Gome measurements of stratospheric and tropospheric BrO Original Research Article

Measurements from the Global Ozone Monitoring Experiment (GOME) have been analysed for BrO absorption using the Differential Optical Absorption (DOAS) method. By introducing a correction for a small angle dependency of the diffusor used for the direct sun measurements in the GOME instrument, the overall consistency of the BrO data set could be improved significantly. Evidence is found for large tropospheric contributions to the BrO columns measured by GOME, both from BrO in the polar boundary layer in spring and a global BrO background, probably located in the free troposphere and present throughout the year. The latter has been further investigated by comparing BrO and O4 columns above the remote Pacific, resulting in an estimate of 0.5 – 2ppt of uniformly mixed BrO in the troposphere, in agreement with previous studies.