青岛近海“20210427”海雾过程的观测与诊断分析

Observation and diagnostic analysis of"20210427"sea fog process in Qingdao offshore

利用欧洲中期天气预报中心的ERA5格点资料和探空、自动站观测数据,对2021年4月27日发生在青岛近海的一次海雾过程进行观测与诊断分析。在海雾发生前,黄淮和江淮的降雨为表层大气提供了充沛的水汽,伴随地面风向转为西南风,暖湿空气在离岸风的作用下,从江苏东北部入海流向青岛近海,遇冷海面生成平流冷却雾。探空数据分析表明,此次过程存在两个逆温层,海雾生成于较低的逆温层下,且雾层较薄;上层逆温层以下存在低云,并受弱下沉运动的影响高度持续降低。低层较强西南暖湿气流的存在,加之冷空气发展移动较慢,海表面较稳定的环流形势使海雾维持了较长时间;伴随西北气流影响,雾层消散。

This paper uses the ERA5 grid point data of the European Center for Medium-Range Weather Forecasts,as well as sounding and automatic station observation data,to observe and diagnose a sea fog process that occurred in Qingdao offshore on April 27,2021.Before the occurrence of the sea fog,the rainfall in the Huanghuai and Jianghuai regions provided abundant water vapor for the surface atmosphere.With the change of the surface wind direction to the southwest wind,the warm and humid air flowed from the northeast of Jiangsu to the offshore of Qingdao under the action of the offshore wind,and generates advection cooling fog when encountering the cold sea surface.Analysis of sounding data shows that there are two temperature inversion layers in this process.Sea fog is generated under a lower temperature inversion layer,and the fog layer is thinner.There are low clouds below the upper inversion layer,and the height continues to decrease due to the weak subsidence movement.The existence of strong southwest warm and humid air flow in the lower layer,coupled with the slow development and movement of cold air,and the relatively stable circulation situation on the sea surface make the sea fog maintain for a long time and with the influence of Northwest air flow,the fog layer dissipates.