青藏高原东北侧夏季干旱的气象成因和长期预报研究

Meteorological Causes for Summer Drought in the North-East Side of the Tibet Plateau and its Long-Range Forecast Research

本文利用近40年(1950～1988年)的北太平洋月平均海温(SST)场、逐月南方涛动指数(SOI)和北半球100hPa月平均高度场,探讨影响黄土高原夏季干旱的信息区及其在时空上的遥相联系,发现热带地区(尤其是低纬地区)的SST和低层环流系统(如SO)的强弱变化与西北夏季干早存在较好的遥相关,这种相关反映在前期各信息区内主要存在半年左右的时滞相关。又从能量频散角度讨论黑潮区SST变化与影响西北夏季干旱环流系统(南亚高压)之间的可能联系。结果得出对中国西北夏季干旱的长期预报,除应按常规注意中高纬度大气环流的变异外,还需要重视前期(冬末春初)热带地区SST与南方涛动的变异。

By using the 40 years (1950-1988) data of the monthly sea surface temperature (SST) of north Pacific ocean, monthly south oscillation index (SOI) and 100hPa monthly mean height in the north hemisphere, the influence of them on the summer drought of loess plateau and the information areas of teleconnection are investigated in this paper. The results show as follows: In tropic regions (especially in low latitude regions), there were high teleconnections between the variations of strength of the SST and the summer drought of the north-west part of China and there existed a time-lag relation for about a half year in various information areas. Also, the influence of SST variation in Kuroshio area on the circulation system (south Asia high) of summer drought of the north-west part of China are discussed by the view of energy frequency diffusion. The results indicate that for seasonal forecast of summer drought of the north-west part of China, the SST variatons of the tropic region and south oscillation in late winter and early spring are previous period needs and attach great importance, exclusive of considering the variations of atmosphere circulation of the high and middle latitudes as a rule.