10.6 Predicted changes in stratospheric ozone fluxes into the troposphere due to a changing climate

Thursday, 11 June 2009: 12:00 PM
Michaela I. Hegglin, University of Toronto, Toronto, ON, Canada; and T. G. Shepherd

Chemistry-Climate models (CCMs) consistently predict an increase in the strength of the Brewer-Dobson circulation due to a changing climate. It has also been shown that this increase strongly affects the distribution of stratospheric ozone, especially in the mid-latitude lower stratosphere. The associated changes are likely to affect the amount of ozone transported from the stratosphere into the troposphere. While the contribution of stratospheric ozone to the total tropospheric ozone budget is rather small, it strongly affects ozone concentrations in the upper troposphere, where ozone has a longer lifetime of about one month and its most important impact on the radiative forcing in determining surface temperatures. We here use the CCMs taking part in CCMVal (Chemistry-Climate Model Validation) – a project within SPARC (Stratospheric Processes and their Role in Climate) – in order to quantify the changes in the net stratosphere-to-troposphere ozone flux between 1960-2100. Along with the results and their implications for the tropospheric ozone budgets, we discuss the role of ozone depletion and recovery in modulating the stratospheric ozone fluxes, and the models' capabilities to represent dynamical and chemical processes in the lower stratosphere in order to gain confidence in their predictions.
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