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Article: Vertical Gradient Variations in Radiation Budget and Heat Fluxes in the Urban Boundary Layer: A Comparison Study Between Polluted and Clean Air Episodes in Beijing During Winter

TitleVertical Gradient Variations in Radiation Budget and Heat Fluxes in the Urban Boundary Layer: A Comparison Study Between Polluted and Clean Air Episodes in Beijing During Winter
Authors
Keywordsaerosol
air pollution
energy budget
radiation budget
Issue Date2020
PublisherAmerican Geophysical Union, co-published with Wiley. The Journal's web site is located at http://agupubs.onlinelibrary.wiley.com/agu/jgr/journal/10.1002/%28ISSN%292169-8996/
Citation
Journal of Geophysical Research: Atmospheres, 2020, v. 125 n. 14, p. article no. e2020JD032478 How to Cite?
AbstractPrevious studies have reported air pollution‐radiation interactions in the urban boundary layer (UBL), but vertical gradient variations in the radiation budget and heat flux under air pollution conditions are relatively sparse. In this study, based on gradient observations from the Beijing 325 m meteorological tower in December 2015, the characteristics of near‐surface radiation balance and energy budget at three levels under different pollution conditions were comparatively investigated. Relative to clean days, both downward and upward shortwave radiation (DSR and USR) dropped during daytime, while downward and upward longwave radiation (DLR and ULR) enhanced during nighttime on heavily polluted days, showing that with evaluated height, the drop magnitudes of DSR and USR decreased, while the enhancement magnitude of DLR (ULR) decreased (increased). The combined effects of four radiation components significantly induced the reduction in net radiation (R n ) on polluted days, leading to the near‐surface energy budget change. In addition, the monthly averaged anthropogenic heat flux (Q f ) was estimated to quantitatively calculate the heat storage (G ) term in the surface energy budget. During daytime, compared to the clean episodes, the sensible heat flux (H ) was reduced more than R n in the whole near‐surface UBL during heavy polluted episodes, resulting in smaller H /(R n + Q f ) and larger G /(R n + Q f ). Finally, we revealed that weak thermal forcing effects caused by insufficient availability of net radiation energy at the surface and weak dynamic motion associated with weak winds were both responsible for the larger reduction (increase) in H (G ) during pollution episodes in the whole near‐surface UBL.
Persistent Identifierhttp://hdl.handle.net/10722/284726
ISSN
2019 Impact Factor: 3.821

 

DC FieldValueLanguage
dc.contributor.authorWang, L-
dc.contributor.authorFan, S-
dc.contributor.authorHu, F-
dc.contributor.authorMiao, S-
dc.contributor.authorYang, A-
dc.contributor.authorLi, Y-
dc.contributor.authorLiu, J-
dc.contributor.authorLiu, C-
dc.contributor.authorChen, S-
dc.contributor.authorHo, HC-
dc.contributor.authorDuan, Z-
dc.contributor.authorGao, Z-
dc.contributor.authorYang, Y-
dc.date.accessioned2020-08-07T09:01:49Z-
dc.date.available2020-08-07T09:01:49Z-
dc.date.issued2020-
dc.identifier.citationJournal of Geophysical Research: Atmospheres, 2020, v. 125 n. 14, p. article no. e2020JD032478-
dc.identifier.issn2169-897X-
dc.identifier.urihttp://hdl.handle.net/10722/284726-
dc.description.abstractPrevious studies have reported air pollution‐radiation interactions in the urban boundary layer (UBL), but vertical gradient variations in the radiation budget and heat flux under air pollution conditions are relatively sparse. In this study, based on gradient observations from the Beijing 325 m meteorological tower in December 2015, the characteristics of near‐surface radiation balance and energy budget at three levels under different pollution conditions were comparatively investigated. Relative to clean days, both downward and upward shortwave radiation (DSR and USR) dropped during daytime, while downward and upward longwave radiation (DLR and ULR) enhanced during nighttime on heavily polluted days, showing that with evaluated height, the drop magnitudes of DSR and USR decreased, while the enhancement magnitude of DLR (ULR) decreased (increased). The combined effects of four radiation components significantly induced the reduction in net radiation (R n ) on polluted days, leading to the near‐surface energy budget change. In addition, the monthly averaged anthropogenic heat flux (Q f ) was estimated to quantitatively calculate the heat storage (G ) term in the surface energy budget. During daytime, compared to the clean episodes, the sensible heat flux (H ) was reduced more than R n in the whole near‐surface UBL during heavy polluted episodes, resulting in smaller H /(R n + Q f ) and larger G /(R n + Q f ). Finally, we revealed that weak thermal forcing effects caused by insufficient availability of net radiation energy at the surface and weak dynamic motion associated with weak winds were both responsible for the larger reduction (increase) in H (G ) during pollution episodes in the whole near‐surface UBL.-
dc.languageeng-
dc.publisherAmerican Geophysical Union, co-published with Wiley. The Journal's web site is located at http://agupubs.onlinelibrary.wiley.com/agu/jgr/journal/10.1002/%28ISSN%292169-8996/-
dc.relation.ispartofJournal of Geophysical Research: Atmospheres-
dc.rightsJournal of Geophysical Research: Atmospheres. Copyright © American Geophysical Union, co-published with Wiley.-
dc.rights©[2020]. American Geophysical Union. All Rights Reserved. This article is available at https://doi.org/10.1029/2020JD032478-
dc.subjectaerosol-
dc.subjectair pollution-
dc.subjectenergy budget-
dc.subjectradiation budget-
dc.titleVertical Gradient Variations in Radiation Budget and Heat Fluxes in the Urban Boundary Layer: A Comparison Study Between Polluted and Clean Air Episodes in Beijing During Winter-
dc.typeArticle-
dc.identifier.emailHo, HC: hcho21@hku.hk-
dc.identifier.authorityHo, HC=rp02482-
dc.description.naturepublished_or_final_version-
dc.description.naturelink_to_subscribed_fulltext-
dc.identifier.doi10.1029/2020JD032478-
dc.identifier.scopuseid_2-s2.0-85088563337-
dc.identifier.hkuros312105-
dc.identifier.volume125-
dc.identifier.issue14-
dc.identifier.spagearticle no. e2020JD032478-
dc.identifier.epagearticle no. e2020JD032478-
dc.publisher.placeUnited States-

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