吉安一次持续性平流辐射大雾天气成因分析

采用Micaps 3.1资料、赣州探空资料、宜春风廓线(WPRD,60 min)风场产品以及吉安自动观测系统资料,分析2012年11月18—19日吉安一次持续性平流辐射大雾天气过程的大尺度天气背景、动力和热力结构特征及其演变等,揭示了这次平流辐射大雾过程的形成和维持机制。结果表明,这是冷暖平流在有利条件下经过辐射冷却后形成的平流辐射雾。在有利的大尺度背景条件下,暖平流移动到冷的下垫面和冷平流移向较暖的近地层,同时地表净辐射进一步加强近地层冷却,是此次大雾过程的触发和加强机制。特殊的温度场结构增加了低层暖湿空气和下垫面之间的温差,近地层至低层弱的辐合和垂直上升运动有助于小风的维持和稳定;充足的水汽为大雾长时间维持提供了有利条件。近地层风速增大和低层逆温层、湿度层消失是这次连续性平流辐射雾消散的主要原因。

Analysis on the Cause of A Continuous Advection Radiation Fog in Ji'an

Using Micaps 3.1 data, sounding data in Ganzhou, wind profile (WPRD) (60 min) wind farm products of Yichun and automatic observation system data of Ji'an,the synoptic background, dynamic and thermal structure characteristics and evolution of the persistent advection radiation fog weather process in Ji'an from November 18 to 19 in 2012 were analyzed,the mechanism of formation and maintenance of the advection radiation fog was revealed.The results showed that this was the advection radiation fog formed by the warm and cold advection under favorable conditions after radiation cooling.In the large scale background under the favorable conditions, the warm advection moved to the surface of cold and cold advection moved to warmer surface layer, and the surface net radiation to further strengthened the ground cooling, the fog process was triggered and strengthening mechanism.The special temperature field structure increased the temperature difference between the warm air of the lower layer and surface.The weak convergence and vertical motion of the surface layer to the lower layer helped to maintain and stabilize of the wind.Sufficient water vapor provided a favorable condition for heavy fog for a long time.The main reason for the continuous advection radiation fog dissipation was the increase of the wind velocity near the surface layer and the disappearance of the low temperature inversion layer and the humidity layer.