The Wave-driven ISentropic Exchange (WISE) mission is a collaborative research project to investigate transport and mixing processes in the upper troposphere and the lower stratosphere (UTLS) over the Atlantic. Headed by Forschungszentrum Jülich GmbH and the Johannes Gutenberg University of Mainz, 14 measurement flights were conducted with the high-altitude research aircraft HALO in September and October 2017 from Shannon, Ireland. Further partners providing instrumentation were the Karlsruhe Institute for Technology (KIT), the German Aerospace Center (DLR), the universities of Heidelberg, Frankfurt am Main, and Wuppertal, and the German National Metrology Institute. The scientific flights were supported by a team of about 90 persons.

The main objective of this project is to study the relation between chemical composition and the dynamical structure of the UTLS with a focus on the following topics: (i) interrelation of the tropopause inversion layer (TIL) and trace gas distribution, (ii) role of planetary wave breaking for water vapor transport into the extratropical lower stratosphere, (iii) role of halogenated substances for ozone and radiative forcing in the UTLS region, and (iv) occurrence and effects of sub-visual cirrus (SVC) in the lowermost stratosphere.

The special issue mainly includes papers from the airborne measurement campaign itself but is also open to other studies close to the topic. This includes both advanced scientific analyses of observational and measured data during the campaign as well as related climatological studies, but also manuscripts based on instrumental developments.