华北雨季不同时段严重旱涝特征的诊断研究

Diagnostic analysis of serious flood and drought features for every months in rainy season in the North China

利用华北平原地区的１３个站点、４５年（１９５１～１９９５）的降水资料。对夏季４个时段（６月、７月、８ 月、６～８月）进行了Ｚ指数计算，确定了该地区各个时段的严重涝年和严重旱年。发现华北地区雨季 的严重洪涝主要集中在７，８月，严重干旱则主要发生在吕月，并可明显看出由５０－６０年代的多水 期向７０年代中期以后的少水期的转变．另外，乌拉尔山到巴尔喀什湖附近的低压槽加深和西北太平 洋副热带高压的北抬，对华北地区雨季持续性暴雨的产生起着决定性的作用．严重洪涝年的夏季 （６～８月），西北太平洋副热带高压偏西、偏北，赤道东太平洋海温多处于下降阶段；严重干旱年西 北太平洋副高偏东、偏南，赤道东太平洋海温则处于上升阶段。

Monthly rainfall data from 1951 to 1995 for June, July and August in 13 meteorological stations of the North China were used for accounting Z index and discussing serious flood and drought featureas in these months. Serious flood mainly happened in July and August, and sevious drought mainly happened in August. There were more flood in1950's to 1960's and more drought since 1970's in the North China. Meanwhile, the deeper trough which covered the regions from the Ural Mis. to the Balkhash Lake play an important role in serious rainstom in rainy season in the North China. There often happened serious flood(drought) when the Northwester Pacific subtropical high was by west and north (east and south), and the Sea Surface Temperature in the equatorial central and eastern Pacific was mainly in dropping(raising) stage.