Estimating Maximum Daily Precipitation by Multi-Station Method: A Case Study of North Khorasan

In 1961 Hershfield introduced a statistical method to estimate probable maximum precipitation (PMP). His method was based on the data of maximum daily precipitation of 2645 stations. Occurrences of rainfalls greater than PMP in the upcomming years, questioned Hershfield’s method. Eliason (1997) presented a multi-station method. Since PMP can occur at every point within a homogen region, this method was based on a combination of data from all stations in such a region. Gumble type 1 and its derived distributions were used as a mathematical tool. For parameter estimation however, Eliason used method of moment. In this paper, three other methods are used, namely maximum likelihood, maximum entropy, and probability weighted moments. Data of 41 homogen stations from North of Khorasan Province in Iran was utilized for comparison purposes. The performance of maximum likelihood was proved via statistical analysis. In addition, PMP is compared for all stations using modified Hershfield method. Results were compared with multi-station methodand showed the performances of the former.