New retrieval of BrO from SCIAMACHY limb: an estimate of the stratospheric bromine loading during April 2008

Abstract

We present a new retrieval of stratospheric BrO (bromine monoxide) from channel 2 SCIAMACHY (SCanning Imaging Absorption spectrometer for Atmospheric CHartographY) limb observations. Retrievals are shown to agree with independent balloon observations to within one standard deviation of the retrieval noise. We retrieve BrO profiles for all of April 2008, and apply simulated [BrO]/[Bry] (bromine monoxide : stratospheric inorganic bromine) ratios to estimate the stratospheric Bry loading. We find 23.5 ± 6 ppt Br, suggesting 7 ppt Br from short-lived bromocarbons to be at the high end of the current best estimate (3–8 ppt). The 6 ppt Br uncertainty estimate is dominated by the 21% uncertainty in the simulated [BrO] / [Bry] ratio due to propagation of errors from the underlying chemical kinetics.