Estimates of the 10-m Neutral Sea Surface Drag Coefficient from Aircraft Eddy-Covariance Measurements

Abstract

he 10-m neutral drag coefficient (CDN10) over the sea is calculated using a large observational dataset consisting of 5800 estimates of the mean flow and the fluxes from aircraft eddy-covariance measurements. The dataset includes observations from 11 different experiments with four different research aircraft. One of the goals is to investigate how sensitive CDN10 is to the analysis method. As such, CDN10 derived from six unique processing schemes that involve different methods for averaging the surface stress and the wind speed are compared. Especially in weak winds, the resulting CDN10 values depend on the choice of processing.Four distinct regimes of CDN10 are identified: weak winds where calculating CDN10 is not well posed, moderate winds (4 to 10 m s?1) where CDN10 is a constant, strong winds (10 to 20 m s?1) where CDN10 increases linearly with increasing wind speed, and very strong winds (20 to 24 m s?1) where CDN10 steadily decreases with increasing wind speed. However, as this last regime is based on data from a single experiment, additional data are needed to confirm this apparent decrease in CDN10 for winds exceeding 20 m s?1.