An Observational And Numerical Study On A Sea Fog Event Over The Yellow And Bohai Seas In Spring Of 2005

A dense sea fog happened at 27th Mar 2005. The images of GOES(Geostationary Operational Environmental Satellite), NOAA (National Oceanic and Atmospheric Administration), MODIS ( Moderate Resolution Imaging Spectroradiometer) and FY-1D and other available data such as FNL (Final analysis data) of NCEP (National Centers for Environmental Prediction), MICAPS (Meteorological Information Comprehensive Analysis and Process System), surface observation data and sounding data are used to recognize and analyze the fog. Satellite images provide information on the area and the shape of the sea fog; MICAPS and surface observation data show the visibility and the specific humidity of the sea fog. It can be seen that this sea fog affected visibility on the sea and the coast cities very seriously. FNL is used to analyze the synoptic situation, the temperature difference between the sea surface and the air two meters above the surface and the transport of specific humidity. It shows by the sounding data that there is inversion layer under 900 hPa and the vertical structure is stable. Then, RAMS model is used to simulate this sea fog event. The distribution of simulated horizontal visibility is similar to the fog region on the visible satellite images. The evolution of the visibility at Dalian station is also close to the observed visibility there. The experiments of SST (Sea Surface Temperature) sensibility show that a temperature difference of more than 2 oC between the sea surface and the air two meters above the surface is necessary to the formation of sea fog. The experiments also suggest that a low SST will limit the development of sea fog.