Physical and optical properties of aged biomass burning aerosol from wildfires in Siberia and the Western USA at the Mt. Bachelor Observatory
The summer of 2015 was an extreme forest fire year in the Pacific Northwest. Our sample site at the Mt. Bachelor Observatory (MBO, 2.7 km a.s.l.) in central Oregon observed biomass burning (BB) events more than 50 % of the time during August. In this paper we characterize the aerosol physical an...
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2016-12-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/16/15185/2016/acp-16-15185-2016.pdf |
| _version_ | 1819168609252933632 |
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| author | J. R. Laing D. A. Jaffe D. A. Jaffe J. R. Hee |
| author_facet | J. R. Laing D. A. Jaffe D. A. Jaffe J. R. Hee |
| author_sort | J. R. Laing |
| collection | DOAJ |
| description | The summer of 2015 was an extreme forest fire year in the Pacific
Northwest. Our sample site at the Mt. Bachelor Observatory (MBO,
2.7 km a.s.l.) in central Oregon observed biomass burning (BB) events more
than 50 % of the time during August. In this paper we characterize the
aerosol physical and optical properties of 19 aged BB events during August
2015. Six of the 19 events were influenced by Siberian fires
originating near Lake Baikal that were transported to MBO over 4–10 days.
The remainder of the events resulted from wildfires in Northern California
and Southwestern Oregon with transport times to MBO ranging from 3 to 35 h.
Fine particulate matter (PM<sub>1</sub>), carbon monoxide (CO), aerosol light
scattering coefficients (<i>σ</i><sub>scat</sub>), aerosol light absorption
coefficients (<i>σ</i><sub>abs</sub>), and aerosol number size distributions
were measured throughout the campaign. We found that the Siberian events had
a significantly higher Δ<i>σ</i><sub>abs</sub>∕ΔCO enhancement
ratio, higher mass absorption efficiency (MAE; Δ<i>σ</i><sub>abs</sub>∕ΔPM<sub>1</sub>), lower single scattering albedo (<i>ω</i>), and lower absorption Ångström exponent (AAE) when compared with
the regional events. We suggest that the observed Siberian events represent
that portion of the plume that has hotter flaming fire conditions and thus
enabled strong pyroconvective lofting and long-range transport to MBO. The
Siberian events observed at MBO therefore represent a selected portion of the
original plume that would then have preferentially higher black carbon
emissions and thus an enhancement in absorption. The lower AAE values in the
Siberian events compared to regional events indicate a lack of brown carbon
(BrC) production by the Siberian fires or a loss of BrC during transport. We
found that mass scattering efficiencies (MSE) for the BB events ranged from
2.50 to 4.76 m<sup>2</sup> g<sup>−1</sup>. We measured aerosol size distributions with a
scanning mobility particle sizer (SMPS). Number size distributions ranged
from unimodal to bimodal and had geometric mean diameters (<i>D</i><sub>pm</sub>)
ranging from 138 to 229 nm and geometric standard deviations
(<i>σ</i><sub>g</sub>) ranging from 1.53 to 1.89. We found MSEs for BB events to
be positively correlated with the geometric mean of the aerosol size
distributions (<i>R</i><sup>2</sup> = 0.73), which agrees with Mie theory. We did not find any dependence on event size distribution to transport time or fire source
location. |
| first_indexed | 2024-12-22T19:06:19Z |
| format | Article |
| id | doaj.art-2fce9b129fea489aa7975ce193516635 |
| institution | Directory Open Access Journal |
| issn | 1680-7316 1680-7324 |
| language | English |
| last_indexed | 2024-12-22T19:06:19Z |
| publishDate | 2016-12-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Chemistry and Physics |
| spelling | doaj.art-2fce9b129fea489aa7975ce1935166352022-12-21T18:15:49ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242016-12-0116151851519710.5194/acp-16-15185-2016Physical and optical properties of aged biomass burning aerosol from wildfires in Siberia and the Western USA at the Mt. Bachelor ObservatoryJ. R. Laing0D. A. Jaffe1D. A. Jaffe2J. R. Hee3School of Science and Technology, University of Washington Bothell, Bothell, WA, USASchool of Science and Technology, University of Washington Bothell, Bothell, WA, USADepartment of Atmospheric Science, University of Washington, Seattle, WA, USASchool of Science and Technology, University of Washington Bothell, Bothell, WA, USAThe summer of 2015 was an extreme forest fire year in the Pacific Northwest. Our sample site at the Mt. Bachelor Observatory (MBO, 2.7 km a.s.l.) in central Oregon observed biomass burning (BB) events more than 50 % of the time during August. In this paper we characterize the aerosol physical and optical properties of 19 aged BB events during August 2015. Six of the 19 events were influenced by Siberian fires originating near Lake Baikal that were transported to MBO over 4–10 days. The remainder of the events resulted from wildfires in Northern California and Southwestern Oregon with transport times to MBO ranging from 3 to 35 h. Fine particulate matter (PM<sub>1</sub>), carbon monoxide (CO), aerosol light scattering coefficients (<i>σ</i><sub>scat</sub>), aerosol light absorption coefficients (<i>σ</i><sub>abs</sub>), and aerosol number size distributions were measured throughout the campaign. We found that the Siberian events had a significantly higher Δ<i>σ</i><sub>abs</sub>∕ΔCO enhancement ratio, higher mass absorption efficiency (MAE; Δ<i>σ</i><sub>abs</sub>∕ΔPM<sub>1</sub>), lower single scattering albedo (<i>ω</i>), and lower absorption Ångström exponent (AAE) when compared with the regional events. We suggest that the observed Siberian events represent that portion of the plume that has hotter flaming fire conditions and thus enabled strong pyroconvective lofting and long-range transport to MBO. The Siberian events observed at MBO therefore represent a selected portion of the original plume that would then have preferentially higher black carbon emissions and thus an enhancement in absorption. The lower AAE values in the Siberian events compared to regional events indicate a lack of brown carbon (BrC) production by the Siberian fires or a loss of BrC during transport. We found that mass scattering efficiencies (MSE) for the BB events ranged from 2.50 to 4.76 m<sup>2</sup> g<sup>−1</sup>. We measured aerosol size distributions with a scanning mobility particle sizer (SMPS). Number size distributions ranged from unimodal to bimodal and had geometric mean diameters (<i>D</i><sub>pm</sub>) ranging from 138 to 229 nm and geometric standard deviations (<i>σ</i><sub>g</sub>) ranging from 1.53 to 1.89. We found MSEs for BB events to be positively correlated with the geometric mean of the aerosol size distributions (<i>R</i><sup>2</sup> = 0.73), which agrees with Mie theory. We did not find any dependence on event size distribution to transport time or fire source location.https://www.atmos-chem-phys.net/16/15185/2016/acp-16-15185-2016.pdf |
| spellingShingle | J. R. Laing D. A. Jaffe D. A. Jaffe J. R. Hee Physical and optical properties of aged biomass burning aerosol from wildfires in Siberia and the Western USA at the Mt. Bachelor Observatory Atmospheric Chemistry and Physics |
| title | Physical and optical properties of aged biomass burning aerosol from wildfires in Siberia and the Western USA at the Mt. Bachelor Observatory |
| title_full | Physical and optical properties of aged biomass burning aerosol from wildfires in Siberia and the Western USA at the Mt. Bachelor Observatory |
| title_fullStr | Physical and optical properties of aged biomass burning aerosol from wildfires in Siberia and the Western USA at the Mt. Bachelor Observatory |
| title_full_unstemmed | Physical and optical properties of aged biomass burning aerosol from wildfires in Siberia and the Western USA at the Mt. Bachelor Observatory |
| title_short | Physical and optical properties of aged biomass burning aerosol from wildfires in Siberia and the Western USA at the Mt. Bachelor Observatory |
| title_sort | physical and optical properties of aged biomass burning aerosol from wildfires in siberia and the western usa at the mt bachelor observatory |
| url | https://www.atmos-chem-phys.net/16/15185/2016/acp-16-15185-2016.pdf |
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