H221-03
Airborne Observations of Ka-band Radar Backscatter from AirSWOT Enable Vegetation and Water Detection
Thursday, 17 December 2020: 04:08
Virtual
Jessica V Fayne1, Laurence C Smith2, Marc Simard3, Kyle Cavanaugh1, Tien-Hao Liao4, Cheryl Doughty5, Lincoln H H Pitcher6, Ethan D. Kyzivat2, Michael W Denbina7, Curtis W. Chen8 and Brent A Williams9, (1)University of California Los Angeles, Los Angeles, CA, United States, (2)Brown University, Providence, RI, United States, (3)NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, United States, (4)California Institute of Technology, Pasadena, CA, United States, (5)University of California Los Angeles, Los Angeles, United States, (6)CIRES, Boulder, CO, United States, (7)NASA Jet Propulsion Laboratory, Pasadena, CA, United States, (8)JPL/NASA/Caltech, Pasadena, CA, United States, (9)JPL/NASA/Caltech, Pasadena, United States
Abstract:
Water surface inundation extent is a crucial parameter for measuring changes in water storage. Accurate measurement of extents for inland water bodies is complicated by emergent vegetation found in shallow and medium depth water bodies, as well as by inundated vegetation at the shoreline. Extents may be underestimated using optical imaging methods where vegetation density is high. Near-nadir, short-wavelength radar is sensitive to both small changes in surface water roughness and vegetation densities, enabling novel classification of inundation beneath vegetation. We use near-infrared optical camera imagery and 35.75 GHz Ka-band radar data, both collected with the NASA/JPL AirSWOT platform, over the Arctic-Boreal regions of Alaska and Canada as well as modeled Ka-band data to explore this sensitivity.
Ka-band backscatter coefficients extracted for different water surface textures such as open water and water mixed with dense/sparse vegetation provide support to our understanding of the varied contributors to the complex scattering patterns observed in real data. In the case of a smooth, specular water surface or dampened scattering from emergent vegetation, these scattering patterns have the potential to produce ‘dark water’, a phenomenon of low signal return that subsequently decreases the available data to measure water surface elevations (WSE) and extents accurately. The differences in vegetation fraction and type afford the Ka-band scattering the ability to provide additional information relating to the presence of wetland and emergent vegetation. Mapping vegetation presence through the use of Ka-band backscatter may effectively close the gap in global emergent vegetation observations from optical and long-wavelength radar data. Results from this study aim to support the processing and data production of future AirSWOT and SWOT InSAR data to produce more consistent WSE by reducing the influence of irregular surface textures, leading to more accurate water storage change estimates, as well as enabling the cataloging of short, emergent vegetation, which is particularly relevant for biogeochemical studies.
