CMA-MESO模式对“21·7”河南特大暴雨的预报评估与误差分析

为分析CMA-MESO模式对2021年7月19—21日河南特大暴雨的预报性能,除了常规观测资料,还利用雷达和卫星非常规观测资料,对模拟回波和云产品开展传统和新型空间检验,以揭示对流风暴和中尺度对流系统(MCS,基于卫星红外通道)的模式预报偏差细节,并从降水形成的水汽、动力、触发和维持机制等角度分析模式误差产生的原因。结果表明:模式能较好预报雨带形态、弱回波持续时间以及主要降水发生前期和后期MCS的面积和强度演变趋势;模式偏差主要体现在低估了降水强度且未报出郑州站极端小时降水,错报主雨带小时降水演变,严重低估了对流风暴和强对流风暴的持续时间,未能报出午后MCS面积陡增的变化趋势且MCS位置预报偏西、偏北;模式降水偏差的原因主要在于水汽的模拟,模式水汽垂直分布不合理,对台风烟花和查帕卡的水汽输送均偏弱,而水汽输送不足的根源是低空急流偏弱和超低空急流脉动不足。另外,模式未能在郑州站附近预报出稳定少动的地面中尺度辐合线,加之大气层结不稳定度不足和对流不稳定能量偏低,使得对流发展不够旺盛,最终导致降水预报不足。

Evaluation and Error Analysis of the July 2021 Extremely Severe Rainstorm in Henan Province Simulated by CMA-MESO Model

In order to reveal the deviation characteristics of severe convective storm and mesoscale convective system (MCS, in satellite infrared channel), we employ the conventional observation and the unconventional observation (radar and satellite data) to analyze the simulation performance of CMA-MESO model in simulating the extremely severe rainstorm that occurred in Henan Province from 19 to 21 July 2021 by using traditional and new spatial verified methods. Besides, we also investigate the causes for the model deviations from the perspectives of water vapor, momentum, trigger and maintenance mechanism of precipitation. The results show that, firstly, the model can well capture the shape of rain band and duration of weak echoes as well as the evolution trend of intensity and area of MCS in the early and late stages of the primary precipitation process. Secondly, the model deviations mainly lie in that the model underestimated the intensity of precipitation, failing to predict the extreme hourly precipitation at Zhengzhou Station and the evolution trend of hourly precipitation of main rain band. Besides, it seriously underestimated the durations of convective storms and severe convective storms. Furthermore, the model missed the sharply increasing of MCS area in the afternoon and the simulated MCS was displaced westward and northward relative to the observation. Thirdly, the model deviation was mainly owing to the incorrect simulation of water vapor. The vertical distribution of simulated water vapor was not reasonable, and the simulated water vapor transports from Typhoon In-Fa and Typhoon Cempaka were both weak. In fact, the weak low-level jet and insufficient ultra low-level easterly jet pulsation directly led to the insufficient transport of simulated water vapor. Moreover, the model’s failure in forecasting the stably maintaining mesoscale convergence line on the surface near Zhengzhou Station, in conjunction with the deficiency of atmospheric instability and underestimation of unstable convective available potential energy, made the development of the simulated convection not strong enough and finally caused the inadequate simulated precipitation.