(1) Cemagref de Montpellier , UMR TETIS Territoires, - PowerPoint PPT Presentation

Characterizing the quality of river water level time series Characterizing the quality of river water level time series derived from satellite radar altimetry: derived from satellite radar altimetry: Efforts toward a standardized methodology Efforts toward a standardized methodology Nicolas BERCHER (1), Pascal KOSUTH (1), Jérôme BRUNIQUEL(2) (1) Cemagref de Montpellier , UMR TETIS « Territoires, Environnement, Télédétection et Informations (1) Cemagref de Montpellier , UMR TETIS « Territoires, Environnement, Télédétection et Informations Spatiales », Spatiales », nicolas.bercher@teledetection.fr ; pascal.kosuth@teledetection.fr nicolas.bercher@teledetection.fr ; pascal.kosuth@teledetection.fr (2) Alcatel Alenia Space, Toulouse, France (2) Alcatel Alenia Space, Toulouse, France jerome.bruniquel@space.alcatel.fr jerome.bruniquel@space.alcatel.fr

“Quality” of river water level time series derived from satellite radar altimetry Quality” of river water level time series derived from satellite radar altimetry “ Introduction: Expectations by hydrologists Building time series of water levels from satellite radar altimetry “Quality” of sampled measurements ( accuracy + effective sampling frequency ) Method for quantification of the “Quality” : accuracy and effective sampling period Influence of river width “ex ante” quantification of the accuracy “Accuracy” of reconstructed river water level time series Oversampling : building a “continuous” time series from satellite sampling Coupled influence of measurement accuracy and effective sampling frequency and influence of river hydrology Method for characterization of the quality of oversampled time series (reconstructed daily time series) “ex ante” quantification of the accuracy ESA – CNES “15 years of progress in radar altimetry” Symposium – Venice – March 2006 ESA – CNES “15 years of progress in radar altimetry” Symposium – Venice – March 2006 Characterizing the quality of river water level time series derived from satellite radar altimetry Efforts toward a standardized methodology Bercher N;, Kosuth P., Bruniquel J. Bercher N;, Kosuth P., Bruniquel J. Characterizing the quality of river water level time series derived from satellite radar altimetry Efforts toward a standardized methodology

“Quality” of river water level time series derived from satellite radar altimetry Quality” of river water level time series derived from satellite radar altimetry “ Introduction (1/3) - Expectations by Hydrologists Radar Altimetry In situ measurements : measurements : ● twice a day, ● 10 to 35 days (theoretical), ● accuracy : ~3 cm ● accuracy : unknown ESA – CNES “15 years of progress in radar altimetry” Symposium – Venice – March 2006 ESA – CNES “15 years of progress in radar altimetry” Symposium – Venice – March 2006 Characterizing the quality of river water level time series derived from satellite radar altimetry Efforts toward a standardized methodology Bercher N;, Kosuth P., Bruniquel J. Bercher N;, Kosuth P., Bruniquel J. Characterizing the quality of river water level time series derived from satellite radar altimetry Efforts toward a standardized methodology

“Quality” of river water level time series derived from satellite radar altimetry Quality” of river water level time series derived from satellite radar altimetry “ Introduction (2/3) - Expectations by Hydrologists Radar altimetry Ra Ra d d a a r Altim r Altim e e try try m m e e a a s s u u re re m m e e n n ts ts : : In situ measurements : measurements ● twice a day, 1 1 0 0 to to 3 3 5 5 d d a a ys ys (th (th e e o o re re tica tica l), l), ● 10 days or 35 days ● accuracy : ~3 cm a a ccu ccu ra ra cy : u cy : u n n kn kn o o w w n n ● with quantified accuracy ● reconstructed daily time series ● with quantified accuracy Methods to characterize the “Quality” of water levels from radar altimetry accuracy and effective sampling frequency of radar altimetry Reconstruction of daily time series ; Resulting accuracy of daily time series Factors affecting the quality of reconstructed time series ESA – CNES “15 years of progress in radar altimetry” Symposium – Venice – March 2006 ESA – CNES “15 years of progress in radar altimetry” Symposium – Venice – March 2006 Characterizing the quality of river water level time series derived from satellite radar altimetry Efforts toward a standardized methodology Bercher N;, Kosuth P., Bruniquel J. Bercher N;, Kosuth P., Bruniquel J. Characterizing the quality of river water level time series derived from satellite radar altimetry Efforts toward a standardized methodology

“Quality” of river water level time series derived from satellite radar altimetry Quality” of river water level time series derived from satellite radar altimetry “ Introduction (3/3) - Building time series of water levels from satellite radar altimetry One satellite overflight Topex/Poseido n track 63 Satellite Retracking Algorithm + corrections Window size Selection of a unique value per cycle CAUTION : Internal dispersion of radar altimetry measures within the window during a cycle ESA – CNES “15 years of progress in radar altimetry” Symposium – Venice – March 2006 ESA – CNES “15 years of progress in radar altimetry” Symposium – Venice – March 2006 Characterizing the quality of river water level time series derived from satellite radar altimetry Efforts toward a standardized methodology Bercher N;, Kosuth P., Bruniquel J. Bercher N;, Kosuth P., Bruniquel J. Characterizing the quality of river water level time series derived from satellite radar altimetry Efforts toward a standardized methodology is not a quantification of the error

“Quality” of river water level time series derived from satellite radar altimetry Quality” of river water level time series derived from satellite radar altimetry “ Introduction: Expectations by hydrologists Building time series of water levels from satellite radar altimetry “Quality” of sampled measurements ( accuracy + effective sampling frequency ) Method for quantification of the “Quality” : accuracy and effective sampling period Influence of river width “ex ante” quantification of the accuracy “Accuracy” of reconstructed river water level time series Oversampling : building a “continuous” time series from satellite sampling Coupled influence of measurement accuracy and effective sampling frequency and influence of river hydrology Method for characterization of the quality of oversampled time series (reconstructed daily time series) “ex ante” quantification of the accuracy ESA – CNES “15 years of progress in radar altimetry” Symposium – Venice – March 2006 ESA – CNES “15 years of progress in radar altimetry” Symposium – Venice – March 2006 Characterizing the quality of river water level time series derived from satellite radar altimetry Efforts toward a standardized methodology Bercher N;, Kosuth P., Bruniquel J. Bercher N;, Kosuth P., Bruniquel J. Characterizing the quality of river water level time series derived from satellite radar altimetry Efforts toward a standardized methodology

“Quality” of river water level time series derived from satellite radar altimetry Quality” of river water level time series derived from satellite radar altimetry “ 89 165 241 63 139 215 178 254 76 152 228 50 102 ESA – CNES “15 years of progress in radar altimetry” Symposium – Venice – March 2006 ESA – CNES “15 years of progress in radar altimetry” Symposium – Venice – March 2006 Characterizing the quality of river water level time series derived from satellite radar altimetry Efforts toward a standardized methodology Bercher N;, Kosuth P., Bruniquel J. Bercher N;, Kosuth P., Bruniquel J. Characterizing the quality of river water level time series derived from satellite radar altimetry Efforts toward a standardized methodology

“Quality” of river water level time series derived from satellite radar altimetry Quality” of river water level time series derived from satellite radar altimetry “ Solimões River; Topex Poseidon; Track 63 Ma Ma na na us us Radar Altimetry Data / In situ data Error Error structure ESA – CNES “15 years of progress in radar altimetry” Symposium – Venice – March 2006 ESA – CNES “15 years of progress in radar altimetry” Symposium – Venice – March 2006 Characterizing the quality of river water level time series derived from satellite radar altimetry Efforts toward a standardized methodology Bercher N;, Kosuth P., Bruniquel J. Bercher N;, Kosuth P., Bruniquel J. Characterizing the quality of river water level time series derived from satellite radar altimetry Efforts toward a standardized methodology

“Quality” of river water level time series derived from satellite radar altimetry Quality” of river water level time series derived from satellite radar altimetry “ High flow Mean flow Low flow ESA – CNES “15 years of progress in radar altimetry” Symposium – Venice – March 2006 ESA – CNES “15 years of progress in radar altimetry” Symposium – Venice – March 2006 Characterizing the quality of river water level time series derived from satellite radar altimetry Efforts toward a standardized methodology Bercher N;, Kosuth P., Bruniquel J. Bercher N;, Kosuth P., Bruniquel J. Characterizing the quality of river water level time series derived from satellite radar altimetry Efforts toward a standardized methodology