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| Titel |
Modeling the South American regional smoke plume: aerosol optical depth variability and surface shortwave flux perturbation |
| VerfasserIn |
N. E. Rosário, K. M. Longo, S. R. Freitas, M. A. Yamasoe, R. M. Fonseca |
| 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 ; 13, no. 6 ; Nr. 13, no. 6 (2013-03-15), S.2923-2938 |
| Datensatznummer |
250018511
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| Publikation (Nr.) |
 copernicus.org/acp-13-2923-2013.pdf |
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| Zusammenfassung |
| Intra-seasonal variability of smoke aerosol optical depth (AOD) and
downwelling solar irradiance at the surface during the 2002 biomass burning
season in South America was modeled using the Coupled
Chemistry-Aerosol-Tracers Transport model with the Brazilian developments on
the Regional Atmospheric Modeling System (CCATT-BRAMS). Measurements of
total and fine mode fraction (FMF) AOD from the AErosol RObotic NETwork
(AERONET) and solar irradiance at the surface from the Solar Radiation
Network (SolRad-NET) were used to evaluate model results. In general, the
major features associated with AOD evolution over the southern part of the
Amazon basin and cerrado ecosystem are captured by the model. The main
discrepancies were found for high aerosol loading events. In the
northeastern portion of the Amazon basin the model systematically
underestimated total AOD, as expected, since smoke contribution is not
dominant as it is in the southern portion and emissions other than smoke
were not considered in the simulation. Better agreement was obtained
comparing the model results with observed FMF AOD, which pointed out the
relevance of coarse mode aerosol emission in that region. Likewise, major
discrepancies over cerrado during high AOD events were found to be
associated with coarse mode aerosol omission in our model. The issue of high
aerosol loading events in the southern part of the Amazon was related to
difficulties in predicting the smoke AOD field, which was discussed in the
context of emissions shortcomings. The Cuiabá cerrado site was the only
one where the highest quality AERONET data were unavailable for both total
and FMF AOD. Thus, lower quality data were used. Root-mean-square error
(RMSE) between the model and observed FMF AOD decreased from 0.34 to 0.19
when extreme AOD events (FMF AOD550 nm ≥ 1.0) and Cuiabá
were excluded from the analysis. Downward surface solar irradiance
comparisons also followed similar trends when extreme AOD were excluded.
This highlights the need to improve modelling of the regional smoke plume in
order to enhance the accuracy of the radiative energy budget. An aerosol
optical model based on the mean intensive properties of smoke from the
southern part of the Amazon basin produced a radiative flux perturbation
efficiency (RFPE) of −158 Wm−2/AOD550 nm at noon. This value
falls between −154 Wm−2/AOD550 nm and −187 Wm−2/AOD550 nm,
the range obtained when spatially varying
optical models were considered. The 24 h average surface radiative flux
perturbation over the biomass burning season varied from −55 Wm−2 close
to smoke sources in the southern part of the Amazon basin and cerrado to −10 Wm−2
in remote regions of the southeast Brazilian coast. |
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