@article{fdi:010076045,
  title = {{D}iversity of moderate {E}l {N}ino events evolution : role of air-sea interactions in the eastern tropical {P}acific},
  author = {{D}ewitte, {B}oris and {T}akahashi, {K}.},
  editor = {},
  language = {{ENG}},
  abstract = {{I}n this paper we investigate the evolution of moderate {E}l {N}ino events during their developing phase with the objective to understand why some of them did not evolve as extreme events despite favourable conditions for the non-linear amplification of the {B}jerknes feedback (i.e. warm {SST} in {A}ustral winter in the eastern equatorial {P}acific). {A}mong the moderate events, two classes are considered consisting in the {E}astern {P}acific ({EP}) {E}l {N}ino events and {C}entral {P}acific ({CP}) events. {W}e first show that the observed {SST} variability across moderate {E}l {N}ino events (i.e. inter-event variability) is largest in the far eastern {P}acific (east of similar to 130 degrees {W}) in the {A}ustral winter prior to their peak, which is associated to either significant warm anomaly (moderate {EP} {E}l {N}ino) or an anomaly between weak warm and cold (moderate {CP} {E}l {N}ino) as reveals by the {EOF} analysis of the {SST} anomaly evolution during the development phase of {E}l {N}ino across the {E}l {N}ino years. {S}ingular value decomposition ({SVD}) analysis of {SST} and wind stress anomalies across the {E}l {N}ino years further indicates that the inter-event {SST} variability is associated with an air-sea mode explaining 31% of the covariance between {SST} and wind stress. {T}he associated {SST} pattern consists in {SST} anomalies developing along the coast of {E}cuador in {A}ustral fall and expanding westward as far as 130 degrees {W} in {A}ustral winter. {T}he associated wind stress pattern features westerlies (easterlies) west of similar to 130 degrees {W} along the equator peaking around {J}une-{A}ugust for {EP} ({CP}) {E}l {N}ino events. {T}his air-sea mode is interpreted as resulting from a developing seasonal {B}jerknes feedback for {EP} {E}l {N}ino events since it is shown to be associated to a {K}elvin wave response at its peak phase. {H}owever equatorial easterlies east of 130 degrees {W} emerge in {S}eptember that counters the growing {SST} anomalies associated to the air-sea mode. {T}hese have been particularly active during both the 1972 and the 2015 {E}l {N}ino events. {I}t is shown that the easterlies are connected to an off-equatorial southerly wind off the coast of {P}eru and {E}cuador. {T}he southerly wind is a response to the coastal {SST} anomalies off {P}eru developing from {A}ustral fall. {I}mplications of our results for the understanding of the seasonal {ENSO} dynamics and diversity are discussed in the light of the analysis of two global climate models simulating realistically {ENSO} diversity({GFDL}_{CM}2.1 and {CESM}).},
  keywords = {{PACIFIQUE} ; {ZONE} {TROPICALE}},
  booktitle = {},
  journal = {{C}limate {D}ynamics},
  volume = {52},
  numero = {12},
  pages = {7455--7476},
  ISSN = {0930-7575},
  year = {2019},
  DOI = {10.1007/s00382-017-4051-9},
  URL = {https://www.documentation.ird.fr/hor/fdi:010076045},
}