Characteristics of ShortTime Heavy Rainfall in Hedong Area of Gansu Based on CopulaFunction
Based on minutely precipitation collected from Lanzhou, Linxia, Hezuo, Dingxi, Wudu, Tianshui, Pingliang and Xifeng weather stations in Hedong Area of Gansu Province during 1960-2014, the spatiotemporal distribution characteristics of heavy rainfall frequencies are analyzed. Besides, the risk analysis on duration and accumulated precipitation is obtained by Copula function based 〖JP2〗on a bivariate Copu〖JP〗la distribution model for heavy rainfall variables. The results show that: (1) The main characteristics of heavy rainfall in Hedong Area during recent 55 years are short duration and low accumulated precipitation. The occurring frequency is 1.64 time/(a?station), average duration is 2.88 h, average accumulated precipitation is about 23.4 mm and the probability of duration less than 1 h is up to 13.4%. (2) Heavy rainfall occurs mainly from April to September, and the monthly variation is in the normal distribution. The Mexico Hat wavelet analysis shows that there are obviously interdecadal changes of 22-23 years and 13-15 years, and interannual changes 3-7 years in the heavy rainfall. (3) The frequency of heavy rainfall from large to small is Pingliang, Xifeng, Tianshui, Dingxi, Wudu, Linxia, Lanzhou and Hezuo in order. Correspondingly, the maximum frequency occurrs in eastern Gansu, second in southern Gansu, and the smallest central Gansu.