Research in a nutshell
The UTLS (upper troposphere/ lower stratosphere) region constitutes the interface of the turbulent and well mixed troposphere and the more stable stratified stratosphere. It is thus affected by frequent and eventually small scale dynamical, chemical and microphysical processes at the tropopause as well as the stratospheric circulation (Brewer-Dobson circulation). Its composition reflects these different processes and and time scales of transport. Importantly the composition feeds back on the thermodynamical structure introducing complex coupling effects on all scales. In combination these lead to large uncertainties when estimating future climate and surface temperatures, since their effects and interaction are partly unknown or quantified.

Airborne tracer measurements allow to identify transport pathways and source regions. They also allow to quantify air mass budgets for the UTLS or to deduce time scales for transport.