影响华南前汛期降水异常的准双周振荡传播特征

摘要

The relationship between the quasi-biweekly oscillation (QBW:here defined as a 1 0 ~25 day oscillation)abnormity of May-June rainfall over southern China and the QBW propagation from the tropics and mid-latitudes is studied based on the composite analysis.The results indicate distinct QBW propagations in different May-June rainfall abnormal cases.The strong QBW rainfall abnormal cases in May in southern China are linked to the QBW propagations not only from the Bay of Bengal but also from the mid-latitudes of northwestern China.However,the weak QBW rainfall abnormal cases in May are just linked to the QBW propagations from the tropics.In June,the strong and weak QBW rainfall abnormal cases in southern China are influenced by the QBW propagations from the Bay of Bengal and from the mid-latitudes,respectively.%采用合成分析方法，分析了5－6月华南降水准双周振荡（10～25 d 振荡）异常与热带和中纬度准双周振荡传播的联系。结果表明与华南5－6月低频降水异常有密切联系的大气准双周振荡的传播过程是有显著差别的。5月华南准双周低频振荡的强降水过程主要是由孟加拉湾热带低频对流活动的北传、东传和源于中国西北地区南下的低频信号影响而造成的；而弱年则只有热带低频信号的北传及东传的影响。华南6月强的低频降水过程主要是受源于孟加拉湾的热带准双周振荡北传和东传的影响；而华南6月弱的低频降水过程主要受源于中纬度的准双周振荡南传的影响。