Millimeter-Wave Radiometry of the Temperature Film on a Sea Surface

Using in-situ measurements of thermal radio emission at frequencies 53–55 GHz from a rough sea surface in the coastal zone of the eastern Crimea shore, we obtain data on the water temperature at a depth of 0.2 mm and on the reflection characteristics of the sea surface. Measuring the intensity of radio emission from a surface irradiated by a signal with known variable power allows one to obtain simultaneous data on the temperature and reflection coefficient. In our experiment, the atmospheric radio emission in the wing of the molecular oxygen absorption band, received by frequency-separated channels of a radiometer–spectrometer, plays the role of such an irradiation. The measured water temperature T_SL=(5.4±1.0) °C turns out to be less than the air temperature and the in-depth water temperature. The reflection coefficient is equal to R=0.349±0.05.