A modeling framework to study interaction between resolved and parameterized waves

We present an idealized Atmospheric General Circulation Model (AGCM) designed to explore the interactions between parameterized gravity waves and the resolved circulation. The model is based on an AGCM used in recent studies to explore coupling between the stratosphere and troposphere. In the earlier model, the effect of gravity waves on the stratospheric circulation was parameterized as Rayleigh friction near the model lid, which can lead to physically inconsistent circulations that do not conserve momentum. This crude parameterization is replaced with orographic and non-orographic gravity wave parameterizations which are similar to those used in state-of-the-art coupled climate models. We first verify that the main results from the model with Rayleigh friction are robust: a strengthened polar vortex in the stratosphere leads to a poleward shift in the tropospheric jet stream, both for climatological changes in the stratospheric forcing and for natural variations of the vortex. We then focus on the coupling between parameterized gravity waves and resolved planetary waves during Stratospheric Sudden Warming events, comparing the model with recent observational estimates of gravity wave activity during sudden warmings.