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A Transported Bromine Explosion Event in the Canadian High Arctic

Ozone depletion events in the polar troposphere have been linked to extremely high concentrations of bromine, known as bromine explosion events. On April 4-5, 2011, we observed such an event in the Canadian High Arctic at the Polar Environment Atmospheric Research Laboratory (PEARL, 86.4°W, 80.1°N), with measurements made by a UV-visible spectrometer showing that the surface volume mixing ratio of BrO increased from ~1 to ~20 pptv. Ozone, measured by ozonesondes, was depleted to ~1 ppbv from the surface to 720 m during this event. Zenith Scattered Light Differential Optical Absorption Spectroscopy (ZSL-DOAS) and Multi-Axis DOAS (MAX-DOAS) data have been used to retrieve stratospheric and tropospheric BrO profiles and partial columns. GOME-2 tropospheric columns of BrO have been used to complement the ground-based measurements.

The HYSPLIT back-trajectory model and GOME-2 data confirmed that this event originated over the Beaufort Sea on March 31, 2011. The interim reanalysis meteorological data from the European Centre for Medium-Range Weather Forecasts (ECMWF), indicates that the 10-m wind increased from 5 to 24 m/s and the boundary layer height surged from 180 to 610 m over Beaufort Sea during the bromine explosion event, suggesting that it was generated from unstable boundary layer meteorological conditions. Further evidences show this long distance (over ~1,800 km) transport event lasted for more than four days, which indicates a strong recycling of BrO within the bromine cloud. The observed bromine explosion event was captured by the UMUKCA chemistry-climate model, which calculated a surface bromine surge to ~10 pptv and surface ozone depletion to ~1 ppbv at PEARL. Comparisons between the measurements and model show that the bromine depletion factor used in the blowing snow bromine release mechanism requires further investigation.