The Defense Threat Reduction Agency is developing enhancements to the Hazard Prediction and Assessment Capability to enable it to provide dispersion calculations in urban areas, to include both building exterior and interior calculations.

This urban dispersion modeling program has many aspects. First, several wind and dispersion models are being developed for immediate or future operational use. The models vary in expected accuracy, run time, and required input data, making it likely more than one will be implemented at any time. Second, DTRA has an active project to acquire and archive urban terrain data, to provide necessary boundary data for urban models. Third, DTRA supports several reduced-scale and full-scale field trials to study urban wind and dispersion phenomena. The data from these field trials are used in model development and validation projects. Finally, DTRA uses its urban dispersion modeling capability to support actual events, operational demonstrations, and planning functions, and some of this work will be described.