Wind wave breaking and aerodynamic roughness of the air-sea interface as seen from above and from below

In this paper an attempt is made to explain some of the features of classical aerodynamic classification based on the effect of mobility of roughness elements (Kitaigorodskii 1968) for both sides of the air-sea interface by incorporating into such a classification the effect of breaking wind waves. Also the \fluctuating\ regime of the sea surface roughness discussed by Toba et al. (1991) is explained by taking into account the existence of the dissipation subrange (Kitaigorodskii 1983, 1986, 1992a, 1992b, 1997) and the inverse cascade of energy in the well developed wind wave field (Zaharoff and Zaslavskii 1982, and Kitaigorodskii 1983). In the last section of the paper a theory is proposed on how to incorporate the effect of wave breaking in the parametrization of the sea surface roughness as seen from below. It is shown that aerodynamically smooth conditions in the classical sense never exist below the sea surface, since effective turbulent viscosity due to shear free turbulence generated by wave breaking is much larger than molecular viscosity.