Error Propagation in Microwave Soil Moisture and Vegetation Optical Depth Retrievals

Satellite soil moisture and vegetation optical depth [(VOD); related to the total vegetation water mass per unit area] are increasingly being used to study water relations in the soil-plant continuum across the globe. However, soil moisture and VOD are typically jointly estimated, where errors in th...

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Autores principales:	Andrew Feldman, David Chaparro, Dara Entekhabi
Formato:	article
Lenguaje:	EN
Publicado:	IEEE 2021
Materias:	Brightness temperature microwave retrieval algorithms regularization soil moisture vegetation optical depth Ocean engineering TC1501-1800 Geophysics. Cosmic physics QC801-809
Acceso en línea:	https://doaj.org/article/124c54438ea94a57bef95e65b47980c9
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spelling	oai:doaj.org-article:124c54438ea94a57bef95e65b47980c92021-11-19T00:00:18ZError Propagation in Microwave Soil Moisture and Vegetation Optical Depth Retrievals2151-153510.1109/JSTARS.2021.3124857https://doaj.org/article/124c54438ea94a57bef95e65b47980c92021-01-01T00:00:00Zhttps://ieeexplore.ieee.org/document/9601253/https://doaj.org/toc/2151-1535Satellite soil moisture and vegetation optical depth [(VOD); related to the total vegetation water mass per unit area] are increasingly being used to study water relations in the soil-plant continuum across the globe. However, soil moisture and VOD are typically jointly estimated, where errors in the optimization approach can cause compensation between both variables and confound such studies. It is thus critical to quantify how satellite microwave measurement errors propagate into soil moisture and VOD. Such a study is especially important for VOD given limited investigations of whether VOD reflects <italic>in situ</italic> plant physiology. Furthermore, despite new approaches that constrain (or regularize) VOD dynamics to reduce soil moisture errors, there is limited study of whether regularization reduces VOD errors without obscuring true vegetation temporal dynamics. Here, we find that, across the globe, VOD is less robust to measurement error (more difficult for optimization methods to find the true solution) than soil moisture in their joint estimation. However, a moderate degree of regularization (via time-constrained VOD) reduces errors in VOD to a greater degree than soil moisture and reduces spurious soil moisture-VOD coupling. Furthermore, despite constraining VOD time dynamics, regularized VOD variations on subweekly scales are both closer to simulated true VOD time series and have global VOD post-rainfall responses with reduced error signatures compared to VOD retrievals without regularization. Ultimately, we recommend moderately regularized VOD for use in large scale studies of soil-plant water relations because it suppresses noise and spurious soil moisture-VOD coupling without removing the physical signal.Andrew FeldmanDavid ChaparroDara EntekhabiIEEEarticleBrightness temperaturemicrowave retrieval algorithmsregularizationsoil moisturevegetation optical depthOcean engineeringTC1501-1800Geophysics. Cosmic physicsQC801-809ENIEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, Vol 14, Pp 11311-11323 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	Brightness temperature microwave retrieval algorithms regularization soil moisture vegetation optical depth Ocean engineering TC1501-1800 Geophysics. Cosmic physics QC801-809
spellingShingle	Brightness temperature microwave retrieval algorithms regularization soil moisture vegetation optical depth Ocean engineering TC1501-1800 Geophysics. Cosmic physics QC801-809 Andrew Feldman David Chaparro Dara Entekhabi Error Propagation in Microwave Soil Moisture and Vegetation Optical Depth Retrievals
description	Satellite soil moisture and vegetation optical depth [(VOD); related to the total vegetation water mass per unit area] are increasingly being used to study water relations in the soil-plant continuum across the globe. However, soil moisture and VOD are typically jointly estimated, where errors in the optimization approach can cause compensation between both variables and confound such studies. It is thus critical to quantify how satellite microwave measurement errors propagate into soil moisture and VOD. Such a study is especially important for VOD given limited investigations of whether VOD reflects <italic>in situ</italic> plant physiology. Furthermore, despite new approaches that constrain (or regularize) VOD dynamics to reduce soil moisture errors, there is limited study of whether regularization reduces VOD errors without obscuring true vegetation temporal dynamics. Here, we find that, across the globe, VOD is less robust to measurement error (more difficult for optimization methods to find the true solution) than soil moisture in their joint estimation. However, a moderate degree of regularization (via time-constrained VOD) reduces errors in VOD to a greater degree than soil moisture and reduces spurious soil moisture-VOD coupling. Furthermore, despite constraining VOD time dynamics, regularized VOD variations on subweekly scales are both closer to simulated true VOD time series and have global VOD post-rainfall responses with reduced error signatures compared to VOD retrievals without regularization. Ultimately, we recommend moderately regularized VOD for use in large scale studies of soil-plant water relations because it suppresses noise and spurious soil moisture-VOD coupling without removing the physical signal.
format	article
author	Andrew Feldman David Chaparro Dara Entekhabi
author_facet	Andrew Feldman David Chaparro Dara Entekhabi
author_sort	Andrew Feldman
title	Error Propagation in Microwave Soil Moisture and Vegetation Optical Depth Retrievals
title_short	Error Propagation in Microwave Soil Moisture and Vegetation Optical Depth Retrievals
title_full	Error Propagation in Microwave Soil Moisture and Vegetation Optical Depth Retrievals
title_fullStr	Error Propagation in Microwave Soil Moisture and Vegetation Optical Depth Retrievals
title_full_unstemmed	Error Propagation in Microwave Soil Moisture and Vegetation Optical Depth Retrievals
title_sort	error propagation in microwave soil moisture and vegetation optical depth retrievals
publisher	IEEE
publishDate	2021
url	https://doaj.org/article/124c54438ea94a57bef95e65b47980c9
work_keys_str_mv	AT andrewfeldman errorpropagationinmicrowavesoilmoistureandvegetationopticaldepthretrievals AT davidchaparro errorpropagationinmicrowavesoilmoistureandvegetationopticaldepthretrievals AT daraentekhabi errorpropagationinmicrowavesoilmoistureandvegetationopticaldepthretrievals
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Error Propagation in Microwave Soil Moisture and Vegetation Optical Depth Retrievals

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