The Influence of Urban Form and Vegetation on Near-Source Dispersion in a Realistic Urban Canopy
Notice bibliographique
Résumé
The atmospheric boundary layer controls many interactions within the troposphere from larger scale atmospheric features to land-atmospheric interactions. The urban boundary layer is the layer above an urban area that is heavily impacted by what happens below, while the urban canopy layer is impacted by the immediate surroundings within the urban area. Understanding flow within the urban canopy layer is crucial for determining the distribution of particulate matter in urban areas and implications for air quality and human health. \n \nPrevious experiments have examined downtown urban domains by releasing tracers to understand dispersion and dissipation of tracer plumes and how turbulence and urban geometry can affect them. Gaussian plume models have been used in the past to model dispersion in urban areas, especially for scalar transport. While multiple studies have been conducted to understand plume characteristics in urban environments, plume behavior close to point sources (< 1 km) and the effects of buildings and foliage on plume characteristics are not well understood. \n \nA field campaign, Tracer Release in an Urban Canopy (TRUC), was conducted in the Sunset Neighborhood of Vancouver, British Columbia in June 2017. This location is well-documented by previous field campaigns. The instrument configuration used during TRUC consisted of fifty spinning impaction traps, a mobile tower with 3-D sonic anemometers at two levels (16.6 m and 1.5 m), and five 2-D sonic anemometers deployed at 1.5 m. A mobile source at 2.4 m released 35 micron yellow/green and violet fluorescent microspheres from 3-D ultrasonic atomizer nozzles. Fourteen successful releases were conducted, each for twenty minutes, at four different locations throughout the neighborhood. \n \nAn equation consisting of the Superposition of two Orthogonally-oriented Gaussian plume distributions (SOG; Miller et al., 2018) was utilized to fit the concentration data collected. The SOG was compared to the TRUC data to determine suitability for interpolating between collection points. While the SOG did characterize the pattern of the concentration behavior well for both the near and far fields, the magnitude of the concentrations was often misrepresented. Channeling of the plume was observed during the TRUC campaign, which was characterized by the SOG most of the time. Comparison of the mean wind angle relative to the street network and various plume parameters were utilized to visualize the channeling of the plume. \n \nResults from this data and usage of the SOG equation were utilized to determine higher-order plume moment statistics. Turbulence, building, and vegetation statistics were also calculated to describe the plume characteristics and behaviors. Evidence of a relationship was seen between the mean wind direction and first order moment, as well as between the mean wind angle and the second order plume moment. While turbulence does affect the plume, especially with mean wind direction, the urban geometry proved to affect the plume characteristics more so in the urban domain.
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Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».