Airborne in situ tracer observations in the 2019 Springtime Antarctic UTLS during the HALO SouthTRAC campaign

During the recent SouthTRAC (Transport and composition of the Southern Hemisphere UTLS) campaign the German High Altitude and LOng range research aircraft (HALO) intensively probed the bottom of the Antarctic vortex and the adjacent mid to high latitude upper troposphere / lower stratosphere (UTLS) throughout late winter and spring 2019.  A main goal of this mission was to study dynamics, transport and composition of this region, and particularly to assess the impact of the Antarctic vortex on the southern hemisphere UTLS.  The Antarctic winter 2019 was extraordinary with respect to dynamics, with a sudden stratospheric warming (only the second one ever observed) leading to a less stable and unusually warm polar vortex. The campaign consisted of two phases based in Rio Grande, Argentina (54°S) and comprised a total of 27 science flights including transfer flights to/from Argentina and 13 local flights from Rio Grande in September/early October and in November 2019.  A number of these flights penetrated into the lower Antarctic vortex, others crossed streamers or thin filaments shed from the vortex by frequent Rossby wave breaking events.

We present observations obtained on board of HALO by the University of Wuppertal's High Altitude Gas Analyzer –V (HAGAR-V), a 5-channel in-situ tracer instrument recently developed for HALO to study the chemical composition, dynamics, and transport in the UTLS.  HAGAR-V combines i) a fast CO₂ measurement by NDIR analyzer (every 3 s), ii) a 2-channel GC/ECD-system measuring the long-lived tracers CFC-12, SF₆ (every 40 s), CFC-11, CFC-113 and Halon-1211 (every 80s), and iii) a 2-channel GC/MS system measuring a large suite of further long-lived (e.g. HFCs) and short-lived halogenated tracers, including further chlorine source gases (e.g. CCl₄, CH₂Cl₂, CHCl₃, C₂Cl₄, HCFCs) every 2-4 minutes.  We will discuss the unusually active dynamics and associated tracer transport in the vicinity of the 2019 Antarctic vortex reflected by these measurements, and show the temporal development of vertical distributions and tracer correlations throughout the spring.  We will also compare the tracer distributions during SouthTRAC with those observed from the M55 Geophysica aircraft during the 1999 Antarctic campaign APE-GAIA.