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| Titel |
Fire emission heights in the climate system – Part 2: Impact on transport, black carbon concentrations and radiation |
| VerfasserIn |
A. Veira, S. Kloster, N. A. J. Schutgens, J. W. Kaiser |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 15, no. 13 ; Nr. 15, no. 13 (2015-07-01), S.7173-7193 |
| Datensatznummer |
250119865
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| Publikation (Nr.) |
 copernicus.org/acp-15-7173-2015.pdf |
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| Zusammenfassung |
| Wildfires represent a major source for aerosols impacting atmospheric
radiation, atmospheric chemistry and cloud micro-physical
properties. Previous case studies indicated that the height of the
aerosol–radiation interaction may crucially affect atmospheric radiation,
but the sensitivity to emission heights has been examined with only a few
models and is still uncertain. In this study we use the general circulation
model ECHAM6 extended by the aerosol module HAM2 to investigate the impact
of wildfire emission heights on atmospheric long-range transport,
black carbon (BC) concentrations and atmospheric radiation. We
simulate the wildfire aerosol release using either various versions of
a semi-empirical plume height parametrization or prescribed standard
emission heights in ECHAM6-HAM2. Extreme scenarios of near-surface or
free-tropospheric-only injections provide lower and upper constraints
on the emission height climate impact. We find relative changes in
mean global atmospheric BC burden of up to 7.9±4.4 %
caused by average changes in emission heights of
1.5–3.5 km. Regionally, changes in BC burden exceed
30–40 % in the major biomass burning regions. The model
evaluation of aerosol optical thickness (AOT) against Moderate Resolution Imaging Spectroradiometer (MODIS), AErosol RObotic NETwork (AERONET)
and Cloud–Aerosol Lidar with Orthogonal Polarization (CALIOP) observations indicates that the implementation of a plume
height parametrization slightly reduces the ECHAM6-HAM2 biases
regionally, but on the global scale these improvements in model
performance are small. For prescribed emission release at the surface,
wildfire emissions entail a total sky top-of-atmosphere (TOA)
radiative forcing (RF) of −0.16±0.06 W m−2. The
application of a plume height parametrization which agrees reasonably
well with observations introduces a slightly stronger negative TOA RF
of −0.20±0.07 W m−2. The standard ECHAM6-HAM2 model in
which 25 % of the wildfire emissions are injected into the
free troposphere (FT) and 75 % into the planetary boundary layer (PBL),
leads to a TOA RF of −0.24±0.06 W m−2. Overall, we
conclude that simple plume height parametrizations provide sufficient
representations of emission heights for global climate
modeling. Significant improvements in aerosol wildfire modeling likely
depend on better emission inventories and aerosol process modeling
rather than on improved emission height parametrizations. |
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