If they do not agree, then their outputs should be considered equally likely unless investigation into the differences reveals an error in one of the models. One could, for example, use two appropriate meteorological models and feed their results into two transport and diffusion models. This would provide four sets of reconstructions for each set of source and meteorological inputs.

Varying the source inputs parametrically and the meteorological inputs through ensemble, perturbation, and/or by moving the detonation in time and space, as the Naval Surface Warfare Center did, and by using combinations of models, appears to be the only sure way to develop the range of possible outcomes that might have occurred at Khamisiyah.

Presenting the results requires some care. There are two audiences for these results. Epidemiologists are concerned with concentration profiles, over time, where troops were actually located. These profiles can be used to compute the exposures possibly experienced by these forces (or, more properly, the ranges of exposures experienced by these forces). However, concentration profiles at grids of locations do little to visualize the release for reviewers or for the general public. Total integrated dosages for the full duration of the release are useful for showing all the places that agent might have gone, but can overstate the risk to forces that were not present and stationary during the entire time of the release. Probably the most realistic summary presentations are periodic integrated dosage contours using a time period equal to the periods for which troop locations are known. For example, if troop locations are known only once per twenty-four-hour day, then a set of twenty-four-hour integrated dosage contours probably best summarizes the release.

Recommendations for the Future

Some of the challenges to reconstructing the Khamisiyah pit release will likely be faced in the future. If realization that there has been a nerve agent release comes after the fact, reconstructing meteorological and source data could be difficult. There is little that can be done to prevent this a priori, except to be more aware of possible agent release during demolition and bombing and to take appropriate measurements without delay.

Model capabilities do not appear to be a constraint. There are excellent models to address meteorological analysis, and transport and diffusion. However, the Panel noted that model selection and application in this incident was ad hoc and less than ideally coordinated. These factors, as much as anything, have contributed to delays and controversy regarding the pit reconstruction. This process could be improved by ensuring that some organization has the end-to-end responsibility for addressing this type of issue, has selected the most appropriate meteorological and transport and diffusion models, and has ensured that the models are either linked together or that there are unified models incorporating all of the elements required for the analysis.

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