Sea Surface Drag Fluctuation in Relation to the Saturation Ratio of Wind Wave Spectrum

A new linear relation between sea surface drag coefficient and the saturation ratio of wind wave spectrum was obtained. The theory is based on the 3/2 power law of wave heights and periods, which was proposed by Toba (1972). The saturation ratio of wind wave spectrum is calculated by using spectrum analysis in principle, however a new parameter derived by the 3/2 power law gives us a saturation ratio from significant wave height and period instead of spectrum analysis. It is found that the negative correlation between sea surface drag and saturation ratio of wind wave spectrum exists. The relation can be explained that the saturated wind wave conditions reduce the momentum exchange from wind to wave, so the sea surface drag reduce in proportion to the momentum exchange.