A44A-01
Overview of the National Atmospheric Release Advisory Center's Urban Research and Development Activities
This presentation describes the tools and services provided by the National Atmospheric Release Advisory Center (NARAC) at Lawrence Livermore National Laboratory (LLNL) for modeling the impacts of airborne hazardous materials. NARAC provides atmospheric plume modeling tools and services for chemical, biological, radiological, and nuclear airborne hazards. NARAC can simulate downwind effects from a variety of scenarios, including fires, industrial and transportation accidents, radiation dispersal device explosions, hazardous material spills, sprayers, nuclear power plant accidents, and nuclear detonations. NARAC collaborates on radiological dispersion source terms and effects models with Sandia National Laboratories and the U.S. Nuclear Regulatory Commission. NARAC was designated the interim provider of capabilities for the Department of Homeland Security's Interagency Modeling and Atmospheric Assessment Center by the Homeland Security Council in April 2004. The NARAC suite of software tools include simple stand-alone, local-scale plume modeling tools for end-user's computers, and Web- and Internet-based software to access advanced modeling tools and expert analyses from the national center at LLNL. Initial automated, 3-D predictions of plume exposure limits and protective action guidelines for emergency responders and managers are available from the center in 5-10 minutes. These can be followed immediately by quality-assured, refined analyses by 24 x 7 on-duty or on-call NARAC staff. NARAC continues to refine calculations using updated on-scene information, including measurements, until all airborne releases have stopped and the hazardous threats are mapped and impacts assessed. Model predictions include the 3-D spatial and time-varying effects of weather, land use, and terrain, on scales from the local to regional to global. Real-time meteorological data and forecasts are provided by redundant communications links to the U.S. National Oceanic and Atmospheric Administration (NOAA), U.S. Navy, and U.S. Air Force, as well as an in-house mesoscale numerical weather prediction model. NARAC provides an easy-to-use Geographical Information System (GIS) for display of plume predictions with affected population counts and detailed maps, and the ability to export plume predictions to other standard GIS capabilities. Data collection and product distribution is provided through a variety of communication methods, including dial-up, satellite, and wired and wireless networks. Ongoing research and development activities will be highlighted. The NARAC scientific support team is developing urban parameterizations for use in a regional dispersion model (see companion paper by Delle Monache). Modifications to the numerical weather prediction model WRF to account for characteristics of urban dynamics are also in progress, as is boundary-layer turbulence model development for simulations with resolutions greater than 1km. The NARAC building-resolving computational fluid dynamics capability, FEM3MP, enjoys ongoing development activities such as the expansion of its ability to model releases of dense gases. Other research activities include sensor-data fusion, such as the reconstruction of unknown source terms from sparse and disparate observations. This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48. The Department of Homeland Security sponsored the production of this material under the Department of Energy contract for the management and operation of Lawrence Livermore National Laboratory. UCRL-PROC-234355
A44A-02
Operational Generation of Urban Wind Fields to Support Transport and Dispersion Modeling
A realistic wind field is a key component to any transport and dispersion model simulation. In the urban environment observing the wind field accurately is complicated by the presence of the building structures themselves. In situ measurements are only representative over a limited area near the point of observation due to the influence of nearby buildings. Winds observed remotely, via radar or lidar, have good spatial resolution, but are limited to making measurements above rooftop. The Urban Shield project is an emergency response system for hazardous atmospheric releases in Arlington County Virginia. To provide building aware wind fields over a 100 square kilometer area for transport and dispersion modeling we use a combined approach of remotely sensed wind observations and very high resolution, ~10 meters, diagnostic wind modeling. In brief, the system uses 3-D wind analyses from Doppler radar and lidar as input to Los Alamos National Laboratory's QUIC-Urb empirical wind model. An overview of the system and results will be presented.
A44A-03 INVITED
Field Studies for Validation of Urban Dispersion Models - Current Status and Research Needs
Urban dispersion models are important tools in addressing consequences from potential releases of harmful airborne materials in urban areas. These models are used by emergency management, law enforcement, and intelligence personnel to effectively plan for and respond to potential terrorist attacks and accidents. Field studies are vitally important for improving and validating these urban dispersion models which are used to simulate contaminant dispersion in and around cities. Over the past decade, three major urban field studies have been designed and conducted in the United States. The primary objectives of these studies have been to advance the state-of-science of understanding and modeling atmospheric flows and dispersion in and around cities, and to provide field observation for validation of urban dispersion models. The three major field studies (Salt Lake City, October 2000; Oklahoma City, July 2003; and New York City, August 2005) were conducted in cities of different sizes, in different geographic regions and during different times of the year. The tracer and meteorological data from these three field campaigns provide a rich dataset for validation of urban dispersion models over a range of conditions. The status and uses of the three urban dispersion datasets will be summarized, followed by a discussion of the current observational gaps and research needs in characterizing specific urban dispersion processes, such as outdoor-indoor coupling and outdoor-subway coupling.
A44A-04
EPA's role and requirements in Radiological Dispersive Device (RDD) Emergency Response
The National Response Plan (NRP)'s Nuclear/Radiological Incident Annex describes how federal agencies should coordinate their actions when responding to nuclear/radiological incidents This would include sabotage and terrorist incidents, such as terrorist use of radiological dispersal devices (RDDs) or improvised nuclear devices, as well as reactor plant accidents (commercial or weapons production facilities), orphan radioactive material sources, transportation and foreign accidents involving nuclear/radioactive material, . For an Incident of National Significance (INS), DHS is always responsible for overall coordination of the Federal response taking the lead on external affairs (public, state/local, Congressional, White House), while working in consultation with the Coordinating Agency. The primary role of the Coordinating Agency during an INS is to focus on managing the technical aspects of the Federal radiological response, including establishing site perimeters, site characterization, contaminant control measures, data management, ensuring coordination of technical data, decontamination/cleanup, and waste management. EPA becomes the Coordinating Agency for non-terrorist incidents at nuclear facilities that are not DOD, DOE, or NRC/Agreement-State licensed facilities.even though DOD, DOE, and NRC become the Coordinating Agency for their own facilities, weapons, and materials. For all other radiological terrorist incidents, such as a RDD in a city, DOE is the initial Coordinating Agency. EPA will be expected to provide radiological emergency response of a magnitude, scope, and rapidity of response greater than in all their past experience. The EPA and Los Alamos National Laboratory have formed a partnership to current research to aid in response planning and enhance preparedness. Currently Los Alamos is defining the boundaries of contamination from an urban RDD using urban dispersion modeling, in order for the EPA to be able to identify, quantify and establish a level of preparation regarding response activities and resources. The dispersion modeling will also be used in the development of future exercise planning scenarios, training and in the development of field response procedures.
A44A-05
Factors Influencing Aerosol Formation in the Simulation of Alpha-pinene Oxidation Experiments
A detailed model is presented for the oxidation of the monoterpene alpha-pinene and the associated formation of Secondary Organic Aerosols (SOA). It is based on a quasi-explicit mechanism for the oxidation of alpha-pinene down to the formation of primary products, developed on objective grounds using advanced quantum theoretical methods, and on a simplified representation for the further oxidation of the products. Gas/particle partitioning follows a kinetic representation with coefficients from vapor pressures calculated using a dedicated group contribution method. This model is evaluated against a large number of laboratory experiments. The simulated and observed SOA yields agree to within a factor of 2 in most cases. The role of known shortcomings in the degradation mechanism is discussed. The role of association reaction of aldehydes and hydroperoxides in the particle phase is also estimated, based on laboratory measurements for the (forward and backward) reaction rates in different solvents. These reactions are found to have a significant impact in several low-NOx ozonolysis experiments.
A44A-06
Understanding Formation and Maintenance of Mixed-Phase Arctic Stratus Through Long- Term Observation at two Arctic Locations
Mixed-phase stratus clouds are commonly found in the Arctic, and have a strong effect on the radiation budget of this region. However, because of the unstable nature of mixed-phase systems, climate and even cloud-resolving models have difficulty accurately representing them and the radiative effects that they provide. In order to accurately predict climate scenarios for the future, a better representation of these prevalent structures must be implemented into current forecasting tools. The University of Wisconsin Arctic High Spectral Resolution Lidar (AHSRL) has been deployed to Barrow, Alaska and Eureka, Canada to gather long-term data sets of clouds at high latitudes. Together with a NOAA Millimeter Cloud Radar (MMCR), University of Idaho Polar Atmospheric Emitted Radiance Interferometer (PAERI) and NOAA Microwave Radiometer (MWR), the AHSRL has been collecting data at Eureka for over two years as a part of the Study of Environmental Arctic Change (SEARCH) program. In addition to these instruments there are twice-daily radiosonde launches as well as relatively frequent A-Train overpasses. A similar set of instruments, in conjunction with aircraft in-situ measurements recorded nearly two months worth of data at Barrow in 2004 for the Mixed-Phase Arctic Clouds Experiment (M-PACE). This data set for 2005 and 2006 alone contains over 1700 half-hour cases of mixed-phase stratus. Using direct measurements and retrieval algorithms, these cases along with those from 2004 and 2007 are being analyzed for long-term statistics on properties such as cloud top and cloud base heights, cloud thickness, cloud water content, ice water content, particle size, and particle number density. Additionally effects of temperature, pressure, wind speed and wind direction on the presence of these cloud structures are being analyzed. Also, observations from CloudSat and CALIPSO are being used to study the spatial extent of these cloud systems as well as to detect aerosol layers that may be aiding in the maintenance of the mixed-phase scenario. We will present results from these observations and introduce theories on the formation of these cloud systems based on these results. Additionally, comparison of observations with numerical simulations of specific cases will be shown, and future pathways for model improvement will be presented. http://lidar.ssec.wisc.edu
A44A-07
Observations of Homogeneous and Inhomogeneous Mixing in Warm Cumulus Clouds
The helicopter-borne instrument payload ACTOS was used to study the entrainment/mixing process in shallow warm cumulus clouds. Using ACTOS, high resolution measurements of the three-dimensional wind, temperature and humidity fields were made. In addition, cloud microphysical parameters such as the droplet number concentration and size were measured with a modified Fast-FSSP. The effect of entrained subsaturated air on the droplet number size distribution was analyzed using mixing diagrams which correlate droplet number concentration and droplet size. Both homogeneous and inhomogeneous mixing was observed to take place. The characteristic of the mixing process is compared to the Damköhler number. The Damköhler number is given by the ratio of the timescale for turbulent mixing and the reaction timescale, which is either the time for droplet evaporation, or the phase relaxation timescale. With ACTOS' instrumentation, the Damköhler number can be determined with a spatial resolution of about 15 m. In agreement with literature, low values of the Damköhler number correlate with the homogeneous mixing scenario, while higher values of the Damköhler number correlate with the inhomogeneous mixing scenario. It is shown that even within one cloud, different mixing scenarios can take place. The data suggest that homogeneous mixing is more likely to occur in the vicinity of the vigorous cloud core, while inhomogeneous mixing dominates in the outer, less turbulent part of the cloud. A case is presented in which the mixing led to the formation of drops that are larger than in the unmixed adiabatic core. This is of potential importance for precipitation formation in warm cumulus clouds.
A44A-08
Development of a new Convective Parameterization
Current convective parameterizations are often quite successful at simulating the mean properties of convective rainfall. However, they are generally less successful at simulating aspects of tropical rainfall variability, such as convectively coupled waves and the the Madden Julian Oscillation. I will discuss the development of a new convective parameterization. Attention will be given to its ability to simulate the diurnal behaviour of rainfall and mid-tropospheric relative humidity over the tropical oceans.