TY - JOUR A1 - Ziereis, Helmut A1 - Hoor, Peter A1 - Grooß, Jens-Uwe A1 - Zahn, Andreas A1 - Stratmann, Greta Annabell A1 - Stock, Paul A1 - Lichtenstern, Michael A1 - Krause, Jens A1 - Bense, Vera A1 - Afchine, Armin A1 - Rolf, Christian A1 - Woiwode, Wolfgang A1 - Braun, Marleen A1 - Ungermann, Jörn A1 - Marsing, Andreas A1 - Voigt, Christiane A1 - Engel, Andreas A1 - Sinnhuber, Björn-Martin A1 - Oelhaf, Hermann T1 - Redistribution of total reactive nitrogen in the lowermost Arctic stratosphere during the cold winter 2015/2016 T2 - Atmospheric chemistry and physics N2 - During winter 2015/2016, the Arctic stratosphere was characterized by extraordinarily low temperatures in connection with a very strong polar vortex and with the occurrence of extensive polar stratospheric clouds. From mid-December 2015 until mid-March 2016, the German research aircraft HALO (High Altitude and Long-Range Research Aircraft) was deployed to probe the lowermost stratosphere in the Arctic region within the POLSTRACC (Polar Stratosphere in a Changing Climate) mission. More than 20 flights have been conducted out of Kiruna, Sweden, and Oberpfaffenhofen, Germany, covering the whole winter period. Besides total reactive nitrogen (NOy), observations of nitrous oxide, nitric acid, ozone, and water were used for this study. Total reactive nitrogen and its partitioning between the gas and particle phases are key parameters for understanding processes controlling the ozone budget in the polar winter stratosphere. The vertical redistribution of total reactive nitrogen was evaluated by using tracer–tracer correlations (NOy–N2O and NOy–O3). The trace gases are well correlated as long as the NOy distribution is controlled by its gas-phase production from N2O. Deviations of the observed NOy from this correlation indicate the influence of heterogeneous processes. In early winter no such deviations have been observed. In January, however, air masses with extensive nitrification were encountered at altitudes between 12 and 15 km. The excess NOy amounted to about 6 ppb. During several flights, along with gas-phase nitrification, indications for extensive occurrence of nitric acid containing particles at flight altitude were found. These observations support the assumption of sedimentation and subsequent evaporation of nitric acid-containing particles, leading to redistribution of total reactive nitrogen at lower altitudes. Remnants of nitrified air masses have been observed until mid-March. Between the end of February and mid-March, denitrified air masses have also been observed in connection with high potential temperatures. This indicates the downward transport of air masses that have been denitrified during the earlier winter phase. Using tracer–tracer correlations, missing total reactive nitrogen was estimated to amount to 6 ppb. Further, indications of transport and mixing of these processed air masses outside the vortex have been found, contributing to the chemical budget of the winter lowermost stratosphere. Observations within POLSTRACC, at the bottom of the vortex, reflect heterogeneous processes from the overlying Arctic winter stratosphere. The comparison of the observations with CLaMS model simulations confirm and complete the picture arising from the present measurements. The simulations confirm that the ensemble of all observations is representative of the vortex-wide vertical NOy redistribution. Y1 - 2022 UR - http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/75174 UR - https://nbn-resolving.org/urn:nbn:de:hebis:30:3-751748 SN - 1680-7324 N1 - Funding: German Research Foundation (DFG) ; EN 367/13-1, EN 367 N1 - Funding: German Research Foundation (DFG) ; 14-1, HO 4225/7-1 N1 - Funding: German Research Foundation (DFG) ; HO4225-6/1 N1 - Funding: DFG SPP HALO 1294 ; VO1504/7-1 N1 - Funding: DFG SFB/TR 301 TPChange N1 - Funding: Helmholtz Association ; HGF-W2/W3 excellence programme N1 - Funding: Deutsche Forschungsgemeinschaft ; 428312742 VL - 22 IS - 5 SP - 3631 EP - 3654 PB - EGU CY - Katlenburg-Lindau ER -