The Global Teleconnection Signature of the Madden‐Julian Oscillation and Its Modulation by the Quasi‐Biennial Oscillation

Abstract

Recent research has suggested that the tropical and extratropical character of the Madden‐Julian oscillation (MJO) depends on the state of the stratospheric quasi‐biennial oscillation (QBO). With this in mind, we use both reanalysis and a global climate model (CESM2‐WACCM) to analyze the global character of upper tropospheric‐lower stratospheric geopotential height anomalies connected with the MJO and quantify dependencies of these teleconnections on the state of the QBO. We find that the global teleconnection signature of the MJO depends upon the state of the QBO. Globally, within reanalysis the fraction of 20‐ to 90‐day 250‐hPa geopotential height variance linked to the MJO is largest during boreal winter and summer for easterly QBO phases and smallest during westerly QBO phases of boreal winter. The difference between QBO phases is mostly driven by changes in the tropical signature of the MJO, although during boreal winter the Northern Hemispheric teleconnections are particularly more prominent during easterly QBO phases. Otherwise, the QBO modulation of extratropical MJO teleconnections is mainly realized through changes in the locations of the teleconnections. A QBO‐MJO relationship is also apparent within CESM2‐WACCM but is weaker than that observed. This extratropical modulation implies that the regions that benefit from increased subseasonal predictability due to the MJO may also change as a function of the QBO. In a broader sense, these findings emphasize that knowledge of the tropical stratospheric state, particularly as it relates to the QBO, is important for understanding the connections between the MJO and the extratropics.

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“…The MJO teleconnection patterns over the North Pacific are also subject to strong modulations by the QBO. During EQBO winters, the PNA‐like Rossby wave teleconnection pattern over the North Pacific is more pronounced than the WQBO winters (Son et al, 2017; Toms et al, 2020; J. Wang, Kim, et al, 2018). The MJO‐related North Pacific storm track (NPST) variability exhibits larger amplitude during EQBO than WQBO.…”

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“…The fact that upper-tropospheric anomalies are most relevant to the MJO during boreal winter may explain the seasonality in coupling between the MJO and the stratosphere (Son et al, 2017;Densmore et al, 2019;Toms et al, 2020). Previous research has hypothesized that the MJO can be modulated by sources of stratospheric variability such as the quasi-biennial oscillation through a downward influence of upper-tropospheric temperature anomalies (Abhik and Hendon, 2019;Martin et al, 2020).…”

“…While we will focus on the tropical characteristics of the MJO, it is also generally accepted that the atmospheric response to deep convective heating within the MJO can generate teleconnection patterns across the globe (e.g., Roundy et al, 2010;Tseng et al, 2019;Toms et al, 2020). The formation and propagation of the MJO are not as well understood, although numerous theories have been put forth (Zhang et al, 2020), one of which suggests that the MJO propagates in response to gradients of tropical water vapor anomalies (Sobel and Maloney, 2013;Adames and Kim, 2016).…”

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“…Moreover, the QBO is strongly related to modulations in the Madden-Julian Oscillation (MJO) 84,85 : the easterly QBO is linked to a more active and persistent MJO in boreal winter, although the mechanism remains uncertain. The QBO can alter the teleconnections of the MJO [86][87][88] , and thus by extension, its extreme impacts. For example, when the QBO winds are easterly, there is stronger and more organized precipitation over east Asia during certain MJO phases 89 and stronger MJO-related modulations of the amplitude and structure of the North Pacific storm track 90 .…”