Diagnosing the stratosphere-troposphere stationary wave response to climate change in a general circulation model

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Abstract

[1] A stationary wave model (SWM) that captures the stratospheric and tropospheric stationary wave field is developed and applied to the problem of the stationary wave response to climate change. The SWM solution is controlled by damping settings that need to be tuned differently for observational and for modeling applications. The SWM is used to separately diagnose the effects of changes to the zonally asymmetric component of diabatic heating and of changes to the zonal mean basic state on the Northern Hemisphere winter stationary wave response to greenhouse gas forced climate change simulated by the Canadian Middle Atmosphere Model (CMAM). The SWM analysis shows that changes to the zonal mean basic state with diabatic heating held fixed explain much of the stationary wave response. In particular, changes to the zonal mean wind in the Northern Hemisphere subtropical upper troposphere dominate the subtropical and extratropical stationary wave response. CMAM simulates an increase in stratospheric wave driving in response to greenhouse forcing, in common with many climate models. In the SWM, this wave driving response, which is sensitive to the spatial structure of the waves, is not dominated by the subtropical jet response but involves several aspects of the zonal mean wind response and the diabatic heating response, all of which contribute to enhanced stratospheric wave driving.

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