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1. Introduction
Sea fog forms over the ocean and is a maritime navigation safety hazard. Once generated, sea fog may propagate inland by the sea breeze to decrease local visibility (Findlater et al. 1989) or transfer air pollutants from land to a broader region (Jung et al. 2021). Here we focus on two necessary conditions of sea fog: First, a temperature difference at the air–sea interface determines the sea fog types (Table 1). Sea fog is advection fog on the sea that can generally evolve into warm advection fog with surface air temperature (SAT) higher than sea surface temperature (SST) and cold advection fog with SAT lower than SST (Taylor 1917; Douglas 1930; Findlater et al. 1989; Heo and Ha 2010; Kim and Yum 2010; Huang et al. 2015). When the extremely cold air advects over the warm SST, the huge air–sea temperature difference (ASTD) will trigger a special cold advection fog—the sea smoke (Willett 1928; Saunders 1964; Roach 1994; Koračin et al. 2014). The heat transport via turbulence near the sea surface is critical for forming sea fog (Huang et al. 2015). The second necessary condition for sea fog generation is sufficient condensation nuclei (CN), either land or ocean aerosols (Koračin et al. 2014). The coarse particles (>0.5 μm) can cause fog more effectively than fine particles (<0.5 μm) (Sasakawa et al. 2003).
The warm advection fog is usually generated when moist air loses heat to the cold ocean and condensation near the sea surface (Taylor 1917; Findlater et al. 1989; Huang et al. 2015). In addition, tidal mixing (Cho et al. 2000) and wind-induced coastal upwelling could further enhance the warm advection fog, i.e., on the U.S. West Coast (Leipper 1994). The spatial scale of warm advection fog can reach several hundred kilometers and last hours, i.e., in the Yellow Sea (YS) of China (Fu et al. 2006; Gao et al. 2007; Zhang et al. 2009; Guo et al. 2015).
The cold advection fog happens near the sea surface when colder air advects over warm water. The cold air decreases the upper ocean temperature (Nelson et al. 2014), enhances the sea surface evaporation to cause saturation in the low-level atmosphere, and causes instability near the sea surface to increase heat transport,...