A combination of a low 37 GHz brightness temperature and a negative 19 and 37 GHz spectral gradient can be an effective discriminant for frozen and thawed soil. SSM/I data for 1988 are used to study the freeze/thaw of soil in the Northern Tibetan Plateau, China. In this study, a previously derived freeze/thaw classification scheme was tested for this unique geographic location. It was found that the 37 GHz threshold needed to be refined for this region. It was also found that the 37 GHz emission is sensitive to the scattering centers embedded in the soil, which may account for the observed low brightness temperature. The selection of the 37 GHz brightness temperature threshold depends on the atmospheric and soil conditions inherent in a particular region.

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