A comparison of methods for estimating u_* from given u_z and air‐sea temperature differences

Abstract

This paper presents an objective assessment of four methods for estimating sea surface friction velocity u* from wind speed at height z, uz, and air‐sea temperature difference. The methods are compared by using the computed friction velocity as the normalization factor in parametric correlations of wind‐wave parameters with the wind and wave measurements made by NOMAD buoys in the Great Lakes. The results show that (1) wind profile parameters obtained from the four methods are generally comparable, (2) parametric correlations with parameters normalized by u* lead to significantly decreased percentage deviations over correlations normalized by uz, and (3) correlations based on u* derived from the four methods show nearly identical percentage deviations. The conclusions are that (1) u* normalization acts to eliminate the effect of atmospheric stability and (2) any of the four methods can be used effectively in practical applications.

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