Why can’t I run a back trajectory from 1900 UTC on 31 July, 2001 using downloaded FNL data? I attached my CONTROL file
Posted: July 22nd, 2021, 1:15 pm
[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:
Why can’t I run a back trajectory from 1900 UTC on 31 July, 2001 using downloaded FNL data? I attached my CONTROL file for you.
Answer:
You are starting your trajectories at 1900UTC on 31 July and you have only defined the July meteorological data in your CONTROL file. Data fields are only every 6 hours (0,6,12,18 UTC) in the FNL archive. Therefore when you start at 1900UTC, the model needs to interpolate data to that time from 1800UTC on 31 July and 0000UTC on 1 August. You need to also define the August data in your control file and have it availble on your computer.
Roland Draxler
Question:
Why can’t I run a back trajectory from 1900 UTC on 31 July, 2001 using downloaded FNL data? I attached my CONTROL file for you.
Answer:
You are starting your trajectories at 1900UTC on 31 July and you have only defined the July meteorological data in your CONTROL file. Data fields are only every 6 hours (0,6,12,18 UTC) in the FNL archive. Therefore when you start at 1900UTC, the model needs to interpolate data to that time from 1800UTC on 31 July and 0000UTC on 1 August. You need to also define the August data in your control file and have it availble on your computer.
Roland Draxler