Diverse controlling mechanisms and teleconnections of three distinctive MJO types

In this diagnostic study, three distinctive MJO types in boreal winter are documented and their controlling mechanisms and teleconnections are investigated with a synergetic glocal approach. It is revealed that the diverse nature of the MJO primarily results from different tropical-extratropical interactions and associated internal atmospheric processes. Both the type-I and type-II are initiated over the western Indian Ocean (IO) by a dry zone around the eastern IO (EIO), while only the type-I can move out the IO and circulate around the globe. The type-III initiates over the western Pacific (WP) and can circulate the globe. The strong upper-level equatorial westerly wind over the IO-WP, resulting from upstream and extratropical influences, suffocates the type-II MJO within the IO. Whereas, the robust upper-level equatorial easterly wind over the IO-WP, also resulting from upstream and extratropical influences, along with regional convective instability over the WP and the arrival of cold surge over the South China Sea (SCS) foster the development and eastward propagation of the type-III MJO. The downstream and extratropical teleconnections are primarily controlled by the associated convection over the tropical IO-WP sector for the type-I, but also strongly influenced by the conditions over the extratropical WP for the type-II and type-III. Given that the MJO has been traditionally viewed as a tropical mode owing its existence to the coupling between organized convection and large-scale circulations, present findings advocate the MJO as a glocal mode and call for more research on the involved tropical-extratropical interactions in order to better understand and simulate the diverse nature of the MJO.