Wavelet analysis of the surface temperature field at an air-water interface subject to moderate wind stress

A new analysis methodology based on the wavelet transform is used to estimate the cross-wind scale statistics of high surface temperature events from two-dimensional infrared imagery. The method is applied to laboratory data obtained from an experiment conducted in 2001 at the University of Miami, Rosenstiel School of Marine and Atmospheric Science Air-sea Interaction Saltwater Tank (ASIST). For the case of positive heat flux, in which heat is transported from water to air and for all wind forcing conditions, results from the analysis of infrared images show that the number of high temperature events, when scanned in the cross-wind direction, occupies a wide range of scales. For all wind cases, at a low temperature fluctuation threshold, the number of high temperature events increases with increasing wavenumber (decreasing scale). As the temperature fluctuation threshold is increased, this distribution collapses around a characteristic scale. In addition, as the wind speed increases this scale decreases. The statistical scale results are shown to be consistent with estimates of streak spacing based on a standard parameterization of the turbulent dynamics as well as with the results from numerical experiments. Our results suggest that further statistical analysis may possibly allow for the estimation of wind stress from infrared imagery. (C) 2008 Elsevier Inc. All rights reserved.