The influence of air-water interface boundary conditions on thermal radio emission at 2, 5 and 8 mm

The influence of air turbulence and oil films on the thermal radio emission of water at mm wavelengths has been investigated. The investigation of the water near-surface thermal regime by one-wavelength radio brightness dynamics is especially interesting because temperature gradients in thin subsurface layers and evaporation from the water surface determine the heat exchange between ocean and atmosphere. The strong dependence of the radio brightness on the oil film thickness, which is due the interference of the thermal radio emission retroreflected at the interface, can be used to determine this parameter from radiometric data. Measurements have been carried out in the open air using a water pool with sizes 2, 1.5, and 0.2 m, three radiometers at wavelengths 0.23, 0.5 and 0.8 cm with horn nadir-looking antennae at 1 m above the water surface. The radiometer sensitivity was about 0.1 K. The diameter of the beam footprints on the water surface was about 10 cm