Evidence for complete and partial surface renewal at an air-water interface

A wind-wave flume is used to determine the extent to which the thermal boundary layer (TBL) at a wind-forced air-water interface is completely renewed from below. We measure skin temperature, T-skin, radiometrically, temperature immediately below the TBL, T-subskin, using a temperature profiler, and net heat flux using the gradient flux technique. The T-skin probability density function, p(T-skin), and surface renewal time scale, tau, were measured using passive and active infrared imaging techniques, respectively. We find that the mean percentile rank of T-subskin in p(T-skin) is 99.90, implying that complete surface renewal occurs. This result suggests an alternative to radiometric measurement of T-skin through the simple combination of an infrared camera and an in situ temperature sensor. Comparison of the temperature difference across the TBL to the expected cooling implies that a significant portion of events only partially renew the TBL. This result should impact efforts to improve air-sea transfer models. Citation: Jessup, A. T., W. E. Asher, M. Atmane, K. Phadnis, C. J. Zappa, and M. R. Loewen (2009), Evidence for complete and partial surface renewal at an air-water interface, Geophys. Res. Lett., 36, L16601, doi: 10.1029/2009GL038986.