Calibration and Uncertainty Quantification of a Gravity Wave Parameterization: A Case Study of the Quasi-Biennial Oscillation in an Intermediate Complexity Climate Model

Atmospheric gravity waves are excited in the lower atmosphere by disturbances such as mountains, convection and fronts. They travel upwards and break in the upper atmosphere, thus modifying the mean flow. This has large effects on the circulation, including driving a tropical oscillation. Gravity waves have a wide range of spatial scales and a large portion of these are smaller than the grid size of a climate model. This means they cannot be resolved and instead, they are represented through approximations called “parameterizations”, which introduce a source of uncertainty in climate model output. In this study, we tune a parameterization so that the model produces an oscillation in the tropical middle atmosphere, with a defined period and amplitude, which is one of the main features of the climate driven primarily by gravity waves. We also explore uncertainties associated with the parameterization.