中国降雨过程时程分型特征

Characteristics of intra-storm temporal pattern over China

为研究降雨过程雨强随历时的变化关系,利用中国14个气象站近40年逐分钟降雨资料,采用动态K均值聚类法并根据雨峰在降雨过程中出现的位置,将中国10256次降雨过程分为4种类型,即降雨前期集中型(I型)、降雨中期集中型(II型)、降雨后期集中型(III型)和降雨均匀分布型(IV型)。结果表明:中国I型降雨出现频次最高,占47.1%;II型次之,占21.2%;III型和IV型出现频次相当,分别占15.3%和16.4%。夏季I型降雨发生频次占绝对优势,为夏季总降水过程的52.2%;冬季各类雨型发生频次相差不大。I型多为短历时高强度降雨,而IV型多为长历时低强度降雨,II型和III型居中。历时越短时,I型降雨的比重越大;随着降雨历时的增加,I型降雨的比重明显下降,IV型降雨的比重增加。

To describe the characteristics of intra-storm temporal distributions of rainfall,minute resolution rainfall data were collected from 14 weather stations in China covering nearly 40 years. A total of 10 256 storms with precipitation amounts greater than 10 mm were analyzed. Based on a dynamic K-means cluster method and the time to peak index,the storms were divided into four hyetograph types： Rainfall concentrated early in the storm（ Type I）; rainfall concentrated in the middle of the storm（ Type II）; rainfall concentrated at the end of the storm（ Type III）; and rainfall distributed uniformly over time（ Type IV）. Type I storms occurred most frequently（ 47. 1%）,followed by Type II（ 21. 2%）,Type III（ 15. 3%）,and Type IV（ 16. 4%）. In summer,Type I storms had a normalized occurring frequency of 52. 2%,suggesting that Type I storms were the most prevalent storm type during the summer. In winter,all four storm types occurred with similar frequencies. Type I storms were characterized by shorter durations and higher intensities,whereas Type IV storms had longer durations and lower intensities. The average duration,intensity,and the maximum 30 min intensity for Type I storms were 19. 2 h,2. 8 mm /h,and 20. 3 mm /h,respectively,whereas that for Type IV storms were 30. 0 h,1. 4 mm /h,and 8. 6 mm /h.