前秋雪盖和海温异常对2008年1月南方低温雨雪天气的影响

EFFECTS OF PRECEDING AUTUMN SNOW COVER AND SST ON LARGE-SCALE CIRCULATIONS OF THE FREEZING RAIN AND SNOW STORM OVER SOUTHERN CHINA IN JANUARY 2008

对1973—2008年1月全国160站的温度和降水资料进行联合EOF分析发现,2008年1月低温雨雪天气与第一模态和第三模态有关,两个模态组合能够解释2008年1月南方地区温度和降水异常的90%以上。与第一模态相关的环流场主要反映了西伯利亚高压偏强且位置偏西,其与前秋中亚-蒙古以北的雪盖面积异常偏大以及北太平洋冷海温异常与关。与第三模态相关环流场则主要反映了副热带高压的增强和南支槽的加深,前秋印度洋暖海温异常有利于次年1月副热带高压增强,而前秋北大西洋和黑潮延伸区暖海温异常与次年1月南支槽的加深有关。

Running a joint EOF analysis of the temperature and precipitation data from 160 stations across China for Januaries of 1973-2008 reveals that the first and third EOF mode combined can account for more than 90% of a freezing rain and snow weather in January 2008 in southern China. The first mode, characterized by a westward shift of intensified Siberia High which is the source of cold air, is preceded by excessive autunm （Sept.-Oct.） snow covers and positive sea surface temperature （SST） anomalies over the northern Pacific. The third mode, on the other hand, features a strengthened western Pacific subtropical high （WPSH） and a deepened southern branch trough, which enhances the advection of warm and moist air in the southern China. The positive SST over equatorial Indian Ocean is followed by the enhanced WPSH and the preceding rising SST over the Northern Atlantic and Kuroshio Extension are related with the deepened southern branch trough.