Vertical Structure of the Marine Atmospheric Boundary Layer Across a Sea SurfaceTemperature Front

摘要

The response of the lower marine atmospheric boundary layer to a sharp change insea-surface temperature was studied in the (FASINEX) Experiment with ships and aircraft instrumented for turbulence measurements. Synoptic conditions on 14th and 16th Feb. 1986 presented the opportunity to study the vertical structure of the turbulence for the case of a North wind, blowing from the cold to warm side of the front. A moving boxcar averaging technique was used to determine the turbulent statistics and fluxes for the meteorological variables, and their associated changes, as the air made the transition from the cold to warm side of the front. Aircraft flight tracks for the two days were designed to investigate somewhat different aspects of the marine atmospheric boundary layer, concentrating on either the vertical structure alone (14 Feb) or on both the vertical and horizontal structure (16 Feb) in the vicinity of an oceanic temperature front. The depth of the atmospheric boundary layer was found to be approx. 200 m deeper over the warm water than was found over the cold water. The potential temperature was found to respond very rapidly to the underlying warm water throughout the entire depth of the boundary layer. The vertical heat flux for each day showed a pronounced increase over the warm water. Heat flux for the 14th showed two organized convective cells in the immediate vicinity of the front; this type of organized convection was not found on the 16th. (EDC)