Study on annual variation of rainfall erosivity in southwest China using gravity center model

The correlation between rainfall time-series and vegetation time-series is one of the key factor that determining the soil erosion. So, study on the annual variation of rainfall erosivity has very important significance for revealing the characteristics of the correlation between rainfall time-series and vegetation time-series and determining the dangerous period of the soil erosion. 439 meteorological stations and hydrological stations were used in this study to estimate the rainfall erosivity in the southwest China. The annual variation of rainfall erosivity was discussed based on the gravity center model. The results showed that the rainfall erosivity changed significantly in a year, which was the highest in summer and was the lowest in winter. The spatial distribution of rainfall erosivity has the decreasing trend from the southeast to the northwest regions of the southwest China. The spatial distribution of rainfall erosivity is similar to that of precipitation. The annual variation of the monthly mean rainfall erosivity in southwest China can be divided into two patterns. One is single peak pattern for the most areas, with peak values occurring in June, July or August. The other one is two peaks pattern for the east part of Qinghai-Tibet Plateau, with peak values occurring in June and September respectively. The peak values are postponed form the southeast of the study area to the northwest of the study area. The gravity center of the rainfall erosivity in the southwest China moves northward firstly, and then moves southward during a year. This shows the annual variations of rainfall erosivity during the year under the influence of monsoon climate in the southwest China.