Effect of surface waves on air–sea momentum flux in high wind conditions for typhoons in the South China Sea

The WAVEWATCH-III wave model is implemented in the South China Sea to investigate the air–sea momentum flux in high wind conditions during 23 passages of typhoon occurred in 2005. The wave model is driven by the reanalyzed surface winds assimilated by several meteorologic data sources. The friction velocity was calculated and the relationships between different air–sea momentum parameters were studied. The results show that the drag coefficient decreases with the wave age generally and levels off for wind speeds higher than 35 m/s under typhoon wind forcing. The spatial variations of air–sea momentum flux parameters in high wind conditions forced by typhoons are completely different from those at weak wind speeds and significantly depend on the relative position from the typhoon center.