安阳区域性夏季大旱成因分析

Study on the Causes of Summer Heavy Drought over Anyang

利用 195 7～ 1998年安阳区域夏季降水资料 ,确定安阳区域性夏季大旱的标准 ,分析了大旱成因 :东亚沿海低槽较常年异常深厚和偏东以及西太平洋副高异常偏东、偏南和偏弱 ;当年 6～ 8月太阳黑子相对平均数处于谷点或从谷点开始上升时期 ;当年春季出现厄尔尼诺或存在厄尔尼诺现象 ,绝大部分安阳降水偏少或特少 ,出现干旱或大旱 ;6～ 8月西风急流轴异常偏北 ,也是造成安阳区域性夏季大旱的原因之一。

Utilizing the data of summer precipitation from 1957 to 1998, we define the criterion of heavy drought in Anyang area and analyze its causes: (1) the low pressure trough over east Asia coastland is abnormal deeper and easterner as well as the western Pacific subtropical high is abnormal easterner, southerner and weaker; (2)the sunspot relative average reaches bottom or just rises from there in June, July and August; (3)EL Nino appears or exists in the spring and the precipitation is so small that drought or heavy drought occurred in most parts of Anyang; (4)western jet stream is abnormal northerner.