一次入海气旋在黄渤海造成的海雾过程分析

Analysis of a Sea Fog Event Caused by an Extratropical Cyclone over the Yellow Sea and the Bohai Sea

利用0.25°×0.25°逐小时ERA5再分析数据、中国气象局地面观测资料和卫星遥感监测资料对2020年5月2-4日移入黄海的温带气旋引发大范围的海雾过程进行了分析,结果表明:(1)本次海雾主要发生在入海气旋的西侧和北侧,同时具有平流冷却雾和锋面雾的性质。(2)黄渤海雾发生期间气海温差在0.5~2.5℃,2 m高度露点温度略高于海温。(3)在气旋西侧和北侧都出现了雨转雾的现象,并且从青岛L波段雷达监测温度廓线显示在500 m和1500 m高度上出现“双逆温”。(4)气旋造成的湿空气辐合是本次海雾过程的重要水汽来源,降水的加湿和蒸发冷却效应同样使得近海面大气饱和度快速增长。(5)黄渤海大部海域感热通量和潜热通量均为负值,湍流热通量主要表现为大气向海洋输送,气旋造成的垂直风切变增强了大气机械湍流,使得大气和海洋进行充分的热量交换从而促进海雾在垂直方向发展。

Based on the 0. 25°×0. 25° ERA5 reanalysis data and surface observation data of China Meteorological Administration,a study is conducted to investigate a large-scale sea fog event caused by an extratropical cyclone over the Yellow Sea in May 2020. Results are as follows:(1)The sea fog mainly occurred in the western and northern of the extratropical cyclone with properties of advection cooling fog and frontal fog.(2)The air sea temperature difference is between 0. 5 ℃ and 2. 5 ℃ during the occurrence of fog in the Yellow Sea and Bohai Sea. The dew point temperature of 2m is slightly higher than the sea surface temperature.(3)The phenomenon of rain turning into fog both in the western and northern of the extratropical cyclone. The temperature profile monitored by Qingdao L-band radar shows "double inversion" at 500 m and 1500 m altitude.(4)The convergence of moist air caused by extratropical cyclone is an important water vapor source for the occurrence and maintenance of this sea fog process. The humidification and evaporative cooling effects of precipitation also make the atmospheric saturation near the sea surface increase rapidly.(5)The sensible and latent heat fluxes in most of the Yellow Sea and Bohai Sea are negative. The turbulent heat flux is mainly represented by the transport from the atmosphere to the ocean. The vertical wind shear caused by extratropical cyclone enhances the atmospheric mechanical turbulence,which makes the atmosphere and the ocean carry out sufficient heat exchange,thus promoting the development of sea fog in the vertical direction.