Testimony 

Before the House Subcommittee on 

National Security, Emerging Threats, and 

International Relations, Committee on 

Government Reform

United States General Accounting Office 

GAO

For Release on Delivery 

Expected at 1:00 p.m. EDT 

Monday, June 2, 2003 GULF WAR ILLNESSES

Preliminary Assessment of 

DOD Plume Modeling for 

U.S. Troops’ Exposure to 

Chemical Agents 

Statement of Keith Rhodes, Chief Technologist 

Center for Technology and Engineering, Applied Research 

 and Methods 

GAO-03-833T 
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DOD’s conclusion as to the extent of U.S. troops’ exposure is highly 

questionable because DOD and CIA plume modeling results are not 

reliable. In general, modeling is never precise enough to draw definitive 

conclusions, and DOD did not have accurate information on source term 

(such as the quantity and purity—concentration—of the agent) and 

meteorological conditions (such as the wind and weather patterns), 

essential to valid modeling. In particular, the models DOD selected were 

not fully developed and validated for long-range environmental fallout; 

the source term assumptions were not accurate; the plume height was 

underestimated; the modeling only considered the effects on health of a 

single bombing; field-testing at Dugway Proving Ground did not 

realistically simulate the actual bombing conditions; and divergence in 

results among models. 

DOD’s conclusion, based on the findings of epidemiological studies--that 

there was no significant difference between rates of illness for exposed 

versus not exposed troops--is not valid. In the epidemiological studies, 

the results of DOD’s flawed modeling served as a key criterion for 

determining the exposure classification—exposed versus not exposed to 

chemical agents—of the troops. Such misclassification is a serious 

problem that can have two types of effects: First, if misclassification 

affects both comparison groups equally (nondifferential classification-- 

equally in the exposed and unexposed groups), it may water down the 

results so that important associations are missed. Second, if 

misclassification affects one group more than the other (differential 

misclassification), it may introduce bias that obscures important 

associations or creates false associations. Consequently, the 

misclassification in the studies resulted in confounding—that is, 

distorting—the results, making the conclusion invalid. 

Of the approximately 700,000 

veterans of the Persian Gulf War, 

many have undiagnosed illnesses. 

The Department of Defense (DOD) 

and the Central Intelligence Agency 

(CIA) have concluded, using 

computer plume modeling, that no 

U.S. troops were exposed to 

hazardous substances because 

plumes—clouds of chemical 

warfare agents—could not have 

reached the troops. GAO was asked 

to assess DOD and CIA plume 

modeling to determine whether 

DOD’s conclusions could be 

supported. GAO’s final assessment 

will be reported at a later date. 

www.gao.gov/cgi-bin/getrpt?GAO-03-833T.

To view the full product, including the scope 

and methodology, click on the link above. 

For more information, contact Keith Rhodes 

at (202) 512-6412 or rhodesk@gao.gov. 

Highlights of GAO-03-833T, a testimony 

before the House Subcommittee on 

National Security, Emerging Threats, and 

International Relations, Committee on 

Government Reform 

June 2, 2003

GULF WAR ILLNESSES

PRELIMINARY ASSESSMENT OF DOD 

PLUME MODELING FOR U.S. TROOPS’ 

EXPOSURE TO CHEMICAL AGENTS
Page 1 GAO-03-833T 

Mr. Chairman and Members of the Subcommittee: 

We are pleased to be here today to present our preliminary assessment of 

the plume modeling conducted by DOD and CIA to determine the number 

of U.S. troops that might have been exposed to the release of chemical 

warfare agents during the Gulf War in 1990. We will report the final results 

of this study at a later date. 

As you know, many of the approximately 700,000 veterans of the Persian 

Gulf War have undiagnosed illnesses since the war’s end in 1991. Some 

fear they are suffering from chronic disabling conditions because of 

wartime exposures to vaccines, as well as chemical warfare agents, 

pesticides, and other hazardous substances with known or suspected 

adverse health effects. Available bomb damage assessments during the 

war showed that of the 21 sites bombed in Iraq—categorized by 

intelligence agencies as nuclear, biological, or chemical facilities—16 had 

been destroyed by bombing. Some of these sites were near the areas 

where U.S. troops were located. 

When the issue of the possible exposure of troops to low levels of 

chemical warfare agents was first raised, during the summer of 1993, the 

Department of Defense (DOD) and the Central Intelligence Agency (CIA) 

concluded that no U.S. troops were exposed because (1) there were no 

forward-deployed chemical warfare agent munitions and (2) plumes—

clouds of chemical warfare agents—from the bombing that destroyed the 

chemical facilities could not have reached the troops. 

This position was maintained until 1996, when it became known that U.S. 

troops destroyed a stockpile of chemical munitions after the Gulf War in 

1991, at a forward-deployed site, Khamisiyah, in Iraq. Consequently, DOD 

and the CIA made several modeling efforts to estimate the number of 

troops that might have been potentially exposed to chemical warfare 

agents. But recognizing that actual data on the source term—such as the 

quantity and the purity (concentration) of the agent—and meteorological 

conditions—such as the wind and the weather patterns—were not 

available,1

 DOD and CIA conducted field-testing and modeling of bombing 

 1

Observations were few because Iraq stopped reporting weather station measurement 

information to the World Meteorological Organization in 1981. As a result, data on the 

meteorological conditions during the Gulf War were sparse. The only data that were 

available were for the surface wind observation site, 80 to 90 kilometers away, and the 

upper atmospheric site, about 200 kilometers away. 
Page 2 GAO-03-833T 

sites at Khamisiyah, in 1996 and 1997, to determine the size and path of the 

plume, as well as the number of U.S. troops exposed to the plume. During 

these initial modeling efforts, DOD asked the Department of Energy’s 

Lawrence Livermore National Laboratories (LLNL) to also conduct 

modeling. In 1997, DOD and CIA also combined a number of their own 

individual modeling efforts into a composite and conducted additional 

plume modeling of the bombing sites at Al Muthanna, Muhammadiyat, and 

Ukhaydir. Subsequently, in 2000, DOD revised its modeling of Khamisiyah. 

In our testimony today, at your request, my remarks will focus on our 

preliminary findings of DOD and CIA plume modeling during the Gulf War. 

Specifically, I will address the validity of the following DOD conclusions: 

• based on DOD plume modeling efforts, that the extent to which U.S. 

troops were exposed was minimal and 

• based on findings of government-funded epidemiological studies, that 

there was no significant difference as to the rate of illness between 

troops that were exposed to chemical warfare agents versus those not 

exposed. 

Our work thus far has involved interviews with agency officials and 

experts in this area, reviews of relevant documents and literature, and a 

review of DOD’s methodology and analyses of plume modeling. Our work 

has been performed in accordance with generally accepted government 

auditing standards. 

DOD’s conclusion as to the extent of U.S. troops’ exposure—based on 

DOD and CIA plume modeling—is highly questionable because the results 

of the modeling are unreliable. In general, modeling is never precise 

enough to draw definitive conclusions, and DOD did not have accurate 

information on source term and meteorological conditions. 

We have several reasons for this assessment: First, DOD selected models 

that were not fully developed and validated for modeling long-range 

environmental fallout. Second, some of the assumptions regarding the 

source term data used in the modeling were not accurate—based on 

incomplete information, data that were not validated, and testing that did 

not realistically simulate the actual conditions at Khamisiyah. For 

example, the CIA calculated the agent purity in 1991 to be 50 percent at 

Khamisiyah, but 18 percent at Al Muthanna and about 15 percent at 

Muhammadiyat. The CIA did not independently validate or establish agent 

Summary 
Page 3 GAO-03-833T 

purity levels based on empirically driven analyses, and relied on UNSCOM 

reporting for these rates. This assessment of the agent purity rate at Al 

Muthanna was questioned by a DOD official. We plan to examine the 

validity of the methodology used to calculated the rate of degradation. 

Third, the plume height was underestimated, which resulted in discounting 

the impact of certain meteorological conditions, such as high-speed winds 

at nighttime, when many of the bombings occurred. This would have a 

dramatic effect on the distance the chemical agent traveled. Moreover, 

according to an internal DOD memo, plume height in one case at Al 

Muthanna was arbitrarily determined by a DOD official to be 10 meters. At 

Muhammadiyat and Ukhaydir, plume heights were estimated to be the 

height of the munition or the munition stack. However, independent fieldtesting demonstrated that a single 1,000-pound bomb would create plume 

height in excess of 400 meters above the ground. Fourth, DOD, in its 

modeling, only considered the effect of a single bombing of the sites on 

the health of the U.S. troops. But DOD did not take into account the 

cumulative effects of repeated bombings of the sites on troops’ health. 

Fifth, post-war field-testing done at Dugway Proving Ground, to estimate 

the source term data and plume height, did not realistically simulate the 

actual conditions of bombings at any of the sites. The simulation occurred 

under conditions that were not comparable to those that existed at 

Khamisiyah. For example, there were differing seasonal and 

meteorological conditions, differences in rocket construction, and lesser 

quantities of rockets. These differences result in multi-variable uncertainty 

that cannot be resolved. Finally, there was a great divergence among the 

various models DOD selected with regard to the size and path of the plume 

and the extent to which troops were exposed. Combining the results of 

various models masked the highly divergent predictions among the 

individual models regarding the size and path of the plume. The results of 

LLNL model which showed the largest area of coverage were disregarded 

and not included in the composite model. 

DOD’s conclusion that there were no significant differences in the rate of 

illness between exposed and non-exposed troops is questionnable. DOD 

based this conclusion on the findings of epidemiological studies, in which 

DOD modeling was flawed. In addition, the modeling results served as a 

key criterion for classifying troops that were ill and had been exposed 

compared with troops that were ill and determined not to have been 

exposed. However, the troops classified as non-exposed might have been 

exposed. Such misclassification is a serious problem that can have two 

types of effects. First, if misclassification affects both comparison groups 

equally (non-differential classification—equally in the exposed and 
Page 4 GAO-03-833T 

unexposed groups), it may water down the results so that important 

associations are missed. Second, if misclassification affects one group 

more than the other (differential misclassification), it may introduce bias 

that obscures important associations or creates false associations. 

Consequently, the misclassification in the studies resulted in 

confounding—that is, distorting—the results. 

In March 1991, after the conclusion of the Gulf War, U.S. Army demolition 

units destroyed munitions at the Khamisiyah storage site—which included 

a bunker and an open pit—in southeastern Iraq. Later, through inspections 

conducted by the United Nations Special Commission (UNSCOM) in Iraq, 

it was discovered that hundreds of 122-millimeter rockets destroyed at 

Khamisiyah contained the nerve agents sarin and cyclosarin. U.S. and 

coalition forces also bombed many other known or suspected Iraqi 

chemical warfare research, materiel, storage, and production sites. 

According to DOD and the CIA, coalition air strikes resulted in damage to 

filled chemical munitions at only two facilities in central Iraq, Al Muthanna 

bunker 2 and Muhammadiyat, and at the Ukhaydir ammunition storage 

depot in southern Iraq. At Muhammadiyat, munitions containing an 

estimated 2.9 metric tons of sarin and cyclosarin and 15 metric tons of the 

chemical agent mustard were damaged during the air strikes. At Al 

Muthanna, munitions containing an estimated 17 metric tons of sarin and 

cyclosarin were damaged during the air strikes. 

According to DOD, the U.S. Government did not immediately make the 

connection between the chemical munitions found by UNSCOM at 

Khamisiyah and U.S. demolition bombings there. However, in 1996, 

concerns raised by the Presidential Advisory Committee on Gulf War 

Illnesses prompted the CIA to examine this issue.2

 The CIA contracted 

with the Science Applications International Corporation (SAIC) to conduct 

the initial analysis and modeling of the bombing of chemical munitions in 

Khamisiyah bunker 73. The CIA’s first report, published in August 1996, 

modeled the potential release of agents from bunker 73. The CIA and DOD 

jointly published a second report in September 1997. In this report, they 

combined the results of five different dispersions (for example, the size 

and path of the plume) and meteorological models to determine the extent 

of the plume from bombing of chemical munitions in Khamisiyah. In 2000, 

 2

The Presidential Advisory Committee on Gulf War Veterans’ Illnesses was a panel 

established in August 1995 to provide oversight to Gulf War illnesses investigations. 

Background 
Page 5 GAO-03-833T 

DOD published the results of a new modeling of the Khamisiyah site, using 

updated CIA source assessments and revising the hazard area. 

In chemical plume modeling, simulations are produced that recreate or 

predict the size and path of the plume, including the potential hazard area, 

and the potential effect on the health of the exposed population. Modeling 

requires accurate information on 

• source term characteristics, properties (for example, vapor pressure, 

flash point, size of particles, persistency, and toxicity information), and 

rate of the agent release; 

• temporal characteristics of the period of release (for example, whether 

the initial release of chemical agent occurred during daylight hours 

when it might rapidly disperse into the surface air or at night when 

differing dispersion patterns would exist depending on terrain and the 

height of the release); 

• accurate collection of data that drive the meteorological models, such 

as temperature, humidity, barometric pressure, dew point, wind 

velocity and direction at varying altitudes, and other related 

measurements of weather conditions during the modeled period; 

• data from global weather models to simulate large-scale weather 

patterns and from regional and localized weather models to simulate 

the weather in the area of the chemical agent release and throughout 

the area of dispersion; and 

• information regarding the location of potentially exposed populations, 

animals, crops or other assets that may be affected by releases of the 

agent. 

The modeling of various chemical agent releases during the 1991 Persian 

Gulf War included global-scale models, such as the National Centers for 

Environmental Prediction Global Data Assimilation System (GDAS) and 

the Naval Operational Global Atmospheric Prediction System (NOGAPS). 

Regional and local weather models used included the Coupled OceanAtmosphere Mesoscale Prediction System (COAMPS), the Operational 

Multiscale Environment Model with Grid Adaptivity (OMEGA), and the 

Mesoscale Model Version 5 (MM5). 

Transport and diffusion models (often simply called dispersion models) 

were also used. They project both the path of the chemical agents after 

Information Needed for 

Modeling the Effects of 

Chemical Warfare Agents

Types of Models Used 
Page 6 GAO-03-833T 

release and the degree of hazard posed by the agents. For example, the 

modeling of various releases during the 1991 Gulf War included dispersion 

models, such as the Second-order Closure Integrated Puff (SCIPUFF) 

model along with its Hazard Prediction and Assessment Capability (HPAC) 

component; the Vapor, Liquid, and Solid Tracking (VLSTRACK) model; the 

Non-Uniform Simple Surface Evaporation Model (NUSSE); and the 

Atmospheric Dispersion by Particle-in-Cell (ADPIC) model. 

DOD’s conclusion as to the extent of U.S. troops’ exposure—based on 

DOD and CIA plume modeling—is highly questionable because the results 

of the modeling are unreliable. The modeling conducted was not precise 

enough to draw definitive conclusions regarding the size and path of the 

plume. We found six reasons to question the conclusions: First, the models 

selected were not fully developed and validated. Second, the assumptions 

regarding the source term used in the modeling were not accurate. Third, 

the plume height was underestimated. Fourth, DOD modeling only 

considered the effects of a single bomb on health. Fifth, post-war field 

testing done at Dugway Proving Ground did not realistically simulate the 

actual conditions of bombing at any site. And, finally, there was a great 

divergence among the various models DOD selected with regard to the 

size and path of the plume. 

DOD and CIA officials selected in-house models for use in plume modeling 

(see appendix 1). In the case of Khamisiyah and other sites, DOD 

models—such as the VLSTRACK and HPAC/SCIPUFF dispersion models—

were not fully developed and validated for environmental fallout at the 

time of their selection. In particular, these models were not appropriate 

for long-range tracking of chemical agents. 

VLSTRACK was developed primarily as a tactical decision aid for 

predicting hazards resulting from the release of chemical and biological 

agents in a military environment. Modeling experts at the Naval Surface 

Center told us that the two-month DOD panel reanalysis and modeling was 

a developmental effort because existing models did not have the capability 

to perform the required projections. Considerations of potential illness 

from low-level exposure to chemical agents resulting from nerve and 

blister agents accidentally released in Iraq required extensive extensions 

and modifications to some of the methodology in VLSTRACK. 

HPAC was developed jointly by the Defense Intelligence Agency and the 

then Defense Special Weapons Agency (now known as DTRA) and was 

specifically tailored to do counterproliferation contingency planning. In a 

DOD’s Conclusions 

Regarding the Extent of 

Exposure of U.S. Troops 

Are Highly Questionable 

The Models Selected Were Not 

Fully Developed and Validated 
Page 7 GAO-03-833T 

1998 scientific review and evaluation of SCIPUFF, which is an integral part 

of HPAC, the National Oceanic and Atmospheric Administration’s 

(NOAA’s) Air Resources Laboratory stated that SCIPUFF is probably 

better suited for short-range (about 10 kilometers) dispersion applications 

rather than for long-range transport modeling. Among the limitations 

cautioned regarding the use of the HPAC model are that does not provide 

a definitive answer due to uncertainties about transport, location, and 

weather. 

In addition, based on the DOD modeling effort, it is evident that a group 

using the VLSTRACK model might receive a significantly different 

prediction from that of a group using the HPAC model. And neither of 

these models has sufficient fidelity—that is, reliability—to permit the 

conclusion that the actual hazard area—that is, path of the plume—is 

confined to the predicted hazard area. In a September 1998 memo, the 

Deputy to the Secretary of Defense for Counterproliferation and 

Chemical/Biological Defense cited a DOD panel study team, which found 

that the VLSTRACK and HPAC models generate hazard predictions that 

are significantly different from each other. The memo noted, “This 

occurred even when the source terms and weather inputs are as simple 

and as identical as possible. In operational deployment, the average model 

user could obtain different answers for the same threat.” 

With regard to meteorological models, according to a 1997 memo from the 

Director of NOAA’s Air Resources Laboratory to DOD, the selection of 

models was dominated by in-house, that is, DOD, models that were not 

well known outside of DOD. The Director noted that there were three 

mainstream mesoscale models available and well accepted for deriving 

site-specific flow conditions from large-scale meteorological information: 

MM5, RAMS, and Eta. At that time, OMEGA and COAMPS were too new 

and not well accepted outside of DOD circles. OMEGA was still under 

development, and a Peer Review Panel on the 1997 Khamisiyah modeling 

reported that there were major problems with the OMEGA model. For 

example, there were physically impossible aspects to the OMEGA model 

solutions and major errors in its simulations. For the analysis done for 

Khamisiyah and Al Muthanna, a DOD technical review panel found that 

OMEGA consistently under-predicted surface wind speeds by a factor of 2 

to 3 when compared with actual observations collected at five World 

Meteorological stations in the area. 

There were significant uncertainties in the source term used in the plume 

modeling at Khamisiyah. DOD and the CIA made assumptions about the 

source term based on field-testing, intelligence information, imagery, 

The Source Term Assumptions 

Were Not Accurate 
Page 8 GAO-03-833T 

UNSCOM inspections, and Iraqi declarations to UNSCOM. However, these 

assumptions were based on incomplete information, data that were not 

validated, and testing that did not realistically simulate the actual 

conditions at Khamisiyah. 

In its initial modeling of the demolition of chemical munitions at 

Khamisiyah, the CIA did not have accurate and precise information as to 

how rockets with chemical warheads would be affected by open pit 

demolition, compared with bunker demolition. This lack of information 

included the number of rockets, agent purity, and amount of agent 

released in the atmosphere, agent reaction in an open-pit demolition, and 

prevailing meteorological conditions. A DOD panel also found a lack of 

information,3

 that is, substantial uncertainties regarding the number of 

damaged rockets that might have released chemical agents and how fast 

the nerve agents—sarin and cyclosarin, which were mixed together in the 

rockets—were released. Some of these agents may have leaked from 

rockets into the soil or into the wood of the boxes that contained the 

rockets and evaporated over time. The panel also found that the CIA and 

SAIC analyses used what were essentially guesses for the lack of data. For 

example, the numbers of rockets were based on what was known to be 

there before the demolition and what was found by the UNSCOM during 

their inspections, but, according to a DOD panel, the numbers varied by a 

factor of 5 or 6. 

In addition, this panel recognized that meteorological data were limited 

because there were relatively few observations, and these were made far 

from the Khamisiyah site. Observations were few because Iraq stopped 

reporting weather station measurement information to the World 

Meteorological Organization in 1981. As a result, data on the 

meteorological conditions during the Gulf War were sparse. The only data 

that were available were for the surface wind observation site, 80 to 90 

kilometers away, and the upper atmospheric site, about 200 kilometers 

away. The panel also recognized that wind patterns could contain areas of 

bifurcation—lines where winds move in one direction on one side and in 

another direction on another side—which also move over time and are 

different at different altitudes. 

 3

DOD had asked the Institute of Defense Analyses to set up a DOD-funded panel to review 

the modeling. 
Page 9 GAO-03-833T 

Source term assumptions on agents (sarin and cyclosarin) purity 

established for the four sites—Khamisiyah, as well as Al Muthanna, 

Muhammadiyat, and Ukhaydir—differed widely. Discrepancies between 

the Khamisiyah purity data and the Al Muthanna and Muhammadiyat data 

were not adequately resolved. The agents were assumed to be purer in 

February 1991 at Al Muthanna than in January at Muhammadiyat and 

purer still in March at Khamisiyah. In each case, agent purity was a key 

factor in the DOD and CIA methodology for determining the amount of 

agents released. Since the purity of the sarin and cyclosarin was used as a 

factor in calculating the amount of agents released, purity is critical in 

compounding the uncertainty of the modeling. For example, for modeling 

purposes, 10 tons of agent with a purity of 18 percent would be 

represented as only 1.8 tons of agent. The CIA did not independently 

validate or establish agent purity levels based on empirically driven 

analyses, and relied on UNSCOM reporting for these rates. This 

assessment of the agent purity rate at Al Muthanna was questioned by a 

DOD official, who noted in a memo, “Why we use the 18 percent purity 

instead of the 50 percent number available in public sources, and why we 

treat GF like GB when there are documents that mention the higher 

toxicity are not easily deferred with ‘because the CIA says so.’ I think the 

GF vs. GB numbers accepted by the EPA or CDC or whatever is the 

competent authority, but the purity number is problematic.” We plan to 

examine the validity of the methodology used to calculated the rate of 

degradation. 

In addition, according to Iraqi production records obtained by UNSCOM, 

the agent purity at Khamisiyah, in early January 1991, was about 55 

percent. The agent subsequently degraded to 10-percent purity by the time 

laboratory analysis had been completed on samples taken by UNSCOM 

from one of the rockets in October 1991. On the basis of the sample purity 

and indications that the degradation rate for sarin and cyclosarin are 

similar, the CIA assessed that the ratio of sarin to cyclosarin when the 

munitions were blown up in March 1991 was the same as that sampled in 

October 1991—3:1. According to the CIA, assuming a conservative 

exponential degradation of the sarin and cyclosarin, the purity on the date 

of demolition, 2 months after production, was calculated to be about 50 

percent. 

At Al Muthanna, however, where the agent was stored in a bunker, the CIA 

estimated the chemical warfare agent had deteriorated to approximately 

18 percent purity by the time that bunker 2 was destroyed, in early 

February 1991, leaving about 1600 kilograms (1.6 metric tons) of viable 

sarin. The CIA based its estimate on UNSCOM’s analysis of Iraqi purity 
Page 10 GAO-03-833T 

data and supporting information, which stated that the munitions were 

filled with the agent in 1988 and that the maximum purity for the 1988 

agent was 18 percent in 1991. However, this assumption suggests 

knowledge of exact production dates and storage conditions that were not 

established. But UNSCOM and intelligence community reporting about the 

near-wartime capabilities of Iraq suggests that while the sarin produced 

was of poor quality, it had a maximum purity of 60 per cent. 

According to CIA documents, the total amount of agent modeled to have 

been released at Al Muthanna was 1 kg, but, to be conservative, the 

amount released was assumed to be 10 kg. The reasoning given for the low 

amounts discharged was the heat of the explosion. The CIA assessed that 

far less agent would have been released in the Al Muthanna bunker 

because, based on U.S. field-testing using simulated bunkers, heat would 

build up rapidly in Iraqi bunkers made of thick reinforced concrete ceiling 

and walls, thereby destroying most of the agent. However, these bumkers 

were targeted using high explosives, such as Tomahawk missiles and 

laser-guided and non-guided bombs, that detonate and produce 

instantaneous and extreme blast forces and shock and pressure waves, as 

well as heat. While the CIA analysts gave great credibility to the heat, no 

consideration was given to either the blast effects of the munitions or to 

the higher altitude plumes generated with the types of munitions used. 

For Muhammadiyat, DOD also provided details regarding how they 

derived source term characterizations for agent released using test data 

from Dugway Proving Grounds. However, the types of munitions used in 

the testing and, therefore, the resulting effects are not comparable to what 

munitions were actually used and their effects. At Dugway Proving 

Grounds, small explosive charges were placed on boxed rockets; at 

Muhammadiyat, the munitions were targeted using multiple high-explosive 

bombs. Agent purity at Muhammadiyat was estimated at 15 percent. 

Plume heights from the explosions could be significantly higher than the 

plume height assumptions provided for in the modeling of Khamisiyah and 

other Iraqi chemical warfare sites. The plume height data the CIA provided 

for the demolitions at the Khamisiyah pit was 0-100 meters. However, 

neither the DOD nor the CIA conducted testing to establish plume heights 

associated with the bombings of Al Muthanna, Muhammadiyat, or 

Ukhaydir. DOD modelers involved with the modeling efforts told us that 

they did not calculate the plume height or any of the other heat or blast 

effects associated with the bombings of these sites because DOD had 

provided the modelers these data. A modeling expert from the Defense 

Threat Reduction Agency (DTRA) told us that DOD data on plume height 

The Plume Height Was 

Underestimated 
Page 11 GAO-03-833T 

was inconsistent with other test data for the types of facilities bombed. 

The modeling expert cited test studies conducted at White Sands Proving 

Grounds in New Mexico, which demonstrated plume heights would range 

from 300 to 400 meters in height. 

Modeling experts from LLNL who participated only in the initial modeling 

at Khamisiyah also told us, citing studies, that they questioned how the 

plume height was estimated. In a pre-war analysis, LLNL projected that the 

smoke source cloud, immediately following the bombing of Iraqi chemical 

warfare agent facilities, would be characterized by a surface-based plume 

with a 54 meter (177 ft.) horizontal radius and a height of 493 meters (1,617 

ft.). A Sandia Laboratory empirical study, performed in 1969, established a 

power law formula for calculating plume heights attributable to highexplosive detonations (see appendix II). Using this formula, an MK-84 or 

GBU-24 (942.6lb. of high explosives) bomb would generate a plume of 421 

meters. 

DOD applied the same assumptions about the height of the plume at 

Khamisiyah to model other possible chemical releases at the Al Muthanna, 

Muhammadiyat, and Ukhaydir sites. At Muhammadiyat, for example, DOD 

established a release height of 0.5 meters (roughly half the bomb height) 

for nerve agent and a release height of 1.0 meters (roughly half of the 

median height of the various bomb stacks) for blister (mustard) agent 

destroyed at this location. Moreover, according to an internal DOD memo, 

an initial cloud size of 10 meters in both lateral and vertical directions was 

“arbitrarily” established. No efforts were made by DOD to validate these 

estimates by analyzing video images that were available showing some of 

the plume data, particularly those taken from ground level at Khamisiyah, 

were used to project the characteristics of the actual plumes. 

As illustrated by figure 1, disparity in plume height source data could 

result in vastly differing projections regarding how far the plume travels 

and disperses, particularly during nighttime periods when a stable 

(nocturnal) boundary layer emerges. 
Page 12 GAO-03-833T 

Figure 1 Boundary Layer Characteristics 

As also shown in figure 1, above the surface layer, in the stable boundary 

layer, the winds often accelerate to higher speeds, in a phenomenon that is 

called the low-level or nocturnal jet. At altitudes on the order of 200 

meters above the ground, winds may reach 10-30 meters per second (22-

67.5 miles per hour) in the nocturnal jet. Higher plumes than those 

postulated by DOD, coupled with this phenomenon, could result in the 

rapid transport of chemical agents until disturbed by turbulence or the 

return of the mixed layer sometime after dawn. However, this possibility 

was not taken into consideration in any of the modeling performed. 

Consequently, the modeling may have resulted in underestimating the 

extent of plume coverage. (For a detailed discussion of this issue, see 

appendix II.) 

In addition, plume geometry associated with high-explosive discharges 

shows that the majority of the mass of the plume is located toward the 

higher altitudes, suggesting that the majority of the mass of the plume 

would move to higher altitues where they might be transported by these 

higher speed winds (see appendix III).

Iraqi chemical warfare facilities were bombed on several occasions, but 

DOD and CIA modeling did not reflect the cumulative effects of these 

repeated bombings on the amounts of agents released and on the health of 

DOD Modeling Only 

Considered the Effects of a 

Single Bombing on Health 

Cloud Layer

2000 

1000 

Convective

Mixed Layer

Surface Layer 

Noon Sunset Midnight

Surface Layer

Local Time

Height (Meters)

Sunrise Noon

S1 S2 S3 S4 S5 S6 

0

Entrainment Zone

Entrainment Zone

Capping Inversion

Residual Layer Mixed

Layer

Surface Layer

Stable (Nocturnal) Boundary Layer

Free Atmosphere 

Source: Roland B. Stull, An Introduction to Boundary Layer Meteorology, (Boston, MA: Klumer Academic Publishers, 1988), p. 11.
Page 13 GAO-03-833T 

troops. For example, there were 17 distinct coalition air strikes on the 

Muhammadiyat ammunition storage depot. While modeling was requested 

for the duration of 72 hours after the chemical release for Khamisiyah, 

DOD used only a 24-hour duration for its modeling of the bombing of 

Muhammadiyat. This was because at this site, unlike at others, DOD made 

the assumption that all of the nerve agent was released at one time and 

therefore modeled each air strike as if it was the only strike that caused a 

release. According to DOD, each model produced a freeze frame of the 

largest hazard area. The hazard area grows until it reaches its maximum 

size, which the modeling suggests is about 10-12 hours after the release. 

DOD and the CIA also conducted post-war field-testing at Dugway Proving 

Ground to simulate the actual bombing conditions at Khamisiyah to derive 

the source term data for use in modeling. From May 1997 through 

November 1999, the testing center at Dugway Proving Ground conducted 

seven field-testings and two laboratory studies to obtain source term data 

for use in DOD and CIA modeling of Khamisiyah. For testing and 

simulation to be effective, the conditions have to be as close to the actual 

event as possible. However, the testing did not realistically simulate the 

conditions that existed during the demolition of 122-mm chemical-filled 

rockets in Khamisiyah and is therefore of questionable usefulness in 

providing inputs data for the modeling. The simulations took place under 

conditions that were not comparable to those that existed at Khamisiyah. 

During the field-testing, there were differences in seasonal and 

meteorological conditions; in munition crate construction material; in 

rocket construction, including the use of concrete-filled pipes as rocket 

replacements to provide (inert) filler to simulate larger stacks; the fewer 

numbers of rockets (and therefore explosives) in the simulations, which 

may have suppressed a potential chain reaction of explosions; the use of 

agent simulant (rather than real agent); and soil. These differences result 

in multi-variable uncertainty that cannot be resolved. 

For example, the Dugway testing used a small sample of 32 rockets with 

simulant-filled warheads to conduct seven field-testings: five were singlerocket demolitions and two involved multiple-rocket demolitions. One 

multiple-rocket trial demolition used nine functional rockets plus three 

dummy rockets, while the other multiple-rocket trial used 19 functional 

rockets and five dummy rockets. In contrast, at the Khamisiyah pit, stacks 

of 122 mm rockets, estimated to total about 1,250 rockets, were detonated. 

Moreover, Dugway testing officials did not know whether the 122 mm 

rockets used during the field-testings were the same as those at the 

Khamisiyah pit. Dugway officials acknowledged that exploding a larger 

number of rockets would make a significant difference on the testing, and 

Dugway Field-testing Did Not 

Realistically Simulate the 

Actual Bombing Conditions 
Page 14 GAO-03-833T 

aerial bombing with a heavy load would have a far greater effect than was 

the case with the Dugway testing. 

According to DOD and CIA analysts, the type of soil and wood can have a 

significant effect on the dispersion of the agent. However, a Dugway 

testing official told us that evaporation characteristics from the trials and 

models were uncertain. DOD and CIA estimates of the evaporation and 

retention rates of the chemical agent spilled on the soil may not be similar 

to what was actually evaporated from and retained in the pit sand at 

Khamisiyah. This is because while Iraqi soil was available and used in the 

laboratory testing, it was not used during the field-testing. Similarly, DOD 

and the CIA estimates of the amount of spilled agent that evaporated from 

and was retained in wooden crates are suspect because Dugway testing 

officials could not obtain actual wood from the Khamisiyah pit site for 

testing. The aged and possibly damp wood at Khamisiyah would absorb 

less agent than the new wood used at Dugway. DOD and CIA determined 

that only about 32 percent of the agent was released and that most leaked 

into the soil and wood with 18 percent of the leakage becoming part of the 

plume (2 percent through aerosolization and 16 percent through 

evaporation). 

Field-testings were also conducted at a different time of the year and time 

of the day than the actual Khamisiyah pit event. According to Dugway 

officials, testing was done in May and in the early morning hours when 

drainage conditions prevail. The U.S. demolition of the Khamisiyah pit 

took place on March 10th, in the late afternoon during the presence of a 

mixing layer. Other demolitions took place during evening and nighttime 

hours when the stable (nocturnal) boundary layer emerges. 

Despite the uncertainties in approximating the conditions that existed 

even at Khamisiyah, DOD and the CIA used these data not only for the 

Khamisiyah modeling, but also for the modeling of other sites. At all these 

sites, the chemical warfare munitions would have been destroyed by air 

strikes with much greater quantities of high-explosive charges and under 

differing meteorological conditions. 

DOD made no effort to resolve widely divergent modeling results among 

the models selected. Instead, a composite model approach was taken, 

which contributed to, rather than resolved, uncertainty. 

For example, the DOD panel tasked the LLNL to conduct an analysis using 

DOD’s MATHEW meteorological model with the ADPIC dispersion model. 

During LLNL presentations to the DOD panel in November 1996 and 

Divergence in Results among 

the Models 
Page 15 GAO-03-833T 

February 1997, the LLNL provided a 72-hour composite projection, 

assuming an instantaneous release of the contents of 550 rockets 

containing sarin. It shows the plume covering an area extending southsoutheast from the release point to the Persian Gulf, then turning eastward 

at the Gulf coast, and then turning northeast over the Gulf and extending 

northeastward across central Iran. (For a more detailed discussion of this 

topic, see appendix IV.) 

DOD models showed significant differences from the LLNL assessment. In 

contrast to the LLNL modeling simulations, analysis done with the DOD 

models—VLSTRACK with COAMPS meteorological models and 

HPAC/SCIPUFF with OMEGA meteorological forecasting models—

showed the plume from an instantaneous release moving first southerly, 

and then turning to the west-southwest. See appendix V for a 72-hour 

plume overlay of those composite projections published by DOD. 

According to the DOD panel, no effort was made to reconcile the 

differences between the DOD and LLNL modeling efforts. The panel 

determined that the results were so different that it would not be possible 

to choose the most affected areas and which U.S. forces were affected. 

Accordingly, the panel recommended that a composite of the DOD models 

be used to combine the hazard areas predicted by the models. Yet we 

observed that even among the models selected for use by DOD, widely 

differing paths were evident (see appendix VI). 

Assuming that a composite modeling effort is an appropriate methodology, 

a composite projection, including the above projections (DOD and CIA 

composite and LLNL), would encompass a far larger number of forces and 

seriously skew the outcome of any epidemiological studies done thus far, 

as shown in figure 2. 
Page 16 GAO-03-833T 

Figure 2: DOD Composite Projection and Lawrence Livermore National Laboratory Projection 
Page 17 GAO-03-833T 

A clear divergence exists in the predictions of the models. Further 

research was conducted to determine whether there was data available 

that might explain this divergence. As a result of this research, the DOD 

panel concluded that the divergence in the modeling outcomes may be 

explained by a line of diffluence (directional split) in the independently 

modeled 10-mm wind field data near Khamisiyah during the first 2 days of 

the modeling period. The precise location of this line was critical to which 

way the material would be transported by the wind. (See appendix VII for 

an illustration of this diffluence with three different data sets). 

In addition, DTRA officials told us that at the time of the modeling, they 

conducted data-validation runs of the various models against visible 

smoke plumes from the oil well fires in Kuwait; the runs showed a definite 

bias, as shown in figure 3. According to DTRA, this validation could mean 

that the uncertainty involved in using these models could result in an 

angular shift of 10 to 50 degrees to the west. In other words, the actual 

area coverd could be from 10 to 50 degrees to the east of the area 

indicated by the model, meaning that it would cover a different population 

from the one in the model. 

Figure 3: Validation Runs of Various Models 
Page 18 GAO-03-833T 

Given that the DOD modeling was flawed, DOD’s conclusion, from 

epidemiological studies based on this modeling with regard to rate of 

illness among exposed versus not exposed, is questionable. 

Nevertheless, the results of the modeling were used as a basis for 

determining the exposure classification—exposed versus not exposed to 

chemical agents—of the troops in population-based epidemiological 

studies. As we noted in 1997, to ascertain the causes of veterans’ illnesses, 

it is imperative that investigators have valid and reliable information on 

exposure, especially for low-level or intermittent exposures to chemical 

warfare agents.4

 To the extent that veterans are misclassified regarding 

exposure, relationships would be obscured and conclusions would be 

misleading. 

Misclassification of study subjects in the measurement of the variables 

being compared is a well-recognized methodological problem in 

epidemiological studies. Misclassification can have two types of effects. 

First, if misclassification affects both comparison groups equally (nondifferential—equally in the exposed and unexposed groups), it may water 

down the results so that important associations are missed. Second, if 

misclassification affects one group more than the other (differential 

misclassification), it may introduce bias that obscures important 

associations or creates false associations. Consequently, the study 

misclassification resulted in confounding—that is, distorting—the results, 

making the conclusion questionable. 

By combining the results from its individual modeling efforts, which 

showed different areas of coverage, and ignoring the results of the LLNL 

modeling, which showed much larger areas of coverage, DOD potentially 

may have misclassified a large number of troops truly exposed to chemical 

warfare agents in the putatively non-exposed group. If exposure to 

chemical warfare agents truly caused adverse effects resulting in 

increased hospitalization or death, such one-way misclassification would 

tend to obscure the differences in hospitalization or death rates by falsely 

increasing the rates in the putatively non-exposed group while not 

affecting the rates in the exposed group. 

 4

GAO, Gulf War Illnesses: Improved Monitoring of Clinical Progress and Reexamination 

of Research Emphasis Are Needed, (GAO/NSIAD-97-163, June 23, 1997). 

DOD’s Conclusion from 

the Epidemiological 

Studies Is Questionable 
Page 19 GAO-03-833T 

Based on the June 1996 plume modeling, DOD officials initially stated that 

only 300 to 400 troops were exposed to chemical plumes. Based on 

additional modeling, that number was revised to approximately 5000 on 

September 1996; to approximately 20,000 on October 22, 1996; and to 

98,910 on July 23, 1997. DOD 2000 estimates place the number exposed at 

101,752. The number from the October 22, 1997 plume model served as the 

basis for informing approximately 100,000 Gulf War veterans of possible 

exposure. This 1997 plume model was also used as the basis of at least two 

epidemiological studies that were published in peer-reviewed scientific 

journals. 

In 2000 DOD announced that as a result of ongoing scientific analysis, 

DOD’s Directorate for Deployment Health Support developed a new 

computer model that changed the location of the Khamisiyah plume 

footprint. The number of service members potentially exposed remained 

approximately 100,000. The new 2000 model reclassified 32,627 troops as 

unexposed who were previously classified as exposed and classified 

35,771 troops as exposed who were previously classified as unexposed. 

Given the weaknesses in DOD modeling and the inconsistency of data 

set—representing these models—given to different researchers, there can 

be no confidence that the research conclusions based on these models 

have any validity. 

In evaluating the limitations of the plume modeling, we concluded that 

even under the best of the circumstances, the results from the modeling 

cannot be definitive. Plume modeling can allow one to estimate what 

might have happened when chemical warfare agents are released in the 

environments. Mathematical equations are used to predict the activities of 

an actual event, in this case, the direction and extent of the chemical 

warfare agent plume. However, in order to predict precisely, one needs to 

have accurate information on the source term and the meteorological 

conditions. However, DOD did not have accurate information on the 

source term or on meteorological conditions. 

Given these modeling flaws, the DOD modeling results should not form the 

basis for determining the extent of exposure of U.S. troops during the Gulf 

War. The models selected were not fully developed and validated for 

environmental fallout and the assumptions used to provide the input into 

the models exhibited a preferential bias for a particular and limited 

outcome. Yet even under these circumstances, the models failed to 

provide similar conclusions. In addition, many potential exposure events 

were not included. It is likely that if fully developed and validated models 

Conclusions 
Page 20 GAO-03-833T 

and more realistic data for source term were included in the modeling, 

particularly plume height and exposure duration, the exposure footprints 

would be much larger and most likely to cover most of the areas where 

U.S. and other coalition forces were deployed. However, given the 

weaknesses in the data available for any further analyses, any further 

modeling efforts on this issue would not be any more accurate and helpful. 

In particular, source term data used for modeling the release of chemical 

warfare agents during the Gulf War were inadequate for any model to 

provide, with the desired accuracy and confidence, a single definitive 

simulation of dispersion. Several modeling experts told us that if source 

term inputs into modeling assessments are not accurate, the results of the 

modeling would not be reliable The development of source term data was 

not empirically driven, but rather driven by the subjective analyses of 

individual intelligence agencies. No empirically driven analyses were 

applied to determine plume height source data from the chemical warfare 

agent research, production, and storage sites subjected to air strikes, and 

no empirically driven calculations were disclosed regarding agent purity as 

it affected the rate of decay of the chemical warfare agent munitions that, 

according to intelligence agencies reports, were produced immediately 

prior to the war. 

Efforts to simulate events and define the source term through testing were 

unrealistic, conducted under inappropriate conditions and, in some cases, 

inappropriately applied to dissimilar events. The subjective and defective 

quality of much of the analyses conducted is best demonstrated by the 

dynamic nature of the source data over time. That is, repeated analyses 

resulted in continually changing conclusions and source data, despite the 

fact that no aspect of the actual events changed after their occurrence. 

DOD completely disregarded the results from the LLNL model which 

provided divergent results, which were in the DOD and CIA modeling 

analysis. This occurred despite a high degree of divergence, even among 

the selected DOD models. Further, the precise plume projections of the 

LLNL model were excluded from DOD’s composite modeling. Finally, in 

the DOD and CIA composite model, divergence from individual models 

was masked. Despite all of the uncertainties that emerged from DOD and 

CIA modeling, the results of the modeling were used to serve as a basis for 

determining the exposure status—exposed versus not exposed to 

chemical agents—of the troops in population-based epidemiological 

studies. However, given the weaknesses in DOD modeling and the 

inconsistency of data set—representing these models—given to different 
Page 21 GAO-03-833T 

researchers, there can be no confidence that the research conclusions 

based on these models have any validity. 

Mr. Chairman, this concludes my statement. I will be happy to answer any 

questions you or Members of the Subcommittee may have. 

Should you or your offices have any questions concerning this report, 

please contact me at (202) 512-6412 or Sushil Sharma, Ph.D., DrPH, at 

(202) 512-3460. We can also be reached by e-mail at rhodesk@gao.gov and 

sharmas@gao.gov. Individuals who made key contributions to this 

testimony were Jason Fong and Laurel Rabin. James J. Tuite III, a GAO 

consultant, provided technical expertise. 

Contacts and 

Acknowledgments 
Page 22 GAO-03-833T 

On November 2, 1996, DOD requested the Institute for Defense Analysis to 

convene an independent panel of experts in meteorology, physics, 

chemistry, and related disciplines to review the Khamisiyah modeling 

analysis done by the CIA and its contractor, the Science Applications 

International Corporation. The DOD panel recommended conducting 

additional analyses using several DOD and non-DOD meteorological and 

dispersion models as shown in table 1. 

Table I.1: Meteorological and Dispersion Models Used in Modeling Khamisiyah 

Meteorological 

Model Developer/Sponsor Dispersion Model Developer/Sponsor 

Coupled OceanAtmosphere 

Mesoscale 

Prediction System 

(COAMPS) 

U.S. Navy Hazard Prediction 

and Assessment 

Capability/Second 

Order Closure, 

Integrated Puff 

(HPAC/SCIPUFF) 

Defense Threat 

Reduction Agency 

Mass Consistent 

Wind Field 

(MATHEW) 

Department of 

Energy/Lawrence 

Livermore National 

Laboratory 

Atmospheric 

Dispersion by 

Particle-in-cell 

(ADPIC) 

Department of 

Energy/Lawrence 

Livermore National 

Laboratory 

Mesoscale Model, 

Version 5 (MM5) 

National Center for 

Atmospheric 

Research 

Non-Uniform Simple 

Surface 

Evaporation, Version 

4 (NUSSE4) 

U.S. Army 

Naval Operational 

Global Atmospheric 

Prediction System 

(NOGAPS) 

U.S. Navy Vapor Liquid Solid 

Tracking 

(VLSTRACK) 

U.S. Navy 

Operational Multiscale Environment 

Model with Grid 

Adaptivity (OMEGA)

Defense Threat 

Reduction Agency 

 

Source: GAO. 

Appendix I: Khamisiyah Models 
Page 23 GAO-03-833T 

A Sandia Laboratory empirical study performed in 1969 established a 

power law formula for calculating plume heights attributable to highexplosive detonations. This power law formula was derived from data on 

23 test shots, ranging from 140-2,242 lbs. high explosives at U.S. 

Department of Energy’s Nevada Test Site (National Exercise, Test, and 

Training Center) and provides a cloud top height at 2 minutes after 

detonation. Most of the shots were detonated during near neutral 

conditions, where the clouds continued to rise after 2 minutes; data for 5 

minutes after detonation on some shots shows tops rising to nearly double 

the 2-minute values. The 2-minute values better represent the final cloud 

top heights during stable conditions. 

This formula is represented as 

h = 76(w1/4) 

where h = height of plume in meters 

and, w = weight of explosives in pounds 

Using this formula, a MK-84 or GBU-24 (942.6lb of high explosives) bomb 

would generate a plume of 421 meters: 

H = 76 (942.6 pounds of high explosives)1/4

H = 76 (5.541) 

H • 421 meters 

Figure II.1 shows what the plume height trend line would be using the 

formula to calculate plume heights, resulting from the detonation of high 

explosives ranging in weight from 100 – 2,000 lbs. 

Appendix II: Power Law Formula 
Page 24 GAO-03-833T 

Figure II.1: Plume Height by Weight of Explosive 
Page 25 GAO-03-833T 

As shown in figure III.1, plume geometry associated with high explosive 

discharges shows that the majority of the mass of the plume is located 

towards the higher altitudes, suggesting that the majority of the mass of 

the plume would move to higher altitudes where they might be transported 

by higher speed winds. 

Figure III.1: Examples of Various Plume Geometries 

As shown in figure 3.2, the distribution of the plume geometry may be 

affected by nocturnal jets. 

Appendix III: Plume Geometries and Wind 

Transport 
Page 26 GAO-03-833T 

Figure III.2: Impact of Nocturnal Jets on Plume at Higher Altitudes 

In fact, empirical studies and actual reported and observed events tend to 

refute DOD and intelligence agencies’ assumptions and support the 

alternative assumption of transport by low-level jets. First, empirical 

testing suggests that the plume heights were much higher than postulated 

in the source term data. Second, no massive casualties were claimed, 

reported or observed in areas immediately surrounding the Iraqi chemical 

warfare research, production, and storage sites bombed by coalition 

forces. Third, since many of the bombings occurred at night, the explosive 

effects coupled with higher altitude plumes and the presence of a 

nocturnal boundary layer capable of moving hazardous materials 

hundreds of miles could easily account for this phenomenon, as well as 

the reports of chemical warfare agent detections in areas occupied by U.S. 

and coalition forces. Fourth, the dynamics of advection explained above 

may account for the reported wartime nighttime detections of very lowlevels of chemical agents associated with turbulence mixing the upper and 

lower level atmospheric layers resulting from aircraft-related sonic booms 

and incoming missiles and artillery. 
Page 27 GAO-03-833T 

The Department of Energy’s Lawrence Livermore National Laboratory 

(LLNL) Atmospheric Release Advisory Capability was tasked to conduct 

an analysis using its MATHEW meteorological model with the ADPIC 

dispersion model. Between 1979 and 2003, the LLNL modeling capability, 

known as the Atmospheric Release Advisory Capability (ARAC), now the 

National Atmospheric Release Advisory Center (NARAC), responded to 

more than 100 alerts, accidents, and disasters, and supported more than 

1,000 exercises. These include assessments of nuclear accidents, fires, 

industrial chemical accidents, and terrorist threats. 

During its presentations to the DOD panel in November 1996 and February 

1997, scientists from Lawrence Livermore National Laboratory provided 

plume projections based on the data provided by the panel staff. A number 

of model projections were calculated and presented to the panel. As 

shown in figure IV.1, the LLNL 72-hour composite projection assuming an 

instantaneous release of the contents of 550 rockets containing sarin. It 

shows the plume covering an area extending south-southeast from the 

release point to the Persian Gulf, then turning eastward at the Gulf Coast, 

and then turning northeast over the Gulf and extending northeastward 

across central Iran. 

Appendix IV: Lawrence Livermore National 

Laboratory Khamisiyah Simulation 
Page 28 GAO-03-833T 

Figure IV.1: Lawrence Livermore National Laboratory Composite Projections 

LLNL’s modeling assessment shows that the 72-hour exposure due to the 

instantaneous release of sarin from 550 rockets covers a large hazard area. 

According to LLNL, agent concentration in excess of the dosage amount 

expected to cause “minimal effects” or symptoms on individuals covered a 

2,255 square km area extending approximately 130 km south-southeast 
Page 29 GAO-03-833T 

from the release point.1 Dosages in excess of the amount that would be 

allowed for a worker exposed to sarin in the workplace, or the 

“occupational limit,2

“ were predicted over a 114,468 square kilometer area, 

including Kuwait City, an approximately 200 kilometer-wide area across 

the Persian gulf, and the higher elevations of the Zagos mountain range in 

Iran. The remaining area was determined to be at the “general population 

limit.”3

 1

Minimal effects is the lowest concentration level that would be expected to have 

noticeable effects on human beings. 

2

Occupational limit is about one-tenth of the minimal effects value and is the maximum 

concentration level that would be allowed for a worker who could become exposed to 

sarin in the course of his job duties. 

3

The general population limit represents the limit below which any member of the general 

population could be exposed (e.g., exhale) 7 days a week, every week, for a lifetime, 

without experiencing any adverse health effects. 
Page 30 GAO-03-833T 

A 72-hour plume overlay of those composite projections published by 

OSAGWI is shown in figure V.1.

 

Figure V.1: DOD Composite Projection 

Note: This projection includes the VLSTRAK and SCIPIFF/HPAC dispersion models with COAMPS, 

MM5, and OMEGA meteorological models. 

Appendix V: DOD Model Simulations
Page 31 GAO-03-833T 

Even among the models selected for use by the DOD panel, widely 

divergent directional outcomes were observed. As shown in figure VI.1, 

differences can be seen among various models for hazard areas during the 

first 2 days of the modeling period for Khamisiyah. 

Figure VI.1 Divergence among Models Used in Constructing DOD and CIA Composite Analysis 

The March 10, 1991 graphic demonstrates a 40-45 degree divergence 

between the HPAC/OMEGA and the HPAC/COAMPS projections while the 

March 11, 1991 graphic demonstrates approximately an 80 degree 

divergence. 

The uncertainty attributed to this divergence is not limited to the 

Khamisiyah modeling. According to a modeling analyst involved with the 

modeling of Al Muthanna, the weather models used, COAMPS and 

OMEGA, each showed the plume going in different directions, at a 110-120 

degree difference. The analyst said that COAMPS showed the plume going 

in a North/Northwest direction, while OMEGA showed the plume going 

South. Similar divergence among model predictions was also observed in 

the modeling of Muhammadiyat, as shown in figure VI.2. 

Appendix VI: Divergence among DOD Models
Page 32 GAO-03-833T 

Figure VI.2: Divergence in DOD Models for Muhammadiyat 
Page 33 GAO-03-833T 

In figure VII.1, windfield vector divergence projections 6.0 meters above 

terrain are based on observational data processed by the Meteorological 

Data Interpolation Code (MEDIC) model. 

Appendix VII: Divergence and Wind Field 

Models
Page 34 GAO-03-833T 

Figure VII.1: Lawrence Livermore National Laboratory Diagnostic Wind Model 

Based on Observational Data

In figure VII.2, the Windfield vector model based on European Centre for 

Medium-Range Weather Forecast (ECMWF) projections, processed by the 

Meteorological Data Interpolation Code (MEDIC) model, is shown. 
Page 35 GAO-03-833T 

Figure VII.2: Lawrence Livermore National Laboratory Diagnostic Wind Model 

Based on ECMWF Projections 
Page 36 GAO-03-833T 

In figure VII.3, the windfield vector model is based on Coupled OceanAtmosphere Mesoscale Prediction System (COAMPS) Simulations at the 

U.S. Naval Research Laboratories. 
Page 37 GAO-03-833T 

Figure VII.3: Windfield Vector Model Based on COAMPS 

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