Comments on “On the Effect of Ocean Waves on the Kinetic Energy Balance and Consequences for the Inertial Dissipation Technique”

Abstract

Open ocean wind stress data obtained from the Southern Ocean (Yelland and Taylor 1996, henceforth YT) were found to be of significantly lower magnitude than collocated stress estimates derived from the operational wave model, WAMcy4, used at the European Centre for Medium-Range Weather Forecasts (ECMWF). Furthermore, the observations did not exhibit the wave age dependence predicted by Janssen (1989) and others (Yelland et al. 1998). Janssen (1999, henceforth J99) suggested that these differences were due to our use of the inertial dissipation (ID) rather than eddy-correlation (EC) method to determine the stress. Janssen argued that the neglect of the pressure fluctuation term in the turbulent kinetic energy budget would cause ID-derived stress data to be biased low for higher wind speeds and suggested a correction factor. In this comment we will argue that 1) the magnitude of our ID stress data is confirmed by EC data from the open ocean, 2) the height dependence of stress estimates predicted by J99 is not observed, and 3) our neglect of the pressure fluctuation term (as calculated by J99) would have enhanced rather than diminished the wave age dependency of our data, had any been present. We conclude that the suggested bias in ID stress estimates is not significant and that J99’s criticism of the ID method is not justified. The further implication is that the WAM-derived wind stress estimates were overestimated.