A Real-Time Atmospheric Dispersion Modeling System

This paper describes a new 3-D multi-scale atmospheric dispersion modeling system and its on-going evaluation. This system is being developed for both real-time operational applications and detailed assessments of events involving atmospheric releases of hazardous material. It is part of a new, modernized Department of Energy (DOE) National Atmospheric Release Advisory Center (NARAC) emergency response computer system at Lawrence Livermore National Laboratory. This system contains coupled meteorological data assimilation and dispersion models, initial versions of which were described by Sugiyama and Chan (1998) and Leone et al. (1997). Section 2 describes the current versions of these models, emphasizing new features. This modeling system supports cases involving both simple and complex terrain, and multiple space and time scales from the microscale to mesoscale. Therefore, several levels of verification and evaluation are required. The meteorological data assimilation and interpolation algorithms have been previously evaluated by comparison to observational data (Sugiyama and Chan, 1998). The non-divergence adjustment algorithm was tested against potential flow solutions and wind tunnel data (Chan and Sugiyama, 1997). Initial dispersion model results for a field experiment case study were shown by Leone et al. (1997). A study in which an early, prototype version of the new modeling system was evaluated and compared to the current NARAC operational models showed that the new system provides improved results (Foster et al., 1999). In Section 3, we show example results from the current versions of the models, including verification using analytic solutions to the advection-diffusion equation as well as on-going evaluation using microscale and mesoscale dispersion field experiments.