An integrated approach to defining realtime upwind threat zones

Prediction of upwind threat zones permits authorities to focus their monitoring and security resources for site or building protection. A threat zone is defined as the area encompassing potential hazardous release points that will impact a given location during the forecast period. Release points within the threat zone can be further characterized by a threat's estimated arrival time. Coupled mesoscale and CFD models produce the required wind fields at scales from kilometers down to meters, which are used to drive a Lagrangian puff model (SCIPUFF) that predicts the movement of airborne biological and chemical materials. We use a Monte-Carlo approach involving numerous point release sites that are automatically selected based upon the prevailing wind field and forecast length. Plumes from each release site are tracked to determine their impingement and arrival time upon the target building. Results from several cases that were observed during Pentagon Shield Campaign 2004 will be presented.