Long-range transported North American wildfire aerosols observed in marine boundary layer of eastern North Atlantic
Wildfire is a major source of biomass burning aerosols, which greatly impact Earth climate. Tree species in North America (NA) boreal forests can support high-intensity crown fires, resulting in elevated injection height and longer lifetime (on the order of months) of the wildfire aerosols. Given th...
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Format: | Article |
Language: | English |
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Elsevier
2020-06-01
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Series: | Environment International |
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Online Access: | http://www.sciencedirect.com/science/article/pii/S0160412019326480 |
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doaj-390d63856e35485a93b60159a9f996ca |
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record_format |
Article |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Guangjie Zheng Arthur J. Sedlacek Allison C. Aiken Yan Feng Thomas B. Watson Shira Raveh-Rubin Janek Uin Ernie R. Lewis Jian Wang |
spellingShingle |
Guangjie Zheng Arthur J. Sedlacek Allison C. Aiken Yan Feng Thomas B. Watson Shira Raveh-Rubin Janek Uin Ernie R. Lewis Jian Wang Long-range transported North American wildfire aerosols observed in marine boundary layer of eastern North Atlantic Environment International North American wildfires Dry intrusion Long-range transport Optical properties Cloud condensation nuclei activity Marine low clouds |
author_facet |
Guangjie Zheng Arthur J. Sedlacek Allison C. Aiken Yan Feng Thomas B. Watson Shira Raveh-Rubin Janek Uin Ernie R. Lewis Jian Wang |
author_sort |
Guangjie Zheng |
title |
Long-range transported North American wildfire aerosols observed in marine boundary layer of eastern North Atlantic |
title_short |
Long-range transported North American wildfire aerosols observed in marine boundary layer of eastern North Atlantic |
title_full |
Long-range transported North American wildfire aerosols observed in marine boundary layer of eastern North Atlantic |
title_fullStr |
Long-range transported North American wildfire aerosols observed in marine boundary layer of eastern North Atlantic |
title_full_unstemmed |
Long-range transported North American wildfire aerosols observed in marine boundary layer of eastern North Atlantic |
title_sort |
long-range transported north american wildfire aerosols observed in marine boundary layer of eastern north atlantic |
publisher |
Elsevier |
series |
Environment International |
issn |
0160-4120 |
publishDate |
2020-06-01 |
description |
Wildfire is a major source of biomass burning aerosols, which greatly impact Earth climate. Tree species in North America (NA) boreal forests can support high-intensity crown fires, resulting in elevated injection height and longer lifetime (on the order of months) of the wildfire aerosols. Given the long lifetime, the properties of aged NA wildfire aerosols are required to understand and quantify their effects on radiation and climate. Here we present comprehensive characterization of climatically relevant properties, including optical properties and cloud condensation nuclei (CCN) activities of aged NA wildfire aerosols, emitted from the record-breaking Canadian wildfires in August 2017. Despite the extreme injection height of ~12 km, some of the wildfire plumes descended into the marine boundary layer in the eastern North Atlantic over a period of ~2 weeks, owing to the dry intrusions behind mid-latitude cyclones. The aged wildfire aerosols have high single scattering albedos at 529 nm (ω529; 0.92–0.95) while low absorption Ångström exponents (Åabs) at 464 nm/648 nm (0.7–0.9). In comparison, Åabs of fresh/slightly aged ones are typically 1.4–3.5. This low Åabs indicates a nearly complete loss of brown carbon, likely due to bleaching and/or evaporation, during the long-range transport. The nearly complete loss suggests that on global average, direct radiative forcing of BrC may be minor. Combining Mie calculations and the measured aerosol hygroscopicity, volatility and size distributions, we show that the high ω529 and low Åabs values are best explained by an external mixture of non-absorbing organic particles and absorbing particles of large BC cores (>~110 nm diameter) with thick non-absorbing coatings. The accelerated descent of the wildfire plume also led to strong increase of CCN concentration at the supersaturation levels representative of marine low clouds. The hygroscopicity parameter, κCCN, of the aged wildfire aerosols varies from 0.2 to 0.4, substantially lower than that of background marine boundary layer aerosols. However, the high fraction of particles with large diameter (i.e., within accumulation size ranges, ~100–250 nm) compensates for the low values of κ, and as a result, the aged NA wildfire aerosols contribute more efficiently to CCN population. These results provide direct evidence that the long-range transported NA wildfires can strongly influence CCN concentration in remote marine boundary layer, therefore the radiative properties of marine low clouds. Given the expected increases of NA wildfire intensity and frequency and regular occurrence of dry intrusion following mid-latitude cyclones, the influence of NA wildfire aerosols on CCN and clouds in remote marine environment need to be further examined. |
topic |
North American wildfires Dry intrusion Long-range transport Optical properties Cloud condensation nuclei activity Marine low clouds |
url |
http://www.sciencedirect.com/science/article/pii/S0160412019326480 |
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doaj-390d63856e35485a93b60159a9f996ca2020-11-25T03:29:33ZengElsevierEnvironment International0160-41202020-06-01139Long-range transported North American wildfire aerosols observed in marine boundary layer of eastern North AtlanticGuangjie Zheng0Arthur J. Sedlacek1Allison C. Aiken2Yan Feng3Thomas B. Watson4Shira Raveh-Rubin5Janek Uin6Ernie R. Lewis7Jian Wang8Center for Aerosol Science and Engineering, Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, MO, USA; Environmental and Climate Science Department, Brookhaven National Laboratory, Upton, NY, USAEnvironmental and Climate Science Department, Brookhaven National Laboratory, Upton, NY, USAEarth System Observations, Los Alamos National Laboratory, Los Alamos, NM, USAEnvironmental Science Division, Argonne National Laboratory, Lemont, IL, USAEnvironmental and Climate Science Department, Brookhaven National Laboratory, Upton, NY, USAEarth and Planetary Sciences, Weizmann Institute of Science, Rehovot, IsraelEnvironmental and Climate Science Department, Brookhaven National Laboratory, Upton, NY, USAEnvironmental and Climate Science Department, Brookhaven National Laboratory, Upton, NY, USACenter for Aerosol Science and Engineering, Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, MO, USA; Environmental and Climate Science Department, Brookhaven National Laboratory, Upton, NY, USA; Corresponding author at: Center for Aerosol Science and Engineering, Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, Missouri, USA.Wildfire is a major source of biomass burning aerosols, which greatly impact Earth climate. Tree species in North America (NA) boreal forests can support high-intensity crown fires, resulting in elevated injection height and longer lifetime (on the order of months) of the wildfire aerosols. Given the long lifetime, the properties of aged NA wildfire aerosols are required to understand and quantify their effects on radiation and climate. Here we present comprehensive characterization of climatically relevant properties, including optical properties and cloud condensation nuclei (CCN) activities of aged NA wildfire aerosols, emitted from the record-breaking Canadian wildfires in August 2017. Despite the extreme injection height of ~12 km, some of the wildfire plumes descended into the marine boundary layer in the eastern North Atlantic over a period of ~2 weeks, owing to the dry intrusions behind mid-latitude cyclones. The aged wildfire aerosols have high single scattering albedos at 529 nm (ω529; 0.92–0.95) while low absorption Ångström exponents (Åabs) at 464 nm/648 nm (0.7–0.9). In comparison, Åabs of fresh/slightly aged ones are typically 1.4–3.5. This low Åabs indicates a nearly complete loss of brown carbon, likely due to bleaching and/or evaporation, during the long-range transport. The nearly complete loss suggests that on global average, direct radiative forcing of BrC may be minor. Combining Mie calculations and the measured aerosol hygroscopicity, volatility and size distributions, we show that the high ω529 and low Åabs values are best explained by an external mixture of non-absorbing organic particles and absorbing particles of large BC cores (>~110 nm diameter) with thick non-absorbing coatings. The accelerated descent of the wildfire plume also led to strong increase of CCN concentration at the supersaturation levels representative of marine low clouds. The hygroscopicity parameter, κCCN, of the aged wildfire aerosols varies from 0.2 to 0.4, substantially lower than that of background marine boundary layer aerosols. However, the high fraction of particles with large diameter (i.e., within accumulation size ranges, ~100–250 nm) compensates for the low values of κ, and as a result, the aged NA wildfire aerosols contribute more efficiently to CCN population. These results provide direct evidence that the long-range transported NA wildfires can strongly influence CCN concentration in remote marine boundary layer, therefore the radiative properties of marine low clouds. Given the expected increases of NA wildfire intensity and frequency and regular occurrence of dry intrusion following mid-latitude cyclones, the influence of NA wildfire aerosols on CCN and clouds in remote marine environment need to be further examined.http://www.sciencedirect.com/science/article/pii/S0160412019326480North American wildfiresDry intrusionLong-range transportOptical propertiesCloud condensation nuclei activityMarine low clouds |