采用次网格地形方案对白鹤滩水电站坝区一次大风天气的数值模拟

基于中尺度气象模式，采用次网格地形方案模拟了2019年3月19~20日四川、云南交界处白鹤滩水电站的一次大风过程，对10 m风速、风向和2 m温度空间分布及日变化的模拟结果进行检验评估，并结合地形分析了坝区易产生大风的原因。结果表明：此次西南大风天气是由高低空一致的西南气流配合地面“东高西低”的环流形势共同造成的。午后热低压发展强盛，地面风速增大，坝区出现8级大风。采用次网格地形方案后，风速的平均绝对误差和均方根误差最高可分别减小17%和14%，同时该方案有效地缓解了模式对白天风速的低估和夜间风速的高估，在大风和小风时段均对风速有较好的模拟能力，从而能更好地刻画风速的日变化特征。综合来看，次网格地形方案能显著改善风场的模拟效果，其中Jiménez方案更适用于坝区大风的模拟，但次网格地形方案对温度模拟没有改善作用。白鹤滩水电站的大风受局地地形影响极大，南北向狭长河谷地形产生的狭管效应使气流增速显著，坝区主体高度区河谷风的放大系数超过3.0，使得白鹤滩水电站极易出现灾害性大风天气。

Numerical Simulation Analysis of a Gale Weather in the Dam Area of Baihetan Hydropower Station by Using the Subgrid-scale Terrain Parameterization Scheme

Based on the mesoscale meteorological model, the subgrid-scale terrain parameterization scheme was used to simulate a gale weather in Baihetan Hydropower Station, which lied in the junction of Sichuan and Yunnan province, from March 19 to 20, 2019. The simulation results of spatial distribution and diurnal variation of 10m wind speed, wind direction and 2m temperature were evaluated, and the causes of this gale were analyzed in combination with the terrain. The results were as follows: The southwest gale weather was caused by the southwest airflow consistent with the surface circulation situation of 'east high and west low'. In the afternoon, the heat low developed strongly, the surface wind speed increased, and there was a strong wind of level 8. After adopting the subgrid-scale terrain parameterization scheme, the MAE and RMSE of the wind speed could be reduced by up to 17 % and 14 %, respectively. Meanwhile, this scheme effectively alleviated the underestimation of the wind speed in the daytime and the overestimation in the nighttime, and could simulate the strong wind and light wind well, so as to capture the diurnal variation of the wind field better. In general, the subgrid-scale terrain scheme could significantly improve the simulation of the wind field, and the Jiménez scheme was more suitable for the simulation of strong wind in the dam area, but the subgrid-scale terrain scheme could not improve the simulation of temperature. The strong wind of Baihetan Hydropower Station was greatly affected by the local terrain. The “narrow pipe effect” caused by the narrow and long valley terrain in the north-south direction increased the wind speed significantly, and when the amplification factor of the valley wind at the main height of the dam area exceeded 3.0, the disastrous gale weather was prone to appear in Baihetan Hydropower Station.