Black carbon aerosol reductions during COVID-19 confinement quantified by aircraft measurements over Europe

Krüger, Ovid O.; Holanda, Bruna A.; Chowdhury, Sourangsu; Pozzer, Andrea; Walter, David; Pöhlker, Christopher; Hernández, Maria Dolores Andrés; Burrows, John P.; Voigt, Christiane; Lelieveld, Jos; Quaas, Johannes; Pöschl, Ulrich; Pöhlker, Mira L.

doi:10.5194/acp-22-8683-2022

Cited by 17 publications

(9 citation statements)

References 86 publications

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“…Importantly, the mobility data-based estimates of aerosol emission changes as used in CovidMIP were found to agree well with aerosol measurements conducted during aircraft campaigns, e.g. measuring BC reductions over Europe in May and June 2020 (Krueger et al, 2022).…”

Section: Discussionsupporting

confidence: 65%

Hemispheric-wide climate response to regional COVID-19-related aerosol emission reductions: the prominent role of atmospheric circulation adjustments

Fahrenbach

Bollasina

2022

Preprint

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Abstract. The national and global restrictions in response to the COVID-19 pandemic led to a sudden, albeit temporary, emission reduction of many greenhouse gases (GHGs) and anthropogenic aerosols, whose near-term climate impact was previously found to be negligible when focusing on global- and/or annual-mean scales. Our study aims to investigate the monthly-scale coupled climate and circulation response to regional, COVID-19-related aerosol emission reductions, using the output from ten Earth System Models participating in the Covid Model Intercomparison Project (CovidMIP). We focus on January–February and March–May 2020, which represent the seasons of largest emission changes in sulphate (SO2) and black carbon (BC). During JF, a marked decrease in aerosol emissions over eastern China, the main emission region, results in a lower aerosol burden, leading to an increase in surface downwelling radiation and ensuing surface warming. Regional sea-level pressure and circulation adjustments drive a precipitation increase over the Maritime Continent, embedded in a negative PDO/ENSO-like response over the Pacific, in turn associated with a northwestward displacement and zonal shrinking of the Indo-Pacific Walker cell. Remote climate anomalies across the Northern Hemisphere, including a weakening of the Siberian High and Aleutian Low as well as anomalous temperature patterns in the northern mid-latitudes, arise primarily as a result of stationary Rossby wave trains generated over East Asia. The anomalous climate pattern and driving dynamical mechanism reverse polarity between JF and MAM 2020, which is shown to be consistent with an underlying shift of the dominant region of SO2 emission reduction from eastern China in JF to India in MAM. Our findings highlight the prominent role of large-scale dynamical adjustments in generating a hemispheric-wide aerosol climate imprint even on short time scales, which are largely consistent with longer-term (decadal) trends. Furthermore, our analysis shows the sensitivity of the climate response to the geographical location of the aerosol emission region, even after relatively small, but abrupt, emission changes. Scientific advances in understanding the climate impact of regional aerosol perturbations, especially the rapidly evolving emissions over China and India, are critically needed to reduce current uncertainties in near-future climate projections and to develop scientifically informed hazard mitigation and adaptation policies.

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Section: Discussionsupporting

confidence: 65%

Hemispheric-wide climate response to regional COVID-19-related aerosol emission reductions: the prominent role of atmospheric circulation adjustments

Fahrenbach

Bollasina

2022

Preprint

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“…In particular, during five days with coordinated flights over Germany (23,26,and 28 May) and over the North Atlantic (30 May, 2 June), the payload offered the opportunity to probe the air masses in more detail. An overview of the BLUESKY mission is given in Voigt et al (2022), and further detailed studies are published by Schumann et al (2021a, b), Reifenberg et al (2022), Nussbaumer et al (2022), Hamryszczak et al (2022), andKrüger et al (2022). In the present study we will focus on the sulfur compounds in the upper troposphere and lower stratosphere.…”

Section: Bluesky Missionmentioning

confidence: 99%

Enhanced sulfur in the upper troposphere and lower stratosphere in spring 2020

et al. 2022

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Abstract. Sulfur compounds in the upper troposphere and lower stratosphere (UTLS) impact the atmosphere radiation budget, either directly as particles or indirectly as precursor gas for new particle formation. In situ measurements in the UTLS are rare but are important to better understand the impact of the sulfur budget on climate. The BLUESKY mission in May and June 2020 explored an unprecedented situation. (1) The UTLS experienced extraordinary dry conditions in spring 2020 over Europe, in comparison to previous years, and (2) the first lockdown of the COVID-19 pandemic caused major emission reductions from industry, ground, and airborne transportation. With the two research aircraft HALO and Falcon, 20 flights were conducted over central Europe and the North Atlantic to investigate the atmospheric composition with respect to trace gases, aerosol, and clouds. Here, we focus on measurements of sulfur dioxide (SO2) and particulate sulfate (SO42-) in the altitude range of 8 to 14.5 km which show unexpectedly enhanced mixing ratios of SO2 in the upper troposphere and of SO42- in the lowermost stratosphere. In the UT, we find SO2 mixing ratios of (0.07±0.01) ppb, caused by the remaining air traffic, and reduced SO2 sinks due to low OH and low cloud fractions and to a minor extent by uplift from boundary layer sources. Particulate sulfate showed elevated mixing ratios of up to 0.33 ppb in the LS. We suggest that the eruption of the volcano Raikoke in June 2019, which emitted about 1 Tg SO2 into the stratosphere in northern midlatitudes, caused these enhancements, in addition to Siberian and Canadian wildfires and other minor volcanic eruptions. Our measurements can help to test models and lead to new insights in the distribution of sulfur compounds in the UTLS, their sources, and sinks. Moreover, these results can contribute to improving simulations of the radiation budget in the UTLS with respect to sulfur effects.

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“…The NRMSE of 0.09 is relatively low, as the higher abundance closer to the surface -that is, closer to the sources -is well represented, both in terms of magnitude and variability. A detail analysis of the black carbon concentration simulated with the EMAC model during the BLUESKY campaign can be found in Krüger et al (2022).…”

Section: Aerosolsmentioning

confidence: 99%

Numerical simulation of the impact of COVID-19 lockdown on tropospheric composition and aerosol radiative forcing in Europe

et al. 2022

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Abstract. Aerosols influence the Earth's energy balance directly by modifying the radiation transfer and indirectly by altering the cloud microphysics. Anthropogenic aerosol emissions dropped considerably when the global COVID-19 pandemic resulted in severe restraints on mobility, production, and public life in spring 2020. We assess the effects of these reduced emissions on direct and indirect aerosol radiative forcing over Europe, excluding contributions from contrails. We simulate the atmospheric composition with the ECHAM5/MESSy Atmospheric Chemistry (EMAC) model in a baseline (business-as-usual) and a reduced emission scenario. The model results are compared to aircraft observations from the BLUESKY aircraft campaign performed in May–June 2020 over Europe. The model agrees well with most of the observations, except for sulfur dioxide, particulate sulfate, and nitrate in the upper troposphere, likely due to a biased representation of stratospheric aerosol chemistry and missing information about volcanic eruptions. The comparison with a baseline scenario shows that the largest relative differences for tracers and aerosols are found in the upper troposphere, around the aircraft cruise altitude, due to the reduced aircraft emissions, while the largest absolute changes are present at the surface. We also find an increase in all-sky shortwave radiation of 0.21 ± 0.05 W m−2 at the surface in Europe for May 2020, solely attributable to the direct aerosol effect, which is dominated by decreased aerosol scattering of sunlight, followed by reduced aerosol absorption caused by lower concentrations of inorganic and black carbon aerosols in the troposphere. A further increase in shortwave radiation from aerosol indirect effects was found to be much smaller than its variability. Impacts on ice crystal concentrations, cloud droplet number concentrations, and effective crystal radii are found to be negligible.

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Black carbon aerosol reductions during COVID-19 confinement quantified by aircraft measurements over Europe

Cited by 17 publications

References 86 publications

Hemispheric-wide climate response to regional COVID-19-related aerosol emission reductions: the prominent role of atmospheric circulation adjustments

Hemispheric-wide climate response to regional COVID-19-related aerosol emission reductions: the prominent role of atmospheric circulation adjustments

Enhanced sulfur in the upper troposphere and lower stratosphere in spring 2020

Numerical simulation of the impact of COVID-19 lockdown on tropospheric composition and aerosol radiative forcing in Europe

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