Scientia Marina, Vol 76, No S1 (2012)

On the parameterization of the drag coefficient in mixed seas

Héctor García-Nava
Instituto de Investigaciones Oceanológicas, Universidad Autónoma de Baja California, Mexico

Francisco J. Ocampo-Torres
Departamento de Oceanografía Física, Centro de Investigación Científica y de Educación Superior de Ensenada, Mexico

Paul A. Hwang
Remote Sensing Division, Naval Research Laboratory, United States


An analysis of the performance of parameterizations for the drag coefficient CD over the ocean is presented. The results were obtained by considering detailed observations from the recent IntOA experiment in which a co-existence of wind sea and swell provides characteristic mixed sea conditions in a wide range of wind speeds. Recent research has advanced our understanding of air-sea fluxes, proposing new functional forms for the drag coefficient, as well as applying wavelength scaling and determining dimensionally consistent expressions for the drag coefficient. Nevertheless, a detailed analysis of the influence of wind sea parameters confirms the need to include the sea state dependence on parameterizing CD for mixed sea conditions. It is also shown that better results are obtained when aerodynamic roughness is considered as a function of wave age and wave steepness, or equivalently if CD is expressed as a function of a characteristic peak frequency defined through the wave momentum spectrum.


drag coefficient; sea state; swell; mixed seas

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