A Short Description of the NOAA HYSPLIT (Hybrid Single-Particle Lagrangian Integrated Trajectory) Model

Richard Artz
NOAA Air Resources Laboratory,
University of Minnesota,
Silver Spring, MD USA

The HYSPLIT (HYbrid Single-Particle Lagrangian Integrated Trajectory) model is a complete system for computing simple air parcel trajectories to complex dispersion and deposition simulations. As a result of a joint effort between NOAA and Australia's Bureau of Meteorology, the model has recently been upgraded. New features include improved advection algorithms, updated stability and dispersion equations, a new graphical user interface, and the option to include modules for chemical transformations. Without the additional dispersion modules, Hysplit computes the advection of a single pollutant particle, or simply its trajectory.

The model can be run interactively on the Web through the READY system on the Air Resources Laboratory Web site ( or the code executable and meteorological data can be downloaded to a Windows PC. The Web version has been configured with some limitations to avoid computational saturation of our Web server. The registered PC version is complete with no computational restrictions, except that users must obtain their own meteorological data files. The meteorological input fields used by Hysplit are required to be in "ARL packed" format. All gridded meteorological data available on our site are already in this form and may be FTP'd to a PC without conversion. The unregistered version is identical to the registered version except that it will not work with forecast meteorology data files.

A short description of model features and recent updates, as well as a few example products will be presented.