, Volume 43, Issue 2, pp 75-106

Ground-Based UV Measurements of BrO and OClO over Ny-Ålesund during Winter 1996 and 1997 and Andøya during Winter 1998/99

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Abstract

Presented here are measurements of BrO and OClO performed by ground-based UV-visible zenith-sky viewing spectrometers developed by the Norwegian Institute for Air Research (NILU). Measurements were taken at Ny-Ålesund, Spitsbergen (79° N, 11° E), in winter and spring1996 and 1997 and at Andøya (69.3° N, 16° E) from summer 1998 until summer 1999. AM and PM differential slant column densities (DSCDs) at 90°SZA of BrO and OClO reached their maxima during polar vortex conditions in the winter months and were anti-correlated to temperature andNO2. Comparison of BrO with a 3-D chemical transport model showed good agreement for seasonal trends and non-vortex conditions. BrO AM/PM ratios were underestimated by the model for vortex conditions, indicating the need for better quantification of BrO source and sink reaction rates. The detection of OClO above 200 K at the 475 K isentropic level indicates the possible activation of chlorine on sulphate particles. Several episodes of boundary layer ozone depletion due to marine-derived BrO were evident in our zenith-skyspectra during April 1997 in Ny-Ålesund.