Exploring the Propagation of the Madden-Julian Oscillation (MJO) across the Maritime Continent

The Maritime Continent MC is a region particularly susceptible to enhanced eastward-moving convective thunderstorm activity during the Madden-Julian Oscillation MJO active phase. To aid MJO predictability over the MC, atmospheric conditions across two vertical levels of the atmosphere were explored in this study a humidity and height in the troposphere, and b wind in the stratosphere. In both, the Wheeler-Hendon Real-Time Multivariate MJO RMM Index was used to categorize MJO events over the MC from 1980-2017 based on their strength entering and exiting the region. An empirical orthogonal function analysis was developed to identify phases of the stratospheric Quasi-Biennial Oscillation QBO by direction and altitude of zonal wind centers. In the troposphere, positive specific humidity anomalies within the MJO active envelope and a near-surface moisture foot region in the lower troposphere east of the active envelope favor MJO propagation. In the stratosphere, east-west winds during active events can indicate the likelihood of intense, eastward-moving MJO thunderstorm intensity over the MC. These MJO events over the MC are likely to remain strong when easterly westerly mid-stratospheric QBO wind anomalies develop during boreal winter spring and summer. When easterly mid-stratospheric wind anomalies are present, stratospheric temperature anomalies in thermal wind balance with the zonal wind anomalies decrease the upper-tropospheric and lower-stratospheric stability, aiding deep convection and favoring a stronger MJO. Mechanisms which explain the seasonality of this relationship are suggested areas for future research, as well as mechanisms which account for the boreal spring and summer QBO-MJO relationship.