83 / 2021-07-16 22:54:49

Global impact of the Maritime Continent barrier effect on the MJO

MJO,Barrier effect,Tropical-extratropical teleconnections,Maritime Continent

The Maritime Continent disrupts eastward propagation of the Madden-Julian Oscillation (MJO). This study surveys the global impact of the disruption - the barrier effect. The MJO propagation may be broadly categorized based on whether the MJO precipitation crosses the Maritime Continent (MC) during extended boreal winter seasons: successfully propagating across the Maritime Continent (MJO-C) and being blocked by MC (MJO-B). Compositing atmospheric circulation upon these two categories reveals that precipitation anomalies of MJO-C are stronger and more coherent than that of MJO-B, while their phase speed and lifetime are comparable. MJO-C and MJO-B excite distinct extratropical responses due to their diabatic heating in the deep tropics. Mid-latitude circulation displays stronger and long-lasting negative geopotential anomalies in the northern Pacific Ocean 5-14 days after phase 7-8 of MJO-C, but significantly weaker anomalies for MJO-B. The extratropical water vapor transports of MJO-B and MJO-C differs markedly after phase 3. The Pacific-North American (PNA) pattern and North Atlantic Oscillation (NAO) both show significantly positive phase about 5-20 days after phase 6 of MJO-C since its precipitation anomaly over tropical Pacific during this period is stronger, while MJO-B has little impact on them, which might be due to the weak tropical precipitation and corresponding poleward-propagating Rossby wave trains. Surface air temperature (SAT) at high-latitude of MJO-B and MJO-C are also significantly different, as MJO-B shows much weaker amplitude and lagged evolution than MJO-C, likely due to their different meridional eddy heat fluxes.