Abstract: Droughts and floods occurred frequently in summer and autumn in Zhejiang province, so it was very important for disasters prevention to study the temporal and spatial distribution and trend evolution of precipitation in summer and autumn. The temporal and spatial distribution and trend evolution of precipitation in summer and autumn was analyzed by using trend analysis, isoline distribution, EOF method and Morlet continuous wavelet transform, based on monthly precipitation data from 65 stations in summer and autumn during 1971 to 2009. The results showed that the precipitation increased at the rate of 92mm/10y in last 39 years. The spatial distribution showed decreasing trend from southeast to other areas. There was a different periodic oscillation, but concentrated in 6 to 10 years, and the 8.7year cycle was most significant, which passed the power spectrum 95% confidence test.

Key words: Climatology, Precipitation, Temporal and spatial distribution, Empirical Orthogonal Function, Morlet wavelet analysis, Power spectrum test