Satellite-Scale Soil Surface Roughness Retrieval in the US Corn Belt

In croplands, the L-band terrestrial brightness temperature is a function of not only soil moisture and vegetation, but also time-varying soil surface roughness. Soil surface roughness changes in response to human activities, such as the planting of crops, soil tillage, and rainfall. We use in situ data from the South Fork SMAP Core Validation Site in the US Corn Belt to determine the magnitude and polarization dependence of the soil surface roughness signal at the satellite scale. We find that when crops are not present, soil surface roughness retrievals are larger than anticipated, and are effectively independent of polarization except for their largest values.