How will radar layover impact SWOT measurements of water surface elevation and slope, and estimates of river discharge?

REMOTE SENSING OF ENVIRONMENT

卷:247

Article

Durand, Michael^1,2  Chen, Curtis³  de Moraes Frasson, Renato Prata^1,2,3  Pavelsky, Tamlin M.⁴  Williams, Brent³  Yang, Xiao⁴  Fore, Alex³ 

[1] Ohio State Univ, Sch Earth Sci, Columbus, OH 43214 USA

[2] Ohio State Univ, Byrd Polar & Climate Res Ctr, Columbus, OH 43214 USA

[3] CALTECH, Jet Prop Lab, NASA, 4800 Oak Grove Dr, Pasadena, CA 91109 USA

[4] Univ N Carolina, Dept Geol Sci, Chapel Hill, NC 27599 USA

关键词: River hydrology;    Radar interferometry;   

DOI  :  10.1016/j.rse.2020.111883

来源: Elsevier

【 摘 要 】

Water surface elevation (WSE), slope and width measurements from the forthcoming Surface Water and Ocean Topography (SWOT) mission will enable spaceborne estimates of global river discharge. WSE will be measured by interferometric synthetic aperture radar (InSAR). InSAR measurements are vulnerable to contamination from layover, a phenomenon wherein radar returns from multiple locations arrive at the sensor simultaneously, rendering them indistinguishable. This study assesses whether layover will significantly impact the precision of SWOT estimates of global river discharge. We present a theoretical river layover uncertainty model at the scale of nodes and reaches, which constitute nominal 200 m and 10 km averages, respectively, along river centerlines. The model is calibrated using high-resolution simulations of SWOT radar interaction with topography covering a total of 41,233 node observations, across a wide range of near-river topographic features. We find that height uncertainty increases to a maximum value at relatively low values of topographic standard deviation and varies strongly with position in the swath. When applied at global scale, the calibrated model shows that layover causes expected height uncertainty to increase by only a modest amount (from 9.4 to 10.4 cm at the 68th percentile). The 68th percentile of the slope uncertainty increases more significantly, from 10 to 17 mm/km. Nonetheless, the 68th percentile discharge uncertainty increases only marginally. We find that the impact of layover on SWOT river discharge is expected to be small in most environments.

【 授权许可】

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