Abstract. Oceanic emissions of very short lived halocarbons (VSLH), such as CHBr3, are important for the halogen budget of the atmosphere. It is an open question how localized elevated emissions in coastal and upwelling regions and low background emissions, typically found over the open ocean, impact the atmospheric VSLH distribution. In this study, we use the Lagrangian dispersion model FLEXPART to simulate atmospheric CHBr3 resulting from uniform background emissions, on the one hand, and from elevated emissions observed during three tropical cruise campaigns, on the other hand. The simulations demonstrate that the atmospheric CHBr3 distributions due to uniform background emissions are highly variable with accumulations taking place in regions of low wind speed. This relation holds on regional and global scales demonstrating the importance of the atmospheric transport for the distribution of short-lived trace gases with lifetimes in the range of days to weeks. The impact of localized elevated emissions, measured during three research cruises, on the atmospheric CHBr3 distribution varies significantly from campaign to campaign. The estimated impact depends on the strength of the emissions and the meteorological conditions. In the open waters of the western Pacific and Indian Ocean, localized elevated emissions only slightly increases the background concentrations of atmospheric CHBr3, even when 1° wide source regions along the cruise tracks are assumed. Near the coast, elevated emissions, including hotspots up to 100 times larger than the uniform background emissions, can be strong enough to be distinguished from the atmospheric background. However, it is not necessarily the highest hotspot emission that produces the largest enhancement, since the tug-of-war between fast advective transport and local accumulation at the time of emission is also important. Our analyses contribute to a better understanding and prediction of the timing and regional characteristics of tropospheric CHBr3 distribution. Significantly, our results demonstrate that transport variations of the atmosphere itself are sufficient to produce highly variable VSLH distributions, and elevated VSLH in the atmosphere do not always reflect a strong localized source. Localized elevated emissions can be obliterated by the highly variable atmospheric background, even if they are orders of magnitude larger than the average open ocean emissions.;
