Important Contributing Factors for Estimating the Active and Total Whitecap Coverage Globally Using Satellite-Derived Parameters

This study identifies the major contributing factors in estimating whitecap coverage globally from satellite observations. Power law functions for estimating both the active and total whitecap coverage from in situ observations are derived using U10 (in situ winds) and U10EN (satellite-reported equivalent neutral winds). Whitecap coverage estimates using U10EN and a power law reproduced in situ whitecap estimates better than using U10 and a power law, but, when compared with the satellite-based whitecap observations from the Whitecap Database, neither can adequately estimate the whitecap. New power law coefficients using U10EN, available in the Whitecap Database, are presented and estimates are compared to the active and total whitecap coverage from the Whitecap Database. An additional 17 parameters, independent of U10EN, are tested to determine their roles in influencing whitecap formation and duration using a modified power law; the most influential parameters are identified. The most influential parameters for the active whitecap coverage include SST, orbital velocity, air temperature, fetch, and the cross SST gradient wind; the most influential parameters for the total whitecap coverage include SST, orbital velocity, air temperature, air-sea temperature differential, and the cross SST gradient wind. Sampling and performance ranking techniques to manage large datasets are presented along with function fitting techniques for a modified power law. The improved understanding of whitecap coverage aids in estimating whitecap coverage globally using satellite products and in determining the global effects of whitecaps on air-sea processes and remote sensing of the surface.