Evaluation And Projection Of Extreme Precipitation Using Multi-RCM In China

Climate change will affect the original thermal distribution and dynamic cycle of the earth system,as a result the precipitation structure will change on the global scale.Due to the influence of local climatic conditions such as terrain and monsoon,extreme precipitation in East Asia tends to be complicate in both temporal and spatial.As extreme precipitation events will do harm to social economy,human security and ecological environment,more and more attention has been paid to the research on the distribution and variation characteristics of extreme precipitation in East Asia,especially in China.Extreme events often relate to terrain factors and small scale weather systems.In order to get precipitation information in China with higher resolution to provide reference for policy making and disaster prevention,the study adopts the dynamical downscaling method to simulate and project the spatial and temporal characteristics of extreme precipitation using regional climate models.Firstly,based on three regional climate models(WRF,CCLM and Reg CM)driven by ERA-reanalysis data in CORDEX-EA-II,the simulation results of precipitation from1989-2009 are analyzed.The ability of the RCMs to simulate the temporal and spatial characteristics of extreme precipitation as well as the diurnal variation of precipitation in China are tested.The results show that these three RCMs can simulate the spatial distribution characteristics of precipitation from 1989-2009.WRF and CCLM models slightly overestimate the intensity of precipitation,while Reg CM model overestimates precipitation frequency due to its overestimation of light rain frequency.The simulation results of extreme precipitation show that WRF and CCLM models underestimate R1 mm,R10mm,R20 mm and CWD in North China and some areas of South China,and overestimate R10 mm and R20 mm in Southwest China,Northeast China and Mongolia.Reg CM tends to overestimate R1 mm and CWD while underestimates CDD.As for the diurnal cycle of precipitation,Reg CM model overestimates the amplitude in most parts of East Asia,while WRF shows better results with slightly ahead peak in some areas.The results of CCLM model needs to be improved on diurnal cycle.Then we use RCMs driven by four GCMs form CMIP5 to simulate the contemporary and future climates.The ensemble results of WRF and Reg CM models are tested from 1981-2005.The main conclusions are as follows: Both RCMs can simulate the annual mean precipitation in East Asia,in which WRF slightly overestimates the precipitation intensity while Reg CM overestimates the precipitation frequency,and the two RCMs also overestimate light rain and underestimate moderate rain in most areas.As for extreme precipitation,WRF underestimates R1 mm and CWD in most parts of East Asia,with overestimating Rx1 day and Rx5 day in most parts of China except for Southwest Basin and Xinjiang province.Reg CM underestimates R99 p,Rx1day and Rx5 day from North China to Southeast China,and overestimates CWD in most of land areas in China except Qinghai Tibet Plateau.For CDD,the two RCMs overestimate over South China and Southeast China and underestimate in the QinghaiTibet Plateau and Northeast China.In general,the ensemble results of WRF and Reg CM can simulate the frequency and intensity of precipitation as well as the extreme precipitation characteristics.Therefore,these RCMs are reliable being used to project future extreme precipitation.Finally,based on the four GCM-driven RCMs can well reproduce the extreme precipitation,the future extreme precipitation from 2031-2055 under the RCP8.5scenario projected by WRF and Reg CM.The two RCMs consistently indicating that the precipitation intensity and the frequency of heavy rain in most parts of East Asia will increase in the future.For the changes of future extreme precipitation indices,WRF and Reg CM agree that R99 p,Rx1day and Rx5 day in most areas will increase in future comparing to the historical period.Reg CM also suggests that R10 mm and R20 mm will also increase in most land areas of East Asia.Both WRF and Reg CM believe that CWD will increase in Northwest China while CDD will decrease in the future.In the meanwhile,R99 p and Rx5 day indices show an increasing trend there.