华北雨季不同时段严重旱涝特征的诊断研究

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、４～８月）进行了Ｚ指数计算，确定了干旱则主要发生在８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

Diagnostic analysis of serious flood and drought features fore very months in rainy season in the North China

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.