12th Conference on Interactions of the Sea and Atmosphere


Study of Drag Coefficient as a Function of Atmospheric Turbulence and Ocean Wave State

Tamara K. Grimmett, NOAA/ERL, Idaho Falls, ID; and G. H. Crescenti, T. L. Crawford, and D. C. Vandemark

For current predictions of heat, moisture, and momentum fluxes in the marine atmospheric boundary layer (MABL), the bulk aerodynamic method is the simplest and most convenient method to employ. However, uncertainties in the neutral transfer coefficients as a function of wind speed, particularly low wind speeds, is still a crucial question (Fairall et al, 1996). Also the effect of sea surface roughness on the transfer coefficients is little understood. Improving the parameterizations of the transfer coefficients used in the bulk aerodynamic method as applied to the MABL through high-fidelity, high-resolution data gathering techniques is the objective of this study. This research is part of the larger CBLAST-Low program.

The LongEZ research aircraft (N3R) is ideally suited to the task of gathering near surface atmospheric and remotely-sensed ocean surface properties over large spatial scales at low altitudes (~10m) in short periods of time. It is an especially powerful tool for studying the spatial variablity of air-sea fluxes.

Data from a recent field experiment (CBLAST-Low) involving the LongEZ research aircraft will be presented. The plane is equipped with a three laser altimeter array and a nadir-pointing Ka-band scatterometer used to determine long and short wave characteristics, respectively, of the sea surface. The normalized radar cross section (NRCS) is computed from these instruments' data. Fluxes are determined using the eddy-correlation method. The effect of the sea surface roughness as characterized by the NRCS on the drag coefficient, Cd, is studied.

extended abstract  Extended Abstract (484K)

Session 4, Part 2: Air-sea Fluxes and interfacial processes
Tuesday, 11 February 2003, 8:30 AM-9:30 AM

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