Page 107 - 《高原气象》2022年第6期

高 原 气 象 41 卷
1470

Analysis of a Sea Fog Event Caused by an Extratropical Cyclone

over the Yellow Sea and the Bohai Sea

LIU Longsheng，HUANG Bin
（National Meteorological Center，Beijing 100081，China）

Abstract：Based on the 0. 25°×0. 25° ERA5 reanalysis data and surface observation data of China Meteorologi‐
cal Administration，a study is conducted to investigate a large-scale sea fog event caused by an extratropical cy‐
clone 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 conver‐
gence 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 atmo‐
spheric 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.
Key words：Sea fog；extratropical cyclone；temperature difference between air and sea surface；inversion lay‐
er；turbulent heat flux