Profiles of TKE and sensible heat and momentum fluxes in the roughness sub-layer of a city

Abstract

Measurements with sonic anemometers on a number of towers in the suburban and urban domains of Oklahoma City during Joint Urban 2003 are examined to characterize the height dependence of turbulent properties within the roughness sub-layer (RSL). Values of the displacement height for five tower locations have previously been shown to vary both with location and with wind direction. Values for the suburban locations obtained from measurements at 10 m varied from as little as 1.4 m to as much as 6.1 m. Values for the urban locations varied from 4.2 m to 7.5 m. It is clear then that for the urban locations the sonic anemometer measurements at 10 m (and below) were entirely within the RSL, while even those at suburban locations were often within this layer. In this paper we examine the profiles of turbulent kinetic energy, sensible heat flux, and momentum flux obtained at the various locations. We stratify the measurements by time of day and by wind direction in order to gain insight into the structure of this layer as it is affected by stability and surface roughness properties. We look, too, at profiles obtained from measurements on taller towers (30 m and 85 m) to see whether a constant flux layer (CFL) might be identified at higher levels above the city.