Problem with Setting Simulation Start Time Before Release Time

Topics about the HYSPLIT dispersion model.
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evalski
Posts: 1
Joined: July 9th, 2021, 10:14 am
Registered HYSPLIT User: Yes

Problem with Setting Simulation Start Time Before Release Time

Post by evalski »

Hello all,

I am currently trying to get results for a scenario in which two emission sources are set 24 hours apart. I want to combine the results after both simulations have been completed separately.

Therefore, I am currently trying to create a simulation in which the release start time is set 24 hours before the release start time. In addition, the concentration grids begin recording from the beginning of the simulation, so the first 24 hours should have 0 concentration, and the deposition results should start from the middle of the simulation. (Specifically, I am trying to make a test scenario in which the Smoky Nuclear Test example in the Advanced Tutorial occurs 24 hours after the simulation start time.)

However, when I set the simulation start time to 24 hours prior (30 08 12) and start the grid to record from the beginning of the simulation, the results become very low. It seems that the deposition results are only outputting a tiny fraction of the emission source.
I have also changed the simulation length from 25 to 48 hours.

Summary:
Simulation Start Time: 08 31 12
Release Start Time: 08 31 12 30
Grid recording start time: 08 31 12 30
--> results are fine

Simulation Start Time: 08 30 12 (or anything prior to 08 31 12, such as 08 30 10)
Release Start Time: 08 31 12 30
Grid recording start time: 08 30 12 30
--> results are extremely low

Does anyone know what is going on here?

Thank you in advance.
alicec
Posts: 411
Joined: February 8th, 2016, 12:56 pm
Registered HYSPLIT User: Yes

Re: Problem with Setting Simulation Start Time Before Release Time

Post by alicec »

What are you using for your sampling interval? (last line described here)
https://www.ready.noaa.gov/hysplitusersguide/S313.htm

Can you attach your CONTROL and SETUP.CFG files?
The MESSAGE files from the two runs would also be helpful.

Also to note, the utilities to add together the cdump files do not require that all the time periods
be matching. So it should be fine to do the two runs with different start times and then combine them.
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