Exploiting the synergy between SMAP and SMOS to improve brightness temperature simulations and soil moisture retrievals in arid regions

Mohsen Ebrahimi; Seyed Kazem Alavipanah; Saeid Hamzeh; Farshad Amiraslani; Najmeh Neysani Samany; Jean Pierre Wigneron

doi:10.1016/j.jhydrol.2017.12.051

Exploiting the synergy between SMAP and SMOS to improve brightness temperature simulations and soil moisture retrievals in arid regions

Mohsen Ebrahimi, Seyed Kazem Alavipanah, Saeid Hamzeh, Farshad Amiraslani, Najmeh Neysani Samany, Jean Pierre Wigneron

Research output: Contribution to journal › Article › peer-review

10 Citations (Scopus)

Abstract

The objective of this study was to exploit the synergy between SMOS and SMAP based on vegetation optical depth (VOD) to improve brightness temperature (TB) simulations and land surface soil moisture (SM) retrievals in arid regions of the world. In the current operational algorithm of SMAP (level 2), vegetation water content (VWC) is considered as a proxy to compute VOD which is calculated by an empirical conversion function of NDVI. Avoiding the empirical estimation of VOD, the SMOS algorithm is used to retrieve simultaneously SM and VOD from TB observations. The present study attempted to improve SMAP TB simulations and SM retrievals by benefiting from the advantages of the SMOS (L-MEB) algorithm. This was achieved by using a synergy method based on replacing the default value of SMAP VOD with the retrieved value of VOD from the SMOS multi angular and bi-polarization observations of TB. The insitu SM measurements, used as reference SM in this study, were obtained from the International Soil Moisture Network (ISMN) over 180 stations located in arid regions of the world. Furthermore, four stations were randomly selected to analyze the temporal variations in VOD and SM. Results of the synergy method showed that the accuracy of the TB simulations and SM retrievals was respectively improved at 144 and 124 stations (out of a total of 180 stations) in terms of coefficient of determination (R²) and unbiased root mean squared error (UbRMSE). Analyzing the temporal variations in VOD showed that the SMOS VOD, conversely to the SMAP VOD, can better illustrate the presence of herbaceous plants and may be a better indicator of the seasonal changes in the vegetation density and biomass over the year.

Original language	English
Pages (from-to)	740-752
Number of pages	13
Journal	Journal of Hydrology
Volume	557
DOIs	https://doi.org/10.1016/j.jhydrol.2017.12.051
Publication status	Published (in print/issue) - 1 Feb 2018

Bibliographical note

Funding Information:
Many thanks go to Amen Al-Yaari for his helpful comments and Fernandez-Moran for providing some MATLAB codes. The authors would like to acknowledge the CATDS (https://www.catds.fr/), the Jet Propulsion Laboratory and NASA Reverb exploring tools (https://reverb.echo.nasa.gov), and ISMN (https://ismn.geo.tuwien.ac.at/) for making respectively the SMOS, SMAP, and insitu SM measurements data freely available. We are very thankful to the anonymous reviewers for their comments on this manuscript. The authors actually thank Iranian National Science Foundation and CNES/TOSCA for their supports in this research.

Publisher Copyright:
© 2017 Elsevier B.V.

Copyright:
Copyright 2018 Elsevier B.V., All rights reserved.

Keywords

L-MEB
SMAP
SMOS
Synergy
Vegetation optical depth
τ-ω

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

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10.1016/j.jhydrol.2017.12.051

Cite this

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title = "Exploiting the synergy between SMAP and SMOS to improve brightness temperature simulations and soil moisture retrievals in arid regions",

abstract = "The objective of this study was to exploit the synergy between SMOS and SMAP based on vegetation optical depth (VOD) to improve brightness temperature (TB) simulations and land surface soil moisture (SM) retrievals in arid regions of the world. In the current operational algorithm of SMAP (level 2), vegetation water content (VWC) is considered as a proxy to compute VOD which is calculated by an empirical conversion function of NDVI. Avoiding the empirical estimation of VOD, the SMOS algorithm is used to retrieve simultaneously SM and VOD from TB observations. The present study attempted to improve SMAP TB simulations and SM retrievals by benefiting from the advantages of the SMOS (L-MEB) algorithm. This was achieved by using a synergy method based on replacing the default value of SMAP VOD with the retrieved value of VOD from the SMOS multi angular and bi-polarization observations of TB. The insitu SM measurements, used as reference SM in this study, were obtained from the International Soil Moisture Network (ISMN) over 180 stations located in arid regions of the world. Furthermore, four stations were randomly selected to analyze the temporal variations in VOD and SM. Results of the synergy method showed that the accuracy of the TB simulations and SM retrievals was respectively improved at 144 and 124 stations (out of a total of 180 stations) in terms of coefficient of determination (R2) and unbiased root mean squared error (UbRMSE). Analyzing the temporal variations in VOD showed that the SMOS VOD, conversely to the SMAP VOD, can better illustrate the presence of herbaceous plants and may be a better indicator of the seasonal changes in the vegetation density and biomass over the year.",

keywords = "L-MEB, SMAP, SMOS, Synergy, Vegetation optical depth, τ-ω",

author = "Mohsen Ebrahimi and Alavipanah, {Seyed Kazem} and Saeid Hamzeh and Farshad Amiraslani and {Neysani Samany}, Najmeh and Wigneron, {Jean Pierre}",

note = "Funding Information: Many thanks go to Amen Al-Yaari for his helpful comments and Fernandez-Moran for providing some MATLAB codes. The authors would like to acknowledge the CATDS (https://www.catds.fr/), the Jet Propulsion Laboratory and NASA Reverb exploring tools (https://reverb.echo.nasa.gov), and ISMN (https://ismn.geo.tuwien.ac.at/) for making respectively the SMOS, SMAP, and insitu SM measurements data freely available. We are very thankful to the anonymous reviewers for their comments on this manuscript. The authors actually thank Iranian National Science Foundation and CNES/TOSCA for their supports in this research. Publisher Copyright: {\textcopyright} 2017 Elsevier B.V. Copyright: Copyright 2018 Elsevier B.V., All rights reserved.",

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AU - Ebrahimi, Mohsen

AU - Alavipanah, Seyed Kazem

AU - Hamzeh, Saeid

AU - Amiraslani, Farshad

AU - Neysani Samany, Najmeh

AU - Wigneron, Jean Pierre

N1 - Funding Information: Many thanks go to Amen Al-Yaari for his helpful comments and Fernandez-Moran for providing some MATLAB codes. The authors would like to acknowledge the CATDS (https://www.catds.fr/), the Jet Propulsion Laboratory and NASA Reverb exploring tools (https://reverb.echo.nasa.gov), and ISMN (https://ismn.geo.tuwien.ac.at/) for making respectively the SMOS, SMAP, and insitu SM measurements data freely available. We are very thankful to the anonymous reviewers for their comments on this manuscript. The authors actually thank Iranian National Science Foundation and CNES/TOSCA for their supports in this research. Publisher Copyright: © 2017 Elsevier B.V. Copyright: Copyright 2018 Elsevier B.V., All rights reserved.

PY - 2018/2/1

Y1 - 2018/2/1

N2 - The objective of this study was to exploit the synergy between SMOS and SMAP based on vegetation optical depth (VOD) to improve brightness temperature (TB) simulations and land surface soil moisture (SM) retrievals in arid regions of the world. In the current operational algorithm of SMAP (level 2), vegetation water content (VWC) is considered as a proxy to compute VOD which is calculated by an empirical conversion function of NDVI. Avoiding the empirical estimation of VOD, the SMOS algorithm is used to retrieve simultaneously SM and VOD from TB observations. The present study attempted to improve SMAP TB simulations and SM retrievals by benefiting from the advantages of the SMOS (L-MEB) algorithm. This was achieved by using a synergy method based on replacing the default value of SMAP VOD with the retrieved value of VOD from the SMOS multi angular and bi-polarization observations of TB. The insitu SM measurements, used as reference SM in this study, were obtained from the International Soil Moisture Network (ISMN) over 180 stations located in arid regions of the world. Furthermore, four stations were randomly selected to analyze the temporal variations in VOD and SM. Results of the synergy method showed that the accuracy of the TB simulations and SM retrievals was respectively improved at 144 and 124 stations (out of a total of 180 stations) in terms of coefficient of determination (R2) and unbiased root mean squared error (UbRMSE). Analyzing the temporal variations in VOD showed that the SMOS VOD, conversely to the SMAP VOD, can better illustrate the presence of herbaceous plants and may be a better indicator of the seasonal changes in the vegetation density and biomass over the year.

AB - The objective of this study was to exploit the synergy between SMOS and SMAP based on vegetation optical depth (VOD) to improve brightness temperature (TB) simulations and land surface soil moisture (SM) retrievals in arid regions of the world. In the current operational algorithm of SMAP (level 2), vegetation water content (VWC) is considered as a proxy to compute VOD which is calculated by an empirical conversion function of NDVI. Avoiding the empirical estimation of VOD, the SMOS algorithm is used to retrieve simultaneously SM and VOD from TB observations. The present study attempted to improve SMAP TB simulations and SM retrievals by benefiting from the advantages of the SMOS (L-MEB) algorithm. This was achieved by using a synergy method based on replacing the default value of SMAP VOD with the retrieved value of VOD from the SMOS multi angular and bi-polarization observations of TB. The insitu SM measurements, used as reference SM in this study, were obtained from the International Soil Moisture Network (ISMN) over 180 stations located in arid regions of the world. Furthermore, four stations were randomly selected to analyze the temporal variations in VOD and SM. Results of the synergy method showed that the accuracy of the TB simulations and SM retrievals was respectively improved at 144 and 124 stations (out of a total of 180 stations) in terms of coefficient of determination (R2) and unbiased root mean squared error (UbRMSE). Analyzing the temporal variations in VOD showed that the SMOS VOD, conversely to the SMAP VOD, can better illustrate the presence of herbaceous plants and may be a better indicator of the seasonal changes in the vegetation density and biomass over the year.

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KW - τ-ω

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SN - 0022-1694

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JO - Journal of Hydrology

JF - Journal of Hydrology

ER -

Exploiting the synergy between SMAP and SMOS to improve brightness temperature simulations and soil moisture retrievals in arid regions

Abstract

Bibliographical note

Keywords

UN SDGs

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