@article{fdi:010080408,
  title = {{M}onitoring of wheat crops using the backscattering coefficient and the interferometric coherence derived from {S}entinel-1 in semi-arid areas},
  author = {{O}uaadi, {N}. and {J}arlan, {L}ionel and {E}zzahar, {J}. and {Z}ribi, {M}. and {K}habba, {S}. and {B}ouras, {E}. and {B}ousbih, {S}. and {F}rison, {P}. {L}.},
  editor = {},
  language = {{ENG}},
  abstract = {{R}adar data at {C}-band has shown great potential for the monitoring of soil and canopy hydric conditions of wheat crops. {I}n this study, the {C}-band {S}entinel-1 time series including the backscattering coefficients u(0) at {VV} and {VH} polarization, the polarization ratio ({PR}) and the interferometric coherence p are first analyzed with the support of experimental data gathered on three plots of irrigated winter wheat located in the {H}aouz plain in the center of {M}orocco covering five growing seasons. {T}he results showed that p and {PR} are tightly related to the canopy development. p is also sensitive to soil preparation. {B}y contrast, u(0) was found to be widely linked to changes in surface soil moisture ({SSM}) during the first growth stages when {L}eaf {A}rea {I}ndex remains moderate (< 1.5 m(2)/m(2)). {I}n addition, drastic changes in the crop geometry associated to heading had a strong impact on the {C}-band u(0), in particular for {VH} polarization. {T}he coupled water cloud and {O}h models ({WCM}) were then calibrated and validated on the study sites. {T}he comparison between the predicted and observed u0 yielded a root mean square error ({RMSE}) values ranging from 1.50 d{B} to 2.02 d{B} for {VV} and between 1.74 d{B} to 2.52 d{B} for {VH} with significant differences occurring in the second part of the season after heading. {F}inally, new approaches based on the inversion of the {WCM} for {SSM} retrieval over wheat fields were proposed using {S}entinel-1 radar data only. {T}o this objective, the dry above-ground biomass ({AGB}) and the vegetation water content ({VWC}) were retrieved from the interferometric coherence and the {PR}. {T}he relationships were then used as the vegetation descriptor in the {WCM}. {T}he best retrieval results were obtained using the relationship between p{VV} and the {AGB} ({R} and {RMSE} of 0.82, 0.05 m3/m3 respectively and no bias). {T}he new retrieval approaches were then applied to a large database covering a rainfed field in {M}orocco and 18 plots of rainfed and irrigated wheat of the {K}airouan plain ({T}unisia) and compared to other classical techniques of {SSM} retrieval including simple linear relationships between {SSM} and u0. {T}he method based on the {WCM} and the p{VV}-{AGB} relationships also provided with slightly better results than the others on the validation database (r = 0.75, {RMSE} = 0.06 m(3)/m(3) and bias = 0.01 m(3)/m(3) over the 18 plots of {T}unisia) but the simple linear relationships performed also reasonably well (r = 0.62, {RMSE} = 0.07, bias = -0.01 in {T}unisia for instance). {T}his study opens perspectives for high resolution soil moisture mapping from {S}entinel-1 data over south {M}editerranean wheat crops and in fine, for irrigation scheduling and retrieval through the assimilation of these new products in an evapotranspiration model.},
  keywords = {{S}entinel-1 ; {S}urface soil moisture ; {B}ackscattering coefficient ; {C}-band ; {I}nterferometric coherence ; {W}inter wheat ; {S}emi-arid region ; {MAROC} ; {ZONE} {SEMIARIDE} ; {HAOUZ} {PLAINE}},
  booktitle = {},
  journal = {{R}emote {S}ensing of {E}nvironment},
  volume = {251},
  numero = {},
  pages = {12050 [20 ]},
  ISSN = {0034-4257},
  year = {2020},
  URL = {https://www.documentation.ird.fr/hor/fdi:010080408},
}