渤海海峡至黄海北部低压顶部型海雾特征分析

Analysis of Sea Fog of Bohai Strait to the Northern Coast of the Yellow Sea

选取2001年2月21-22日和2011年8月15-16日2次海雾过程进行对比分析,研究低压气旋顶部型海雾的高低空环流配置及物理量分布特征。利用地面观测实况和探空资料,结合NCEP再分析资料计算的物理量场,对低压气旋顶部型海雾的形成、持续和消散进行综合分析。分析结果显示,低压气旋顶部型海雾持续时间长,强度大。低压气旋的顶部或右前方盛行偏南风或西南风,偏南风或西南风带来的暖湿气流:(1)为海雾的形成提供了充沛的水汽条件;(2)容易在对流层低层形成逆温或等温的稳定层结;(3)在低层形成暖平流。稳定的大气层结,较好的水汽条件,配合较弱的垂直运动,有利于海雾的形成和持续。当低压气旋顶部的偏南风不断增大到一定程度(风速>10 m/s),容易破坏海雾发生区上空的稳定层结,温度平流增大,加速湿空气在水平方向和垂直方向上的输送和扩散,不利于海雾的维持。当低压气旋过境后,低压气旋后部的偏北风带来的冷空气容易形成冷平流,有利于海雾的消散。

Two sea fog events on 21-22 February 2001 and 15-16 August 2011 were compared and analyzed,characteristics of configuration of atmospheric circulation at high and low levels and distribution of physical quantities of sea fog with the synoptic pattern of top of cyclone were invented. Based on surface observation and sounding data,combined with physical quantities calculated from NCEP reanalysis,the formation maintenance and dissipation of this kind of sea fog was researched. The results indicate that this kind of sea fog has long duration and strong intensity. Southerly or southwesterly prevails on top of cyclone brings warm and wet air from south,which would provide abundant moisture for the development of sea fog,tend to form inversion or isothermal layer and cause warm advection. Stable stratification,adequate water vapor and weak vertical motion favor the formation and lasting of sea fog. When south wind on top of cyclone increases to some extent（wind velocity〉10 m/s）,stable stratification above fog area is vulnerable to collapse,and temperature advection also strengthens,which accelerates transportation and diffusion of wet air in horizontal and vertical direction,hindering the maintenance of sea fog. After cyclone passage,northerly from rear portion of cyclone brings cold air,and cold advection promotes dissipation of sea fog.