| This study is based on in situ measurements made on the NASA DC-8 during the SAGE III Ozone Loss and Validation Experiment/Third European Stratospheric Experiment on Ozone (SOLVE/THESEO) campaign which was conducted in the 1999-2000 Arctic winter (November, 1999 to April, 2000). The DC-8's extensive coverage of the arctic winter tropopause region afforded the opportunity to probe more deeply into the unique chemistry of the upper troposphere/lower stratosphere (UTLS). Central to this analysis are the measurements of OH, HO2⊂ (collectively called HOx⊂), and halogen oxides that play a crucial role in the chemistry of this region. We discuss the modified configuration of the Penn State Airborne Tropospheric Hydrogen Oxides Sensor (ATHOS) in order to accommodate the University of Colorado ClO/BrO instrument, the salient points of the measurement profiles that were obtained by this unique instrument, the shifts of these profiles in the presence of cirrus clouds that may indicate heterogeneous processing/activation of halogen reservoir species, and the projected impact of the abundance of these species on the local chemical ozone budget in the region. |
