ARL News

BAMS Cover Article on Pentagon Shield Describes ARL FRD Tracer Dispersion Study

March 21, 2007

The Field Research Division (FRD) of the Air Resources Laboratory is featured on the cover of the Bulletin of the American Meteorological Society (BAMS). The feature article of the February 2007 issue describes a multi-agency and multi-institutional program dubbed “Pentagon Shield.” The program was instituted to develop and deploy a Pentagon building protection system to guard against a potential terrorist attack using chemical, biological, or radiological material released into the atmosphere. The Pentagon with its 25,000+ occupants represents a likely target of terrorists, as highlighted by the September 11, 2001 attack on the Pentagon itself.

A field study to determine atmospheric transport and diffusion characteristics into and around the Pentagon building was conducted by FRD in late April and early May 2004. FRD released the atmospheric tracer sulfur hexafluoride (SF6) from various locations around the Pentagon during several intensive observation periods to mimic a potential attack. FRD placed both real-time and bag samplers on, around, and in the Pentagon to measure the dispersion characteristics of the tracer into and around the building. The resultant dispersion patterns have been used to verify a series of nested meso- and building-scale meteorological models used in an automated operational building protection system. The complete system will consist of coupled outdoor and indoor components, wherein the outdoor part is essentially a sensor-data-fusion system that uses meteorological and contaminant observations as input to various models.

The scientific objectives addressed by the field program involve the analysis of atmospheric structure and the transport and diffusion process near the Pentagon, the verification of the models, and the comparison of wind data obtained from the different measurement systems. The specific questions addressed by the FRD contribution to the Pentagon Shield program are as follows:

  1. What are the characteristics of the wind field perturbations produced by the building, including circulations in the light wells between the building rings and the center courtyard.
  2. How quickly does the atmosphere surrounding the Pentagon, within the light wells between the rings, and in the central courtyard, purge itself of contaminant after the passage of a plume?
  3. How well do transport and diffusion models simulate observed concentrations of tracer gas near the building?

These questions are being answered through follow-on data analyses. The sensitive nature of the data, however, will prevent a public release of the analyses.

Contact information:
Kirk L. Clawson
Phone: (208) 526-2742