北京地区一次辐射雾的数值模拟

Simulation and Analysis of a Radiation Fog Event in Beijing Area

利用非静力中尺度模式MM5V3对2006年11月20日北京地区的一次大雾天气过程进行了数值研究。模拟结果与极轨卫星监测图像以及十二通道微波辐射计观测资料的对比表明,模式对此次雾的模拟是比较成功的,尤其是在雾区的分布位置、雾的高度以及雾的维持时间等方面。针对不同的云物理方案、长波辐射项、短波辐射项以及模式的垂直分辨率进行了4组敏感性实验。结果表明,地面的长波辐射冷却促使辐射雾的形成,而短波辐射的加热是辐射雾消散的主要原因。另外,增加模式的垂直分辨率以及选取更加详细的云微物理方案可以使模式模拟的辐射雾的结果有明显的改善。

A radiation fog on 20 November 2006 in Beijing area is simulated and diagnosed with MM5 nonhydrostatic model.By contrasting the image of the NOAA satellite with the observation data of radiometer,the results showed that the MM5 could well simulate this fog event,especially in simulating the fog area,the height and the duration of the fog.Furthermore,aiming at explicit moisture scheme,longwave radiation,shortwave radiation,and vertical resolution,four sensitivity experiments were performed.The results show that longwave radiative cooling is an important factor of the formation of the fog,while the shortwave radiative warming is an important factor of the fog dispersal.In addition,the results were obviously improved by increasing the vertical resolution or using more complicated explicit cloud scheme.