Impact of Finner Model Horizontal Resolution on a Heavy Rainstorm Forecast

For rainstorm that causing special large flood of Yangtse Rive drainage area during 12 June to 29 July 1998,the numerical simulation is made using a mesoscale rainstorm model(MRM1) varying-distance layers 21 levels,high resolution PBL,Eta coordinate model with 36 km and 18 km horizontal resolution.The results show that the average threat score of precipitation from slight rain to rainstorm which using 18 km model is as much as that using 36 km,but the forecast impact of heavy rainstorm has notable progress using the 18 km model,and the centers of forecast rainstorm or heavy rainstorm clearly close observation centers.10 cases of numerical simulation on 12～21 June 1998 show a trend that the precipitation concentrating to some area,and the rate of sub-grid precipitation increase from 14.1% to 27.5%,with the rate of grid precipitation decrease from 14.1% to 27.5% after promoting the model horizontal resolution.The numerical comparative analyses for weather systems that caused great rainstorm in Fujian and Zhejiang Province on 19 June 1998 show that the mesoβscale character of weather system has been preferably simulated using 18 km model,the forecast rainstorm and heavy rainstorm fields have obvious localization,and it is more close to the observation.