Impact of zonal variations in ozone on stratosphere-troposphere coupling

Recent studies indicate that the depletion and recovery of Antarctic ozone plays a major role in changes in SH tropospheric climate. Furthermore, the impact of ozone changes on tropospheric climate in the climate models used in the IPCC fourth assessment (AR4) is much weaker than in stratosphere-resolving chemistry climate models (CCMs). It is not known whether this is because of the lack of interactive chemistry, incorrect specification of the ozone, or inadequate representation of the stratospheric circulation in the AR4 models, or lack of a coupled ocean in the stratospheric CCMs. We report here on a series of GEOS CCM experiments to examine the impact of prescribing ozone on the stratospheric flow and coupling with the troposphere. Simulations with the full, interactive stratospheric chemistry are compared with identical simulations using the same CCM except that the monthly-mean zonal-mean stratospheric ozone from first simulation is prescribed (as in AR4 models). Consistent with previous comparisons of multi-model means from CCMs and from AR4 models, there is a weaker response in both the stratosphere and troposphere when monthly-mean zonal-mean ozone is prescribed. We will quantify the magnitude of this difference, examine the cause of the difference, and discuss possibilities to account for zonal variations in ozone.