Evaluation of Temperature and Wind Characteristics and CMA-GFS Forecasting Performance under Cold Wave Events in the Beijing Tianjin Hebei Region

Based on various data such as CMA-GFS numerical model forecasting, global sounding and ground encrypted automatic station observations, and ERA5 reanalysis, 37 cold wave events from 2000 to 2024 were screened and the distribution characteristics of cold wave cooling and wind speed in the Beijing Tianjin Hebei region were statistically analyzed; A multidimensional test was conducted on the spatial and temporal deviations of CMA-GFS high-altitude, temperature, and the highest and lowest ground temperature at 2 meters, as well as the wind field at 10 meters, with different reporting times of 0-72 hours in advance, for 11 cold wave events. The performance of multi factor forecasting was carefully evaluated, and the possible causes of ground temperature model forecasting bias were discussed. Research has shown that: (1) regions with an average maximum cooling amplitude greater than 6 ℃ during cold wave events are concentrated in the northern and southern parts of Beijing, Tianjin, and southeastern Hebei. The cooling amplitude in the northern mountainous areas of Beijing is significantly higher than that in the plain areas; The areas with a maximum cooling amplitude greater than 16 ℃ are mainly located in mountainous areas, while the maximum cooling amplitude of most other stations is concentrated at 8-12 ℃; The distribution of 2-minute average wind speed and maximum gust values is similar, with overall lower wind speeds in non coastal areas of plains and higher wind speeds in mountainous and coastal areas. (2) CMA-GFS can effectively predict the atmospheric circulation situation in the upper troposphere during cold wave events, but there is a certain deviation in temperature prediction. Most event temperature prediction deviations do not decrease with the approaching reporting time, and some events show the maximum prediction deviation in the nearest reporting time. For the highest ground temperature forecast, it is better than the lowest temperature. The highest temperature forecast for 63.6% of the cold wave event is relatively low, with areas with low forecasts concentrated in Beijing, Tianjin, and central Hebei. The ME, RMSE, station accuracy, and deviation dispersion reported from 00 hours are all better than other reporting times; The minimum temperature forecast for most cold wave events is relatively high, with high altitude areas concentrated in the northern and western parts of Hebei and the northern part of Beijing. The best effect is to start reporting 36 hours in advance. The prediction error of wind speed at 10 meters in the Beijing Tianjin Hebei Plain area is mostly between ± 2m/s for most stations, and a few stations have a relatively large prediction error. The best prediction effect is achieved 36 hours in advance, and the maximum error is achieved at 00 hours. (3) The ground temperature prediction bias of the CMA-GFS model originates from the high-altitude temperature prediction bias, and in some cases where the temperature prediction is accurate, it may be related to non adiabatic errors caused by relative humidity and other factors.