@article{fdi:010037928,
  title = {{T}he {M}ercator global ocean operational analysis system: {A}ssessment and validation of an 11-year reanalysis},
  author = {{F}erry, {N}. and {R}{\'e}my, {E}. and {B}rasseur, {P}. and {M}aes, {C}hristophe},
  editor = {},
  language = {{ENG}},
  abstract = {{T}his paper presents {P}rototype {S}ysteme 2 {G}lobal ({PSY}2{G}), the first {M}ercator global {O}cean {G}eneral {C}irculation {M}odel ({OGCM}) to assimilate along-track sea level anomaly ({SLA}) satellite data. {B}ased on a coarse resolution ocean model, this system was developed mainly for climatic purposes and will provide, for example, initial oceanic states for coupled ocean-atmosphere seasonal predictions. {I}t has been operational since 3 {S}eptember 2003 and produces an analysis and a two-week forecast for the global ocean every week. {T}he {PSY}2{G} system uses an incremental assimilation scheme based on the {C}ooper and {H}aines [{C}ooper, {M}., {H}aines, {K}., 1996. {D}ata assimilation with water property conservation. {J}. {G}eophys. {R}es., 101, 1059-1077.] lifting-lowering of isopycnals. {T}he {SLA} increment is obtained using an optimal interpolation method then the correction is partitioned into baroclinic and barotropic contributions. {T}he baroclinic ocean state correction consists of temperature, salinity and geostrophic velocity increments and the barotropic correction is a barotropic velocity increment. {A} reanalysis (1993-2003) was carried out that enabled the {PSY}2{G} system to perform its first operational cycle. {A}ll available {SLA} data sets ({TOPEX}/{P}oseidon, {ERS}2, {G}eosat-{F}ollow-{O}n, {J}ason1 and {E}nvisat) were assimilated for the 1993-2003 period. {T}he major objective of this study is to assess the reanalysis from both an assimilation and a thermodynamic point of view in order to evaluate its realism, especially in the tropical band which is a key region for climatic studies. {A}lthough the system is also able to deliver forecasts, we have mainly focused on analysis. {T}hese results are useful because they give an a priori estimation of the qualities and capabilities of the operational ocean analysis system that has been implemented. {I}n particular, the reanalysis identifies some regional biases in sea level variability such as near the {A}ntarctic {C}ircumpolar {C}urrent, in the eastern {E}quatorial {P}acific and in the {N}orwegian {S}ea (generally less than 1 cm) with a small seasonal cycle. {T}his is attributed to changes in mean circulation and vertical stratification caused by the assimilation methodology. {B}ut the model's low resolution, inaccurate physical parameterisations (especially for ocean-ice interactions) and surface atmospheric forcing also contribute to the occurrence of the {SLA} biases. {A} detailed analysis of the thermohaline structure of the ocean reveals that the isopycnal lifting-lowering tends to diffuse vertically the main thermocline. {T}he impact on temperature is that the surface layer (0-200 m) becomes cooler whereas in deeper waters (from 500 to 1500 m), the ocean becomes slightly warmer. {T}his is particularly true in the tropics, between 30 degrees {N} and 30 degrees {S}. {H}owever it can be demonstrated that the assimilation improves the variability in both surface currents and sub-surface temperature in the {E}quatorial {P}acific {O}cean.},
  keywords = {data assimilation ; global ocean prediction ; altimetry ; sea level ; {GODAE}},
  booktitle = {},
  journal = {{J}ournal of {M}arine {S}ystems},
  volume = {65},
  numero = {1-4},
  pages = {540--560},
  ISSN = {0924-7963},
  year = {2007},
  DOI = {10.1016/j.jmarsys.2005.08.004},
  URL = {https://www.documentation.ird.fr/hor/fdi:010037928},
}