Abstract:

The study of temporal trend of precipitation in river basins has been paid more and more attention.In this paper,based on the precipitation data from 13 weather stations during 1960~2003 in Hanjiang River basin,the annual and seasonal precipitation and continued rainy days were analyzed.Results showed that average rainy days in spring accounted for 25%~31% of annual rainy days,precipitation accounted for 21%~31% of annual rainfall.In summer,average rainy days accounted for 13%~18% and precipitation accounted for 50%.There were 22%~31% rainy days and 21%~29% precipitation amounts in autumn.In winter,rainfall only accounted for 6% of annual rainfall, average precipitation in rain days was 28 mm.Besides,continued rainy days distribution model in different station and seasons were studied.Chisquare goodness of fit tests was performed on precipitation data to compare the fit of the models.The results indicated that Polya probability distribution was statistically feasible.At the α=01 significance level,95% of stations in Hanjiang River basin passed the verification.But 4 stations in spring could not pass the verification.Polya probability distribution model could be used to estimate probability of continued rainy days in watershed science.It will provide guidelines for flood prevention and disaster alleviation,also will provide scientific references for the middle route of South to North Water Transfer Project in China