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Recent investigations using polarimetric decomposition and numerical models have helped to improve the understanding of how radar signals interact with lake ice. However, further research is needed on how radar signals are impacted by varying lake ice properties. Radiative transfer (RT) models provide one method of improving this understanding. These are the first published experiments using the snow microwave RT (SMRT) model to investigate the response of different frequencies (L-, C-, and X-band) at horizontal-horizontal (HH) and vertical-vertical (VV) polarizations using various incidence angles (20°, 30°, and 40°) to changes in ice thickness, porosity, bubble radius, and ice–water interface roughness. This is also the first use of SMRT in combination with a thermodynamic lake ice model. Experiments were for a lake with tubular bubbles and one without tubular bubbles under difference scenarios. An analysis of the backscatter response to different properties indicates that increasing ice thickness and layer porosity have little impact on backscatter from lake ice. X-band backscatter shows increased response to surface ice layer bubble radius; however, this was limited to other frequencies except at shallower incidence angles (40°). All three frequencies display the largest response to increasing root mean square (rms) height at the ice–water interface, which supports surface scattering at the ice–water interface as being the dominant scattering mechanism. These results demonstrate that the SMRT is a valuable tool for understanding the response of backscatter to changes in freshwater lake ice properties and could be used in the development of inversion models. [ABSTRACT FROM AUTHOR]

Polarimetric synthetic aperture radar satellite and ground-based Ku- and X-band scatterometer measurements are used to explore the scattering mechanism for ice in shallow Arctic lakes, wherein strong radiometric responses are seen for floating ice, and low returns are evident where the ice has grounded. Scatterometer measurements confirm that high backscatter is from the ice/water interface, whereas polarimetric decomposition suggests that the dominant scattering mechanism from that interface is single bounce. Using Fresnel equations, a simple model for surface bounce from the ice/water interface is proposed, and its predictions are supported by experimental parameters such as co-pol phase difference, co-pol ratio, and the results of rigorous numerical modeling. Despite early research suggesting double-bounce scattering from columnar air bubbles and the ice/water interface as the dominant scattering mechanism in shallow lakes, this paper strongly supports a single-bounce model. [ABSTRACT FROM PUBLISHER]

This study is the first assessment of winter season backscatter (\boldsymbol\sigma^\circ ) evolution for snow-covered lake ice observed by X- (9.6 GHz) and Ku-band (17.2 GHz) ground-based scatterometers (UW-SCAT), collected during the Canadian Snow and Ice Experiment in 2010–2011. The \boldsymbol\sigma^\circ evolution of three ice cover scenarios is observed and simulated using a bubbled ice \boldsymbol\sigma^\circ model. The range resolution of UW-SCAT provides separation of interaction at the snow–ice interface (P1), and within the ice volume and ice–water interface (P2). Ice cores extracted at the end of the observation period indicate a P2 \boldsymbol\sigma^\circ increase of approximately 10–12 decibels (dB) (HH & VV) at X- and Ku-band coincident to tubular bubble development. Similarly, complexity of the ice surface (gray ice) results in increased P1 \boldsymbol\sigma^\circ (\sim\mathbf7\;\mathbfdB). P1 observations indicate that Ku-band is sensitive to snowpack overlying lake ice, with \boldsymbol\sigma^\circ exhibiting a 5 (6) dB drop for VV (HH) when 0.235 m snow is removed. X-band is insensitive to changes in overlying snowpack. A bubbled ice \boldsymbol\sigma^\circ model is presented using dense medium-radiative transfer theory under the quasi-crystalline approximation (DMRT-QCA), which treats bubbles as spherical inclusions within an ice volume. Model runs demonstrate the capability of DMRT to produce observed \boldsymbol\sigma^\circ magnitude using snow and ice observations as input. This study improves the understanding of microwave interaction with bubbled ice near the surface or within the volume. Results from this study indicate that further model development involves bubble shape modification within the ice from spherical to tubular. [ABSTRACT FROM PUBLISHER]