Best Practices for Computing Backtrajectories with WRF

F

ffrntic

New member
Hello everyone,


I am currently working on a case study and would like to compute air parcel backtrajectories using WRF output. However, I'm running into some confusion regarding the recommended approach.

Is there a supported, internal option in WRF for computing backward trajectories (not forward)? The documentation only mentions traj_opt = 1 for forward trajectories.

I’ve considered using HYSPLIT, but was told the resolution may be too coarse for our needs. Would a custom Python script using 3D wind fields (e.g., with Runge-Kutta integration) be a viable alternative? Has anyone implemented this and validated the output?

If anyone can share references or workflows they’ve used for high-resolution backtrajectory analysis from WRF output, I’d be grateful.
 
Thank you for you answer. I’m trying to determine the best tool for high-resolution backward trajectory analysis. Between RIP and HYSPLIT (using WRF output), which tool is likely to provide better spatial and temporal resolution in the computed trajectories?
 
Unfortunately I don't have any experience with HYSPLIT, so I can't provide a fair assessment of the two tools. Perhaps someone else on this forum will be able to respond.
 
I am about to begin this process myself and will be converting my very high-resolution WRF-ARW output files to the proper format for use in HYSPLIT. There is guidance on this process and using the "arw2arl" executable here: Converting WRF data to ARL - HYSPLIT Forum: hysplitbbs.arl.noaa.gov.

If I had not already run WRF-ARW, an easier workflow for WRF and HYSPLIT looks possible using the ARL's coupled WRF-HYSPLIT (Inline WRF-HYSPLIT Coupling), but I'm only just learning of this option.
 
Thanks for the reply — I'm in the middle of this same process as well.

I’m trying to use arw2arl on my WRF-ARW output (converted to classic NetCDF), but I keep getting the following error:

: NetCDF: Malformed URL

Even after regenerating WRFDATA.CFG using the -s option, the error persists.

Have you run into this before? Would be curious if you’ve found a way around it.
 
./arw2arl wrfout_d02_2025-07-27_00_00_00_7km
This works for me !!


Using an existing decoding configuration: WRFDATA.CFG
Using an existing encoding configuration: ARLDATA.CFG
NOTICE pakset:
Number of index records = 1
Number of records /time = 321
NOTICE pakini: start initialization rec = 1
NOTICE pakini: end initialization rec = 321
Completed: 25 7 27 0 0
NOTICE pakini: start initialization rec = 322
NOTICE pakini: end initialization rec = 642
Completed: 25 7 27 1 0
NOTICE pakini: start initialization rec = 643
NOTICE pakini: end initialization rec = 963
Completed: 25 7 27 2 0
NOTICE pakini: start initialization rec = 964
NOTICE pakini: end initialization rec = 1284
Completed: 25 7 27 3 0
NOTICE pakini: start initialization rec = 1285
NOTICE pakini: end initialization rec = 1605
Completed: 25 7 27 4 0
 
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