Environmental Protection Agency (EPA) Regulatory Model Improvement Committee Model (AERMOD Cimorelli et al. 2007 Hanna and Zhou 2009).īritter and Hanna (2003) review the needs of urban dispersion models in terms of meteorological inputs. The atmosphere has large turbulence intensities and has nearly neutral stability in an area with many tall skyscrapers because of the large amount of mechanical mixing generated by the buildings, the contributions of anthropogenic heat sources, and the large capacity for storing solar energy that is possessed by materials that are used in streets and buildings ( Hanna et al. The energy flux information is needed to estimate hourly averages of winds, turbulence, and stability for input to transport and dispersion models that are being increasingly used in urban areas. (2005) describe multilayer approaches to model energy fluxes in downtown urban areas, but these have not been fully tested in downtown areas with tall skyscrapers. Most of the previous research on urban thermal energy fluxes has focused on suburban areas or urban areas with buildings of no taller than a few stories and has not addressed thermal energy fluxes in the midst of downtown skyscrapers. This study was spurred by the need to better understand diurnal variations of urban thermal energy fluxes near the surface in built-up downtown areas of large cities with tall skyscrapers of heights of 100 m and greater. These results should permit improved parameterizations of sensible heat fluxes in the urban downtown area with tall buildings. Also in agreement with observations in other cities is that the ground heat flux in the downtown area has a magnitude that is 3 or 4 times that in suburban or rural areas. In confirmation of measurements in other cities, the sensible heat flux in the downtown area is observed to be slightly positive (10–20 W m −2) at night, indicating nearly neutral or slightly unstable conditions. At street level in the downtown area, in the midst of tall skyscrapers, the ground heat flux and the sensible heat flux are relatively large and the latent heat flux is relatively small when compared with concurrent fluxes observed in the upwind suburban areas. The results of analysis of urban heat flux components from 10 locations in suburban and built-up downtown areas in Oklahoma City, Oklahoma, during the Joint Urban 2003 (JU2003) field experiment are presented here. In this paper, the authors work with some high-quality and relevant but arguably underutilized data. Because of recent concerns about dispersion in built-up downtown areas of large cities, there is a need to estimate sensible heat flux in the midst of tall buildings. The sensible heat flux is a major priority, because it is combined with the momentum flux to estimate the stability, the wind profile, and the turbulence intensities. Surface energy fluxes, at averaging times from 10 min to 1 h, are needed as inputs to most state-of-the-art dispersion models.
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