SPARC Observed Composition Trends and Variability in the UT/LS (OCTAV-UTLS) is an international activity that focusses on improving the quantitative understanding of the UTLS’s role in climate and the impacts of stratosphere-troposphere exchange (STE) processes on air quality.
One key aspect of this activity will be to develop and apply common metrics to compare UTLS data using a variety of geophysically-based coordinate systems (e.g., tropopause, equivalent latitude, jet-focused) using meteorological information from reanalysis datasets.

Contribution of IMK-ASF: provide observational data of the temperature and chemical composition of the UTLS region from MIPAS/Envisat and contribute to the coordinate-system related studies; G.Stiller is member of the scientific steering committee.