Abstract
Abstract. The Snow Microwave Radiative Transfer (SMRT) thermal emission and backscatter model was developed to determine uncertainties in forward modeling through intercomparison of different model ingredients. The model differs from established models by the high degree of flexibility in switching between different electromagnetic theories, representations of snow microstructure, and other modules involved in various calculation steps. SMRT v1.0 includes the dense media radiative transfer theory (DMRT), the improved Born approximation (IBA), and independent Rayleigh scatterers to compute the intrinsic electromagnetic properties of a snow layer. In the case of IBA, five different formulations of the autocorrelation function to describe the snow microstructure characteristics are available, including the sticky hard sphere model, for which close equivalence between the IBA and DMRT theories has been shown here. Validation is demonstrated against established theories and models. SMRT was used to identify that several former studies conducting simulations with in situ measured snow properties are now comparable and moreover appear to be quantitatively nearly equivalent. This study also proves that a third parameter is needed in addition to density and specific surface area to characterize the microstructure. The paper provides a comprehensive description of the mathematical basis of SMRT and its numerical implementation in Python. Modularity supports model extensions foreseen in future versions comprising other media (e.g., sea ice, frozen lakes), different scattering theories, rough surface models, or new microstructure models.
Highlights
The number and diversity of spaceborne observations from passive and active microwave sensors over snow-covered regions has considerably increased over the last 3 decades
(2) To foster comparisons between Snow Microwave Radiative Transfer (SMRT) and other common existing models (MEMLS, dense media radiative transfer theory (DMRT)-QMS, and HUT), we provide language bindings to seamlessly run these models within SMRT, which use the prescribed snowpack in SMRT and collect results as if they were produced by SMRT
5 Conclusions A new radiative transfer model to simulate emission or radar echo from a snowpack has been presented in this paper
Summary
The number and diversity of spaceborne observations from passive and active microwave sensors over snow-covered regions has considerably increased over the last 3 decades. All examples mentioned above indicate a clear demand for a modular and extensible approach that unifies existing knowledge and facilitates efficient intercomparisons of model ingredients with particular focus on the representation of microstructure To this end we developed the Snow Microwave Radiative Transfer (SMRT) model as a versatile tool to compute backscattering and brightness temperature (active–passive mode) from multilayered media, composed of bi-continuous, random microstructures (typically snow or bubbly ice), overlying a reflective surface (typically soil, water, or ice). The originality of this new model is the flexibility for the user to select among various electromagnetic or microstructure formulations at different stages of the forward modeling problem. As a consequence of these decisions on design, the model is composed of a fixed architecture, described in Sect. 2.1, and many switchable formulations described in Sect. 2.2 and 2.3 and in Appendix A
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