华南初夏干旱及多雨年份的季风环流特征

本文根据1961—1980年我国华南5月降水量资料,划分5月的旱或涝。并挑选1963、1966(干旱)1973、1975(涝)四年作为典型年,从天气气候角度分析了初夏季风环流结构与华南5月旱涝关系。华南地区旱5月和涝5月在夏季风来临早迟、持续期长短、强度强弱等方面都有明显差异。华南5月出现旱或涝,不仅在同期全球环流,而且在前期环流,特别是北半球中高纬度几个活动中心也有明显的差异。1月以阿留申低压及冰岛低压,4月以太平洋高压及大西洋高压差别比较明显。华南5月降水量的多少与前期3月低纬气压指标值有较好关系,涝 

THE CHARACTERISTIC OF MONSOON CIRCULATION DURING DROUGHT OR FLOOD EARLY SUMMER OVER SOUTH CHINA

In this paper, the drought or flood early summer over South China is defined based on monthly rainfall of May, 1961-1980. The relationship among those two extreme periods and the structure of monsoon circulation is analysed from the viewpoint of synoptic climatology by seclecting 1963, 1966 (drought), 1973, 1975 (flood) as examples. The main results are as follows:1.The differences in the time of onset, maintenance, and strength of summer monsoon are obvious during drought or flood May over South China;2.There is also obvious contrariety in the global circulation, especially of the active centres in high and middle latitudes prior to drought or flood may over South China, of which the differences are more attractive on Aleutian low and Iceland low in January and on Pacific high and Atlantic high in April;3.The rainfall of May over South China is closely associated with the low lititude pressure index in March, when the pressure index is above the normal, the rainfall usually is more, when the pressure index is below the normal the rainfall is less.