Climate-relevant processes in the upper troposphere/lower stratosphere (UTLS)
Prof. Dr. Martin Riese (Institut für Energie und Klimaforschung, Forschungszentrum Jülich GmbH)

Changes and variability of upper troposphere / lower stratosphere (UTLS) composition are major drivers of surface climate change (e.g. Solomon et al., 2010). Even small changes of spatially highly variable concentrations of greenhouse gases such as water vapor (H2O) and ozone (O3), aerosols or cirrus clouds have significant effects on the atmospheric radiation balance. A prominent example is the contribution of lower stratospheric water vapour variations to decadal changes in the rate of global warming. Improved prediction capabilities of chemistry-climate models (CCM) therefore rely on a realistic representation of physical and chemical processes affecting UTLS composition. The talk will give an overview on important UTLS processes such as stratosphere-troposphere exchange and changes in the wave-driven Brewer-Dobson circulation. Current uncertainties are discussed as well as the need for temperature and trace gas observations with improved three-dimensional spatial resolution.