Mechanism of drag coefficient saturation at strong wind speeds. Issue 18 (28th September 2016)

• Record Type: Journal Article
• Authors: Takagaki, Naohisa; Komori, Satoru; Suzuki, Naoya; Iwano, Koji; Kurose, Ryoichi
• Is Part Of: Geophysical research letters. Volume 43:Issue 18(2016)
• Page Start: 9829
• Page End: 9835
• Publication Date: 2016-09-28
• Subjects: air‐sea interaction -- wind waves -- tropical cyclone; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1002/2016GL070666
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: Previous studies have demonstrated the saturation of drag coefficients at strong wind speeds. But the mechanism behind this saturation has not yet been fully clarified. In this study, at normal and strong wind speeds, we use a wind‐wave tank for investigating the peak enhancement factor of the wind‐sea spectrum, which is an appropriate wave parameter for representing interfacial flatness. We measured the water‐level fluctuation using wave gauges. At strong wind speeds, the result shows that the peak enhancement factor of the wind‐sea spectrum decreases with decreasing inverse wave age and with increasing wind speed. This suggests that the distinctive wind‐wave breaking occurs at strong wind speeds. It also suggests that this distinctive breaking of wind waves causes the saturation of drag coefficients at strong wind speeds. Key Points: The peak enhancement factor in a wind‐wave tank is measured New correlations about the peak enhancement factor of the wind‐sea spectrum are proposed Drag saturation at extremely high wind speeds is determined to be caused by distinctive wave breaking