Turbulence kinetic energy in the Oklahoma City urban environment

The Joint URBAN 2003 field experiment took place in Oklahoma City, Oklahoma, during July 2003 to explore the effect of an urban canopy on the transport and diffusion of a passive tracer released in an urban area. Over one hundred three-dimensional sonic anemometers were deployed in and around the urban area to monitor wind speed, direction, and turbulence during releases of SF6. Deployment locations include a profile of eight sonic anemometers mounted on a crane located 1 km north (typically downwind) of the central business district, and several surface meteorological towers within an urban canyon.

We quantify the effect of the urban area on atmospheric turbulence using mean quantities and turbulent fluctuations from these sonic anemometers. We calculate several parameters that are typically used in parameterizations of urban turbulence, and compare the observed values to the empirical results currently used in many atmospheric urban models and results derived from wind tunnel studies. These parameters include the drag coefficient (local friction velocity/local mean wind speed) and normalized turbulent standard deviations.

We also quantify the turbulence kinetic energy (TKE) budget in the Oklahoma City urban area. Our analysis considers spectral data from the sonic anemometers: using streamwise spectra, TKE dissipation rates are calculated. The other terms in the TKE budget are also calculated. TKE budgets in various stability regimes will be presented and compared to those predicted by surface similarity theory and observed in other field experiments. The dominant length scales of velocity spectra will also be presented.

This work was performed under the auspices of the U.S. Department of Energy by University of California, Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48.