一次持续性浓雾天气过程的水汽输送及逆温特征分析

Characteristics of the Inversion and the Water Vapor Transport during a Duration Fog Event

利用地面站观测、大气边界层观测及NCEP再分析资料,对2006年2月13～14日华北中南部一次持续性浓雾过程的水汽输送和逆温特征进行了计算和分析,研究了其与浓雾生、消发展之间的联系。结果表明:暖性弱高压脊和地面变性冷高压的高低空系统配置为浓雾的形成提供了有利的逆温层结和近地面弱风条件;在深厚逆温条件下,南支暖湿水汽的输送和辐合使毛毛雨滴下降过程中蒸发,在近地面较冷气层中再次凝结导致了浓雾的生成;加强北上的低空西南急流为浓雾的启动和长时间维持提供了大量的水汽,有利于逆温层顶抬升,湿层增厚,进而促进了浓雾的生成和发展;西北干冷空气自上而下破坏了深厚浓雾所依存的高湿条件,使雾顶下降雾层变薄,加之日出后的短波辐射使近地层空气升温,近地面的稳定层结被破坏,上下层气流交换增强,从而导致了雾最终消散。结果还表明:在近地面逆温、微风等有利成雾天气条件下,当低层持续适量的水汽辐合时,浓雾同时伴随有毛毛雨现象,当低层水汽辐散时,毛毛雨现象消失。

Based on the station observation, boundary layer observation and NCEP reanalysis data, the characteristics of water vapor and temperature inversion are discussed during the durative fog, which occurred in the North China on February 13-14, 2006. The results show that the upper and low-layer system setting of a warm high ridge at middle level and the transformed surface cold high pressure over the east of China, which are advantageous for fog formation to form temperature inversion and the feeble wind adjacent to the surface. With the deep inversion temperature, the drizzle which occurs in the water convergence directly leads to the fog when its vapor condenses again in the colder layer. The southwestern low jet stream is served to the formation and duration of the fog, which mainly contributes to the inversion existence and water vapour transport. The fog thickness is thinner and thinner when the the low level is controled by the northwestern dry and cold advection and becomes dry; meantime, the stable stratification is distroyed due to the increased temperature in the surface layer contributed by the shortwave radiation, which lead to increased mix between the up and down layers and finally achieve the dissipation of fog. It is also showed that the fog will be accompanied with the drizzle when the water vapor converges, otherwise, the fog without the drizzle company.