Impacts of Asian megacity emissions on regional air quality during spring 2001

Guttikunda, Sarath; Tang, Youhua; Carmichael, Gregory R.; Kurata, Gakuji; Pan, Li; Streets, David G.; Woo, Jung‐Hun; Thongboonchoo, Narisara; Fried, Alan

doi:10.1029/2004jd004921

Cited by 92 publications

(53 citation statements)

References 18 publications

(32 reference statements)

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“…In a sense there is an urban decrement driven by this process. Conversely, there has been some work looking at megacity impacts on regional ozone (Tie et al, 2013;Beirle et al, 2011;Guttikunda et al, 2005) (see also Sect. 4.1).…”

Section: Atmosmentioning

confidence: 99%

Tropospheric ozone and its precursors from the urban to the global scale from air quality to short-lived climate forcer

et al. 2015

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Abstract. Ozone holds a certain fascination in atmospheric science. It is ubiquitous in the atmosphere, central to tropospheric oxidation chemistry, yet harmful to human and ecosystem health as well as being an important greenhouse gas. It is not emitted into the atmosphere but is a byproduct of the very oxidation chemistry it largely initiates. Much effort is focused on the reduction of surface levels of ozone owing to its health and vegetation impacts, but recent efforts to achieve reductions in exposure at a country scale have proved difficult to achieve owing to increases in background ozone at the zonal hemispheric scale. There is also a growing realisation that the role of ozone as a short-lived climate pollutant could be important in integrated air quality climate change mitigation. This review examines current understanding of the processes regulating tropospheric ozone at global to local scales from both measurements and models. It takes the view that knowledge across the scales is important for dealing with air quality and climate change in a synergistic manner. The review shows that there remain a number of clear challenges for ozone such as explaining surface trends, incorporating new chemical understanding, ozone-climate coupling, and a better assessment of impacts. There is a clear and present need to treat ozone across the range of scales, a transboundary issue, but with an emphasis on the hemispheric scales. New observational opportunities are offered both by satellites and small sensors that bridge the scales.

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Section: Atmosmentioning

confidence: 99%

Tropospheric ozone and its precursors from the urban to the global scale from air quality to short-lived climate forcer

et al. 2015

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“…Im and Kanakidou (2012) found for Athens and Istanbul an even larger contribution around 95-96 % over these cities. Earlier, Guttikunda et al (2005) calculated the eastern Asia megacities contribution to NO z levels and found values around 10-30 % over cities, however NO z contains species produced during plume aging further from city centers causing this lower contribution.…”

Section: The Urban Emissions Impact On Air Qualitymentioning

confidence: 99%

On the long-term impact of emissions from central European cities on regional air quality

2016

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Abstract. For the purpose of qualifying and quantifying the impact of urban emission from Central European cities on the present-day regional air quality, the regional climate model RegCM4.2 was coupled with the chemistry transport model CAMx, including two-way interactions. A series of simulations was carried out for the 2001-2010 period either with all urban emissions included (base case) or without considering urban emissions. Further, the sensitivity of ozone production to urban emissions was examined by performing reduction experiments with −20 % emission perturbation of NO x and/or non-methane volatile organic compounds (NMVOC).The modeling system's air quality related outputs were evaluated using AirBase, and EMEP surface measurements showed reasonable reproduction of the monthly variation for ozone (O 3 ), but the annual cycle of nitrogen dioxide (NO 2 ) and sulfur dioxide (SO 2 ) is more biased. In terms of hourly correlations, values achieved for ozone and NO 2 are 0.5-0.8 and 0.4-0.6, but SO 2 is poorly or not correlated at all with measurements (r around 0.2-0.5). The modeled fine particulates (PM 2.5 ) are usually underestimated, especially in winter, mainly due to underestimation of nitrates and carbonaceous aerosols.European air quality measures were chosen as metrics describing the cities emission impact on regional air pollution. Due to urban emissions, significant ozone titration occurs over cities while over rural areas remote from cities, ozone production is modeled, mainly in terms of number of exceedances and accumulated exceedances over the threshold of 40 ppbv. Urban NO x , SO 2 and PM 2.5 emissions also significantly contribute to concentrations in the cities themselves (up to 50-70 % for NO x and SO 2 , and up to 60 % for PM 2.5 ), but the contribution is large over rural areas as well (10-20 %). Although air pollution over cities is largely determined by the local urban emissions, considerable (often a few tens of %) fraction of the concentration is attributable to other sources from rural areas and minor cities. For the case of Prague (Czech Republic capital), it is further shown that the inter-urban interference between large cities does not play an important role which means that the impact on a chosen city of emissions from all other large cities is very small. At last, it is shown that to achieve significant ozone reduction over cities in central Europe, the emission control strategies have to focus on the reduction of NMVOC, as reducing NO x (due to suppressed titration) often leads to increased O 3 . The influence over rural areas is however always in favor of improved air quality, i.e. both NO x and/or NMVOC reduction ends up in decreased ozone pollution, mainly in terms of exceedances.

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“…Another way to asses the influence of megacities is by examining their chemical 'footprint'. Similarly to previous work, [22] we calculate the area of the Earth's surface over which the surface mixing ratio or concentration of various chemical species is increased by more than 10%. The threshold of 10% is chosen because the megacities themselves account for ∼10% of the Earth's population.…”

Section: Global Effectsmentioning

confidence: 99%

The influence of megacities on global atmospheric chemistry: a modelling study

Butler

Lawrence

2009

Environ. Chem.

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Environmental context. Over half of the population of the world now live in urban areas, and the number of so-called 'megacities', with populations of ∼10 million or more, is growing at a tremendous rate. We show how these patterns of urbanisation have the potential to influence the atmospheric chemical environment on a global scale, particularly through the effects of emissions from megacities on the reactive nitrogen cycle. With the growing worldwide interest in the study of the effects of megacities at all spatial scales, such as current European Union projects MEGAPOLI and CityZen, our study represents the first of many future studies that examine the effects of megacities on atmospheric chemistry on the global scale.Abstract. We present the first study of the effects of megacities on global atmospheric chemistry using a global threedimensional chemical transport model. The effects on air quality, radiative forcing and atmospheric oxidation capacity are disproportionately smaller than the proportion of anthropogenic emissions due to megacities. Disproportionately large effects of megacities are modelled for reactive nitrogen compounds, in particular PAN (peroxy acetyl nitrate), which has increased in abundance globally by 9% due to megacities under year 2000 conditions, with 23% of the Earth experiencing an increase of 10% or more. These influences decrease under two very different future emission scenarios. Under a low-emission future scenario, the influence of megacities is generally reduced, and under a high-emission future scenario, although the local influence of megacities is increased, the geographical extent of the influence becomes smaller. In our model, the individual grid cells that contain megacities respond to the megacity emissions differently depending on their latitude. Tropical megacity grid cells generally show increased ozone year-round, while northern extratropical megacities generally show reduced ozone year-round. Better parameterisation of the sub-grid effects of megacities is an important issue for future work.

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Impacts of Asian megacity emissions on regional air quality during spring 2001

Cited by 92 publications

References 18 publications

Tropospheric ozone and its precursors from the urban to the global scale from air quality to short-lived climate forcer

Tropospheric ozone and its precursors from the urban to the global scale from air quality to short-lived climate forcer

On the long-term impact of emissions from central European cities on regional air quality

The influence of megacities on global atmospheric chemistry: a modelling study

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