Evolution of the urban aerosol during winter temperature inversion episodes

Janhäll, Sara; Olofson, K. Frans G.; Andersson, Patrik; Pettersson, Jan B. C.; Hallquist, Mattias

doi:10.1016/j.atmosenv.2006.04.051

Cited by 93 publications

(54 citation statements)

References 41 publications

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“…This suggests that the peaks of CO mixing ratio observe in the early morning were due to rapid increase and accumulation of emissions of CO while there was still little convection, before stronger mixing started later in the morning. Similar observations have been previously reported (Janhäll et al, 2006;Hu et al, 2009;Durant et al, 2010). In the afternoon on weekdays, when the traffic volume was still high, the CO mixing ratio dropped significantly, compared to early morning rush hour.…”

Section: Average Diurnal Cyclessupporting

confidence: 81%

Long-path measurements of pollutants and micrometeorology over Highway 401 in Toronto

et al. 2017

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Abstract. Traffic emissions contribute significantly to urban air pollution. Measurements were conducted over Highway 401 in Toronto, Canada, with a long-path Fourier transform infrared (FTIR) spectrometer combined with a suite of micrometeorological instruments to identify and quantify a range of air pollutants. Results were compared with simultaneous in situ observations at a roadside monitoring station, and with output from a special version of the operational Canadian air quality forecast model (GEM-MACH). Elevated mixing ratios of ammonia (0-23 ppb) were observed, of which 76 % were associated with traffic emissions. Hydrogen cyanide was identified at mixing ratios between 0 and 4 ppb. Using a simple dispersion model, an integrated emission factor of on average 2.6 g km −1 carbon monoxide was calculated for this defined section of Highway 401, which agreed well with estimates based on vehicular emission factors and observed traffic volumes. Based on the same dispersion calculations, vehicular average emission factors of 0.04, 0.36, and 0.15 g km −1 were calculated for ammonia, nitrogen oxide, and methanol, respectively.

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Section: Average Diurnal Cyclessupporting

confidence: 81%

Long-path measurements of pollutants and micrometeorology over Highway 401 in Toronto

et al. 2017

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“…Additionally, many case studies of air pollution episodes also stress the importance of temperature inversions (e.g. Kukkonen et al, 2005;Janhall et al, 2006). This work provides extra information, as it shows that the ability of inversions to trap the pollutants below the capping inversion strongly depends on the prevailing weather, and expresses this dependence quantitatively.…”

Section: Resultsmentioning

confidence: 99%

The effect of the prevailing weather on the statistics of atmospheric temperature inversions

Milionis

Davies

2007

Intl Journal of Climatology

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ABSTRACT:The unanimously accepted dependence of the static stability of the lower troposphere on the prevailing weather has, so far, not been expressed quantitatively. This work is the first systematic attempt at expressing this dependence quantitatively. Two weather classifications, an index expressing the activity of the atmospheric temperature inversion layers, and various other inversion statistics are considered for this purpose. Radiosonde data from Hemsby (UK) are used. Lamb's weather classification, which is used initially, shows clear differences in the statistics of inversions for different weather classes. The anticyclonic class is associated with the maximum activity, and the cyclonic class with the minimum activity. The weather class is also shown to affect the vertical variation of the activity of inversions. Differences in the activity of inversions due to the weather class are maximized in the layer 900-800 mb. Given that it is within this layer where the top of the atmospheric boundary layer is usually found, this result is of particular importance for air pollution modelling. An alternative weather classification is also used with the objective of associating inversion statistics not just to a particular weather type, but also to the physical reasons that are responsible for their formation. This classification shows that, in the absence of an anticyclone, the activity of inversions is rather independent of the prevailing weather pattern. However, when the anticyclonic category is also included, the differences become significant. As the results of this work express quantitatively the strong dependence of inversion statistics on the prevailing weather, they can be used for the creation of correction factors for many characteristics related to an inversion climatology (e.g. for the annual cycle of the activity of inversions). Such corrections are necessary in cases where the weather types in the study period do not reflect their frequency in the average climate.

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“…To our knowledge there are no studies where remotely sensed profiles of urban turbulence were taken simultaneously with aerosol size distributions measured at different altitudes. Janhäll et al (2006) follow the break-up of the overnight inversion, but did not link that directly with particle size distributions measured at different heights. The objective of the present paper is to report spatial variations in particles emitted from traffic and to observe the evolution of size distributions with distance and time by taking measurements simultaneously at three sites within the urban area of London.…”

Section: Introductionmentioning

confidence: 99%

Remarkable dynamics of nanoparticles in the urban atmosphere

et al. 2011

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Abstract. Nanoparticles emitted from road traffic are the largest source of respiratory exposure for the general public living in urban areas. It has been suggested that adverse health effects of airborne particles may scale with airborne particle number, which if correct, focuses attention on the nanoparticle (less than 100 nm) size range which dominates the number count in urban areas. Urban measurements of particle size distributions have tended to show a broadly similar pattern dominated by a mode centred on 20-30 nm diameter emitted by diesel engine exhaust. In this paper we report the results of measurements of particle number concentration and size distribution made in a major London park as well as on the BT Tower, 160 m aloft. These measurements taken during the REPARTEE project (Regents Park and BT Tower experiment) show a remarkable shift in particle size distributions with major losses of the smallest particle class as particles are advected away from the traffic source. In the Park, the traffic related mode at 20-30 nm diameter is much reduced with a new mode at <10 nm. Size distribution measurements also revealed higher number concentrations of sub-50 nm particles at the BT Tower during days affected by higher turbulence as determined by Doppler Lidar measurements and are indicative of loss of nanoparticles from air aged during less turbulent conditions. These results are suggestive of nanoparticle loss by evaporation, rather than coagulation processes. The results have major implications for understanding the impacts of traffic-generated particulate matter on human health.

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Evolution of the urban aerosol during winter temperature inversion episodes

Cited by 93 publications

References 41 publications

Long-path measurements of pollutants and micrometeorology over Highway 401 in Toronto

Long-path measurements of pollutants and micrometeorology over Highway 401 in Toronto

The effect of the prevailing weather on the statistics of atmospheric temperature inversions

Remarkable dynamics of nanoparticles in the urban atmosphere

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