The importance of stratospheric ozone as a climate active gas is well recognised. Including the interactions between climate and ozone in models is computationally very expensive and ozone is usually prescribed in climate models. This approach underestimates the effects of ozone on the pattern of surface climate variability particularly on the time scale of months to years, and, by construction, ignores transient interactions between ozone and climate on the decadal scale.
The international modeling community is in desperate need of a method for including ozone interactively within climate models but avoiding the huge computational overhead implicit in a coupled chemistry-climate model (CCM), which does not allow performing ensemble runs, which are indispensable for medium range climate predictions.Recent work from AWI has led to the development of an innovative system of coupled differential equations that can simulate the seasonal evolution of polar ozone chemistry. The model, named SWIFT, correctly includes all chemical and physical mechanisms and although SWIFT is extremely rapid and can process hundreds of years per second, it is applicable for a wide range of climate conditions and is not limited to current conditions.
Through this collaborative project we will further develop SWIFT and extend it to the non-polar regions, such that it can be used as an extremely fast module for global stratospheric ozone chemistry in the MiKlip model system. For the development and validation of SWIFT we will imbed the module into EMAC. EMAC is a chemistry-climate model including the ECHAM5 dynamical model and a comprehensive chemistry scheme provided by the MPI for Chemistry. In this project, we will produce EMAC-SWIFT by replacing the full chemistry scheme of EMAC with SWIFT. We will also use a version of EMAC developed by FUB that includes an interactive ocean model, both with full chemistry (EMAC-O) and with the SWIFT chemistry (EMAC-O-SWIFT). Based on this setup we will validate SWIFT and explore the capabilities of such an extended model by comparing results obtained from model integrations using EMAC-SWIFT with those obtained from the EMAC CCM with full chemistry module. After validation in the EMAC environment we will provide the SWIFT module to the “prototype MiKlip system” and assist with its implementation. Further, we will quantify the benefits of including interactive ozone chemistry on decadal prediction by comparing the “prototype MiKlip system” (including SWIFT) with the “MiKlip baseline system” (without interactive ozone chemistry), as well as by analyzing the final “MiKlip synthesis system”.