Scientific objectives

POLSTRACC aims at improving our understanding of the role of the Arctic stratosphere in the atmospheric system in the future. Utilizing the combination of airborne observations, correlative ground- and satellite-based observations and model simulations, the goal of POLSTRACC is to provide more reliable projections of the development of the upper troposphere and lower stratosphere (UTLS) and in particular the ozone layer in the future. POLSTRACC will employ a high-altitude aircraft campaign during the Arctic winter 2015/16 based in Oberpfaffenhofen (Germany) and Kiruna (Sweden) to study the Arctic polar vortex and its vicininty during an entire winter/spring cycle. The key objectives of POLSTRACC are:

• Investigating the structure, dynamics and chemical composition of the UTLS at high latitudes, with a special focus on the Lowermost Stratosphere (LMS). Studies on the outflow of the polar vortex and its influence on the composition of the LMS at high and middle latitudes.
• Improving the understanding of catalytic processes involved in polar ozone depletion, with a focus on chlorine and bromine chemistry in the LMS.
• Improving the knowledge on polar stratospheric cloud (PSC) composition, de-/nitrification by sedimentation of nitric acid-containing particles and the role of gravity waves or orographic waves on PSC occurrence.
• Investigating Arctic cirrus clouds, their influence on the radiative forcing and their potential for denitrification, dehydration and chlorine activation.

The POLSTRACC mission is performed in combination with the BMBF/ROMIC project GW-LCYCLE and the SALSA project, and will involve a modern suite of remote-sensing and in-situ instruments. The POLSTRACC payload covers a variety of trace gases and physical parameters, with contributions from the Karlsruhe Institute of Technology (KIT), Forschungszentrum Jülich (JÜLICH), National Aeronautics and Space Research Centre (DLR), universities and partners. The measurements will be complemented by chemistry transport and climate chemistry modelling studies, allowing to test improved parametrizations of processes involved in chemical ozone depletion, atmospheric dynamics, clouds and the radiation budget of the UTLS.