Verification and Assessment of "23·7" Severe Rainstorm Numerical Prediction in North China

During the severe rainstorm in North China from 31 July to 1 August in 2023, CMA-GFS, CMA-EPS, EC-EPS, EC-HR, NCEP-GFS, CMA-TYM, CMA-MESO, and CMA-BJ are tested and evaluated using synoptic verification, threat score (TS), and MODE (method for object-based diagnostic evaluatin). The persistence and intensity of long-term heavy rainfall, as well as the area and intensity of short-term heavy rainfall, are tested and analyzed for their effectiveness over time. Results indicate that the cumulative precipitation predicted by EC-EPS may exceed 100 mm for 14 days in advance, but there is no prediction ability for extreme heavy precipitation above 600 mm. EC-HR forecast for the location of precipitation is generally accurate up to 8 days in advance. In the short term, the daily precipitation intensity forecast by CMA-BJ closely matches the actual situation, indicating its significance in predicting precipitation extremes. The average and maximum precipitation values of CMA-GFS, EC-HR, and NCEP-GFS in the areas with concentrated heavy precipitation are lower than actual values. CMA-GFS doesn't perform very well while EC-HR is closer to the actual situation. CMA-GFS, EC-HR, and NCEP-GFS models all provide inadequate forecasts for the persistence of heavy rainfall. However, EC-HR has a relative advantage in predicting persistent precipitation 8 days in advance. TS of CMA-BJ is highest for precipitation forecasts above 50 mm and 100 mm. EC-HR and CMA-TYM precipitation forecasts above 50 mm are relatively stable. From the daily MODE results of the precipitation concentration period from 29 July to 31 July, it is evident that EC-HR exhibits a northward predictive characteristic, while the prediction of CMA-BJ is slightly southward. The forecasting ability of CMA-GFS is insufficient, and forecasts from NCEP-GFS and CMA-MESO are not stable. The high-pressure system in North China has a significant impact on the precipitation. EC-HR model forecasts the formation and reinforcement of a 500 hPa high-pressure system 3 to 4 days earlier than CMA-GFS and NCEP-GFS models. It also surpasses both in predicting the precise location and strength of intense precipitation. Additionally, EC-HR model predicts the emergence of a 925 hPa low-pressure trough and a low-level jet 7 days in advance. However, it underestimates the intensity of the trough and jet system, with the actual location being to the west to north. CMA-GFS and NCEP-GFS underestimate the impact of the Taihang Mountains on easterly winds, leading to significantly lower precipitation forecasts. The analysis of the deviation in the 36 h precipitation forecast for 30 July also shows that EC-HR has weak predictions for low-level wind fields, trough positions, and convective precipitation, resulting in a weak intensity of heavy precipitation and a west-north precipitation area.