Meteorological reanalyses for the study of Gulf War illnesses: Khamisiyah case study

The Marine Meteorology Division of the Naval Research Laboratory (NRL), ass isted by the Fleet Numerical Meteorology and Oceanography Center, has perfo rmed global and mesoscale reanalyses to support the study of Gulf War illne ss. Realistic and quantitatively accurate atmospheric conditions are needed to drive dispersion models that can predict the transport and dispersion o f chemical agents that may have affected U.S. and other coalition troops in the hours and days following the demolition of chemical weapons at Khamisi yah, Iraq, at approximately 1315 UTC 10 March 1991. The reanalysis was cond ucted with the navy's global and mesoscale analysis and prediction systems: the Navy Operational Global Atmospheric Prediction System and the NRL Coup led Ocean-Atmosphere Mesoscale Prediction System. A comprehensive set of ob servations has been collected and used in the reanalysis, including unclass ified and declassified surface reports, ship and buoy reports, observations from pibal and rawinsonde, and retrievals from civilian and military satel lites. The atmospheric conditions for the entire globe have been reconstruc ted using the global system at the effective spatial resolution of 0.75 deg rees. The atmospheric conditions over southern Iraq, Kuwait, and northern S audi Arabia have been reconstructed using the mesoscale system at the spati al resolutions of 45, 15, and 5 km. In addition to a baseline reanalysis, p erturbation analyses were also performed to estimate the atmospheric sensit ivity to observational error and analysis error. The results suggest that t he reanalysis has bounded the variability and that the actual atmospheric c onditions were unlikely to differ significantly from the reanalysis. The synoptic conditions at and after the time of the detonation were typica l of the transitional period after a Shamal and controlled by eastward-prop agating small-amplitude troughs and ridges. On the mesoscale, the condition s over the Tigris-Euphrates Valley were further modulated by the diurnal va riation in the local circulations between land, the Persian Gulf, and the Z agros Mountains. The boundary layer winds at Khamisiyah were from NNW at th e time of the detonation and shifted to WNW in the nocturnal boundary layer . On the second day, a strong high passed north of Khamisiyah and the winds strengthened and turned to the ESE. During the third day, the region was d ominated by the approach and passage of a low pressure system and the assoc iated front with the SE winds veering to NW. A transport model for passive scalars was used to illustrate the sensitivit y to the reanalyzed fields of potential areas of contamination. Transport c alculations based on various release scenario and reanalyzed meteorological conditions suggest that the mean path of the released chemical agents was southward from Khamisiyah initially, turning westward, and eventually north westward during the 72-h period after the demolition. Precipitation amounts in the study area were negligible and unlikely to have an effect on the ne rve agent.