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. We infer surface fluxes of bromoform ( CHBr3 ) anddibromoform ( CH2Br2 ) from aircraft observations over the westernPacific using a tagged version of the GEOS-Chem global 3-D atmosphericchemistry model and a maximum a posteriori inverse model. Using GEOS-Chem (GC) asan intermediary, we find that the distribution of a priori oceanemissions of these gases are reasonably consistent with observed atmosphericmole fractions of CHBr3 ( r=0.62 ) and CH2Br2 ( r=0.38 ). These a priori emissions result in a positive model biasin CHBr3 peaking in the marine boundary layer, but reproduceobserved values of CH2Br2 with no significant bias by virtue ofits longer atmospheric lifetime. Using GEOS-Chem, we find that observedvariations in atmospheric CHBr3 are determined equally by sourcesover the western Pacific and those outside the study region, but observedvariations in CH2Br2 are determined mainly by sources outsidethe western Pacific. Numerical closed-loop experiments show that the spatialand temporal distribution of boundary layer aircraft data have the potentialto substantially improve current knowledge of these fluxes, with improvementsrelated to data density. Using the aircraft data, we estimate aggregatedregional fluxes of 3.6 ± 0.3 × 10 8 and 0.7 ± 0.1 × 10 8  g month −1 for CHBr3 and CH2Br2 over130–155 ∘ E and 0–12 ∘  N, respectively, which representreductions of 20 %–40 % of the prior inventories by Ordonezet al. (2012) and substantial spatial deviations from different apriori inventories. We find no evidence to support a robust linearrelationship between CHBr3 and CH2Br2 oceanicemissions, as used by previous studies. We find that over regions with denseobservation coverage, our choice of a priori inventory does notsignificantly impact our reported a posteriori flux estimates.

Surface fluxes of bromoform and dibromomethane over the tropical western Pacific inferred from airborne in situ measurements