甘肃天水地区最大日降水量变化特征及可能最大日降水量估算

Variation Characteristics of the Maximum Daily Rainfall and Estimation of Possible Maximum Daily Precipitation in Tianshui of Gansu

基于甘肃天水地区7个站点的逐日降水资料，研究了该地区1951~2012年逐年最大日降水量的变化特征，并利用改进的Hershfield理论方法估算其可能最大日降水量，主要结论如下：（1）近62 a来，天水地区年最大日降水量平均约为59.2 mm，均方差为15.9 mm，最大值达110.5 mm，最小值仅有32.7 mm，说明该地区最大日降水量的年际变化幅度较大。此外，各站点最大日降水量主要集中在6、7、8月，约占总体的78.2%，其中7月最多，8月次之；（2）天水地区1951~2012年间年最大日降水量存在明显的准2a、准4~5a、准8~10a、准15a以及准48a的振荡周期，且最大日降水量在未来一段时间内有增强趋势，年变化幅度有可能增大；（3）天水地区的可能最大日降水量（ PMP）为170.5 mm，天水、麦积、武山、甘谷、秦安、张家川、清水等站点的PMP分别达148.0、159.6、124.1、133.4、137.4、146.5、153.1 mm，强度均达到了大暴雨标准。

Based on the daily precipitation data at 7 stations in Tianshui of Gansu Province,the variation characteristics of the maximum daily rainfall from 1951 to 2012 were investigated,and the period was analyzed by the empirical mode decomposition（ EMD）. Second-ly,the possible maximum daily precipitation（PMP）was estimated by using the improved Hershfield statistical method. The results are as follows：（1）In the past 62 years,the average value of annual maximum daily rainfall was 59. 2 mm,mean-square error was 15. 9 mm,the maximum and minimum value was 110. 5 mm and 32. 7 mm,respectively,which indicated that the annual fluctuation of the maximum daily rainfall was during 1951-2012. In addition,the maximum daily rainfall for all meteorological stations mainly concen-trated in June,July and August,accounted for approximately 78. 2% of the total,especially in July and August.（2）The annual time series of the maximum daily rainfall in Tianshui had obvious oscillation period of quasi-2,4-5,8-10,15,48 years during 1951-2012,and the trend raised significantly and,the change magnitude was likely to increase in the next period.（3）The PMP was 124. 1-159. 6 mm in the different station of Tianshui,while the whole area was 170. 5 mm,and that in each station exceeded the standard of heavy rainfall.