The Hybrid Single-Particle Lagrangian Integrated Trajectory model (HYSPLIT), developed by NOAA’s Air Resources Laboratory, is one of the most widely used models for atmospheric trajectory and dispersion calculations. We present the model’s historical evolution over the last 30 years from simple hand-drawn back trajectories to very sophisticated computations of transport, mixing, chemical transformation, and deposition of pollutants and hazardous materials. We highlight recent applications of the HYSPLIT modeling system, including the simulation of atmospheric tracer release experiments, radionuclides, smoke originated from wild fires, volcanic ash, mercury, and wind-blown dust.

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NOAA’s HYSPLIT Atmospheric Transport and Dispersion Modeling System

Abstract Air quality forecasters, emergency responders, aviation interests, government agencies, and the atmospheric research community are among those who require access to tools to analyze and predict the transport and dispersion of pollutants in the atmosphere. Because of this need, the unique web-based Real-time Environmental Applications and Display sYstem (READY) has been under continuous development since 1997 to provide access to a suite of tools for producing air parcel trajectory and dispersion model results and displaying meteorological data. READY provides a “quasi-operational” portal to run the HYSPLIT atmospheric transport and dispersion model and interpret its results. Typical user applications include modeling the release of hazardous pollutants and volcanic ash, forest fire and prescribed burn smoke forecasting, poor air quality events, and various climatological studies. In addition, READY provides the user with quick access to meteorological data interpolated to the location of interest, helping in the interpretation of the HYSPLIT model results.

Real-time Environmental Applications and Display sYstem (READY) Website

Air quality forecasters, emergency responders, aviation interests, government agencies, and the atmospheric research community are among those who require access to tools to analyze and predict the transport and dispersion of pollutants in the atmosphere. Because of this need, the unique web-based Real-time Environmental Applications and Display sYstem (READY) has been under continuous development since 1997 to provide access to a suite of tools for producing air parcel trajectory and dispersion model results and displaying meteorological data. READY provides a “quasi-operational” portal to run the HYSPLIT atmospheric transport and dispersion model and interpret its results. Typical user applications include modeling the release of hazardous pollutants and volcanic ash, forest fire and prescribed burn smoke forecasting, poor air quality events, and various climatological studies. In addition, READY provides the user with quick access to meteorological data interpolated to the location of interest, helping in the interpretation of the HYSPLIT model results.

Real-time Environmental Applications and Display sYstem: READY

https://www.jstor.org/stable/10.1641/0006-3568(2001)051%5B0180:ADITNU%5D2.0.CO;2

Acidic Deposition in the Northeastern United States: Sources and Inputs, Ecosystem Effects, and Management Strategies

Statistical analysis of air mass back trajectories combined with long-term ambient air pollution measurements are useful tools for source identification. Using these methods, the geographic information system (GIS) based software, TrajStat, was developed to view, query, and cluster the trajectories and compute the potential source contribution function (PSCF) and concentration weighted trajectory (CWT) analyses when measurement data are included.

TrajStat: GIS-based software that uses various trajectory statistical analysis methods to identify potential sources from long-term air pollution measurement data

The HYSPLIT_4 (HYbrid Single-Particle Lagrangian Integrated Trajectory) model is designed for quick response to atmospheric emergencies, diagnostic case studies, or climatological analyses using previously gridded meteorological data. Calculations may be performed sequentially on multiple meteorological grids, going from fine to coarse resolution using either archive or forecast data fields. Air concentration calculations associate the mass of the pollutant species with the release of either puffs, particles, or a combination of both. The dispersion rate is calculated from the vertical diffusivity profile, wind shear, and horizontal deformation of the wind field. Air concentrations are calculated at a specific grid point for puffs and as cell-average concentrations for particles. The model results are evaluated against ACE balloon trajectories, air concentrations from the ANATEX tracer experiment, radiological deposition from the Chernobyl accident, and satellite photographs of the Rabaul volcanic eruption. One common feature of the model results was their sensitivity to the vertical atmospheric structure; trajectories in terms of their height when near ground-level due to the strong gradients of wind speed and direction, air concentrations with respect to the rate of vertical mixing, and deposition as a result of the vertical distribution of the pollutant.

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Roland R. Draxler

Papers

An Overview of the HYSPLIT_4 Modelling System for Trajectories, Dispersion, and Deposition