Whitecaps and the passive remote sensing of the ocean surface

Abstract

Whitecap coverage (W), which influences the apparent microwave brightness temperature and short-wave albedo of the sea surface, is not only a strongly non-linear function of the l0m-elevation wind speed (U), but also varies with changes in the stability of the lower atmosphere (i.e. with alterations in the water-air temperature difference AT), and with changes in the surface-sea water temperature (Tw). Thus wind retrieval algorithms to be applied to open ocean data from whitecap-detecting satellite instruments should ideally be of the form, U(W, δT, Tw, d), where d is a measure of the effective wind duration. The wind speed associated with the onset of whitecapping, while also varying with AT and Tw, is typically 3 to 3-5ms-1, not the often quoted 7ms-1