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PROBABILISTIC CHARACTERIZATION OF ATMOSPHERIC TRANSPORT AND DISPERSION
Citation:
IRWIN, J., W. B. PETERSEN, AND S. HOWARD. PROBABILISTIC CHARACTERIZATION OF ATMOSPHERIC TRANSPORT AND DISPERSION. Presented at NOAA/EPA Golden Jubilee Symposium, Durham, NC, September 20 - 21, 2005.
Impact/Purpose:
The scientific modeling expertise of NERL/AMD technical staff often results in requests for staff to provide timely support and advice to EPA Management in the event of a national emergency and to perform the research on model development and evaluation in support of the development of early response models. Flow and dispersion in urban areas is extremely complex and not well characterized in spite of their importance to homeland security and emergency response applications. Specifically, understanding the transport and fate of pollutants in urban canopies is critical for implementing air quality standards, performing risk assessments, developing environmental management strategies, supporting human exposure and health effects studies. Recently, though, much focus has been placed on supporting the development of homeland security tools needed to prepare for and respond to malicious attacks with toxic chemicals. Toward this goal, laboratory studies have been conducted in EPA's Meteorological Wind Tunnel for idealized urban settings, for very complex settings such as lower Manhattan surrounding the World Trade Center (WTC) site, and for very building specific cases such as the Pentagon. Continued studies in a variety of urban morphologies and release scenarios are needed to support a more thorough understanding of urban dispersion and the development of refined numerical modeling approaches.
Description:
Dispersion models are used to assess the possible extent and severity of accidental or terrorist releases of toxic materials. Most operational models only provide a characterization of average concentrations and conditions following a release. Knowledge of the variability about the average is vital to the correct interpretation of model results. The variability can be characterized as coming from two primary sources, 1) wind field (trajectory) variability, and 2) unresolved (diffusion) variability not currently characterized by the model parameterizations. This study provides a quantification of these two sources of variability.