Louisiana Wetland Water Level Monitoring Using Retracked TOPEX/POSEIDON Altimetry

Abstract

Previous studies using satellite radar altimetry to observe inland river and wetland water level changes usually spatially average high-rate (10-Hz for TOPEX, 18-Hz for Envisat) measurements. Here we develop a technique to apply retracking of TOPEX waveforms by optimizing the estimated retracked gate positions using the Offset Center of Gravity retracker. This study, for the first time, utilizes stacking of retracked TOPEX data over Louisiana wetland and concludes that the water level observed by each of 10-Hz data with along-track sampling of ∼660 m exhibit variations, indicating detection of wetland dynamics. After further validations using nearby river gauges, we conclude that TOPEX is capable of measuring accurate water level changes beneath heavy-vegetation canopy region (swamp forest), and that it revealed wetland dynamic flow characteristics along track with spatial scale of 660 m or longer.

Keywords:

• Satellite radar altimetry
• Louisiana wetlands
• water level change
• waveform retracking
• stackfile

Acknowledgments

This research is partially supported by grants from the National Geospatial-Intelligence Agency's University Research Initiatives Program: HM1582-07-1-2024, National Science Foundation Hydrology program: EAR-0440007, and the Climate, Water, and Carbon Program at the Ohio State University. The TOPEX/POSEIDON data products used in this study are from NASA/JPL PO-DAAC and CNES AVISO. We also thank two anonymous reviewers for their constructive comments which have improved the manuscript.