Topographic Signatures in Aquarius Radiometer and Scatterometer Response

Theory suggests that topography (large-scale roughness) will affect thermal emission at L-band and could impact remote sensing of surface parameters, such as soil moisture from space. Evidence is presented here for the existence of effects due to topography using data from the L-band radiometers and scatterometer aboard the recently launched Aquarius. The correlation with the slope standard deviation at the topographic scale is presented for data over North Africa and Australia. In the case of the radiometer, brightness temperature is observed to increase at horizontal polarization and decrease at vertical polarization. In the case of the scatterometer, an increase with topographic roughness is observed for both polarizations. The presence of the scatterometer provides an independent verification that the behavior observed is due to topography and the observations are consistent with predictions based on Monte Carlo simulations.