Preliminary characterization of the stratospheric circulation using long-lived tracers with the WACCM chemistry-climate model and observations

The changes in stratospheric circulation are one of the major sources of uncertainty in climate projection, therefore they are a major area of research.
The current work is part of the ACCROSS (Atmospheric Composition and Circulation investigated with meteorological Reanalyses, Observational datasets and models for the Study of the Stratosphere and its changes) project, which intends to improve our understanding of the circulation changes in the past years through an extensive use of observations and model simulations of selected long-lived tracers.
Here we compare simulations of a state-of-the-art Chemistry Climate Model with satellite observations of HF and N2O from February 2004 to February 2013. To accomplish this task major modifications to the model chemistry scheme have been made.
This early comparison shows poor agreement in the HF distribution in the middle stratosphere for all latitudes, while in the low stratosphere the agreement is better, especially in the tropics. Since good agreement is found in the N2O distribution, the residual circulation is well represented, e.g. the model reproduces well the position of the transport barriers in the SH, this suggests that the disagreement in the HF distributions is due to an incomplete chemical scheme. A comparison with chemistry-transport models using the same chemistry scheme and boundary conditions is needed to evaluate this point.