西北地区不同类型云的时空分布及其与降水的关系

TEMPORAL AND SPATIAL DISTRIBUTION OF THE DIFFERENT CLOUDS OVER NORTHWESTERN CHINA WITH THE RELATION TO PRECIPITATION

利用1983年7月～2001年9月国际卫星云气候计划ISCCP D2的月平均资料,对西北不同区域不同类型云的云量和云水路径的时空分布及其与降水的关系进行了研究.结果表明:高原气候区是各种云出现最多的地区,特别是积状云的云量明显高于其他两区,但这些云的云水路径值低;西北地区大多数云云量的高值区出现在天山山区、北疆地区、陕西东南部和青藏高原的部分地区.高云和部分中云云量空间分布特征与降水有着较好的一致性:沿着天山-昆仑山-祁连山一带以及陕南和/或陇南地区是高值区,低值区在塔里木盆地-内蒙古西部戈壁沙漠-黄土高原西北部一带;绝大多数云类春夏季节云量维持较高,秋冬季节云量较少.云水路径值较大的层状云类的云量多寡与降水多寡相一致;积状云类和层积云类云量多少与降水没有一定的关系,在降水偏少时,这类云的云量大多与降水正常时相近,有些云的云量甚至比降水偏多时还要多.

The temporal and spatial characteristics of the different clouds and the relation to precipitation over Northwest China are analyzed using the ISCCP （International Satellite Cloud Climatology Project）monthly mean D2 data from July 1983 to September 2001. Northwestern China is divided into three climatic regions for the purpose of this study. The results show that the plateau climatic region is the one with highest cumuliform cloud amount with low values of liquid water path. The higher cloud amount value areas for most types, especially for high cloud, are over Tianshan Mountains, Kunlun Mountains, Qilian Mountains, and southern Shaanxi and/or southern Gansu, while the lower values of cloud amounts are located over Tarim Basin, the western desert of Inner Mongolia and the northwestern part of Loess Plateau. Also, cloud amount levels are consistent with levels of precipitation. In general, cloud amounts are higher in spring and summer while lower in autumn and winter. The amounts of stratiform clouds associated with higher liquid water path are consistent with precipitation. The amounts of cumuliform and stratocumuliform clouds, however, do not have definite relation to precipitation.