Mutation and Multi scale Characteristics Analysis of Rainfall Series in Dongting Lake Watershed

Abstract:

In order to study the variations characteristics of rainfall in the Dongting Lake Watershed, the method of Mann Kendall test and Morlet wavelet function were used to analyze the rainfall time series during the period of 1960—2008 in Dongting Lake Watershed. The research results showed that the annual rainfall series took on a weak increasing trend during the period of 1960—2008, while a remarkable decreasing tendency arose after entering the 21st century. The characteristic time scales of changes in annual rainfall were 3, 7 and 24 years, and the characteristic time scales of changes in flood season rainfall were 3 , 7 and 16 years during the period of 1960—2005. According to the analysis of major period of changes in rainfall, it could be conjectured the annual rainfall and flood season rainfall would both be less than the normal level during the period of 2006—2008, which agrees well with the data. The Morlet wavelet analysis method proved to be feasible in prediction of rainfall trends in the future.

Key words:rainfall; Dongting Lake Watershed; mutation; multi scale characteristics; Mann Kendall method; wavelet analysis