This study investigates how regional patterns of tropical sea surface temperature (SST) warming influence the propagation characteristics of the Madden–Julian Oscillation (MJO)—a key driver of intraseasonal tropical variability with widespread global impacts. Despite its importance, the sensitivity of MJO propagation to SST pattern changes has remained poorly understood. Read more here.
By comparing two distinct periods—Period 1 (1979–1998) and Period 2 (2003–2022)—the research demonstrates that a La Niña-like shift in SST patterns around 1999 has led to regionally divergent changes in MJO propagation speed: 7.1% acceleration over the Indian Ocean, 5.4% acceleration over the Maritime Continent, but 17.6% deceleration over the western Pacific.
These variations are attributed to changes in low-level moisture gradients, vertical motion, and upper-tropospheric stability. Over the Indian Ocean, enhanced zonal moisture gradients and stronger upward motion support faster propagation. However, over the western Pacific, weakened moisture gradients and suppressed convection inhibit propagation. Over the Maritime Continent, despite complex terrain and atmospheric dynamics, recent mean-state changes still promote faster MJO movement.
This research is significant in that it quantifies for the first time the regional sensitivity of MJO propagation to SST pattern changes, improving the physical understanding of ocean-atmosphere interactions. The findings have broad implications for subseasonal and long-range climate prediction. By clarifying how MJO behavior is modulated by evolving SST patterns, this work contributes to advancing predictive capabilities under ongoing climate change.