How can we improve the driving of the Quasi-Biennial Oscillation in climate models?

Abstract

The Quasi-Biennial Oscillation (QBO) of zonal-mean zonal winds in the tropical stratosphere is a conspicuous feature of the Earth climate. Its influence virtually extends to the whole atmosphere. The QBO is driven by the dissipation of waves generated by deep convection in the tropics. Yet a significant fraction of these waves have spatial scales that are not explicitly resolved in current climate models, so that the evolution of the QBO in a changing climate still remains unclear. A study by Vincent and Alexander (2020, https://doi.org/10.1029/2020JD032779) shows that recent long-duration balloon observations, combined with information on the vertical structure of the tropical atmosphere, could contribute to provide significantly improved constraints on wave parameterization in models. Plain Language SummaryIn the tropics, the regular alternation with a period of ∼27 months of westward and eastward winds between 16-and 30-km altitude is known as the Quasi-Biennial Oscillation (QBO), and it influences the global atmospheric circulation in a variety of ways. The QBO results from the dissipation of atmospheric waves that propagate vertically in the atmosphere from their source region below 10-km altitude. These waves have horizontal scales ranging from some tens to some thousands of kilometers. The smaller-scale waves are not properly represented in current climate models, despite their importance in determining the characteristics of the QBO. A study by Vincent and Alexander (2020, https://doi.org/10.1029/2020JD032779), which has used observations collected on balloons that fly for months at 20-km altitude in the atmosphere, provides a new way to better characterize those waves, and hence improves the simulation of the QBO in climate models.