浙江中部一次大雾过程分析与预报

利用NCEP再分析格点资料、常规观测资料、数值预报产品以及卫星云图对2009年4月6日早晨浙江中部一次大范围大雾天气过程进行诊断分析。结果表明：高空槽后暖脊的大气环流背景有利于地面长波辐射冷却和中层增温,易形成逆温,为大雾生成提供了有利条件,而边界层逆温层或等温层的形成与维持对雾的发展持续具有重要作用;凝结核、低层湍流混合是山区能见度较城镇大的主要原因;交叉温度可用来预示整个潜在雾层的湿度状态,温度与交叉温度差值可作为了解大雾生成、发展、消散过程的一项指标;模式产品能提供雾形成的环境条件;红外云图、可见光云图有助于预测雾的形成、发展、消散过程。

Analysis and Forecasting of a Fog Event in Central Zhejiang Province

The NCEP reanalysis grid data,conventional observations,numerical forecast products,as well as satellite imagery,are used to diagnose and analyze a dense fog event occurred in the central Zhejiang Province and the surrounding areas on 6 April 2009.The results show that the circulation pattern of ＂the warm ridge behind a trough＂ is conducive to the surface cooling resulted from long-wave radiation and the mid-level warming,which is advantageous to the formation of temperature inversion,so to provide favorable conditions for fog generation.The formation and maintenance of the temperature inversion or isothermal layer in the boundary layer played an important role in the development and sustentation of the fog event.The main reasons for the higher visibility in mountain areas than that in urban areas include more condensation nuclei and stronger turbulent mixing.The crossover temperature can be used to indicate the humidity state of the potential fog layer,and the difference between temperature and crossover temperature can be used as an indicator of the generation,development,and dissipation processes of fogs.The model products can provide the environmental conditions for fog formation,and the satellite images are helpful in predicting the generation,development and dissipation of fogs.