The coupling of MJO with oceanic Kelvin waves in the three major oceanic basins

The Madden-Julian Oscillation (MJO) is a critical component of tropical intraseasonal variability, influencing global weather patterns. This study investigates the interaction between the MJO and oceanic waves, specifically Kelvin waves, using indices from Wheeler and Hendon (2004) for the MJO and Rydbeck (2019) for sea surface height (SSH) anomalies. Our methodology involves cross-referencing the phases of the MJO with the phases of the Kelvin Index. We contrast the MJO days with significant oceanic Kelvin wave activity with those when the Kelvin wave signal is weak. By analyzing these intersections, we aim to elucidate the coupling of oceanic waves and the MJO across the three major ocean basins.

Our findings indicate that during significant Kelvin wave activity, there is enhanced convection and more clearly defined oceanic wave structures within the MJO phases in the Pacific basin. This suggests a strong coupling between atmospheric and oceanic processes, where the presence of Kelvin waves can amplify convective activity associated with the MJO. Additionally, we observed that during periods of weak Kelvin wave signals, the MJO tends to be weaker, with more diffuse wave structures. Conversely, in the Atlantic basin, MJO’s impact on ocean Kelvin waves involves episodes of atmospheric convective anomalies over the Amazon, which tend to be related with stronger MJO previous activity in the western Pacific. For the Indian basin, the methodology is able to discriminate the oceanic Kelvin waves triggered by equatorial wind stress anomalies associated with MJO.

We also evaluate 30-yr long simulations from storm-resolving coupled models performed in the framework of EU-NextGEMS project to evaluate their performance in simulating MJO’s footprint on the ocean.

This study provides new insights into the complex dynamics of the MJO and its interaction with oceanic waves, highlighting the importance of considering both atmospheric and oceanic components in understanding tropical variability. The results have significant implications for improving the predictability of the MJO and its associated weather impacts, offering potential advancements in climate modeling and forecasting.