Source Term Estimation of Atmospheric Pollutants Using an Ensemble of Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) Concentration Simulations

Source Term Estimation (STE) of a plume of atmospheric pollutants is a mathematically and physically rigorous problem that can be solved in a variety of ways depending on what is known regarding the emission. One such problem is when concentrations are known at multiple locations downstream within the dispersion plume, but the source location is unknown. This study uses the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model with data from the 1983 Cross Appalachian Tracer Experiment (CAPTEX) (Ferber et al. 1986) to determine the location of the experiment’s tracer releases. This is accomplished by conducting an ensemble of HYSPLIT forward concentration simulations using a grid of first-guess locations. The model rank for each simulation is calculated using both ground and airborne measurements, and the location yielding the highest model rank is determined to be the source. Knowing the sensitivity of the STE based on the number of available measurements is useful for determining the location of an unknown release of radionuclides into the atmosphere in support of nuclear treaty monitoring.