  A formal averaging procedure over the air-sea interface is developed for both
momentum and enthalpy surface-transfer coefficients, C_D and C_K, in hurricane
conditions. This leads to splitting of both the transfer coefficients across
the total area of the sea surface, C_(D,K), into the sums of their partial
values over the foam-free, C_(D,Kw), and foam-covered, C_(D,Kf), fractions
weighted with foam- and water-coverage coefficients {\alpha}f and 1-{\alpha}f .
The transfer coefficients, C_(D,K) and C_(D,Kw), are estimated by measurements
in open-sea and in laboratory conditions, respectively, while the transfer
coefficients across the foam-covered fraction, C_(D,Kf), which cannot be
measured directly, are estimated from the splitting relations. Applying the
Monin-Obukhov similarity theory at the neutral stability atmospheric conditions
to the transfer coefficients, separately to the foam-free, the foam-covered,
and the total sea surfaces, yields the roughness lengths,
Z_(D,Kw),Z_(D,Kf),Z_(D,K). The study is aimed at explaining an anomalous
behavior of the momentum and enthalpy transfer coefficients, C_D and C_K, with
wind speed U10 under hurricane conditions, by the effect of the foam slipping
layer sandwiched between the atmosphere and the ocean.
