Observation and analysis of the influence of wind waves on air-sea momentum fluxes

Due to the long-standing lack of understanding the role of wind waves on wind stress at moderate to high wind speeds, a high-frequency turbulence observation system is used in this study to obtain air-sea momentum flux data under pure wind wave conditions based on the tower-based marine meteorological observation platform in the southern Bohai Sea. Moreover, the modulation of wind waves on wind stress under wind speeds greater than 10 m s(-1) is analyzed. The results indicated that the wind wave states caused by winds from the northwest and northeast are different under the influence of cold air, resulting in different wind stresses and drag coefficients. The wind stress increases with an increasing wind speed, reaching its maximum value when the northwest wind is nearly 20 m s(-1), while the extreme value of the drag coefficient is basically the same when the northwest wind speed is the maximum and the northeast wind wave significant wave height is the maximum. The drag coefficient increases with an increasing wind speed within the range of 10-15 m s(-1), reaching saturation at 15 m s(-1). The critical wind speed is smaller than other observed results. Further analysis showed that wind-induced turbulent stress deviates from the observed values, and the degree of deviation depends on the wind speed and wave state, with a greater deviation caused by strong winds and waves. The wave-induced stress can correct the negative deviation between wind-induced turbulent stress and the observed value, and the drag coefficient calculated based on the modified wind stress tends to be close to the observed value overall.