@article{PAR00014092,
  title = {{C}omparison of {SMOS} and {AMSR}-{E} vegetation optical depth to four {MODIS}-based vegetation indices},
  author = {{G}rant, {J}. {P}. and {W}igneron, {J}. {P}. and {D}e {J}eu, {R}. {A}. {M}. and {L}awrence, {H}. and {M}ialon, {A}. and {R}ichaume, {P}. and {A}l {B}itar, {A}. and {D}rusch, {M}. and van {M}arle, {M}. {J}. {E}. and {K}err, {Y}ann},
  editor = {},
  language = {{ENG}},
  abstract = {{T}he main objectives of this study were to provide a proxy "validation" of the {S}oil {M}oisture and {O}cean {S}alinity ({SMOS}) mission's vegetation optical depth product (tau({SMOS})) on a global scale, to give a first indication of the potential of tau({SMOS}) to capture large-scale vegetation dynamics, and to contribute towards investigations into the possible use of optical vegetation indices ({VI}'s) for the estimation of tau. {T}he analyses were performed by comparing the spatial and temporal behaviour of tau({SMOS}) relative to four {MODIS}-based {VI}'s, with that of the vegetation optical depth from a similar sensor, {AMSR}-{E} (tau({AMSR}-{E})). 16-day and annual average values of the passive microwave optical depth (tau) for the year 2010 were obtained from {SMOS} (1.4 {GH}z) and {AMSR}-{E} (6.9 {GH}z) observations. {T}he {VI}'s chosen for this study were the {N}ormalized {D}ifference {V}egetation {I}ndex ({NDVI}), {E}nhanced {V}egetation {I}ndex ({EVI}), {L}eaf {A}rea {I}ndex ({LAI}) and {N}ormalized {D}ifference {W}ater {I}ndex ({NDWI}). {T}he highest global-scale, annual correlation was found between tau({SMOS}) and tau({AMSR}-{E}) from ascending orbits ({S}pearman's {R} = 0.80). {O}n global, annual scales, tau({SMOS}) showed higher correlations with tau({AMSR}-{E}) than with the {VI}'s, while tau({AMSR}-{E}) was more highly correlated with {VI}'s than with tau({SMOS}). {T}imeseries of both tau and the {VI}'s were made per landcover class, for the northern hemisphere, tropics and southern hemisphere. {A}lthough the large-scale spatial and spatio-temporal behaviour of tau({SMOS}) and tau({AMSR}-{E}) is generally similar, the results highlight some notable differences in observing vegetation with optical vs. passive microwave sensors, and certain crucial differences between the two passive microwave sensors themselves. {O}verall, the results found in this study give a good first confidence in the {SMOS} {L}3 tau product and its potential use in vegetation studies. {T}hese results provide an essential general reference for future (global-scale) vegetation monitoring with passive microwaves, for the future inclusion of tau({SMOS}) in long-term, multi-sensor datasets, and for passive microwave algorithm development.},
  keywords = {{SMOS} ; {AMSR}-{E} ; {MODIS} ; {P}assive microwaves ; {V}egetation optical depth ; {O}ptical vegetation indices},
  booktitle = {},
  journal = {{R}emote {S}ensing of {E}nvironment},
  volume = {172},
  numero = {},
  pages = {87--100},
  ISSN = {0034-4257},
  year = {2016},
  DOI = {10.1016/j.rse.2015.10.021},
  URL = {https://www.documentation.ird.fr/hor/{PAR}00014092},
}