In:
Atmospheric Chemistry and Physics, Copernicus GmbH, Vol. 22, No. 16 ( 2022-08-26), p. 10901-10917
Abstract:
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.
Type of Medium:
Online Resource
ISSN:
1680-7324
DOI:
10.5194/acp-22-10901-2022
Language:
English
Publisher:
Copernicus GmbH
Publication Date:
2022
detail.hit.zdb_id:
2092549-9
detail.hit.zdb_id:
2069847-1
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