Climate Coupling in the Western Hemisphere and 2023 El Niño Onset

This research provides insights on tropical ocean–atmosphere climate coupling as Madden Julian Oscillation (MJO), Kelvin, and Rossby waves interact during the onset phase of the El Nino Southern Oscillation (ENSO). A statistical analysis of transient intra-seasonal modes from singular value decomposition of 5-day filtered satellite outgoing long-wave radiation anomalies 2001–2024 reveals the expected eastward propagation from the Pacific. Wavelet spectra exhibit well-known pulsing at 30–50 days from intra-seasonal MJO, and at 3–5 years from inter-annual ENSO. How they interact and amplify emerges from statistical analyses and a case study of El Niño onset in 2023. Eastward propagation (∼15 m s–1) of deep westerly anomalies from the east Pacific to the Atlantic, and simultaneous equatorial warming in both basins, distinguish it from past events.