000906264 001__ 906264 000906264 005__ 20240712100829.0 000906264 0247_ $$2doi$$a10.5194/acp-22-2049-2022 000906264 0247_ $$2ISSN$$a1680-7316 000906264 0247_ $$2ISSN$$a1680-7324 000906264 0247_ $$2Handle$$a2128/30704 000906264 0247_ $$2altmetric$$aaltmetric:123028921 000906264 0247_ $$2WOS$$aWOS:000759289700001 000906264 037__ $$aFZJ-2022-01330 000906264 082__ $$a550 000906264 1001_ $$0P:(DE-HGF)0$$aLauther, Valentin$$b0$$eCorresponding author 000906264 245__ $$aIn situ observations of CH2Cl2 and CHCl3 show efficient transport pathways for very short-lived species into the lower stratosphere via the Asian and the North American summer monsoon 000906264 260__ $$aKatlenburg-Lindau$$bEGU$$c2022 000906264 3367_ $$2DRIVER$$aarticle 000906264 3367_ $$2DataCite$$aOutput Types/Journal article 000906264 3367_ $$0PUB:(DE-HGF)16$$2PUB:(DE-HGF)$$aJournal Article$$bjournal$$mjournal$$s1645005316_18216 000906264 3367_ $$2BibTeX$$aARTICLE 000906264 3367_ $$2ORCID$$aJOURNAL_ARTICLE 000906264 3367_ $$00$$2EndNote$$aJournal Article 000906264 520__ $$aEfficient transport pathways for ozone-depleting very short-lived substances (VSLSs) from their source regions into the stratosphere are a matter of current scientific debate; however they have yet to be fully identified on an observational basis. Understanding the increasing impact of chlorine-containing VSLSs (Cl-VSLSs) on stratospheric ozone depletion is important in order to validate and improve model simulations and future predictions. We report on a transport study using airborne in situ measurements of the Cl-VSLSs dichloromethane (CH2Cl2) and trichloromethane (chloroform, CHCl3) to derive a detailed description of two transport pathways from (sub)tropical source regions into the extratropical upper troposphere and lower stratosphere (Ex-UTLS) in the Northern Hemisphere (NH) late summer. The Cl-VSLS measurements were obtained in the upper troposphere and lower stratosphere (UTLS) above western Europe and the midlatitude Atlantic Ocean in the frame of the WISE (Wave-driven ISentropic Exchange) aircraft campaign in autumn 2017 and are combined with the results from a three-dimensional simulation of a Lagrangian transport model as well as back-trajectory calculations. Compared to background measurements of similar age we find up to 150 % enhanced CH2Cl2 and up to 100 % enhanced CHCl3 mixing ratios in the extratropical lower stratosphere (Ex-LS). We link the measurements of enhanced CH2Cl2 and CHCl3 mixing ratios to emissions in the region of southern and eastern Asia. Transport from this area to the Ex-LS at potential temperatures in the range of 370–400 K takes about 6–11 weeks via the Asian summer monsoon anticyclone (ASMA). Our measurements suggest anthropogenic sources to be the cause of these strongly elevated Cl-VSLS concentrations observed at the top of the lowermost stratosphere (LMS). A faster transport pathway into the Ex-LS is derived from particularly low CH2Cl2 and CHCl3 mixing ratios in the UTLS. These low mixing ratios reflect weak emissions and a local seasonal minimum of both species in the boundary layer of Central America and the tropical Atlantic. We show that air masses uplifted by hurricanes, the North American monsoon, and general convection above Central America into the tropical tropopause layer to potential temperatures of about 360–370 K are transported isentropically within 5–9 weeks from the boundary layer into the Ex-LS. This transport pathway linked to the North American monsoon mainly impacts the middle and lower part of the LMS with particularly low CH2Cl2 and CHCl3 mixing ratios. In a case study, we specifically analyze air samples directly linked to the uplift by the Category 5 Hurricane Maria that occurred during October 2017 above the Atlantic Ocean. CH2Cl2 and CHCl3 have similar atmospheric sinks and lifetimes, but the fraction of biogenic emissions is clearly higher for CHCl3 than for the mainly anthropogenically emitted CH2Cl2; consequently lower CHCl3 : CH2Cl2 ratios are expected in air parcels showing a higher impact of anthropogenic emissions. The observed CHCl3 : CH2Cl2 ratio suggests clearly stronger anthropogenic emissions in the region of southern and eastern Asia compared to those in the region of Central America and the tropical Atlantic. Overall, the transport of strongly enhanced CH2Cl2 and CHCl3 mixing ratios from southern and eastern Asia via the ASMA is the main factor in increasing the chlorine loading from the analyzed VSLSs in the Ex-LS during the NH late summer. Thus, further increases in Asian CH2Cl2 and CHCl3 emissions, as frequently reported in recent years, will further increase the impact of Cl-VSLSs on stratospheric ozone depletion. 000906264 536__ $$0G:(DE-HGF)POF4-2112$$a2112 - Climate Feedbacks (POF4-211)$$cPOF4-211$$fPOF IV$$x0 000906264 588__ $$aDataset connected to CrossRef, Journals: juser.fz-juelich.de 000906264 7001_ $$0P:(DE-Juel1)129164$$aVogel, Bärbel$$b1 000906264 7001_ $$0P:(DE-HGF)0$$aWintel, Johannes$$b2 000906264 7001_ $$0P:(DE-HGF)0$$aRau, Andrea$$b3 000906264 7001_ $$00000-0001-6582-6864$$aHoor, Peter$$b4 000906264 7001_ $$0P:(DE-HGF)0$$aBense, Vera$$b5 000906264 7001_ $$0P:(DE-Juel1)129138$$aMüller, Rolf$$b6 000906264 7001_ $$0P:(DE-Juel1)168493$$aVolk, C. 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