Fluid Dynamics of Urban Atmospheres in Complex Terrain

Fernando, H. J. S.

doi:10.1146/annurev-fluid-121108-145459

Cited by 194 publications

(121 citation statements)

References 93 publications

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“…The so called 'anthropogenic stressors' (Fernando, 2010) result from sources of emission including human metabolism, vehicles, heating, ventilation and air conditioning (HVAC) in buildings, industry and power plants. Anthropogenic heat and moisture inputs vary significantly both in space and time, of which measurements are not readily available in most cities.…”

Section: Anthropogenic Heat and Watermentioning

confidence: 99%

“…Being humanity's engine of creativity, wealth production and economic growth, rapid urbanization has also emerged as the source of many adverse environmental impacts due to 'anthropogenic stressors' (Fernando, 2010) such as the heat island effect, emissions of greenhouse gases, production of pollutants, etc. Understanding of urban land surface processes, such as transport of energy, water, trace gases and pollutants, is key to solving many urban environmental problems.…”

Section: Introductionmentioning

confidence: 99%

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A coupled energy transport and hydrological model for urban canopies evaluated using a wireless sensor network

Wang

Bou‐Zeid

Smith

2012

Quart J Royal Meteoro Soc

192

145

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We propose a new surface exchange scheme coupling the transport of energy and water in urban canopies. The new model resolves the subfacet heterogeneity of urban surfaces, which is particularly useful for capturing surface exchange processes from vegetated urban surfaces, such as lawns or green roofs. We develop detailed urban hydrological models for surfaces consisting of either natural (soil and vegetation) or engineered materials with water-holding capacity. The coupling of energy and water transport enables us to parametrize surface evaporation from different urban facets including soils, vegetation and water-holding engineered surfaces. The new coupled model is evaluated using field measurement data obtained through a wireless sensor network deployed over the Princeton University campus. Comparison of model prediction and measured results shows that the proposed surface exchange scheme is able to predict widely varying surface temperatures for each subfacet with good accuracy. Different weather conditions and seasonal variability are found to have insignificant effect on the model performance. The new model is also able to capture the subsurface hydrological processes with reasonable accuracy, particularly for urban lawns. The proposed model is then applied to assess different mitigation strategies of the urban heat island effect.Key Words: urban canopy model; urban hydrology; urban heat island; land-atmosphere interaction; water-holding pavements

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Section: Anthropogenic Heat and Watermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A coupled energy transport and hydrological model for urban canopies evaluated using a wireless sensor network

Wang

Bou‐Zeid

Smith

2012

Quart J Royal Meteoro Soc

192

145

View full text Add to dashboard Cite

show abstract

“…Interactions within the cold air pools can be further complicated by other local dynamic effects, such as breeze-like circulations (e.g. Lareau et al, 2013) or up-and down-slope winds (Fernando, 2010). This complexity challenges numerical weather prediction (NWP) models, which often cannot properly resolve and hence predict air pollution episodes, in particular those developing during the periods with strong stable stratification in the lower atmosphere and mountainous terrain (e.g.…”

mentioning

confidence: 99%

“…Thus, the problem could be partially related to an insufficient spatial model resolution with respect to the relevant topographic features. But partially, it should be also related to the breakdown of inadequate turbulent mixing schemes for the atmospheric stably stratified boundary layer (Atlaskin and Vihma, 2012;Fernando and Weil, 2010;Mahrt, 2014;Zilitinkevich et al, 2015). These and other inaccuracies in the air quality assessment and modelling motivated the Pan-Eurasian Experiment (PEEX) community to include air pollution in the stably stratified boundary layers in the list of research priorities addressing the environmental and socio-economic challenges of the northern high latitudes (Lappalainen et al, 2016).…”

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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.

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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.

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“…Large urban settlements such as Los Angeles, Hong Kong, and Rio de Janeiro have grown within or in the shadow of complex terrain, and managing the air quality of such cities requires a good understanding of the air flow patterns that spill off of mountains. On a daily time scale, the interconnected engineered and natural systems that sustain urban metabolism and quality of life are affected by weather [Fernando, 2010]. Further, recent military engagements in remote mountainous areas have heightened the need for better weather predictions-alpine warfare is considered to be one of the most dangerous types of combat.…”

mentioning

confidence: 99%

Field Studies Delve Into the Intricacies of Mountain Weather

Fernando¹,

Pardyjak²

2013

EoS Transactions

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Mountain meteorology, in particular weather prediction in complex (rugged) terrain, is emerging as an important topic for science and society. Large urban settlements such as Los Angeles, Hong Kong, and Rio de Janeiro have grown within or in the shadow of complex terrain, and managing the air quality of such cities requires a good understanding of the air flow patterns that spill off of mountains. On a daily time scale, the interconnected engineered and natural systems that sustain urban metabolism and quality of life are affected by weather [Fernando, 2010]. Further, recent military engagements in remote mountainous areas have heightened the need for better weather predictions—alpine warfare is considered to be one of the most dangerous types of combat.

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Fluid Dynamics of Urban Atmospheres in Complex Terrain

Abstract: in global atmospheric model development through improved parameterizations: Challenges, opportunities and strategies, Bull. Am. Meteorol. Soc., 91,[869][870][871][872][873][874][875]

Cited by 194 publications

References 93 publications

A coupled energy transport and hydrological model for urban canopies evaluated using a wireless sensor network

A coupled energy transport and hydrological model for urban canopies evaluated using a wireless sensor network

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

Field Studies Delve Into the Intricacies of Mountain Weather

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