Predicting atmospheric debris transport in real-time using a trajectory forecast model

Abstract

An experiment is described in which a trajectory forecast model was used in real-time to estimate the transport of debris associated with a large chemical explosion in the south-western U.S. The forecast trajectories were used to vector sampling aircraft into a position favorable for intersecting the debris cloud. The forecasts are evaluated and compared with three independent measures of debris transport: diagnostic trajectories calculated after the experiment using observed wind fields; transport of a tracer balloon; and aircraft measurements of the debris cloud. Trajectory forecasts originating as early as 39 h before the explosion successfully predicted the downwind atmospheric drift pathway of the cloud. The forecast trajectories agreed well with diagnostic trajectories, confirming the high quality of the meteorological forecast data upon which the trajectories are based. The forecast trajectories also proved skilful in predicting real-rime atmospheric motion at short notice. The results support our conclusion that forecast trajectory models are valuable tools for vectoring sampling aircraft in long-range atmospheric dispersion experiments and operations. These models should prove useful in the future when real-time estimates of atmospheric transport are needed.