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