Comparisons of Transport and Dispersion Model Predictions of the Mock Urban Setting Test Field Experiment

Abstract

The potential effects of a terrorist attack involving the atmospheric release of chemical, biological, radiological, nuclear, or other hazardous materials continue to be of concern to the United States. The Defense Threat Reduction Agency has developed a Hazard Prediction Assessment Capability (HPAC) that includes initial features to address hazardous releases within an urban environment. Improved characterization and understanding of urban transport and dispersion are required to allow for more robust modeling. In 2001, a scaled urban setting was created in the desert of Utah using shipping containers, and tracer gases were released. This atmospheric tracer and meteorological study is known as the Mock Urban Setting Test (MUST). This paper describes the creation of sets of HPAC predictions and comparisons with the MUST field experiment. Strong consistency between the conclusions of this study and a previously reported HPAC evaluation that relied on urban tracer observations within the downtown area of Salt Lake City was found. For example, in both cases, improved predictions were associated with the inclusion of a simple empirically based urban dispersion model within HPAC, whereas improvements associated with the inclusion of a more computationally intensive wind field module were not found. The use of meteorological observations closest to the array and well above the obstacle array-the sonic anemometer measurements 16 m above ground level-resulted in predictions with the best fit to the observed tracer concentrations. The authors speculate that including meteorological observations or vertical wind profiles above or upwind of an urban region might be a sufficient input to create reasonable HPAC hazard-area predictions.

Comparisons of Transport and Dispersion Model Predictions of the Joint Urban 2003 Field Experiment

“…5 , 6 Under the joint sponsorship of the DoD (Defense Threat Reduction Agency -DTRA) and DHS, a series of tracer gas releases were carried out in Oklahoma City starting on 28 June and ending on 31 July 2003. This field experiment, referred to as "Joint Urban 2003," included ten intensive operating periods (IOPs), in which the tracer gas sulfur hexafluoride (SF 6 ) was released in downtown Oklahoma City. 7 In total, twenty-nine 30-minute continuous SF 6 releases were accomplished with 2 hours of sampler monitoring following the start of each release.…”

“…This study examines the 29 continuous Joint Urban 2003 SF 6 releases and describes comparisons of the tracer gas sampler observations to Urban HPAC predictions. Several sets of predictions based on different configurations of Urban HPAC and varying meteorological inputs are examined in this paper.…”

“…The basic exponential profile shape used is described in Ref. [1][2][3][4][5][6] and has been shown to fit a variety of canopy types, including plant canopies as well as discrete objects. The canopy model has also been compared with experimental dispersion data within a plant canopy [Ref.…”

“…The canopy model has also been compared with experimental dispersion data within a plant canopy [Ref. [1][2][3][4][5][6][7] and with cube arrays in a wind tunnel [Ref. [1][2][3][4][5][6][7][8].…”

“…[1][2][3][4][5][6][7] and with cube arrays in a wind tunnel [Ref. [1][2][3][4][5][6][7][8]. In using HPAC to provide predictions in an urban environment, one can conveniently capture some of the effects of the urban canopy on transport and dispersion by setting the surface type to "urban."…”