Numerical Studies On Precipitation And Circulation Field In Summer In East Asia After Reanalysis Data Into CESM

The ability of the CESM model is evaluated to simulate the precipitation and circulation fields in summer in east Asia in 1980-2009 by using multiple reanalysis data;Then according to the evaluation results,the "real" surface temperature is updated to the CESM mode by using the piecewise-integration method,comparing and analyzing the differences of the physical quantities and the spatial and temporal distributions of main modes between the two groups of tests;Finally,3d temperature field and wind field of reanalysis data are assimilated into the CESM to conduct numerical experiments by using the Nudging method,and the simulation result error of the adopting and no-adopting Nudging method are compared and analyzed.The main results as following:(1)CESM model could simulate the space distribution characteristic that summer precipitation reduce from the sea to inland in east Asia and that the rainbelt moves the north from spring to summer and back to the south from fall to winter;The spatial distribution of simulated precipitation in model shows that there is more precipitation on land and less on the ocean;The CESM simulated surface temperature shows the low temperature on the land and high temperature over the sea;The simulated subtropical high pressure at 500 hPa is anomaly westward to JiangHuai region in China and a strong intensity;The difference of meridional circulation between CESM and reanalysis data locates in TP and its surrounding areas,which the southern TP appears a high and narrow circulation;The CESM model can also simulate two major water vapor conveyor belts in the East Asia region,and the area of less simulated water vapor transmission is corresponding to that of low simulated precipitation.(2)Comparing and analyzing the simulated summer temperature fields of sensitivity test that "real" surface temperature in East Asia is assimilated to CESM model by using the piecewise-integration method and the control test of continuous-integration method,the result shows that the simulation results of surface temperature,precipitation,water vapor flux,zonal and meridional circulation field by using piecewise-integration are obviously improved comparing to that of continuous integral method by CESM model,which the correlation with reanalysis data is also improved.(3)The EOF analysis of the precipitation results and the 500 hPa wind field of reanalysis data,piecewise integral method and continuous integral method shows that whether the precipitation field or the 500 hPa wind field,the correlation coefficients,which the spatial and temporal distribution results of each mode are simulated,of the reanalysised and simulated by piecewise integral method are higher than those of the continuous integral test results,which shows that the piecewise-integration method has some improvement on this model.(4)The 3d temperature field and wind field of reanalysis data are assimilated into the CESM to conduct numerical experiments by using the Nudging method,and the simulation result error of the adopting and no-adopting Nudging method are compared and analyzed,the result shows that the root-mean-square error that the model simulated decreases with time and is stable within two days after adopting the Nudging method while the root-mean-square error of no-Nudging method increases with the extension of simulation time,which means that the Nudging method that the “real” reanalysis data is incorporated into the CESM colud significantly improve the simulation results of model and reduce the uncertainty of the CESM model simulation results.