The Influence of Urban Form and Vegetation on Near-Source Dispersion in a Realistic Urban Canopy

Understanding flows 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. 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. A field campaign, Tracer Release in an Urban Canopy (TRUC), was conducted in the Sunset Neighborhood of Vancouver, British Columbia in June 2017, consisting of fifty spinning impaction traps, a mobile tower with 3-D sonics 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 μm yellow 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. An equation consisting of the Superposition of two Orthogonally-oriented Gaussian plume distributions (SOG) (Miller et al., Agr. Forest Meteorol., vol. 256-257, 2018, pp. 125-136) will be utilized to fit the concentration data collected. Results from this data and usage of the SOG equation will be applied to determine higher-order plume shape statistics, including skewness and kurtosis. The influence of urban geometry and turbulence statistics on plume moments will also be explored.