Spatio-temporal Characteristics And Simulation Of Extreme Precipitation In Huai River Basin

Based on the daily precipitation data of 50 stations which are uniformly distributed in the Huai River basin during 1961?2014,the spatio-temporal characteristics of strength,frequency and the occurrence timing of extreme precipitation in Huai River basin were analyzed by using the methods of linear trend,MK test,R/S analysis,circular statistics and EOF.And using the generalized extreme value model(GEV)simulate extreme precipitation,exploring the relationship of climatic factors and extreme precipitation.The main results are as follows:(1)From the long time scale analysis,the threshold of extreme precipitation in the Huai River basin has increased significantly(reached the 0.1 significant level),and there has been no significant change in frequency and magnitude.However,after the middle period of 2000s,the threshold,magnitude and frequency of extreme precipitation decreased and reached the 0.05 significant level.(2)There are obvious spatial differences in extreme precipitation affected by geographical location,typhoon and Meiyu.There are more extreme precipitation events in the east of the basin(coastal area)and in the Southwest(lower latitudes).(3)The overall rainfall intensity of the basin is increasing gradually.The extreme precipitation threshold,frequency,contribution rate and extreme value of precipitation are in the reverse phase distribution of "central and Western East"(the upward trend in the central and western regions is the main,and the downward trend is the main trend below the East).Combined with R/S analysis,extreme precipitation in the future will continue to develop in the current trend.(4)The occurrence timing of extreme precipitation mainly concentrates in the middle to late July,and shows obvious interannual oscillation.The occurrence timing of extreme precipitation in the basin shows an advancing trend,but does not reach 0.05 significant level.(5)Occurrence timing of extreme precipitation is gradually postponed from southwest to northeast in space,and most of the sites show a slightly advancing linear trend;the spatial distribution is relevant to the changes of Meiyu and typhoon,while the advancing trend may be due to the fact that the main rain belt has been moving northward since the 1990s.(6)The EOF analysis of occurrence timing of extreme precipitation indicates:the typical spatial field of the first mode shows the anti-phase distribution between the northwest and the southeast;the typical spatial field of the second mode is uniformly distributed.(7)The PX3D index sequence of most of the sites through the stability test,the stationary GEV model can better fit the PX3D index sequence.The nonstationary GEV model based on time location parameter covariates can significantly improve the fitting situation of the model for significant trend sequences,while considering the influence of significant trend when designing extreme precipitation prediction.(8)Climate factors(AMO,EASMI,PDO,SOI and Nino3.4 S ST)were used as parameter covariates of GEV model,and the fitting of PX3D index for all stations in the watershed was improved.Taking climatic factors SOI and Nino3.4 SST indices as location parameter covariates,we can better simulate the influence of extreme precipitation peak and valley change.Taking climatic factors AMO,EASMI and PDO indices as scale parameter covariates,they are more inclined to simulate the influence of extreme precipitation fluctuation amplitude change.