模式水平分辨率提高对一段大暴雨预报结果的影响

Impact of Finner Model Horizontal Resolution on a Heavy Rainstorm Forecast

使用中尺度暴雨模式MRM1-不等距21层细致边界层η坐标模式，分别采用36km和18km的水平分辨率对1998年6月12日～7月31日造成长江流域特大洪水的暴雨进行数值模拟，结果表明：当把模式水平分辨率提高到18km后，暴雨及其以下降水量等级的预报TS评分与36km的相当，但大暴雨预报效果明显提高，降水分布具有明显集中的趋势，暴雨、大暴雨中心也明显向实况降雨中心靠拢。对1998年6月12～21日10个个例的数值模拟表明，水平分辨率由36km提高到18km后，网格尺度降水量占总降水量的比例由平均14．1％提高到27．5％，而次网格尺度降水量的比例由85．9％下降到72．5％；对1998年6月19日造成闽浙大暴雨的天气系统模拟对比分析表明，模式提高分辨率后，能够较好地模拟出造成大暴雨的中-β尺度低涡及其中尺度特征，预报暴雨及大暴雨的雨区有了明显的局地性，更接近实况暴雨及大暴雨的雨区。

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） varyingdistance 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 meso-βscale 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.