山东中西部一次持续性大雾的形成及维持机制

Mechanisms Analysis of Formation and Maintenance of a Sustained Heavy Fog in Central and Western Shandong Province

利用常规气象观测资料和NCEP/NCAR提供的6 h再分析资料（分辨率为1°×1°）,对2013年1月12-16日发生在山东中西部地区的一次持续性大雾天气过程从环流背景、层结条件、动力和热力学机制等方面进行了诊断分析。结果表明：中高层偏西气流、对流层低层温度脊和地面冷高压的稳定维持为这次持续性大雾过程提供了有利的环流背景;大雾过程经历了辐射雾—平流辐射雾—平流雾的复杂演变阶段,不同阶段的大雾湿层厚度及逆温强度有所不同;适当的风速和低层弱的水汽辐合有利于大雾稳定维持和发展;近地层辐合上升、中高层辐散下沉,易在界面形成逆温层,有利于大雾的出现,而整层的辐合上升运动往往容易形成中高云,不利于近地层水汽的聚集,难以形成大雾。

Based on the conventional observation data and NCEP 1° × 1°reanalysis data,the circulation background,atmospheric stratification,dynamic and thermal struture for a sustained heavy fog from 12 to 16 January 2013 in central and western Shandong Province were analyzed.The results showed that the straight westly air flow in middle and upper level,the warm temperature ridge at low level of troposphere and the persistant surface cold high provided an appropriate condition for the sustained heavy fog weather event.The sustained fog event went through three phases including radiation fog,radiation-advection fog and advection fog,the thickness of moist layer and the intensity of temperature inversion were different in different phases of the fog event.The proper wind velocity and low-level weak water vapor convergence were favourable to the fog weather.The low-level convergence ascending movement and middle-high level divergence descending movement formed inversion layer at the interface,which was favorable to appearence of the thick fog,while the entire level convergence ascending movement was easy to form medium and high cloud,which wasn＇t favourable to vapour gathering,so there was no thick fog.