Long-Term Variation in Wintertime Atmospheric Diffusion Conditions Over the Sichuan Basin

Atmospheric diffusion is one of the factors affecting local air quality, dominating the evolution of air pollution episodes. Previous work has emphasized the unfavorable diffusion conditions in the Sichuan Basin resulting from its complex terrain. However, the recent spatiotemporal variation in atmo...

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Autores principales:	Guoyin Wang, Wennan Leng, Shaojing Jiang, Bangjun Cao
Formato:	article
Lenguaje:	EN
Publicado:	Frontiers Media S.A. 2021
Materias:	atmospheric diffusion ability ventilation coefficient atmospheric boundary layer air pollution Sichuan Basin Environmental sciences GE1-350
Acceso en línea:	https://doaj.org/article/77c327e5918640ecb2cd1b3b2eec753f
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spelling	oai:doaj.org-article:77c327e5918640ecb2cd1b3b2eec753f2021-11-10T09:15:58ZLong-Term Variation in Wintertime Atmospheric Diffusion Conditions Over the Sichuan Basin2296-665X10.3389/fenvs.2021.763504https://doaj.org/article/77c327e5918640ecb2cd1b3b2eec753f2021-11-01T00:00:00Zhttps://www.frontiersin.org/articles/10.3389/fenvs.2021.763504/fullhttps://doaj.org/toc/2296-665XAtmospheric diffusion is one of the factors affecting local air quality, dominating the evolution of air pollution episodes. Previous work has emphasized the unfavorable diffusion conditions in the Sichuan Basin resulting from its complex terrain. However, the recent spatiotemporal variation in atmospheric diffusion conditions in the basin and their effects on local air quality remain unclear. Based on the wind speed, boundary layer height, vertical potential temperature difference of ERA5 analysis, two independent metrics containing information on horizontal and vertical diffusion ability, i.e., ventilation coefficient (VE) and the air stagnant conditions (ASI), are involved to indicate wintertime atmospheric diffusion conditions in the basin. Both VE and ASI reveal a decrease tendency of atmospheric diffusion condition from the northwestern portion of the basin to the southeast. In terms of the long-term variation in diffusion conditions, VE showed a broader increasing trend from 1979 to 2019, with a distinct increase in the western region. In contrast, the occurrence of air stagnation events has declined −3∼−6%/decade in the basin, more significantly over the western basin. Both the increase in VE and the decrease in air stagnation frequency indicate the improvement of atmospheric diffusion conditions in the Sichuan Basin from 1979 to 2019, which mitigates the effects of air pollutant emissions to some extent. The enhancement of diffusion conditions is due to the improvement of vertical diffusion conditions. The lowest seasonal PM2.5 concentrations occur in the northwestern basin, where VE is highest and ASI is lowest. Atmospheric diffusion conditions can explain approximately 25–50% of the interannual variation in PM2.5 concentrations in Chengdu.Guoyin WangGuoyin WangWennan LengShaojing JiangBangjun CaoFrontiers Media S.A.articleatmospheric diffusion abilityventilation coefficientatmospheric boundary layerair pollutionSichuan BasinEnvironmental sciencesGE1-350ENFrontiers in Environmental Science, Vol 9 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	atmospheric diffusion ability ventilation coefficient atmospheric boundary layer air pollution Sichuan Basin Environmental sciences GE1-350
spellingShingle	atmospheric diffusion ability ventilation coefficient atmospheric boundary layer air pollution Sichuan Basin Environmental sciences GE1-350 Guoyin Wang Guoyin Wang Wennan Leng Shaojing Jiang Bangjun Cao Long-Term Variation in Wintertime Atmospheric Diffusion Conditions Over the Sichuan Basin
description	Atmospheric diffusion is one of the factors affecting local air quality, dominating the evolution of air pollution episodes. Previous work has emphasized the unfavorable diffusion conditions in the Sichuan Basin resulting from its complex terrain. However, the recent spatiotemporal variation in atmospheric diffusion conditions in the basin and their effects on local air quality remain unclear. Based on the wind speed, boundary layer height, vertical potential temperature difference of ERA5 analysis, two independent metrics containing information on horizontal and vertical diffusion ability, i.e., ventilation coefficient (VE) and the air stagnant conditions (ASI), are involved to indicate wintertime atmospheric diffusion conditions in the basin. Both VE and ASI reveal a decrease tendency of atmospheric diffusion condition from the northwestern portion of the basin to the southeast. In terms of the long-term variation in diffusion conditions, VE showed a broader increasing trend from 1979 to 2019, with a distinct increase in the western region. In contrast, the occurrence of air stagnation events has declined −3∼−6%/decade in the basin, more significantly over the western basin. Both the increase in VE and the decrease in air stagnation frequency indicate the improvement of atmospheric diffusion conditions in the Sichuan Basin from 1979 to 2019, which mitigates the effects of air pollutant emissions to some extent. The enhancement of diffusion conditions is due to the improvement of vertical diffusion conditions. The lowest seasonal PM2.5 concentrations occur in the northwestern basin, where VE is highest and ASI is lowest. Atmospheric diffusion conditions can explain approximately 25–50% of the interannual variation in PM2.5 concentrations in Chengdu.
format	article
author	Guoyin Wang Guoyin Wang Wennan Leng Shaojing Jiang Bangjun Cao
author_facet	Guoyin Wang Guoyin Wang Wennan Leng Shaojing Jiang Bangjun Cao
author_sort	Guoyin Wang
title	Long-Term Variation in Wintertime Atmospheric Diffusion Conditions Over the Sichuan Basin
title_short	Long-Term Variation in Wintertime Atmospheric Diffusion Conditions Over the Sichuan Basin
title_full	Long-Term Variation in Wintertime Atmospheric Diffusion Conditions Over the Sichuan Basin
title_fullStr	Long-Term Variation in Wintertime Atmospheric Diffusion Conditions Over the Sichuan Basin
title_full_unstemmed	Long-Term Variation in Wintertime Atmospheric Diffusion Conditions Over the Sichuan Basin
title_sort	long-term variation in wintertime atmospheric diffusion conditions over the sichuan basin
publisher	Frontiers Media S.A.
publishDate	2021
url	https://doaj.org/article/77c327e5918640ecb2cd1b3b2eec753f
work_keys_str_mv	AT guoyinwang longtermvariationinwintertimeatmosphericdiffusionconditionsoverthesichuanbasin AT guoyinwang longtermvariationinwintertimeatmosphericdiffusionconditionsoverthesichuanbasin AT wennanleng longtermvariationinwintertimeatmosphericdiffusionconditionsoverthesichuanbasin AT shaojingjiang longtermvariationinwintertimeatmosphericdiffusionconditionsoverthesichuanbasin AT bangjuncao longtermvariationinwintertimeatmosphericdiffusionconditionsoverthesichuanbasin
_version_	1718440207912534016

Long-Term Variation in Wintertime Atmospheric Diffusion Conditions Over the Sichuan Basin

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