Characteristics of Spring Vegetation Variation over Tibetan Plateau and Its Influence on Summer Precipitation of Southwest China

On the basis of the monthly precipitation data for the period 1982-2001 collected from 96 observational stations in Southwest China (SWC) and normalized difference vegetation index (GIMMS NDVI), the characteristics of spring vegetation variation over Tibetan Plateau (TP) and its influence on summer precipitation in SWC have been analyzed. The result of our research may lead to the following conclusions: the condition of spring NDVI over eastern and southern arid regions of TP was in a good state but bad in western and northern arid regions. The spring NDVI over TP increased in recent 20 years. Correlation and SVD analyze show that there are obviously connections between the summer precipitation fluctuation in SWC and those in preceding spring vegetation variation over TP. Corresponding to the NDVI in preceding spring is positive departure distribution over TP, especially in mid-western and northern arid, the precipitation appeared a decreasing trend in northern Sichuan, eastern Sichuan and Chongqing and increase in other arid of SWC, vice versa. These results lead to a conclusion that the growth of vegetation over TP may be an important forecasting index which can provide us a new possible clue for SWC rainfall forecasting.