Bromine and iodine chemistry in a global chemistry-climate model: Description and evaluation of very short-lived oceanic sources

The global oceanic emissions estimated for the most abundant VSL bromocarbons - 533 Gg yr⁻¹ for CHBr3 and 67.3 Gg yr⁻¹ for CH₂Br₂ -- are within the range of previous estimates. Overall the latitudinal and vertical distributions of modelled bromocarbons are in good agreement with observations. Nevertheless, we identify some issues such as the reduced number of aircraft observations to validate models in the Southern Hemisphere, the overestimation of CH2Br2 in the upper troposphere -- lower stratosphere and the underestimation of CH3I in the same region.

Despite the difficulties involved in the global modelling of the shortest lived iodocarbons (CH₂ICl, CH₂IBr, CH₂I₂), modelled results are in good agreement with published observations in the MBL. Finally, sensitivity simulations show that knowledge of the diurnal emission cycle for these species, in particular for CH₂I₂, is key to assess their global source strength.