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| Titel |
Characterising Brazilian biomass burning emissions using WRF-Chem with MOSAIC sectional aerosol |
| VerfasserIn |
S. Archer-Nicholls, D. Lowe, E. Darbyshire, W. T. Morgan, M. M. Bela, G. Pereira, J. Trembath, J. W. Kaiser, K. M. Longo, S. R. Freitas, H. Coe, G. McFiggans |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1991-959X
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| Digitales Dokument |
URL |
| Erschienen |
In: Geoscientific Model Development ; 8, no. 3 ; Nr. 8, no. 3 (2015-03-12), S.549-577 |
| Datensatznummer |
250116176
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| Publikation (Nr.) |
 copernicus.org/gmd-8-549-2015.pdf |
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| Zusammenfassung |
The South American Biomass Burning Analysis (SAMBBA) field campaign
took detailed in situ flight measurements of aerosol during the 2012
dry season to characterise biomass burning aerosol and improve
understanding of its impacts on weather and climate. Developments
have been made to the Weather Research and Forecast model with
chemistry (WRF-Chem) model to improve the representation of biomass
burning aerosol in the region, by coupling a sectional aerosol scheme
to the plume-rise parameterisation. Brazilian Biomass Burning
Emissions Model (3BEM) fire emissions are used, prepared using
PREP-CHEM-SRC, and mapped to CBM-Z and MOSAIC species. Model results
have been evaluated against remote sensing products, AERONET sites,
and four case studies of flight measurements from the SAMBBA
campaign.
WRF-Chem predicted layers of elevated aerosol loadings
(5–20 μg sm−3) of particulate organic matter at high
altitude (6–8 km) over tropical forest regions, while
flight measurements showed a sharp decrease above 2–4 km
altitude. This difference was attributed to the plume-rise
parameterisation overestimating injection height. The 3BEM emissions
product was modified using estimates of active fire size and burned
area for the 2012 fire season, which reduced the fire size. The
enhancement factor for fire emissions was increased from 1.3 to 5 to
retain reasonable aerosol optical depths (AODs). The smaller fire
size lowered the injection height of the emissions, but WRF-Chem
still showed elevated aerosol loadings between 4–5 km
altitude. Over eastern cerrado (savannah-like) regions, both
modelled and measured aerosol loadings decreased above approximately
4 km altitude.
Compared with MODIS satellite data and AERONET sites, WRF-Chem
represented AOD magnitude well (between 0.3–1.5) over western
tropical forest fire regions in the first half of the campaign, but
tended to over-predict them in the second half, when precipitation
was more significant. Over eastern cerrado regions, WRF-Chem tended
to under-predict AODs. Modelled aerosol loadings in the east were
higher in the modified emission scenario. The primary organic
matter to black carbon ratio was typically between 8–10 in
WRF-Chem. This was lower than the western flight measurements
(interquartile range of 11.6–15.7 in B734, 14.7–24.0 in B739), but
similar to the eastern flight B742 (8.1–10.4). However, single
scattering albedo was close to measured over the western flights
(0.87–0.89 in model; 0.86–0.91 in flight B734, and 0.81–0.95 in
flight B739 measurements) but too high over the eastern flight B742
(0.86–0.87 in model, 0.79–0.82 in measurements). This suggests
that improvements are needed to both modelled aerosol composition and
optical properties calculations in WRF-Chem. |
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