The Naval Research Laboratory’s Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS) is a nonhydrostatic, multiply nested, numerical weather prediction model with a full suite of physical parameterization schemes, including the surface layer scheme developed by Louis (1979) for the determination of surface fluxes over both continental and oceanic surfaces. In order to improve the parameterization of the marine surface layer, a modified version of the Coupled Ocean-Atmosphere Response Experiment (COARE) bulk flux parameterization scheme is being incorporated into COAMPS. The COARE algorithm has been modified to use a polynomial approximation to the flux profile function under unstable conditions in order to improve computational efficiency. The polynomial version has been extensively tested against the standard version. Errors were found to be generally less than 0.1% for a wide range of wind speeds and stabilities.
The first phase of the incorporation of the COARE algorithm in COAMPS involves characterizing the differences between fluxes produced by the Louis scheme and those from the COARE algorithm in a one-way interactive mode. The differences between the two schemes are highly dependent on wind speed and stability; under high wind speed, nearly neutral conditions, the two schemes generally agree to within about 10%; in low wind speed, highly unstable or stable conditions, differences between the schemes can exceed 100%. In the second phase, fluxes from the COARE algorithm will be used to force COAMPS in a fully interactive mode. Phases one and two are being conducted using a one-dimensional version of COAMPS. Finally, three dimensional tests will be conducted using results of field experiments for validation. Results from all three phases will be presented.