Mesoscale Model Analysis of Sea Fog Formation and Dissipation Near Kunsan Air Base.

摘要

This research used the Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS) to examine the physical processes affecting sea fog development near Kunsan AB. The simulated sea fog event occurred from 30 March to 02 April 2011 and was validated using observations. Model results were analyzed from three perspectives. A trajectory analysis examined the evolution of the wind, air-sea interaction, and thermodynamic properties of the air column prior to the sea fog formation; a time variation of similar properties at fixed locations investigated the evolution of the fog for the entire life cycle of the fog event; and a vertical cross-section through Kunsan AB revealed the spatial variability and the effects of coastal circulations. Finally, evaluation of a current forecast tool, Fog Stability Index (FSI), was conducted to determine its adequacy. Results from this analysis indicated strong influence of the adjacent sea on the fog development and maintenance at Kunsan AB. For the fog event studied in this research, fog initially developed as nocturnal fog over land, but was later maintained by advection from the sea. Strong cooling within the fog layer was present resulting in significant surface-air temperature difference, likely associated with radiation cooling. Radiative cooling, however, did not result in turbulent mixing due to the shallowness of the fog layer and the stable thermal stratification. The presence of the fog layer along the coast appeared to modify the coastal circulation, which was also an important component in introducing moisture into Kunsan AB for fog formation/maintenance. Dissipation of the fog was dominated by synoptic changes. A modified version of FSI is suggested based on results from this study.