Multitime Scales Analysis of Precipitation in Yellow River Delta Reserve

Based on the annual precipitation data from 1971 to 2007,the temporal variability features of the Yellow River Delta Reserve were studied by applying the wavelet analysis method.The results indicated that the precipitation in the studied area was mainly concentrated in the summer,but very little from November to March of the next year.The amount of precipitation changed dramatically sometimes,e.g.the variation was significant from the year 1974 to 1975,from 1989 to 1990,and the temporal variability in precipitation within each year was obvious,the difference in precipitation between the rainy days and rainless days was extremely evident.The wavelet analysis showed that there were 2-4yr or 4-6yr short periodic oscillations in the precipitation among the 37 years,there were also 8yr,14yr and 24yr long periodic oscillations.The results of wavelet analysis for the summer data were similar to that of the yearly data.