Modeling the coupled stratosphere-troposphere stationary wave response to climate change

Stationary wave models are simplified atmospheric models that elucidate the dynamics of the climatological mean zonally asymmetric component of the atmospheric circulation. We here apply a recently developed stationary wave model that captures both the stratospheric and tropospheric stationary wave field to the question of the stationary wave response to climate change. Past stationary wave models largely focused on tropospheric circulation, but the stationary wave field extends into the stratosphere and plays an important dynamical role there. Our model is able to represent the stratospheric stationary wave field and its possible coupling to the troposphere. We use the model to diagnose the stationary wave response to climate change in Chemistry-Climate Model simulations. Our model allows us to separately diagnose the effects of changes to the zonally asymmetric component of diabatic heating and changes to the zonal mean basic state on the climate response. We find that in these simulations changes in the zonal mean basic state play a major role in explaining the changes in the stationary wave field. The statosphere-troposhpere dynamical coupling was explored by dividing the stationary wave response into four components: the response in the stratosphere / troposphere induced by the forcing in the stratosphere / troposphere. The stratospheric stationary wave field primarily results from the forcings from troposphere, while stratospheric diabatic heating has a minor impact on the tropospheric stationary waves; this impact is seen most strongly in the tropics and subtropics.