@article{fdi:010088729,
  title = {{W}eekly mapping of surface water extent in the intertropical wetlands using spaceborne {GNSS} reflectometry},
  author = {{Z}eiger, {P}. and {F}rappart, {F}. and {D}arrozes, {J}. and {P}rigent, {C}. and {J}im{\'e}nez, {C}. and {B}ourrel, {L}uc},
  editor = {},
  language = {{ENG}},
  abstract = {{A}s of today, the uncertain distribution and dynamics of inundations in the tropical wetlands cause large uncertainties in the quantification of the world's methane emissions. {L}ong-term, global remote sensing observations currently rely on optical sensors, affected by cloud cover and vegetation, and on passive microwave imagery with a low spatial resolution. {G}lobal {N}avigation {S}atellite {S}ystem {R}eflectometry ({GNSS}-{R}) {L}-band observations from space onboard the {C}yclone {GNSS} ({CYGNSS}) mission can provide information about the dynamics of surface water at moderate to low spatial resolution and with a frequent revisit. {I}n this article, we propose a methodology to compute the fraction of water contained in 0.1 degrees pixels (similar to 10 km) using {CYGNSS} reflectivity and {A}bove {G}round {B}iomass ({AGB}) maps. {W}e produced a 1-year time series of water fractions with a weekly time sampling for the full coverage of {CYGNSS} between +/- 38 degrees of latitude, from {A}ugust 2018 to {J}uly 2019. {W}e evaluated the results against regional reference maps of surface water based on {MODIS}, {JERS}-1, and {PALSAR}, and against the {G}lobal {I}nundation {E}xtent from {M}ulti-{S}atellite ({GIEMS}) dataset. {CYGNSS} water fractions represent well the spatial distribution and the seasonality of inundation extent for most of the tropical wetlands, with a global {RMSD} of 15.0 % against {GIEMS}. {W}e found a likely overestimation when the soil moisture ({SM}) exceeds 0.3-0.4 cm3/cm3, i.e. for saturated soils where {GNSS}-{R} reflections are coherent, as the {SM} was not parameterized in our retrieval model. {D}espite this, the results are consistent in the entire intertropical band including over densely vegetated areas. {T}hese weekly water fractions for 2018-2019 with a 0.1 degrees pixel size are distributed to contribute to further comparisons and hydrological researches.},
  keywords = {{GNSS}-reflectometry ; {CYGNSS} ; {I}nundation dynamics ; {S}urface water extent ; {W}ater fractions ; {W}etlands ; {MONDE}},
  booktitle = {},
  journal = {{J}ournal of {H}ydrology},
  volume = {626},
  numero = {{B}},
  pages = {130305 [17 p.]},
  ISSN = {0022-1694},
  year = {2023},
  DOI = {10.1016/j.jhydrol.2023.130305},
  URL = {https://www.documentation.ird.fr/hor/fdi:010088729},
}