Speaker: Kevin DellaSanta (GISS/NPP)
Topic: The QBO in GISS modelE2.2: Future changes and historical trends

Building upon earlier middle atmosphere configurations of GISS models (Rind et al. 2014), E2.2 includes a spontaneously generated Quasi-Biennial Oscillation (QBO) in the tropical stratosphere (Rind et al. 2020, Orbe et al. 2020). Relative to other models, a strength of the GISS QBO is to include convection as a source of gravity waves (Rind et al. 1988). This allows climate change to impact the QBO more directly by altering its dominant momentum source. We investigate past and future changes to the QBO using a wide range of E2.2 integrations. Both the QBO period and amplitude are projected to decrease, dynamically interpretable in terms of changes to convection and upwelling, respectively. Novel aspects of our findings include the role of composition feedbacks, the impact of volcanic eruptions, and the presence of regular disruptions. Certain aspects are more robust while others appear quite sensitive to the basic state, and the results suggest directions for achieving improvements in the model.