气候变化领域集成服务门户(CCPortal): Urban canopy meteorological forcing and its impact on ozone and PM2.5: Role of vertical turbulent transport

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DOI	10.5194/acp-20-1977-2020
	Urban canopy meteorological forcing and its impact on ozone and PM2.5: Role of vertical turbulent transport
	Huszar P.; Karlický J.; Ďoubalová J.; Šindelářová K.; Nováková T.; Belda M.; Halenka T.; Žák M.; Pišoft P.
发表日期	2020
ISSN	16807316
起始页码	1977
结束页码	2016
卷号	20 期号:4
英文摘要	It is well known that the urban canopy (UC) layer, i.e., the layer of air corresponding to the assemblage of the buildings, roads, park, trees and other objects typical to cities, is characterized by specific meteorological conditions at city scales generally differing from those over rural surroundings. We refer to the forcing that acts on the meteorological variables over urbanized areas as the urban canopy meteorological forcing (UCMF). UCMF has multiple aspects, while one of the most studied is the generation of the urban heat island (UHI) as an excess of heat due to increased absorption and trapping of radiation in street canyons. However, enhanced drag plays important role too, reducing mean wind speeds and increasing vertical eddy mixing of pollutants. As air quality is strongly tied to meteorological conditions, the UCMF leads to modifications of air chemistry and transport of pollutants. Although it has been recognized in the last decade that the enhanced vertical mixing has a dominant role in the impact of the UCMF on air quality, very little is known about the uncertainty of vertical eddy diffusion arising from different representation in numerical models and how this uncertainty propagates to the final species concentrations as well as to the changes due to the UCMF. To bridge this knowledge gap, we set up the Regional Climate Model version 4 (RegCM4) coupled to the Comprehensive Air Quality Model with Extensions (CAMx) chemistry transport model over central Europe and designed a series of simulations to study how UC affects the vertical turbulent transport of selected pollutants through modifications of the vertical eddy diffusion coefficient (Kv) using six different methods for Kv calculation. The mean concentrations of ozone and PM2.5 in selected city canopies are analyzed. These are secondary pollutants or having secondary components, upon which turbulence acts in a much more complicated way than in the case of primary pollutants by influencing their concentrations not only directly but indirectly via precursors too. Calculations are performed over cascading domains (of 27, 9, and 3km horizontal resolutions), which further enables to analyze the sensitivity of the numerical model to grid resolution. A number of model simulations are carried out where either urban canopies are considered or replaced by rural ones in order to isolate the UC meteorological forcing. Apart from the well-pronounced and expected impact on temperature (increases up to 2°C) and wind (decreases by up to 2ms-1), there is a strong impact on vertical eddy diffusion in all of the six Kv methods. The Kv enhancement ranges from less than 1 up to 3m2 s-1 at the surface and from 1 to 10m2 s-1 at higher levels depending on the methods. The largest impact is obtained for the turbulent kinetic energy (TKE)-based methods. The range of impact on the vertical eddy diffusion coefficient propagates to a range of ozone (O3) increase of 0.4 to 4ppbv in both summer and winter (5%-1% relative change). In the case of PM2.5, we obtained decreases of up to 1μg m-3 in summer and up to 2μg m-3 in winter (up to 3%-4% relative change). Comparing these results to the "total-impact", i.e., to the impact of all meteorological modifications due to UCMF, we can conclude that much of UCMF is explained by the enhanced vertical eddy diffusion, which counterbalances the opposing effects of other components of this forcing (temperature, humidity and wind). The results further show that this conclusion holds regardless of the resolution chosen and in both the warm and cold parts of the year. © 2020 Copernicus GmbH. All rights reserved.
关键词	air quality atmospheric chemistry atmospheric forcing canopy climate modeling heat island ozone particulate matter pollutant transport street canyon turbulent flow urban atmosphere
语种	英语
来源机构	Atmospheric Chemistry and Physics
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/132227
推荐引用方式 GB/T 7714	Huszar P.,Karlický J.,Ďoubalová J.,et al. Urban canopy meteorological forcing and its impact on ozone and PM2.5: Role of vertical turbulent transport[J]. Atmospheric Chemistry and Physics,2020,20(4).
APA	Huszar P..,Karlický J..,Ďoubalová J..,Šindelářová K..,Nováková T..,...&Pišoft P..(2020).Urban canopy meteorological forcing and its impact on ozone and PM2.5: Role of vertical turbulent transport.,20(4).
MLA	Huszar P.,et al."Urban canopy meteorological forcing and its impact on ozone and PM2.5: Role of vertical turbulent transport".20.4(2020).