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2
User Needs
This report assesses the needs for improving our ability to track and predict the
atmospheric transport of chemical, biological, or nuclear (C/B/N) atmospheric
releases. These needs are defined in terms of the various communities who must
respond to such threats and their counterterrorism objectives and decision-support time
frames. Different user communities establish and prioritize their needs differently. By
identifying end user requirements, the committee has attempted to focus on the practical
application and implementation opportunities for atmospheric modeling and observa-
tional tools. The broad range of counterterrorism activities is divided into the areas of
preparedness (which, in turn, includes intelligence and threat assessment, preparedness
planning, prevention anclprotection), response, and recovery and ana11lysis. Each of these
stages places a different set of constraints and requirements on observational and
modeling needs (Appendix D). Response and recovery needs are further subdivided
according to the diversity of responders, their particular responsibilities, and the time
scales associated with their various roles.
PREPAREDNESS
Inte1/~1/tigence and threat assessment involves consideration of the capabilities and
attack risks linked with any potential terrorist organization, from individuals acting alone
to organized groups or even hostile nation-states. Atmospheric transport modeling may
contribute in several ways to this expansive effort. The historical precedent of nuclear
weapons test monitoring attests to the usefulness of accurate atmospheric modeling
studies as a means of retracing the transport of airborne C/B/N agents. Transport mode-
ling may also assist in determining sensor sensitivity and sampling requirements as well
as preferential locations for monitoring (either systematically for wide coverage or
specifically for suspected terrorist activities). Similarly, such models may be used to
assess the risk associated with any number of hypothetical threat scenarios against
assumed targets.
Atmospheric transport modeling tools can be used to help determine the time,
location, and magnitude of releases after they have occurred. An example of this type of
1
~1
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ATMOSPHERIC DISPERSION OF HAZARDOUS MATERIAL RELEASES
event was the tracking of radioisotopes released from the Chernobyl reactor accident.
For these "hindcast" activities, particularly for cases in which extended time is available
for after-the-fact analysis, existing large-scale transport models have provided useful
support to the intelligence community. However, improved atmospheric dispersion
modeling could contribute substantively to the design of enhanced monitoring systems,
for instance, to help determine requirements for monitor location and spacing and sensor
measurement sensitivities. Assessment of conjectured threats against known potential
targets (such as nuclear power plants) also seems to be served satisfactorily by existing
atmospheric dispersion models. For these cases, predictions of average atmospheric
behavior and likely variations around mean dispersion seem adequate for general threat
assessment and training purposes. However, as the need for higher temporal and spatial
resolution mapping becomes greater for example, with regard to threat assessment in
urban environments and complex topographies current transport models are not yet
sufficiently useful. Furthermore, given that local-scale transport is affected by dynamic
weather conditions, such models require continuous updating with observations or output
from meteorological models.
Preparedness planning is a natural extension of counterterrorism threat assessment,
and it complements existing emergency planning for accidental atmospheric releases of
harmful agents. This particularly is the case for facilities such as petrochemical and
nuclear plants that are known to be potential sites of hazardous releases and that may also
be terrorist targets. Emergency responders generally have well-established plans and
contingency options for reacting quickly to events involving atmospheric releases
(whether accidental or purposely induced) from such pre-identified facilities. In many
cases, they have trained regularly against such threats. Existing atmospheric transport
models appear to be useful for site-specific planning and training needs and likewise for
event-specific preparation and planning activities, such as those associated with major
entertainment, sports, or other public events (e.g., the Super Bowl, a presidential inaugu-
ration).
Protection and prevention generally involve the anticipation and interdiction of
suspected terrorist activity by responsible authorities before a terrorist attack occurs and,
specifically, before the release of C/B/N agents into the atmosphere. Although successful
interdiction implies that an atmospheric release of hazardous material has been avoided,
atmospheric transport modeling can and has been used to assist in decision making for
the allocation of monitoring resources and deployment of field personnel. For example,
during the Salt Lake City Olympics (Appendix H), prevailing weather patterns and
predicted atmospheric transport effects were used by protection forces to identify areas of
heightened vulnerability or risk and, correspondingly, to help allocate available moni-
toring resources for maximum coverage and effectiveness. While improved transport
modeling would be useful in the case of real emergency events, existing models have
proven useful for satisfying these preventive resource-allocation and training needs.
RESPONSE
Once hazardous agents have been released into the atmosphere, a series of emer-
gency response actions will occur, carried out by a variety of specialized emergency
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USER NEEDS
these users and
13
response personnel working in concert across several overlapping time scales. Each of
time scales places different needs-based requirements on tools for
tracking the atmospheric release. For the purpose of providing an assessment framework,
actions and user needs are defined on three time scales:
1. Immediate first response (0-2 hours)
2. Early response (generally 2-12 hours)
3. Sustained response support (generally greater than 12 hours)
Response to events also is affected by knowledge of the release source term; for
instance, one may have a likely known source agent (such as a nuclear power plant), an
unknown source term (such as an undetermined biotoxin release), or a quasi-known
source (such as a chemical explosion with visible plume but of uncertain or mixed
composition).
"First responder" is a term generally used to describe the fire and rescue, medical
services, and law enforcement personnel responding to an emergency over the first
several hours (Appendix D). For the purposes of this study, the committee defines first
responders as those individuals who are first to report and arrive at the scene of an
emergency, often within minutes after the events occur. These individuals frequently will
be the ones who report the emergency to local and state emergency response managers,
provide an initial assessment of its nature and magnitude, and direct short-term response
reaction over the first few tens of minutes of an event. Their highest priority is to protect
the public and to care for the injured. Beyond whatever benefits might be derived from
preparatory training exercises, there may be little opportunity for atmospheric dispersion
modeling to assist in meeting first responders' needs in the immediate aftermath of an
actual terrorist attack. In contrast, real-time observations of wind, precipitation, and so
forth, may play a major role in immediate decision-making.
Dispersion modelers must understand the role and capabilities of these first
responders; they serve as the initial data collection interface on what has happened, often
being asked to provide subjective characterization of the release events so as to best
determine follow-on emergency responses over the next few hours. Their limited
descriptive input may be the only information available for the first quick-Iook atmo-
spheric model assessment of likely event consequences.
The early emergency response team will move into action upon receiving initial
reports of an event (or a series of related events). This response team may be part of
larger emergency management teams that are state, county, or municipality based,
depending on the event location. Emergency response protocol establishes the official
primacy of local authorities in dealing with such emergencies, although state, regional,
and federal resources may be actively engaged in providing various degrees of
supplemental support. The experience and training of these early emergency response
teams is especially crucial during these chaotic first few hours following a release. In
larger population centers, a member of the emergency response team likely will have
some level of experience and capability in using very simple transport modeling tools
(such as CAMEO/ALOHA Computer-Aided Management of Emergency Operations-
Areal Locations of Hazardous Atmospheres], discussed in Chapter 4~. In more rural or
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ATMOSPHERIC DISPERSION OF HAZARDOUS MATERIAL RELEASES
less prepared locales or for the use of more sophisticated models, emergency response
teams may need more complete advisory support from a national or regional atmospheric
modeling center.
The initial response plan over the first several hours of an event typically will
include execution of a quick-Iook atmospheric transport model prediction. This model
may have very limited access to real-time atmospheric data and information about the
hazard source (in terms of injection dynamics, aerosol size and composition, and poten-
tial lethal dosages. Over the next few hours, as additional real-time data and source term
information become available, modeling predictions will become increasingly accurate
and specific.
It is essential that the atmospheric modeling results support the decision-making
needs of this early responder community (Appendix D). Within the first few tens of
minutes to several hours, emergency managers are working to resolve several critical
issues, including a quick decision on the type of personal protective equipment and
devices to be used to ensure the safety of the on-site responders (police, fire, medical
personnel) and a decision as to evacuate or to shelter-in-place civilian populations in
event impact areas. Over the next several to 12 hours, the emergency response team will
be working to refine these evaluations and predictions, to assess the downwind impact
zone in accordance with atmospheric transport and dispersion models so as to provide
timely warning to threatened downwind populations, and to provide support for recovery
efforts involving response personnel entering or re-entering affected areas. (Box 2.1.)
The time beyond roughly 12 hours following an event typically represents the
transition period from crisis management to some degree of sustained managed response
and the beginning of recovery activities. Of course, for long-lived chemical, biological,
or nuclear releases, the response and recovery activities overlap significantly. As trans-
port and dispersion models are supported by a more complete database of detailed atmo-
~ Dosage is the dose expressed as a function of time and the organism being dosed; for example, it
can be expressed as milligrams per kilogram of body weight per day (ma kg-i days.
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USER NEEDS
15
spheric observations and contaminant monitoring measurements, the response tasks also
become correspondingly precise in terms of determining requirements for personal pro-
tective equipment, exposures estimates across finer spatial resolutions, and conesquence
assessment.
Especially during this period, the modeling support team must be familiar with
non-technical aspects of the emergency management team's decision-making process.
The decision makers not only need access to the best atmospheric transport predictions,
but they also require reasonable estimates of the variability and confidence levels of
results. They typically must reach some balance between safety concerns under a worst-
case lethality scenario and the expense and other consequences accompanying over-
reaction to such a scenario. In addition, while model output generally can be no better
than data input, even the most sophisticated emergency response team members caution
that models requiring input data from the end user that the user does not understand or
cannot immediately provide will result in the model's being quickly discarded. Model
providers must work diligently to assume the perspective of the end user by always
asking, "What is needed, and how much is enough?" They also must recognize that the
emergency responder often will have to reach a decision based upon whatever incomplete
or imprecise information is available at the time. Transport modeling must be designed to
provide the best support available even under the most difficult and limiting
circumstances.
Finally, the emergency response team does not enjoy the luxury of a posterior)
statistical analysis and comparison of differences accompanying competing atmospheric
models. They need definitive support without excessive complexity, caveat, or
confusion to directly address the decisions they must make, on the timetable on which
they must make them. The burden of interfacing the atmospheric transport models to the
decision-making needs of the emergency response team generally must fall upon the
modeling community. A regular series of"tabletop," functional, and full-scale event
simulation exercises (Box 2.2), bringing together emergency response teams and
members of the atmospheric modeling and observational communities, would greatly
benefit all parties involved and facilitate the development of a common set of data
interface and decision support protocols.
The emergency responders who participated in the workshop uniformly agreed that
in real emergency events, the atmospheric modeling community should speak with a
single voice. There is general dissatisfaction with the large number of seemingly com-
petitive atmospheric transport models and services now supported by various agencies.
Conversely, there is wide agreement on the value of having a single point of contact
(preferably reachable through a 1-800 phone number) that can provide a clearinghouse of
information about the available observational and modeling support and immediately
connect first responders and emergency managers to the appropriate centers of technical
2 Exposure is the concentration, amount, or intensity of a particular agent that reaches the target
population, usually expressed in numerical terms of substance concentration, duration, and
frequency (for chemical agents and micro-organisms) or intensity (for physical agents such as
radiation).
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ATMOSPHERIC DISPERSION OF HAZARDOUS MATERIAL RELEASES
expertise. Of course, the usefulness of such a system will first require a comprehensive
understanding of customer needs and the capabilities of various existing dispersion
modeling centers. Such a resource may be especially valuable in smaller cities, towns,
and rural areas, where first responders (who are often volunteer firefighters) may have
little information about how to obtain immediate assistance.
Additionally, because of conflicting concerns over liability for decisions made and
actions undertaken during the difficult first few hours following a terrorist attack, many
in the responder community urge that atmospheric dispersion modeling and prediction be
managed as a federal service.
As discussed in greater detail in Chapter 4, most models predict the average
dispersion (over a large number of realizations of the given situation) and not the event-
to-event variability about that average. As a result, even a good atmospheric transport
model may have single-event errors of more than a factor of ten. In determining evacu-
ation zones based upon estimates of lethality dosage, fluctuations of this magnitude
represent substantial human health risks. It is important that atmospheric models applied
to individual atmospheric releases provide predictions with clearly stated uncertainties.
There is an opportunity to improve the overall understanding of atmospheric
transport and dispersion modeling by advancing research in this field and by syner-
gistically combining the different techniques and approaches, as described later in this
report. The subtleties of choosing among models, and determining how they are to work
together under changing atmospheric conditions and output needs, must remain the chal-
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USER NEEDS
17
lenge of a nationally coordinated effort and not be left as a responsibility of emergency
response managers in the field. These end users have requested modeling outputs that
offer simplicity, repeatability, scalability, and timeliness. With appropriate attention, the
committee believes atmospheric transport and dispersion modeling can meet these needs
and substantially enhance our national emergency response capability.
RECOVERY AND ANALYSIS
There is no specific timetable that establishes when recovery from a harmful
atmospheric release begins. Because of the nature of transport, event recovery may be
well underway in areas initially affected by the release as the hazardous agents reach new
locations downwind. Atmospheric transport models should provide accurate prediction,
warning, and exposure assessments for these later-time concerns (Box 2.3~.
During the recovery period, health care workers will become much more active in
reaching and caring for the injured. Atmospheric modeling predictions of exposure
expectations will help the health care community assess the size of the needed response
and the accumulation and allocation of necessary resources to deal with the events. Also,
during the necessary triage of incapacitated and ambulatory injured, model predictions of
exposure may influence the interpretation of symptoms and treatment modalities.
Emergency response workers will continue to monitor contaminant exposure levels
and confirm when an area is safe to reenter, prescribing personal protective equipment as
a function of exposure risk. Modeling efforts may prove especially valuable in
highlighting possible geographic or structural areas capable of capturing and maintaining
dangerous concentration levels of persistent hazardous agents. At some point, those who
have been evacuated from their communities will be allowed to return home. The timing
of such actions will depend in large part on the decontamination needs of the built
environment, including likely contaminant collection sites such as storm drains, sanitary
sewers, and building basements. In some cases, long-term environmental monitoring and
restoration of natural lands, plants and animals, and waterways may become necessary.
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ATMOSPHERIC DISPERSION OF HAZARDOUS MATERIAL RELEASES
KEY FINDINGS AND RECOMMENDATIONS
Atmospheric observations and dispersion models must interface seamIessly with
the needs of emergency responders. 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. Conversely, dispersion modelers and meteorologists would benefit from learning
how nowcasts and forecasts are used in emergency response situations. "Tabletop" (i.e.,
roundtable discussion and planning) event simulation exercises should be convened
regularly to bring together emergency response teams and members of the
atmospheric modeling and observational communities to help establish and exercise
a common set of data interface and decision support protocols.
Emergency responders face a confusing array of seemingly competitive atmo-
spheric 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. A single
federal point of contact should be established (such as a 1-X00 phone number) that
could be used to connect emergency responders across the country to appropriate
dispersion modeling centers for immediate assistance.
Emergency managers need a realistic understanding of the bounds on the uncer-
tainties of dispersion model predictions. Dispersion model predictions of the
concentrations for a given release need to be accompanied by a prediction of the event-to-
event variability in that situation. Dispersion modelers should use ensemble modeling
or other approaches that quantify not only the average downwind concentration
distribution in a given situation, which is interpretable as the most likely outcome,
but also the event-to-event variability to be expected. The specific formats of the
information presented should be developed in close collaboration with users of this
information.
Representative terms from entire chapter:
atmospheric transport
