Trade-off between urban heat island mitigation and air quality in urban valleys

Henao, Juan J.; Rendón, Angela M.; Salazar, Juan F.

doi:10.1016/j.uclim.2019.100542

Cited by 47 publications

(12 citation statements)

References 76 publications

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“…However, competing feedbacks should be considered since green and cool roofs reduce wind speed and vertical mixing during the day, which might lead to air stagnation and air pollution situations [ 64 ]. Similarly, Henao et al [ 65 ] indicated that air pollution transport mechanisms in urban valleys could be altered by urban heat island mitigation and that air quality could worsen. In fact, Li et al [ 66 ] presented the “urban aerosol pollution island”, which is negatively correlated with the urban heat island in summer.…”

Section: Mesoscalementioning

confidence: 99%

Key Points in Air Pollution Meteorology

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García

Sánchez

et al. 2020

IJERPH

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Although emissions have a direct impact on air pollution, meteorological processes may influence inmission concentration, with the only way to control air pollution being through the rates emitted. This paper presents the close relationship between air pollution and meteorology following the scales of atmospheric motion. In macroscale, this review focuses on the synoptic pattern, since certain weather types are related to pollution episodes, with the determination of these weather types being the key point of these studies. The contrasting contribution of cold fronts is also presented, whilst mathematical models are seen to increase the analysis possibilities of pollution transport. In mesoscale, land–sea and mountain–valley breezes may reinforce certain pollution episodes, and recirculation processes are sometimes favoured by orographic features. The urban heat island is also considered, since the formation of mesovortices determines the entry of pollutants into the city. At the microscale, the influence of the boundary layer height and its evolution are evaluated; in particular, the contribution of the low-level jet to pollutant transport and dispersion. Local meteorological variables have a major influence on calculations with the Gaussian plume model, whilst some eddies are features exclusive to urban environments. Finally, the impact of air pollution on meteorology is briefly commented on.

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Section: Mesoscalementioning

confidence: 99%

Key Points in Air Pollution Meteorology

Pérez

García

Sánchez

et al. 2020

IJERPH

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“…However, under certain circumstances, vegetation can lead to adverse impacts in urban areas. UGI can impair ventilation through reduced airflow which impacts pollutant transport and dispersion leading to aggregation and consequently higher concentrations 18,19 . Moreover, plants emit highly reactive biogenic volatile organic compounds (BVOCs) which influence the urban atmospheric composition and can enhance near-a.…”

Section: Introductionmentioning

confidence: 99%

“…UGI can impair ventilation through reduced airflow which impacts pollutant transport and dispersion leading to aggregation and consequently higher concentrations. 18,19 Moreover, plants emit highly reactive biogenic volatile organic compounds (BVOCs) which influence the urban atmospheric composition and can enhance near-surface ozone (O 3 ) formation, as certain BVOCs are O 3 precursor substances. 10 Episodes with elevated ozone during summer are of specific interest since these are associated with exceedances of the World Health Organization (WHO) guideline concentration limits.…”

Section: Introductionmentioning

confidence: 99%

Analysis of the effect of abiotic stressors on BVOC emissions from urban green infrastructure in northern Germany

Feldner

Ramacher

Karl

et al. 2022

Environ. Sci.: Atmos.

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“…Measures that have been successfully applied to other cities may have inadvertent effects when applied to a different city, especially one with very different surroundings. For example, attempts to mitigate the urban heat island can interfere with the circulation patterns in complex terrain and have a detrimental effect on air quality (Henao et al, 2020). Numerical modelling is indispensable for investigating such effects, but if models are applied to areas where they have not been carefully evaluated, the output may be inaccurate and measures could be implemented that have unintended consequences or even act to exacerbate rather than ameliorate the situation.…”

Section: Introductionmentioning

confidence: 99%

Energy and mass exchange at an urban site in mountainous terrain – the Alpine city of Innsbruck

Ward

Rotach

Gohm

et al. 2022

Preprint

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Abstract. This study represents the first detailed analysis of multi-year near-surface turbulence observations for an urban area located in highly complex terrain. Using four years of eddy covariance measurements over the Alpine city of Innsbruck, Austria, the effects of the urban surface, orographic setting and mountain weather on energy and mass exchange are investigated. In terms of surface controls, findings for Innsbruck are in accordance with previous studies at city-centre sites. The available energy is partitioned mainly into net storage heat flux and sensible heat flux (each comprising about 40 % of the net radiation, Q*, during summer daytimes). The latent heat flux is small by comparison (only about 10 % of Q*) due to the small amount of vegetation present but increases for short periods (6–12 h) following rainfall. Additional energy supplied by anthropogenic activities and heat released from the large thermal mass of the urban surface helps to support positive sensible heat fluxes in the city all year round. Annual observed CO2 fluxes (5.1 kg C m−2 y−1) correspond well to both modelled emissions and expectations based on findings at other sites with a similar proportion of vegetation. The net CO2 exchange is dominated by anthropogenic emissions from traffic in summer and building heating in winter. In contrast to previous urban observational studies, the effect of the orography is examined here. Innsbruck’s location in a steep-sided valley results in marked diurnal and seasonal patterns in flow conditions. A typical valley-wind circulation is observed (in the absence of strong synoptic forcing) with moderate up-valley winds during daytime, weaker down-valley winds at night (and in winter) and near-zero wind speeds around the times of the twice-daily wind reversal. Due to Innsbruck’s location north of the main Alpine crest, south foehn events frequently have a marked effect on temperature, wind speed, turbulence and pollutant concentration. Warm, dry foehn air advected over the surface can lead to negative sensible heat fluxes both inside and outside the city. Increased wind speeds and intense mixing during foehn (turbulent kinetic energy often exceeds 5 m2 s−2) help to ventilate the city, illustrated here by low CO2 mixing ratio. Radiative exchange is also affected by the orography, for example incoming shortwave radiation is blocked by the terrain at low solar elevation. Interpretation of the dataset is complicated by distinct temporal patterns in flow conditions and the combined influences of the urban environment, terrain and atmospheric conditions. The analysis presented here reveals how Innsbruck’s mountainous setting impacts the near-surface conditions in multiple ways, highlighting the similarities with previous studies in much flatter terrain and examining the differences, in order to begin to understand interactions between urban and orographic processes.

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Trade-off between urban heat island mitigation and air quality in urban valleys

Cited by 47 publications

References 76 publications

Key Points in Air Pollution Meteorology

Key Points in Air Pollution Meteorology

Analysis of the effect of abiotic stressors on BVOC emissions from urban green infrastructure in northern Germany

Energy and mass exchange at an urban site in mountainous terrain – the Alpine city of Innsbruck

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