ARB Research Seminar

This page updated June 19, 2013

What Have Urban Experiments Taught Us About Atmospheric Flow and Transport? (Urban Flow and Transport Model Development and Evaluation with Field Experiments)

Julie K. Lundquist, Ph.D., National Atmospheric Release Advisory Center, Lawrence Livermore National Laboratory

August 15, 2007
Cal EPA Headquarters, 1001 "I" Street, Sacramento, CA



Releases of hazardous materials such as toxic industrial chemicals or chemical/biological agents, whether due to industrial accidents or terrorist releases, pose significant risks to civilian populations. Urban areas are the most consequential locations for such releases due to large populations and difficult evacuation logistics; however, urban areas often experience complex non-uniform winds which cannot be easily predicted by conventional transport and dispersion models. For advance planning, for emergency response, and for determining community exposure, observational and modeling tools designed specifically for urban areas can be used to predict and track the transport and dispersion of these hazardous materials.

Verification and validation of these tools is possible using data from field experiments. We discuss insights gleaned from the Joint URBAN 2003 (JU2003) urban dispersion experiment (Oklahoma City, July 2003), the largest urban dispersion experiment to date. We compare observed dispersion patterns with those predicted with several of the urban modeling tools utilized by Lawrence Livermore National Laboratory's (LLNL's) National Atmospheric Release Advisory Center (NARAC). In densely built-up areas, like an urban core, the mechanical production of turbulence, which can be simulated with a computational fluid dynamics model like NARAC's FEM3MP, dominates the flow and dispersion. FEM3MP simulations agree quite well with observations in Oklahoma City's urban core, even when using a mixed virtual-explicit building simulation approach to increase computational efficiency.

Because the source of a release is often unknown during the critical emergency response phase, LLNL has also developed a methodology for discerning the strength and location of an accidental release from sparse observations. Examples of this "event reconstruction" based on the JU2003 releases show that our approach can successfully identify sources of these releases. Both conventional forward simulation tools and this backward event reconstruction methodology are important components of response to releases of hazardous materials.

Speaker Biography

Julie K. Lundquist, Ph.D., is a staff scientist in the Energy and Environment Directorate at Lawrence Livermore National Laboratory, where she has been employed since 2002. Dr. Lundquist's research synthesizes observations of the atmospheric boundary layer with innovative data analysis methods and numerical simulations in order to improve our understanding and prediction of transport and diffusion in the atmosphere. Her work directly supports the National Atmospheric Release Advisory Center (NARAC). Dr. Lundquist is particularly interested in the intermittent and inhomogeneous turbulence observed in urban and stable boundary layers and methods for parameterizing turbulence in numerical weather prediction models.

Dr. Lundquist obtained her Ph.D. in Astrophysical, Planetary, and Atmospheric Science from the University of Colorado at Boulder in 2001, following a Bachelors degree in English and Physics at Trinity University and a M.S. degree from the University of Colorado at Boulder.

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