中国日降水量小于不同阈值日数时空分布特征

利用中国672个站点1951-2010年的逐日降水资料,系统分析了全国各地日降水量小于0.1mm、1 mm、5mm和10mm不同阈值的日数、平均持续日数、最长持续日数和持续10天以上过程出现频次等要素的时空分布特征,并分别选择齐齐哈尔、乌鲁木齐、北京、昆明、常德、南京、汕头和海口8个代表站点,分析了各变量的历史演变趋势.结果表明,全国日降水量小于0.1mm、1mm、5mm和10mm日数、平均持续日数、平均最长持续日数、极端最长持续日数以及日降水量小于0.1m持续10天以上过程发生频次的时空分布特征基本相似,空间上自西北向东南方向递减,时间上冬、秋季多,春、夏季少,这与我国气候干旱的时空分布特点基本一致；而全国日降水量小于1mm、5mm和10 mm持续10天以上过程出现频次的时空分布特征,与我国实际干旱灾害的发生规律基本一致,高值中心出现在华北、黄淮、江淮、江南等地,发生时间集中在春、夏季.全国主要区域代表站点日降水量小于0.1mm日数、平均持续日数、最长持续日数基本都呈增加趋势,且南方强于北方；日降水量小于1mm、5mm和10 mm日数、平均持续日数和最长持续日数在西部地区,特别是西北地区表现出较为明显的减少趋势,其中乌鲁木齐日降水量小于5mm和10mm平均持续日数线性减少趋势分别达2.0d/10a和7.5d/10a,最长持续日数线性减少趋势分别达9.3d/10a和11.8d/10a,呈现出明显的湿润化趋势.

Spatial and Temporal Distribution of Dry Spells in China

Spatial and temporal distribution and trends of dry days,mean and maximum dry spells,the number of long dry spells(longer than 10 days) which are defined according to precipitation daily thresholds of 0.1 mm,1 mm,5 mm and 10 mm,are analyzed systematically using historic daily precipitation data from 1951 to 2010 at 672 stations in China.The results show that precipitation daily thresholds of dry days,mean and maximum dry spells with 0.1 mm,1 mm,5 mm and 10 mm and the number of long dry spells with 0.1 mm precipitation daily threshold have become longer from Northwest China to Southeast China and those in winter and autumn are longer than those in spring and summer.The spatial and temporal features of these variables are consistent with climate drought of China.The spatial and temporal features of the number of long dry spells with 1 mm,5 mm and 10 mm daily precipitation thresholds are similar to those of drought disaster occurrence in China.Long dry spells occur frequently in North China,Yellow-Huaihe river basin,Yangtze-Huaihe river basin and areas south of the Yangtze River,and most of them are observed in spring and summer.The trends of dry days,mean and maximum dry spells with 0.1 mm daily precipitation threshold increase in most parts of China,especially in southern China.But the trends of dry days,mean and maximum dry spells with 1 mm,5 mm and 10 mm daily precipitation thresholds decrease in most of western China,especially in Northwest China.