Normalizing flux coefficients for stratification, homogeneity, and stationarity

Monin-Obukhov similarity theory is routinely applied over the ocean, in order to describe surface layer profiles of windspeed, temperature, and gas concentrations. Using this theory, fluxes are in turn estimated based on the best available parameterizations of normalized flux coefficients, e.g., the neutral flux coefficients; flux coefficients can vary according to different environmental conditions. Since it is generally assumed that the domain of interest must be characterized by spatially homogeneous and steady state conditions, systematic violations of the assumptions may lead to significant uncertainties in flux estimates. In this paper, MOS theory is extended in order to accommodate nonstationarity and spatial inhomogeneity in the representation of the normalized drag coefficient, Stanton number, and Dalton number. We illustrate the importance of our theoretical extension, based on a re-examination of a historical air-sea interaction data set obtained from the North Sea.