中国地区降水持续性的季节变化特征

本文利用我国588个气象站1969-2008年逐12小时的降水资料，分析了中国地区降水持续性的空间分布特征及其季节演变规律。分析结果表明，35°N以南，西部和东部年平均的降水平均持续时间较长，中部略短；35°N以北，西北和内蒙西部最短，东北地区北部略长。将降水事件按持续时间分类自南向北，东南地区、江淮和黄淮地区、东北和华北北部地区短时降水（持续一个时次，12小时）的降水量和降水频率占全年总降水的比例逐渐增加，持续性降水（持续3个时次及以上）的比例减少。降水平均持续时间随季节的变化基本能反映出江南春雨、江淮梅雨、东北和华北夏季雨季、关中盆地和汉水谷地的秋雨以及青藏高原地区和西南地区夏季雨季。同时，东南地区秋冬季节、江淮和黄淮地区10月上旬和西南地区10月下旬存在降水平均持续时间的峰值，与降水量的变化不一致，是由持续性降水频率的增加和短时降水频率的减少造成的。此外，东部三个区域降水平均持续时间的夏季季节内变化对应了季风雨带的“北跳和南撤”过程。

Analyses of Seasonal Variation Characteristics of the Rainfall Duration over China

Using 12-hourly station rain-gauge data at 588 stations during 1969-2008,this paper analyzes the spatial characteristics and seasonal variation of rainfall durations over China.The result shows that in south of 35°N,the annual mean averaged rainfall duration over eastern and western regions is longer than that over the middle region,while over north of 35°N,northwestern China and the west of Inner Mongol, the averaged rainfall duration is the shortest all over China,and the rainfall duration over the north of northeastern China is longer.According to the duration time,precipitation events are classified.Over the three regions of eastern China(southeastern China,the region of Jianghuai and Huanghuai,and the region of northeastern China and the north of North China),the percentages of the short-duration rainfall(1 time duration for 12 h) to the total rainfall gradually increase during the whole year for both amount and frequency, while those of long-duration rainfall(no less than 3 times duration) decrease.The seasonal variation of averaged rainfall duration in China reasonably reflects the spring persistent rain over southeastern China,the Meiyu,the summer rainy season over northeastern China and the north of North China,the autumn rain over Guanzhong Basin and Hanshui River Valley and the summer rain over the Tibetan Plateau and southwestern China.The averaged rainfall duration is long in autumn and winter over southeastern China,in the first dekad of October over Jianghuai and Huanghuai region and in the last dekad of October over southwestern China,which is not in accordance with the variation of rainfall.These features can be attributed to the increasing frequency of the long-duration rainfall and decreasing frequency of the short-duration rainfall.Subseasonal variation of averaged rainfall duration over the three regions of eastern China corresponds to the ’northward advance and the southward retreat’ of the monsoon rain belt.