@article{fdi:010073733,
  title = {{S}ubseasonal coastal-trapped wave propagations in the {S}outheastern {P}acific and {A}tlantic {O}ceans : 1. {A} {N}ew approach to estimate wave amplitude},
  author = {{I}llig, {S}erena and {C}adier, {E}. and {B}achelery, {M}. {L}. and {K}ersale, {M}.},
  editor = {},
  language = {{ENG}},
  abstract = {{T}he {H}umboldt and the {B}enguela upwelling systems are connected to the equatorial variability through the coastal waveguide, so that a large variance of the coastal sea level and current variability can be described as an infinite sum of orthonormal free {C}oastal-{T}rapped {W}ave ({CTW}) modes. {T}he objective of this study is to infer the {CTW} mode contributions to the coastal variability in both systems at subseasonal timescales (<120 days) from regional ocean circulation model simulations. {W}e develop and validate twin regional model configurations of the southeastern {P}acific and {A}tlantic {O}ceans. {C}ross-shore spatial structures of the first four free {CTW} modes are then derived from model mean stratification and topography along the southwestern {A}frican and {S}outh {A}merican continents. {W}e introduce and validate a new methodology to estimate the gravest {CTW} mode contributions to model pressure and alongshore current. {O}ur formulation draws on the orthonormality of the {CTW} modal structures, and uses a simple projection of the coastal and bottom model pressure onto each {CTW} structure. {R}esults give confidence in the ability of this modal decomposition methodology to disentangle {CTW} mode contributions from complex nonlinear coastal processes that control the coastal subseasonal variability. {I}n both systems, it allows to successfully extract the gravest poleward propagating {CTW} modes with velocities close to the theoretical values and amplitudes consistent with the solutions of a simple multimode linear {CTW} model. {F}urthermore, results show that both systems exhibit relatively different {CTW} dynamics and forcings which are discussed in the companion paper ({I}llig et al., 2018). {P}lain {L}anguage {S}ummary {C}oastal-trapped waves propagate in the ocean along the continental shelves, with the coast on their left in the southern hemisphere. {T}hey exert an important influence on the coastal circulation and mixing, with notable implications for productive ecosystems. {W}e introduce a new methodology to estimate the amplitude of these waves and their contribution to the coastal sea level and alongshore current variability. {I}t benefits from a relatively simple implementation and is adapted to ocean model solutions. {W}e validate this method using twin regional ocean model configurations of the southeastern {P}acific and {A}tlantic {O}ceans. {T}his novel approach allows to successfully extract the contribution of the southward propagating coastal waves in these two different systems, with velocities close to the theoretical values and amplitudes consistent with the dynamics of a simple linear coastal model. {T}his gives confidence in the ability of this new technique to disentangle coastal wave contributions from complex nonlinear processes that control the ocean variability in coastal fringes. {F}urthermore, results show that both systems exhibit drastic differences in the coastal wave dynamics at subseasonal timescales (<120 days) which are discussed in the companion paper ({I}llig et al., 2018).},
  keywords = {coastal-trapped waves ; modal decomposition ; ocean model simulations ; linear coastal model ; subseasonal variability ; eastern boundary ; upwelling systems ; {PACIFIQUE} {SUD} {EST} ; {ATLANTIQUE} {SUD} {EST}},
  booktitle = {},
  journal = {{J}ournal of {G}eophysical {R}esearch : {O}ceans},
  volume = {123},
  numero = {6},
  pages = {3915--3941},
  ISSN = {2169-9275},
  year = {2018},
  DOI = {10.1029/2017jc013539},
  URL = {https://www.documentation.ird.fr/hor/fdi:010073733},
}