A simple estimation of equatorial Pacific response from windstress to untangle Indian Ocean Dipole and Basin influences on El Niño

摘要: Sea Surface Temperature (SST) anomalies that develop in spring the central Pacific are crucial to El Nino Southern Oscillation (ENSO) development. Here we use a linear, continuously stratified, ocean model, and its impulse response typical ENSO wind pattern, derive simple equation relates those SST low frequency evolution of zonal stress τ x over preceding months. We show can be approximated as “causal” filter , τ (t − t 1) − c τ 2), where t1 is ~1–2 months, t2 − t1 ~6 months c ranges between 0 1 depending on location (i.e. approximately proportional 1–2 months earlier minus fraction 7–8 months earlier). The first term represents fast oceanic response, while second one delayed negative feedback associated with wave reflection at both boundaries. This approach then applied assess relative influence Indian Ocean Dipole (IOD) Basin-wide warming/cooling (IOB) favouring phase transition ENSO. In agreement previous studies, Atmospheric General Circulation Model experiments indicate equatorial responses IOD eastern (IOB-related) western poles tend cancel out during autumn. abrupt demise pole thus favours an development IOB-cooling-forced westerly winter–spring (vice versa for IOB warming). As expected from above, faster change fostered by enhances compared sole influence. thereby tendency favour transition. more independent than IOB, this external could contribute enhanced predictability.