Influence of the MJO on Stratospheric Equatorial Waves During Different QBO regimes

Abstract:

The Quasi-Biennial Oscillation (QBO) is driven by upward transfers of momentum from a combination of equatorial waves and gravity waves, whose upward propagation are forced by deep convection and modulated by the QBO itself. Here, we examine the influence of the Madden-Julian Oscillation (MJO), the leading mode of atmospheric intraseasonal variability, on stratospheric equatorial wave activity. Equatorial waves are identified using wavenumber-frequency wavelet analysis based on the MERRA-2 and Atmospheric Infrared Sounder (AIRS) data, then isolated in different QBO regimes and MJO phases. Regressions against wavelet transforms show the structure and interactions of the equatorial waves. While there are differences between the datasets, results suggest increased Kelvin wave activity for zonal and temporal scales associated with shallower equivalent depths in the stratosphere during the MJO, especially during easterly QBO conditions. Changes in stratospheric equatorial wave activity due to the MJO may then affect the evolution of the QBO, in ways that vary based on QBO regime.