青藏高原雪盖异常对我国环流和降水的影响

THE INFLUENCE OF THE ABNORMAL SNOW COVER OVER THE QINGHAI-TIBET PLATEAU ON PRECIPETATION

利用美国ＮＯＡＡＮＥＳＤＩＳ提供的１９７５－１９８６年青藏高原地区卫星雪盖资料，作出了各月冬季青藏高原雪盖频率图。发现１－３月是高原雪盖面积最大的月份，在此期间高原雪盖面积有明显的持续性，并与欧亚雪盖面积有较高的一致性。根据３月高原雪盖异常与中国环流和降水的关系，发现高原雪盖异常的后延冷却效应较弱，大约不足一个月；３月高原多雪以后，５月东亚北风加大，南岭以北降水偏少，少雪年则相反。

According to 1975-1986 satellite snow cover data over the Qinghai-Tibet Plateauprovided by NOAA NESDIS,the monthly and seasonal snow cover frequency chartsover the Plateau are made. It is found that the Plateau snow cover areas from January toMarch are the widest in a year.And,during the period they appear to be obvious persis-tence,and there are remrkable relationship between them and Eurasian snow cover ar- eas. In this paper,the influence of abnormal snow cover over the Plateau in March uponthe circulation and precipitation of China are also examined.It is found that the lag timeof direct cooling effect caused by abnormal snow cover over the Plateau is about lessthan one month.When the snow cover areas over the Plateau in March exceed the nor-mal,north wind over East Asia is strengthened and the precipitation north of the Nan-ling Mountains,south of China,is less than the normal in the two subsequent months-May.