4.7 Article

The Indo-Pacific Maritime Continent Barrier Effect on MJO Prediction

Journal

JOURNAL OF CLIMATE
Volume 36, Issue 3, Pages 945-957

Publisher

AMER METEOROLOGICAL SOC
DOI: 10.1175/JCLI-D-22-0010.1

Keywords

Maritime Continent; Atmosphere-ocean interaction; Madden-Julian oscillation; Forecast verification; skill; Subseasonal variability; Tropical variability

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Recent research has shown that the Madden-Julian oscillation (MJO) tends to weaken or decay when its convective anomaly moves over the Maritime Continent (MC), known as the MC barrier effect. This study found that the predictive skill of the real-time multivariate MJO (RMM) index is higher for continuously propagating MJO events compared to blocked events. The persistence of the propagating MJO events as they move through the MC region contributes to the higher prediction skill.
The Madden-Julian oscillation (MJO) is often observed to weaken or sometimes completely decay as its convective anomaly moves from the Indian Ocean over to the Maritime Continent (MC), which is known as the MC barrier effect on the MJO. This barrier effect is often exaggerated in numerical models. Using 23 years of the retrospective intraseasonal forecast from two coupled model systems with useful MJO prediction skills, we show that the predictive skill of the real-time multivariate MJO (RMM) index for the continuously propagating MJO events across the MC region is higher than for the blocked MJO events. The greater prediction skill is not related to the higher initial RMM amplitude for the continuous MJO events. Rather the higher skill arises from the more persistent behavior of the propagating MJO events as the convective anomaly moves through the MC region into the western Pacific. The potential predictability is similar for both types of MJO events, suggesting the forecast models hardly differentiate the two types of MJO events in prediction; they only maintain higher RMM magnitudes of the continuously propagating events. The global reanalysis dataset indicates that the blocked events are often associated with persistent higher surface pressures over colder sea surface temperatures in the central Pacific, suggesting the large-scale environment plays a role in promoting or inhibiting the MJO propagation across the MC region. Caveats in the models to reproduce the observed MJO events are also discussed.

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