AN EVALUATION OF SOIL mOISTURE DOwNSCALING TECHNIQUES USING L-bAND AIRbORNE ObSERVATIONS

69 m7 The European Space Agency (ESA) will launch the Soil Moisture and Ocean Salinity (SMOS) mission in late 2009. This mission is aimed at monitoring, globally, surface soil moisture and sea surface salinity from radiometric L-band observations [1]. Soil moisture is a critical state variable of the terrestrial water cycle and the factor that links the global water, energy and carbon cycles. Currently there are not observing systems that monitor this key variable, being SMOS an unprecedented initiative to provide global soil moisture mapping. SMOS observations are expected to be highly accurate but, due to technological limitations, their spatial resolution is limited to 40-km. This resolution is adequate for many global applications but restricts the uses of the data in regional studies, where a resolution of 1-10 km is needed [2]. Specific disaggregation techniques using simulated SMOS brightness temperatures from the SMOS End-to-end Performance Simulator (SEPS) have been explored to address the possibility of improving the spatial resolution of future SMOS observations: In [3], deconvolution techniques using improved Wiener, Constrained Least Squares and wavelet filters that may include different levels of brightness temperature information in the simulator were presented. With these techniques, the product spatial resolution and radiometric sensitivity was improved in a 49% over soil pixels and in a 30% over sea pixels. However, despite the improvements, results are still far for the 1-10 km goal. Within the preparatory activities for the SMOS cal/val at the REMEDHUS soil moisture station network [4], a high resolution brightness temperature generator and a dedicated Level 2 Soil Moisture processor have been conveniently added to SEPS. Thereby downscaling techniques for improving the spatial resolution of SMOS soil moisture estimates using REMEDHUS high resolution in-situ ground measurements of soil temperature, vegetation canopy, and NDVI data could be developed. Several field experimental campaigns using the UPC Airborne RadIometer at Lband (ARIEL) have been conducted [5]. By using ARIEL airborne observations, this paper is devoted to evaluate and adjust soil moisture downscaling techniques The authors would like to thank J. Mart ́ınez, N. S ́anchez, C. P ́erez, and G. Baroncini from the Centro Hispanoluso de Investigaciones Agrarias (CIALE), University of Salamanca, for providing the REMEDHUS ground truth data. The work presented on this paper was AN EVALUATION OF SOIL mOISTURE DOwNSCALING TECHNIQUES USING L-bAND AIRbORNE ObSERVATIONS