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
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.
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.