Abstract: Based on the monthly precipitation data from 1953 to 2010 in the southwest mountain area of Zhejiang province, the precipitation characteristics were analyzed on the different time scales. The annual, seasonal and monthly drought and flood distributions and its evolution trend were studied using methods of a precipitation anomaly percentage and a Morlet wavelet transform. The results show that the rainfall and rain day are in the decreasing trends in the southwest mountain area of Zhejiang province over the past 58 years, especially for rain day, and its decreasing rate is 3.39 days per decade. Rainfall increases in August and decreases in May significantly, while rain day decreases in May and December significantly. The drought and flood has different cycles on different scales according to a Morlet wavelet transform method, and the intensity of each cycle differs. Among all cycles, features of two cycles i.e. a 4-8 years cycle and a 16-20 years cycle are significant. It is estimated that the trend of drought and flood will develop to flood after 2010 in the southwest mountain area of Zhejiang province. It is light drought and light flood on inter-annual scale in the study area. Drought and flood mainly appears from August to December on seasonal and monthly scales. The probability of drought is higher than that of flood, while the intensity of flood is greater than that of drought.

Key words: Climatology, Precipitation, Drought and flood change, Morlet wavelet analysis