2018年2月琼州海峡一次持续性海雾过程特征分析

Characteristics of a Persistent Sea Fog Process over the Qiongzhou Strait in February 2018

基于逐小时地面常规观测资料、L波段探空资料、风廓线雷达风场资料和日本葵花气象卫星数据及ERA-Interim再分析资料,对2018年2月15—25日琼州海峡持续性海雾过程进行诊断分析。结果表明:此次持续性海雾过程分为4个阶段、3种类型,即15—17日辐射雾、18—20日和24—25日平流雾、22日锋面雾。辐射雾期间,琼州海峡为均压型环流控制,夜间气温降低,水汽处于饱和状态,1000 m以下存在双层逆温结构,雾顶出现在第一逆温层底部。两次平流雾期间,琼州海峡为入海变性高压脊后部偏强的东到东南风控制,气温(相对湿度)长时间维持不变(饱和),但18—20日的低空湿平流较24—25日强,水汽辐合层较厚,且比湿持续增大,致使平流雾持续时间较长;600 m以下较大的垂直风切变使雾层混合均匀,雾顶可发展至1000 m以上。锋面雾期间,徐闻站为4 m·s^(-1)以上的偏北风且伴有弱降水,琼州海峡附近低空为湿平流(水汽辐合)中心和冷暖平流交汇的锋区。海雾各阶段,气-海温差在-2~3℃之间,当气-海温差增大时,海雾消散。

Based on hourly ground conventional observation data,L-band sounding data,wind profile radar data,Himawari satellite data from Japan and ERA-Interim reanalysis data,the characteristics of a persistent sea fog process from 15 to 25 February 2018 over the Qiongzhou Strait were analyzed.The results show that the persistent sea fog process was divided into four stages and three types,including radiation fog from 15 to 17 February,advection fog from 18 to 20 and 24 to 25 February and frontal fog on 22 February,respectively.During the radiation fog,the circulation situation of pressure field over the Qiongzhou Strait was uniform,the air temperature dropped and the water vapor was saturated at night,and the double-layer inversion appeared below 1000 m,the fog top appeared at the bottom of the first inversion layer.During two advection fogs,the stronger east-southeast airflow at the back of denatured high pressure ridge entering sea controlled the Qiongzhou Strait,and the temperature(relative humidity)kept constant(saturated)for a long time.Compared with the advection fog from 24 to 25 February,the low-level wet advection of advection fog from 18 to 20 February was stronger,the water vapor convergence layer was thicker,and the specific humidity increased persistently,which were conducive to its persistence for the long time.The larger vertical wind shear below 600 m mixed the air evenly,and the fog top reached 1000 m and above.During the frontal fog,the wind speed of northerly wind exceeded 4 m·s^(-1)at Xuwen station,and accompanied by weak precipitation.The center of wet advection(water vapor convergence)and the frontal area of intersection between cold and warm advection located at lower layer near the Qiongzhou Strait.In each stage of sea fog,the air-sea temperature differences were-2 to 3℃.When the temperature difference increased,the sea fog dissipated.