Bridging the Gap: Combining Long-Path DOAS and Satellite Observations to Understand Arctic Bromine Chemistry

Halogen chemistry is a central element of tropospheric ozone depletion events (ODEs) during polar spring. Key processes such as sources of reactive halogen species, their transport, and interhalogen interactions as well as the influence of anthropogenic pollution and climate change, however, remain in the focus of Arctic research.

We deployed a long-path DOAS (Differential Optical Absorption Spectroscopy) instrument in Utqiagvik (formerly Barrow), Alaska, in December 2023, and observed enhanced bromine monoxide (BrO) coinciding with reduced ozone concentrations between March and May in 2024 and 2025. By linking these ground-based measurements with satellite observations from TROPOMI and GOME-2B, we aim to improve our understanding of local, regional, and large-scale processes. The results of this comparison highlight the importance of considering the different measurement geometries to capture both near-surface and elevated BrO layers. The findings further suggest that the long-path DOAS measurements are particularly sensitive to bromine activation at an early stage. Therefore, continued ground-based observations are necessary to better characterise near-surface BrO abundances, complementing advances in global satellite monitoring.