Year-to-year variations of spring time polar tropospheric BrO as seen by GOME Original Research Article

In this paper we present data on the variation of tropospheric BrO, that is connected with the spring time ozone depletion in polar regions. For this study we use data derived from the Global Ozone Monitoring Experiment (GOME) for the years 1996–2001. We especially focus on the possible detection of trends in the extent of coverage of polar regions by BrO and on the time series of BrO abundances. For this purpose we calculated monthly means during polar spring of the areas that are covered with BrO exceeding certain thresholds. It turns out that in the timeseries of total, i.e. tropospheric and stratospheric, BrO column densities there is, up to now, no clear trend identifiable. In contrast, the analysis of areas covered by high concentrations of tropospheric BrO (columns >5.5 × 1013 molecules/cm2) is considerably expanding (about 10% per year during 1996–2000) in the northern hemisphere in the comparison of monthly means during polar spring, which is possibly due to an anthropogenic effect on the climate system.