Can't Initialize Back trajectories between 21:01 and 23:59

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klarson_SITC
Posts: 2
Joined: February 8th, 2023, 8:15 pm
Registered HYSPLIT User: Yes

Can't Initialize Back trajectories between 21:01 and 23:59

Post by klarson_SITC »

Hello,

I wanted to do a 24-hour backtrajectory of the Dispersion HYSPLIT using the READY Server using the 0.25 deg GFS (model Archived GFS0p25) at 23:00 UTC on 12/24/2022.

It flags that "The release starting time (12/24/2022 23 UTC) is after the meteorological data ending time (12/24/2022 21 UTC). Please go back and check the release starting time."

We can't select a previous day in the next day's GFS file so I can't try to run 12/24/2022 23:00 with the 12/25/2022 00 UTC. I checked and this flag occurs for a couple different Archived GFS0p25 files when attempting to start the back trajectory between 22:00 UTC to 23:59 UTC. Is this supposed to be the way HYSPLIT functions?

I would have expected HYSPLIT to recognize 22:00 and 23:59 are calculated using a linear interpolation between 21 UTC from that day (12/24/2022) and 00 UTC from the next day (12/25/2022) as the GFS output is in 3 hour intervals. It works fine for 21:59 UTC so if there is a linear interpolation between 21 UTC and 00 UTC the next day that interpolation function is working fine in that case.
sonny.zinn
Posts: 354
Joined: May 8th, 2019, 1:31 pm
Registered HYSPLIT User: Yes

Re: Can't Initialize Back trajectories between 21:01 and 23:59

Post by sonny.zinn »

[The reply was updated to correct an error.]

Although the READY user interface allows users to choose one archived meteorological data file for back trajectory calculations, more than one files are selected to run HYSPLIT. The number of actual files depends on the meteorology. For GFS0p25, ten files are automatically selected, more specifically, the user selected file at day D, file at day D-1, D-2, ..., D-9. For your application, you could pick the 12/25/2022 file and specify the starting time of the back trajectory to 12/24/2022 23 UTC. However, the user interface does not allow entering a starting time other than for day D. We will look into changing this.

We recommend you to download and install a public version of HYSPLIT, meteorological data files that are required for your study, and perform back trajectory runs. Please check out https://www.ready.noaa.gov/HYSPLIT.php (for downloading pre-compiled HYSPLIT), https://www.ready.noaa.gov/documents/Tu ... basic.html (for trajectory calculation), and https://www.ready.noaa.gov/documents/Tu ... error.html (for back trajectory calculation).
klarson_SITC
Posts: 2
Joined: February 8th, 2023, 8:15 pm
Registered HYSPLIT User: Yes

Re: Can't Initialize Back trajectories between 22:00 and 23:59

Post by klarson_SITC »

Thank you for the reply.

As I work for a small Tribal government, computing resources are sparse to non-existent to do local dispersion/trajectory models with multiple 10s of GBs worth of weather data - which is why I really appreciate the READY Server access.

Just to clarify for my own understanding of how READY initialization functions:
  • Only one archived meteorological data file can be chosen to initialize trajectory and dispersion calculations at READY
  • GFS 0.25 is in 3 hr intervals (0, 3, 6, ... 21) for a single day. These are saved in a single file and selected by the user.
  • HYSPLIT on the READY server initializes a dispersion back trajectory using the GFS model fields that are from the nearest 3 hour interval equal to or greater than that hour (11:27 --> 12:00, 15:45 --> 15:00 - positing the latter since 21:59 runs fine but 22:00 does not) so since 22 is greater than 21, this breaks as the "24" is "00" on the next day and thus not in the file.
sonny.zinn
Posts: 354
Joined: May 8th, 2019, 1:31 pm
Registered HYSPLIT User: Yes

Re: Can't Initialize Back trajectories between 21:01 and 23:59

Post by sonny.zinn »

There was an error in my previous reply, which was corrected. Please read it again. It turns out the limitation has to do with the selectors for the start time. We will look into fixing this but it is going to take a while.
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