Incident Wind Direction Effect on Plume Transport and Dispersion and Mean Wind and Turbulence Fields in an Urban Area: Evaluation of Joint Urban 2003 Field Experiment Data

The Joint Urban 2003 tracer dispersion field experiment, held in downtown Oklahoma City during the month of July 2003, was conducted to characterize the transport and dispersion of point source releases in cities. As part of this work, tracer concentrations measured throughout downtown Oklahoma City have been analyzed as a function of inflow wind direction. It is observed that the extent of spread of the released tracer is different for different wind directions. We have looked at the mean wind and turbulence fields in order to provide an explanation for this observation. The flow field and the turbulence structure in the core of the urban area is highly dependent on the ambient wind direction and the local morphology. For certain wind direction bins there is high magnitude of unidirectional flows and increased turbulence observed in the street canyons. Invariably for such cases the released tracer has higher spread. In this talk, we will show the plume concentration measurements for different inflow wind directions and relate them to the details associated with the structure of the mean flow and turbulence. This work may ultimately benefit parameterized urban dispersion models.