HYSPLIT Forum: hysplitbbs.arl.noaa.gov

I am just trying to establish whether this idea is sensible. I am mainly interested in this for ash fall applications, so if the PARDUMP file doesn't hold information on the particles that have reached the ground then that kills the idea for me.

Anyway the idea is that the best grid (boundaries and resolution) to define your output concentration/deposition field on really depends on the case and where the particles end up. So I was thinking it might be nice to read the PARDUMP file to determine the spatial range of pollutants, and use that information to write the CONTROL file for a final call to par2conc.

Is this a sensible thing to do?

Cheers,
Cory.

I need to look into the code about whether ground-level particles are in the PARDUMP file.

Yes, you need to know where the particles will be to optimally set the output grid. Your idea of using the PARDUMP to determine the spatial range, then set the grid in CONTROL and run par2conc, has one limitation. The HYSPLIT time step is determined based on the maximum wind speed at a grid point, the horizontal size of the grid, and the value TRATIO in the SETUP.CFG file. TRATIO is the "fraction of a grid cell that a particle is permitted to transit in one advection time step" (html/S610.htm). If you run with one grid, optimize it and run par2conc, it might give a different result than directly running HYSPLIT originally on that grid if the time step differs.

It may be better to run a coarse grid first, tune it, and re-run HYSPLIT, and not run par2conc.