Microwave Model of Radiation From the Multilayer ``Ocean-Atmosphere'' System for Remote Sensing Studies of the Polar Regions

Abstract

Abstract-Microwave model for simulation of radiation from the multilayer system "sea surface-sea icesnow cover-atmosphere" is introduced. In the general case, ice and snow cover is modelled by multilayer medium, where every layer is characterized by its specific physical parameters. Electrodynamical properties of each layer are determined from the original authors' model of the effective permittivity of heterogeneous medium. This model takes into account effects of radiation scattering on irregularities of environment. Measurable physical characteristics of sea ice and snow are used as the model input data. This advantage allows using this model for interpretation of remote sensing images of the ice cover in the Polar Regions. Major attention is drawn to comparison of model calculations with satellite data and visual observations from ships. The collection of SSM/I and SSMIS images from GLOBAL-RT data base, and processed visual observations from ships in Arctic cruises were used. Observations data served as the input parameters for electrodynamical model. Comparison of model results with SSM/I images demonstrated good coincidence at various frequencies.

A physical algorithm to measure sea ice concentration from passive microwave remote sensing data

“…The appearance of liquid water in snow leads to considerable increase of the real and imaginary parts of wet snow dielectric constant in the microwave range. These dependencies are identical in shape to those of the real and imaginary parts of water (Tikhonov et al, 2014). Therefore, the emissivity of wet snow is determined primarily by the volumetric content of liquid water in the snow (Boyarskii and Tikhonov, 2000;Matzler and Huppi, 1989).…”

“…The low-frequency bands (19.35 and 37 GHz) are more sensitive to volumetric scattering in snow and ice covers (Andersen et al, 2007;Boyarskii et al, 1994;Boyarskii and Tikhonov, 2000). This is explained by a greater penetration depth at these frequencies (Tikhonov et al, 2014) and dimension similarity between inhomogeneities and emission wavelength (Boyarskii et al, 1994;Boyarskii and Tikhonov, 2000). Horizontal polarization bands are more sensitive to stratification of snow cover and sea ice (Andersen et al, 2007).…”

“…The analysis of the model calculations of ice cover brightness temperature in the Arctic and their comparison with the SSM/I (Special Sensor Microwave/Imager) and SSMIS (Special Sensor Microwave Imager Sounder) data (Tikhonov et al, 2013(Tikhonov et al, , 2014 have shown that the sought parameters may be tangents of the angles between the lines drawn through the brightness temperature values at two different frequencies of the same polarization and the frequency axis: …”

“…The principal feature of this algorithm is that it is based on a theoretical model of emissivity of the system "sea surface -sea ice -snow cover -atmosphere", not just experimental data (Tikhonov et al, 2014). The model includes: emission model of a layered medium (Sharkov, 2003), a model of dielectric properties of ice and snow (Boyarskii et al, 1994;Tikhonov et al, 2014), a standard atmosphere model (Tikhonov et al, 2014), a model of surface roughness in the microwave range (Choudhury et al, 1979). Antenna pattern and radiometer bandwidth were taken into account in the model calculations.…”

“…Emissivity of such extended area is determined not only by the ice type, but also the surface roughness and snow cover. Theoretical estimates demonstrate that dry snow penetration depth at frequencies over 19 GHz is less than 40 cm (Tikhonov et al, 2013(Tikhonov et al, , 2014. Therefore, a layer of snow on ice will change considerably the brightness temperature difference between multiyear and first-year ice.…”