Overview:

The Field Research Division along with several other scientists from government laboratories, universities, and private companies participated in a tracer experiment held in Oklahoma City during July of 2003. The study has since been named Joint Urban 2003 (JU03). The Department of Homeland Defense and the Defense Threat Reduction Agency national security programs funded the study. Data collected from the study will be used in developing and testing new atmospheric dispersion models. These models in turn will support intelligence, law enforcement, and emergency management to help counter any threat of chemical or biological attack on civilian populations.

Objectives:

• Use state of the art remote sensing and in-situ meteorological instruments to continuously measure winds and turbulence of the atmosphere from the ground through several kilometers above the ground;

• Collect flow and tracer concentration data at various distances from the release point including in and around a

single block, in and around several blocks in the downtown Central Business District (CBD), and into the suburban Oklahoma City area several km from the CBD;

• Investigate tracer exchange through a building envelope;

• Create a quality controlled and consistency-checked data archive suitable for modeling and research use.

Summary:

FRDs main responsibility in the study was the sulfur hexafluoride (SF₆) tracer dissemination and data collection. FRD released SF₆ during ten Intensive Observation Periods (IOPs). Each IOP included two or three quasi-continuous (30-min.) point releases (17 daytime, 12 nocturnal) and 40 puff (instantaneous) releases (25 daytime and 15 nocturnal). SF₆ concentrations were sampled and measured as the tracer dispersed through Oklahoma City. Sampling was done using programmable integrating gas samplers (PIGS) and new Super PIGS, and quasi-instantaneous measurements were taken using fast- response tracer gas analyzers (TGAs). The samplers were positioned at approximately 150 locations within Oklahoma City, which included street-level, rooftop, and pedestrian tunnel locations within the CBD, and on arcs at distances of 1,2, and 4 km from the point of tracer release. Extra samplers were also positioned at selected stations for quality control. Ten van-mounted TGAs were also driven to varying locations within Oklahoma City to intercept dispersing tracer plumes. FRD deployed a sonic anemometer and temperature/relative humidity probe to help measure turbulence and stability at the release site and a sodar to help measure the upper level winds near the CBD.

Conclusions:

Analysis of the sampler data leads to the following conclusions: (1) concentrations measured at street level often exceeded rooftop-level measurements by a factor of 3 or greater; (2) tracer dissipation is retarded by roughness elements to a greater degree at street level than at rooftop levels; (3) tracer released at street level during moderate winds rapidly disperses to rooftop levels near the release location; (4) tracer released at street level can be channeled down street canyons at angles approaching 60 to 80 degrees from the downwind direction; (5) tracer dissipation is significantly faster during the day than at night; (6) rooftop-level wind speed more strongly influences dissipation rates at night than during the day; (7) street-level turbulence measurements can be useful predictors of tracer dissipation rates; and (8) tracer accumulation and dissipation in underground pedestrian tunnels happens at time scales of at least an order of magnitude greater than those experienced in the open air. All accessible JU03 experimental data are available on the web from archives administered by the U.S. Army Dugway Proving Ground Meteorology Division.

Images:

SF₆ release site and miscellaneous pictures

Videos:

Puff Tracer Release (Requires Quicktime). Note that the dust released in the video is not the tracer. It is simply talc that lines the inside of any large balloon to keep it from sticking together. (The actual tracer is invisible.)

Presentations:

• Clawson, K.L., R.G. Carter, D.J. Lacroix, N.F. Hukari, and K.J. Alwine. 2004. Joint Urban 2003 vertical SF₆ real-time analyzer and time-integrated sampler data characteristics. Fifth Conference on Urban Environment, August 23-26, 2004, Vancouver, British Columbia. American Meteorological Society. [View / download PDF ]

• K.J. Alwine, K.L. Clawson, J.J. Leach, D. Burrows, R. Wayson, J. Flaherty, and E. Allwine. 2004. Urban dispersion processes investigated during the Joint Urban 2003 Study in Oklahoma City. Fifth Conference on Urban Environment, August 23-26, 2004, Vancouver, British Columbia. American Meteorological Society.

• J.C. Doran, K.J. Alwine, K.L. Clawson, R.G. Carter, 2005. Rentention of tracer gas from instantaneous releases of SF₆ in an urban environment. 86th AMS Conference, January 29-February 2, 2006, Atlanta, Georgia. American Meteorological Society. [View / download PDF]

Publications:

• Clawson, K.L., R.G. Carter, D.J. Lacroix, C.A. Biltoft, N.F. Hukari, R.C. Johnson, J.D. Rich, S.A. Beard, T. Strong. 2005. Joint Urban 2003 (JU03) SF₆ Atmospheric Tracer Field Tests. NOAA Technical Memorandum OAR ARL-254, Air Resources Laboratory, Idaho Falls, Idaho, 237 pp. [View / download PDF]

Collaborators (20+) including:

• NOAA ARL Atmospheric Turbulence and Diffusion Division (ATDD)

• Pacific Northwest National Laboratory

• Lawrence Livermore National Laboratory

• Los Alamos National Laboratory

• Lawrence Berkley National Laboratory

• Dugway Proving Grounds

• Army Research Office

• Defense Threat Reduction Agency

• Oklahoma University

• University of Utah

• Indiana University

Joint Urban 2003 Data Repository:

https://ju2003-dpg.dpg.army.mil/ (Currently offline)

Contact:

Roger Carter
1750 Foote Dr.
Idaho Falls, ID 83402
(208)526-2745
email: Roger.Carter@noaa.gov