A Look at Amazon Basin Seasonal Dynamics with the Biophysical ...

Surface Water Dynamics in the Amazon Basin:Application of Satellite Radar AltimetryC.M. Birkett 1 , L.A.K. Mertes 2 , T. Dunne 3 , M.H. Costa 4 , M.J. Jasinski 51 Universities Space Research Association, NASA/GSFC, Maryland, USA2 Department of Geography and ICESS, University of California at Santa Barbara, USA3 Bren School of Environmental Science and Management and ICESS, University of California atSanta Barbara, USA4 Department of Agricultural Engineering, Federal University of Viçosa, Brazil5 Hydrological Sciences Branch, NASA/GSFC, Maryland, USAAbstract. Satellite radar altimetry has the ability to monitor variations in surface water height(stage) for large wetlands, rivers, and associated floodplains. A clear advantage is the provisionof data where traditional gauges are absent. As part of an international programme a completealtimetric analysis of the Amazon Basin is being undertaken. Here, an updated and more rigorousevaluation of the TOPEX/POSEIDON (T/P) dataset is presented for the first ~7.5 years of themission. With an initial study group of 230 targets, height variability at many ungauged locationscan be observed for 30-50%, the range reflecting the clarity of the variations in lieu of instrumentlimitations. An assessment of the instrument performance confirms that the minimum river widthattainable is ~1 km in the presence of some inundated floodplain. This constraint does allowobservation of the main stem (Solimões/Amazon) and the larger tributaries, but rugged terrain inthe vicinity of the target additionally places severe limitations on data retrieval. First-ordervalidation exercises with the deduced 1992-1999 time series of stage fluctuations revealaccuracies ranging from tens of centimeters to several metres (mean ~1.1 m rms). Altimetricwater levels in the Solimões and Amazon are particularly well defined with amplitudes