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Tropospheric Reactive Bromine and Meteorology over the Arctic Ocean.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Tropospheric Reactive Bromine and Meteorology over the Arctic Ocean./
作者:	Swanson, William.
出版者:	Ann Arbor : ProQuest Dissertations & Theses, : 2021,
面頁冊數:	176 p.
附註:	Source: Dissertations Abstracts International, Volume: 83-01, Section: B.
Contained By:	Dissertations Abstracts International83-01B.
標題:	Atmospheric chemistry. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=28548682
ISBN:	9798535509600

Tropospheric Reactive Bromine and Meteorology over the Arctic Ocean.
Swanson, William.

Tropospheric Reactive Bromine and Meteorology over the Arctic Ocean. - Ann Arbor : ProQuest Dissertations & Theses, 2021 - 176 p.

Source: Dissertations Abstracts International, Volume: 83-01, Section: B.

Thesis (Ph.D.)--University of Alaska Fairbanks, 2021.

This item must not be sold to any third party vendors.

During late winter and spring in the Arctic, unique chemistry produces high levels of reactive bromine radicals (e.g., bromine atomic radicals and bromine monoxide, BrO) in the lower troposphere. These high levels of bromine radicals react with and reduce ambient ozone and oxidize gaseous elemental mercury. These reactive bromine species are chemically released from frozen saline surfaces and are affected by meteorological processes such as transport and mixing. Prior work has proposed that heterogenous reactions on snowpack surfaces as well as on atmospheric particle surfaces contribute to the reactive bromine production. We investigate these hypotheses using an extensive dataset of lower-tropospheric BrO observations from the Arctic Ocean and Utqiagvik (formerly Barrow). First, we combine BrO observations with meteorological data and use principal component analysis to determine what environmental processes are correlated with BrO. We find that increased levels of reactive bromine under two sets of meteorological conditions: 1) stable, poorly vertically mixed conditions with temperature inversions, and 2) low-atmospheric-pressure conditions with increased vertical mixing. A principal component regression model based on these correlations predicted both the vertical column density of BrO in the lowest 2 km of the troposphere (R = 0.45) and the vertical column density of BrO in the lowest 200 m (R = 0.54). Next, we compare BrO observations to a global chemical-transport model, GEOS-Chem, which was recently modified to add a blowing snow sea salt aerosol particle source. The GEOS-Chem model including the blowing snow process predicts monthly averaged BrO within experimental error for 9 of 13 total months of observations in Spring 2015 but cannot replicate hourly peaks in observed BrO. The model also predicts BrO during the Fall, which is not supported by the observations, potentially indicating a problem with the blowing snow model. We improve GEOS-Chem by adding a snowpack source of molecular bromine arising from deposition of precursor species such as ozone. Adding this snowpack molecular bromine source improves the agreement between the model and the observed monthly BrO at Utqiagvik. However, a prior literature form of this model that had assumed an increased daytime yield of molecular bromine due to photochemistry leads to overprediction of radical bromine and is not supported. We find that using both the blowing snow aerosol particle source and the snowpack molecular bromine source together in GEOS-Chem increases model skill in simulating Arctic reactive bromine events. Our global chemical model improvements should improve prediction of the effect of climate change on Arctic reactive bromine levels and help assess their implications for ozone depletion and mercury deposition.

ISBN: 9798535509600Subjects--Topical Terms:

544140
Atmospheric chemistry.
Subjects--Index Terms:

Arctic

Tropospheric Reactive Bromine and Meteorology over the Arctic Ocean.
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500 $a Source: Dissertations Abstracts International, Volume: 83-01, Section: B.
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520 $a During late winter and spring in the Arctic, unique chemistry produces high levels of reactive bromine radicals (e.g., bromine atomic radicals and bromine monoxide, BrO) in the lower troposphere. These high levels of bromine radicals react with and reduce ambient ozone and oxidize gaseous elemental mercury. These reactive bromine species are chemically released from frozen saline surfaces and are affected by meteorological processes such as transport and mixing. Prior work has proposed that heterogenous reactions on snowpack surfaces as well as on atmospheric particle surfaces contribute to the reactive bromine production. We investigate these hypotheses using an extensive dataset of lower-tropospheric BrO observations from the Arctic Ocean and Utqiagvik (formerly Barrow). First, we combine BrO observations with meteorological data and use principal component analysis to determine what environmental processes are correlated with BrO. We find that increased levels of reactive bromine under two sets of meteorological conditions: 1) stable, poorly vertically mixed conditions with temperature inversions, and 2) low-atmospheric-pressure conditions with increased vertical mixing. A principal component regression model based on these correlations predicted both the vertical column density of BrO in the lowest 2 km of the troposphere (R = 0.45) and the vertical column density of BrO in the lowest 200 m (R = 0.54). Next, we compare BrO observations to a global chemical-transport model, GEOS-Chem, which was recently modified to add a blowing snow sea salt aerosol particle source. The GEOS-Chem model including the blowing snow process predicts monthly averaged BrO within experimental error for 9 of 13 total months of observations in Spring 2015 but cannot replicate hourly peaks in observed BrO. The model also predicts BrO during the Fall, which is not supported by the observations, potentially indicating a problem with the blowing snow model. We improve GEOS-Chem by adding a snowpack source of molecular bromine arising from deposition of precursor species such as ozone. Adding this snowpack molecular bromine source improves the agreement between the model and the observed monthly BrO at Utqiagvik. However, a prior literature form of this model that had assumed an increased daytime yield of molecular bromine due to photochemistry leads to overprediction of radical bromine and is not supported. We find that using both the blowing snow aerosol particle source and the snowpack molecular bromine source together in GEOS-Chem increases model skill in simulating Arctic reactive bromine events. Our global chemical model improvements should improve prediction of the effect of climate change on Arctic reactive bromine levels and help assess their implications for ozone depletion and mercury deposition.
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