HYSPLIT - Hybrid Single Particle Lagrangian Integrated Trajectory Model

HYSPLIT Description

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. The intial development was a result 

of a joint effort between NOAA and Australia's Bureau of Meteorology. Recent upgrades include enhancements 

provided by a number of different contributors. Some new features include improved advection algorithms, 

updated stability and dispersion equations, continued improvements to the 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 dispersion of a pollutant is calculated by assuming either puff or particle dispersion. In the puff model, puffs 

expand until they exceed the size of the meteorological grid cell (either horizontally or vertically) and then split into 

several new puffs, each with it's share of the pollutant mass. In the particle model, a fixed number of particles are 

advected about the model domain by the mean wind field and spread by a turbulent component. The model's 

default configuration assumes a 3-dimensional particle distribution (horizontal and vertical). 

The model can be run interactively on the Web through the READY system on our site or the code executable and meteorological data can be downloaded to a Windows or 

Mac 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 user's must obtain their own meteorological data files. The unregistered version is identical to the registered version except that plume 

concentrations cannot be calculated with with forecast meteorology data files. The trajectory-only model has no restrictions and forecast or archive trajectories may be 

computed with either version. 

Model Features

Trajectories

Single or multiple (space or time) simultaneous trajectories

Optional grid of initial starting locations 

Computations forward or backward in time

Default vertical motion using omega field

Other motion options: isentropic, isosigma, isobaric, isopycnic

Trajectory ensemble option using meteorological variations

Output of meteorological variables along a trajectory

Integrated trajectory clustering option

Air Concentrations

3D particle dispersion or splitting puffs (top-hat or Gaussian)

Instantaneous or continuous emissions, point or area sources

Multiple resolution concentration output grids

Fixed concentration grid or dynamic sampling

Wet and dry deposition, radioactive decay, and resuspension

Emission of multiple simultaneous pollutant species

Automated source-receptor matrix computation

Ensemble dispersion based on variations in meteorology, turbulence, or physics

Concentration probability output for multiple simulations

Integrated dust-storm emission algrorithm

Define rate constants to convert one species to another

Mass can be transferred to a Eulerian module for global-scale simulations

Air Resources Laboratory - HYSPLIT - Hybrid Single Particle Lagrangian Integrated Traj... Page 1 of 2

http://www.arl.noaa.gov/HYSPLIT_info.php 3/31/2014
Modified: April 11, 2012 

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Meteorology

Model can run with multiple nested input data grids

Links to ARL and NWS meteorological data server

Access to forecasts and archives including NCAR/NCEP reanalysis

Additional software to convert MM5, RAMS, COAMPS, WRF, and other data

Utility programs to display and manipulate meteorological data

Common Features

Tcl/Tk GUI with integrated html compatible help

Viewer to display TOMS aerosol index with model particle positions

Model restart from particle position files for plume initialization

Model graphics displayed as Postscript files

Converters to many other formats: GIF, GrADS, ArcView, Vis5D

Further Information

HYSPLIT Summary Handout (PDF, 250 KB)

Air Resources Laboratory - HYSPLIT - Hybrid Single Particle Lagrangian Integrated Traj... Page 2 of 2

http://www.arl.noaa.gov/HYSPLIT_info.php 3/31/2014