Characteristics of precipitation days and intensity over the Huaihe River basin in flood season during recent 50 years

The Huaihe River basin is located in the transitional zone from north subtropical to south warm temperate climate.The characteristics and influential factors of precipitation in different fields are various.This study investigated the distribution and determined the influential factors of precipitation in flood season over the Huaihe River basin.For this goal,the meteorological observation data of 145 stations from 1961 to 2010 were collected and analyzed.The percent of different intensity rainfall days and the ratio between storm days and rainfall days were calculated.Finally,the temporal variations of meteorological observation data were analyzed.The results showed that rainfalls in the southern of Huaihe River basin are higher than those in the northern,affected by several factors,such as terrain,moisture and wind.Meanwhile,rainfall exhibited temporal characteristics,with the percent of storm cases and ratio of storms to rainfall increasing from 1961.This study derived two main conclusions: first,the precipitation of the Huaihe River basin became heterogeneous in spatial and temporal distribution with the changing of climate;second,the heavy rain cases such as storm occurred more frequently than before.