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Abstract. Bromine released from the decomposition of short-lived brominated source gases contributes as a sink of ozone in the lower stratosphere.The two major contributors are CH2Br2 and CHBr3.In this study, we investigate the global seasonal distribution of these two substances, based on four High Altitude and Long Range Research Aircraft (HALO) missions, the HIAPER Pole-to-Pole Observations (HIPPO) mission, and the Atmospheric Tomography (ATom) mission.Observations of CH2Br2 in the free and upper troposphere indicate a pronounced seasonality in both hemispheres, with slightly larger mixing ratios in the Northern Hemisphere (NH).Compared to CH2Br2, CHBr3 in these regions shows larger variability and less clear seasonality, presenting larger mixing ratios in winter and autumn in NH midlatitudes to high latitudes.The lowermost stratosphere of SH and NH shows a very similar distribution of CH2Br2 in hemispheric spring with differences well below 0.1 ppt, while the differences in hemispheric autumn are much larger with substantially smaller values in the SH than in the NH.This suggests that transport processes may be different in both hemispheric autumn seasons, which implies that the influx of tropospheric air (“flushing”) into the NH lowermost stratosphere is more efficient than in the SH.The observations of CHBr3 support the suggestion, with a steeper vertical gradient in the upper troposphere and lower stratosphere in SH autumn than in NH autumn.However, the SH database is insufficient to quantify this difference.We further compare the observations to model estimates of TOMCAT (Toulouse Off-line Model of Chemistry And Transport) and CAM-Chem (Community Atmosphere Model with Chemistry, version 4), both using the same emission inventory of Ordóñez et al. (2012).The pronounced tropospheric seasonality of CH2Br2 in the SH is not reproduced by the models,presumably due to erroneous seasonal emissions or atmospheric photochemical decomposition efficiencies.In contrast, model simulations of CHBr3 show a pronounced seasonality in both hemispheres, which is not confirmed by observations.The distributions of both species in the lowermost stratosphere of the Northern and Southern hemispheres are overall well captured by the models with the exception of southern hemispheric autumn,where both models present a bias that maximizes in the lowest 40 K above the tropopause, with considerably lower mixing ratios in the observations.Thus, both models reproduce equivalent flushing in both hemispheres, which is not confirmed by the limited available observations.Our study emphasizes the need for more extensive observations in the SH to fully understand the impact of CH2Br2 and CHBr3 on lowermost-stratospheric ozone loss and to help constrain emissions.

Dichloromethane (CH₂Cl₂) and perchloroethylene (C₂Cl₄) are chlorinated very short lived substances (Cl‐VSLS) with anthropogenic sources. Recent studies highlight the increasing influence of such compounds, particularly CH₂Cl₂, on the stratospheric chlorine budget and therefore on ozone depletion. Here, a multiyear global‐scale synthesis inversion was performed to optimize CH₂Cl₂(2006–2017) and C₂Cl₄(2007–2017) emissions. The approach combines long‐term surface observations from global monitoring networks, output from a three‐dimensional chemical transport model (TOMCAT), and novel bottom‐up information on prior industry emissions. Our posterior results show an increase in global CH₂Cl₂emissions from 637 ± 36 Gg yr⁻¹in 2006 to 1,171 ± 45 Gg yr⁻¹in 2017, with Asian emissions accounting for 68% and 89% of these totals, respectively. In absolute terms, Asian CH₂Cl₂emissions increased annually by 51 Gg yr⁻¹over the study period, while European and North American emissions declined, indicating a continental‐scale shift in emission distribution since the mid‐2000s. For C₂Cl₄, we estimate a decrease in global emissions from 141 ± 14 Gg yr⁻¹in 2007 to 106 ± 12 Gg yr⁻¹in 2017. The time‐varying posterior emissions offer significant improvements over the prior. Utilizing the posterior emissions leads to modeled tropospheric CH₂Cl₂and C₂Cl₄abundances and trends in good agreement to those observed (including independent observations to the inversion). A shorter C₂Cl₄lifetime, from including an uncertain Cl sink, leads to larger global C₂Cl₄emissions by a factor of ~1.5, which in some places improves model‐measurement agreement. The sensitivity of our findings to assumptions in the inversion procedure, including CH₂Cl₂oceanic emissions, is discussed.