西南地区降水日变化特征分析

Analysis on Diurnal Variation of Precipitation in Southwest China

利用1960-2000年西南地区包括(川、渝、黔、滇四省(市))91个气象站的小时降水量自动记录信息化资料,计算和分析了西南地区过去40年间逐月逐日逐时的降水频率和降水比率。结果表明,西南地区各地各季逐时降水最大频率出现的时间较为分散,但四川、重庆和贵州部分地区夜雨频繁,而云南的降水则以白天降水为主;西南地区逐时降水相对集中出现在某个时段的特点较为明显,尤其是夏季,这与西南地区夏季多短时强对流天气有关;重庆的降水在秋、冬、春三季多发生于凌晨到中午以前,但在夏季,除了凌晨到中午降水较为集中和东南部在午后降水也较为集中外,在傍晚到午夜以前降水也较多。

Based on the hourly precipitation data of 91 weather stations in Southwest China from 1960 to 2000,the hourly precipitation frequencies and amount ratios in each month over 40 years in southwest China are investigated.The results indicated that the maximum frequency of hourly precipitation is different in various areas and seasons.In contrast with Yunnan′s daytime rainfall in different seasons,the rainfall of Sichuan,Chongqing and part of Guizhou tend to reach the high frequency in the nighttime.In southwest region,the daily precipitation is unevenly distributed with time.During summer,however,precipitation in each climate area concentrates in a short time.The possible reason for this phenomenon is that severe convective frequently occur in southwest China during summer.