Abstract:

A wide range of radiation fog shrouded North China at 18:00 on January 21, 2013. Based on mesoscale model of WRF (the Weather Research and Forecasting Model) V3.5.1, the predictability of this case is discussed, through comparison between different horizontal resolution of the boundary layer scheme (BLS) and large eddy simulation (LES) scheme. The results indicate that there exists a certain capability to simulate this fog through the BLS, but also exists a delay of 3 hours; however, through LES, both of the occurrence time and distribution of fog can be well simulated. More accurate results can be obtained by improving the horizontal resolution, which makes the occurrence time and distribution closer to the observation. Further analysis shows that, compared with BLS, LES simulates lower temperature of the surface, more water vapor, higher relative humidity and earlier occurrence of the temperature inversion. As a result, in this example, LES is capable of significantly improving the forecast skill of the mesoscale model for radiation fog in North China.

Key words: WRF, large eddy simulation, radiation fog

摘要：

利用WRF V3.5.1, 对2013 年1 月21 日18:00 华北地区突发的大范围辐射雾过程进行模拟, 对不同水平分辨率的 WRF 边界层方案以及大涡模拟(LES)进行对比, 讨论中尺度模式对此次事件预报的可能性。结果表明: WRF 边界层方案对这次辐射雾有一定的模拟能力, 但模拟的发生时间有3 小时的延迟, 而LES 方案能很好地模拟出此次大雾过程的出现时间和雾区位置; 提高水平分辨率可以改善 LES 模拟的结果, 使得雾的形成时间和雾区范围更接近实况。进一步的分析表明, LES 实验模拟相比边界层方案, 地面的气温更低, 水汽更多, 相对湿度更大, 逆温层出现更早。因此对于这个个例而言, LES 可以明显提高中尺度模式对华北地区辐射雾的预报技巧。

关键词: WRF, 大涡模拟, 辐射雾