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

Abstract

A large-scale persistent fog event occurred over the Yellow Sea of China from April 27 to May 4, 2015. In this study, we used satellite remote sensing data, ground meteorological observed data, global sounding data, and reanalysis data from the National Centers for Environmental Prediction (NCEP) and sea surface temperature (SST) data from the National Oceanic and Atmospheric Administration (NOAA) to analyze the evolutionary characteristics, the boundary-layer marine meteorological characteristics, and the development mechanism of the sea fog event. The results show that the sea fog event was a warm advective fog process. The Yellow Sea was at the rear of the warm high and the front of the continental low (circulation situation with high in the east and low in the west). The southerly and southeasterly winds transported warm and moist air from the Northwest Pacific northward to the Yellow Sea which served as the water vapor source. A thermal turbulence interface was formed during the sea fog development. The weak vertical wind shear below the interface was conducive to the maintenance and development of sea fog in the area of the temperature inversion in the boundary layer and the formation of a certain thickness of sea fog. The sea fog occurred in the area with water vapor convergence, where the 2-m dew point was slightly higher than the SST. The area with a relative humidity greater than 90% and an air–sea temperature difference from 0 to 2 °C overlapped with the sea fog area, and these two values indicate the extent of the sea fog.