Revised Estimates of Ocean Surface Drag in Strong Winds

Air-sea drag governs the momentum transfer between the atmosphere and the ocean and remains largely unknown in hurricane winds. We revisit the momentum budget and eddy covariance methods to estimate the surface drag coefficient in the laboratory. Our drag estimates agree with field measurements in low-to-moderate winds and previous laboratory measurements in hurricane-force winds. The drag coefficient saturates at 2.6x10(-3) and U-10 approximate to 25 m s(-1), in agreement with previous laboratory results by Takagaki et al. (2012,). During our analysis, we discovered an error in the original source code used by Donelan et al. (2004,). We present the corrected data and describe the correction procedure. Although the correction to the data does not change the key finding of drag saturation in strong winds, its magnitude and wind speed threshold are significantly changed. Our findings emphasize the need for an updated and unified drag parameterization based on field and laboratory data. Plain Language Summary We measure the rate of air-sea momentum transfer (surface drag) in strong winds in a 15-m-long wind-wave tank. In support of previous work, we find further evidence that the drag saturates (levels off) in hurricane force winds, based on three different measurement methods. The level of drag saturation, however, is higher than previously thought. The leading study that discovered the drag saturation in high winds had an error in the source code used for the analysis of the data. This error resulted in an overestimate of 10-m wind speed and an underestimate of the drag coefficient. This finding is important because previous laboratory data that underestimate the drag were used to implement surface flux parameterization in the most widely used research and operational weather prediction model for tropical cyclone applications.