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

摘要

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.%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。