The Societal Value of the HYSPLIT Air Dispersion Model

The Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model, which was developed by NOAA’s Air Resources Lab (ARL), is used in a wide variety of applications to estimate the forward and back trajectories of pollutants. Because HYSPLIT is available for free, its societal value is not easily measured. This study describes its many types of applications and provides a literature review that highlights how the benefits of these uses could theoretically be quantified. However, the heart of the report is quantifying in monetary terms the social value of information that the HYSPLIT model provides to its users and society at large. Both case studies highlight instances in which consulting HYSPLIT led to better information and more informed decisionmaking, with measurable benefits to society. The first case explores the state of Maine’s citing HYSPLIT to prove to the Environmental Protection Agency (EPA) that certain counties were not contributing to ozone exceedances in the state and to petition for those areas to be removed from the ozone transport region, a designation that imposes stricter environmental regulations on polluters. The second case explores the benefits of using HYSPLIT to better inform the evacuation zone following a fire at the Husky Refinery in Duluth, MN. The combined case study values more than exceed the annual cost of maintaining the HYSPLIT model.