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Comparison between SMOS Vegetation Optical Depth products and MODIS vegetation indices over crop zones of the USA

Lawrence, Heather; Wigneron, Jean-Pierre; Richaume, Philippe; Novello, Nathalie; Grant, Jennifer LU ; Mialon, Arnaud; Al Bitar, Ahmad; Merlin, Olivier; Guyon, Dominique and Leroux, Delphine, et al. (2014) In Remote Sensing of Environment 140. p.396-406
Abstract
The Soil Moisture and Ocean Salinity (SMOS) mission provides multi-angular, dual-polarised brightness temperatures at 1.4 GHz, from which global soil moisture and vegetation optical depth (tau) products are retrieved. This paper presents a study of SMOS' tau product in 2010 and 2011 for crop zones of the USA. Retrieved tau values for 504 crop nodes were compared to optical/IR vegetation indices from the MODES (Moderate Resolution Imaging Spectroradiometer) satellite sensor, including the Normalised Difference Vegetation Index (NDVI), Enhanced Vegetation Index (EVE), Leaf Area Index (LAI), and a Normalised Difference Water Index (NOW!) product. tau values were observed to increase during the growing season and decrease during senescence in... (More)
The Soil Moisture and Ocean Salinity (SMOS) mission provides multi-angular, dual-polarised brightness temperatures at 1.4 GHz, from which global soil moisture and vegetation optical depth (tau) products are retrieved. This paper presents a study of SMOS' tau product in 2010 and 2011 for crop zones of the USA. Retrieved tau values for 504 crop nodes were compared to optical/IR vegetation indices from the MODES (Moderate Resolution Imaging Spectroradiometer) satellite sensor, including the Normalised Difference Vegetation Index (NDVI), Enhanced Vegetation Index (EVE), Leaf Area Index (LAI), and a Normalised Difference Water Index (NOW!) product. tau values were observed to increase during the growing season and decrease during senescence in these areas, as did MODIS vegetation indices. SMOS' tau values generally peaked later than MODES LAI values, with an estimated time difference of about 19 days. A linear regression between tau and the MODIS products was carried out for each node and values of the determination coefficient, R-2, slope, b' and intercept, b '' were found. The average R-2 value varied from 0.32 to 035 for the different vegetation indices. The linear regression between LAI and tau produced an average slope of b' = 0.06, and an average intercept of b '' = 0.14. The effects of crop fraction and dominant crop type were investigated and crop fraction was found to have a low effect on R-2 values. R-2 values appeared to be lower for wheat and hay and higher for corn. b' and b '' values had higher standard deviations for wheat but were generally close to the mean values for corn, soybean and hay. (C) 2013 Published by Elsevier Inc. (Less)
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publication status
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subject
keywords
SMOS, Vegetation optical depth, L-band radiometry, Optical vegetation, indices
in
Remote Sensing of Environment
volume
140
pages
396 - 406
publisher
Elsevier
external identifiers
  • wos:000329766200033
  • scopus:84885147206
ISSN
0034-4257
DOI
10.1016/j.rse.2013.07.021
language
English
LU publication?
yes
id
d725228b-9850-4d30-92a2-20a0685e0dfc (old id 4318686)
date added to LUP
2014-02-25 12:05:37
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2017-11-05 03:13:05
@article{d725228b-9850-4d30-92a2-20a0685e0dfc,
  abstract     = {The Soil Moisture and Ocean Salinity (SMOS) mission provides multi-angular, dual-polarised brightness temperatures at 1.4 GHz, from which global soil moisture and vegetation optical depth (tau) products are retrieved. This paper presents a study of SMOS' tau product in 2010 and 2011 for crop zones of the USA. Retrieved tau values for 504 crop nodes were compared to optical/IR vegetation indices from the MODES (Moderate Resolution Imaging Spectroradiometer) satellite sensor, including the Normalised Difference Vegetation Index (NDVI), Enhanced Vegetation Index (EVE), Leaf Area Index (LAI), and a Normalised Difference Water Index (NOW!) product. tau values were observed to increase during the growing season and decrease during senescence in these areas, as did MODIS vegetation indices. SMOS' tau values generally peaked later than MODES LAI values, with an estimated time difference of about 19 days. A linear regression between tau and the MODIS products was carried out for each node and values of the determination coefficient, R-2, slope, b' and intercept, b '' were found. The average R-2 value varied from 0.32 to 035 for the different vegetation indices. The linear regression between LAI and tau produced an average slope of b' = 0.06, and an average intercept of b '' = 0.14. The effects of crop fraction and dominant crop type were investigated and crop fraction was found to have a low effect on R-2 values. R-2 values appeared to be lower for wheat and hay and higher for corn. b' and b '' values had higher standard deviations for wheat but were generally close to the mean values for corn, soybean and hay. (C) 2013 Published by Elsevier Inc.},
  author       = {Lawrence, Heather and Wigneron, Jean-Pierre and Richaume, Philippe and Novello, Nathalie and Grant, Jennifer and Mialon, Arnaud and Al Bitar, Ahmad and Merlin, Olivier and Guyon, Dominique and Leroux, Delphine and Bircher, Simone and Kerr, Yann},
  issn         = {0034-4257},
  keyword      = {SMOS,Vegetation optical depth,L-band radiometry,Optical vegetation,indices},
  language     = {eng},
  pages        = {396--406},
  publisher    = {Elsevier},
  series       = {Remote Sensing of Environment},
  title        = {Comparison between SMOS Vegetation Optical Depth products and MODIS vegetation indices over crop zones of the USA},
  url          = {http://dx.doi.org/10.1016/j.rse.2013.07.021},
  volume       = {140},
  year         = {2014},
}