Tropical sea surface temperature (SST) warming displays pronounced regional contrasts, yet its influence on Madden–Julian Oscillation (MJO) propagation remains unclear. This study investigates how a shift toward La Niña-like conditions around 1999 affected MJO propagation by comparing two periods: 1979–1998 and 2003–2022. Analyses of satellite observations and reanalysis datasets reveal that MJO propagation has accelerated over the Indian Ocean and the Maritime Continent but slowed over the western Pacific in the later period. These contrasting responses arise from regionally distinct SST and atmospheric changes: enhanced low-level moisture gradients and greater upper-tropospheric stability over the Indian Ocean favor faster propagation, whereas weakened gradients and reduced convective activity over the western Pacific inhibit it. Despite the complex terrain and atmospheric variability of the Maritime Continent, background conditions there also promote enhanced propagation. These results highlight the sensitivity of MJO dynamics to regional ocean–atmosphere states and provide guidance for improving subseasonal climate prediction.
 

Madden-Julian Oscillation,propagation speed,moisture distribution,dry static energy,uneven SST warming