Izumo Takeshi, Colin M. (2022). Improving and harmonizing El Nino recharge indices. Geophysical Research Letters, 49 (23), p. e2022GL101003 [10 p.]. ISSN 0094-8276.
Titre du document
Improving and harmonizing El Nino recharge indices
Geophysical Research Letters, 2022,
49 (23), p. e2022GL101003 [10 p.] ISSN 0094-8276
El Nino Southern Oscillation (ENSO) is the leading mode of interannual climate variability, with large socioeconomical and environmental impacts. The main conceptual model for ENSO, the Recharge Oscillator (RO), considers two independent modes: the fast zonal tilt mode in phase with central-eastern Pacific Temperature (T-e), and the slow recharge mode in phase quadrature. However, usual indices (western or equatorial sea level/thermocline depth h) do not orthogonally isolate the slow recharge mode, leaving it correlated with T-e. Furthermore the optimal index is currently debated. Here, we develop an improved recharge index by objectively optimizing the RO equations fit to observations. (a) T-e-variability is regressed out, to build h(ind) statistically-independent from T-e. Capturing the pure recharge, h(ind) reconciles usual indices. (b) The optimum is equatorial plus southwestern Pacific h(ind_eq+sw) (because of ENSO Ekman pumping meridional asymmetry). Using h(ind_eq+sw), the RO becomes more consistent with observations. h(ind_eq+sw) is more relevant for ENSO operational diagnostics.
Plan de classement
Sciences fondamentales / Techniques d'analyse et de recherche [020]
;
Sciences du milieu [021]
;
Limnologie physique / Océanographie physique [032]
