华北平原地区夏季严重旱涝特征诊断分析

利用华北平原地区13个站1951～1995年6～8月的降水量资料讨论了该地区发生的严重旱涝特征，发现各有7年出现严重干旱和雨涝。严重干旱主要发生在6、7月份，严重雨涝主要发生在7、8月份。特大旱涝发生最频繁的地带在燕山南麓和太行山东麓。50年代多雨涝，60～80年代多干旱，进入90年代雨涝增多，反映华北平原地区旱涝变化阶段性和群发性。东西伯利亚（或鄂霍茨克海）阻塞高压及亚洲中高纬度东高西低分布的稳定维持，则分别对华北平原的严重干旱与雨涝的形成起着重要的作用。西太平洋副热带高压位置偏北、偏西（偏南、偏东），华北平原地区易发生严重雨涝（干旱）。夏季风偏强（弱）年份，华北平原多发生雨涝（干旱）。 在赤道中东太平洋海温与北太平洋西风漂流区海温处于明显正距平阶段，华北平原地区易分别发生严重干旱与雨涝。

A Diagnostic Analyses of Serious Flood/Drought during Summer Season in the North China Plane

Monthly rainfall data of June-August of 1951 to 1995 from 13 meteorological stations of the North China Plane are used for discussing serious flood and drought features. There are seven serious floods and droughts in the last 45 years, respectively. Serious droughts and floods mainly happened from June to July and from July to August, respectively. The most serious drought and flood frequently happened at the southern foot of the Yanshan Mountain and the eastern foot of the Taihang mountain. There were more floods during the 1950s and more droughts from the 1960s to 1980s and increasing floods during the 1990s in the North China Plane. The stable sustenances of blocking high over the East Siberia (or the Okhotsk Sea), and distribution of Ural trough and Baikal ridge plays a very important role in the serious drought and flood formation in the North China Plane, respectively. When location of the western Pacific subtropical high is to the north and west (south and east) as compared with the normal, serious floods (droughts) happened often. When summer monsoon intensity is weak (strong), drought (flood) frequently happen in the North China Plane. During SST raise stage in the equatorial central and eastern Pacific and North Pacific westerly drift region, serious droughts and floods easily happen in the North China Plane, respectively.