Is there a way to run a number of trajectories at once?

[sonny.zinn]

[Note that the question and the answer below are recreated from a HYSPLIT FAQ site that predates this forum site. The original posting date is unknown.]

Question:
I am running a statistical program that groups hundreds of trajectories over one another and creates probability fields. My problem is that generating one trajectory at a time and converting the ASCII trajectory endpoint data into Excel format is far too time consuming. Is there a way to run a number of trajectories at once?

Answer:
Yes, this is possible. On the web you are limited to one latitude,longitude 3 heights. The PC version offers more options (https://www.ready.noaa.gov/HYSPLIT.php). A link to archived meteorology is also on that web page. I’m not sure if you are familiar with the PC version so I’ll go into some detail.

If you want to run trajectories from many locations at the same time, just give the various latitude-longitude-heights in “Trajectory” “Trajectory Setup”. This sets the CONTROL file. The model is run with “Trajectory” “Run Standard Model”. “Trajectory” “Trajectory Display” does the plot.

If you want to start a trajectory every X number of hours from the same source (latitude,longitude,height) go to “Advanced”, “Configuration Setup” and “Trajectory”. Then set the “Temporal trajectory restart interval” to the X number of hours. Once saved, this is the parameter NSTR=X in the file SETUP.CFG in the ‘working’ directory. In the CONTROL file (“Trajectory”, “Trajectory Setup”) set the “Total run time” to many days. Run the trajectories – “Trajectory”, “Run Standard Model”. Plot the trajectories – “Trajectory” “Trajectory Display”. On the vertical-time section plot at the bottom you can see the trajectories beginning every X hours. All trajectories end of after the “Total run time”. The plotting program may be limited to 25 trajectories.

Another way to do create many trajectories is to edit the tcl script C:\hysplit4\examples\scripts\auto_traj.tcl to loop through trajectory origins or time.

Barbara Stunder