SAR Mode Altimeter for Monitoring In-Land Hydrology
Moreau, Thomas¹; Thibaut, Pierre¹; Mercier, Franck¹; Boy, Francois²; Picot, Nicolas²; Nino, Fernando³; Calmant, Stephane³; Cretaux, Jean-François³; Bercher, Nicolas^3
1CLS, FRANCE; ²CNES, FRANCE; ³LEGOS, FRANCE

Even if devoted to ice monitoring, the ESA Cryosat-2 mission offers the first opportunity to map in-land hydrological targets with a SAR-mode altimeter sensor. Taking advantages of the SAR-mode performance enhancements, such as noise reduction and finer along track spatial resolution compared to those typically seen with conventional radar altimeters like Jason-2 and/or ESA ENVISAT mission, hydrological sites of interest will be investigated in more depth than ever before. The enhanced resolution, the reduced land contamination due to the SAR altimeter footprint size and the dedicated ground processing methods (Hamming weighting, focus on inland water bodies, stacking, ...) will improve the mapping scene of rivers and lakes and give a more detailed access to the geometry and surface area of the water bodies. In addition, the improved range precision will allow extracting river and lake heights at higher accuracy. It makes the SAR-mode altimeter very useful in land hydrology to, for example, observe the storage and discharge rates of land water bodies, where conventional altimeters products are impacted by the large footprint size. It is also of high importance for Sentinel-3 mission, and SWOT at a later time, to provide a significant increase in our monitoring capabilities of continental water bodies even before the launch of these satellites and to develop suitable processing methods. In this context, CLS is conducting a study in partnership with CNES altimeter processing and LEGOS experts to optimize the potential of SAR-mode data in hydrological applications, by developing new methodologies in data processing and analysis.
We will present our processing method and a first validation will be performed thanks to a comparison with conventional radar altimeters data (Jason-2, ENVISAT, ...). The noise reduction will be particularly analyzed. In addition, a comparison to insitu data and to the LEGOS HydroWeb database will be presented.