Fourth Symposium on the Urban Environment


Dense network of near-field observations of building-canopy winds and tracer concentrations during the URBAN 2000 experiment

Frank J. Gouveia, LLNL, Livermore, CA; and J. H. Shinn

The URBAN 2000 field campaign was conducted in Salt Lake City during October 2000 and consisted of ten Intensive Observation Periods during which tracers were released from midnight to early morning. The concentration fields and wind fields were measured in some detail from near the source and out to 5 km downwind. URBAN 2000 was conducted by the Chemical and Biological National Security Program, US Department of Energy and involved scientists from 5 National Laboratories, NOAA, DoD, and a few international agencies. Information about URBAN 2000 can be found on a website:

We conducted field experiments to define the flow and tracer-concentration fields around several buildings in downtown Salt Lake City during the URBAN 2000 experiment. Our network of observations was situated in a one-block area with three large, multi-story buildings and a large, structure-less parking lot. Seven 2-D sonic anemometers were located around one of these buildings (Heber Wells) at a height of 2.5 m. The one-second samples of wind were retained and also summarized into 10-minute averages. Stationary bag samplers collected air at fifteen locations yielding a total of 2357 samples. These samples were analyzed for SF6 and represent 5-minute averages of tracer concentration. One fast-response SF6 sampler (infrared spectrophotometer) was located just 60 m from the SF6 point source. All of these wind and air-sampling instruments were within 200 m of the source. The forcing wind during the 18 tests was light (~2 m/s). Our observations of building-canopy winds were usually less than 0.5 m/s and highly variable, but generally demonstrate a predictable pattern of wind around the building. Wind direction was bimodal, especially in the building lee, but even on the upwind sides, indicating the lee effect from the buildings further upwind. We present data from IOP 10 as an example. The primary use of the data would be to critique and evaluate Computational Fluid Dynamics (CFD) models under development in CBNP.

Session 12, Urban field projects: URBAN-VTMX
Thursday, 23 May 2002, 1:30 PM-3:44 PM

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