Three striking and impactful extreme cold weather events successively occurred across East Asia and North America during the mid-winter of 2020/21.These events open a new window to detect possible underlying physical ...Three striking and impactful extreme cold weather events successively occurred across East Asia and North America during the mid-winter of 2020/21.These events open a new window to detect possible underlying physical processes.The analysis here indicates that the occurrences of the three events resulted from integrated effects of a concurrence of anomalous thermal conditions in three oceans and interactive Arctic-lower latitude atmospheric circulation processes,which were linked and influenced by one major sudden stratospheric warming(SSW).The North Atlantic warm blob initiated an increased poleward transient eddy heat flux,reducing the Barents-Kara seas sea ice over a warmed ocean and disrupting the stratospheric polar vortex(SPV)to induce the major SSW.The Rossby wave trains excited by the North Atlantic warm blob and the tropical Pacific La Nina interacted with the Arctic tropospheric circulation anomalies or the tropospheric polar vortex to provide dynamic settings,steering cold polar air outbreaks.The long memory of the retreated sea ice with the underlying warm ocean and the amplified tropospheric blocking highs from the midlatitudes to the Arctic intermittently fueled the increased transient eddy heat flux to sustain the SSW over a long time period.The displaced or split SPV centers associated with the SSW played crucial roles in substantially intensifying the tropospheric circulation anomalies and moving the jet stream to the far south to cause cold air outbreaks to a rarely observed extreme state.The results have significant implications for increasing prediction skill and improving policy decision making to enhance resilience in“One Health,One Future”.展开更多
Climate and forecast mode simulations with the regional climate model HIRlam-ECHAM(HIRHAM) are evaluated over a pan-Antarctic domain. The ability of the model to simulate temperature and wind profiles in the troposp...Climate and forecast mode simulations with the regional climate model HIRlam-ECHAM(HIRHAM) are evaluated over a pan-Antarctic domain. The ability of the model to simulate temperature and wind profiles in the troposphere is quantified by comparing its results with radiosonde data acquired from the Davis station for January and July 2007. Compared to the climate mode, the forecast mode was found to deliver improved results for temperature and wind simulations at the near surface and in the lower troposphere. The main remaining model bias found was the under-representation of low-level wind jets. Based on ensemble simulations, it is shown that a distinct internal variability is inherent in the climate mode simulations, and associated areas of reduced predictability over Antarctica are identified.展开更多
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 f...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℃--16℃ in winter and the seasonal sea ice cycle and sea ice concentration are significantly 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 Pacific 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 intensification of the jet stream over East Asia and the north Pacific in winter.展开更多
The temperature, humidity, and vertical distribution of ozone in the Antarctic atmospheric boundary layer(ABL) and their seasonal changes are analyzed, by using the high-resolution profile data obtained during the I...The temperature, humidity, and vertical distribution of ozone in the Antarctic atmospheric boundary layer(ABL) and their seasonal changes are analyzed, by using the high-resolution profile data obtained during the International Polar Year 2008 to 2009 at Zhongshan Station, to further the understanding of the structure and processes of the ABL. The results show that the fre- quency of the convective boundary layer in the warm season accounts for 84% of its annual occurrence frequency. The frequency of the stable boundary layer in the cold season accounts for 71% of its annual occurrence frequency. A neutral boundary layer ap- pears rarely. The average altitude of the convective boundary layer determined by the parcel method is 600 m; this is 200 to 300 m higher than that over inland Antarctica. The average altitude of the top of the boundary layer determined by the potential tempera- ture gradient and humidity gradient is 1 200 m in the warm season and 1 500 m in the cold season. The vertical structures of ozone and specific humidity in the ABL exhibit obvious seasonal changes. The specific humidity is very high with greater vertical gradi- ent in the warm season and very low with a lesser gradient in the cold season under 2 000 m. The atmospheric ozone in the ABL is consumed by photochemical processes in the warm season, which results in a slight difference in altitude. The sub-highest ozone center is located in the boundary layer, indicating that the ozone transferred from the stratosphere to the troposphere reaches the low boundary layer during October and November in Antarctica.展开更多
Ensemble simulations with the Arctic coupled regional climate model HIRHAM-NAOSIM have been analyzed to investigate atmospheric feedbacks to September sea-ice anomalies in the Arctic in autumn and the following winter...Ensemble simulations with the Arctic coupled regional climate model HIRHAM-NAOSIM have been analyzed to investigate atmospheric feedbacks to September sea-ice anomalies in the Arctic in autumn and the following winter. Different "low- minus high ice" composites have been calculated using selected model runs and different periods. This approach allows us to investigate the robustness of the simulated regional atmospheric feedbacks to detected sea-ice anomalies. Since the position and strength of the September sea-ice anomaly varies between the different "low- minus high ice" composites, the related simulated atmospheric patterns in autumn differ depending on the specific surface heat flux forcing through the oceaaa-atmosphere interface. However, irrespective of those autumn differences, the regional atmospheric feedback in the following winter is rather insensitive to the applied compositing. Neither the selection of simulations nor the considered period impacts the results. The simulated consistent large-scale atmospheric circulation pattern show-s a wave-like pattern with positive pressure anomaly over the region of the Barents/Kara Seas and Scandinavia/western Russia ("Scandinavian-Ural blocking") and negative pressure anomaly over the East Siberian/Laptev Seas.展开更多
Polar climate systems have experienced a number of dramatic changes (Wang et al., 2017; Turner et al., 2016; Gordon, 2014; Rignot et al., 2013; Meier et al., 2012; Kwok and Rothrock, 2009; Thompson and Solomon, 2002...Polar climate systems have experienced a number of dramatic changes (Wang et al., 2017; Turner et al., 2016; Gordon, 2014; Rignot et al., 2013; Meier et al., 2012; Kwok and Rothrock, 2009; Thompson and Solomon, 2002), which have influenced climatic conditions across large parts of the globe through large-scale atmospheric and oceanic teleconnections (Dou and Wu, 2018; Zhang et al., 2018;展开更多
The climates of the polar regions axe important components of the global Earth system and have experienced dramatic changes in recent decades. These changes and their possible influences on and feedback with processes...The climates of the polar regions axe important components of the global Earth system and have experienced dramatic changes in recent decades. These changes and their possible influences on and feedback with processes across the rest of the globe have raised great research challenges regarding the processes involved. In addition, the polar regions have been the least observed and understood regions. To improve our understanding and prediction of polar climate changes, and associated extreme events and global impacts, a number of international initiatives for polar climate research, such as Year of Polar Prediction (YOPP) and the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAIC), have been planned and implemented.展开更多
The European Centre for Medium-Range Weather Forecasts Reanalysis ERA40,National Centers for Environmental Prediction(NCEP) 20th-century reanalysis,and three station observations along an Antarctic traverse from Zhong...The European Centre for Medium-Range Weather Forecasts Reanalysis ERA40,National Centers for Environmental Prediction(NCEP) 20th-century reanalysis,and three station observations along an Antarctic traverse from Zhongshan to Dome-A stations are used to assess 2-m temperature simulation skill of a regional climate model.This model(HIRHAM) is from the Alfred Wegener Institute for Polar and Marine Research in Germany.Results show:(1) The simulated multiyear averaged 2-m temperature field pattern is close to that of ERA40 and NCEP;(2) the cold bias relative to ERA40 over all of Antarctic regions is 1.8℃,and that to NCEP reaches 5.1℃;(3) bias of HIRHAM relative to ERA40 has seasonal variation,with a cold bias mainly in the summer,as much as 3.4℃.There is a small inland warm bias in autumn of 0.3℃.Further analysis reveals that the reason for the cold bias of 2-m temperature is that physical conditions of the near-surface boundary layer simulated by HIRHAM are different from observations:(1) During the summer,observations show that near-surface atmospheric stability conditions have both inversions and non-inversions,which is due to the existence of both positive and negative sensible heat fluxes,but HIRHAM almost always simulates a situation of inversion and negative sensible heat flux;(2) during autumn and winter,observed near-surface stability is almost always that of inversions,consistent with HIRHAM simulations.This partially explains the small bias during autumn and winter.展开更多
基金supported by the U.S. Department of Energy (Grant No. DE-SC0020640)the National Natural Science Foundation of China (Grant Nos. 41675041 and 41790475)+6 种基金the Arctic Research Program of the NOAA Global Ocean Monitoring and Observing Officethe Deutsche Forschungsgemeinschaft (project 268020496 TRR 172 within the Transregional Collaborative Research Center “Arcti C Amplification:Climate Relevant Atmospheric and Surfa Ce Processesand Feedback Mechanisms (AC)3”)the Academy of Finland (contract 317999)the Cooperative Institute for ClimateOcean&Ecosystem Studies (CIOCES) under NOAA Cooperative Agreement NA20OAR4320271.
文摘Three striking and impactful extreme cold weather events successively occurred across East Asia and North America during the mid-winter of 2020/21.These events open a new window to detect possible underlying physical processes.The analysis here indicates that the occurrences of the three events resulted from integrated effects of a concurrence of anomalous thermal conditions in three oceans and interactive Arctic-lower latitude atmospheric circulation processes,which were linked and influenced by one major sudden stratospheric warming(SSW).The North Atlantic warm blob initiated an increased poleward transient eddy heat flux,reducing the Barents-Kara seas sea ice over a warmed ocean and disrupting the stratospheric polar vortex(SPV)to induce the major SSW.The Rossby wave trains excited by the North Atlantic warm blob and the tropical Pacific La Nina interacted with the Arctic tropospheric circulation anomalies or the tropospheric polar vortex to provide dynamic settings,steering cold polar air outbreaks.The long memory of the retreated sea ice with the underlying warm ocean and the amplified tropospheric blocking highs from the midlatitudes to the Arctic intermittently fueled the increased transient eddy heat flux to sustain the SSW over a long time period.The displaced or split SPV centers associated with the SSW played crucial roles in substantially intensifying the tropospheric circulation anomalies and moving the jet stream to the far south to cause cold air outbreaks to a rarely observed extreme state.The results have significant implications for increasing prediction skill and improving policy decision making to enhance resilience in“One Health,One Future”.
基金funded by the National Natural Science Foundation of China under Grant No.40905048the German Bosch Foundation,and the program of basic research and operating of CAMS
文摘Climate and forecast mode simulations with the regional climate model HIRlam-ECHAM(HIRHAM) are evaluated over a pan-Antarctic domain. The ability of the model to simulate temperature and wind profiles in the troposphere is quantified by comparing its results with radiosonde data acquired from the Davis station for January and July 2007. Compared to the climate mode, the forecast mode was found to deliver improved results for temperature and wind simulations at the near surface and in the lower troposphere. The main remaining model bias found was the under-representation of low-level wind jets. Based on ensemble simulations, it is shown that a distinct internal variability is inherent in the climate mode simulations, and associated areas of reduced predictability over Antarctica are identified.
基金supported by the National Basic Research Development Program of China (Grant no.2011CB952001)
文摘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℃--16℃ in winter and the seasonal sea ice cycle and sea ice concentration are significantly 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 Pacific 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 intensification of the jet stream over East Asia and the north Pacific in winter.
基金supported by the Chinese Polar Environment Comprehensive Investigation & Assessment Programmes(2011-2015)
文摘The temperature, humidity, and vertical distribution of ozone in the Antarctic atmospheric boundary layer(ABL) and their seasonal changes are analyzed, by using the high-resolution profile data obtained during the International Polar Year 2008 to 2009 at Zhongshan Station, to further the understanding of the structure and processes of the ABL. The results show that the fre- quency of the convective boundary layer in the warm season accounts for 84% of its annual occurrence frequency. The frequency of the stable boundary layer in the cold season accounts for 71% of its annual occurrence frequency. A neutral boundary layer ap- pears rarely. The average altitude of the convective boundary layer determined by the parcel method is 600 m; this is 200 to 300 m higher than that over inland Antarctica. The average altitude of the top of the boundary layer determined by the potential tempera- ture gradient and humidity gradient is 1 200 m in the warm season and 1 500 m in the cold season. The vertical structures of ozone and specific humidity in the ABL exhibit obvious seasonal changes. The specific humidity is very high with greater vertical gradi- ent in the warm season and very low with a lesser gradient in the cold season under 2 000 m. The atmospheric ozone in the ABL is consumed by photochemical processes in the warm season, which results in a slight difference in altitude. The sub-highest ozone center is located in the boundary layer, indicating that the ozone transferred from the stratosphere to the troposphere reaches the low boundary layer during October and November in Antarctica.
基金supported by the SFB/TR172 “Arctic Amplification:Climate Relevant Atmospheric and Surface Processes,and Feedback Mechanisms (AC)” funded by the Deutsche Forschungsgemeinschaft (DFG)supported by the project QUARCCS “Quantifying Rapid Climate Change in the Arctic:Regional feedbacks and large-scale impacts” funded by the German Federal Ministry for Education and Research (BMBF)
文摘Ensemble simulations with the Arctic coupled regional climate model HIRHAM-NAOSIM have been analyzed to investigate atmospheric feedbacks to September sea-ice anomalies in the Arctic in autumn and the following winter. Different "low- minus high ice" composites have been calculated using selected model runs and different periods. This approach allows us to investigate the robustness of the simulated regional atmospheric feedbacks to detected sea-ice anomalies. Since the position and strength of the September sea-ice anomaly varies between the different "low- minus high ice" composites, the related simulated atmospheric patterns in autumn differ depending on the specific surface heat flux forcing through the oceaaa-atmosphere interface. However, irrespective of those autumn differences, the regional atmospheric feedback in the following winter is rather insensitive to the applied compositing. Neither the selection of simulations nor the considered period impacts the results. The simulated consistent large-scale atmospheric circulation pattern show-s a wave-like pattern with positive pressure anomaly over the region of the Barents/Kara Seas and Scandinavia/western Russia ("Scandinavian-Ural blocking") and negative pressure anomaly over the East Siberian/Laptev Seas.
基金funded by the Fundamental Research Funds for the Central Universities (Grant nos.2017B04814,2017B20714),Hohai UniversityState Key Laboratory of Satellite Ocean Environment Dynamics+1 种基金supported by the Global Change Research Program of China (Grant no.2015CB953904)the National Natural Science Foundation of China (NSFC,Grant no.41876220)
文摘Polar climate systems have experienced a number of dramatic changes (Wang et al., 2017; Turner et al., 2016; Gordon, 2014; Rignot et al., 2013; Meier et al., 2012; Kwok and Rothrock, 2009; Thompson and Solomon, 2002), which have influenced climatic conditions across large parts of the globe through large-scale atmospheric and oceanic teleconnections (Dou and Wu, 2018; Zhang et al., 2018;
文摘The climates of the polar regions axe important components of the global Earth system and have experienced dramatic changes in recent decades. These changes and their possible influences on and feedback with processes across the rest of the globe have raised great research challenges regarding the processes involved. In addition, the polar regions have been the least observed and understood regions. To improve our understanding and prediction of polar climate changes, and associated extreme events and global impacts, a number of international initiatives for polar climate research, such as Year of Polar Prediction (YOPP) and the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAIC), have been planned and implemented.
基金supported by the Program of China Polar Environment Investigation and Assessment(2011–2015)the Basic Scientific Special Project "Climate System Model" of Chinese Academy of Meteorological Science(Grant No.2012Z001)the National Natural Science Foundation of China(Grant Nos.41005045 and 41206179)
文摘The European Centre for Medium-Range Weather Forecasts Reanalysis ERA40,National Centers for Environmental Prediction(NCEP) 20th-century reanalysis,and three station observations along an Antarctic traverse from Zhongshan to Dome-A stations are used to assess 2-m temperature simulation skill of a regional climate model.This model(HIRHAM) is from the Alfred Wegener Institute for Polar and Marine Research in Germany.Results show:(1) The simulated multiyear averaged 2-m temperature field pattern is close to that of ERA40 and NCEP;(2) the cold bias relative to ERA40 over all of Antarctic regions is 1.8℃,and that to NCEP reaches 5.1℃;(3) bias of HIRHAM relative to ERA40 has seasonal variation,with a cold bias mainly in the summer,as much as 3.4℃.There is a small inland warm bias in autumn of 0.3℃.Further analysis reveals that the reason for the cold bias of 2-m temperature is that physical conditions of the near-surface boundary layer simulated by HIRHAM are different from observations:(1) During the summer,observations show that near-surface atmospheric stability conditions have both inversions and non-inversions,which is due to the existence of both positive and negative sensible heat fluxes,but HIRHAM almost always simulates a situation of inversion and negative sensible heat flux;(2) during autumn and winter,observed near-surface stability is almost always that of inversions,consistent with HIRHAM simulations.This partially explains the small bias during autumn and winter.