Mesoscale atmospheric models with second-order turbulence closures require a parameterization of the turbulent kinetic energy (TKE) dissipation rate. Such parameterizations typically express dissipation rate as function of TKE and a dissipative length scale, and these parameterizations are based on simplifying assumptions that are not satisfied in urban environments. The enhanced and heterogeneous turbulence and mixing encountered in the urban environment require improved parameterizations. To develop such parameterizations, it is important to observe and quantify dissipation rate under different conditions in urban environments.

The Joint URBAN 2003 field experiment took place in Oklahoma City, Oklahoma, during July 2003. Over one hundred three-dimensional sonic anemometers were deployed in and around the urban area to monitor wind speed, direction, and turbulence during dispersion experiments in the city center. Sonic anemometers were sited in various urban microenvironments, such as within a street canyon, at an intersection of two boulevards, atop a building in the built-up city center, in a less-built-up area just downwind of the city center, etc. The inertial dissipation method (Oncley et al., 1996; Piper, 2001) will be applied to data from these sonic anemometers to calculate dissipation rates and dissipative length scales throughout the urban area. Preliminary observations within the urban area will be compared to each other and with rural observations of dissipation to illustrate the variability between urban microenvironments as a first step toward improved dissipation parameterizations.

This work was performed under the auspices of the U.S. Department of Energy by University of California, Lawrence Livermore National Laboratory under Contract W-7405-Eng-48.