SPATIO-TEMPORAL VARIATIONS OF THE EXTREME PRECIPITATION OF MIDDLE AND LOWER REACHES OF THE YANGTZE RIVER IN RECENT 52 YEARS

Middle and Lower Reaches of the Yangtze River is not only the main agriculture region of China,but also one of the areas with precipitation anomalies and frequent floods.The study of the tendency of extreme precipitations of Middle and Lower Reaches of the Yangtze River can provide a reference for agricultural production and local flood control and disaster mitigation.Daily precipitation data from 84 meteorological stations in the Middle and lower reaches of the Yangtze River during 1961-2012 were used to derive annual maximum series(AM)and peak over threshold series(POT).We used moving average,Mann-Kendall test,linearity trend estimation and other methods to study the changes of extreme precipitation events.The results showed that(1)in the past 52 years,the extreme precipitation in the Middle and lower reaches of the Yangtze River had significantly increased,the extreme precipitation rate was 9.3mm per 10 years,the extreme precipitation had inter-decadal variation,and since 1990 the extreme precipitation had increased obviously.(2)The maximum perennial average value and standard deviation of the spatial distribution of AM and POT were the highest in Jiangxi Province,the southeastern of Hubei Province and the southern of Anhui Province.The maximum standard deviation of the spatial distribution of AM and POT occurred in the southeastern and northern of Jiangxi Province,the southeastern of Hubei Province and the northwestern of Hunan Province.It is large in the central part and small at the north and west part.The perennial average value and standard deviation AM were larger than POT,and the annual fluctuation was significantly stronger than POT.The annual fluctuation of the extreme precipitation was larger than the annual variation.(3)The annual maximum daily precipitation along the Yangtze River had an increasing trend,and the western region of the Yangtze River's northern showed a decreasing tendency.The extreme precipitation along the Yangtze River,the middle area and the eastern region mainly showed an increasing trend,and the western region showed a decreasing tendency.In the past 52 years,the extreme precipitation of Middle and Lower Reaches of the Yangtze River had an increasing tendency,and the extreme precipitation rate was 0.93mm/year.The extreme precipitation of Middle and Lower Reaches of the Yangtze River expression annual variation,the trend was low-high-low-high-lowhigh.The annual maximum daily precipitation of Middle and Lower Reaches of the Yangtze River showed a significant increasing and strengthen tendency.The extreme precipitation of each station also showed an increasing trend,but the variation degree was different.After 21 century the extreme precipitation times of Chuzhou station did not change obviously,but the extreme precipitation strength was increasing,so the precipitation was more concentrated.