HYSPLIT — The Complete Guide: Free Air Trajectories and Dispersion of Pollutants, Smoke and Ash
HYSPLIT is a model from the Air Resources Laboratory of NOAA, the US National Oceanic and Atmospheric Administration. It is in the public domain and completely free, and because it uses global meteorological data, it works for any point in the world. There is a downloadable version for Windows, macOS and Linux, and an online version that runs in the browser.
HYSPLIT
NOAA Air Resources Laboratory
A model of air-parcel trajectories and the dispersion of pollutants, smoke, ash and radionuclides from global meteorological data, by NOAA.
Get it from the vendorWhat you get
- Forward trajectories — where an air mass leaving a given point will travel.
- Backward trajectories — where the air measured at a station came from, to identify a pollution source.
- Dispersion and deposition — concentrations and ground deposition of particles and gases.
- Many substances — industrial pollutants, smoke, volcanic ash and radionuclides.
- Ready data — global meteorological archives and forecasts.
How it differs
HYSPLIT works on scales of tens to thousands of kilometres and suits regional questions: where dust came from, where smoke from a large fire will travel, or what will happen to a cloud from an accidental release. It is not a replacement for a regulatory model that computes concentrations at a plant fence line — a local model fits that job.
Related tools
For dispersion around stacks and industrial plants — AERMOD. For local-scale emergency scenarios with hazardous chemicals — ALOHA. For pollution trajectories at sea — OpenDrift.
AERMOD
US Environmental Protection Agency
An air dispersion model for stacks and area sources: ground-level concentrations around industrial plants, used worldwide in environmental impact studies.
Get it from the vendor
ALOHA
US EPA and NOAA (CAMEO)
Models toxic gas clouds, fires and explosions from a hazardous chemical release and maps the threat zones around it.
Get it from the vendor
OpenDrift
Norwegian Meteorological Institute
Traces the drift of oil, plastic, larvae or search-and-rescue targets in the ocean.
Get it from the vendor
QGIS
QGIS.org
Open-source GIS for spatial analysis, layer work and map production.
Get it from the vendorThe bottom line
HYSPLIT is a powerful, accessible tool for understanding how pollution moves through the atmosphere. It is public domain and completely free, including for commercial use.