000912324 001__ 912324 000912324 005__ 20240712101016.0 000912324 0247_ $$2doi$$a10.1175/BAMS-D-21-0012.1 000912324 0247_ $$2ISSN$$a0003-0007 000912324 0247_ $$2ISSN$$a1520-0477 000912324 0247_ $$2Handle$$a2128/32953 000912324 0247_ $$2WOS$$aWOS:000886646700005 000912324 037__ $$aFZJ-2022-05516 000912324 082__ $$a550 000912324 1001_ $$0P:(DE-HGF)0$$aVoigt, Christiane$$b0$$eCorresponding author 000912324 245__ $$aCleaner Skies during the COVID-19 Lockdown 000912324 260__ $$aBoston, Mass.$$bASM$$c2022 000912324 3367_ $$2DRIVER$$aarticle 000912324 3367_ $$2DataCite$$aOutput Types/Journal article 000912324 3367_ $$0PUB:(DE-HGF)16$$2PUB:(DE-HGF)$$aJournal Article$$bjournal$$mjournal$$s1670315666_2716 000912324 3367_ $$2BibTeX$$aARTICLE 000912324 3367_ $$2ORCID$$aJOURNAL_ARTICLE 000912324 3367_ $$00$$2EndNote$$aJournal Article 000912324 520__ $$aDuring spring 2020, the COVID-19 pandemic caused massive reductions in emissions from industry and ground and airborne transportation. To explore the resulting atmospheric composition changes, we conducted the BLUESKY campaign with two research aircraft and measured trace gases, aerosols, and cloud properties from the boundary layer to the lower stratosphere. From 16 May to 9 June 2020, we performed 20 flights in the early COVID-19 lockdown phase over Europe and the Atlantic Ocean. We found up to 50% reductions in boundary layer nitrogen dioxide concentrations in urban areas from GOME-2B satellite data, along with carbon monoxide reductions in the pollution hot spots. We measured 20%–70% reductions in total reactive nitrogen, carbon monoxide, and fine mode aerosol concentration in profiles over German cities compared to a 10-yr dataset from passenger aircraft. The total aerosol mass was significantly reduced below 5 km altitude, and the organic aerosol fraction also aloft, indicative of decreased organic precursor gas emissions. The reduced aerosol optical thickness caused a perceptible shift in sky color toward the blue part of the spectrum (hence BLUESKY) and increased shortwave radiation at the surface. We find that the 80% decline in air traffic led to substantial reductions in nitrogen oxides at cruise altitudes, in contrail cover, and in resulting radiative forcing. The light extinction and depolarization by cirrus were also reduced in regions with substantially decreased air traffic. General circulation–chemistry model simulations indicate good agreement with the measurements when applying a reduced emission scenario. The comprehensive BLUESKY dataset documents the major impact of anthropogenic emissions on the atmospheric composition. 000912324 536__ $$0G:(DE-HGF)POF4-2111$$a2111 - Air Quality (POF4-211)$$cPOF4-211$$fPOF IV$$x0 000912324 588__ $$aDataset connected to CrossRef, Journals: juser.fz-juelich.de 000912324 7001_ $$0P:(DE-HGF)0$$aLelieveld, Jos$$b1 000912324 7001_ $$0P:(DE-HGF)0$$aSchlager, Hans$$b2 000912324 7001_ $$0P:(DE-Juel1)130949$$aSchneider, Johannes$$b3 000912324 7001_ $$0P:(DE-HGF)0$$aCurtius, Joachim$$b4 000912324 7001_ $$0P:(DE-HGF)0$$aMeerkötter, Ralf$$b5 000912324 7001_ $$0P:(DE-HGF)0$$aSauer, Daniel$$b6 000912324 7001_ $$0P:(DE-HGF)0$$aBugliaro, Luca$$b7 000912324 7001_ $$0P:(DE-Juel1)2693$$aBohn, Birger$$b8$$ufzj 000912324 7001_ $$0P:(DE-HGF)0$$aCrowley, John N.$$b9 000912324 7001_ $$0P:(DE-HGF)0$$aErbertseder, Thilo$$b10 000912324 7001_ $$0P:(DE-HGF)0$$aGroß, Silke$$b11 000912324 7001_ $$0P:(DE-HGF)0$$aHahn, Valerian$$b12 000912324 7001_ $$0P:(DE-Juel1)177066$$aLi, Qiang$$b13$$ufzj 000912324 7001_ $$0P:(DE-HGF)0$$aMertens, Mariano$$b14 000912324 7001_ $$0P:(DE-HGF)0$$aPöhlker, Mira L.$$b15 000912324 7001_ $$0P:(DE-HGF)0$$aPozzer, Andrea$$b16 000912324 7001_ $$0P:(DE-HGF)0$$aSchumann, Ulrich$$b17 000912324 7001_ $$0P:(DE-HGF)0$$aTomsche, Laura$$b18 000912324 7001_ $$0P:(DE-HGF)0$$aWilliams, Jonathan$$b19 000912324 7001_ $$0P:(DE-HGF)0$$aZahn, Andreas$$b20 000912324 7001_ $$0P:(DE-HGF)0$$aAndreae, Meinrat$$b21 000912324 7001_ $$0P:(DE-HGF)0$$aBorrmann, Stephan$$b22 000912324 7001_ $$0P:(DE-HGF)0$$aBräuer, Tiziana$$b23 000912324 7001_ $$0P:(DE-HGF)0$$aDörich, Raphael$$b24 000912324 7001_ $$0P:(DE-HGF)0$$aDörnbrack, Andreas$$b25 000912324 7001_ $$0P:(DE-HGF)0$$aEdtbauer, Achim$$b26 000912324 7001_ $$0P:(DE-HGF)0$$aErnle, Lisa$$b27 000912324 7001_ $$0P:(DE-HGF)0$$aFischer, Horst$$b28 000912324 7001_ $$0P:(DE-HGF)0$$aGiez, Andreas$$b29 000912324 7001_ $$0P:(DE-HGF)0$$aGranzin, Manuel$$b30 000912324 7001_ $$0P:(DE-HGF)0$$aGrewe, Volker$$b31 000912324 7001_ $$0P:(DE-HGF)0$$aHarder, Hartwig$$b32 000912324 7001_ $$0P:(DE-HGF)0$$aHeinritzi, Martin$$b33 000912324 7001_ $$0P:(DE-HGF)0$$aHolanda, Bruna A.$$b34 000912324 7001_ $$0P:(DE-Juel1)188765$$aJöckel, Patrick$$b35 000912324 7001_ $$0P:(DE-HGF)0$$aKaiser, Katharina$$b36 000912324 7001_ $$0P:(DE-HGF)0$$aKrüger, Ovid O.$$b37 000912324 7001_ $$0P:(DE-HGF)0$$aLucke, Johannes$$b38 000912324 7001_ $$0P:(DE-HGF)0$$aMarsing, Andreas$$b39 000912324 7001_ $$0P:(DE-HGF)0$$aMartin, Anna$$b40 000912324 7001_ $$0P:(DE-HGF)0$$aMatthes, Sigrun$$b41 000912324 7001_ $$0P:(DE-HGF)0$$aPöhlker, Christopher$$b42 000912324 7001_ $$0P:(DE-HGF)0$$aPöschl, Ulrich$$b43 000912324 7001_ $$0P:(DE-HGF)0$$aReifenberg, Simon$$b44 000912324 7001_ $$0P:(DE-HGF)0$$aRingsdorf, Akima$$b45 000912324 7001_ $$0P:(DE-HGF)0$$aScheibe, Monika$$b46 000912324 7001_ $$0P:(DE-HGF)0$$aTadic, Ivan$$b47 000912324 7001_ $$0P:(DE-HGF)0$$aZauner-Wieczorek, Marcel$$b48 000912324 7001_ $$0P:(DE-HGF)0$$aHenke, Rolf$$b49 000912324 7001_ $$0P:(DE-HGF)0$$aRapp, Markus$$b50 000912324 773__ $$0PERI:(DE-600)2029396-3$$a10.1175/BAMS-D-21-0012.1$$gVol. 103, no. 8, p. 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