This session focuses on the variability of the tropospheric and stratospheric chemical composition on seasonal to decadal timescales. Emphasis is put on the scientific value of long-term measurement time series and supporting model simulations. Both topics contribute to improved understanding of the mechanisms which control interannual to decadal variability of atmospheric constituents like greenhouse gases (e.g. CO2, CH4, N2O and CFCs, as well as indirect gases such as H2) and air pollutants (e.g. CO, O3, NOx, VOCs). Documentation of the changing atmospheric composition in the context of global change is important.
Researchers are invited to present novel scientific results from mid- and long-term observational time series from various ground based measurements networks such as Global Atmosphere Watch (GAW), European Monitoring and Evaluation Programme (EMEP), Network for the Detection of Atmospheric Composition Change (NDACC), Southern Hemisphere Additional Ozonesondes (SHADOZ), Advanced Global Atmospheric Gases Experiment (AGAGE), National Oceanic and Atmospheric Administration (NOAA), regular airborne (e.g. MOZAIC, CARIBIC) and other campaigns as well as satellite data and model simulations. Data relevant to tropospheric and stratospheric composition, in particular to ozone depletion and climate change as well as firn data on past atmospheric composition are welcome. We welcome contributions from multi-year modeling studies and inter-comparison exercises which address tropospheric or stratospheric composition changes, carried out in the framework of international projects (e.g. GEOMON, MACC) and initiatives (IGAC’s Atmospheric Chemistry and Climate, TFMM, TFHAT and others). Within the session, there will be a special sub-session for the anniversary of the NDACC program.