An improved method for downscaling soil moisture retrieved by SMOS with MODIS LST/NDVI

Abstract

One main objective of Soil Moisture and Ocean Salinity (SMOS) is to provide observations of global soil moisture. The resolution of L-band radiometer carried by SMOS is about 50 km resolution, which is rather coarse for many applications. The method based on `universal triangle' has been used on downscaling soil moisture retrieved by SMOS with L-band brightness temperature. Consider the senor carried by SMOS is the L-band multi-angular dual polarization radiometer, this paper presents an improved method for downscaling Centre Aval de Traitement des Données SMOS (CATDS) L3 soil moisture by using MODIS Land Surface Temperature (LST) /NDVI and SMOS dual polarization brightness temperature. Southwest of China is selected as the study area and ground based soil moisture from Maqu monitor network is used to compare with the SMOS CATDS soil moisture at 25 km and the downscaled soil moisture. The results show that the improved method could improve the result with R <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> from 0.15 to 0.25. High resolution brightness temperature used in the method is obtained from SMOS CATDS brightness temperature at 25 km and causes error during the experiment.