3 research outputs found
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Building Height-Characteristics in Three U.S. Cities
Urban canopy parameterizations have been used to represent urban effects in numerical models of mesoscale meteorology, the surface energy budget, and pollutant dispersion. The urban canopy parameterization accounts for the drag exerted by urban roughness elements, the enhancement of turbulent kinetic energy, and the alteration of the surface energy budget (Brown 2000). Accurate representation of urban effects in numerical simulations requires the determination of urban morphological parameters, including building height statistics. Computer analysis of 3-D building digital datasets can provide details of the urban environment in an efficient manner. Ratti ut al. (2001) describe a method for obtaining urban canopy parameters from digital imagery using image processing techniques, Burian et al. (2002) present an alternative analysis approach using a geographic information system (GIS). In this paper, building height statistics computed for three U.S. cities following the GIS approach are presented
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An overview of building morphological characteristics derived from 3D building databases.
Varying levels of urban canopy parameterizations are frequently employed in atmospheric transport and dispersion codes in order to better account for the urban effect on the meteorology and diffusion. Many of these urban parameterizations need building-related parameters as input. Derivation of these building parameters has often relied on in situ 'measurements', a time-consuming and expensive process. Recently, 3D building databases have become more common for major cities worldwide and provide the hope of a more efficient route to obtaining building statistics. In this paper, we give an overview of computations we have performed for obtaining building morphological characteristics from 3D building databases for several southwestern US cities, including Los Angeles, Salt Lake City, and Phoenix
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Roughness length and displacement height derived from building databases
In air quality and meteorological models, the bulk drag and turbulence enhancement due to cities is often parameterized through the roughness length (z{sub 0}) and displacement height (d). These log-law parameters have traditionally been derived from meteorological measurements and building morphological characteristics (e.g., see Grimmond and Oke, 1999). We are in the midst of an effort to characterize the morphological properties of some of the major cities in the western U.S. At this time we have completed the analyses for Los Angeles, Phoenix, and Salt Lake City. We are currently working with datasets from Portland and Houston and anticipate analyzing more than five other cities in the near future. Morphological analysis of 3-D building databases produces a suite of urban canopy parameters that can be incorporated into mesoscale meteorological, surface energy budget, and pollutant dispersion models. Additional computations can be performed to derive roughness length and displacement height using several common morphological formulae described in the literature. This paper summarizes the derivation of roughness length and displacement height for a 12-km{sup 2} section of downtown Los Angeles, 16-km{sup 2} section of downtown Phoenix, and 6-km{sup 2} section of downtown Salt Lake City. We correlate the computed roughness length and displacement height to underlying land use type