Spectral radiometric measurements of the temperature and radiation capacity of a rough sea surface

Abstract

The results of radiometric remote simultaneous field measurements of the temperature and radiation capacity of the upper layer of the sea-surface temperature film 0.2 mm thick are presented. The measurements were conducted in the presence of wind waves and were characterized by an increased accuracy, which was achieved owing to the use of measurements of the intensity of radio radiation from the surface illuminated by radiation of a specified varying power. In our experiment, this illumination was provided by the radio radiation of the atmosphere, whose radiance temperature varies significantly, depending on the frequency at the slope of the absorption band of molecular oxygen (52.5–56 GHz). As a result, the radiation capacity and temperature of the skin layer were determined from the correlation dependence between the radiance temperatures of the surface and atmosphere measured by a radiometer-spectrometer in a number of channels separated in frequency. The radiance temperatures of the sea and atmosphere were measured at four frequencies of the 5-mm spectral range (53–55 GHz) on a vertical polarization. For absolute measurements, a calibration method was developed on the basis of a blackbody disk and two reflecting mirrors with the same solid angles. The measured values of the radiation capacity are variable and substantially smaller than the theoretical values determined by the models accepted for the permittivity of water and sea roughness. A possible cause of this can be the change of the permittivity of water in a thin surface layer of the temperature film (0.2 mm) due to the concentration of gases dissolved in water and surface-active substances within this layer.