Journal article

On the variability of the Charnock constant and the functional dependence of the drag coefficient on wind speed: Part II-Observations

John AT Bye, Joerg-Olaf Wolff, Karsten A Lettmann

OCEAN DYNAMICS | SPRINGER HEIDELBERG | Published : 2014

Abstract

An analytical expression for the 10 m drag law in terms of the 10 m wind speed at the maximum in the 10 m drag coefficient, and the Charnock constant is presented, which is based on the results obtained from a model of the air-sea interface derived in Bye et al. (2010). This drag law is almost independent of wave age and over the mid-range of wind speeds (5-17 ms-1) is very similar to the drag law based on observed data presented in Foreman and Emeis (2010). The linear fit of the observed data which incorporates a constant into the traditional definition of the drag coefficient is shown to arise to first-order as a consequence of the momentum exchange across the air-sea boundary layer brough..

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Funding Acknowledgements

JATB gratefully acknowledged the award of a Fellowship at the Hanse-Wissenschaftskolleg, Delmenhorst, Germany in the first half of 2013 during which this study was carried out in the Institute for Chemistry and Biology of the Sea (ICBM), University of Oldenburg. Helpful comments by two referees, especially with regard to the presentation of the theoretical results, are also gratefully acknowledged.