The Change Of Extreme Precipitation And Temperature And Their Relationships With Plateau Summer Monsoon In Southwest China

Based on the daily precipitation data and maximum and minimum temperature data of 90 meteorological stations of Southwest China during 1970-2010, used 10 extreme precipitation indices defined by the world meteorological organization such as RX5day、PRCPTOT、PPER 、TX90p 、TX10p et al. The F test、11-year moving average、low pass filter、wavelet analysis、EOF were used to analyze the temporal and spatial distributions of extreme precipitation and temperature events in Southwest China in recent 41 years. The correlation analysis and synthetic analysis were used to analyze the relationship between extreme precipitation indices and Plateau Summer Monsoon, also analyze the relationship between extreme temperature indices and Plateau Summer Monsoon.On the spatial scale, for extreme precipitation indices, long term changes in extreme precipitation trend of Southwest has obvious geographical differences, with the characteristics of gradient change from east to west or northwest to southeast. There existed significantly increasing trend of RX5day(December-February)、SDII、PPER and CDD in large part of Southwest China, there existed increasing trend of PRCPTOT and RX5day(September-November) in large part of Southwest China, The increasing areas are roughly equivalent. For extreme temperature indices, The results indicate that in recent 41 years,hot days and cold days are symmetrical in local places,hot nights and cold nights are symmetrical in most areas.On the time scale,the trend of RX5day(December-February)、RX5day(MarchMay)、RX5day(June-August) of Southwest China increased slowly,RX5 day showed decreasing trend; R95p、SDII and PPER showed increasing trend, but PRCPTOT and CDD showed decreasing trend. In recent 41 years hot extreme indices showed significant increasing trend; cold extreme indices showed significant decreasing trend.The results of wavelet analysis showed that extreme precipitation indices had obvious variation, but the periodic oscillation was not entirely consistent, There existed certain short period oscillation and long period oscillation. The periodic oscillation of hot extreme indices and cold extreme indices were not the same, but all of them existed a four year period oscillation. The results of EOF indicated that in recent 41 years, the first 3 modes of extreme precipitation indices and extreme temperature indices showed features of zonal distribution.The plateau summer monsoon existed interdecadal variation, the plateau summer monsoon was stronger from mid 70’s to about 1992, the plateau summer monsoon was weaker from1992 to 2005.Through the Mann-Kendall mutation test, the mutation characteristics of the plateau summer monsoon was analyzed, the results showed that the plateau summer monsoon occurred an obvious mutation in about 1992,after 1992,the plateau summer monsoon weakend.The plateau summer monsoon index and extreme precipitation indices/ extreme temperature indices have significant correlation. on the interdecadal scale, there existed a significantly negative linear correlation between the plateau summer monsoon and R95p、PRCPTOT、RX5day during the same period(July). For extreme temperature indices,there existed a significantly positive linear correlation between the plateau summer monsoon and TX90 p during the same period(July).however, there existed not significantly linear correlation between the plateau summer monsoon and TN90 p during the same period(July).For the spatial correlation between R95 p and plateau summer monsoon,in the northwest Sichuan、eastern Sichuan existed a significantly negative correlation,in eastern Yunnan existed a significantly positive correlation. For the spatial correlation between TX90 p and plateau summer monsoon,in the most part of Sichuan,Chongqing and in northern Guizhou existed a significantly positive correlation. For the spatial correlation between TN90 p and plateau summer monsoon,in the northwest of Sichuan existed existed a significantly negative correlation,in eastern Sichuan existed a significantly positive correlation.