关键词: 年最大日降水量, EMD分解, Hershfield理论方法, 可能最大日降水量

Abstract:

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). Secondly, 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 concentrated 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.

Key words: maximum daily rainfall, Empirical Mode Decomposition,  Hershfield statistical method, 24 hours probable maximum precipitation