The Arctic Springtime Chemistry Climate Investigations – ASCCI aircraft campaign – an overview

The Arctic Springtime Chemistry Climate Investigations (ASCCI) aircraft campaign studied processes in the Arctic upper troposphere and lower stratosphere and their impact on midlatitudes in a changing climate. It was conducted between February and early April 2025 as a coordinated research effort by several German Universities and research institutes.For the ASCCI mission, the German High Altitude and Long-Range Research Aircraft HALO was equipped with a payload consisting of a mixture of in-situ and remote sensing instruments, allowing for a detailed chemical and dynamical characterization of the lowermost polar stratosphere during late winter to early spring 2025. The campaign was especially designed to complement information from the POLSTRACC campaign carried out with HALO during the Arctic winter 2015 to 2016, and the SouthTRAC campaign in 2019 which was aimed at studying the Antarctic lower polar stratosphere during late winter and early spring. Our main aims were to study (i) the inter-annual variability of Arctic lower stratospheric ozone depletion in comparison to POLSTRACC, (ii) high latitude stratosphere-troposphere exchange and the structure of the high latitude tropopause and (iii) the impact of short-lived climate pollutants (ozone, aerosols) and their precursors on the Arctic upper troposphere.The Arctic winter 2024/2025 was characterized by a record-cold mid-winter period, followed by an early stratospheric warming from which the polar vortex only partly recovered. Despite this warming, we were able to observe signs of heterogeneous redistribution of nitrogen species and of chemical ozone depletion. We will present an overview of the flights carried out during ASCCI and first results of the observations. The ASCCI teamUniversity of Mainz, Institute for Physics of the AtmosphereFranziska Weyland, Peter Hoor, Vera Bense, Heiko Bozem, Jonas Blumenroth, Hans-Christoph Lachnitt,Forschungszentrum Jülich (FZJ)Jens-Uwe Grooß, Michaela Hegglin, Marc von Hobe, Tom Neubert, Felix Ploeger, Markus Retzlaff,     Christian Rolf, Georg Schardt, Nicole Spelten, Martin Riese, Sebastian Rhode, Joern Ungermann.University of WuppertalMichael Volk, Valentin Lauther, Johannes Strobel, Ronja von Luijt.Deutsches Zentrum für Luft- und Raumfahrt (DLR)Georgios Dekoutsidis, Andreas Fix, Silke Groß, Konstantin Krüger, Andreas Schäfler, Martin Wirth, Stefan Kaufmann, Mara Montag, Elisabeth Horst, Laura Tomsche, Christiane Voigt, Helmut Ziereis.Karlsruhe Institute of Technology (KIT)Bastian Kirsch, Simone Scheer, Florian Obersteiner, Andreas Zahn, Felix Friedl-Vallon, Michael Höpfner, Wolfgang Woiwode, Erik Kretschmer, Georg, Wetzel, Anne Kleinert, Guid Maucher, Hans Nordmeyer, Christog Piesch, Franziska Trinkl.University of HeidelbergBenjamin Weyland, Karolin Voss, Maximilain Albrecht, Andre Butz, Klaus Pfeilsticker