Abstract
AbstractThe circulation of the stratosphere is strongly influenced by the fluxes of gravity waves propagating from tropospheric sources. In the tropics, these gravity waves are primarily generated by convection. The Madden‐Julian Oscillation (MJO) dominates the intraseasonal variability of this convection. However, the influence of the MJO on the variability of stratospheric gravity waves is largely unknown. Here we examine gravity wave potential energy at 26 km and the upper tropospheric zonal wind anomaly of the MJO at 200 hPa, sorted by the relative phase of the MJO using the Real Multivariate MJO indices. We show that a strong anticorrelation exists between gravity wave potential energy and the MJO eastward wind anomaly. We propose that this correlation is a result of the filtering of upward propagating waves by the MJO winds. The study provides the first observational evidence that the MJO contributes significantly to the global variability of stratospheric gravity waves in the tropics.
Highlights
Gravity waves play a very important role in the dynamics of the stratosphere
We show that a strong anticorrelation exists between gravity wave potential energy and the Madden-Julian Oscillation (MJO) eastward wind anomaly
The variances of the 2–180 day and MJO period range gravity wave potential energies (GWPE) are more widely distributed around the tropics
Summary
Gravity waves play a very important role in the dynamics of the stratosphere. The waves can propagate upward from their sources in the troposphere upward to greater heights, resulting in a vertical flux of energy and horizontal momentum. Deep tropospheric convection associated with cumulus clouds is the main source of gravity waves [e.g., Alexander et al, 2008; Wright and Gille, 2011]. Such tropical waves drive important features of the tropical stratospheric circulation, including the quasi-biennial oscillation (QBO) and semiannual oscillation (SAO) [e.g., Hamilton et al, 2004]. Measurements of the fluxes and variability of gravity waves and how these are related to their sources are essential in efforts to understand the dynamics of the stratosphere and in efforts to develop numerical weather prediction and climate models [e.g., Fritts and Alexander, 2003; Alexander et al, 2010]
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