Multifrequency Radiometric Method of the Temperature Profile Measurement in the Active Topsoil

Abstract

In this theoretical paper, we propose a method for measuring the temperature profile in the active topsoil of the Arctic tundra using observations of the brightness temperature for two different polarizations of the radiation at frequencies of 1.4, 6.93, 7.3, and 10.7 GHz. A multifrequency physical model of microwave emission of bare soil, a dielectric model of the Arctic tundra soil, and temperature profiles, which were measured in the active topsoil at the Toolik field station on the Alaska North Slope, were used to calculate the observed values of the brightness temperature. Temperature profiles were retrieved from the observed values of the brightness temperature in the approximation of a piecewise-linear profile of topsoil temperature during 2010–2011. Correlation analysis of the temperature profiles measured at the Toolik station and retrieved from the radiometric data has shown that in winter the error of measurement of the soil temperature at depths of 0.6 and 16.0 cm in terms of the variance (correlation coefficient) does not exceed 2.3 (0.98) and 7.2 (0.62°C), respectively. In summer, the error of measurement of the soil temperature using the radiometric method is two times less than in winter.