夏季西北干旱区干、湿年环流及高原动力影响差异的对比分析

COMPARATIVE ANALYSES OF DIFFERENCES BETWEEN CIRCULATION AND DYNAMICAL EFFECT OF QINGHAI-XIZANG PLATEAU OVER NW CHINA DROUGHT AREA IN DRY- AND WET- SUMMER

为了更深入地分析西北干旱气候形成的原因，并研究各影响因子之间的联系，利用１９７９—１９８６年夏季（６—８月）的ＥＣＭＷＦ的格点资料和我们先前划分的夏季高原北侧地区干、湿等级资料，进一步作了夏季高原北侧地区干、湿年间平均环流和高原动力作用等因子差异的对比分析，也讨论了这些差异对该地区干、湿年形成的贡献。结果指出，由于青藏高原及深居内陆的环境造成了西北干旱背景，而高原的热力、动力作用、环流特征等各因子逐年之间的差异则造成西北干旱区的干、湿年。随之提出了西北干旱区及其干。

To further analyze the forming cause of the drought over the northwest China and to also seek the relation among all the factors which may cause the drought,in this paper,the differences between the circulation and the dynamical influences of the Qinghai-Xizang Plateau on the north side of the Plateau(NSP) in dry- and wet- summer have comparatively been analyzed utilizing the gridded data of ECMWF for June to August of 1979 1986. The contribution of the differences to the dry- or wet-summer climate on NSP has also been discussed in the paper. The main results show that the combined effects of the Plateau thermal and dynamical influences, dominant circulation,as well as the geophysical environment far from the ocean result in the drought background over the northwest China. The year-to-year difference of each factor leads to the dry or wet year in northwest China drought area. The schematic diagram showing how to cause the dry and wet years on the NSP area has,finally,been drawn.