Simulation experiment on"23·7"extreme precipitation in North China using the GRIST model
GRIST(Global-Regional Integrated forecast SysTem),the kilometer-scale variable-resolution(VR)model,combines the virtues of both global and regional models.It can provide medium-term forecast products without lateral conditions while it is expected to reach a forecast level similar to that of high-precision regional models.To evaluate GRIST's ability to simulate extreme weather events,this study uses the VR version of GRIST to conduct a hindcast experiment on the extremely heavy rainfall event that occurred in North China from July 29 to August 2,2023.The simulation results are evaluated against satellite-gauge merged precipitation analysis(China Merged Precipita-tion Analysis,CMPA)and global reanalysis(the fifth generation of the European Center for Medium-Range Weather Forecasts atmospheric reanalysis of the global climate,ERA5)data,and are also compared with five other operational numerical models(including global models,ECMWF and CMA-GFS,as well as regional models,CMA-MESO,CMA-SH,and CMA-BJ).Results indicate that both GRIST and five oper-ational models can reproduce the occurrence of this heavy rainfall event at various degrees.From 08 BT 30 July to 08 BT 1 August,the peri-od with the strongest precipitation during the event,the simulation performance of GRIST is optimal.The spatial correlation coefficient be-tween GRIST and CMPA can reach up to 0.85,and the TS scores of precipitation at various intensities are at the levels of regional model fore-casts.GRIST accurately simulated the large-scale circulation characteristics during this process,encompassing the location and extent of the Western Pacific Subtropical High,northward water vapor transport.Furthermore,it demonstrated a commendable capability in simulating the distribution and intensity of storm-relative helicity,a key indicator of the local circulation.The precise representation of circulation condi-tions at various scales by GRIST contributes significantly to its ability to characterize precipitation areas and the evolution of precipitation.
numerical simulationextremely heavy rainfallvariable-resolution modelglobal model
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