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

Abstract

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.

Keywords

• sea fog
• extratropical cyclone
• temperature difference between air and sea surface
• inversion layer
• turbulent heat flux