@article{fdi:010092260,
  title = {{E}quatorial {P}acific cold tongue bias degrades simulation of {ENSO} asymmetry due to underestimation of strong {E}astern {P}acific {E}l {N}iños},
  author = {{B}ayr, {T}. and {L}uebbecke, {J}. {F}. and {V}ialard, {J}{\'e}r{\^o}me and {L}atif, {M}.},
  editor = {},
  language = {{ENG}},
  abstract = {{E}l {N}iño-{S}outhern {O}scillation ({ENSO}) exhibits a considerable asymmetry in sea surface temperature anomalies ({SST}a), as {E}l {N}iño events tend to be stronger and centered further east than {L}a {N}iña events. {H}ere, we analyze {ENSO} asymmetry in observations and preindustrial control integrations of 32 models participating in phase 6 of the {C}oupled {M}odel {I}ntercomparison {P}roject ({CMIP}6). {O}bservations indicate a significant link between strong eastern {P}acific ({EP}) {E}l {N}iño events and the {ENSO} amplitude and asymmetry. {T}he large {CMIP}6 database confirms this strong link. {M}ost {CMIP}6 models suffer from an equatorial {P}acific cold {SST} bias. {T}his cold tongue bias hinders the southward migration of the {ITCZ} toward the equator over the eastern equatorial {P}acific, which is characteristic of strong {EP} {E}l {N}iño events in observations. {T}herefore, many models underestimate the eastern equatorial {P}acific rainfall anomalies and simulate a wind stress feedback over the western {P}acific that is too weak and too far west. {A}s a result, the cold tongue bias exerts a strong control on the climate models' ability to generate strong {EP} {E}l {N}iño events and therefore on the {ENSO} overall amplitude and asymmetry. {W}e discuss the relevance of these results in view of a potential increase of strong {EP} {E}l {N}iño events under global warming. {SIGNIFICANCE} {STATEMENT}: {E}l {N}iño and {L}a {N}iña are asymmetric, as {E}l {N}iño events tend to be stronger and further east than {L}a {N}iña events. {D}ue to an equatorial {P}acific cold tongue bias with too cold {SST}s, the simulation of {ENSO} asymmetry is degraded in many climate models participating in {CMIP}6. {H}ere, we show how the cold tongue bias influences {ENSO} asymmetry. {T}he cold bias hampers the simulation of strong eastern {P}acific {E}l {N}iños by making it more difficult for {SST} to exceed the threshold for deep atmospheric convection over the eastern equatorial {P}acific. {R}ecent research indicates that climate models with a realistic {ENSO} asymmetry agree on the projected {ENSO} under global warming. {T}he results of this study suggest that reducing the cold tongue bias has the potential to enhancing the reliability of future {ENSO} projections.},
  keywords = {{P}acific {O}cean ; {A}tmosphere-ocean interaction ; {ENSO} ; {N}onlinear dynamics ; {C}oupled models ; {M}odel errors ; {PACIFIQUE} ; {ZONE} {EQUATORIALE}},
  booktitle = {},
  journal = {{J}ournal of {C}limate},
  volume = {37},
  numero = {23},
  pages = {6167--6182},
  ISSN = {0894-8755},
  year = {2024},
  DOI = {10.1175/jcli-d-24-0071.1},
  URL = {https://www.documentation.ird.fr/hor/fdi:010092260},
}