Final Report for the Joint Urban 2003 Atmospheric Dispersion Study in Oklahoma City: Lawrence Livermore National Laboratory participation
The Joint Urban 2003 (JU2003) field study was designed to collect meteorological and tracer data resolving atmospheric dispersion at scales-of-motion ranging from flows in and around a single city block, in and around several blocks in the downtown Central Business District (CBD), and into the suburban Oklahoma City area a few km from the CBD. Indoor tracer and flow measurements within four downtown study buildings were also made in conjunction with detailed outdoor measurements investigating the outdoor-indoor exchange rates and mechanisms. The movement of tracer within the study buildings was also studied. The data from the field experiment is being used to evaluate models that are being developed for predicting dispersion of contaminants in urban areas. These models may be fast-response models based on semi-empirical algorithms that are used in real-time emergencies, or highly sophisticated computational fluid dynamics models that resolve individual building faces and crevices. The data from the field experiment, together with the models, can then be used to develop other advanced tools that are especially valuable in the efforts to thwart terrorists. These include tools for finding location and characteristics of a contaminant source; tools that can be used for real-time response or for forensic investigation. The tools will make use of monitoring networks for biological agents that are being established in several sensitive cities throughout the nation. This major urban study was conducted beginning June 28 and ending July 31, 2003. It included several integrated scientific components necessary to describe and understand the physical processes governing dispersion within and surrounding an urban area and into and within building environments. The components included characterizing: (1) the urban boundary layer and the development of the urban boundary layer within the atmospheric boundary layer, (2) the flows within and downwind of the tall-building core, (3) the flows within a street canyon including the effects of traffic on turbulence, (4) the surface energy balance within an urban area, (5) the dispersion of tracer into, out of and within buildings, and (6) the dispersion of tracer throughout the tall-building core and out to four km downwind from the release. The scientific elements of the study were accomplished using state-of-the-art meteorological and tracer instruments including lidars, sodars, radars, sonic anemometers, airplane-based meteorological sensors, fast-response tracer analyzers and helicopter-based remote tracer detectors. Winds and other meteorological quantities were measured continuously at nearly 200 locations in and around downtown Oklahoma City. Ten intensive operation periods (IOPs) of 8-hours each were completed during the 34-day study period where detailed meteorological, turbulence and tracer measurements were made. Sulfur hexafluoride tracer was released in downtown Oklahoma City and sampled in and around downtown and as far as four km downwind. During four of the ten IOPs the infiltration of tracer into four downtown buildings was studied with detailed measurements of tracer and flows within and surrounding some buildings. Tracer was sampled using over 200 integrated samplers and 25 fast response analyzers. Vertical measurements of tracer were made by placing samplers on the tops of nearly 20 buildings and by sampling tracer at 7 levels on a 90 m crane. The tracer and meteorological data collected in Oklahoma City is being used to evaluate and improve existing indoor and outdoor dispersion models, including fine-scale computational fluid dynamics (CFD) models, mesoscale numerical weather prediction models with sub-grid scale urban parameterizations and fast-response dispersion models that typically rely on empirical or semi-empirical relationships describing the atmospheric processes. The data will lead to improved algorithms and parameterizations within these models. Samplers to collect tracer data were located at various distances from the release locations for collecting data for validating urban dispersion models. At the same time, a dense network of meteorological instruments was deployed including in-situ anemometers and profiling platforms such as lidars, sodars and radars. The meteorological instruments were state of the art and were strategically placed to document the inflow and outflow boundary conditions from the CBD, as well as the evolution of the atmospheric boundary layer structure as the air circulated through and over the CBD. A high density network of atmospheric micrometeorological instruments was placed in one particular urban canyon to investigate circulation within the urban canyon and investigate the interaction of circulation within the canyon with that of the overall circulation.
- Research Organization:
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 885407
- Report Number(s):
- UCRL-TR-216437; TRN: US200616%%614
- Country of Publication:
- United States
- Language:
- English
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