Abstract:

The spatialtemporal distributions of extreme precipitation events,particularly the durative extreme precipitation events,play an important role in flood disasters.Through introducing the parameters that reflect the temporal distribution of extreme precipitation process events：concentration degree (EPCD) and concentration period (EPCP),the innerannual inhomogeneity distribution characteristics of extreme precipitation process events over the Yangtze River Basin (YRB) are analyzed.The analyses were based on daily rainfall data of 142 Meteorological stations from 1960 to 2009 over YRB,using the wavelet and the principal component analysis methods.The results show that extreme precipitation process events over the upper reaches of YRB occur mainly in early July,and their occurrence is relatively intensive.While those over the middle and lower reaches of YRB occur mainly in middle May through late June,and their occurrence is relatively dispersive.Variations of EPCP and EPCD over the middle and lower reaches of YRB are more obvious than those over the upper reaches of YRB.The primary eigenvector represents the reverse EPCD and EPCP variation in the southeast area to the northwest area and the southern area to northern area over the YRB,respectively.Extreme precipitation process events have the trend of concentration and exhibit tendency of shifting to earlier age in the YRB.Furthermore,the EPCD and EPCP have main periodic oscillation of 13 years and 10 years,respectively