两次华南持续性暴雨过程中热带西太平洋对流异常作用的比较

利用NOAA的外逸长波辐射资料(OLR)和NCEP/NCAR再分析资料以及华南地区台站降水资料诊断分析了热带西太平洋对流活动在2005年和2006年华南地区持续性暴雨发生的大尺度环流背景上的物理作用.分析表明:2005年6月17～24日华南持续性暴雨过程与热带西太平洋对流的10～25天低频振荡从150 °E附近西传有关,持续性暴雨期间西太平洋副热带高压持续西伸的Gill型环流响应对应于传播到120 °E附近强对流的低频间歇期;2006年5月下旬～6月中旬华南的持续性暴雨可能与热带西太平洋的双热带辐合带(ITCZ)南支对流带异常强盛有关,持续强盛的南支ITCZ使得115～135 °E平均的局地Hadley环流最大上升中心位于0～5 °S,菲律宾海附近区域上升运动的减弱有利于西太平洋副热带高压持续西伸加强.通过比较这两例典型的华南持续性暴雨过程发现,副热带高压在华南地区持续西伸是两次持续性暴雨发生的共同的大尺度环流背景,而热带西太平洋对流活动则通过不同的物理过程影响副热带高压的持续西伸.

COMPARISON OF THE EFFECTS OF ANOMALOUS CONVECTIVE ACTIVITIES IN THE TROPICAL WESTERN PACIFIC ON TWO PERSISTENT HEAVY RAIN EVENTS IN SOUTH CHINA

Based on the NCEP/NCAR reanalysis data,the thermodynamic features and the effect of spatially nonuniform heating on the circulation of the tropical monsoon area in South Asia due to the land-sea distribution are analyzed.The influences of the subcontinent topography on the Asian tropical circulation are mostly characterized by its thermodynamic effects on low-level circulation,of which the strongest is observed in winter and spring but the relatively weak in summer,followed by the weakest in autumn.The thermodynamic difference between the Indochina Peninsula and Indian Peninsula and its influence on the circulation are regulated by the Tibetan Plateau.During the transitional period from spring to early summer,the Tibetan Plateau thermal forcing generates a large-scale cyclonic circulation in low latitudes in the lower troposphere.As a result,the southerlies/northerlies are increased to the east/west of the Bay of Bengal,Therefore latent heating of the atmosphere is strengthened and the surface sensible heating over the Indochina Peninsula is weakened.On the other hand the surface sensible heating over the Indian Peninsula is increased.It is shown that heating with various scales and different kinds can affect the tropical atmosphere in different ways,which lead to the unique characteristics of the tropical Asian circulation.