Retrieval and Observations of Atmospheric BrO from SCIAMACHY nadir Measurements

Abstract

Measurements from the space-borne instrument SCIAMACHY launched in March 2002 onboard the ENVISAT platform, have been analysed for BrO absorption using the Differential Optical Absorption Spectroscopy (DOAS) method. BrO is an important atmospheric trace gas mainly responsible for the depletion of ozone in the polar boundary layer, the free troposphere and the stratosphere. Since 1995, global observations of BrO have been successfully demonstrated by the GOME instrument in several publications. This work reports the retrieval of BrO columns from the channel 2 UV/Visible spectral range of the SCIAMACHY nadir geometry. Although data analysis of GOME and SCIAMACHY BrO is very similar, a UV-shifted spectral range was employed to minimize the impact of residual structures from the polarisation sensitivity of the instrument. From this analysis, excellent agreement was obtained between the GOME and SCIAMACHY BrO columns. The impact of the improved spatial resolution of SCIAMACHY has also been utilised to explore the possibility for a volcanic source of BrO during major eruptions. In the polar regions over sea ice, frost flowers have been implicated as a major source of bromine to the atmosphere and BrO columns obtained from GOME and SCIAMACHY measurements correlates with areas potentially covered with frost flowers.