The Effect of Sea Surface Temperature on Relative Humidity and Atmospheric Visibility of a Winter Sea Fog Event over the Yellow-Bohai Sea

Abstract

Sea fog is one of the main types of dangerous weather affecting offshore operations. The sea surface temperature (SST) has an important influence on the water vapor content and intensity of sea fog. In order to study the impact of SST on local relative humidity and atmospheric visibility, a sea fog episode that occurred over the Yellow Sea and Bohai Sea on 21 January 2013 was investigated through observational data, reanalysis data, and Weather Research and Forecasting (WRF) simulation. The results show that the influence of SST on the distribution of sea fog with different properties is inconsistent. Based on the time-varying equation of relative humidity, the changes in the advection, radiation, and turbulence effects on the relative humidity with respect to SST are explored through control and sensitivity experiments. The results show that the advection effect plays a decisive role in the generation and dissipation stages of sea fog. The increase (decrease) in SST weakens (strengthens) the radiative cooling and relative humidity. The contribution magnitude of advection effect to relative humidity is 10−5, while those of radiation and turbulence are 10−6 and 10−7, respectively. The atmospheric visibilities in the Bohai Sea and northern Yellow Sea decrease with increasing SST, which are mainly affected by the positive turbulence effect; whereas the atmospheric visibility in the central and southern Yellow Sea increases with SST, which is mainly influenced by the combined effects of U-direction advection, radiation, and turbulence. The stability related to boundary layer height plays an important role in water vapor condensation.

Characteristics of Advection Fog at Qingdao Liuting International Airport

“…We estimated fog thickness based on sounding data and found that average CF thickness is larger than EF thickness, which is consistent with ERA5 data (Figure 12c). Abundant studies have analyzed the formation process and characteristics of fog over the YS based on satellite, buoy and ship observation data [10,15,16], but few studies have focused on coastal fog mechanisms. This study found that there are significant differences in the EF and CF characteristics at Liuting International Airport (Table 1).…”

“…Studies have shown that fog formation over the YS is affected by sea-atmosphere interactions, and the local SST is one of the main driving factors [10,15]. Due to Liuting International Airport's location in the coastal area of Qingdao city, sea-land-atmosphere interactions can influence EF and CF formation, and local SST must be a driving factor for coastal fog formation.…”

“…CF forms when SST becomes generally colder than SAT and is dominant in summer in the YS area [9,14]. Studies have shown that the local SST is the main driving factor of annual fog variation in the YS area, and the advection fog formation process is sensitive to SST [10,15]. The difference between SST and SAT is about 15-20 K when EF forms in the Arctic region, but what is the difference between SST and SAT when EF and CF form in the YS area?…”

Southward Migration of Arctic Ocean Species During the Last Glacial Period

“…Nevertheless, the modern Arctic Ocean and NW Pacific Ocean are very different environments (Figure 1 and Figure S4 in Supporting Information S1). From 1982 to 2017, sea surface temperatures (SSTs) in the YS ranged from 13 to 18°C (Y. G. Liu, 2017), and based on older records dating from January 1958 to December 2008, the monthly mean temperatures of bottom waters in the YS were ∼0-10°C between December and May and ∼10-25°C from June to November (Li et al, 2015). Additionally, the mean SST of the Sea of Japan ranged from 5 to 20°C from 1982 to 2018 (Lee & Park, 2019).…”

The Boundary Layer Characteristics and Development Mechanism of a Warm Advective Fog Event over the Yellow Sea

“…When the air temperature is higher than the SST, the heat is transported from the air to the sea surface to cool the air, which is conducive to the formation of sea fog [1]. However, if the air temperature is far greater than the SST, and the air in the lower boundary layer is overly stable, the fog will only occur in the near sea surface layer and will not develop upward to reach a greater thickness [10]. Hence, an appropriate air-sea temperature difference play decisive role in the formation of sea fog.…”