华南前汛期降水异常及其环流特征分析

ANALYSIS OF PRECIPITATION IN THE ANNUALLY FIRST RAINY PERIOD AND GENERAL CIRCULATION IN THE SOUTH OF CHINA

利用国家气候中心整编的中国160站的月平均降水资料和美国NCEP/NCAR的再分析资料,分析华南前汛期降水的异常及其环流特征。文中取"九五"重中之重项目执行组指出的华南地区的16站来代表华南地区,侧重分析了华南前汛期降水异常的年际、年代际变化特征及华南前汛期多、少雨年同期的环流特征。研究发现:华南地区降水的季节分布呈现双峰型,两个峰值分别在6月和8月。华南前汛期近50年的总的降水趋势变化不明显。1950年代前期和1960年代中期—1980年代中为相对多雨期,而1950年代中期—1960年代中期以及1980年代中期—1990年代初为相对少雨期,1990年代为正常波动期。华南前汛期降水存在3a、5a、7a、14a的周期。在分析华南前汛期多、少雨年大气环流场的特征时发现:华南前汛期多雨年时南亚高压和副高都偏弱,华南地区低层的水汽通量辐合加强,而且低空辐合,高空辐散,气流上升运动加强,容易形成降水;而少雨年的情况恰恰相反。

In this paper, monthly mean precipitation data from 160 stations （selected as represent the south of China） and monthly mean data of NCEP/NCAR during 1951--2000, 16 stations are emphatically studied for the inter-annual and inter-decadal variations of the precipitation in the annually first rainy period and the circulation anomaly between the rainys and droughts in the rainy period in the south of China. It is found that the precipitation in the south of China has two peak values respectively in June and August. The total rainfall tendency has little change. Flood years were in the beginning of 1950s, the middle of 1960s and the beginning of 1980s; drought years were from the middle of 1950s to the middle of 1960s, and from the middle of 1980s to the start of 1990s.The precipitation anomaly has 3-year, 5-year, 7-year and 14-year periodic variation in the annually first rainy period in the South of China. From the research into the circulation anomaly between the flood years and drought years, it is discovered that the South Asia high and subtropical high are both weak and water vapor transport at low-level is convergent and strong, resulting in low-level convergence versus high-level divergence, with strong updraft in the flood years during the rainy period in the South of China. The situation in drought years is opposite to that of rainy years.