@article{fdi:010073104,
  title = {{E}valuating four gap-filling methods for eddy covariance measurements of evapotranspiration over hilly crop fields},
  author = {{B}oudhina, {N}. and {Z}itouna-{C}hebbi, {R}. and {M}ekki, {I}. and {J}acob, {F}r{\'e}d{\'e}ric and {B}en {M}echlia, {N}. and {M}asmoudi, {M}. and {P}revot, {L}.},
  editor = {},
  language = {{ENG}},
  abstract = {{E}stimating evapotranspiration in hilly watersheds is paramount for managing water resources, especially in semiarid/subhumid regions. {T}he eddy covariance ({EC}) technique allows continuous measurements of latent heat flux ({LE}). {H}owever, time series of {EC} measurements often experience large portions of missing data because of instrumental malfunctions or quality filtering. {E}xisting gap-filling methods are questionable over hilly crop fields because of changes in airflow inclination and subsequent aerodynamic properties. {W}e evaluated the performances of different gap-filling methods before and after tailoring to conditions of hilly crop fields. {T}he tailoring consisted of splitting the {LE} time series beforehand on the basis of upslope and downslope winds. {T}he experiment was setup within an agricultural hilly watershed in northeastern {T}unisia. {EC} measurements were collected throughout the growth cycle of three wheat crops, two of them located in adjacent fields on opposite hillslopes, and the third one located in a flat field. {W}e considered four gap-filling methods: the {RE}ddy{P}roc method, the linear regression between {LE} and net radiation ({R}n), the multi-linear regression of {LE} against the other energy fluxes, and the use of evaporative fraction ({EF}). {R}egardless of the method, the splitting of the {LE} time series did not impact the gap-filling rate, and it might improve the accuracies on {LE} retrievals in some cases. {R}egardless of the method, the obtained accuracies on {LE} estimates after gap filling were close to instrumental accuracies, and they were comparable to those reported in previous studies over flat and mountainous terrains. {O}verall, {RE}ddy{P}roc was the most appropriate method, for both gap-filling rate and retrieval accuracy. {T}hus, it seems possible to conduct gap filling for {LE} time series collected over hilly crop fields, provided the {LE} time series are split beforehand on the basis of upslope-downslope winds. {F}uture works should address consecutive vegetation growth cycles for a larger panel of conditions in terms of climate, vegetation, and water status.},
  keywords = {{TUNISIE}},
  booktitle = {},
  journal = {{G}eoscientific {I}nstrumentation {M}ethods and {D}ata {S}ystems},
  volume = {7},
  numero = {2},
  pages = {151--167},
  ISSN = {2193-0856},
  year = {2018},
  DOI = {10.5194/gi-7-151-2018},
  URL = {https://www.documentation.ird.fr/hor/fdi:010073104},
}