@article{fdi:010082139,
  title = {{S}ea level anomalies using altimetry, model and tide gauges along the {A}frican coasts in the {E}astern {T}ropical {A}tlantic {O}cean : inter-comparison and temporal variability},
  author = {{D}ieng, {H}. {B}. and {D}adou, {I}. and {L}eger, {F}. and {M}orel, {Y}. and {J}ouanno, {J}ulien and {L}yard, {F}. and {A}llain, {D}.},
  editor = {},
  language = {{ENG}},
  abstract = {{B}ecause of sparse in situ measurements, the use of altimeter and ocean models are currently the only options to understand the coastal variability of sea level anomalies ({SLA}) near the {A}frican coasts of the {E}astern {T}ropical {A}tlantic {O}cean ({ETAO}: 35 degrees {S}-25 degrees {N}; 25 degrees {W}-{A}frican coasts). {I}n this study, three {SLA} products derived from altimetry ({X}-{TRACK} and {CMEMS}) and from a regional ocean model ({NEMO}) are validated near the coast using the 14 tide gauges ({TG}s) available in the region. {S}tatistical analysis (correlation, standard deviation and root mean square) are performed to compare our three products with the {TG}. {W}e then analyze the sub-seasonal to inter-annual variability of {SLA}s (i.e. from 20 days up to 2 years) over the period {J}anuary 2008-{D}ecember 2014. {W}e found a very good agreement between altimetry, model and {TG}s near the coasts of {S}enegal (10 degrees {N}-25 degrees {N}) and {G}ulf of {G}uinea (10 degrees {S}-10 degrees {N}). {T}his is not the case near the coast of {B}enguela (south of 10 degrees {S}) and is mainly explained by the combined effects of the position of {TG}s (located in semi-enclosed bays), the geophysical corrections used in the computations of the {SLA} derived from altimetry (i.e. tide, dynamical atmospheric correction -{DAC}- and sea state bias -{SSB}-). {I}n addition, the low spatial resolution of the {CMEMS} and model data do not allow a good description of the small scale oceanic and atmospheric variability, which dominates in the {B}enguela upwelling system. {W}e then show, with all products, that the temporal variability of {SLA} is mainly seasonal (annual and semi-annual) throughout the {ETAO} region. {T}he altimetry data also show some inter-annual (15-24 months) variability in the equatorial band, which can be related to equatorial {K}elvin waves. {T}his is less pronounced with the {NEMO} model and does not appear over the whole equatorial band. {W}e show that high spatial resolution and improved altimetric geophysical corrections near the coast can each reduce near-shore data errors by up to 10%. {H}owever, despite these improvements, agreements between {SLA} products are still unsatisfactory in the {B}enguela region, suggesting that efforts need to be intensified on geophysical corrections and in increasing the temporal and spatial resolution of data near the coast. {M}oreover, there exist gaps in {TG} measurements, along the {W}est {A}frican coast, especially in the {B}enguela region. {T}he {TG} network should thus be completed.},
  keywords = {{S}ea level anomalies ; {C}oastal altimetry ; {A}frican coasts ; {E}astern {T}ropical {A}tlantic {O}cean ; {X}-{TRACK} and {CMEMS} ; {NEMO} model ; {T}ide gauge ; {AFRIQUE} ; {ATLANTIQUE} {EST} ; {ZONE} {TROPICALE}},
  booktitle = {},
  journal = {{A}dvances in {S}pace {R}esearch},
  volume = {68},
  numero = {2},
  pages = {534--552},
  ISSN = {0273-1177},
  year = {2021},
  DOI = {10.1016/j.asr.2019.10.019},
  URL = {https://www.documentation.ird.fr/hor/fdi:010082139},
}