Modelling the impact of megacities on local, regional and global tropospheric ozone and the deposition of nitrogen species

Stock, Z. S.; Russo, M. R.; Butler, Tim; Archibald, Alexander T.; Lawrence, M. G.; Telford, P.; Abraham, N. L.; Pyle, J. A.

doi:10.5194/acp-13-12215-2013

Cited by 26 publications

(20 citation statements)

References 67 publications

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“…There have also been model-based efforts to estimate the fingerprints of cities on the atmospheric chemistry across multiple scales. On the global scale, Lawrence et al (2007), Butler and Lawrence (2009), Folberth et al (2010), Butler et al (2012) and Stock et al (2013) gave estimates of the emission impacts on the environment. On regional scales, many studies focused on European urban centres (e.g.…”

Section: Introductionmentioning

confidence: 99%

The regional impact of urban emissions on climate over central Europe: present and future emission perspectives

et al. 2016

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Abstract. The regional climate model RegCM4.2 was coupled to the chemistry transport model CAMx, including twoway interactions, to evaluate the regional impact of urban emission from central European cities on climate for presentday (2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010) and future (2046)(2047)(2048)(2049)(2050)(2051)(2052)(2053)(2054)(2055) periods, and for the future one only emission changes are considered. Short-lived non-CO 2 emissions are considered and, for the future impact, only the emission changes are accounted for (the climate is kept "fixed"). The urban impact on climate is calculated with the annihilation approach in which two experiments are performed: one with all emissions included and one without urban emissions. The radiative impacts of non-CO 2 primary and secondary formed pollutants are considered, namely ozone (O 3 ), sulfates (PSO 4 ), nitrates (PNO 3 ), primary organic aerosol and primary elementary carbon (POA and PEC).The validation of the modelling system is limited to key climate parameters, near-surface temperature and precipitation. It shows that the model, in general, underestimates temperature and overestimates precipitation. We attribute this behaviour to an excess of cloudiness/water vapour present in the model atmosphere as a consequence of overpredicted evaporation from the surface.The impact on climate is characterised by statistically significant cooling of up to −0.02 and −0.04 K in winter (DJF) and summer (JJA), mainly over cities. We found that the main contributors to the cooling are the direct and indirect effects of the aerosols, while the ozone titration, calculated especially for DJF, plays rather a minor role. In accordance with the vertical extent of the urban-emission-induced aerosol perturbation, cooling dominates the first few model layers up to about 150 m in DJF and 1000 m in JJA. We found a clear diurnal cycle of the radiative impacts with maximum cooling just after noon (JJA) or later in afternoon (DJF). Furthermore, statistically significant decreases of surface radiation are modelled in accordance with the temperature decrease. The impact on the boundary layer height is small but statistically significant and decreases by 1 and 6 m in DJF and JJA respectively. We did not find any statistically significant impact on precipitation and wind speed. Regarding future emissions, the impacts are, in general, smaller as a consequence of smaller emissions, resulting in smaller urban-induced chemical perturbations.In overall, the study suggest that the non-CO 2 emissions play rather a minor role in modulating regional climate over central Europe. Much more important is the direct climate impact of urban surfaces via the urban canopy meteorological effects as we showed earlier.

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Section: Introductionmentioning

confidence: 99%

The regional impact of urban emissions on climate over central Europe: present and future emission perspectives

et al. 2016

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“…Considering ozone concentrations as a relative contribution to the global scale, megacities contribute a small amount to global ozone (Stock et al, 2013). In a model "annihilation" experiment where the emissions from grid cells containing megacities were removed, emissions from megacities contributed only 0.84 % to the global average tropospheric ozone column density, proportionally smaller than the 6 % of global anthropogenic ozone precursor emissions from megacities (Butler et al, 2012).…”

Section: Megacitiesmentioning

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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“…Other comparisons note that tagging is more appropriate for source attribution than for estimating responses to emissions changes (e.g., Collet et al, 2014). In cases strongly affected by nonlinearities of O 3 formation, the choice of source estimation method can lead to considerable differences (Grewe et al, 2010;Stock et al, 2013;Lapina et al, 2014;Emmons et al, 2012). Parrish et al (2017a) noted that the running average ODVs for sites in Southern California over the past 4 decades can be fit to a simple exponential decay function.…”

Section: Approaches Used To Quantify Usb and Nab Omentioning

confidence: 99%

Scientific assessment of background ozone over the U.S.: Implications for air quality management

Jaffe

Cooper

Fiore

et al. 2018

Elementa: Science of the Anthropocene

109

149

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Ozone (O3) is a key air pollutant that is produced from precursor emissions and has adverse impacts on human health and ecosystems. In the U.S., the Clean Air Act (CAA) regulates O3levels to protect public health and welfare, but unraveling the origins of surface O3is complicated by the presence of contributions from multiple sources including background sources like stratospheric transport, wildfires, biogenic precursors, and international anthropogenic pollution, in addition to U.S. anthropogenic sources. In this report, we consider more than 100 published studies and assess current knowledge on the spatial and temporal distribution, trends, and sources of background O3over the continental U.S., and evaluate how it influences attainment of the air quality standards. We conclude that spring and summer seasonal mean U.S. background O3(USB O3), or O3formed from natural sources plus anthropogenic sources in countries outside the U.S., is greatest at high elevation locations in the western U.S., with monthly mean maximum daily 8-hour average (MDA8) mole fractions approaching 50 parts per billion (ppb) and annual 4thhighest MDA8s exceeding 60 ppb, at some locations. At lower elevation sites, e.g., along the West and East Coasts, seasonal mean MDA8 USB O3is in the range of 20–40 ppb, with generally smaller contributions on the highest O3days. The uncertainty in U.S. background O3is around ±10 ppb for seasonal mean values and higher for individual days. Noncontrollable O3sources, such as stratospheric intrusions or precursors from wildfires, can make significant contributions to O3on some days, but it is challenging to quantify accurately these contributions. We recommend enhanced routine observations, focused field studies, process-oriented modeling studies, and greater emphasis on the complex photochemistry in smoke plumes as key steps to reduce the uncertainty associated with background O3in the U.S.

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Modelling the impact of megacities on local, regional and global tropospheric ozone and the deposition of nitrogen species

Cited by 26 publications

References 67 publications

The regional impact of urban emissions on climate over central Europe: present and future emission perspectives

The regional impact of urban emissions on climate over central Europe: present and future emission perspectives

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

Scientific assessment of background ozone over the U.S.: Implications for air quality management

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