Open AccessOn the variability of sea drag in finite water depth
Author(s) -
Toffoli A.,
Loffredo L.,
Le Roy P.,
Lefèvre J.M.,
Babanin A. V.
Publication year - 2012
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2011jc007857
Subject(s) - wind speed , drag coefficient , drag , roughness length , parametric statistics , meteorology , environmental science , planetary boundary layer , parametrization (atmospheric modeling) , geology , boundary layer , wind wave , mechanics , atmospheric sciences , wind profile power law , physics , mathematics , radiative transfer , statistics , oceanography , quantum mechanics
The coupling between the atmospheric boundary layer and the ocean surface in large‐scale models is usually parameterized in terms of the sea drag coefficient, which is routinely estimated as a function of mean wind speed. The scatter of data around such parametric dependencies, however, is very significant and imposes a serious limitation on the forecasts and predictions that make use of sea surface drag parameterizations. The analysis of an atmospheric and wave data set collected in finite water depth at the Lake George measurement site (Australia) suggests that this variability relates to a number of parameters at the air‐sea interface other than wind speed alone. In particular, results indicate that the sea drag depends on water depth and wave steepness, which make the wave profile more vertically asymmetric, and the concentration of water vapor in the air, which modifies air density and friction velocity. These dependencies are used to derive parametric functions based on the combined contribution of wind, waves and relative humidity. A standard statistical analysis confirms a substantial improvement in the prediction of the drag coefficient and sea surface roughness when additional parameters are taken into account.