Thermometric measurements of the molecular sublayer at the air-water interface

A series of measurements was conducted in the Air-Sea Interaction Saltwater Tank (ASIST) to study the response of the air-water interfacial molecular sublayer under various heat flux and wind speed conditions. In-situ gradients were measured with a platinum-plated tungsten wire microthermometer, which resolved the temperature of the thermally conductive sublayer. Air-sea heat flux was controlled by changing the air-water temperature difference (ΔT^AW) and the wind speed, and measurements were made for three ΔT^AW regimes over a range of wind speeds. A function was fitted to the measured temperature profiles as a way of extracting the boundary layer thickness in a consistent fashion, from which the λ coefficient after Saunders (1967) was computed. This dataset returned a mean λ coefficient of 2.4 ± 0.5, which was generally lower than previous studies, and was found to be independent of wind speed in the range of 1 to 9 ms^-1.