Abstract: Soil erosion has become a global ecological and environmental problem. Soil erosion not only lead to the destruction of land resources and reduced crop yields,but also cause water pollution and reservoir sedimentation,and increase flood risks. Therefore,the evaluation of regional soil erosion risk by analyzing the spatial and temporal variation of rainfall erosivity is of both scientific and practical significances. In order to study the spatial and temporal variations of annual rainfall erosivity and rainfall erosivity at each level in Yunnan province and its five sub-regions, this study used the data of daily rainfalls for nearly 43a from 120 observation stations in Yunnan province and made the systematic analysis through Man-Kendall trend test,Morlet continue wavelet transform and other approaches. The results indicated that: the annual mean rainfall erosivity is 4415.6 MJ·mm/(hm²·h·a), the annual mean precipitation is 1081.6 mm and the average precipitation day is 150.5 d. The erosivity of heavy rain played the leading role in regulating the annual rainfall erosivity,65.4-71.4% of the annual rainfall erosivity was generated from the rainfall erosivity of heavy rain or at a higher level that accounted for 5.3-8.5% of the annual precipitation days. 4.2-6.9% of erosive precipitation days was generated from the rainfall erosivity of heavy rain that accounted for 38-43.9% of the annual rainfall erosivity. The spatial distribution of average rainfall erosivity is basically consistent with that of average precipitation. The spatial distribution of average rainfall erosivity and precipitation is significantly different from that of average precipitation days. The diversity of spatial distribution of rainfall erosivity at different levels increased with the precipitation levels. The spatial distribution of rainfall erosivity at the same level is highly related with that of precipitation. Tn the Northwest Yunnan areas,the erosivity of heavy rain played the leading role for most of the months. In the remaining areas,the rainfall erosivity of moderate rain played the leading role in the dry season while the erosivity of heavy rain played the leading role in the rainy season. For the rainfall erosivity at each level, higher rainfall level is characterized by greater seasonal variation and concentration . In each region,the rainfall erosivity of moderate rain was relatively reduced while the rainfall erosivity at other levels was predominately reduced. The rainfall erosivity of rainstorm was relatively changed to a greatest extent while the rainfall erosivity of heavy rain and moderate rain was changed at a relatively slow rate. In each region,the annual rainfall erosivity and rainfall erosivity at each level generally has 3-4 fluctuation periods,the major oscillation period was measured by 9a in terms of the annual rainfall erosivity,the erosivity of heavy rain and the erosivity of moderate rain in the Northwest Yunnan areas. The major oscillation period was measured from 18a to 21a in the remaining areas. In terms of the rainfall erosivity of heavy rain,the major oscillation periods were largely distinguished in each region.

Key words: Yunnan province, different magnitude of rainfall, rainfall erosivity, wavelet analysis