Abstract
An analysis of the performance of parameterizations for the drag coefficient C D 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 C D 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 C D is expressed as a function of a characteristic peak frequency defined through the wave momentum spectrum.
Highlights
Air-sea fluxes are key boundary processes for both the atmosphere and the ocean
Foreman and Emeis (2010) proposed a new functional form to represent the drag coefficient for moderate to strong winds where no wind speed dependence was determined. While their results approximate rather well with data sets reported in the literature, the swell influence was not explicitly included in the analysis and the sea state conditions considered were wind sea-dominated
At low winds it is expected that the greatest effect of swell on momentum flux will be brought by the direct interaction of the swell waves with the air flow
Summary
SUMMARY: 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. RESUMEN: El coeficiente de arrastre sobre la superficie del mar como función de las características del oleaje. A través de investigaciones recientes se ha avanzado en el conocimiento de los flujos entre el océano y la atmósfera, al proponer nuevas formas funcionales del coeficiente de arrastre, así como al utilizar expresiones dimensionalmente consistentes que se basan en escalas asociadas a la longitud de onda de las olas. Los resultados de este trabajo confirman la necesidad de incluir la influencia del estado del mar en las parametrizaciones del coeficiente de arrastre, especialmente bajo condiciones mixtas de oleaje. Palabras clave: coeficiente de arrastre, estado del mar, swell, oleaje mixto
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