利用中国站点降水和气温资料、NCEP/NCAR大气再分析资料和海温数据,总结了2021年春季(3—5月)我国气候异常特征,并初步分析了其可能成因。2021年春季全国平均气温为11.6℃,为1961年以来第四暖,但4月我国中部地区出现阶段性气温偏低;全...利用中国站点降水和气温资料、NCEP/NCAR大气再分析资料和海温数据,总结了2021年春季(3—5月)我国气候异常特征,并初步分析了其可能成因。2021年春季全国平均气温为11.6℃,为1961年以来第四暖,但4月我国中部地区出现阶段性气温偏低;全国平均降水量为145.3 mm,接近常年同期,但季内阶段性变化显著,这与环流的阶段性调整密切相关。3—4月亚洲中纬度环流为“东高西低”型,副热带高压偏弱偏东,有利于来自西北太平洋的水汽向长江以北输送,降水呈“北多南少”分布。5月中纬度环流转变为“东低西高”型,副热带高压西伸北扩,低层西南暖湿气流增强,在江南、华南强烈辐合上升,为强对流天气的频繁发生提供了有利条件,降水调整为“南多北少”分布。此外4月中旬开始,中高纬阻塞活动逐渐频繁,一方面导致我国中部地区气温阶段性偏低,另一方面也是造成南方强对流天气发生的重要因素之一。春季后期环流出现明显调整与高低纬度环流相互作用及热带海温的演变有关。4月中旬北极圈大气明显回暖,乌拉尔山高压脊增强,进而造成上述“东低西高”型环流异常;同时,随着5月热带印度洋的快速增暖,前期表现为对La Ni a事件响应的东亚低纬度环流形势也出现明显调整,从而导致季内降水分布也发生了明显变化。展开更多
During the past decades, concurrent with global warming, most of global oceans, particularly the tropical Indian Ocean, have become warmer. Meanwhile, the Southern Hemispheric stratospheric polar vortex (SPV) exhibits...During the past decades, concurrent with global warming, most of global oceans, particularly the tropical Indian Ocean, have become warmer. Meanwhile, the Southern Hemispheric stratospheric polar vortex (SPV) exhibits a deepening trend. Although previous modeling studies reveal that radiative cooling effect of ozone depletion plays a dominant role in causing the deepening of SPV, the simulated ozone-depletion-induced SPV deepening is stronger than the observed. This suggests that there must be other factors canceling a fraction of the influence of the ozone depletion. Whether the tropical Indian Ocean warming (IOW) is such a factor is unclear. This issue is addressed by conducting ensemble atmospheric general circulation model (AGCM) experiments. And one idealized IOW with the amplitude as the observed is prescribed to force four AGCMs. The results show that the IOW tends to warm the southern polar stratosphere, and thus weakens SPV in austral spring to summer. Hence, it offsets a fraction of the effect of the ozone depletion. This implies that global warming will favor ozone recovery, since a warmer southern polar stratosphere is un-beneficial for the formation of polar stratospheric clouds (PSCs), which is a key factor to ozone depletion chemical reactions.展开更多
文摘利用中国站点降水和气温资料、NCEP/NCAR大气再分析资料和海温数据,总结了2021年春季(3—5月)我国气候异常特征,并初步分析了其可能成因。2021年春季全国平均气温为11.6℃,为1961年以来第四暖,但4月我国中部地区出现阶段性气温偏低;全国平均降水量为145.3 mm,接近常年同期,但季内阶段性变化显著,这与环流的阶段性调整密切相关。3—4月亚洲中纬度环流为“东高西低”型,副热带高压偏弱偏东,有利于来自西北太平洋的水汽向长江以北输送,降水呈“北多南少”分布。5月中纬度环流转变为“东低西高”型,副热带高压西伸北扩,低层西南暖湿气流增强,在江南、华南强烈辐合上升,为强对流天气的频繁发生提供了有利条件,降水调整为“南多北少”分布。此外4月中旬开始,中高纬阻塞活动逐渐频繁,一方面导致我国中部地区气温阶段性偏低,另一方面也是造成南方强对流天气发生的重要因素之一。春季后期环流出现明显调整与高低纬度环流相互作用及热带海温的演变有关。4月中旬北极圈大气明显回暖,乌拉尔山高压脊增强,进而造成上述“东低西高”型环流异常;同时,随着5月热带印度洋的快速增暖,前期表现为对La Ni a事件响应的东亚低纬度环流形势也出现明显调整,从而导致季内降水分布也发生了明显变化。
基金Supported by National Natural Science Foundation of China (Grant Nos. 40775053 and 90711004)National Basic Research Program of China (Grant No. 2009CB421401)Innovation Key Program of Chinese Academy of Sciences (Grant Nos. KZCXZ-YW-Q11-03, KZCZ2-YW-Q03-08)
文摘During the past decades, concurrent with global warming, most of global oceans, particularly the tropical Indian Ocean, have become warmer. Meanwhile, the Southern Hemispheric stratospheric polar vortex (SPV) exhibits a deepening trend. Although previous modeling studies reveal that radiative cooling effect of ozone depletion plays a dominant role in causing the deepening of SPV, the simulated ozone-depletion-induced SPV deepening is stronger than the observed. This suggests that there must be other factors canceling a fraction of the influence of the ozone depletion. Whether the tropical Indian Ocean warming (IOW) is such a factor is unclear. This issue is addressed by conducting ensemble atmospheric general circulation model (AGCM) experiments. And one idealized IOW with the amplitude as the observed is prescribed to force four AGCMs. The results show that the IOW tends to warm the southern polar stratosphere, and thus weakens SPV in austral spring to summer. Hence, it offsets a fraction of the effect of the ozone depletion. This implies that global warming will favor ozone recovery, since a warmer southern polar stratosphere is un-beneficial for the formation of polar stratospheric clouds (PSCs), which is a key factor to ozone depletion chemical reactions.
