Briana Lynch- Thesis Defense - Aug 27

“The Influence of Urban Form and Vegetation on Near-Source Dispersion in a Realistic Urban Canopy” NWC 5600 ABSTRACT: 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

Start

August 27, 2019 - 9:00 am

End

August 27, 2019 - 10:00 am

Address

120 David L Boren Blvd, Norman, OK 73072   View map

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

NWC 5600

ABSTRACT:

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.

 

Previous 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 the urban domain, as well as understand specific flow around complex objects, like various building shapes and vegetation. 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. This location is well-documented by previous field campaigns. Instrument configuration used during TRUC consisted 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 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.

 

An 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. Results 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. 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.