华南4～6月降水异常的环流特征

CIRCULATION FEATURES OF APRIL TO JUNE ABNORMAL PRECIPITATION IN SORTH CHINA

分析了华南４～６月降水量的年际变化特征及华南４～６月旱、涝年的５００ｈＰａ高度距平场的主要差异。结果表明，４～６降水存在２．５～３年的准周期变化和持续１０年左右的阶段性变化特征。旱、涝年１～３月５００ｈＰａ高度距平场的分布基本反位相，４～６月的距平场也存在明显的差异。综合结果表明，从冬季开始到次年６月，旱、涝年５００ｈＰａ高度距平沿５０°Ｎ纬圈的演变具有基本相反的过程。

This paper investigates the interannual variation features of April to June precipitationand main difference in 500hPa height anomaly between drought and flood years in South China。Results show that the rainfall has a quasi periodic(2.5 to 3 year)oscillation and a 10 year or sopersistent variation as an interval feature;in the dry and wet years,the January to March 500 hPaanomaly patterns are basically in anti-phase and the April to June patterns differ widely。Comprehensive analysis indicates that the evolution of 500 hPa height anomaly from winter to the follow-ing June follows a roughly opposite direction along the 50°N parallel in the two types of years。