Variability of Arctic Sea Ice and Seawater Microwave Emissivities

In the paper, we analyze sea ice and seawater emissivities at frequencies of 6.9, 10.65, 18.7, 23.8, 36.5, and 89 GHz in vertical and horizontal polarizations in the Arctic seas. The radiation coefficients were calculated for the period from January 1 to December 31, 2020, using average daily AMSR2 (Advanced Microwave Scanning Radiometer) measurements and were based on the transport equation in the approximation of a nonscattering atmosphere using ERA5 reanalysis data for surface temperature and profiles of atmospheric meteorological parameters. To separate sea ice from seawater, a satellite sea ice concentration product of the University of Bremen was used. The results of this paper indicate a significantly greater variability of sea emissivity than described in the literature. The variability of the emissivity of the Arctic sea ice increases with frequency and at frequency of 89 GHz is twice as high as at frequencies of 18.7, 23.8, and 36.5 GHz.