@article{fdi:010090530,
  title = {{T}emporal decorrelation of {C}-band radar data over wheat in a semi-arid area using sub-daily tower-based observations},
  author = {{O}uaadi, {N}. and {J}arlan, {L}ionel and {V}illard, {L}. and {C}hakir, {A}dnane and {K}habba, {S}. and {F}anise, {P}ascal and {K}asbani, {M}. and {R}afi, {Z}. and {L}e {D}antec, {V}. and {E}zzahar, {J}. and {F}rison, {P}. {L}.},
  editor = {},
  language = {{ENG}},
  abstract = {{R}ecent studies have shown that radar temporal coherence over tropical and boreal forests undergoes a diurnal cycle as a result of a combined effect of the wind-induced motion of scatterers and of the change and displacement of water within the plant in response to the transpiration process. {W}ithin this context, the objective of this paper is to investigate, for the first time, the diurnal cycle of temporal coherence over wheat crops in relation to its development and physiological functioning throughout the agricultural season. {A} ground-based experiment was installed in {M}orocco, targeting a wheat field during the 2020 agricultural season. {T}he radar system, essentially based on a {V}ector {N}etwork {A}nalyzer ({VNA}) connected to 6{C} -band antennas installed at the top of a 20 m tower, has enabled quad-polarimetric acquisitions every 15 min. {I}n parallel, evapotranspiration, soil moisture and meteorological variables are automatically measured in addition to above-ground biomass and vegetation water content collected during field campaigns. {T}he results show that the temporal coherence with a 15 min baseline follows a marked diurnal cycle characterized by variable amplitude according to the phenological stage, with high values during the night, a significant morning drop to reach the lowest values in the late afternoon followed by an increase to recover the high nighttime values. {T}he rate of the drop at dawn is shown to be related to the increase of evapotranspiration (r = 0.80 at {VV} polarization) when the wheat is covering the soil and the transpiration dominate the evapotranspiration process. {T}his supports the assumption of a physiological effect related to water movement entailing a decorrelation. {B}y contrast, the daily minimum of temporal coherence occurring in the late afternoon correlates well to the daily maximum of wind (r = 0.7). {I}nterestingly enough, the amplitude of the diurnal cycle exhibit a marked seasonal evolution characterized by an increase of 85% from tillering to maturity in relation to the wheat development. {A}t the early start of the season when the soil is almost bare, irrigation events impact slightly the diurnal cycle of temporal coherence. {L}ikewise, it is shown that the presence of dew in the early morning has led to a decrease of the decorrelation rate. {T}emporal coherence dynamic has also been investigated for longer baselines up to 22 days. {R}esults indicate a stronger decorrelation than what has been observed on tropical and boreal forests by previous studies with values below 0.4 for baselines above 2 days. {T}aken together, the results of this work demonstrate the unique potential of sub-daily {C}band data for monitoring crop water status by future geostationary radar missions such as {H}ydroterra.},
  keywords = {{T}emporal coherence ; {C}-band ; {D}iurnal cycle ; {S}easonal cycle ; {E}vapotranspiration ; {I}rrigation ; {D}ew ; {W}heat ; {P}henological stages ; {S}emi-arid region ; {MAROC} ; {ZONE} {SEMIARIDE} ; {ZONE} {MEDITERRANEENNE}},
  booktitle = {},
  journal = {{R}emote {S}ensing of {E}nvironment},
  volume = {304},
  numero = {},
  pages = {114059 [17 ]},
  ISSN = {0034-4257},
  year = {2024},
  DOI = {10.1016/j.rse.2024.114059},
  URL = {https://www.documentation.ird.fr/hor/fdi:010090530},
}