【摘要】 2006年夏季,四川、重庆发生了50年一遇的高温大旱。利用中国730站中川渝地区58个测站2006年1月1日~9月8日的逐日降水、日最高气温和NCEP再分析资料,探讨了这次高温干旱的特征及成因机理,重点分析了西太平洋副热带高压和大陆副热带高压的异常活动以及西风带与热带环流的特征。研究指出,东亚西风带扰动偏弱、偏北,青藏高原低涡活动减弱,使得川渝地区上空长时间受强大的副热带高压控制;2006年夏季副热带高压的加强和维持与菲律宾以东洋面及南海地区的对流加强、孟加拉湾地区降水异常增多导致的加热场异常密切相关。更多还原

【Abstract】 During July to September in 2006,the Sichuan-Chongqing region of southwestern China suffered from a severe drought and heat wave,which were record-breaking in the past 50 years.This study focuses on the related characteristics and possible causes of the severe drought and heat wave.The abnormal summer climate of the Sichuan-Chongqing region directly caused by the long-term maintenance of a subtropical high pressure belt aloft in the middle and upper troposphere,whose axis was situated along 30°N.The amplifications of western Pacific subtropical high(WPSH) and Tibetan high in a wide meridional extent both contributed to the formation of such a unified subtropical high pressure belt.Specifically, the Tibetan high extended eastward,with its center still located in the Iran Plateau,giving rise to the amplification and westward extension of the WPSH.As a result,both the Tibetan high in the upper troposphere and the WPSH in the middle troposphere mer ged into one subtropical high pressure belt.Meanwhile,the mid-latitude westerlies as well as the accompanying transient disturbances shifted poleward from their climatological position,which is favorable to the maintenance of subtropical high pressure system over the Sichuan-Chongqing region.The lower tropospheric vortex originated from the eastern slope of the Tibetan Plateau,which is also called southwestern vortex and a major rain-producing weather system locally,was weaker in this summer than normal.In the tropics,the abnormal condensational latent heat releases over the western Pacific Intertropical Convergence Zone(ITCZ) and the Bay of Bengal possibly contributed to the maintenance of subtropical high pressure system over the Sichuan-Chongqing region.更多还原