Quasi-Biennial Oscillation in a warming world

The quasi-biennial oscillation (QBO) of the zonal wind is a prominent feature of the tropical lower stratosphere. The easterly and westerly wind regimes have been alternating with an average period of about 28 months during the last 50 years. The QBO is forced by a combination of upward propagating Kelvin and mixed-Rossby gravity waves as well as by smaller scale gravity waves that are primarily generated in the tropics by convection. In this study, we examine the potential changes to the QBO in a warming climate by performing simulations in 2xCO2 and 4xCO2 scenarios. In our study we use the 60-level configuration of the Community Atmosphere Model, version 5 (60LCAM5), which generates an internally generated QBO. In this model, the convective gravity wave parameterization is coupled to the convection parameterization, and hence the QBO responds both to changes in planetary waves and changes in gravity waves in a warmer world.