Boundary Layers and Air Quality in Mountainous Terrain

Steyn, D. G.; Wekker, Stephan F. J. De; Koßmann, M.; Martilli, Alberto

doi:10.1007/978-94-007-4098-3_5

Cited by 30 publications

(35 citation statements)

References 81 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Increased local knowledge and general understanding of the relevant processes (e.g. Glazunov et al, 2016) can then help the forecasters to improve air quality predictions based on NWP models, as suggested by Steyn et al (2013).…”

mentioning

confidence: 99%

“…Wolf-Grosse et al: A large-eddy simulation study areas, this can be caused either by a local circulation trapping the pollutants or by local stagnation within the surrounding mountains (Rotach et al, 2004;Steyn et al, 2013). The most prominent examples of such local stagnation are typically observed in stably stratified cold air pools trapped in valleys and other orographic depressions (e.g.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Sensitivity of local air quality to the interplay between small- and large-scale circulations: a large-eddy simulation study

Wolf¹,

Esau²,

Reuder

2017

Atmos. Chem. Phys.

View full text Add to dashboard Cite

Abstract. Street-level urban air pollution is a challenging concern for modern urban societies. Pollution dispersion models assume that the concentrations decrease monotonically with raising wind speed. This convenient assumption breaks down when applied to flows with local recirculations such as those found in topographically complex coastal areas. This study looks at a practically important and sufficiently common case of air pollution in a coastal valley city. Here, the observed concentrations are determined by the interaction between large-scale topographically forced and local-scale breeze-like recirculations.Analysis of a long observational dataset in Bergen, Norway, revealed that the most extreme cases of recurring wintertime air pollution episodes were accompanied by increased large-scale wind speeds above the valley. Contrary to the theoretical assumption and intuitive expectations, the maximum NO 2 concentrations were not found for the lowest 10 m ERA-Interim wind speeds but in situations with wind speeds of 3 m s −1 . To explain this phenomenon, we investigated empirical relationships between the large-scale forcing and the local wind and air quality parameters. We conducted 16 large-eddy simulation (LES) experiments with the Parallelised Large-Eddy Simulation Model (PALM) for atmospheric and oceanic flows. The LES accounted for the realistic relief and coastal configuration as well as for the large-scale forcing and local surface condition heterogeneity in Bergen. They revealed that emerging local breeze-like circulations strongly enhance the urban ventilation and dispersion of the air pollutants in situations with weak largescale winds. Slightly stronger large-scale winds, however, can counteract these local recirculations, leading to enhanced surface air stagnation.Furthermore, this study looks at the concrete impact of the relative configuration of warmer water bodies in the city and the major transport corridor. We found that a relatively small local water body acted as a barrier for the horizontal transport of air pollutants from the largest street in the valley and along the valley bottom, transporting them vertically instead and hence diluting them. We found that the stable stratification accumulates the street-level pollution from the transport corridor in shallow air pockets near the surface. The polluted air pockets are transported by the local recirculations to other less polluted areas with only slow dilution. This combination of relatively long distance and complex transport paths together with weak dispersion is not sufficiently resolved in classical air pollution models. The findings have important implications for the air quality predictions over urban areas. Any prediction not resolving these, or similar local dynamic features, might not be able to correctly simulate the dispersion of pollutants in cities.

show abstract

mentioning

confidence: 99%

mentioning

confidence: 99%

Sensitivity of local air quality to the interplay between small- and large-scale circulations: a large-eddy simulation study

Wolf¹,

Esau²,

Reuder

2017

Atmos. Chem. Phys.

View full text Add to dashboard Cite

show abstract

“…The paucity of studies is partly linked to the lack of observations in the Andean region and also to the difficulties rising from the complex interactions between the airflow and the underlying surface over complex terrain [Steyn et al, 2013].…”

Section: 1002/2015ef000311mentioning

confidence: 99%

“…The detailed distribution, timing, and intensity of the wind are, however, much less explored in the Andes. Of particular interest are the differences in the airflow channeled by the narrow valleys by comparison to those that develop over more open terrain [Steyn et al, 2013]. The complex topography of the region is illustrated in Figure 1.…”

Section: The Climate Of the Andean Regionmentioning

confidence: 99%

Pollution and its Impacts on the South American Cryosphere

et al. 2015

View full text Add to dashboard Cite

This article is a review of the science goals and activities initiated within the framework of the Pollution and its Impacts on the South American Cryosphere (PISAC) initiative. Air pollution associated with biomass burning and urban emissions affects extensive areas of South America. We focus on black carbon (BC) aerosol and its impacts on air quality, water availability, and climate, with an emphasis on the Andean cryosphere. BC is one of the key short-lived climate pollutants that is a topic of growing interest for near-term mitigation of these issues. Limited scientific evidence indicates that the Andean cryosphere has already responded to climate change with receding glaciers and snow cover, which directly affect water resources, agriculture, and energy production in the Andean region of South America. Despite the paucity of systematic observations along the Andes, a few studies have detected BC on snow and glaciers in the Andes. These, in addition to existing and projected emissions and weather patterns, suggest a possible contribution of BC to the observed retreat of the Andean cryosphere. Here we provide an overview of the current understanding of these issues from scientific and policy perspectives, and propose strategic expansions to the relevant measurement infrastructure in the region.

show abstract

“…From this perspective, the alpine environment is unique in the world, being a cross between continental Europe and the Mediterranean basin, a key region for the assessment of climate change (Giorgi and Lionello 2008). Furthermore, mountain sites are subject to various and intricate weather patterns, such as mountain-valley breezes, temperature inversions, Föhn winds, advection of air masses from neighboring polluted basins, all of which also influence the aerosol concentration, especially in the lowest layers of the atmosphere (Steyn et al 2013). Finally, even low aerosol optical depth values can substantially degrade the visual quality of the mountain landscape, thus having, for instance, a large impact on tourism.…”

Section: Introductionmentioning

confidence: 99%

One Year of Measurements with a POM-02 Sky Radiometer at an Alpine EuroSkyRad Station

Diémoz

Campanelli

Estellés

2014

Journal of the Meteorological Society of Japan

View full text Add to dashboard Cite

Aerosol optical properties at the Alpine station of Saint-Christophe, northern Italy are measured with a POM-02 sky radiometer. Diffuse radiances from the sky and direct sun irradiances are processed with SKYRAD and SUNRAD algorithms, respectively, providing consistent results. The aerosol optical depth at the station is generally very low (0.10 at a wavelength of 500 nm); however, spikes (up to 0.75) can occur due to the transport of Saharan dust and smoke clouds moving on an intercontinental scale, according to NAAPS and HYSPLIT models. In addition, the aerosol microphysical properties are analyzed by means of the Ångström exponent and its spectral variation, which allows discrimination between different types of particles and the assessment of possible contamination by clouds. Influence by local meteorology and anthropogenic emissions is investigated, providing useful information to understand the pollution dynamics in mountainous regions. Finally, we highlight some algorithmic and instrumental issues that are still poorly understood.

show abstract

Boundary Layers and Air Quality in Mountainous Terrain

Cited by 30 publications

References 81 publications

Sensitivity of local air quality to the interplay between small- and large-scale circulations: a large-eddy simulation study

Sensitivity of local air quality to the interplay between small- and large-scale circulations: a large-eddy simulation study

Pollution and its Impacts on the South American Cryosphere

One Year of Measurements with a POM-02 Sky Radiometer at an Alpine EuroSkyRad Station

Contact Info

Product

Resources

About