南岭山地一次锋面浓雾过程的边界层结构分析

利用2001年3月上旬在南岭山地进行的综合野外观测资料,分析了有雾和无雾时的天气型和边界层风、温、湿结构特征。分析表明,冷空气影响期间出现的地面雾是低空湿度饱和区向地面扩展,云底接地形成的雾,锋面雾消散过程实质上为雾层底逐渐抬升离开地面的过程。边界层结构受天气系统的影响,锋面逆温结构对雾的维持有重要作用,单层强逆温结构有利于雾的发展和维持,多层(双层)弱逆温结构容易导致雾消散;出现雾与前期低空南风强劲,高空盛行西南或西南西气流,充分回暖增湿,导致整层空气湿度大有密切关系;浓雾维持期间,出现小到中雨时,雨强峰值时间段都出现能见度短时好转的现象,否则则反之,表明云雾中的微物理过程与能见度有密切关系。

Analyses on Boundary Layer Structure of a Frontal Heavy Fog Process in Nanling Mountain Area

Using the field observational data in Nanling mountain area in the first nine-day periods of March 2001,the structural characteristics of wind,temperature and humidity and weather pattern in the periods of fog-free and heavy fog have been analysed.The analyses of sounding reveal that the surface fog is essential the saturation area extending into the surface during the cold air outbreak,and the fog form when the cloud base reach the surface ground.The dissipation process of surface fog is virtual a process of the lifting cloud base from the surface ground.The construction of boundary layer is controlled by the influencing weather systems.The construction of frontal inversion play a major role in the sustaining of cloud system or fog,the mono-layer strong inversion construction is favourable to the development of fog,while the multi-or dual-layer weak inversion constructions may lead to the dissipation of fog.The occurrence of fog closely relate to strong south wind at low-level,southwest or west southwest wind at upper air and the warming before the occurrence of fog,resulting in the high humidity of the whole layer.The observation also show that when there is light to moderate precipitation during the fog process,the visibility get better with the phase of the peak precipitation rate,the oscillations of weak and strong rain result in the oscillations of bad and better visibility,showing the close relationship between microphysics processes and visibility inside the body of fog.