Simulation Assessment On East Asia Summer Precipitation And Simulation Bias Correction Using CMIP5 Model

Firstly,the reanalysis data from National Centers for Environmental Prediction and the National Center for Atmospheric Research and the precipitation data from the Global Precipitation Climatology Project is analyzed.Then,the simulation capability of the Coupled Model Intercomparison Project Phase 5 is evaluated,which simulate the climatological and interannual variability of the 850 hPa geopotential height field,the 200 hPa zonal wind,the East Asian summer precipitation.The future changes of East Asia summer rainfall,western Pacific subtropical high,East Asia jet are projected under the Representative Concentration Pathway(RCP)4.5 and 8.5 scenarios.Finally,the effect of bias correction by the principal component analysis is evaluated on simulating the East Asia summer rainfall.The prediction of the climate mean and interannual variability of the East Asia summer rainfall is carried out by the revised model data.The main conclusions of the full text are as follows:The spatial distribution of geopotential height field at 850hPa and zonal wind at 200hPa is well simulated,and the large interannual variability in the northwestern Pacific can also be reproduced.However,the interannual variability of the geopotential height field and zonal wind is overestimated in the multi-model ensemble(MME),especially in the northwestern Pacific region which varies greatly from year to year.The distribution of summer precipitation in East Asia is well simulated from southwest to northeast,which is located more southward and is weaker.The interannual variation of the summer precipitation is overestimated in the tropical Pacific,while underestimated in East Asia.The reanalysis data reveals that there is a good positive correlation between the western Pacific subtropical high and summer precipitation in the Yangtze River valley to the Japan Sea,but a negative correlation in the western Pacific.The correlation relation is still present between the East Asia jet and summer precipitation.The relation in the reanalysis data can well be reproduced in the MME,which is weaker in the East Asia and the western Pacific.Firstly,the capability of historical summer precipitation in East Asia is evaluated,and then the correlation relationship between the circulation factor and summer precipitation is also detected.The combination of the two methods can be considered as the index,for selecting models to projection research.Taking the simulation of the East Asian summer precipitation as an index alone can't effectively reduce the uncertainty.However,selecting the joint assessment index can effectively distinguish the historical precipitation simulation and future precipitation projection.Under the RCP4.5 scenario,the large interannual variation of the geopotential height at 850hPa is located in the North Pacific at the end of the 21st century,with greater interannual variation in East Asia and the Northwest Pacific Ocean.The increase of geopotential height field is obviously higher in the RCP8.5 than that of RCP4.5.It shows that the interannual variability of the geopotential height field will become stronger in East Asia and the Northwest Pacific under the global wanning.In the RCP4.5 scenario,the interannual variability of the zonal wind varies greatly from 40 °N.The enhancement of interannual variability is mainly reflected by the enhanced north-south migration of the upper-air jets.Although the future interannual variability of the East Asia summer rainfall is obviously different in both scenarios,the precipitation variability projecting by most of the models increase in East Asia and the western Pacific.The precipitation in East Asian summer rain belt and the western Pacific region will experience more variability at the end of the 21st century,indicating that these areas will have greater risks of droughts and floods in the future.The bias correction method can effectively improve simulation capability of the East Asia summer rainfall used by the principal component analysis.The revised result is closer to the observation in 2006-2016 and the simulation effect of the East Asia summer rainfall is increased by 3.0%?9.5%.Under the RCP4.5 and RCP8.5 scenarios,the revised linear trend of the East Asia summer rainfall is dominated by the of-0.012 mm·d-1·10a-1 and-0.025 mm·d-1.10a-1 respectively from 2006-2100.There is a good agreement between different model combinations in simulating the interannual variability of the East Asia summer rainfall.The interannual variability is larger in East Asia and the western Pacific.After correction,the interannual variability of the East Asia summer rainfall will be increased by 21.2%and 19.4%respectively in both scenarios.