IMPACT OF TERRAIN TOPOGRAPHY ON RETRIEVAL OF SNOW WATER EQUIVALENCE USING PASSIVE MICROWAVE REMOTE SENSING

The current algorithms of retrieval of snow water equivalence (SWE) using passive microwave remote sensing is based on the linear brightness temperature difference. In the mountain areas, the topography affects the microwave signal received by the microwave radiometer by ways of changing the elevation and the radiation between the terrains. Accordingly it can exert some certain influences on the result of SWE using the current algorithms of the retrieval of SWE. In this paper, Guo's terrain correction algorithm (2009) of passive microwave remote sensing is applied to correct the brightness temperature globally at AMSR-E's frequencies which are used in the current algorithms of the retrieval of SWE. We evaluated the terrain impact on brightness temperature at 18.7 GHz and 36.5 GHz at each polarization and polarization difference, respectively. From our analysis, we could see that: at the global scale, Guo's terrain correction algorithm is sensible to the changes of the topography on brightness temperature; the influence of the terrain on the passive microwave brightness temperature is similar with at 18.7 GHz and 36.5GHz. The vertical polarization channels are apt to be greater than zero while the horizontal ones to be less than zero. From the analysis of Guo's terrain correction on Tb at 18.7 GHz and 36.5 GHz, brightness temperature differences of the same polarizations are better combination compared to that of the different polarizations. Most of the difference of SWE estimated on Jan. 2, 2009 after terrain correction could be 14 mm, and the maximum difference is up to 40mm.