Evaluation of frequencies for sea surface temperature and salinity measurements using passive microwave radiometers

Abstract

Theoretical investigations have been carried out for a proper choice of frequencies for measuring sea surface temperature and salinity, with passive Microwave Radiometers. The brightness, temperature and emissivity has been calculated using an improved model for the dielectric constant of sea water. This was developed by Klein et al. (1977) for frequencies below the X-band. A simple model of air-water interface, neglecting the atmospheric contribution has been used in this study. It was found that multifrequency microwave radiometer operating between 1 to 3 or 4 GHz is suitable for simultaneous measurement of sea surface temperature and salinity. For measurement of only sea surface temperature, frequencies between 4 to 7 GHz, with an optimum frequency around 4.5 GHz should be considered. Additional experimental investigation is needed to justify the use of frequencies below 10 GHz for sea surface temperature measurement, because of the atmospheric contribution to the brightness temperature. The need for accurate experimental measurement of dielectric constants has been pointed out, keeping in view the accuracy of present day microwave radiometers.