基于沿岸自动气象站的台湾海峡西岸海雾生消过程及特征

Process and characteristics of occurrence and dissipation of sea fog in the west coast of the Taiwan Strait based on coastal automatic weather station*

2019年4月19日20时—4月26日07时,台湾海峡西岸发生了一次严重海雾事件,通过海西沿海的自动气象站数据进行了海雾生消规律研究。海雾集中于02时至08时发生,其生成时间越接近清晨,持续时间越短。海雾多为本地生成,部分站点海雾为传播而形成且南北海雾之间关联性不大。海雾发生前能见度均快速下降,海雾消亡后能见度快速上升。当海雾生成时,陆表温度–气温LST-T(LST,land surface temperature;T,temperature)在-1.7~2℃之间,陆表温度–露点温度LST-Td(dewpoint temperature,Td)在-1~2.7℃之间,T-Td在0.2~1℃之间,海雾维持阶段相对湿度(relative humility,RH)≥96%。在水汽丰沛的大背景下,海雾生成与发展与风速的关系较为密切,与风向的关系较弱。结合Himawari-8卫星影像与ERA5(European centre for fifth generation of atmospheric reanalysis)再分析资料对本次海雾过程的特征进行了分析。卫星影像给出了本次过程的影响范围和生消特点。环流形势表明,500h Pa上福建处于槽后脊前弱西南气流控制下。850h Pa和925h Pa高度场上均受西南气流的影响,带来了充沛的水汽,根据海气状况分析此次海雾类型为平流雾。

A severe sea fog occurred in the West Side of the Taiwan Strait from 8PM April 19,2019 to 7AM April 26,2019.Based on the coastline automatic weather station,the generation and dissipation law of sea fog was studied.Sea fog occurred from 2AM to 8AM,and the closer the generation time is to the early morning,the shorter the duration.Sea fog is mostly generated locally,some stations are formed for the purpose of propagation,and there is little correlation between north and south sea fog.The visibility decreased rapidly before the sea fog occurred and increased rapidly after the fog dissipated.When sea fog formatted LST-T(LST,land surface temperature;T,temperature)between−1.7~2℃,LST-Td(dewpoint temperature,Td)between 1~2.7℃,T-Td between 0.2~1℃.During the sea fog maintenance period,RH(relative humility)≥96%.Under the background of abundant water vapor,the formation and development of sea fog are closely related to wind speed and weakly related to wind direction.Combined with Himawari-8 satellite image and ERA5 reanalysis data,the characteristics of this sea fog process was analyzed.Satellite images show the extent of the process and the characteristics of occurrence and dissipation.Circulation analysis indicated that this sea fog event occurred under the control of weak southwest flow at 500 hPa,while at 850 hPa and 925 hPa Fujian was affected by southwest airflow,bringing abundant water vapor.According to the analysis of the sea and air conditions,the type of sea fog was advection fog.