Global observations of tropospheric BrO columns using GOME-2 satellite data
1Belgian Institute for Space Aeronomy (IASB-BIRA), Brussels, Belgium
2National Centre for Atmospheric Science (NCAS), Cambridge, CB2 1EW, UK
3Centre for Atmospheric Science, Department of Chemistry, University of Cambridge, Cambridge CB2 1EW, UK
4Institute of Environmental Physics, University of Bremen, Bremen, Germany
5National Institute of Water and Atmospheric Research (NIWA), Omakau, Central Otago, New Zealand
Abstract. Measurements from the GOME-2 satellite instrument have been analyzed for tropospheric BrO using a residual technique that combines measured BrO columns and estimates of the stratospheric BrO content from a climatological approach driven by O3 and NO2 observations. Comparisons between the GOME-2 results and BrO vertical columns derived from correlative ground-based and SCIAMACHY nadir observations, present a good level of consistency. We show that the adopted technique enables separation of stratospheric and tropospheric fractions of the measured total BrO columns and allows quantitative study of the BrO plumes in polar regions. While some satellite observed plumes of enhanced BrO can be explained by stratospheric descending air, we show that most BrO hotspots are of tropospheric origin, although they are often associated to regions with low tropopause heights as well. Elaborating on simulations using the p-TOMCAT tropospheric chemical transport model, this result is found to be consistent with the mechanism of bromine release through sea salt aerosols production during blowing snow events. No definitive conclusion can be drawn however on the importance of blowing snow sources in comparison to other bromine release mechanisms. Outside polar regions, evidence is provided for a global tropospheric BrO background with column of 1–3 × 1013 molec cm−2, consistent with previous estimates.