黄、东海春季海雾“楔”形雾区分布特征及其成因分析

Analysis on Formation and Characteristics of Sea Fog Events with Wedge Shape over the Yellow and East China Sea in Spring

基于可见光云图、地面天气图、探空数据、船舶实测数据、下垫面海表面温度资料(SST)和再分析数据,采用数理统计和个例分析相结合的方法,对近10年的黄、东海连片大范围海雾过程的时空特征进行分析,并选取2011年3月12-13日、2014年4月9-11日、2018年3月31日-4月1日3次典型“楔”形海雾个例从天气形势、水汽输送、层结条件和下垫面海温等方面进行重点研究,结果表明:(1)“楔”形雾区表现为黄海海区为大范围雾区覆盖,东海沿海呈细长条带状分布,即北部宽广、南部细长的“楔”形分布特征。(2)“楔”形雾区海雾个例多发生于春季,发生概率占春季大范围海雾的30%左右,其中4月的最多,其次是3月的,5月的最少,春季雾频分布同样具备“楔”形分布特征。(3)“楔”形雾区海雾多属于北太平洋高压后部型的平流冷却雾,大尺度环流背景场控制下的水汽输送、下沉运动、层结条件导致了海雾的形成。(4)海陆分布、SST分布尤其海表面温度梯度锋(SSTF)限定了海雾雾区发展,对雾区“楔”形分布起决定作用。

Using the visible satellite cloud images,surface synoptic charts,sounding data,measurement data by ships,sea surface temperature(SST)data and reanalysis data,as well as mathematical statistics and case study methods,this paper analyzes the spatial and temporal characteristics of the sea fog events with large-scale fog range in the recent ten years.Three sea fog events during 12-13 March 2011,9-11 April 2014 and 31 March to 1 April 2018 are picked and intensively studied from the aspects of synoptic situation,water vapor transport,atmospheric stratification and sea surface temperature to find out the characteristics and formation of the wedge-shaped sea fog.The results show that:(1)The sea fog events with wedge shape are featured with huge fog area over the Yellow Sea and ribbon fog area over the East China Sea,that is,the wedge-shaped distribution of broad in the north and elongated in the south.(2)The sea fog events with wedge shape have higher occurrence rate in spring,accounting for about 30% of the spring large-scale sea fog events,of which April sees the most,followed by March and May in order.Besides,the fog occurrence frequency in spring is also distributed in the pattern of wedge.(3)The sea fogs in the wedge-shaped fog area mostly belong to the advection cooling fog in the rear part of North Pacific high pressure.Under the control of the large-scale atmospheric circulation background,the water transport,atmospheric subsidence and stratification conditions etc.play highly important roles in the formation of wedge-shaped sea fog.(4)The sea-land distribution,SST distribution and sea surface temperature gradient front(SSTF) distribution jointly confine the development of fog area.Especially,SSTF acts as the key factor for the formation of wedge-shaped sea fog events.