Measurement of Inland Surface Water from Multi-mission Satellite Radar Altimetry: Sustained Global Monitoring for Climat
Multi-mission satellite radar altimetry makes a unique contribution to the monitoring of global inland surface water; existing datasets already allow derivation of decadal time-series over hundreds of targets worldwide. These data are utilised both for cl
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Measurement of Inland Surface Water from Multi-mission Satellite Radar Altimetry: Sustained Global Monitoring for Climate Change P.A.M. Berry and J. Benveniste
Abstract Multi-mission satellite radar altimetry makes a unique contribution to the monitoring of global inland surface water; existing datasets already allow derivation of decadal time-series over hundreds of targets worldwide. These data are utilised both for climate change research, to inform water resource management, and, in synergy with GRACE data, to examine time-varying gravity signatures from land surfaces and (potentially) measure sub-surface hydrological flow. As the number of gauged catchments continues to fall, the importance of a global remote sensing measurement capability becomes ever more critical. The key to unlocking this potential is to retrack the complex waveforms returned from inland water targets, to identify and discard echo components returned from targets not directly beneath the satellite, and to discriminate successfully between wet land and inundated surface. This paper presents a global assessment of current capabilities, showcases decadal time-series from past and current altimeters, and demonstrates the Near Real Time measurement capability now running for the ENVISAT RA-2 and soon for Jason-2 as an ESA pilot system, allowing users access to these data within 3 days of measurement. The enhancement of this unique capability anticipated from the series of proposed future missions (such as CryoSat-2 and Sentinel-3) is discussed, and the key contribution to global climate change monitoring is demonstrated.
P.A.M. Berry () E.A.P.R.S. Lab, Gateway House, De Montfort University, Leicester LE19BH, UK e-mail: [email protected]
29.1 Introduction Satellite radar altimetry has been used for more than a decade to measure inland water heights. From initial measurement of a few large lake targets (Guzkowska et al., 1990), the techniques have now been applied to many large water bodies (Berry, 2002; Maheu et al., 2003; Birkett et al.. 2002). A global evaluation of the current capability and future potential of this technique is clearly required.
29.2 Global Analysis To assess the extent to which viable data have been collected over inland water by current and past altimeters, a global analysis has been performed for TOPEX (Algiers, 1993; Callahan, 1993), ERS2 (Capp, 2001), EnviSat RA-2 (Benveniste et al., 2002) and Jason-1 (Zanife et al., 2004). A mask was created to select only those waveforms likely to have returned from an inland water target, and each waveform was analysed and, if valid (i.e., contained significant signal and the leading edge was successfully captured) was retracked. Time series of successfully captured waveforms and their retracked heights were then generated. Statistics were generated for all missions for all inland water crossings where time series could be created successfully. Criteria for judging “success” included the requirement that valid waveforms be present for at least 90% of crossings. The results are summ
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