Advanced / Special Topics / Particle Dump File Format

The concentration configuration menu provides an option to write a model initialization file, which by default is always named "PARDUMP" (for particle dump). This file can be written at regular intervals during the simulation, a convenient way to restart a simulation in case of unexpected failure. To restart the model using the PARDUMP file it is only necessary for the file to be present in the root working directory. If the internal time stamp of the file matches the start time of the simulation, the model will initialize the particle count from the file before emitting new particles according to the emission scenario defined in the control file. The format of the PARDUMP file is given below:

Record #1

Record #2 - Loop to record: Number of particles

The "Particle" tab of the "Special File Display" menu brings up a Windows based viewer that shows the particle positions over a map background. The display can be zoomed and otherwise adjusted using the left and right mouse buttons in conjunction with the shift and cntl keys. Help is provided on the screen with the left and right side comments corresponding to the respective mouse button. The particle viewer can also be used to overlay satellite images on the particle positions. More information on this is provided "FTP Satellite Data" help menu. The particle position file may be converted to a binary concentration file through the command line utility program par2conc.

Number of pollutants per particle is set by MAXDIM. Default is 1.

HEIGHT is in meters agl. The height is in agl even when KMSL=1 is set in SETUP.CFG
Note that there may be some differences between the value written to the pardump file and the actual value when the terrain height is large. The terrain height is not passed to the pardump reading or writing routines and so the height is written approximating terrain height as 0m. This results in a small difference which is dependent on the terrain height and internal scaling height.
Za' = (ZMDL / (ZMDL-ZTER))* Za
Za' is the approximated height written to the pardump file.
Za is the actual height of the particle
ZMDL, internal scaling height. Default is 25km. May be higher if model top is chosen higher. See #6
ZTER is the terrain height.
Zt is the terrain following coordinate.
Example - a height of 100m agl in an area with terrain height tof 1600m would show up as a height of 106.8m in the pardump file.
This has no impact on the intended functionality which is to restart the model from a pardump file created by the model.
However if you are writing your own pardump file or using the output for other purposes in a high altitude area, you may
wish to take this into account.

SIGMA-H is the horizontal puff size in meters.

VEL-W is the current value for the turbulent velocity in the vertical in m/s

VEL-V is the current value for the turbulent velocity in the horizontal in m/s

Currently VEL-U is not written to the pardump file and when the model is initialized from a pardump file, it assumed that vel-u = vel-v.

POLLUTANT is an integer, N, which corresponds to the Nth pollutant species defined in the CONTROL file. Pollutant definition

METEO-GRID is n integer, N, which corresponds to the Nth meteorological data grid defined in the CONTROL file.

SORT-INDEX Each particle or puff is assigned its own unique sort-index. The sort index is used within HYSPLIT for looping through all the computational particles or puffs. If a computational particle is removed during the simulation, the sort indices are reassigned so that there are only as many sort indices as particles. Consequently, the sort index for a computational particle may change during a simulation. If ichem=8, then particle deletion is turned off, and the sort index will refer to the same computational particle throughout the simulation. In the case of puffs, the sort indices are reassigned when puffs are deleted, merged or split.

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