FY 2024

The Indo-Pacific Maritime Continent barrier effect on MJO ensemble prediction

Abhik, S., C. Zhang, and H.H. Hendon

Geophys. Res. Lett., 50(21), e2023GL105462, doi: 10.1029/2023GL105462, View open access article at AGU/Wiley (external link) (2023)

The barrier effect of the Indo-Pacific Maritime Continent (MC) on the Austral summertime Madden-Julian Oscillation (MJO) is explored using retrospective forecasts from subseasonal-to-seasonal (S2S) prediction models. The general MJO prediction skills in the S2S models are evaluated and the top-performing models are identified. We select two sets of observed MJO events - continuously propagating across the MC into the western Pacific (WP) and blocked by the MC. The continuously propagating MJO events are better predicted than the blocked MJO events for their systematic eastward propagating behavior, especially in the ocean-atmosphere coupled models. Although the best four models and their ensemble consistently produce greater prediction skills of the continuously propagating MJOs, the all-model ensemble is not better than the top-performing models. Our analysis suggests that a realistic representation of air-sea interaction over the WP is crucial for better MJO prediction.

Plain Language Summary.The eastward propagating Madden-Julian Oscillation (MJO) is weakened or sometimes ceases across the Maritime Continent (MC) islands. We explore this MC “barrier effect” on the Austral summer MJO prediction in 13 multiweek prediction models. The top four MJO prediction models better predict the continuously propagating MJOs than the MJO events that fail to cross the MC. The all-model average performance is inferior to top-performing models. The ocean-atmosphere coupled models produce more realistic eastward propagation than atmospheric-only models, which suggests that air-sea interaction is critical for improving MJO prediction.