北京及其周边地区一次大雾的数值模拟及诊断分析

利用美国国家大气研究中心研制的第5代中尺度模式系统MM5对2002年12月1~4日北京及其周边地区出现的一次大雾进行了数值模拟研究,模拟的雾出现和消散时间与实况一致。同时对雾形成和维持的机制进行了分析,讨论了雾发生发展阶段的物理过程,并对影响大雾过程的辐射条件做了敏感性试验。结果表明:形成大雾的主要原因是大气层结稳定,水汽充沛,地面的长波辐射冷却;近地面层微物理过程充分发展和雾顶的强烈辐射降温致使雾在垂直空间上出现爆发性发展;而太阳短波辐射对雾的减弱消散有着重要影响;深厚逆温层的维持对雾层长时间维持起着决定性作用。

Numerical Simulation and Diagnosis of a Dense Fog in Beijing and Its Penumbra

The fifth-generation Pennsylvania State University-National Center for Atmospheric Research Mesoscale Model was utilized to simulate a dense fog occurred in Beijing and the area around on 1-4 December 2002,the results of simulation in formation and dissipation of the fog are coincide with the real situation,in the same time,the mechanism of formation and maintenance of the fog are analyzed,and the physical process of formation and development is also discussed.Sensitive experiments are performed for understanding the role of radiation.The results showed that longwave radiative cooling is very important for the formation of the fog in addiation to steady atmospheric stratification and plenty of moisture.And the active microphysics process near the ground and stronger radiative cooling on the top of the fog result in the burst development of fog.The fog dissipation was influenced most by shortwave radiation.In addiation,the sustentation of the deep inversion play a decisive role in the course of prolonged fog.