Climate change characteristics of the spring drought in southwest- south China

By using nearly 50 a precipitation data and NECP data of 131 stations in southwest and south China,and the linear trend analysis,synthesis analysis and other methods,the spring droughts were divided into no drought dry,light dry,medium dry,heavy drought and special drought five levels according to season- scale precipitation anomaly percentage. The spatial and temporal distribution characteristics of all levels of droughts nearly 50 a were analyzed. The results showed that in this areas,each level of drought had increased from east to west; severe drought and special heavy drought concentrated in southwestern Sichuan- northern Yunnan,southern Guangdong and southern Guangxi; mild drought and the drought had a down- drop- down decadal variability,they were reduced from 1960 s to mid- 1970 s,increased in the late 1970 s to mid- 1990 s,and rapidly reduced in 1996,followed by slowly increasing. Severe drought and light drought had a significant reduction. 1963 was the heaviest year of drought in 50 years,followed by 1969,1979 and 1995. The distributions of arid and arid reasons were discussed from 700 h Pa height field and vertical velocity field.