A three-dimensional model study on the production of BrO and Arctic boundary layer ozone depletion

Abstract

A three-dimensional model (GEM-AQ/Arctic) was developed to study the chemistry and processes involved in the ozone depletion events (ODEs) in the Arctic boundary layer (ABL), which included a comprehensive mechanism of multiphase halogen chemistry in the ABL and our current understanding of the ODEs. Assuming that frost flower-derived aerosols were the primary halogen source, the areas potentially covered by frost flowers were determined. The carbonate precipitation scheme was taken into account for triggering the bromine explosions in the model. A comparison of the simulations with GOME satellite measurements in springs of 2000 and 2001 showed that the spatial structure and temporal evolution of tropospheric BrO clouds were well predicted by the model. The majority of the springtime ODEs observed at three arctic stations was reasonably reproduced. An analysis on the model results indicated that most periods of simulated ozone depletion (03 < 1 nmol mol-1) occurred in a layer 300 to 400 m deep at the Arctic sites. It is found that the halogen chemistry in the marine boundary layer (MBL) contributed substantially to the spring time ODEs, but atmospheric temperature and circulations as well as the transported air pollution in the ABL were also responsible for the ODEs. For springs of 2000 and 2001, two source regions with low surface O3 levels were identified: the Siberian/Beaufort Arctic and the Canadian Arctic, broadly corresponding to areas of enhanced BrO levels and accompanied by the Arctic anticyclones. Dominant trans-Arctic transport pathways were also investigated for the ODEs at Alert, Barrow and Zeppelinfjellet. Copyright 2008 by the American Geophysical Union.