Spatial and temporal distribution of enhanced boundary layer BrO concentrations measured by the GOME instrument aboard ERS-2

The temporal and spatial distribution of enhanced boundary layer BrO concen trations in both hemispheres during 1997 is presented using observations of the Global Ozone Monitoring Experiment (GOME) on board the European resear ch satellite ERS-2. BrO concentrations (up to 50 ppt) are the major cause f or catalytic boundary layer ozone destruction typically observed during pol ar spring in both hemispheres. While autocatalytic mechanisms are most prob ably responsible for the release of the observed high concentrations of rea ctive bromine compounds, uncertainties still remain with respect to the pri mary release, mechanisms arid whether the autocatalytic reactions are takin g place on sea-salt aerosol or the surface of sea ice. We find that enhance d boundary layer BrO concentrations correlate very well with ozone depletio n events. Enhanced BrO concentrations are always found over or near to area s of frozen salt water (above sea ice or also above the frozen surface of t he Caspian Sea) consistent with the assumption that such conditions are a p rerequisite for the autocatalytic release of high BrO concentrations to the troposphere.