Stratospheric ClO Across the Edge of the Arctic Polar Vortex: Measurements of the Airborne Submillimeter SIS Radiometer Compared to 3-D Model Calculations

Abstract

The Airborne Submillimeter SIS Radiometer (ASUR), operated on-board the German research aircraft FALCON, measures thermal emission lines of stratospheric trace gases at submillimeter wavelength. Measurement campaigns with respect to ozone depletion in the Arctic winter stratosphere were carried out in yearly intervals from 1992–97 to investigate the distributions of the radical chlorine monoxide (CIO), the reservoir species hydrochloric acid (HCI), the chemically inert tracer nitrous oxide (N2O), and ozone (O3). The high sensitivity of the receiver allowed to take spatially well resolved measurements inside, at the edge, and outside of the Arctic polar vortex. This paper focuses on the results obtained for C10 from two flights across the vortex edge during February and March 1996, when temperatures in the lower stratosphere of the Arctic vortex were persistently low leading to a strong chlorine activation due to heterogeneous reactions on polar stratospheric cloud particles [1]. For this situation, when strong gradients of the C1O mixing ratio at the vortex edge were observed, the measured profiles of C1O are compared to results of the 3-dimensional chemical transport model SLIMCAT of the University of Cambridge [2].