Analysis on Variation Characteristics of Precipitation Time Series in Weihe River Basin during the Past 55 Years

By using linear regression, moving average, Mann-Kendall test and Morlet wavelet analysis method, the annual, flood seasonal and dry seasonal precipitation series during 1954 similar to 2008 in Weihe River basin are analyzed. The results indicate that: (1)Annual precipitation and precipitation in flood season and dry season present decreasing trends during the past 55 years, and the variation trends are not significant. (2)There is an irregular spatial distribution of mean annual precipitation, which shows a decreasing trend from southeast to northwest. (3)Annual precipitation exists principal periods of about 2, 10, 17 and 50 years, and the phase changes of 2 and 50 years period are most obvious. Time scales of phase change of precipitation series in flood season and dry season are roughly consistent with those in annual. The research results will provide reference for climate analysis and future weather forecasting in Weihe River basin.