Global response of stratospheric gravity waves to Madden-Julian Oscillation

The Madden-Julian Oscillation (MJO) is a dominant mode of intraseasonal variability in the tropical troposphere. While the MJO is a slow-moving oscillation that does not propagate to high altitude, it's impacts on the broader spectrum of waves can be seen throughout the middle atmosphere. The influence of this ∼30–90 day oscillation on stratospheric gravity waves (GWs) is not just confined to the tropics but extends to high-latitudes. In this study, we use long-term (1979–2018) reanalysis data to investigate the global stratospheric GW response to MJO during the boreal and austral winter months of December, January, February (DJF) and June, July, August (JJA), respectively. In DJF, the MJO GW relative anomalies are in general significant in both hemispheres during all eight MJO phases. In JJA, the GW relative anomalies are stronger in the winter hemisphere compared to the summer hemisphere. In the low- and mid-latitudes, the GW response in the troposphere depends on the strength of the convection, while the stratospheric response is related to the zonal wind response and filtering of upward propagating GWs. The strength and spatial pattern of GW anomalies in the high-latitude winter hemisphere in MJO Phases 4 and 7 may be connected to the dissipation of MJO related poleward propagating planetary waves.