Barrier for the Eastward Propagation of Madden-Julian Oscillation Over the Maritime Continent: A Possible New Mechanism

The Madden-Julian Oscillation (MJO) is the dominant intraseasonal variability of the tropical troposphere. Many MJOs originate from the tropical Indian Ocean and propagate into the Pacific via the Maritime Continent (MC). However, 30-50% of the MJO stalls over the MC, while its cause remains unclear. Here, we find that a new interbasin coupled phenomenon dubbed Warm Pool Dipole (WPD), which is associated with out-of-phase sea surface temperature anomalies (SSTAs) in the southeast Indian Ocean and the western central tropical Pacific, may play an important role in controlling the MJO propagation. During the positive WPD, similar to 67% of the MJO is stalled over the MC, whereas none is stalled during its negative phase. It is the SSTAs at both poles of the WPD together that produce these effects. The results are robust to cross-data set differences and supported by model experiments, although the small observational sample size limits their level of statistical significance.