@article{fdi:010086055,
  title = {{D}irect and rectified effects of {T}ropical instability waves on the {E}astern {T}ropical {P}acific mean state in a regional ocean model},
  author = {{M}aillard, {L}. and {B}oucharel, {J}. and {R}enault, {L}ionel},
  editor = {},
  language = {{ENG}},
  abstract = {{T}ropical instability waves ({TIW}s) are oceanic features propagating westward along the northern front of the {P}acific cold tongue. {O}bservational and modeling studies suggest that {TIW}s may have a large impact on the eastern tropical {P}acific background state from seasonal to interannual time scales through heat advection and mixing. {H}owever, observations are coarse or limited to surface data, and modeling studies are often based on the comparison of low- versus high-resolution simulations. {I}n this study, we perform a set of regional high-resolution ocean simulations ({CROCO} 1/12 degrees) in which we strongly damp ({NOTIW}s-{RUN}) or not ({TIW}s-{RUN}) {TIW} propagation, by nudging meridional current velocities in the {TIW} region toward their monthly climatological values. {T}his approach, while effectively removing {TIW} mesoscale activity, does not alter the model internal physics in particular related to the equatorial {K}elvin wave dynamics. {T}he impact of {TIW}s on the oceanic mean state is then assessed by comparing the two simulations. {W}hile the well-known direct effect of {TIW} heat advection is to weaken the meridional temperature gradient by warming up the cold tongue (0.34 degrees {C} month(-1)), the rectified effect of {TIW}s onto the mean state attenuates this direct effect by cooling down the cold tongue (-0.10 degrees {C} month(-1)). {T}his rectified effect occurs through the {TIW}-induced deepening and weakening of the {E}quatorial {U}ndercurrent, which subsequently modulates the mean zonal advection and counterbalances the {TIW}s' direct effect. {T}his approach allows quantifying the rectified effect of {TIW}s without degrading the model horizontal resolution and may lead to a better characterization of the eastern tropical {P}acific mean state and to the development of {TIW} parameterizations in {E}arth system models. {S}ignificance {S}tatement{T}ropical instability waves ({TIW}s), meandering features at the surface of the equatorial {P}acific {O}cean, have long been recognized as a key component of the climate system that can even impact marine ecosystems. {Y}et, they are still hardly simulated in coupled global climate models. {H}ere, we introduce a new framework to isolate and quantify their complex influence on the tropical {P}acific background climate. {T}his approach allows revealing a so far overlooked effect of {TIW}s on the mean circulation and heat transport in this region that should be accounted for in the next generation of global coupled climate models through parameterization or increased resolution.},
  keywords = {{M}esoscale processes ; {O}cean models ; {T}ropical variability ; {O}cean dynamics ; {H}eat budgets fluxes ; {PACIFIQUE} ; {ZONE} {TROPICALE} ; {PACIFIQUE} {EST}},
  booktitle = {},
  journal = {{J}ournal of {P}hysical {O}ceanography},
  volume = {52},
  numero = {8},
  pages = {1817--1834},
  ISSN = {0022-3670},
  year = {2022},
  DOI = {10.1175/jpo-d-21-0300.1},
  URL = {https://www.documentation.ird.fr/hor/fdi:010086055},
}