Low-Frequency Modulation of Intraseasonal Equatorial Kelvin Wave Activity in the Pacific from SODA: 1958-2001

Boris Dewitte (1) , Sara Purca (2) , Serena Illig (1) , Lionel Renault (1) , Benjamin S Giese (3)

1 LEGOS - Laboratoire d'études en Géophysique et océanographie spatiales
2 IMARPE - Instituto del Mar del Peru
3 Texas A&M University [College Station]

Intraseasonal equatorial Kelvin wave activity (IEKW) at a low frequency in the Pacific is investigated using the Simple Ocean Data Assimilation (SODA) oceanic reanalyses. A vertical and horizontal mode decomposition of SODA variability allows estimation of the Kelvin wave amplitude according to the most energetic baroclinic modes. A wavenumber-frequency analysis is then performed on the time series to derive indices of modulation of the IEKW at various frequency bands. The results indicate that the IEKW activity undergoes a significant modulation that projects onto baroclinic modes and is not related in a straightforward manner to the low-frequency climate variability in the Pacific. Linear model experiments corroborate that part of the modulation of the IEKW is tightly linked to change in oceanic mean state rather than to the low-frequency change of atmospheric equatorial variability.

Mots clés: Pacific Ocean; Ocean models; Kelvin waves; Intraseasonal variability

Domaines: Sciences de la Terre

Boris Dewitte, Sara Purca, Serena Illig, Lionel Renault, Benjamin S Giese. Low-Frequency Modulation of Intraseasonal Equatorial Kelvin Wave Activity in the Pacific from SODA: 1958-2001. Journal of Climate, 2008, 21 (22), pp.6060-6069. ⟨10.1175/2008JCLI2277.1⟩. ⟨hal-00409292⟩