Very short-lived halogens amplify ozone depletion trends in the tropical lower stratosphere

Abstract

In contrast to the general stratospheric ozone recovery following international agreements, recent observations show an ongoing net ozone depletion in the tropical lower stratosphere (LS). This depletion is thought to be driven by dynamical transport accelerated by global warming, while chemical processes have been considered to be unimportant. Here we use a chemistry–climate model to demonstrate that halogenated ozone-depleting very short-lived substances (VSLS) chemistry may account for around a quarter of the observed tropical LS negative ozone trend in 1998–2018. VSLS sources include both natural and anthropogenic emissions. Future projections show the persistence of the currently unaccounted for contribution of VSLS to ozone loss throughout the twenty-first century in the tropical LS, the only region of the global stratosphere not projecting an ozone recovery by 2100. Our results show the need for mitigation strategies of anthropogenic VSLS emissions to preserve the present and future ozone layer in low latitudes.

Evaluating the Model Representation of Asian Summer Monsoon Upper Troposphere and Lower Stratosphere Transport and Composition Using Airborne In Situ Observations

“…Ozone mixing ratios observed by FOZAN-II are further supported by ozonesonde observations over Nepal during StratoClim which show ∼30-50 ppbv ozone throughout the free troposphere (Brunamonti et al, 2018), as well as by ozonesonde observations from the neighboring regions (Bian et al, 2012;Ma et al, 2022). We have performed several sensitivity experiments to investigate the cause of the model ozone high bias, including testing for sensitivity to chemistry of very short lived (VSL) species using the model configuration of Villamayor et al (2023), and to adjusting the model's lightning parameterization to generate less NOx (an ozone precursor). The results of these sensitivity runs on model ozone mixing ratios are shown in Figure S3 in Supporting Information S1.…”

“…We have performed several sensitivity experiments to investigate the cause of the model ozone high bias, including testing for sensitivity to chemistry of very short lived (VSL) species using the model configuration of Villamayor et al. (2023), and to adjusting the model's lightning parameterization to generate less NOx (an ozone precursor). The results of these sensitivity runs on model ozone mixing ratios are shown in Figure S3 in Supporting Information .…”

Natural marine bromoform emissions in the fully coupled ocean-atmosphere-model NorESM2

“…In the tropics, VSLSs are rapidly lifted to the stratosphere by tropical deep convection (Sala et al, 2014;Navarro et al, 2015;Fuhlbrügge et al, 2016), where they contribute up to ~25% to stratospheric bromine (Dorf et al, 2006 and following work). Bromine is ~60 times more efficient in depleting lower stratospheric ozone than chlorine and significantly contributes to ozone depletion in the lower stratosphere (Daniel et al, 1999;Sinnhuber et al, 2009;Montzka et al, 2011;Villamayor et al, 2023) with potential impacts on the radiation budget of the atmosphere from -0.02 W m -2 to -0.13 W m -2 (Hossaini et al, 2015;Saiz-Lopez et al, 2023).…”

Eine Alkin‐verbrückte kovalent organische Gerüstverbindung mit interaktiven Bindungstaschen für das Einfangen von Brom

“…[3] Dies steht vor allem im Zusammenhang mit der Freisetzung von Schadstoffen aus verschiedenen industriellen Quellen, die erhebliche Mengen an Brom und Iod enthalten (Halone). [4] Brom kann in der Troposphäre photokatalytisch gespalten werden und bildet freie BrO-Radikale, die bereits bei ppb-Konzentrationen das gesamte lokale Ozon abbauen können. [5] Darüber hinaus ist Brom im Gegensatz zu Iod toxisch, welches in Spuren für die menschliche Gesundheit nützlich ist und für das ordnungsgemäße Funktionieren der Schilddrüse benötigt wird.…”