Near Field Dispersion during Joint-Urban 2003

The Joint Urban 2003 (JU2003) experiment was conducted in Oklahoma City, Oklahoma in July of 2003 with support from the Department of Homeland Security and the Defense Threat Reduction Agency. The purpose of JU2003 was to obtain observations for evaluating and improving atmospheric dispersion models that are used in urban areas.

Observations from other urban experiments indicate that estimating dispersion in the near field of a source is particularly difficult. Individual buildings, street canyons and clusters of buildings create complex circulations in which material disperses, often seemingly independent of the mean wind vector. As an example, observations indicate that material disperses rapidly in the vertical when buildings are present. JU2003 was designed to sample the near-field dispersion of a tracer gas using both real-time and integrated samplers. The real-time samplers were located at ground level and were generally within 50 meters of the release location. The integrated samplers were located up to 100 to 200 meters from the release, with several sampling locations on rooftops and upper levels of parking garages.

The near-field sampling network was deployed during a total of 6 Intensive Operations Periods (IOPs). During IOPs, portable sonic anemometers were deployed in the vicinity of the release point to document the circulation and the turbulence characteristics. The results for the six IOPs will be presented, including correlating the tracer concentration data with the local wind measurements.