@article{fdi:010073116,
  title = {{R}etrieving surface soil moisture at high spatio-temporal resolution from a synergy between {S}entinel-1 radar and {L}andsat thermal data : a study case over bare soil},
  author = {{A}mazirh, {A}. and {M}erlin, {O}livier and {E}r-{R}aki, {S}. and {G}ao, {Q}. and {R}ivalland, {V}. and {M}albeteau, {Y}. and {K}habba, {S}. and {E}scorihuela, {M}. {J}.},
  editor = {},
  language = {{ENG}},
  abstract = {{R}adar data have been used to retrieve and monitor the surface soil moisture ({SM}) changes in various conditions. {H}owever, the calibration of radar models whether empirically or physically-based, is still subject to large uncertainties especially at high-spatial resolution. {T}o help calibrate radar-based retrieval approaches to supervising {SM} at high resolution, this paper presents an innovative synergistic method combining {S}entinel-1 ({S}i) microwave and {L}andsat-7/8 ({L}7/8) thermal data. {F}irst, the {S}1 backscatter coefficient was normalized by its maximum and minimum values obtained during 2015-2016 agriculture season. {S}econd, the normalized {S}1 backscatter coefficient was calibrated from reference points provided by a thermal-derived {SM} proxy named soil evaporative efficiency ({SEE}, defined as the ratio of actual to potential soil evaporation). {SEE} was estimated as the radiometric soil temperature normalized by its minimum and maximum values reached in a water-saturated and dry soil, respectively. {W}e estimated both soil temperature endmembers by using a soil energy balance model forced by available meteorological forcing. {T}he proposed approach was evaluated against in situ {SM} measurements collected over three bare soil fields in a semi-arid region in {M}orocco and we compared it against a classical approach based on radar data only. {T}he two polarizations {VV} (vertical transmit and receive) and {VH} (vertical transmit and horizontal receive) of the {S}1 data available over the area are tested to analyse the sensitivity of radar signal to {SM} at high incidence angles (39 degrees-43 degrees). {W}e found that the {VV} polarization was better correlated to {SM} than the {VH} polarization with a determination coefficient of 0.47 and 0.28, respectively. {B}y combining {S}i ({VV}) and {L}7/8 data, we reduced the root mean square difference between satellite and in situ {SM} to 0.03 m(3) m(-3) which is far smaller than 0.16 m(3) m(-3) when using {SI} ({VV}) only.},
  keywords = {{N}ear surface soil moisture ; {S}entinel-1 ({A}/{B}) ; {L}andsat-7/8 ; {E}nergy balance modelling ; {S}oil evaporation ; {B}are soil ; {MAROC}},
  booktitle = {},
  journal = {{R}emote {S}ensing of {E}nvironment},
  volume = {211},
  numero = {},
  pages = {321--337},
  ISSN = {0034-4257},
  year = {2018},
  DOI = {10.1016/j.rse.2018.04.013},
  URL = {https://www.documentation.ird.fr/hor/fdi:010073116},
}