Study On Extreme Precipitation Evolution And Disaster Prevention Engineering In East China

Extreme precipitation is an important type of extreme weather events.Studying the characteristics of spatio-temporal changes and predicting their future trends is of great significance in understanding the extreme weather and climate processes in the context of global warming.In this study,we first detect the spatial and temporal distribution characteristics of extreme precipitation index over East China(six provinces and one city)based on observed dataset.It reveals the changes of extreme precipitation in historical periods,regional differences.Second,the influence of circulation index and urbanization on extreme precipitation index in East China is discussed.Third,we have evaluate the ability of the global climate model IPSL-CM5A-LR of the CMIP5(Coupled Model Intercomparison Project)and its nested WRF regional climate model to simulate precipitation in the East China region,especially extreme precipitation.And on this basis,variation characteristics of extreme precipitation indices in the mid-21 st century(2041-2060)under RCP85 and RCP85 scenario respectively over East China were analyzed.The main conclusions are as follows:(1)Based on the daily precipitation observation data,linear trend analysis and Mann-Kendall trend test techniques,the temporal and spatial variation characteristics of extreme precipitation indices in East China from 1960 to 2015 are investigated.The results show that the interannual trends of selected indices are all increasing excepting for CWD,and the intensity and frequency of rainfall and the contribution rate of extreme precipitation all increase obviously.Spatially,the variation trends of the extreme precipitation indices showed obvious regional differences and regional agglomeration characteristics,and the intensity,frequency and continuity of precipitation increased significantly in the middle and south of East China;Extreme precipitation also increased in central and southern East China and decreased in the north;the continuous rainfall day(CWD)showed a decreasing trend in East China as a whole,and a significant trend in the south of East China.This means that extreme precipitation events are more likely to occur in the central and eastern coastal areas of East China.(2)Based on wavelet analysis and Mann-kendall mutation test method,the change period and abrupt changes of extreme precipitation indices during 1961-2015 in East China are analyzed.The results show that the time series of each extreme precipitation index have multiple time scale characteristics,and the main period is approximately the same,about 28 years.The extreme precipitation index has a significant mutation in 1961-2015 years,most of which occurred in 80 and 90 s of twentieth Century.(3)Based on circulation index and DMSP /OLS data and socio-economic statistics,the division of urban and rural sites in East China was carried out,and the impact of atmospheric circulation and urbanization on extreme precipitation in East China was analyzed.The results show that among the selected circulation indices,the western hemisphere warm pool index(WHWP)and North Atlantic decadal oscillation(AMO)are significantly related to the extreme precipitation index,and mainly positively correlated with the extreme precipitation index of sites in Zhejiang,Jiangxi and Fujian;Urbanization also exacerbates extreme urban rainfall to a certain extent.It increases the extreme precipitation threshold of the city and exacerbates the increasing trend of extreme precipitation.(4)Based on observation data and climate model of IPSL-CM5A-LR and WRF,the ability of simulating the extreme precipitation indices in East China during the historical period(1981-2000)were evaluated.The results show that the numerical simulation and spatial distribution of each extreme precipitation index simulated by WRF model are closer to the observed values,and the simulation ability of the IPSL-CM5A-LR model is optimized to some extent.(5)Under future scenarios of RCP45 and RCP85,annual precipitation will increase in the central and northern parts of East China and decrease in the southeast part of China,and the increasing range under RCP85 is greater than the RCP45 scenario;Rainfall days will increase in the north of East China and decrease in the south,and the decreasing range under RCP85 is less than the RCP45 scenario.For other extreme precipitation indices,the prediction results are different between different models and different scenarios,but the estimated increase in the RCP85 scenario is greater than the RCP45 scenario.In general,the frequency and intensity of the extreme precipitation in East China will increase.(6)According to the characteristics of East China's natural geography,the flood control and disaster prevention work in East China will take different defensive measures in the three aspects of river basin,city and coastal area,but it also should be allocated rationally and harmonize with each other.The non engineering measures are necessary when the engineering measures are applied correctly.The two kinds of measures can be used comprehensively to build a modern and complete flood control system.