Comparing in situ and satellite-based parameterizations of oceanic whitecaps

Abstract

The majority of the parameterizations developed to estimate whitecap fraction uses a stability-dependent 10 m wind (U10) measured in situ, but recent efforts to use satellite-reported equivalent neutral winds (U10EN) to estimate whitecap fraction with the same parameterizations introduce additional error. This study identifies and quantifies the differences in whitecap parameterizations caused by U10 and U10EN for the active and total whitecap fractions. New power law coefficients are presented for both U10 and U10EN parameterizations based on available in situ whitecap observations. One-way analysis of variance (ANOVA) tests are performed on the residuals of the whitecap parameterizations and the whitecap observations and identify that parameterizations in terms of U10 and U10EN perform similarly. The parameterizations are also tested against the satellite-based WindSat Whitecap Database to assess differences. The improved understanding aids in estimating whitecap fraction globally using satellite products and in determining the global effects of whitecaps on air-sea processes and remote sensing of the surface. Key Points: In situ and satellite-based wind differences affect whitecap fraction estimates Whitecap fraction parameterizations should be updated for satellite-based winds Discrepancies exist between visible and radiometric whitecap observations