Remote Sensing of Bromine Monoxide in Relation to Boundary-layer Halogen Chemistry

Remote sensing of bromine monoxide (BrO) from the Ozone Monitoring Instrument (OMI) and other satellite instruments opens the possibility to extend our understanding of atmospheric halogen chemistry from local-scale studies to global scales. In the Arctic springtime boundary layer, these bromine monoxide radicals and bromine atoms are known to destroy ozone [1] and oxidize mercury [2], leading to its deposition and possible incorporation into the food chain. In the stratosphere, these same reactive bromine species deplete ozone, affecting the ground-level UV dose. The satellite BrO vertical column density (VCD) data contain contributions from both boundary layer BrO and stratospheric BrO. Therefore, it is critical to separate the stratospheric BrO from the boundary layer BrO to determine in which atmospheric layer the satellite-detected BrO is causing impacts. In this presentation, we describe ground-based remote sensing of boundary layer BrO and combine these observations with satellite observations and models to develop and test methods for partitioning satellite-detected total column BrO measurements. Reactive halogens (e.g. BrO) are produced in the boundary layer through gas-surface reactions on the surface of ice that contains sea salts [1]. While the exact mechanism of what types of salt-containing surfaces are most responsible for reactive halogen production is a matter of debate, the process is clearly related to the salinity of ice surfaces. The salinity of sea ice surfaces during the Arctic springtime is increasing due to dramatic reductions in perennial (multi-year) sea ice in the summer, which increases the coverage of the more saline first-year sea ice. Therefore, it is critical to measure the boundary layer component of BrO so as to be able to relate its abundance to sea ice properties. With a firm understanding of the relationship between halogen activation and sea ice properties, it should be possible to make informed predictions regarding the impacts of summer sea ice reductions on boundary layer ozone depletion and