Extended Abstract (296K)5.3
Investigation of fog and low clouds associated with a coastally trapped disturbance
William T. Thompson, NRL, Monterey, CA; and S. D. Burk
In a continuing study of low clouds and fog associated with coastally trapped disturbances along the U. S. west coast, we have examined processes involved in buoyancy flux generation and consumption, including an evaluation of the impact of liquid water flux. We have also constructed thermodynamic budgets in order to further understand the relative importance of various forcing mechanisms. Previously, we have presented results of model validation and sensitivity studies designed to determine the relative roles of cloud top radiative cooling and surface sensible and latent heat fluxes. We utilize the Naval Research Laboratory’s Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS ) nonhydrostatic forecast model to simulate a CTD event and produce fields of fog a and low stratus. We find that 1) the lag between the wind shift and the leading edge of the CTD cloud tongue that is often observed in these events occurs for dynamically important reasons to be outlined in this presentation; 2) negative liquid water flux can be driven by strong radiative cooling in a fog that has little entrainment; and 3) total buoyancy increases southward in the fog, ultimately enhancing entrainment of warm, dry air that causes the lifting condensation level to lift away from the surface as the fog transitions to a low stratus deck.
Session 5, atmospheric and oceanic processes
Thursday, 13 January 2005, 8:30 AM-11:45 AM
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