Planetary wave drag: Theory, observation and its role in shaping the general circulation

Abstract

Breaking planetary waves in the wintertime stratospheric surf-zone are associated with a local loss of angular momentum, or 'drag' force. This drag force is, among other things, responsible for driving the Brewer-Dobson circulation. The concept of planetary wave drag is investigated using zonal mean quasi-geostrophic theory. In particular, quasi-geostrophic potential vorticity is used to describe the coupled interactions between planetary waves, the polar vortex and the stratospheric surf-zone. Theory is complemented with observation using reanalysis data. To study the role of planetary wave drag in shaping the general circulation, a parameterization of planetary wave drag is implemented in a zonal mean model of the atmosphere. Results from quasi-geostrophic theory are used to interpret the model output. Model performance with respect to the observed climatology is quantified with the use of Taylor-diagrams. Furthermore, a selection of quasi-geostrophic results are tested and expanded upon using novel numerical cyclo-geostrophic piecewise PV-inversion experiments with Rossby-Ertel PV-configurations.