Abstract:

Based on the daily rainfall data of meteorological stations of Henan Province in the flood seasons (1961~2006)，taking 95 percentiles as threshold value of precipitation events，the time series of frequency of extreme precipitation events in the past forty six years was constructed，the methods of trend analysis，maximum entropy spectrum analysis and other statistical techniques were employed to analyze the characteristics of spatial distribution and interannual variation.The results showed that：totally，the frequency of extreme precipitation events in south area was higher than that of in north area in Henan，and there was a consistency between the proportion of rainfall in flood seasons and the frequency of extreme precipitation events；There were four different patterns of spatial distribution：the type of consistency in provincial range，the type of northwest to southeast，the type of Nanyang Basin and the type of midland；The change tendency was different in different areas in the past fortysix years，the extreme precipitation events tended to be decreasing in the west area and south area，yet there was a increasing trend in north area，east area，middle area and south west area；and the interdecadal change characteristics of frequency oscillation was different respectively，and the cycle of two to eight years and the cycle of ten years were the most common.

Key words: Henan Province/ extreme precipitation/ frequency/ flood season