鄂西山区副高边缘局地暴雨的GRAPES-Meso模式检验评估

Verification of Grapes-Meso model for local rainstorm occurring on the edge of subtropical high in the mountain area of Western Hubei

选取2017—2020年鄂西山区10次发生在副高边缘的暴雨过程,利用传统点对点TS评分和对象检验评估GRAPES-Meso的预报性能,并对比了发生短时强降水前的环流形势场、强降水发生的水汽和不稳定等环境场。结果显示,GRAPES-Meso模式在鄂西山区降水预报偏弱,对象检验评估较传统点对点TS评分能更客观评价模式强降水的位置、形状、方向等信息。模式对集中型局地暴雨过程预报效果好于分散型局地暴雨过程;模式预报的水汽条件存在系统偏差,露点温度东高西低的整体分布预报正确,但是对十堰北部、恩施南部山区的露点温度预报均偏低2~4℃;在目标评分较高的个例中,K指数大致可以预报出十堰附近的相对大值区,但是对于发生在宜昌附近的暴雨过程,K指数预报严重偏低。GRAPES-Meso模式预报的环流形势场效果最好,在目标评分较高的个例中,模式能够较好地模拟出辐合中心的位置、出现强辐合的时间,可以为预报预警提供中尺度辐合区、切变线等信息。

Selecting 10 heavy rain processes that occurred on the edge of the subtropical high in the western Hubei mountain area from 2017 to 2020,using traditional point-to-point TS scoring and object testing to evaluate the forecast performance of GRAPES-Meso,and compared the circulation field,water vapor and unstable environmental field before the occurrence of short-term heavy precipitation.The results show that the precipitation forecast of GRAPES-Meso is too small,and the object inspection evaluation can more objectively evaluate the location,shape,and direction of heavy rainfall in the model than the traditional point-to-point TS score.The forecast effect of the model for concentrated local rainstorm process is better than that for decentralized local rainstorm process;the water vapor conditions predicted by the model are systematically biased,and the overall distribution of the dew point temperature is correct,but the dew point temperature forecast in the mountainous area of northern Shiyan and southern Enshi is 2~4℃lower than the actual situation.In the case with a higher target score,the K index can roughly predict the relatively large value area near Shiyan,but for the heavy rain process near Yichang,the K index forecast is seriously low.The GRAPES-Meso model has the best effect of forecasting the circulation.In the case with a higher target score,the model can better simulate the location of the convergence center and the time of strong convergence.It can provide mesoscale convergence zone,shear line and other information for forecast and early warning.