BrO in the Tropical and Subtropical UTLS: Longitudinal Gradients over the Pacific Ocean

Bromine oxide (BrO) is a halogen radical that catalytically destroys ozone, modifies the oxidative capacity of the atmosphere and oxidizes atmospheric mercury. About 75% of the global tropospheric ozone loss occurs at tropical latitudes, where the ozone radiative forcing is most sensitive to changes in the ozone concentration. Here we report on BrO observations in the tropical and sub-tropical free troposphere and UTLS. Airborne measurements of BrO vertical profiles were performed by the University of Colorado Airborne Multi Axis DOAS (CU AMAX-DOAS) instrument aboard the NSF/NCAR GV aircraft. We compare BrO profiles measured at tropical and subtropical latitudes over the Western Pacific (CONvective TRansport of Active Species in the Tropics, CONTRAST, field campaign) with tropical BrO profiles measured over the Central (Mauna Loa Observatory fly-by) and Eastern Pacific ocean (Tropical Ocean tRoposphere Exchange of Reactive halogen species and Oxygenated VOC, TORERO, experiment). For selected case studies we compare BrO profiles from three independent instruments, i.e., CU AMAX-DOAS, mountain-top MAX-DOAS at Mauna Loa Observatory, and Chemical Ionization Mass Spectrometry and BrO predictions from global models (CAM-Chem, GEOS-Chem and RAQMS).