Universität zu Köln

Ullmann, Tobias, Jagdhuber, Thomas, Hoffmeister, Dirk, May, Simon Matthias, Baumhauer, Roland and Bubenzer, Olaf (2023). Exploring Sentinel-1 backscatter time series over the Atacama Desert (Chile) for seasonal dynamics of surface soil moisture. Remote Sens. Environ., 285. NEW YORK: ELSEVIER SCIENCE INC. ISSN 1879-0704

Full text not available from this repository.

Abstract

Recent research indicates an inverse relation between Synthetic Aperture Radar (SAR) signal and near-surface soil moisture (SM) over very dry sediments, arid to hyper-arid soils resp., caused by subsurface scattering ef-fects. This phenomenon can lead to large errors when it comes to modelling and remote sensing-based estimation of SM. While the effect of subsurface scattering and its influence on SM estimates is well described and modelled in literature, its actual presence in recorded SAR data is largely unknown. Here we investigate the relation between C-Band SAR backscatter and SM in the hyper-arid environment of the Atacama Desert (Chile). Time series (2018-2020) of Sentinel-1 VV/VH intensities are compared to in situ SM, measured at 17 stations located across the Atacama Desert. Linear and non-linear regression modelling is applied to uncover the relationship between the SAR intensities and in situ SM, while, in addition, SM variations triggered by seasonal varying humidity (i.e., not by precipitation) are investigated. Results indicate (i) a very weak linear relationship between SM variations and SAR intensities (VV/VH) for most meteorological stations in the Atacama (R2 < 0.5). In particular, noticeable and significant exceptions are found for stations located in the northern uplands of the Coastal Cordillera and on sediments, which are characterized by thick atmospheric dust deposits on top of subsurface cemented crusts; (ii) over these sites a strong inverse linear relationship is present (R2 up to 0.84) and the observable seasonal variations in SAR intensity are linked to the seasonal variations in SM; (iii) remarkably low changes in SM (ranging from approx. 1 to 3%) lead to comparable high changes in SAR intensity (up to 5.5 dB in VH and up to 4.0 dB in VV); (iv) employing a non-linear regression modelling to the SAR time series allowed identifying the occurrence and the strength of seasonal variations over the central desert. This study contributes to a better understanding of SAR scattering over arid to hyper-arid soils, indicates a moisture -regulated complex interplay of surface and subsurface scattering, and proves the presence of subsurface scat-tering effects in Sentinel-1C-Band data to occur over large parts of the Atacama Desert.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Ullmann, Tobias UNSPECIFIED UNSPECIFIED UNSPECIFIED Jagdhuber, Thomas UNSPECIFIED UNSPECIFIED UNSPECIFIED Hoffmeister, Dirk UNSPECIFIED UNSPECIFIED UNSPECIFIED May, Simon Matthias UNSPECIFIED UNSPECIFIED UNSPECIFIED Baumhauer, Roland UNSPECIFIED UNSPECIFIED UNSPECIFIED Bubenzer, Olaf UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-685357
DOI:	10.1016/j.rse.2022.113413
Journal or Publication Title:	Remote Sens. Environ.
Volume:	285
Date:	2023
Publisher:	ELSEVIER SCIENCE INC
Place of Publication:	NEW YORK
ISSN:	1879-0704
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language SYNTHETIC-APERTURE RADAR; ZEBRA STRIPES; RETRIEVAL; ARIDITY; VALIDATION; NITRATE; ORIGIN; CORE Multiple languages Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/68535