolcanic and non-ENSO years, thus requiring a second source that may be tropospheric. The generation of nonvolcanic S-isotopic anomalies in an oxidizing atmosphere has implications for interpreting Archean sulfur deposits used to determine the redox state of the paleoatmosphere.

  4. 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.

  5. Midlatitude atmospheric responses to Arctic sensible heat flux anomalies in Community Climate Model, Version 4

    Science.gov (United States)

    Mills, Catrin M.; Cassano, John J.; Cassano, Elizabeth N.

    2016-12-01

    Possible linkages between Arctic sea ice loss and midlatitude weather are strongly debated in the literature. We analyze a coupled model simulation to assess the possibility of Arctic ice variability forcing a midlatitude response, ensuring consistency between atmosphere, ocean, and ice components. We work with weekly running mean daily sensible heat fluxes with the self-organizing map technique to identify Arctic sensible heat flux anomaly patterns and the associated atmospheric response, without the need of metrics to define the Arctic forcing or measure the midlatitude response. We find that low-level warm anomalies during autumn can build planetary wave patterns that propagate downstream into the midlatitudes, creating robust surface cold anomalies in the eastern United States.

  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. 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

  8. 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.

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

    Directory of Open Access Journals (Sweden)

    Masayo Ogi

    2016-10-01

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

  10. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2001-08-01

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

  12. 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

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

    Science.gov (United States)

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

    2009-09-01

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

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

    Institute of Scientific and Technical Information of China (English)

    王嘉; 郭裕福

    2004-01-01

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

  15. 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.

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

    Science.gov (United States)

    Lin, Jianshe

    2016-04-01

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

  17. Superdominant Right Coronary Artery with Absence of Left Circumflex and Anomalous Origin of the Left Anterior Descending Coronary from the Right Sinus: An Unheard Coronary Anomaly Circulation

    Directory of Open Access Journals (Sweden)

    Marcos Danillo Peixoto Oliveira

    2015-01-01

    Full Text Available Coronary artery anomalies are congenital changes in their origin, course, and/or structure. Most of them are discovered as incidental findings during coronary angiographic studies or at autopsies. We present herein the case of a 70-year-old man with symptomatic severe aortic valvar stenosis whose preoperative coronary angiogram revealed a so far unreported coronary anomaly circulation pattern.

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

    Science.gov (United States)

    Zheleznova, Irina; Gushchina, Daria

    2015-04-01

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

  19. 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...

  20. 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

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

    Science.gov (United States)

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

    2016-09-01

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

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

    Science.gov (United States)

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

    2014-12-01

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

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

    Science.gov (United States)

    Stryhal, Jan; Huth, Radan

    2016-04-01

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

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

    Institute of Scientific and Technical Information of China (English)

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

    2007-01-01

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

  5. 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.

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

    CERN Document Server

    Koll, Daniel D B

    2016-01-01

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

  7. 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.

  8. 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.

  9. 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.

  10. 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).

  11. Linked Extreme Weather Events during Winter 2009-2010 and 2010-2011 in the Context of Northern Hemisphere Circulation Anomalies

    Science.gov (United States)

    Bosart, L. F.; Archambault, H. M.; Cordeira, J. M.

    2011-12-01

    Lance F. Bosart, Heather M. Archambault, and Jason M. Cordeira Department of Atmospheric and Environmental Sciences, University at Albany, State University of New York, Albany, New York The Northern Hemisphere (NH) planetary-scale circulation during winter 2009-2010 was characterized by an unusual combination of persistent high-latitude blocking and southward-displaced storm tracks, manifest by a strongly negative Arctic Oscillation (AO), in conjunction with a moderate El Nino event. The high-latitude blocking activity and southward-displaced storm tracks supported episodic cold-air outbreaks and enhanced storminess over parts of midlatitude eastern Asia, eastern North America, and western Europe as well as anomalous warmth over northeastern Canada and Greenland that delayed sea ice formation and ice thickening in these areas during winter 2009-2010. Although somewhat less extreme than winter 2009-2010, the first half of winter 2010-2011 was also characterized by high-latitude blocking and southward-displaced storm tracks (manifest by negative values of the AO) while the Pacific-North American (PNA), initially negative, became neutral in late December and most of January. Winter 2010-2011 was characterized by moderate La Nina conditions in contrast to moderate El Nino conditions that prevailed during winter 2009-2010. Despite the reversal of the ENSO phase from winter 2009-2010 to winter 2010-2011, high-latitude blocking activity and the associated southward-displaced storm tracks again allowed for episodic cold-air outbreaks and enhanced storminess over parts of midlatitude eastern Asia, central and eastern North America, and western Europe with delayed sea ice formation and thickening over the Davis Strait and adjacent regions during the first half of winter 2010-2011. Beginning in late January and continuing through early February 2011 the phase of the AO and the PNA reversed with the AO and PNA becoming positive and negative, respectively. This linked AO

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

    CERN Document Server

    Knurenko, Stanislav

    2014-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1993-11-19

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

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

    Institute of Scientific and Technical Information of China (English)

    JIA Liwei; LI Weijing; CHEN Deliang; AN Xiaocun

    2006-01-01

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

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

    Institute of Scientific and Technical Information of China (English)

    YAN Huasheng; WAN Yunxia; CHENG Jiangang

    2005-01-01

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

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

    Science.gov (United States)

    Washington, Warren M.; Meehl, Gerald A.

    1989-06-01

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

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

    CERN Document Server

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

    2012-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

    1992-02-01

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

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

    Science.gov (United States)

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

    2010-09-01

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

  20. 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.

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

    Institute of Scientific and Technical Information of China (English)

    HONG Jieli; LIU Yimin

    2012-01-01

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

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

    Science.gov (United States)

    Izakov, M. N.

    2016-09-01

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

  3. 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.

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

    Science.gov (United States)

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

    2012-01-01

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

  5. 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)

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

    Science.gov (United States)

    Paschalidou, A K; Kassomenos, P A

    2016-01-01

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

  7. Projections of Southern Hemisphere atmospheric circulation interannual variability

    Science.gov (United States)

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

    2017-02-01

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

  8. 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 ...

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

    Institute of Scientific and Technical Information of China (English)

    ZONG Haifeng; ZHANG Qingyun

    2011-01-01

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

  10. 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...

  11. Natural modes of variability in the A1B scenario: Atmospheric forcing anomalies associated with NAO

    Science.gov (United States)

    Markovic, Michaela; Klein, Birgit; Mikolajewicz, Uwe; Mathis, Moritz

    2015-04-01

    A global fully coupled climate scenario run based on the Max Plank Institute Ocean Model (MPIOM) is used to disentangle the effect of internal climatic modes, e.g. the North Atlantic Oscillation (NAO), from climate change signals in the North Sea. By placing one grid pole on Central Europe, enhanced spatial resolution for the European seas was obtained (up to 4 km in the German Bight). This allows a regional scale resolution within the global model, without the inherent problems of prescribed lateral boundary conditions. Furthermore, it provides sufficient resolution to study the leading modes of variability in the circulation and climate of the North Sea, as well as their connection to exchange processes with adjacent parts of the North Atlantic. The North Atlantic Oscillation (NAO) is the dominant mode of winter climate variability affecting the North Sea with amplitudes comparable to the climate change signal. Here we investigate in the fully coupled scenario run how the NAO impact the surface heat fluxes, which comprises the sum of the four components: net surface solar radiation, net surface thermal radiation, sensible heat flux, and latent heat flux. In particular, we analyzed NAO+ and NAO- composites. The results show that the largest contributions to the net radiation balance are attributed to the sensible heat flux and the latent heat fluxes. The highest anomalies in both variables are found over the Norwegian Trench which are related to mixed layer dynamics, circulation changes, and changing in the mean wind field. This modification in the mixed layer dynamics, and mean wind fields will be further investigated.

  12. Can anomalies of fetal brain circulation be useful in the management of growth restricted fetuses?

    Science.gov (United States)

    Hernandez-Andrade, Edgar; Serralde, Jesus Andres Benavides; Cruz-Martinez, Rogelio

    2012-02-01

    Assessment of the fetal cerebral circulation provides important information on the hemodynamic changes associated with chronic hypoxia and intrauterine growth restriction. Despite the incorporation of new US parameters, the landmark for the fetal brain hemodynamic evaluation is still the middle cerebral artery. However, new vascular territories, such as the anterior and posterior cerebral arteries, might provide additional information on the onset of the brain sparing effect. The fractional moving blood volume estimation and three-dimensional power Doppler ultrasound indices are new techniques that seem to be promising in identifying cases at earlier stages of vascular deterioration; still, they are not available for clinical application and more information is needed on the reproducibility and advantages of three-dimensional power Doppler ultrasound blood flow indices. In the past, the brain sparing effect was considered as a protective mechanism; however, recent information challenges this concept. There is growing evidence of an association between brain sparing effect and increased risk of abnormal neurodevelopment after birth. Even in mild late-onset intrauterine growth restriction affected fetuses with normal umbilical artery blood flow, increased cerebral blood perfusion can be associated with a substantial risk of abnormal neuroadaptation and neurodevelopment during childhood.

  13. 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

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

    Science.gov (United States)

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

    2016-08-01

    The onset of modern central Asian atmospheric circulation is traditionally linked to the interplay of surface uplift of the Mongolian and Tibetan-Himalayan orogens, retreat of the Paratethys sea from central Asia and Cenozoic global cooling. Although the role of these players has not yet been unravelled, the vast dust deposits of central China support the presence of arid conditions and modern atmospheric pathways for the last 25 million years (Myr). Here, we present provenance data from older (42-33 Myr) dust deposits, at a time when the Tibetan Plateau was less developed, the Paratethys sea still present in central Asia and atmospheric pCO2 much higher. Our results show that dust sources and near-surface atmospheric circulation have changed little since at least 42 Myr. Our findings indicate that the locus of central Asian high pressures and concurrent aridity is a resilient feature only modulated by mountain building, global cooling and sea retreat.

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

    Institute of Scientific and Technical Information of China (English)

    俞永强; 张学洪; 郭裕福

    2004-01-01

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

  16. 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...

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

    Science.gov (United States)

    Lee, Jae Nyung

    2008-10-01

    variability over the Asian monsoon region. The corresponding EOF in ModelE has a qualitatively similar structure but with less variability in the Asian monsoon region which is displaced eastward of its observed position. In both the NCEP/NCAR reanalysis and the GISS GCM, the negative anomalies associated with the NAM in the Euro-Atlantic and Aleutian island regions are enhanced in the solar minimum conditions, though the results are not statistically significant. The difference of the downward propagation of NAM between solar maximum and solar minimum is shown with the NCEP/NCAR reanalysis. For the winter NAM, a much greater fraction of stratospheric circulation perturbations penetrate to the surface in solar maximum conditions than in minimum conditions. This difference is more striking when the zonal wind direction in the tropics is from the west: when equatorial 50 hPa winds are from the west, no stratospheric signals reach the surface under solar minimum conditions, while over 50 percent reach the surface under solar maximum conditions. This work also studies the response of the tropical circulation to the solar forcing in combination with different atmospheric compositions and with different ocean modules. Four model experiments have been designed to investigate the role of solar forcing in the tropical circulation: one with the present day (PD) greenhouse gases and aerosol conditions, one with the preindustrial (PI) conditions, one with the doubled minimum solar forcing, and finally one with the hybrid-isopycnic ocean model (HYCOM). The response patterns in the tropical humidity and in the vertical motion due to solar forcing are season dependent and spatially heterogeneous. The tropical humidity response from the model experiments are compared with the corresponding differences obtained from the NCEP/NCAR reanalysis with all years and with non-ENSO years. Both the model and the reanalysis consistently show that the specific humidity is significantly greater in the

  18. 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

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

    Science.gov (United States)

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

    2017-01-01

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

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

    Science.gov (United States)

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

    2016-04-01

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

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

    Science.gov (United States)

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

    2012-12-01

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

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

    Science.gov (United States)

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

    2016-11-01

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

  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.;

    2016-01-01

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

  4. INTERANNUAL VARIATIONS OF ATMOSPHERIC HEAT SOURCES AND MOISTURE SINKS OVER THE EQUATORIAL PACIFIC AND THEIR RELATIONS TO THE SST ANOMALIES

    Institute of Scientific and Technical Information of China (English)

    蓝光东; 温之平; 贺海晏

    2004-01-01

    The interannual variations of atmospheric heat sources and moisture sinks over the Equatorial Pacific and their relations with the SST anomalies are studied using ECMWF reanalysis data from 1979 to 1993. It is found by singular value decomposition (SVD) analysis that the region in the tropical Pacific with high positive correlation between the vertically integrated heat source anomaly and the SST anomaly, and between the vertically integrated moisture sink anomaly and the SST anomaly, is mainly located in a long and narrow belt to the east of 170 (E between 5 (S and 5 (N. The analysis of the vertical structure of atmospheric heat sources and moisture sinks shows that the interannual variations of Q1, Q2 and SST in the equatorial central and eastern Pacific are strongly and positively correlated in the whole troposphere except the bottom (962.5 hPa) and the top (85 hPa) layers. However, in the western Pacific, the interannual variations of Q1 below 850 hPa is negatively related to the SST. The correlation coefficient at the level 962.5 hPa reaches even -0.59. In other layers the positive correlation between the interannual variations of Q1, Q2 and the SST are weak in the western Pacific.

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

    Science.gov (United States)

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

    1995-01-01

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

  6. 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...

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2001-08-01

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

  8. Impact of oceanic circulation changes on atmospheric δ13CO2

    Science.gov (United States)

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

    2015-12-01

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

  9. 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.

  10. 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.

  11. 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...

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

    Directory of Open Access Journals (Sweden)

    E. I. Nikolopoulos

    2014-12-01

    Full Text Available The work examines the seasonality and large-scale atmospheric circulation patterns of debris flows in the Trentino-Alto Adige region (Eastern Italian Alps. Analysis is based on classification algorithms applied on a uniquely dense archive of debris flows and hourly rain gauge precipitation series covering the period 2000–2009. Results highlight the seasonal and synoptic forcing patterns linked to debris flows in the study area. Summer and fall season account for 92% of the debris flows in the record, while atmospheric circulation characterized by Zonal West, Mixed and Meridional South, Southeast patterns account for 80%. Both seasonal and circulation patterns exhibit geographical preference. In the case of seasonality, there is a strong north–south separation of summer–fall dominance while spatial distribution of dominant circulation patterns exhibits clustering, with both Zonal West and Mixed prevailing in the northwest and central east part of the region, while the southern part relates to Meridional South, Southeast pattern. Seasonal and synoptic pattern dependence is pronounced also on the debris flow triggering rainfall properties. Examination of rainfall intensity–duration thresholds derived for different data classes (according to season and synoptic pattern revealed a distinct variability in estimated thresholds. These findings imply a certain control on debris-flow events and can therefore be used to improve existing alert systems.

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

    OpenAIRE

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

    2005-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Eric T. DeWeaver

    2010-01-19

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

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

    Science.gov (United States)

    Sugimoto, Norihiko; AFES project Team

    2016-10-01

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

  16. 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.

  17. 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.

  18. 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...

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2009-02-15

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

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

    Institute of Scientific and Technical Information of China (English)

    李江龙; 张学洪; 俞永强; 戴福山

    2004-01-01

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

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

    Science.gov (United States)

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

    2016-09-01

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

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

    Science.gov (United States)

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

    2015-01-01

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

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

    Science.gov (United States)

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

    1988-01-01

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

  4. 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.

  5. 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...

  6. 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

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

    Directory of Open Access Journals (Sweden)

    F. S. R. Pausata

    2011-10-01

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

  8. Principal component analysis of a river basin discharge and precipitation anomaly fields associated with the global circulation

    Science.gov (United States)

    Pandžić, K.; Trninić, D.

    1992-03-01

    The relation between mesoscale (the Kupa river catchment area, Yugoslavia) discharge and precipitation field anomalies and macroscale (European-Northern Atlantic Region) surface pressure anomalies is considered. For this purpose the principal component analysis (PCA) technique has been applied. Mesoscale monthly discharge values for 25 stream flow measurement stations, precipitation and the Palmer 'drought index' data for 18 weather stations as well as the macroscale surface pressure for 12 × 19 grid points have been used. All refer to the period 1961-1980. Two principal components (PCs) are the most significant for each mesoscale field, which describe more than 85% of total field variance. In addition to a significant correlation indicated between mesoscale discharge and precipitation anomaly and the Palmer 'drought index' PCs, five space anomaly patterns were established for each field. A pattern of the macroscale surface pressure anomaly field corresponds to each of these patterns. Thus, an interpretation of the discharge anomaly field in the Kupa river basin in terms of macrocirculation is achieved.

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

    Science.gov (United States)

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

    2016-11-01

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

  10. 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

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

    Science.gov (United States)

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

    2016-04-01

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

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

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

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

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

    Directory of Open Access Journals (Sweden)

    H. Evangelista

    2015-08-01

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

  14. The estimation of 550 km x 550 km mean gravity anomalies. [from free atmosphere gravimetry data

    Science.gov (United States)

    Williamson, M. R.; Gaposchkin, E. M.

    1975-01-01

    The calculation of 550 km X 550 km mean gravity anomalies from 1 degree X 1 degree mean free-air gravimetry data is discussed. The block estimate procedure developed by Kaula was used, and estimates for 1452 of the 1654 blocks were obtained.

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

    Science.gov (United States)

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

    1992-01-01

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

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

    Directory of Open Access Journals (Sweden)

    Daniel S. Schaffer

    2000-01-01

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

  17. 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.

  18. 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...

  19. 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...

  20. 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

  1. 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...

  2. Atmospheric forcing of sea ice anomalies in the Ross Sea Polynya region

    Science.gov (United States)

    Dale, Ethan; McDonald, Adrian; Rack, Wolfgang

    2016-04-01

    Despite warming trends in global temperatures, sea ice extent in the southern hemisphere has shown an increasing trend over recent decades. Wind-driven sea ice export from coastal polynyas is an important source of sea ice production. Areas of major polynyas in the Ross Sea, the region with largest increase in sea ice extent, have been suggested to produce the vast amount of the sea ice in the region. We investigate the impacts of strong wind events on polynyas and the subsequent sea ice production. We utilize Bootstrap sea ice concentration (SIC) measurements derived from satellite based, Special Sensor Microwave Imager (SSM/I) brightness temperature images. These are compared with surface wind measurements made by automatic weather stations of the University of Wisconsin-Madison Antarctic Meteorology Program. Our analysis focusses on the winter period defined as 1st April to 1st November in this study. Wind data was used to classify each day into characteristic regimes based on the change of wind speed. For each regime, a composite of SIC anomaly was formed for the Ross Sea region. We found that persistent weak winds near the edge of the Ross Ice Shelf are generally associated with positive SIC anomalies in the Ross Sea polynya area (RSP). Conversely we found negative SIC anomalies in this area during persistent strong winds. By analyzing sea ice motion vectors derived from SSM/I brightness temperatures, we find significant sea ice motion anomalies throughout the Ross Sea during strong wind events. These anomalies persist for several days after the strong wing event. Strong, negative correlations are found between SIC within the RSP and wind speed indicating that strong winds cause significant advection of sea ice in the RSP. This rapid decrease in SIC is followed by a more gradual recovery in SIC. This increase occurs on a time scale greater than the average persistence of strong wind events and the resulting Sea ice motion anomalies, highlighting the production

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

    Energy Technology Data Exchange (ETDEWEB)

    Costigan, K.R.

    1998-11-01

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

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

    Science.gov (United States)

    Fattahi, E.; Sedaghatkerdar, A.

    2009-04-01

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

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

    Science.gov (United States)

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

    2016-09-01

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

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

    Institute of Scientific and Technical Information of China (English)

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

    2011-01-01

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

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

    Science.gov (United States)

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

    2013-08-01

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

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

    Science.gov (United States)

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

    2012-04-01

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

  9. 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

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

    Science.gov (United States)

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

    2011-12-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2012-10-15

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

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

    Science.gov (United States)

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

    2017-03-01

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

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

    Science.gov (United States)

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

    2016-06-01

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

  14. 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.

  15. 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.

  16. 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.

  17. Atmospheric forcing of sea ice anomalies in the Ross Sea polynya region

    Science.gov (United States)

    Dale, Ethan R.; McDonald, Adrian J.; Coggins, Jack H. J.; Rack, Wolfgang

    2017-01-01

    We investigate the impacts of strong wind events on the sea ice concentration within the Ross Sea polynya (RSP), which may have consequences on sea ice formation. Bootstrap sea ice concentration (SIC) measurements derived from satellite SSM/I brightness temperatures are correlated with surface winds and temperatures from Ross Ice Shelf automatic weather stations (AWSs) and weather models (ERA-Interim). Daily data in the austral winter period were used to classify characteristic weather regimes based on the percentiles of wind speed. For each regime a composite of a SIC anomaly was formed for the entire Ross Sea region and we found that persistent weak winds near the edge of the Ross Ice Shelf are generally associated with positive SIC anomalies in the Ross Sea polynya and vice versa. By analyzing sea ice motion vectors derived from the SSM/I brightness temperatures we find significant sea ice motion anomalies throughout the Ross Sea during strong wind events, which persist for several days after a strong wind event has ended. Strong, negative correlations are found between SIC and AWS wind speed within the RSP indicating that strong winds cause significant advection of sea ice in the region. We were able to partially recreate these correlations using colocated, modeled ERA-Interim wind speeds. However, large AWS and model differences are observed in the vicinity of Ross Island, where ERA-Interim underestimates wind speeds by a factor of 1.7 resulting in a significant misrepresentation of RSP processes in this area based on model data. Thus, the cross-correlation functions produced by compositing based on ERA-Interim wind speeds differed significantly from those produced with AWS wind speeds. In general the rapid decrease in SIC during a strong wind event is followed by a more gradual recovery in SIC. The SIC recovery continues over a time period greater than the average persistence of strong wind events and sea ice motion anomalies. This suggests that sea ice

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

    Science.gov (United States)

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

    1993-01-01

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

  19. 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.

  20. Interannual variability of the Asian subtropical westerly jet in boreal summer and associated with circulation and SST anomalies

    Science.gov (United States)

    Du, Yin; Li, Tim; Xie, Zhiqing; Zhu, Zhiwei

    2016-04-01

    The interannual variability of the Asian Subtropical Westerly Jet (ASWJ) in boreal summer is investigated through the diagnosis of 54-year (1960-2013) NCEP/NCAR reanalysis data. The main characteristics of two leading empirical orthogonal function patterns of 200 hPa zonal wind anomalies are the meridional displacement and southwest-northeast tilting of ASWJ. The first leading mode has significant periods of 4.9 years, whereas the second mode has significant periods of 3.6 and 7.7 years, respectively. The two modes exhibit an equivalent barotropic structure, and are associated with a distinctive north-south and east-west dipole rainfall pattern in China, respectively. The positive phase of the first leading mode appears during El Nino developing phase, whereas the positive phase of the second mode occurs during La Nina decaying phase. A mechanism is put forth based on observational analysis and AGCM sensitivity experiments. The positive phase of the first mode is primarily driven by the combined effect of a cold SST anomaly (SSTA) in mid-latitude North Pacific and a warm SSTA in tropical Indian Ocean and Pacific. In response to the SSTA forcing, a zonally oriented north-south tropospheric temperature dipole is induced. While the tropospheric warming in the tropics arises from El Nino like heating, the tropospheric cooling in the mid-latitudes arises possibly from the local SSTA forcing. For the positive phase of the second mode, the upper-tropospheric anticyclonic vorticity anomaly in the east pole arises from local SSTA forcing in North Pacific, whereas the cyclonic anomaly in the west pole results from southeastward Rossby wave energy emanation from North Atlantic to East Asia.

  1. Direct communication between the left circumflex and the right coronary arteries: a very rare coronary anomaly circulation.

    Science.gov (United States)

    Oliveira, Marcos Danillo Peixoto; Cavalcanti, Rafael R César; Kajita, Alexandre H; Miranda, Thais; Kajita, Luiz J; Horta, Pedro E; Ribeiro, Expedito E; Lemos, Pedro Alves

    2016-02-01

    Coronary artery anomalies (CAA) are congenital changes in their origin, course, and/or structure. Intercoronary communication (ICC) is a very rare subset with uni- or bidirectional blood flow between two or more coronary arteries. We present the case of a 58-year-old man with an acute coronary syndrome whose coronary angiography incidentally showed a surprising and very rare communication between the right coronary and left circumflex arteries.

  2. 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.

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

    OpenAIRE

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

    2005-01-01

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

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

    CERN Document Server

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

    2004-01-01

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

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

    Science.gov (United States)

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

    1995-01-01

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

  6. 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.

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

    Science.gov (United States)

    Böhme, M.

    2004-05-01

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

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

    Science.gov (United States)

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

    2016-10-01

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

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

    OpenAIRE

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

    2009-01-01

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

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

    Science.gov (United States)

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

    2015-12-01

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

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

    Directory of Open Access Journals (Sweden)

    B. Croft

    2005-01-01

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

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

    Science.gov (United States)

    Heng, Kevin

    2011-09-01

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

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

    Science.gov (United States)

    Berg, Peter; Döscher, Ralf; Koenigk, Torben

    2016-06-01

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

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

    Science.gov (United States)

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

    2007-07-01

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

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

    Institute of Scientific and Technical Information of China (English)

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

    2007-01-01

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

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

    Science.gov (United States)

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

    2016-08-01

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

  17. 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.

  18. Heatwaves in Europe: areas of homogeneous variability and links with the regional to large-scale atmospheric and SSTs anomalies

    Energy Technology Data Exchange (ETDEWEB)

    Carril, Andrea F.; Gualdi, Silvio; Cherchi, Annalisa; Navarra, Antonio [Istituto Nazionale di Geofisica e Vulcanologia, INGV, Centro Euro-Mediterraneo per i Cambiamenti Climatici, CMCC, Bologna (Italy)

    2008-01-15

    This work presents a methodology to study the interannual variability associated with summertime months in which extremely hot temperatures are frequent. Daily time series of maximum and minimum temperature fields (T{sub max} and T{sub min}, respectively) are used to define indexes of extreme months based on the number of days crossing thresholds. An empirical orthogonal function (EOF) analysis is applied to the monthly indexes. EOF loadings give information about the geographical areas where the number of days per month with extreme temperatures has the largest variability. Correlations between the EOF principal components and the time series of other fields allow plotting maps highlighting the anomalies in the large scale circulation and in the SSTs that are associated with the occurrence of extreme events. The methodology is used to construct the ''climatology'' of the extremely hot summertime months over Europe. In terms of both interannual and intraseasonal variability, there are three regions in which the frequency of the extremely hot days per month homogeneously varies: north-west Europe, Euro-Mediterranean and Eurasia region. Although extremes over those regions occur during the whole summer (June to August), the anomalous climatic conditions associated with frequent heatwaves present some intraseasonal variability. Extreme climate events over the north-west Europe and Eurasia are typically related to the occurrence of blocking situations. The intraseasonal variability of those patterns is related to the amplitude of the blocking, the relative location of the action centre and the wavetrain of anomalies downstream or upstream of the blocking. During June and July, blocking situations which give extremely hot climate conditions over north-west Europe are also associated with cold conditions over the eastern Mediterranean sector. The Euro-Mediterranean region is a transition area in which extratropical and tropical systems compete

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2010-12-15

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

  20. 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.

  1. STATISTICS OF OCCURRENCE OF PRE-SEISMIC ANOMALIES IN GEOACOUSTIC EMISSION AND IN ATMOSPHERIC FIELD

    Directory of Open Access Journals (Sweden)

    M. A. Mishchenko

    2016-11-01

    Full Text Available Statistics of occurrence of anomalous disturbances in high-frequency geoacoutic emis-sion of the near surface sedimentary rocks and in atmospheric electric field by the ground surface before earthquakes is presented. Long-term continuous series of measure-ments of geoacoustic emission for the period of 2003-2012 at «Mikizha» site and the data of measurements of atmospheric electric field obtained for the summer-autumn periods of 2006-2008 at «Mikizha» site and for 2009-2012 at «Karymshina» site were used in the analysis. Anomalous disturbances of the emission and of the field were compared with the earthquake catalogue of Kamchatka Branch of Geophysical Service RAS.

  2. 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.

  3. 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

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

    Science.gov (United States)

    Sniderman, K.; Porch, N.

    2009-12-01

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

  5. 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.)

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

    Science.gov (United States)

    Sekiguchi, Miho; Nakajima, Teruyuki

    2009-03-01

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

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

    Science.gov (United States)

    Persad, G.; Ming, Y.

    2009-12-01

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

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

    Science.gov (United States)

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

    2016-10-01

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

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

    CERN Document Server

    Panja, Debabrata

    2007-01-01

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

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

    Science.gov (United States)

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

    2015-02-01

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

  11. 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.

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

    Science.gov (United States)

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

    2012-12-01

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

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

    Directory of Open Access Journals (Sweden)

    P. S. Bhattacharjee

    2009-10-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2009-07-01

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

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

    Science.gov (United States)

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

    1995-05-01

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

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

    Science.gov (United States)

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

    2016-10-01

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

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

    Science.gov (United States)

    Kim, Jin-Ah; Byun, Hi-Ryong

    2016-10-01

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

  18. 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.)

  19. 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.

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

    Science.gov (United States)

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

    2009-04-01

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

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

    Science.gov (United States)

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

    2012-12-01

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

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

    CERN Document Server

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

    2014-01-01

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

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

    Directory of Open Access Journals (Sweden)

    Z. Zhang

    2015-08-01

    Full Text Available Using the daily records derived from the synoptic weather stations and the NCEP/NCAR and ERA-Interim reanalysis data, the variability of the winter hazy pollutions (indicated by the mean visibility and number of hazy days in Beijing-Tianjin-Hebei (BTH region during the period 1981 to 2015 and its relationship to the atmospheric circulations in middle-high latitude were analyzed in this study. The winter hazy pollution in BTH had distinct inter-annual and inter-decadal variabilities without a significant long-term trend. According to the spatial distribution of correlation coefficients, six atmospheric circulation indices (I1 to I6 were defined from the key areas in sea level pressure (SLP, zonal and meridional winds at 850 hPa (U850, V850, geopotential height field at 500 hPa (H500, zonal wind at 200 hPa (U200, and air temperature at 200 hPa (T200, respectively. All of the six indices have significant and stable correlations with the winter visibility and number of hazy days in BTH. Both the visibility and number of hazy days can be estimated well by using the six indices and fitting and the cross-validation with leave-N-out method, respectively. The high level of the prediction statistics and the reasonable mechanism suggested that the winter hazy pollutions in BTH can be forecasted or estimated credibly based on the optimized atmospheric circulation indices. However, we also noted that the statistic estimation models would be largely influenced by the artificial control of a pollutant discharge. Thus it is helpful for government decision-making departments to take actions in advance in dealing with probably severe hazy pollutions in BTH indicated by the atmospheric circulation conditions.

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

    Science.gov (United States)

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

    2016-01-01

    Using the daily records derived from the synoptic weather stations and the NCEP/NCAR and ERA-Interim reanalysis data, the variability of the winter haze pollution (indicated by the mean visibility and number of hazy days) in the Beijing-Tianjin-Hebei (BTH) region during the period 1981 to 2015 and its relationship with the atmospheric circulations at middle-high latitude were analyzed in this study. The winter haze pollution in BTH had distinct inter-annual and inter-decadal variabilities without a significant long-term trend. According to the spatial distribution of correlation coefficients, six atmospheric circulation indices (I1 to I6) were defined from the key areas in sea level pressure (SLP), zonal and meridional winds at 850 hPa (U850, V850), geopotential height field at 500 hPa (H500), zonal wind at 200 hPa (U200), and air temperature at 200 hPa (T200), respectively. All of the six indices have significant and stable correlations with the winter visibility and number of hazy days in BTH. In the raw (unfiltered) correlations, the correlation coefficients between the six indices and the winter visibility (number of hazy days) varied from 0.57 (0.47) to 0.76 (0.6) with an average of 0.65 (0.54); in the high-frequency ( pollution in BTH winter, and vice versa. The high level of the prediction statistics and the reasonable mechanism suggested that the winter haze pollution in BTH can be forecasted or estimated credibly based on the optimized atmospheric circulation indices. Thus it is helpful for government decision-making departments to take action in advance in dealing with probably severe haze pollution in BTH indicated by the atmospheric circulation conditions.

  5. Investigating atmospheric transport processes using cosmogenic 35S and oxygen isotopic anomaly (Δ17O) in sulfate

    Science.gov (United States)

    Hill-Falkenthal, J. C.; Pandey, A.; Coupal, E.; Kim, S. D.; Dominguez, G.; Thiemens, M. H.

    2010-12-01

    Sulfate aerosols have been recognized to possess hazardous impact on both climate and human health. Improved understanding of the SO2 residence time and sulfate aerosol transport is needed for assessing its influences on climate. Cosmogenically produced 35S (half-life~87 days)1 measurements have been used to understand the atmospheric transport process, boundary layer dynamics and its effect on the tropospheric SO2 oxidation rate constant. Our method involves determining 35S in gaseous SO2 and aerosol sulfate samples collected twice a week at Scripps Institute of Oceanography Pier (La Jolla, CA) for a year along with the determination of oxygen isotopes in both coarse and fine particle samples. The oxygen isotopes measurement in sulfate and 35S measurements were done by isotope ratio mass spectrometry and low-noise liquid scintillation spectroscopy2, respectively. The data show that 35S activity is significantly different for coarse and fine particles, with the latter possessing higher activity as it is mainly produced from the gas phase oxidation of SO2 at higher altitude. The fluctuation in 35S activity in fine particles indicates mixing of air masses from higher altitude. The coarse particles show nearly constant 35S activity which is either due to the constant uptake rate of SO2 by sea salt aerosol or the coagulation of fine particles together. The normalized activity 35S/S is about 5 times higher in both coarse and fine particles during Santa Ana wind event. Santa Ana wind is characterized by low humidity (<20%) and relatively high temperature and may have an impact on SO2 oxidation. We are investigating the sulfate oxygen isotope signature and the correlation between oxygen anomaly and 35S activity in sulfate. 1. Lal D., P. K. Malhotra, and B. Peters, On the production of radioisotopes in the atmosphere by cosmic radiation and their application in meteorology, J. Atmos. AndTerrest. Phys. 12, 306, 1958 2. Brother, L.A., G. Dominguez, A. Abramian, A. Corbin

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

    Science.gov (United States)

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

    2016-08-01

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

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

    NARCIS (Netherlands)

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

    2010-01-01

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

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

    Science.gov (United States)

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

    2015-02-01

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

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

    Science.gov (United States)

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

    2016-01-01

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

  10. 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.

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

    Science.gov (United States)

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

    2004-11-01

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

  12. 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.

  13. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2008-07-15

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2011-03-15

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2005-12-01

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

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

    Science.gov (United States)

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

    2017-01-01

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

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

    CERN Document Server

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

    2008-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-03-10

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

  20. 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

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

    Science.gov (United States)

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

    2012-04-01

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

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

    Science.gov (United States)

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

    2015-12-01

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

  3. 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.

  4. 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...

  5. 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

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

    Directory of Open Access Journals (Sweden)

    G. Walker

    2009-10-01

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

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

    NARCIS (Netherlands)

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

    2007-01-01

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

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

    Science.gov (United States)

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

    2017-02-01

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

  9. Relationships between 700 hPa height anomalies and 1 April snowpack accumulations in the western USA

    Science.gov (United States)

    McCabe, G.J.; Legates, D.R.

    1995-01-01

    Relationships between atmospheric circulation and the temporal and spatial distribution of snowpack accumulations in the western USA are examined. In general, above-average snowpack accumulations are associated with negative 700 hPa height anomalies over the eastern North Pacific Ocean and the western USA. These anomalies are indicative of anomalous cyclonic circulation, which produces an anomalous westerly flow of moist air from the eastern North Pacific Ocean into the western USA and increases winter precipitation and snowpack accumulations. Below-average snowpack accumulations at most of the snowcourse stations are associated with positive 700 hPa anomalies over the western USA. -from Authors

  10. Rotational atmospheric circulation during North Atlantic-European winter: the influence of ENSO

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Serrano, J. [UCM, Departamento de Geofisica y Meteorologia, Madrid (Spain); Institut Catala de Ciencies del Clima (IC3), Barcelona (Spain); Rodriguez-Fonseca, B.; Zurita-Gotor, P.; Camara, A. de la [UCM, Departamento de Geofisica y Meteorologia, Madrid (Spain); Blade, I. [UB, Departament d' Astronomia i Meteorologia, Barcelona (Spain)

    2011-11-15

    The dominant variability modes of the North Atlantic-European rotational flow are examined by applying a principal component analysis (PCA/EOF) to the 200 hPa streamfunction mid-winter anomalies (Jan-Feb monthly means). The results reveal that, when this norm is used, the leading mode (EOF1) does not correspond to the traditional North Atlantic Oscillation (NAO, which appears in our analysis as the second leading mode, EOF2) but is the local manifestation of the leading hemispheric streamfunction EOF. The regression of this regional mode onto the global SST field exhibits a clear El Nino signature, with no signal over the Atlantic, while the associated upper height anomalies resemble the Tropical/Northern Hemisphere (TNH) pattern. East of North America, this TNH-like wavetrain produces a meridional dipole-like pattern at lower levels. Although in some ways this pattern resembles the NAO (EOF2), the dynamics of these two modes are very different in that only EOF2 is associated with a latitudinal shift of the North Atlantic stormtrack. Thus, the choice of the streamfunction norm in the EOF analysis allows the separation of two different phenomena that can produce similar dipolar surface pressure anomalies over the North Atlantic but that have different impact on European climate. These two modes also differ on their contribution to variability at lower levels: while NAO-EOF2 is mostly confined to the North Atlantic, TNH-EOF1 has a more annular, global character. At upper levels NAO-EOF2 also produces a global pattern but with no annular structure, reminiscent of the ''circumglobal'' teleconnection. (orig.)

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2005-07-01

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

  12. 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.

  13. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2004-12-01

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

  15. 天气尺度瞬变扰动的物理分解原理%Physical decomposition principle of regional-scale atmospheric transient anomaly

    Institute of Scientific and Technical Information of China (English)

    钱维宏

    2012-01-01

    大气变量可以在时空域内物理分解成四个部分.前两个是纬圈-时间平均的对称部分和时间平均的非对称部分,分别由太阳辐射和海陆分布热力调节的季节变化引起,并形成规则的逐日气候.第三部分是由年际和季节内的热带海洋或极地热力强迫引起的纬圈平均瞬变对称扰动,可形成大气变量的行星尺度指数循环.第四部分是一些复杂的天气尺度瞬变非对称扰动.大气变量中的逐日天气尺度瞬变扰动,可以用于指示区域持续性的干旱、暴雨、低温和热浪等极端天气事件.天气尺度瞬变扰动天气图能在极端天气事件的预报中发挥应有的作用.%In a mixed space-time domain, atmospheric variables can be decomposed into the zonal time-average climate symmetric part, the time-average climate asymmetric part, the zonal-average transient symmetric anomaly, and the transient asymmetric anomaly. The first two parts are forced by the seasonal solar radiation and land-sea distribution and linked to regular daily climate. The third part is caused from intra-seasonal to inter-annual tropical or polar heating variations and shows like the planetary-scale index cycle. The last part is complex as some atmospheric transient waves or regional-scale anomalies. The daily transient anomalies of atmospheric variables can be used to indicate some extreme weather events such as the regional persistent drought, heavy rainfall, lower temperature and hot days. We suggest that the weather map of transient anomalies could be applied in forecasts of extreme weather events.

  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. 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.

  18. 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.

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

    Directory of Open Access Journals (Sweden)

    M. J. Winnick

    2012-10-01

    Full Text Available Understanding how the hydrologic cycle has responded to warmer global temperatures in the past is especially important today as concentrations of CO2 in the atmosphere continue to increase due to human activities. The Pliocene offers an ideal window into a climate system that has equilibrated with current atmospheric pCO2. During the Pliocene the Western United States was wetter than modern, an observation at odds with our current understanding of future warming scenarios, which involve the expansion and poleward migration of the subtropical dry zone. Here we compare Pliocene oxygen isotope profiles of pedogenic carbonates across the Western US to modern isotopic anomalies in precipitation between phases of the El Niño Southern Oscillation (ENSO. We find that when accounting for seasonality of carbonate formation, isotopic changes through the late Pliocene match modern precipitation isotopic anomalies in El Niño years. Furthermore, isotopic shifts through the late Pliocene mirror changes through the early Pleistocene, which likely represents the southward migration of the westerly storm track caused by growth of the Laurentide Ice Sheet. We propose that the westerly storm track migrated northward through the late Pliocene with the development of the modern Cold Tongue in the East Equatorial Pacific, then returned southward with widespread glaciation in the Northern Hemisphere – a scenario supported by terrestrial climate proxies across the US. Together these data support the proposed existence of background El Niño-like conditions in Western North America during the warm Pliocene. If the Earth behaves similarly with future warming, this observation has important implications with regard to the amount and distribution of precipitation in Western North America.

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

    Directory of Open Access Journals (Sweden)

    M. J. Winnick

    2013-04-01

    Full Text Available Understanding how the hydrologic cycle has responded to warmer global temperatures in the past is especially important today as concentrations of CO2 in the atmosphere continue to increase due to human activities. The Pliocene offers an ideal window into a climate system that has equilibrated with current atmospheric pCO2. During the Pliocene the western United States was wetter than modern, an observation at odds with our current understanding of future warming scenarios, which involve the expansion and poleward migration of the subtropical dry zone. Here we compare Pliocene oxygen isotope profiles of pedogenic carbonates across the western US to modern isotopic anomalies in precipitation between phases of the El Niño–Southern Oscillation (ENSO. We find that when accounting for seasonality of carbonate formation, isotopic changes through the late Pliocene match modern precipitation isotopic anomalies in El Niño years. Furthermore, isotopic shifts through the late Pliocene mirror changes through the early Pleistocene, which likely represents the southward migration of the westerly storm track caused by growth of the Laurentide ice sheet. We propose that the westerly storm track migrated northward through the late Pliocene with the development of the modern cold tongue in the east equatorial Pacific, then returned southward with widespread glaciation in the Northern Hemisphere – a scenario supported by terrestrial climate proxies across the US. Together these data support the proposed existence of background El Niño-like conditions in western North America during the warm Pliocene. If the earth behaves similarly with future warming, this observation has important implications with regard to the amount and distribution of precipitation in western North America.

  1. On the feedback of the winter NAO-driven sea ice anomalies

    Science.gov (United States)

    García-Serrano, J.; Frankignoul, C.

    2016-09-01

    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 intra-seasonal differences: the December SIC influence is dominated by anomalies east of Greenland, with maximum amplitude in the Greenland Sea (GS); while the January SIC influence is dominated by anomalies west of Greenland, in the Davis Strait-Labrador Sea (DL) region. The lagged atmospheric anomalies are likewise different. A reduction of SIC over GS in December is followed in February by a negative NAO-like pattern near the surface and a hemispheric signature in the upper-troposphere, thus acting as a negative feedback. On the other hand, a reduction of SIC over DL in January is followed by an atmospheric anomaly over the North Atlantic that projects on the positive phase of the East Atlantic pattern. The dynamics associated with these atmospheric anomalies is described, indicating that transient-eddy activity is likely at work in settling the large-scale patterns. The role of concomitant North Atlantic sea surface temperature anomalies is discussed.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2009-08-15

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

  3. 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

  4. 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

  5. Atmospheric circulation changes and neoglacial conditions in the Southern Hemisphere mid-latitudes: insights from PMIP2 simulations at 6 kyr

    Energy Technology Data Exchange (ETDEWEB)

    Rojas, Maisa [University of Chile, Department of Geophysics, Santiago (Chile); Moreno, Patricio I. [University of Chile, Department of Ecology, Santiago (Chile)

    2011-07-15

    Glacial geologic studies in the Southern Hemisphere (SH) mid-latitudes (40-54 S) indicate renewed glacial activity in southern South America (Patagonia) and New Zealand's (NZ) South Island starting at {proportional_to}7 kyr, the so-called neoglaciation. Available data indicate that neoglacial advances in these regions occurred during a rising trend in atmospheric CO{sub 2} and CH{sub 4} concentrations, lower-than-present but increasing summer insolation and seasonality contrasts. In this paper we examine the climatological context in which neoglaciations occurred through analysis of the complete Paleoclimate Modelling Inter-comparison Project (PMIP2) database of simulations at 6 kyr for the SH. We observe that the amplitude of the annual insolation cycle in the SH did not change significantly at 6 kyr compared to the pre-industrial values, the largest difference occurring in autumn (MAM, negative anomalies) and spring (SON, positive anomalies). The simulated changes in temperatures over the SH respond to the insolation changes, with a 1-2 month delay over the oceans. This results in a reduced amplitude of the annual cycle of temperature and precipitation over most continental regions, except over Patagonia and NZ, that show a slight increase. In contrast, large-scale circulation features, such as the low and upper level winds and the subtropical anticyclones show an amplified annual cycle, as a direct response to the increased/decreased insolation during the transitional seasons SON/MAM. In the annual mean, there is a small but consistent equatorward shift of the latitude of maximum wind speed of 1-3 over the entire SH, which results in a small increase of wind speed over the South Pacific and Atlantic Oceans north of {proportional_to}50 S and a widespread decline south of 50 S. PMIP2 simulations for 6 kyr, indicate that in the annual mean, the SH mid-latitudes were colder, wetter and with stronger winds north of about 50 S. These conditions are consistent

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

    Science.gov (United States)

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

    2017-02-01

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

  7. 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.

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

    Science.gov (United States)

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

    2007-12-01

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

  9. The history and transitent nature of salinity anomalies in the Mediterranean Sea from advanced reanalysis

    Science.gov (United States)

    Pinardi, Nadia; Fratianni, Claudia; Lyubartsev, Vladyslav

    2015-04-01

    Long term, high resolution re-analyses of the Mediterranean Sea circulation and thermohaline structure are now available from the NextData and MyOcean projects. The first is a 60 years re-analysis (1953-2012) done with atmospheric AMIP forcing and the second is 25 years re-analysis (1987-2012) done with ECMWF atmospheric forcing re-analysis. Both concur to have a representation of the longest time series of salinity anomalies in the Mediterranean Sea, the highest space-time reconstruction ever done for the whole basin. The salinity anomalies of the Mediterranean Sea below seven hundred meters of the past 60 years are examined in comparison with the Eastern Mediterranean Transient, a phenomenon Dr. A.Hecht contributed to discover during POEM. Deep water salinity changes and Gibraltar Strait anomalies are also examined in the light of possible feedback mechanisms, as well as the structure and correlation of such salinity anomalies with atmospheric forcing.

  10. 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

  11. 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

  12. 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.

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

    Science.gov (United States)

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

    1977-01-01

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

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

    Science.gov (United States)

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

    2015-12-01

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

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

    Science.gov (United States)

    Fleming, Sean W.; Hood, Eran; Dalhke, Helen; O'Neel, Shad

    2016-01-01

    The northern portion of the Pacific coastal temperate rainforest (PCTR) is one of the least anthropogenically modified regions on earth and remains in many respects a frontier area to science. Rivers crossing the northern PCTR, which is also an international boundary region between British Columbia, Canada and Alaska, USA, deliver large freshwater and biogeochemical fluxes to the Gulf of Alaska and establish linkages between coastal and continental ecosystems. We evaluate interannual flow variability in three transboundary PCTR watersheds in response to El Niño-Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), Arctic Oscillation (AO), and North Pacific Gyre Oscillation (NPGO). Historical hydroclimatic datasets from both Canada and the USA are analyzed using an up-to-date methodological suite accommodating both seasonally transient and highly nonlinear teleconnections. We find that streamflow teleconnections occur over particular seasonal windows reflecting the intersection of specific atmospheric and terrestrial hydrologic processes. The strongest signal is a snowmelt-driven flow timing shift resulting from ENSO- and PDO-associated temperature anomalies. Autumn rainfall runoff is also modulated by these climate modes, and a glacier-mediated teleconnection contributes to a late-summer ENSO-flow association. Teleconnections between AO and freshet flows reflect corresponding temperature and precipitation anomalies. A coherent NPGO signal is not clearly evident in streamflow. Linear and monotonically nonlinear teleconnections were widely identified, with less evidence for the parabolic effects that can play an important role elsewhere. The streamflow teleconnections did not vary greatly between hydrometric stations, presumably reflecting broad similarities in watershed characteristics. These results establish a regional foundation for both transboundary water management and studies of long-term hydroclimatic and environmental change.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-03-10

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

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

    Science.gov (United States)

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

    2016-04-01

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

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

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

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

  19. 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.

  20. 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.

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

    CERN Document Server

    Heng, Kevin; Phillipps, Peter J

    2010-01-01

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

  2. 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

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

    Science.gov (United States)

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

    2001-01-01

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

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

    Science.gov (United States)

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

    2017-02-01

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

  5. 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

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

    Directory of Open Access Journals (Sweden)

    A. Chakraborty

    2004-04-01

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

    Key words. Atmospheric composition and structure (aerosols and particles – Meteorology and atmospheric dynamics (tropical meteorology; precipitation

  7. 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.

  8. Possible combined influences of absorbing aerosols and anomalous atmospheric circulation on summertime diurnal temperature range variation over the middle and lower reaches of the Yangtze River

    Science.gov (United States)

    Cai, Jiaxi; Guan, Zhaoyong; Ma, Fenhua

    2016-12-01

    Based on the temperature data from the China Meteorological Administration, NCEP-NCAR reanalysis data, and the TOMS Aerosol Index (AI), we analyze the variations in the summertime diurnal temperature range (DTR) and temperature maxima in the middle and lower reaches of the Yangtze River (MLRYR) in China. The possible relationships between the direct warming effect of the absorbing aerosol and temperature variations are further investigated, although with some uncertainties. It is found that the summertime DTR exhibits a decreasing trend over the most recent 50 years, along with a slight increasing tendency since the 1980s. The trend of the maximum temperature is in agreement with those of the DTR and the absorbing aerosols. To investigate the causes of the large anomalies in the temperature maxima, composite analyses of the circulation anomalies are performed. When anomalous AI and anomalous maximum temperature over the MLRYR have the same sign, an anomalous circulation with a quasi-barotropic structure occurs there. This anomalous circulation is modulated by the Rossby wave energy propagations from the regions northwest of the MLRYR and influences the northwestern Pacific subtropical high over the MLRYR. In combination with aerosols, the anomalous circulation may increase the maximum temperature in this region. Conversely, when the anomalous AI and anomalous maximum temperature in the MLRYR have opposite signs, the anomalous circulation is not equivalently barotropic, which possibly offsets the warming effect of aerosols on the maximum temperature changes in this region. These results are helpful for a better understanding of the DTR changes and the occurrences of temperature extremes in the MLRYR region during boreal summer.

  9. 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.

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

    Science.gov (United States)

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

    2012-04-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-02-10

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

  12. 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

  13. 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.

  14. 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.

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

    Science.gov (United States)

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

    2017-01-01

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

  16. 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

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

    Directory of Open Access Journals (Sweden)

    P. Räisänen

    2014-12-01

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

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

    Institute of Scientific and Technical Information of China (English)

    DONG Min; WU Tongwen; WANG Zaizhi; ZHANG Fang

    2010-01-01

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

  19. 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.

  20. 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.

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

    Directory of Open Access Journals (Sweden)

    T. Tharammal

    2012-04-01

    Full Text Available A series of experiments was conducted using a water isotope tracers-enabled atmospheric general circulation model (Community Atmosphere Model version 3.0, CAM3.0-Iso, by changing the individual boundary conditions (greenhouse gases, ice sheet albedo and topography, sea-surface temperature each at a time to Last Glacial Maximum (LGM values. In addition, a combined simulation with all the boundary conditions being set to LGM values was carried out. A pre-industrial (PI simulation with boundary conditions taken according to the PMIP2 (Paleoclimate Modelling Intercomparison Project protocol was performed as the control experiment. The experiments were designed in order to analyze the temporal and spatial variations of the oxygen isotopic composition of precipitation (δ18Oprecip in response to individual climate factors. The change in topography (due to the change in land-ice cover played a significant role in reducing the surface temperature and δ18Oprecip over North America. Exposed shelf areas and the ice sheet albedo reduced the Northern Hemisphere surface temperature and δ18Oprecip further. A global mean cooling of 4.1 °C was simulated with combined LGM boundary conditions compared to the control simulation, which was in agreement with previous experiments using the fully coupled Community Climate System Model (CCSM3. Large reductions in δ18Oprecip over the LGM ice sheets were highly correlated with the temperature decrease over them. The SST and ice sheet topography changes were found to be responsible for most of the changes in the climate and hence the δ18Oprecip distribution among the simulations.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2008-06-15

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

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

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

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

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

    Science.gov (United States)

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

    2016-11-01

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

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

    Science.gov (United States)

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

    2013-10-01

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

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

    Directory of Open Access Journals (Sweden)

    Daniel Holdaway

    2015-09-01

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

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

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

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

  8. 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.

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

    Institute of Scientific and Technical Information of China (English)

    Odd Helge OTTER(A)

    2008-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1963-11-15

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

  11. 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。

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1998-01-01

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

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

    Science.gov (United States)

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

    2017-01-01

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

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

    Directory of Open Access Journals (Sweden)

    E. V. Sokolikhina

    2006-01-01

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

  15. 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...

  16. Minnesota Bouguer Anomaly Grid

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — A 1.5 kilometer Bouguer anomaly grid for the state of Minnesota. Number of columns is 404 and number of rows is 463. The order of the data is from the lower left to...

  17. 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.

  18. 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...

  19. 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....

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

    Science.gov (United States)

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

    2017-01-01

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

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

    Science.gov (United States)

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

    2014-05-01

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

  2. The Linkages Between The Annually First Raining Period Precipitation in The Middle Part of Zhejiang and The Circulation Anomalies%浙中地区前汛期降水异常的大气环流响应

    Institute of Scientific and Technical Information of China (English)

    刘学华; 王立静; 邱小伟

    2011-01-01

    利用1953-2008年NCEP/NCAR日平均再分析资料、大气环流指数资料、浙中地区逐日降水资料.采用合成分析方法对浙中前汛期(5~7月上旬)降水异常的大气环流特征进行了分析.结果表明:降水偏多年南压高压强度较常年偏弱,高层气流辐散偏强,副热带高压强度偏强,西伸脊点明显偏西,纬向环流偏弱.经向环流偏强,印度西南季风和副热带季风偏强,冷暖空气交汇于长江中下游,造成浙中前汛期降水偏多;降水偏少年则恰好相反,南压高压偏强,高层辐散度偏弱,副高强度略偏弱,西伸脊点偏东.纬向环流偏强,印度西南季风和西南夏季风偏弱,北部冷空气偏强,南部暖空气偏弱,暖湿气流北上受阻,造成少雨.%Based on daily mean ncep reanalysis data and the circulation index data and daily precipitation data in the middle part of zhejiang, using synthesize analysis method, the linkages between the annually first raining period precipitation in the middle part of zhejiang and the circulation anomalies is analyzed, the result is that: in the more precipitation years, the intensity of south asia high is less than the mean intensity of that, but plus divergence of upper air is larger than mean intensity. The intensity of horse latitude higt is larger, and the west ridge point is more west, zonal circulation is less, and meridional circulation is larger, Indian monsoon and subtropical monsoon are larger, cold air and warm air converge in middle and lower reaches of the Changjiang River, so those work precipitation of middle part of zhejiang more. In the less precipitation years, that is reverse.

  3. 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

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

    Science.gov (United States)

    McGraw, Marie C.

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

  5. 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

  6. Anomaly holography

    Energy Technology Data Exchange (ETDEWEB)

    Gripaios, Ben [Rudolf Peierls Centre for Theoretical Physics, University of Oxford, 1 Keble Rd., Oxford OX1 3NP (United Kingdom); Merton College, Oxford OX1 4JD (United Kingdom)], E-mail: b.gripaios1@physics.ox.ac.uk; West, Stephen M. [Rudolf Peierls Centre for Theoretical Physics, University of Oxford, 1 Keble Rd., Oxford OX1 3NP (United Kingdom)], E-mail: s.west1@physics.ox.ac.uk

    2008-01-21

    We consider, in the effective field theory context, anomalies of gauge field theories on a slice of a five-dimensional, anti-de Sitter geometry and their four-dimensional, holographic duals. A consistent effective field theory description can always be found, notwithstanding the presence of the anomalies and without modifying the degrees of freedom of the theory. If anomalies do not vanish, the d=4 theory contains additional pseudoscalar states, which are either present in the low-energy theory as physical, light states, or are eaten by (would-be massless) gauge bosons. We show that the pseudoscalars ensure that global anomalies of the four-dimensional dual satisfy the 't Hooft matching condition and comment on the relevance for warped models of electroweak symmetry breaking.

  7. 2012年盛夏我国多台风特征及环流背景初步分析%Tentative analysis on multi-typhoon characteristics and atmospheric circulation background in the midsummer of 2012

    Institute of Scientific and Technical Information of China (English)

    张春艳; 王力; 孙明明; 张建海

    2012-01-01

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

  8. Sea surface temperature anomalies, planetary waves, and air-sea feedback in the middle latitudes

    Science.gov (United States)

    Frankignoul, C.

    1985-01-01

    Current analytical models for large-scale air-sea interactions in the middle latitudes are reviewed in terms of known sea-surface temperature (SST) anomalies. The scales and strength of different atmospheric forcing mechanisms are discussed, along with the damping and feedback processes controlling the evolution of the SST. Difficulties with effective SST modeling are described in terms of the techniques and results of case studies, numerical simulations of mixed-layer variability and statistical modeling. The relationship between SST and diabatic heating anomalies is considered and a linear model is developed for the response of the stationary atmosphere to the air-sea feedback. The results obtained with linear wave models are compared with the linear model results. Finally, sample data are presented from experiments with general circulation models into which specific SST anomaly data for the middle latitudes were introduced.

  9. 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.

  10. 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.

  11. 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...

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

    Science.gov (United States)

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

    2013-02-01

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

  13. 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)

  14. 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.

  15. An observed connection between wintertime temperature anomalies over Northwest China and weather regime transitions in North Atlantic

    Science.gov (United States)

    Li, Chao; Zhang, Qingyun

    2015-04-01

    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 define SAT anomaly cases. Differences 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 flow over Northwest China. Time-lagged composites reveal possible connections between the SAT anomalies and the different 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 intensified 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.

  16. 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.

  17. 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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1999-01-01

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

  19. 南半球对流层大气对热带太平洋-印度洋海温异常综合模的响应及其机制解释%Teleconnection Mode between the Tropical Pacific- Indian Ocean Temperature Anomaly and Southern Hemisphere TroposphericCirculation and Its Mechanism

    Institute of Scientific and Technical Information of China (English)

    周秋林; 梅士龙

    2011-01-01

    The teleconnection mode between the tropical Pacific- Indian Ocean temperature anomaly and Southern Hemisphere tropospheric circulation and its mechanism are studied through NOAA SST and NCEP/NCAR reanalysis data sets. First of all, spatial teleconnection mode is presented by using correlation and composition analyses and results show that there are obvious characteristics of remote response in the Southern Hemisphere troposphere closely related with the tropical Pacific- Indian Ocean temperature anomaly in boreal autumn and winter. These centers of action compose a Rossby wave train, starting from the middle of the tropical Pacific and ending in southern Africa and the tropical Indian Ocean. The train links the tropical Pacific, the Indian Ocean to the Southern Hemisphere high latitudes and plays a similar “atmosphere bridge” role. However, the pure IOD (Indian Ocean Dipole) and pure ENSO are difficult to excite teleconnection wave train in the Southern Hemisphere, which further confirms the interaction between them. Secondly, the theory of planetary wave energy propagation can be used to explain the teleconnection. It is found that the energy propagation of planetary wave with zonal numbers 1 - 3 is the possible mechanism for the teleconnection between the tropical Pacific - Indian Ocean temperature anomaly and the Southern Hemisphere tropospheric circulation.%利用NOAA SST及NCEP/NCAR再分析资料,研究了热带太平洋-印度洋海温异常综合模和南半球对流层大气之间的遥相关模态并对其进行了机制解释.首先通过相关和合成分析,给出了遥相关的空间模态,结果表明:北半球秋、冬季,在南半球对流层大气存在和热带太平洋-印度洋海温异常综合模密切联系的遥相关作用中心,该中心的分布构成一列明显的从赤道中太平洋出发,最终到达非洲中南部及赤道印度洋的Rossby波列,将赤道太平洋、印度洋与南半球中高纬度大气连接起来,起到

  20. Reconstructing atmospheric circulation over southern New Zealand: Establishment of modern westerly airflow 5500 years ago and implications for Southern Hemisphere Holocene climate change

    Science.gov (United States)

    Turney, C. S. M.; Wilmshurst, J. M.; Jones, R. T.; Wood, J. R.; Palmer, J. G.; Hogg, A. G.; Fenwick, P.; Crowley, S. F.; Privat, K.; Thomas, Z.

    2017-03-01

    Late-twentieth century changes in the intensity and migration of Southern Hemisphere westerly winds have been implicated in spatially complex variability in atmospheric and ocean circulation, and ice-sheet dynamics, across the mid- to high-latitudes. A major uncertainty, however, is whether present day hemispheric-wide symmetrical airflow is representative of past behaviour. Here we report a multi-proxy study from Stewart Island and southern Fiordland, New Zealand (46-47°S) reconstructing Holocene changes at the northern limit of westerly airflow. Increased minerogenic input and a pronounced shift in cool-loving vegetation around 5500 years ago is consistent with the establishment of westerly airflow at this latitude in the southwest Pacific. In marked contrast, stronger winds are reported further south over the subantarctic Auckland (50°S) and Campbell (52°S) Islands from 8000 years ago. Intriguingly, reconstructions from the east Pacific suggest a weakening of core westerly airflow after 8500 years ago, but an expansion along the northern limits sometime after 5500 years ago. Our results suggest similar atmospheric circulation changes have been experienced in the Pacific since 5500 years ago, but indicate an expanded network of sites is needed to comprehensively test the driver(s) and impact(s) of Holocene mid-latitude westerly winds across the Southern Hemisphere.

  1. 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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-05-28

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

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

    Science.gov (United States)

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

    2016-10-01

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

  4. 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.

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

    Science.gov (United States)

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

    2009-09-01

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

  6. A method to permanently collapse the Atlantic Meridional Overturning Circulation in climate models

    CERN Document Server

    Cimatoribus, Andrea A; Drijfhout, Sybren S; Dijkstra, Henk A

    2011-01-01

    The sensitivity of the Atlantic Meridional Overturning Circulation (AMOC) to changes in basin integrated net evaporation is highly dependent on the zonal salinity contrast at the southern border of the Atlantic. Biases in the freshwater budget strongly affect the stability of the AMOC. The impact of these biases is investigated in a coupled ocean-atmosphere model by adding local anomaly patterns to the freshwater fluxes at the surface. These anomalies impact the freshwater and salt transport by the different components of the ocean circulation, in particular the basin-scale salt-advection feedback, completely changing the response of the AMOC to arbitrary perturbations. It is found that an appropriate dipole anomaly pattern at the southern border of the Atlantic Ocean can collapse the AMOC entirely even without a further hosing. Based on these results, a method is proposed for permanently collapsing the AMOC in climate models and to systematically test the existence of multiple equilibria in these models.

  7. 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...

  8. On the effect of nuclear interactions in neutrino reactions with oxygen targets and its role in atmospheric neutrino anomaly; De l`effet des interactions nucleaires dans les reactions de neutrinos sur des cibles d`oxygene et de son role dans l`anomalie des neutrinos atmospheriques

    Energy Technology Data Exchange (ETDEWEB)

    Marteau Jacques [Inst. de Physique Nucleaire, Lyon-1 Univ., 69 - Villeurbanne (France)

    1998-12-10

    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 {Delta} 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 {Delta} 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 {mu}/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

  9. The mechanism for the impact of sea surface temperature anomaly on the ridgeline surface of Western Pacific

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Based on the atmospheric circulation data provided by ECMWF and the sea surface temperature data by NOAA, we studied the mechanism for the impact of sea surface temperature anomaly on the ridgeline surface of western Pacific using an improved high truncated spectral model. Our results show that the wave-wave interaction and the wave-mean flow interactions are weaker in the inner dynamic process of atmospheric circulation, when atmospheric circulation is forced by the sea surface temperature of El Ni-o pattern. With the external thermal forcing changed from winter to summer pattern, the range of ridgeline surface of western Pacific moving northward is smaller, which causes the ridgeline surface of western Pacific on south of normal. On the contrary, the wave-wave interaction and the wave-mean flow interaction are stronger, when atmospheric circulation is forced by the sea surface temperature of La Ni-a pattern. With the external thermal forcing turning from winter to summer pattern, the ridgeline surface of western Pacific shifts northward about 19 latitude degrees, which conduces the ridgeline surface of western Pacific on north of normal. After moving to certain latitude, the ridgeline surface of western Pacific oscillates with the most obvious 30-60 d period and the 4°-7° amplitude. It is one of the important reasons for the interannual variation of ridgeline surface of Western Pacific that the at- mospheric inner dynamical process forced out by different sea surface temperature anomaly pattern is different.

  10. 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.

  11. 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.

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

    Science.gov (United States)

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

    1984-01-01

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

  13. Poleward eddy heat flux anomalies associated with recent Arctic sea ice loss

    Science.gov (United States)

    Hoshi, Kazuhira; Ukita, Jinro; Honda, Meiji; Iwamoto, Katsushi; Nakamura, Tetsu; Yamazaki, Koji; Dethloff, Klaus; Jaiser, Ralf; Handorf, Dörthe

    2017-01-01

    Details of the characteristics of upward planetary wave propagation associated with Arctic sea ice loss under present climate conditions are examined using reanalysis data and simulation results. Recent Arctic sea ice loss results in increased stratospheric poleward eddy heat fluxes in the eastern and central Eurasia regions and enhanced upward propagation of planetary-scale waves in the stratosphere. A linear decomposition scheme reveals that this modulation of the planetary waves arises from coupling of the climatological planetary wavefield with temperature anomalies for the eastern Eurasia region and with meridional wind anomalies for the central Eurasia region. Propagation of stationary Rossby wave packets results in a dynamic link between these temperature and meridional wind anomalies with sea ice loss over the Barents-Kara Sea. The results provide strong evidence that recent Arctic sea ice loss significantly modulates atmospheric circulation in winter to modify poleward eddy heat fluxes so as to drive stratosphere-troposphere coupling processes.

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

    Science.gov (United States)

    Zhou, Botao; Xu, Ying; Shi, Ying

    2017-03-01

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

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

    Science.gov (United States)

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

    2016-10-01

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

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

    Science.gov (United States)

    Proedrou, Elisavet; Hocke, Klemens; Wurz, Peter

    2016-12-01

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

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

    Science.gov (United States)

    Tyler, Daniel; Barnes, Jeffrey R.

    2016-10-01

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

  18. Impacts of Vertical Structure of Convection on Tropical Circulation in a Warmer Climate

    Science.gov (United States)

    Chen, C. A.; Chou, C.

    2014-12-01

    The atmosphere becomes warmer and more humid under global warming, while changes in precipitation show a large discrepancy on a regional scale. Changes in regional precipitation are usually associated with changes in tropical circulation. Stronger (weaker) upward motion enhances (reduces) precipitation amount and intensity, in addition to the effect of enhanced water vapor. In a more detailed analysis, however, changes in atmospheric vertical motion can be either strengthened or weakened, even within convective areas with positive rainfall anomalies. To understand the diverse responses of changes in tropical circulation in a warmer climate as well as the associated mechanism, atmospheric stability and the impact of the vertical structure of convection on tropical circulation are investigated in 32 coupled global climate models from CMIP3 and CMIP5. The study regions are convective areas with positive precipitation anomalies. Under global warming, an upward shift structure of vertical velocity is observed in all model simulations, which implies a deepening of convection and a more stable atmosphere. Areas with enhanced (weakened) ascending motion, the climatological bottom-heavy (top-heavy) structure of vertical velocity tends to import more (less) moist static energy to counteract the stabilization due to the effect of deepened convection, and then the ascending motion is strengthened (weakened). The bottom-heavy-like structure is dominated by shallow convection, while the top-heavy-like structure is usually associated with deep convection. In other words, shallow convection tends to strengthen tropical circulation and enhance upward motion in future climate.

  19. 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.

  20. 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.

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

    Institute of Scientific and Technical Information of China (English)

    ZHOU Bo-Tao

    2012-01-01

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

  2. 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.

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

    Science.gov (United States)

    Arakawa, A.; Lamb, V. R.

    1979-01-01

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

  4. 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....

  5. 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 model....

  6. 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...

  7. 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.

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

    Science.gov (United States)

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

    2002-12-01

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

  9. Understanding severe winter haze events in the North China Plain in 2014: roles of climate anomalies

    Science.gov (United States)

    Yin, Zhicong; Wang, Huijun; Chen, Huopo

    2017-02-01

    Atmospheric pollution has become a serious environmental and social problem in China. Over the past 30 years, the number of winter (December-February) haze days over the North China Plain (WHDNCP) was greatest in 2014. In addition to anthropogenic influence, climate anomalies also played a role. Thus, it is necessary to analyze the anomalous atmosphere circulations associated with haze pollution of this year in detail. Near the surface, the weaker East Asian winter monsoon pattern, causing southerly winds over the North China Plain, could aggravate the situation of haze. In the lower and middle troposphere, taking the anticyclone circulation over North China as an intermediate system, the positive phases of the eastern Atlantic/western Russia (EA/WR), the western Pacific (WP), and the Eurasia (EU) patterns led to a worse air pollution dispersion condition that contributed to a larger number of WHDNCP. In 2014, these three patterns could be recognized from the wind anomalies in the lower troposphere. The preceding autumn (September-November) Arctic sea ice (ASI) anomalies over the eastern Hemisphere and the warmer winter surface over Eurasia might have induced or intensified the positive EA/WR pattern in 2014. These two external forcings, together with the pre-autumn sea surface temperature anomalies in the Pacific, might have also stimulated or enhanced the positive EU-like patterns. The anomalous surface temperature in autumn 2014 was efficient in intensifying anomalous circulations such as the positive phase of the WP pattern. The opposite case of minimum WHDNCP in 2010 further supports the mechanism of how EA/WR and WP patterns and associated external factors altered the local climate conditions to impact the WHDNCP.

  10. Anomaly Structure of Supergravity and Anomaly Cancellation

    CERN Document Server

    Butter, Daniel

    2009-01-01

    We display the full anomaly structure of supergravity, including new D-term contributions to the conformal anomaly. This expression has the super-Weyl and chiral U(1)_K transformation properties that are required for implementation of the Green-Schwarz mechanism for anomaly cancellation. We outline the procedure for full anomaly cancellation. Our results have implications for effective supergravity theories from the weakly coupled heterotic string theory.

  11. 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.

  12. 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.

  13. 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.

  14. Multi-time-scale hydroclimate dynamics of a regional watershed and links to large-scale atmospheric circulation: Application to the Seine river catchment, France

    Science.gov (United States)

    Massei, N.; Dieppois, B.; Hannah, D. M.; Lavers, D. A.; Fossa, M.; Laignel, B.; Debret, M.

    2017-03-01

    In the present context of global changes, considerable efforts have been deployed by the hydrological scientific community to improve our understanding of the impacts of climate fluctuations on water resources. Both observational and modeling studies have been extensively employed to characterize hydrological changes and trends, assess the impact of climate variability or provide future scenarios of water resources. In the aim of a better understanding of hydrological changes, it is of crucial importance to determine how and to what extent trends and long-term oscillations detectable in hydrological variables are linked to global climate oscillations. In this work, we develop an approach associating correlation between large and local scales, empirical statistical downscaling and wavelet multiresolution decomposition of monthly precipitation and streamflow over the Seine river watershed, and the North Atlantic sea level pressure (SLP) in order to gain additional insights on the atmospheric patterns associated with the regional hydrology. We hypothesized that: (i) atmospheric patterns may change according to the different temporal wavelengths defining the variability of the signals; and (ii) definition of those hydrological/circulation relationships for each temporal wavelength may improve the determination of large-scale predictors of local variations. The results showed that the links between large and local scales were not necessarily constant according to time-scale (i.e. for the different frequencies characterizing the signals), resulting in changing spatial patterns across scales. This was then taken into account by developing an empirical statistical downscaling (ESD) modeling approach, which integrated discrete wavelet multiresolution analysis for reconstructing monthly regional hydrometeorological processes (predictand: precipitation and streamflow on the Seine river catchment) based on a large-scale predictor (SLP over the Euro-Atlantic sector). This

  15. Arctic sea-ice cover and sea-ice cover anomalies over eastern Canadian waters

    Energy Technology Data Exchange (ETDEWEB)

    Agnew, T.

    1990-01-01

    Concerns about global climate warming have increased interest in climate monitoring and analysis of climate trends in Canada. Sea-ice cover is of interest for climate monitoring since it is very sensitive to changes in the climate controls over a region and is an integrator of temperature anomalies over periods of a week and longer. In addition, climate models suggest that polar regions will have the largest climate warming signal. The existence of long-term digital sea-ice databases makes analysis of sea ice as a climate change indicator possible. The northern hemisphere sea-ice concentration database for 1953 to 1988 was qualitatively evaluated for its representativeness over eastern Canadian Arctic waters. Despite inhomogeneity problems, the database identifies the average freezeup and breakup patterns in the Canadian Arctic islands, Baffin Bay/Davis Strait, and the Hudson Bay area, and can be used for sea-ice variability and anomaly studies. However, inhomogeneity problems put into question the use of the database for sea-ice trend analysis. Sea-ice anomalies for the 1982/83 El Nino winter are compared to atmospheric temperature and circulation anomalies over the Baffin Bay/Davis Strait area. Sea-ice anomaly charts for 1953-1988 are calculated and have been made available as an unpublished catalogue within the Canadian Climate Centre. 15 refs., 27 figs.

  16. The 1985 southern hemisphere mid-latitude total column ozone anomaly

    Directory of Open Access Journals (Sweden)

    G. E. Bodeker

    2007-05-01

    Full Text Available One of the most significant events in the evolution of the ozone layer over southern mid-latitudes since the late 1970s was the large decrease observed in 1985. This event remains unexplained and most state-of-the-art atmospheric chemistry-transport models are unable to reproduce it. In this study, the 1985 southern hemisphere mid-latitude total column ozone anomaly is analyzed in detail based on observed daily total column ozone fields, stratospheric dynamical fields, and calculated diagnostics of stratospheric mixing. The 1985 anomaly appears to result from a combination of (i an anomaly in the meridional circulation resulting from the westerly phase of the equatorial quasi-biennial oscillation (QBO, (ii weaker transport of ozone from its tropical mid-stratosphere source across the sub-tropical barrier to mid-latitudes related to the particular phasing of the QBO with respect to the annual cycle, and (iii a solar cycle induced local reduction in ozone. The results based on observations are compared and contrasted with analyses of ozone and dynamical fields from the ECHAM4.L39(DLR/CHEM coupled chemistry-climate model (hereafter referred to as E39C. Equatorial winds in the E39C model are nudged towards observed winds between 10° S and 10° N and the ability of this model to produce an ozone anomaly in 1985, similar to that observed, confirms the role of the QBO in the anomaly.

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

    Institute of Scientific and Technical Information of China (English)

    吕心艳

    2011-01-01

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

  18. 2012年8月大气环流和天气分析%Analysis of the August 2012 Atmospheric Circulation and Weather

    Institute of Scientific and Technical Information of China (English)

    陶亦为

    2012-01-01

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

  19. 2012年9月大气环流和天气分析%Analysis of the September 2012 Atmospheric Circulation and Weather

    Institute of Scientific and Technical Information of China (English)

    钱奇峰

    2012-01-01

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

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

    Science.gov (United States)

    Podnebesnykh, Nataliya

    2014-05-01

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

  1. Sea-ice cover anomalies in the Arctic Basin associated with atmospheric variability from multi-decadal trends to intermittent quasi-biennial oscillations

    Directory of Open Access Journals (Sweden)

    Motoyoshi Ikeda

    2012-06-01

    Full Text Available Arctic Ocean sea ice has been diminishing since 1970, as shown by National Snow and Ice Data Center data. In addition to decadal variability, low ice anomalies in the Pacific–Siberian region have been occurring at shorter timescales. The influence of the widely-known Northern Annular Mode (NAM occurs across all seasons. In this study, empirical orthogonal function (EOF analysis was applied to sea-level pressure in National Centers for Environmental Prediction Reanalysis data for 1960–2007, showing the NAM to be the leading mode of variability and the Arctic Dipole Mode (ADM to be the second leading mode. The ADM changes markedly across seasons. In autumn–winter, it has a pole over Siberia and a pole over Greenland, at opposite signs at a several-year scale, whereas the spring–summer ADM (ADMSS has a pole over Europe and a pole over Canada. In the 1980s, the most influential mode shifted from the NAM to the ADM, when the Pacific sector had low ice cover at a 1-year lag from the positive ADM, which was marked by low pressure over Siberia. In years when the ADMSS was pronounced, it was responsible for distinct ice variability over the East Siberian–Laptev seas. The frequency separation in this study identified the contributions of the ADM and ADMSS. Effects of the latter are difficult to predict since it is intermittent and changes its sign biennially. The ADM and ADMSS should be closely watched in relation to the ongoing ice reduction in the Pacific–Siberian region.

  2. Sensitivity of Asian Summer Monsoon precipitation to tropical sea surface temperature anomalies

    Science.gov (United States)

    Fan, Lei; Shin, Sang-Ik; Liu, Zhengyu; Liu, Qinyu

    2016-10-01

    Sensitivity of Asian Summer Monsoon (ASM) precipitation to tropical sea surface temperature (SST) anomalies was estimated from ensemble simulations of two atmospheric general circulation models (GCMs) with an array of idealized SST anomaly patch prescriptions. Consistent sensitivity patterns were obtained in both models. Sensitivity of Indian Summer Monsoon (ISM) precipitation to cooling in the East Pacific was much weaker than to that of the same magnitude in the local Indian-western Pacific, over which a meridional pattern of warm north and cold south was most instrumental in increasing ISM precipitation. This indicates that the strength of the ENSO-ISM relationship is due to the large-amplitude East Pacific SST anomaly rather than its sensitivity value. Sensitivity of the East Asian Summer Monsoon (EASM), represented by the Yangtze-Huai River Valley (YHRV, also known as the meiyu-baiu front) precipitation, is non-uniform across the Indian Ocean basin. YHRV precipitation was most sensitive to warm SST anomalies over the northern Indian Ocean and the South China Sea, whereas the southern Indian Ocean had the opposite effect. This implies that the strengthened EASM in the post-Niño year is attributable mainly to warming of the northern Indian Ocean. The corresponding physical links between these SST anomaly patterns and ASM precipitation were also discussed. The relevance of sensitivity maps was justified by the high correlation between sensitivity-map-based reconstructed time series using observed SST anomaly patterns and actual precipitation series derived from ensemble-mean atmospheric GCM runs with time-varying global SST prescriptions during the same period. The correlation results indicated that sensitivity maps derived from patch experiments were far superior to those based on regression methods.

  3. The Atmospheric Bridge: The Influence of ENSO Teleconnections on Air-Sea Interaction over the Global Oceans.

    Science.gov (United States)

    Alexander, Michael A.; Bladé, Ileana; Newman, Matthew; Lanzante, John R.; Lau, Ngar-Cheung; Scott, James D.

    2002-08-01

    During El Niño-Southern Oscillation (ENSO) events, the atmospheric response to sea surface temperature (SST) anomalies in the equatorial Pacific influences ocean conditions over the remainder of the globe. This connection between ocean basins via the `atmospheric bridge' is reviewed through an examination of previous work augmented by analyses of 50 years of data from the National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP-NCAR) reanalysis project and coupled atmospheric general circulation (AGCM)-mixed layer ocean model experiments. Observational and modeling studies have now established a clear link between SST anomalies in the equatorial Pacific with those in the North Pacific, north tropical Atlantic, and Indian Oceans in boreal winter and spring. ENSO-related SST anomalies also appear to be robust in the western North Pacific during summer and in the Indian Ocean during fall. While surface heat fluxes are the key component of the atmospheric bridge driving SST anomalies, Ekman transport also creates SST anomalies in the central North Pacific although the full extent of its impact requires further study. The atmospheric bridge not only influences SSTs on interannual timescales but also affects mixed layer depth (MLD), salinity, the seasonal evolution of upper-ocean temperatures, and North Pacific SST variability at lower frequencies. The model results indicate that a significant fraction of the dominant pattern of low-frequency (>10 yr) SST variability in the North Pacific is associated with tropical forcing. AGCM experiments suggest that the oceanic feedback on the extratropical response to ENSO is complex, but of modest amplitude. Atmosphere-ocean coupling outside of the tropical Pacific slightly modifies the atmospheric circulation anomalies in the Pacific-North America (PNA) region but these modifications appear to depend on the seasonal cycle and air-sea interactions both within and beyond the North Pacific Ocean.

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

    Directory of Open Access Journals (Sweden)

    Nobuaki Kimura

    2014-01-01

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

  5. 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.

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

    Science.gov (United States)

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

    2016-10-01

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

  7. 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)

  8. Effects of Sea Surface Temperature Anomalies off the East Coast of Japan on Development of the Okhotsk High

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The study examined effects of sea surface temperature anomalies (SSTAs) off the east coast of Japan on the blocking high over the Okhotsk Sea in June by diagnostic analysis and numerical simulation. Firstly,based on 500-hPa geopotential height fields, the Okhotsk high index (OKHI) for June from 1951 to 2000is calculated and analyzed. The result indicates that the OKHI has obvious inter-annual and inter-decadal variations, and there are 9 yr of high OKHI and 8 yr of low OKHI in 50 yr. Secondly, by using the OKHI, the relationship between the Okhotsk high and the 500-hPa geopotential height anomaly is investigated. The results indicate that the "+-+" pattern of geopotential height anomaly crossing Eurasia in the mid-high latitudes and the "+-" pattern of geopotential height anomaly from high to low latitudes over East Asia are in favor of the formation and maintenance of the Okhotsk high. The relationship between the OKHI and the SSTA over the North Pacific is investigated in early summer by using correlation and composite analysis.We found that when the blocking circulation over the Okhotsk Sea occurs, there is an obvious negative SSTA off the east coast of Japan in early summer. We simulated the effects of the negative SSTA of east coast of Japan on the atmospheric circulation anomaly over East Asia through the control and sensitivity experiments using NCAR CAM3 model in order to confirm our analysis results. The simulation shows that the negative SSTA off the east coast of Japan results in the significant positive 40 gpm 500-hPa geopotential height anomaly over the Okhotsk Sea and the negative anomalies off the east coast of Japan which might contribute to the formation and development of the Okhotsk high in June.

  9. Moderate to heavy cold-weather precipitation occurrences in Tehran and the associated circulation types

    Science.gov (United States)

    Khansalari, Sakineh; Raziei, Tayeb; Mohebalhojeh, Ali Reza; Ahmadi-Givi, Farhang

    2017-01-01

    Large-scale atmospheric circulations associated with 133 moderate to heavy cold-weather precipitation events recorded at Mehrabad station in Tehran, Iran, during the period 1951-2013 are analysed. To this end, the performance of un-rotated, orthogonally rotated and obliquely rotated solutions of T-mode principal component analysis (PCA) is examined in classifying the atmospheric circulations into a few representative circulation types (CTs). The T-mode PCAs were applied to the 500-hPa geopotential height for the events in a domain from 10∘E to 70∘E and from 20∘N to 50∘N. The first six leading principal components were retained and then orthogonally and obliquely rotated using varimax and promax solutions, respectively. Statistical inter-comparison of the CTs obtained using the three solutions suggests that the obliquely rotated solution is the better choice for circulation classification in the present study. The six CTs obtained using the oblique rotation were then linked to the daily total precipitation and daily mean temperature variability at Tehran station as well as to the standardized anomalies of the daily total precipitation and mean daily temperature of a dense network of stations distributed across Iran. It is found that the CTs identified, though generally comparable in producing significant precipitation in Tehran, vary in their potential to bring cold weather and generate snowfall in Tehran specifically and in the country in general. While the first three CTs give rise to regional patterns of standardized precipitation anomalies centred in Tehran, the next three CTs leave a pronounced precipitation signature almost across the whole country. As regards the standardized temperature anomalies, with the exception of one CT that causes deep and widespread negative standardized anomalies over most parts of the country, the other CTs are characterized with a dipolar structure of a deep intrusion of cold weather to the west and prevailing warm weather

  10. Climate Prediction Center (CPC) Zonally Average 500 MB Temperature 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 500-hPa temperature anomalies averaged over the latitude band 20oN ? 20oS. The anomalies are...

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

    Institute of Scientific and Technical Information of China (English)

    秦成云; 吴洪军; 汤洁; 封洋; 夏网萍

    2013-01-01

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

  12. Snow anomaly events from historical documents in eastern China during the past two millennia and implication for low-frequency variability of AO/NAO and PDO

    Science.gov (United States)

    Chu, Guoqiang; Sun, Qing; Wang, Xiaohua; Sun, Junying

    2008-07-01

    Models and instrumental data indicate that the spatial and temporal variations of snow cover are significantly related to atmospheric circulation (e.g. the AO/NAO). Here, we present historical snow anomaly events during the past two millennia that provide a unique temporal window to studying long-term AO/NAO, a prominent phenomenon in wintertime. Direct descriptions such as ``no snow during the winter'' and ``pray God for snow'' are interpreted as convincing evidence for snow anomalies. The variations of positive/negative snow abnormal events show clear decadal to century variations during the past two millennia. Based on the previous instrumental research and comparison with other reconstruction data, we suggest the Index of Abnormal Snow (IAS) may be an AO-like atmospheric variability. The winter during the Medieval Warm Period (MWP) (AD 900-1300) might be strongly influenced by a predominantly positive AO with less snow condition, whereas the Little Ice Age (LIA) (AD 1300-1900) by negative AO concomitant with heavier snowfalls in East Asia. Our data show that a warm climate period (the MWP)/a cold period (the LIA) can be perturbed by a cold spell/a warm spell which are linked with a change in atmospheric circulation. Low-frequency variability of snow records may be intrinsic to the natural climate system. Although the dynamic mechanisms linking snow anomalies with atmospheric circulation (the AO/NAO, the PDO) is unclear on the decadal to century time scales, Pacific Ocean may play an important role in regulating atmospheric circulations since the IAS is highly correlated with the reconstruction of PDO.

  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. Characterising the relationship between weather extremes in Europe and synoptic circulation features

    Directory of Open Access Journals (Sweden)

    S. Pfahl

    2014-02-01

    Full Text Available Extreme weather events in Europe are closely linked to anomalies of the atmospheric circulation and in particular to circulation features like cyclones and atmospheric blocking. In this study, this linkage is systematically characterised with the help of conditional cyclone and blocking frequencies during precipitation, wind gust and temperature extremes at various locations in Europe. Such conditional frequency fields can serve as a dynamical fingerprint of the extreme events and yield insights into their most important physical driving mechanisms. Precipitation extremes over the ocean and over flat terrain are shown to be closely related to cyclones in the vicinity and the associated dynamical lifting. For extreme precipitation over complex terrain, cyclone anomalies are found at more remote locations, favouring the flow of moist air towards the topography. Wind gust extremes are associated with cyclone and blocking anomalies in opposite directions, with the cyclones occurring mostly over the North and Baltic Seas for extreme events in central Europe. This setting is associated with pronounced surface pressure gradients and thus high near-surface wind velocities. Hot temperature extremes in northern and central Europe typically occur in the vicinity of a blocking anticyclone, where subsidence and radiative forcing are strong. Over southern Europe, blocking anomalies are shifted more to the north or northeast, indicating a more important role of warm air advection. Large-scale flow conditions for cold extremes are similar at many locations in Europe, with blocking anomalies over the North Atlantic and northern Europe and cyclone anomalies southeast of the cold extreme, both contributing to the advection of cold air masses. This characterisation of synoptic-scale forcing mechanisms can be helpful for better understanding and anticipating weather extremes and their long-term changes.

  15. Walker circulation in a transient climate

    Science.gov (United States)

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

    2016-04-01

    The tropical overturning circulations modulate the heat exchange across the tropics and between the tropics and the poles. The anthropogenic influence on the climate system will affect these circulations, impacting the dynamics of the Earth system. In this work we focus on the Walker circulation. We investigate its temporal and spatial dynamical changes and their link to other climate features, such as surface and sea-surface temperature patterns, El-Niño Southern Oscillation (ENSO), and ocean heat-uptake, both at global and regional scale. In order to determine the impact of anthropogenic climate change on the tropical circulation, we analyze the outputs of 28 general circulation models (GCMs) from the CMIP5 project. We use the experiment with 1% year-1 increase in CO2 concentration from pre-industrial levels to quadrupling of the concentration. Consistent with previous studies (ex. Ma and Xie 2013), we find that for this experiment most GCMs associate a weakening Walker circulation to a warming transient climate. Due to the role of the Walker Pacific cell in the meridional heat and moisture transport across the tropical Pacific and also the connection to ENSO, we find that a weakened Walker circulation correlates with more extreme El-Niño events, although without a change in their frequency. The spatial analysis of the Pacific Walker cell suggests an eastward displacement of the ascending branch, which is consistent with positive SST anomalies over the tropical Pacific and the link of the Pacific Walker cell to ENSO. Recent studies (ex. England et al. 2014) have linked a strengthened Walker circulation to stronger ocean heat uptake, especially in the western Pacific. The inter-model comparison of the correlation between Walker circulation intensity and ocean heat uptake does not convey a robust response for the investigated experiment. However, there is some evidence that a stronger weakening of the Walker circulation is linked to a higher transient climate

  16. Fetal Circulation

    Science.gov (United States)

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

  17. 2013年11月大气环流和天气分析%Analysis of the November 2013 Atmospheric Circulation and Weather

    Institute of Scientific and Technical Information of China (English)

    赖芬芬; 何立富

    2014-01-01

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

  18. Coupled atmosphere-mixed layer ocean response to ocean heat flux convergence along the Kuroshio current extension

    Energy Technology Data Exchange (ETDEWEB)

    Kwon, Young-Oh [Woods Hole Oceanographic Institution, Physical Oceanography Department, Woods Hole, MA (United States); Deser, Clara [National Center for Atmospheric Research, Boulder, CO (United States); Cassou, Christophe [CNRS-CERFACS, Toulouse (France)

    2011-06-15

    The winter response of the coupled atmosphere-ocean mixed layer system to anomalous geostrophic ocean heat flux convergence in the Kuroshio Extension is investigated by means of experiments with an atmospheric general circulation model coupled to an entraining ocean mixed layer model in the extra-tropics. The direct response consists of positive SST anomalies along the Kuroshio Extension and a baroclinic (low-level trough and upper-level ridge) circulation anomaly over the North Pacific. The low-level component of this atmospheric circulation response is weaker in the case without coupling to an extratropical ocean mixed layer, especially in late winter. The inclusion of an interactive mixed layer in the tropics modifies the direct coupled atmospheric response due to a northward displacement of the Pacific Inter-Tropical Convergence Zone which drives an equivalent barotropic anomalous ridge over the North Pacific. Although the tropically driven component of the North Pacific atmospheric circulation response is comparable to the direct response in terms of sea level pressure amplitude, it is less important in terms of wind stress curl amplitude due to the mitigating effect of the relatively broad spatial scale of the tropically forced atmospheric teleconnection. (orig.)

  19. Early 21st Century Anomalously Cold Central Eurasian Winters Forced By Arctic Sea Ice Retreat in an Atmosphere Model

    Science.gov (United States)

    Semenov, V. A.; Latif, M.

    2014-12-01

    The early 21st century was marked by several severe winters over Central Eurasia linked to a blocking anti-cyclone centered south of the Barents Sea (BS). The increased occurrence of such anomalously cold winters coincided with a strong reduction of winter Arctic sea ice cover (ASIC), especially in the BS where sea ice area exhibited a step-like decline in 2005, suggesting a possible connection. To study the possible link we performed simulations with a high-resolution global atmospheric general circulation model forced by a set of multi-year sea ice anomalies observed during the last decades. The regional circulation response to reduced ASIC in 2005-2012 exhibits a statistically significant anti-cyclonic surface pressure anomaly and a surface temperature response similar to that observed. The results suggest that the recent BS sea ice reduction may have been responsible for the recent anomalously cold winters in Central Eurasia. Furthermore, a positive sea ice anomaly in the late 1960s associated with negative phase of the North Atlantic Oscillation also results in a similar anti-cyclonic anomaly and a cooling over the continent in the model. This implies that the atmospheric circulation response to sea ice anomalies during the period of modern sea ice decline can be essentially non-linear, both with respect to amplitude and pattern.

  20. 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

  1. Relationship between SSTA in the northwestern Pacific and winter climate anomaly in China

    Institute of Scientific and Technical Information of China (English)

    QIN Huiling; JIAN Maoqiu; YUAN Zhuojian

    2004-01-01

    The relationship between sea surface temperature anomaly (SSTA) in the domain from the northwest of thc Pacific to Chinaseas (NWP-CS) andclimate (precipitation and surface temperature) anomaly in winters over east of Chinese Mainland (ECM) are investigated with composite analysis. The results suggest that (1) SSTA in NWP-CS usually appears as "seesaw" pattern, I.e., sign of SSTA in the northwest of thc Philippines is positive (negative) while in the southeast it is negative (positive), defmed as SSTA "seesaw" positive (negative) pattern. When SSTA "seesaw" positive(negative) pattern appears, the surface temperature in ECM is higher (lower) than the normal winters but thc precipitation anomaly is not distinct; (2) there are two anomalous anticyclones (cyclones) locating in the northwest Pacific and east of the Philippines at 850 hPa level and an anomalous anti-Hadley (Hadley) circulation, which descends (ascends)south of 18°N, ascends (descends) north of 18°N; (3) heat flux anomaly from ocean into atmosphere is weaker (stronger)in the northwest of the Philippines but stronger (weaker) in the southeast of the Philippines than the normal winters, because the weaker (stronger) northerly prevails in thc northwest of the Philippines and stronger (weaker) northeaster in the southeast of the Philippines induced by anomalous anticyclones (cyclones).

  2. Interannual variability of South American monsoon circulation

    Science.gov (United States)

    Alonso Gan, Manoel; Rafaele Araújo Lima, Jeane

    2016-04-01

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

  3. Gauge mediated supersymmetry breaking and neutrino anomalies

    CERN Document Server

    Joshipura, A S; Joshipura, Anjan S.; Vempati, Sudhir K.

    1999-01-01

    Supersymmetric standard model with softly broken lepton symmetry provides a suitable framework to accommodate the solar and atmospheric neutrino anomalies. This model contains a natural explanation for large mixing and hierarchal masses without fine tuning of the parameters. Neutrino spectrum is particularly constrained in the minimal messenger model (MMM) of gauge mediated SUSY breaking, since all SUSY breaking effects are controlled in MMM by a single parameter. We study the structure of neutrino masses and mixing both in MMM and in simple extensions of it in the context of solar and atmospheric neutrino anomalies.

  4. Large-scale atmospheric circulation biases and changes in global climate model simulations and their importance for climate change in Central Europe

    Directory of Open Access Journals (Sweden)

    A. P. van Ulden

    2006-01-01

    Full Text Available The quality of global sea level pressure patterns has been assessed for simulations by 23 coupled climate models. Most models showed high pattern correlations. With respect to the explained spatial variance, many models showed serious large-scale deficiencies, especially at mid-latitudes. Five models performed well at all latitudes and for each month of the year. Three models had a reasonable skill. We selected the five models with the best pressure patterns for a more detailed assessment of their simulations of the climate in Central Europe. We analysed observations and simulations of monthly mean geostrophic flow indices and of monthly mean temperature and precipitation. We used three geostrophic flow indices: the west component and south component of the geostrophic wind at the surface and the geostrophic vorticity. We found that circulation biases were important, and affected precipitation in particular. Apart from these circulation biases, the models showed other biases in temperature and precipitation, which were for some models larger than the circulation induced biases. For the 21st century the five models simulated quite different changes in circulation, precipitation and temperature. Precipitation changes appear to be primarily caused by circulation changes. Since the models show widely different circulation changes, especially in late summer, precipitation changes vary widely between the models as well. Some models simulate severe drying in late summer, while one model simulates significant precipitation increases in late summer. With respect to the mean temperature the circulation changes were important, but not dominant. However, changes in the distribution of monthly mean temperatures, do show large indirect influences of circulation changes. Especially in late summer, two models simulate very strong warming of warm months, which can be attributed to severe summer drying in the simulations by these models. The models differ also

  5. 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).

  6. Long-term sedimentary recycling of rare sulphur isotope anomalies

    OpenAIRE

    Reinhard, Christopher T.; Planavsky, Noah J.; Lyons, Timothy W.

    2013-01-01

    The accumulation of substantial quantities of O_2 in the atmosphere has come to control the chemistry and ecological structure of Earth’s surface. Non-mass-dependent (NMD) sulphur isotope anomalies in the rock record are the central tool used to reconstruct the redox history of the early atmosphere. The generation and initial delivery of these anomalies to marine sediments requires low partial pressures of atmospheric O_2 (PO_2; refs 2, 3), and the disappearance of NMD anomalies from the rock...

  7. EFFECTS OF THE ATMOSPHERIC COLD SOURCE OVER THE TIBETAN PLATEAU ON THE QUASI 4-YEAR OSCILLATION OF OCEAN-ATMOSPHERIC-LAND INTERACTION

    Institute of Scientific and Technical Information of China (English)

    ZHANG Bo; CHEN Long-xun; ZHOU Xiu-ji; ZHAO Bin

    2009-01-01

    Using correlation analyses,composite analyses,and singular value decomposition,the relationship between the atmospheric cold source over the eastern Tibetan Plateau and atmospheric/ocean circulation is discussed. In winter,the anomaly of the strong (weak) atmospheric cold source over the eastern plateau causes low-level anomalous north (south) winds to appear in eastern China and low-level anomaly zonal west (east) winds to prevail in the equatorial Pacific from spring to autumn. This contributes to the anomalous warm (cold) sea surface temperature the following autumn and winter. In addition,the anomalous variation of sea surface temperature over the equatorial middle and eastern Pacific in winter can influence the snow depth and intensity of the cold source over the plateau in the following winter due to variation of the summer west Pacific subtropical high.

  8. 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

  9. 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.

  10. Long-term sedimentary recycling of rare sulphur isotope anomalies.

    Science.gov (United States)

    Reinhard, Christopher T; Planavsky, Noah J; Lyons, Timothy W

    2013-05-01

    The accumulation of substantial quantities of O2 in the atmosphere has come to control the chemistry and ecological structure of Earth's surface. Non-mass-dependent (NMD) sulphur isotope anomalies in the rock record are the central tool used to reconstruct the redox history of the early atmosphere. The generation and initial delivery of these anomalies to marine sediments requires low partial pressures of atmospheric O2 (p(O2); refs 2, 3), and the disappearance of NMD anomalies from the rock record 2.32 billion years ago is thought to have signalled a departure from persistently low atmospheric oxygen levels (less than about 10(-5) times the present atmospheric level) during approximately the first two billion years of Earth's history. Here we present a model study designed to describe the long-term surface recycling of crustal NMD anomalies, and show that the record of this geochemical signal is likely to display a 'crustal memory effect' following increases in atmospheric p(O2) above this threshold. Once NMD anomalies have been buried in the upper crust they are extremely resistant to removal, and can be erased only through successive cycles of weathering, dilution and burial on an oxygenated Earth surface. This recycling results in the residual incorporation of NMD anomalies into the sedimentary record long after synchronous atmospheric generation of the isotopic signal has ceased, with dynamic and measurable signals probably surviving for as long as 10-100 million years subsequent to an increase in atmospheric p(O2) to more than 10(-5) times the present atmospheric level. Our results can reconcile geochemical evidence for oxygen production and transient accumulation with the maintenance of NMD anomalies on the early Earth, and suggest that future work should investigate the notion that temporally continuous generation of new NMD sulphur isotope anomalies in the atmosphere was likely to have ceased long before their ultimate disappearance from the rock record.

  11. Nearshore circulation

    NARCIS (Netherlands)

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

    1990-01-01

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

  12. 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.

  13. 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 terrestrial...

  14. 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.

  15. Anomaly-induced baryogenesis

    CERN Document Server

    Kobakhidze, A

    2004-01-01

    We propose a new mechanism for dynamical generation of the observed baryon asymmetry within the minimal Standard model extended by massive Majorana neutrinos and non-vanishing electroweak Chern-Simons term. We show that electroweak Chern-Simons number is produced in the expanding universe due to the conformal anomaly and subsequently converted into baryon number through the triangle anomaly.

  16. Competing Orders and Anomalies.

    Science.gov (United States)

    Moon, Eun-Gook

    2016-08-08

    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.

  17. 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

  18. 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.

  19. Simulation of seasonal cloud forcing anomalies

    Energy Technology Data Exchange (ETDEWEB)

    Randall, D.A.

    1990-08-01

    One useful way to classify clouds is according to the processes that generate them. There are three main cloud-formation agencies: deep convection; surface evaporation; large-scale lifting in the absence of conditional instability. Although traditionally clouds have been viewed as influencing the atmospheric general circulation primarily through the release of latent heat, the atmospheric science literature contains abundant evidence that, in reality, clouds influence the general circulation through four more or less equally important effects: interactions with the solar and terrestrial radiation fields; condensation and evaporation; precipitation; small-scale circulations within the atmosphere. The most advanced of the current generation of GCMs include parameterizations of all four effects. Until recently there has been lingering skepticism, in the general circulation modeling community, that the radiative effects of clouds significantly influence the atmospheric general circulation. GCMs have provided the proof that the radiative effects of clouds are important for the general circulation of the atmosphere. An important concept in analysis of the effects of clouds on climate is the cloud radiative forcing (CRF), which is defined as the difference between the radiative flux which actually occurs in the presence of clouds, and that which would occur if the clouds were removed but the atmospheric state were otherwise unchanged. We also use the term CRF to denote warming or cooling tendencies due to cloud-radiation interactions. Cloud feedback is the change in CRF that accompanies a climate change. The present study concentrates on the planetary CRF and its response to external forcing, i.e. seasonal change.

  20. 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.

  1. 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...

  2. 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...

  3. Scattering anomaly in optics

    CERN Document Server

    Silveirinha, Mario G

    2016-01-01

    In time-reversal invariant electronic systems the scattering matrix is anti-symmetric. This property enables an effect, designated here as "scattering anomaly", such that the electron transport does not suffer from back reflections, independent of the specific geometry of the propagation path or the presence of time-reversal invariant defects. In contrast, for a generic time-reversal invariant photonic system the scattering matrix is symmetric and there is no similar anomaly. Here, it is theoretically proven that despite these fundamental differences there is a wide class of photonic platforms - in some cases formed only by time-reversal invariant media - in which the scattering anomaly can occur. It is shown that an optical system invariant under the action of the composition of the time-reversal, parity and duality operators is characterized by an anti-symmetric scattering matrix. Specific examples of photonic platforms wherein the scattering anomaly occurs are given, and it is demonstrated with full wave n...

  4. DREDed Anomaly Mediation

    CERN Document Server

    Boyda, E; Pierce, A T; Boyda, Ed; Murayama, Hitoshi; Pierce, Aaron

    2002-01-01

    We offer a guide to dimensional reduction (DRED) in theories with anomaly mediated supersymmetry breaking. Evanescent operators proportional to epsilon arise in the bare Lagrangian when it is reduced from d=4 to d= (4-2 epsilon) dimensions. In the course of a detailed diagrammatic calculation, we show that inclusion of these operators is crucial. The evanescent operators conspire to drive the supersymmetry-breaking parameters along anomaly-mediation trajectories across heavy particle thresholds, guaranteeing the ultraviolet insensitivity.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

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

    Science.gov (United States)

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

    2002-01-01

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

  10. SADM potentiometer anomaly investigations

    Science.gov (United States)

    Wood, Brian; Mussett, David; Cattaldo, Olivier; Rohr, Thomas

    2005-07-01

    During the last 3 years Contraves Space have been developing a Low Power (1-2kW) Solar Array Drive Mechanism (SADM) aimed at small series production. The mechanism was subjected to two test programmes in order to qualify the SADM to acceptable levels. During the two test programmes, anomalies were experienced with the Potentiometers provided by Eurofarad SA and joint investigations were undertaken to resolve why these anomalies had occurred. This paper deals with the lessons learnt from the failure investigation on the two Eurofarad (rotary) Potentiometer anomaly. The Rotary Potentiometers that were used were fully redundant; using two back to back mounted "plastic tracks". It is a pancake configuration mounted directly to the shaft of the Slip Ring Assembly at the extreme in-board end of the SADM. It has no internal bearings. The anomaly initially manifested itself as a loss of performance in terms of linearity, which was first detected during Thermal Vacuum testing. A subsequent anomaly manifested itself by the complete failure of the redundant potentiometer again during thermal vacuum testing. This paper will follow and detail the chain of events following this anomaly and identifies corrective measures to be applied to the potentiometer design and assembly process.

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

    OpenAIRE

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

    2016-01-01

    The Dolomite Alps of northeastern Italy experience debris flows with great frequency during the summer months. An ample supply of unconsolidated material on steep slopes and a summer season climate regime characterized by recurrent thunderstorms combine to produce an abundance of these destructive hydro-geologic events. In the past, debris flow events have been studied primarily in the context of their geologic and geomorphic characteristics. The atmospheric contribution to ...

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

    OpenAIRE

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

    2015-01-01

    The Dolomite Alps of northeastern Italy experience debris flows with great frequency during the summer months. An ample supply of unconsolidated material on steep slopes and a summer season climate regime characterized by recurrent thunderstorms combine to produce an abundance of these destructive hydrogeologic events. In the past debris flow events have been studied primarily in the context of their geologic and geomorphic characteristics. The atmospheric contribution to th...

  13. 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.

  14. Neutrino anomalies and large extra dimensions

    CERN Document Server

    Dighe, A S; Dighe, Amol S.; Joshipura, Anjan S.

    2001-01-01

    Theories with large extra dimensions can generate small neutrino masses when the standard model neutrinos are coupled to singlet fermions propagating in higher dimensions. The couplings can also generate mass splittings and mixings among the flavour neutrinos in the brane. We systematically study the minimal scenario involving only one singlet bulk fermion coupling weakly to the flavour neutrinos. We explore the neutrino mass structures in the brane that can potentially account for the atmospheric, solar and LSND anomalies simultaneously in a natural way. We demonstrate that in the absence of a priori mixings among the SM neutrinos, it is not possible to reconcile all these anomalies. The presence of some structure in the mass matrix of the SM neutrinos can solve this problem. This is exemplified by the Zee model, which when embedded in extra dimensions in a minimal way can account for all the neutrino anomalies.

  15. Severe winter weather as a response to the lowest Arctic sea-ice anomalies

    Institute of Scientific and Technical Information of China (English)

    CHEN Hongxia; LIU Na; ZHANG Zhanhai

    2013-01-01

    Possible impact of reduced Arctic sea-ice on winter severe weather in China is investigated regarding the snowstorm over southern China in January 2008. The sea-ice conditions in the summer (July-September) and fall (September-November) of 2007 show that the sea-ice is the lowest that year. During the summer and fall of 2007, sea ice displayed a significant decrease in the East Siberian, the northern Chukchi Sea, the western Beaufort Sea, the Barents Sea, and the Kara Sea. A ECHAM5.4 atmospheric general circula-tion model is forced with realistic sea-ice conditions and strong thermal responses with warmer surface air temperature and higher-than-normal heat flux associated with the sea-ice anomalies are found. The model shows remote atmospheric responses over East Asia in January 2008, which result in severe snowstorm over southern China. Strong water-vapor transported from the Bay of Bengal and from the Pacific Ocean related to Arctic sea-ice anomalies in the fall (instead of summer) of 2007 is considered as one of the main causes of the snowstorm formation.

  16. Low frequency variability of the Indian Ocean from TOPEX/POSEIDON sea surface height anomalies

    Digital Repository Service at National Institute of Oceanography (India)

    Somayajulu, Y.K.; Murty, V.S.N.; Sarma, Y.V.B.

    The sea surface height (SSH) anomalies derived from TOPEX/POSEIDON altimeter have been utilized to study the variability of surface circulation in the Indian Ocean during 1993-1999. The Western Bay, southeastern Arabian Sea, regions off Somalia...

  17. 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)

  18. Numerical Simulation of Atmosphere-Ocean-Sea Ice Interaction During Interannual Cycle in High Northern Latitudes