Analysis on the Precipitation Anomalies in Southwest of China from 2009 to 2011

The southwest of China has suffered a great drought since 2009. The authors chose five provinces(Yunnan, Guangxi, Sichuan, Chongqing, Guizhou) as the study area, by using the daily precipitation data from 1970 to 2011 of the 126 meteorological stations in the five provinces, the ten-day precipitation variation rates from 2009 to 2011 for the five provinces were calculated. The results indicated that the precipitation variation rates were negative in most time of the three years. The precipitation reduced at those years, and the decrease of precipitation was most serious in the period from October to March, which are the dry season of this area, therefore, such situation exacerbated the drought degree. The drought had some rules in the spatial distribution that the drought often happened from the Guangxi province first, and then spreaded to the Yunnan and Sichuan provinces, and the drought also ended from the Guangxi province. In addition, through the regress analysis, it was found that the precipitation of the five provinces was influenced by the West Pacific subtropical high and the Tibet plateau barometric pressure, and the effects of the different circulation parameters on the precipitation were not the same.