The Joint Urban 2003 (JU2003) experiment was conducted in July 2003, principally supported by the Chemical and Biological National Security Program (CBNP, originally DOE and now DHS) and the Defense Threat Reduction Agency (DTRA). JU2003 was designed to obtain observations for evaluating and improving atmospheric dispersion models at scales from around a few buildings through the entire urban area. Sulfur Hexafluoride (SF6) was released at various locations within the central business district (CBD) of Oklahoma City and was measured in the near-field using real-time infrared spectrometry. Bag samples were also collected for later laboratory analysis. During releases, arrays of three-dimensional and two-dimensional ultra-sonic anemometers were deployed in the near-field of the release.

Dispersion in the near-field strongly depends on the small scale variation in the wind field and on the presence of buildings and other urban structures. Observations indicate that material disperses rapidly in the vertical when buildings are present. Observations from the SF6 sampling and the anemometers are presented and the processes that contribute to the near-field dispersion are explored.

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.