Extratropical Responses to MJO Under Different Phases of QBO Using Linear Baroclinic Model (LBM)

The interaction between the Madden–Julian Oscillation (MJO) and the Quasi-Biennial Oscillation (QBO) has the potential to influence extratropical atmospheric conditions through its impact on atmospheric dynamics. It has been observed that the strength of the MJO varies between the westward phase of the QBO (W-QBO) and the eastward phase (E-QBO). This research aims to conduct a thorough analysis of the extratropical responses to MJO occurrences during both E-QBO and W-QBO phases, with a specific focus on teleconnections to extratropical areas, utilizing a Linear Baroclinic Model (LBM). We demonstrate that the presence of the QBO during MJO propagation significantly affects convective activity, leading to changes in diabatic heating in the tropics, which, in turn, drive different MJO teleconnection responses. Notably, E-QBO exhibits stronger MJO teleconnections, as indicated by geopotential height anomalies that result in the formation of high and low-pressure systems in the Pacific region. This is consistent with stronger diabatic heating during E-QBO that enhances Rossby wave source, consequently leading to a more pronounced propagation of Rossby wave trains toward mid-latitudes approximately two weeks after each MJO phase in the respective QBO phases is initialized in the LBM. The discrepancy between model and observational MJO teleconnection responses underscore the importance of incorporating nonlinear dynamics to fully understand the MJO teleconnection responses in extratropical regions.