On Detection of a Wave Age Dependency for the Sea Surface Roughness

Abstract

From an empirical fit to measurements from RASEX together with other previously measured data sets they find the coefficients A=1.89 and B=1.59. One of the main problems in these results was the conflicting, apparent trend of decreasing Charnock parameter with inverse wave age in the RASEX data set taken alone (see also Taylor and Yelland (2001)). The problem with this kind of scaling is that the two quantities z ch and wave age, between which a functional relationship is proposed, are not independent of each other. This can lead to self-correlation problems, i.e. the functional relationship might be distorted or even determined by the common scaling variable. A theoretical analysis of the self-correlation problem has been presented by Hicks (1978) and specifically for the question of wave age dependent Charnock parameter by Smith et al. (1992). The latter group concluded that self-correlation had an influence on the results of the HEXOS data. JHVL98 generalised that this will always be the case for a

Importance of thermal effects and sea surface roughness for offshore wind resource assessment

“…The more complex sea surface roughness models based on wave age dependency were found to actually increase the prediction error. The reason might be that the wave age dependency of the Charnock parameter suffers from self-correlation problems [33].…”

On the Exchange of Momentum over the Open Ocean

“…Johnson et al (1998) argued that this effect could be reduced by comparing the mean results from several sites with different fetches, such that their coefficients are derived from a fit to the mean phase speed and Charnock coefficients from a number of different field experiments. This analysis relies on the wide range of wage ages captured during CBLAST and CLIMODE deployments and, to a lesser extent, the wind event captured during the MBL experiment to reduce the problem of selfcorrelation (Donelan et al 1992;Lange et al 2004;Drennan et al 2005). The Charnock coefficient is computed using individual estimates of the drag coefficient and friction velocity using steps 5) and 6) as in section 2c.…”

AutoFlux: an autonomous system for the direct measurement of the air-sea fluxes of CO2, heat and momentum

“…In addition, the influence of sea state on the momentum flux is still hotly debated and is thought to be particularly large in coastal regions. 4,5,6 The heat fluxes are reasonably well understood but uncertainties of about 20% exist in their parameterisations in terms of mean variables. In addition, the variation of the heat transfer coefficients with wind speed is still subject to debate.…”