Interplay between radiative base state and dynamics in a dry GCM

We will present and discuss the impact of a new treatment of the thermodynamic equilibrium state on simulations of the dynamics of the stratosphere and troposphere-stratosphere interactions. Dry primitive equation models are commonly used to analyze aspects of atmospheric dynamics. In these calculations, the atmosphere is relaxed against a predefined base state. Perturbation experiments may modify the relaxation temperature field, relaxation time scale, or the orography to force specific wave responses. We argue that nonlinearities in the dynamics require a careful construction of the base state. It has been shown by previous authors that the presence of a polar night vortex (of radiative origin) is crucial for realistic troposphere-stratosphere interactions. Similarly, we have recently shown that a relaxation temperature field and time scale based on radiative transfer calculations improves the seasonality of upwelling in the tropical lower stratosphere. Here, we present further analyses of the impact of the formulation of the thermodynamic equilibrium state on the sensitivity of the dynamical responses to perturbations in the base state. Specifically, we analyze nonlinear dynamical responses in experiments intended to represent idealizations of stratospheric ozone depletion, and global warming.