The composition of the upper troposphere and lower stratosphere (UTLS) plays a key role in the climate system, influencing radiation, atmospheric chemistry, and dynamics. Recent advances in observations and modeling are providing new insights into the processes governing the variability and long-term evolution of this region. The session focuses on topics related to UTLS dynamics, transport, and chemical processes that determine atmospheric composition and its implications for radiation and climate across a range of spatial and temporal scales.
We encourage contributions based on in situ and remote-sensing observations from recent and ongoing field campaigns as well as on models of varying complexity, ranging from comprehensive chemistry–climate models to idealized and conceptual approaches. Especially, we welcome studies connecting observational datasets with process-level understanding or model evaluation.