强对流临近预警中集合预报成员的即时分析——以陇东一次暴雨过程ECMWF集合预报应用为例

Real-Time Analysis of Ensemble Member in Severe Convection Warning——A Case of ECMWF Ensemble Prediction Apply to Heavy Rainfall of Eastern Gansu

2015年5月31日甘肃陇东地区出现一次暴雨天气过程,ECMWF集合预报系统的降水预报只有1个成员(简称EM-p)预报出暴雨,并且EM-p对预报暴雨落区、量级和降水时段的预报与观测实况基本接近。本文通过对EM-p和集合预报系统控制成员预报效果的对比分析,以及EM-p与实况的对比分析表明,EM-p对产生暴雨的对流参数预报完全符合本地经验指标,虽然对低层急流预报出现一定程度偏差,但对低层辐合区(暴雨落区)位置的预报与观测实况极为接近,因此EM-p成员能够为暴雨的短时预报和临近预警提供可靠的定量依据,可有效提前暴雨预警时间。通过分析,期望为如何利用ECMWF集合预报有效判断低概率但高影响天气的发生提供一些有益的思路。

As for the heavy rain occurred in the eastern Gansu on 31 May 2015,only one ensemble-member(shorten as EM-p)of ECMWF ensemble forecast system predicted this heavy rain process accurately.The data of the predicted precipitation area,intensity,and rainfall time by EM-p are closer to that of the observation.In this paper,a comparative analysis of the forecast of EM-p,the forecast of control ensemble-member,and observation was conducted.The result indicated that the predicted convection parameters of the heavy rain by EM-p are consistent with the local experience.EM-p can accurately predict the location of the lower-level convergence area(the heavy rain area)although with a deviation in the prediction of lower-level jet.Therefore,EM-p can provide a reliable basis for the short-term forecast and warning of heavy rain,which can also advance the heavy rain warning time effectively.It is hoped to provide a reference for howto improve the forecasting ability of lowprobability but high impact weather by using the ECMWF ensemble forecast system by analyzing this case.