西南地区云水量与可降水量比值的分布特征和变化趋势

采用1980～2009年云水量和可降水量的NCEP逐月再分析资料，通过统计分析，研究30a来西南地区（云南、贵州、讴庆、四川）云水量与可降水量比值的时空分布特征和变化趋势。结果表明：（1）西南地区年、季17孟水量与可降水比值均具有明显的地区性差异，由西北向东南递减，高值区位于川西高原；（2）云水量与可降水比值年内分布不均匀，从2月到8月逐渐减小，9月至1月逐渐增大，同时，季节差异较大，夏季最小，冬季最大；（3）30a来，整个西南地区年、夏季和秋季云水量与可降水量比值呈显著减少趋势。

Trend and Distribution Features of Ratio of Cloud Water to Precipitable Water in Southwest China

Based on NCEP monthly cloud water and precipitable water data from 1980 to 2009, the spatial and temporal distribution characteristic and variation trend of ratio of cloud water to precipitable water in southwest China were analyzed in this paper. The results show that the annual and seasonal ratio of cloud water to precipitable water in southwest China had obvious regional difference, which decreased from northwest to southeast, and the high value was located in Western Sichuan Plateau. Ratio of cloud water to precipitable water decreased from February to August, and increased from September to January in a year, and the ratio was minimum in summer and maximum in winter. There was a clear downward trend for annual ratio of cloud water to preeipitable water in 30 years, and the ra- tio also decreased in summer and autumn.