The 2D-PIV measurements were conducted to obtain air flow distributions above wind waves. Poisson equation was solved numerically to compute air pressure distributions by using the PIV measurement data. Low pressure distributions, less than 1013hPa, appear over a wave crest. High speed air flow over a wave crest makes air pressure decrease. Separation vortices on leeward surface also have low pressure values. The form drag was calculated by integrating of horizontal component of pressure resistance along wave surface. The frictional drag also was calculated in a similar way, using frictional resistance. The form drag is one order larger than the frictional drag. However, the averaged value of form drag is nearly equal to zero.
