强热带风暴"碧利斯"造成异常强降水的气候背景

利用大气环流特征量和NCEP/NCAR再分析资料,分析了强热带风暴"碧利斯"造成异常强降水的气候背景。结果表明,冬春季节西太平洋暖池海温偏高时,夏季副热带高压脊线活动偏北,影响中国的热带气旋个数偏多,2006年冬春季海温分布及夏季副高活动形势有利热带气旋影响中国。强热带风暴"碧利斯"登陆和西行时,大气环流高层辐散、低层辐合和热带辐合带的位置偏北、西南暖湿气流在华南有强的辐合等均有利中国南部地区气流辐合上升,使"碧利斯"登陆后低压环流仍能长时间维持,从而造成异常强降水。

Climatic Background of Heavy Rainfall Anormalies Caused by the Severe Tropical Storm "Bilis"

Based on the 74 circulation characteristics from the National Climate Centre of China and NCEP/NCAR reanalysis data, the climatic background of heavy rainfall anormalies caused by the severe tropical storm ( STS ) "Bilis" is analyzed. The results show that when the tropical western Pacific is in a warming state in winter and spring, the western Pacific subtropical high shifts northward, and then the number of tropical cyclones ( TCs ) affecting China is more than the normal level. In 2006, the warmer sea surface temperature in winter and spring and northern subtropical high in summer are all beneficial to TCs influencing China frequently. During the STS "Bilis" landing Fujian Province and moving westerly, circulation convergence and vertical motion strengthening in south China are closely related to the following factors: a) the high-level divergence and low-level convergence are intensifying, b) the intertropical convergence zone (ITCZ) is northward than the normal level, c)the strong convergence of the south-west warm-wet flow occurs in south China. All of these factors led to the STS circulation lasting out for a long time after "Bilis" landing and reinforced heavy rainfall anormalies.