Blocking spectra of wind waves

For description of the small-scale region of the spectrum of wind waves, th e concept of the "blocking" range is proposed in which the waves cease to t ake wind energy, and this energy is transferred to the surface drift curren t through wave crest breaking. It is shown that the general phenomenologica l balance equation for the spectrum of wind waves N(k) of the form dN/dt = P-o + P+ - P- yields two conditions P-o = 0 and P+ = P- in the blocking ran ge. The first condition makes it possible to determine an explicit form of the wave spectrum N(k) in the blocking range from the nonlinear interaction term P-o = P-o(N), and the second condition allows the determination of th e dissipation spectrum P-(k) in this range of scales. For weakly nonlinear waves, when P-o(N) is a four-wave nonlinear interaction term cubic in N, an explicit form of the blocking spectrum N(k) is found in the directional ap proximation. In the strongly nonlinear limit, the blocking spectrum N(k) pr oves to be consistent with the Phillips spectrum obtained for the saturatio n range from dimensional considerations.