Editorial Type:
Article
Article Type:
Research Article

Temporal and Spatial Aspects of Velocity Variance in the Urban Surface Roughness Layer

Bruce B. Hicks MetCorps, Norris, Tennessee

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Elena Novakovskaia Earth Networks, Inc., Germantown, Maryland

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Ronald J. Dobosy NOAA/Air Resources Laboratory/Atmospheric Turbulence and Diffusion Division, and Oak Ridge Associated Universities, Oak Ridge, Tennessee

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William R. Pendergrass III NOAA/Air Resources Laboratory/Atmospheric Turbulence and Diffusion Division, Oak Ridge, Tennessee

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William J. Callahan Earth Networks, Inc., Germantown, Maryland

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Print Publication:
01 Mar 2013
DOI:
https://doi.org/10.1175/JAMC-D-11-0266.1
Page(s):
668–681
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Abstract

Data from six urban areas in a nationwide network of sites within the surface roughness layer are examined. It is found that the average velocity variances in time, derived by averaging the conventional variances from a network of n stations, are nearly equal to the velocity variances in space, derived as the variances among the n average velocities. This similarity is modified during sunlit hours, when convection appears to elevate the former. The data show little dependence of the ratio of these two variances on wind speed. It is concluded that the average state of the surface roughness layer in urban and suburban areas like those considered here tends toward an approximate equality of these two measures of variance, much as has been observed elsewhere for the case of forests.

Corresponding author address: Bruce B. Hicks, Metcorps, P.O. Box 1510, Norris, TN 37828-1510. E-mail: hicks.metcorps@gmail.com

Abstract

Data from six urban areas in a nationwide network of sites within the surface roughness layer are examined. It is found that the average velocity variances in time, derived by averaging the conventional variances from a network of n stations, are nearly equal to the velocity variances in space, derived as the variances among the n average velocities. This similarity is modified during sunlit hours, when convection appears to elevate the former. The data show little dependence of the ratio of these two variances on wind speed. It is concluded that the average state of the surface roughness layer in urban and suburban areas like those considered here tends toward an approximate equality of these two measures of variance, much as has been observed elsewhere for the case of forests.

Corresponding author address: Bruce B. Hicks, Metcorps, P.O. Box 1510, Norris, TN 37828-1510. E-mail: hicks.metcorps@gmail.com
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Journal of Applied Meteorology and Climatology

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