International Journal of Remote Sensing

Passive microwave remote-sensing techniques can monitor surface soil freeze/thaw states at the frozen soil surface. Studies found that the negative spectral gradient at 19 and 37 GHz is a good criterion for the determination of frozen soil. To remove vegetation effects on soil microwave emission signatures, only vegetation attenuation was considered, omitting vegetation emission contributions. Studies on vegetation effects indicated that at high frequencies, scattering and attenuation effects should be considered. In this article, a matrix-doubling microwave emission model evaluated vegetation effects in a cold environment at 18.7 and 36.5 GHz. To verify the model, a multi-channel truck-mounted radiometer collected emission data at a young tree stand and a grass-like field in 2008. Comparisons between model simulations and field measurements corresponded well. The model then established an emission database of natural, vegetated surface in the freezing environment, matched with the τ–ω model (which is a zeroth-order microwave emission model) in the same environment using least-square error. The effective scattering and attenuation of vegetation at both frequencies in the freezing environment were retrieved.