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Abstract

Besides chlorine, bromine is the second most important halogen when it comes to the destruction of ozone in the stratosphere. Although 150 times more chlorine than bromine is transported into the stratosphere, the higher ozone-depleting efficiency of bromine (by a factor of 45) makes it very important for catalytic cycles. In this study, balloon-borne DOAS (Differential Optical Absorption Spectroscopy) measurements of direct sunlight and limb measurements of scattered skylight, recorded at high latitudes in fall 2009, were used to analyse the bromine chemistry of the stratosphere. These measurements were compared with data from the 1D photochemical model Labmos, initialised with output from the 3D chemical transport model SLIMCAT. This comparison showed that the ratio of the photolysis rate JBrONO2 and the BrONO2 formation rate coefficient k[BrO][NO2] deviates from the JPL-2011 recommendations, leading to a larger BrO/BrONO2 ratio. Using the revised JBrONO2/k[BrO][NO2] ratio, the total stratospheric BrY is likely to be 1.4 ppt lower than the previously estimated (20.3± 2.5) ppt. Furthermore, photochemical corrections of the balloon-borne trace gas concentration profiles were applied in order to compare them with observations from the satellite instrument SCIAMACHY (SCanning Imaging Absorption SpectroMeter for Atmospheric CHartographY) for validation of the satellite retrievals.