Expert Report

Each report is produced by a committee of experts selected by the Academy to address a particular statement of task and is subject to a rigorous, independent peer review; while the reports represent views of the committee, they also are endorsed by the Academy. Learn more on our expert consensus reports.

This report examines ways in which atmospheric dispersion models and meteorological observations can be used to help emergency personnel prepare for and respond to a chemical, biological or nuclear attack.

Key Messages

  • Urban building and topography three-dimensional databases need to be developed and maintained for use in numerical and wind-tunnel dispersion simulations.
  • Atmospheric observations and dispersion models must interface seamlessly with the needs of emergency responders.
  • Civilian instruments currently are available only for research use.
  • Dispersion modelers and meteorologists would benefit from learning how nowcasts and forecasts are used in emergency response situations.
  • Dispersion models used for emergency planning and response should provide confidence estimates that prescribed concentrations will not be exceeded outside of predicted hazard zones.
  • Doppler radar systems can be useful for estimating boundary layer winds, monitoring precipitation, and possibly tracking some C/B/N plumes.
  • Emergency managers need a realistic understanding of the bounds on the uncertainties of dispersion model predictions.
  • Emergency responders face a confusing array of seemingly competitive atmospheric transport model systems supported by various agencies, and in many cases, they do not have a clear understanding of where to turn for immediate assistance.
  • Emergency response managers would benefit from training that conveys the strengths and weaknesses of existing observational and dispersion modeling tools and the situations under which various types of tools perform best.
  • Focused field exercises are needed to understand the behavior of modeled transport and dispersion in different weather regimes and C/B/N release scenarios, particularly for nocturnal conditions.
  • It is necessary to learn how to more effectively assimilate into models an appropriate range of meteorological data (e.g., wind, temperature, and moisture data) from observing systems as well as real-time data from C/B/N sensors, especially as the quality and availability of these data increase. It also is important to effectively couple dispersion models with appropriate source characterization models.
  • Local topography and the built environment lead to local wind patterns that can carry contaminants in unexpected directions. Observational networks must represent these local flows as faithfully as possible.
  • Mobile observational platforms can provide valuable information and fulfill multiple needs in the first minutes to hours after a hazardous release.
  • New dispersion modeling constructs need to be further explored and possibly adapted for operational use in urban settings. This includes advanced, short execution time models, slower but more accurate computational fluid dynamics and large-eddy simulation models, and models with adaptive grids.
  • Radar wind profilers and radio acoustic sounding system profilers, which measure variations of the horizontal wind and temperature, respectively, with height and enable identification of turbulent layers, provide important information for response to C/B/N attacks and are relatively inexpensive and easy to maintain.
  • Techniques must be developed for constructing ensembles of model solutions on the urban scale so that probabilistic rather than deterministic information can be provided to emergency managers.
  • The bulk effects of urban surfaces on the surface energy, moisture, and momentum are not well accounted for in most meteorological models. Existing development work in this area should be enhanced and the improved modeling techniques adopted more widely.
  • The current array of surface observational systems needs to be better used and enhanced.
  • The most basic observations required for tracking and predicting the dispersion of a hazardous agent include identification of the plume, characterization of low-level winds (to follow the plume trajectory), characterization of the depth and intensity of the turbulent layers through which the plume moves (to estimate plume spread), and identification of areas of potential agent degradation and dry or wet deposition.
  • There is a clear need for more central coordination among the various federal agencies currently involved and among the relevant players at the local, regional, and national levels.
  • There is a wealth of knowledge about meteorological and dispersion models residing in universities, National Weather Service Weather Forecast Offices, and private sector facilities throughout the nation. These sources of expertise, together with the existing programs in several national laboratories and military facilities, should be integral components of the coordinated national effort recommended above, to assist with developing local and regional models that are optimized for the topography and seasonal weather patterns in vulnerable areas.
  • Urban field programs and wind-tunnel urban simulations should be conducted to allow for the testing, evaluation, and development of existing and new modeling systems (both meteorological and dispersion models).
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