Abstract
When the wind blows across the water, a highly sheared current develops which extends a few millimeters into the water and amounts, at the surface, to 3–4% of the wind speed. Banner and Phillips (1974) have pointed out that the wind drift, as this thin surface current layer is called, may he sufficiently augmented by interaction with the orbital velocity field of the wave that the maximum particle speed may exceed the phase speed and the wave breaks. If a longer gravity wave is also present, the wind drift may be further augmented and the short gravity wave may break prematurely. We have examined both the basic breaking condition and the diminution (straining) of the short gravity waves by longer waves experimentally in wave tanks. We find that actual wave breaking occurs at substantially higher winds than predicted and that the diminution is substantially less at the higher winds. The observed wind speed dependence of this diminution appears to be contrary to prediction and points to direct coupling between wind and short gravity waves as an important factor in the response of these waves to straining.
