Overview*

1. The Hybrid Single Particle Lagrangian Integrated Trajectory Model (HYSPLIT) [1] is a computer model that is used to compute air parcel trajectories and dispersion or deposition of atmospheric pollutants. It was developed by NOAA and Australia's Bureau of Meteorology.
2. HYSPLIT is rather unique in that it may be run in client-server mode (HYSPLIT-WEB) from the NOAA website, allowing members of the public to select gridded historical or forecast datasets, to configure model runs, and retrieve model results with a web browser..

Used For* 

1. One popular use of HYSPLIT is to establish whether high levels of air pollution at one location are caused by transport of air contaminants from another location. HYSPLIT's back trajectories, combined with satellite images (for example, from NASA's MODIS satellites), can provide insight into whether high air pollution levels are caused by local air pollution sources or whether an air pollution problem was blown in on the wind.
2. BlueSky forest fire smoke dispersion modeling
   

* from Wikipedia

Features**

• Best if used beyond one meteorological grid cell from the source.  (i.e., not accurate near the source)***
  
• 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
• 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

 2021 Tim Chui's Installation Instructions for Hysplit.  hysplit_2021-v3.pdf 

Theory (just skim these articles)

1. Langevin equation - - read first couple paragraphs in Wikipedia.  https://en.wikipedia.org/wiki/Langevin_equation
   
2. Very nice review paper by Thomson & Wilson, 2012: History of Lagrangian Stochastic Models for Turbulent Dispersion.  Lagrangian Modeling of the Atmosphere.  Geophysical Monograph Series 200.  AGU.  doi: 10.1029/2012GM001238 
   
3. Paper by Weil, Sullivan and Moeng, 2004: The Use of Large-Eddy Simulations in Lagrangian Particle Dispersion Models, J. Atmos. Sci.,  61, 2877 - 2887.  https://journals.ametsoc.org/doi/pdf/10.1175/JAS-3302.1 .  See their Fig. 1. 
   

Model Dynamics, Physics & Parameterizations

1. Technical Memo on Hysplit_4, by Draxler (2018) .  (covers all aspects:  trajectories, particles, puffs, concentration, etc.)
   
2. Particle version of Hysplit - updated info from Dec 2015 article in BAMS.  <= Nice overview to read carefully.
   

Code sources

1. tcl free download (do first on Mac before downloading hysplit) https://www.activestate.com/activetcl/downloads
   
2. Before you can get the code, you need to register online:  https://ready.arl.noaa.gov/HYSPLIT_register.php
   
3. HYSPLIT model: https://ready.arl.noaa.gov/HYSPLIT.php 
   
4. Installation on PCs and Macs:  https://ready.arl.noaa.gov/documents/Tutorial/html/index.html
   

Resources

1. Tutorials by Reagan McKinney:  Hysplit part 1 - trajectories.     Hysplit part 2 - concentrations . 
2. COMET  MetEd  nice overview  Hysplit  (register for free in COMET) .
3. A. F. Stein, R. R. Draxler, G. D. Rolph, B. J. B. Stunder, M. D. Cohen, and F. Ngan, 2015: NOAA’s HYSPLIT Atmospheric Transport and Dispersion Modeling System. Bull. Amer. Meteor. Soc., 96, 2059–2077.  (December 2015).  Access it thru the UBC Library.
   doi: http://dx.doi.org/10.1175/BAMS-D-14-00110.1 , with supplementary online material  DOI:10.1175/BAMS-D-14-00110.2 .  
   
4. Excellent online basic tutorial from NOAA / ARL:  https://ready.arl.noaa.gov/documents/Tutorial/html/index.html  .
   
5. Excellent online advanced tutorial from NOAA/ARL: https://ready.arl.noaa.gov/documents/TutorialX/html/index.html .
   

Model running resources and tips

1. Installation and running tips (outdated, such as old wrf2arl; see new wrf2arl below) from our TA, Matt. 
   
2. A 235 MB NetCDF file of WRF output, to use for homework runs of Hysplit.
3. A 1.5 GB ARL file produced at UBC in 2018 that covers all of Canada, to use for homework runs of Hysplit.
   

WRF-ARW to Hysplit-ARL file conversion - - fixed and revised for Macintosh and other linux/unix systems in 2018

1. First, make a list of your WRF-ARW output files that you want to use in Hysplit.  Also, you can preview those NetCDF files using the panoply program.
   
2. The arw2arl converter provided by NOAA/ARL is broken, but can be fixed.  So ..
3. Use the following directions to download the old arw2arl fortran code and fix it.
   ... or you can download and unzip our "hopefully-already-fixed" version of the arw2arl executable for linux machines.
   
4. Then use the fixed converter to separately convert each of the NetCDF output files from WRF (you might have one file for each forecast hour, depending on your settings when you ran WRF).
   
5. Finally, here is a bash script called arl_concat (as text or pdf) you can use to concatenate all the WRF output files (for different forecast hours) into a single arl input file that can be read as input by Hysplit.
   

Other Resources for Class Discussion

1. Time-difference worksheet to learn how the Hysplit transport code works .
2. Canadian Lagrangian models run at CMC .
   

http://www.eos.ubc.ca/courses/atsc507/ADM/
Copyright © 2016, 2018, 2021 by Roland Stull.