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.

Government-run programs are increasingly under scrutiny to prove their value to justify their funding. Since such programs provide resources and tools that are public goods and are generally available for free, they typically lack traditional methods for assessing product value used by private companies, such as a price on the product. Instead, one way to estimate the value of a government program is to assess the value of information (VOI) it provides. Such an assessment requires knowledge of the uses to which it is put, the benefit of those uses, and the counterfactual: what would happen to the activities if the program in question were no longer available.

The National Oceanic and Atmospheric Administration (NOAA) Air Resources Lab (ARL) developed the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model to simulate dispersion and forward and back trajectories of pollutants in the atmosphere. HYSPLIT is widely used for a variety of reasons, such as modeling smoke from wildfires, tracing the source of radionuclides, and informing aircraft rerouting in the event of volcanic eruptions. HYSPLIT is distinguished because it is free, accessible, supported, and frequently updated. Additionally, it can run faster than similar models, and the website provides curated meteorological data to drive the model for use and/or download.

HYSPLIT’s uses and corresponding benefits are vast and can be difficult to assess because it is available for free to the public. Without a price tag, the user’s willingness to pay (WTP) for such a product is not directly known. However, it is possible to assign a monetary value to many of HYSPLIT’s benefits through techniques developed in the VOI literature, as discussed in section 4, which will help decisionmakers measure this value against the program’s cost and assess its overall net societal value.

This report examines those net benefits to society by making monetary estimates where possible. Section 1 covers the concept of value, which defines what we mean by VOI and how we would begin to quantify it. Section 2 categorizes HYSPLIT by use, source, and the corresponding possible benefits from that use, which includes human health, environmental health, property, and administrative benefits, such as time saved and mitigation costs avoided. Section 3 describes the two case studies performed as part of this project, along with the methods and the results. The first study estimates the benefits of Maine’s citing HYSPLIT to prove that parts of the state could be excluded from the ozone transport region (OTR), which imposed additional regulations on facilities that emit volatile organic compounds (VOCs) in those areas. The second case study explores the use of HYSPLIT in an emergency to help inform an evacuation zone following an explosion at the Husky Refinery in Duluth, MN. Section 4 examines the literature relevant to each benefit category and, where possible, the economic valuation literature as it relates to the uses of HYSPLIT. Section 5 concludes.