Latitudinal distribution of atmospheric methyl bromide: Measurements and modeling

The global distribution of atmospheric methyl bromide (CH3Br) obtained from extensive new measurements of atmospheric CH3Br from latitude 82.5 degrees N to 69.1 degrees S, showed a small decrease from mid- to high-latitudes, a gradient between the northern and southern hemispheres with a ratio of 1. 2 to 1.3, and occasional high concentrations in the tropics. The observed d ata and modeled distributions of industrial CH3Br were used to apportion CH 3Br between natural and industrial components for both hemisphere. We obtai ned an estimated man-made contribution of 4.3 pptv and 2.3 pptv in the nort hern and southern hemispheres, respectively and a natural (non-industrial) background concentration in both hemispheres of 6 pptv with a slight increa se in the tropics.