Widespread persistent near-surface ozone depletion at northern high latitudes in spring

Abstract

Springtime near-surface ozone depletion has been observed at northern high latitudes. Due to limited observations, the spatial and temporal extent of low O3 concentrations near the surface is still unknown. A regional 3-D chemistry and transport model is applied to simulate surface O3 depletion catalyzed by bromine radicals at northern high latitudes in March and April 2000. Satellite observations of BrO column by the ESA Global Ozone Monitoring Experiment (GOME) were processed to specify the BrO concentrations in the lower troposphere. In view of the GOME measurement and model uncertainties, the model results show an adequate agreement with the O3 depletion events observed at two surface sites, Alert, Canada (82.5°N, 62.3°W) and Barrow, Alaska (71.3°N, 156.6°W), and by airborne in situ and DIAL instrument during the TOPSE experiments at northern high latitudes. Low O3 events at Alert appear to be mostly driven by transport of O3-poor air from high BrO regions. Model results indicate that low O3 concentrations (<20 ppbv) near the surface cover ∼60% of the northern high latitudes and that the depleted O3 concentrations (<10 ppbv) cover ∼20% of the region in April. The high BrO events tend to be largescale and persistent (1-2 weeks). We find that they are correlated with low temperature, a condition conducive for heterogeneous reactions on frozen snow or aerosol surfaces. Copyright 2003 by the American Geophysical Union.