2008年1月我国严重低温雨雪冰冻灾害与东亚季风系统异常的关系

Severe Disaster of Blizzard,Freezing Rain and Low Temperature in January 2008 in China and Its Association with the Anomalies of East Asian Monsoon System

鉴于2008年1月我国低温雨雪冰冻灾害所造成的经济损失的严重性,作者从东亚季风系统有关成员的异常来探讨此灾害的发生成因。分析结果表明,2008年1月在中高纬度乌拉尔地区阻塞高压异常发展和长时间的维持及东亚大槽位置的长时间的稳定,这使得异常强冷空气不断沿蒙古高原东侧南下入侵我国华中、华东和华南地区;而西太平洋副热带高压异常偏北,大量暖湿空气沿副高西侧北上,并与南下冷空气在长江流域相遇,从而导致我国长时间的低温雨雪冰冻天气。进一步的分析结果表明,利用在热带中、东太平洋的LaNi a事件对我国冬季气候异常的影响并不能很好地说明此次灾害的发生,而利用热带西太平洋和西北大西洋海温异常对中高纬度和副热带地区大气环流异常的影响可以较好地说明这次灾害的发生成因。此外,2007年冬季北半球准定常行星波向低纬度地区上空对流层上层传播的加强和平流层极涡的下传也可能是2008年1月我国低温雨雪冰冻灾害的重要原因之一。

Due to the severity of the economic losses caused by the blizzard,freezing rain and low temperature occurred in China in January 2008,the causes and mechanism of this disaster are studied using the NCEP/NCAR reanalysis and station observational datasets in China.The authors analyzed the anomalies which are associated to the components of the East Asian monsoon system.The results show that the development and maintenance of the Ural Blocking High over the Ural area in mid and high latitudes for anomalously long time caused the East Asian trough to stay in a stable state,which led to the continuous southward intrusion of cold air along the Mongolian Plateau to Central China,East China and South China.Meanwhile,the western Pacific Subtropical High shifted further northward and westward,which led to the northward transports of a large amount of wet air along the west edge of the Subtropical High from the Bay of Bengal and the convergence with cold air in the Yangtze River valley.The above circulation configuration led to the prolonged occurrence of heavy snowfall and low temperature.Moreover,the results further show that the occurrence of this disaster can not be explained well by the influence of the La Nia event on wintertime climate anomalies in China.The sea surface temperature anomalies（SSTA） in the tropical western Pacific and Northwest Atlantic Ocean are important because of their influences on the Ural Blocking High and the position of western Pacific Subtropical High,respectively.Besides,we discussed the influence of quasi-stationary planetary wave activities,which shows intensification of propagation from mid and high latitudes toward the upper troposphere over low latitudes of the Northern Hemisphere.The influence from the stratospheric circulation,which is presented by downward propagation of strong stratospheric polar vortex,may also add to the circulation anomalies in East Asia.