This menu calls a utility program that can be used to adjust the particle positions prior to restarting the simulation from a saved particle position file. The particle position file needs to be written by setting the appropriate namelist parameter as described in the Advanced/Configuration Setup/Concentration menu tab. Normally observational data should be consulted prior to making any adjustments to the particle positions. Positions are only shifted horizontally and not vertically. The same horizontal adjustment is applied at all heights. If a height adjustment is required, the model should be re-run with a different initial particle height distribution.
One or more particle files may be processed by a single execution. A standard simulation only generates one particle output file containing positions at one or more time periods. Multiple particle position files, with a three-digit suffix (.001, .002, etc), are automatically generated by the ensemble version of the model. The adjusted output is always written to a new file name, defaulting to PARINIT, also the default name for initializing a new simulation.
Regardless of how many time periods are contained in the particle position file, the adjustment is only applied to one time period, normally the initialization time period for the next simulation. If the time field (-t) is not specified, then the adjustment occurs to the first time period in the file, otherwise the adjustment is applied to the MMDDHH designated in the time argument. Only this one time period is written to the output file, regardless of how many time periods are contained within the input file.
A particle position shift can be specified as an angular adjustment in degrees and distance from a fixed location (such as the particle source point). A shift may also be specified as a window translation, where all particles within a given latitude-longitude window are shifted by a specified number of degrees in latitude and longitude. No particles outside of the window or beyond the radius are shifted unless the blending (-b) flag is set. In this case, the shift is applied to each particle in a linearly decreasing fashion to zero adjustment at a distance of two windows.
The spatial adjustment of the particle positions in the HYSPLIT binary particle output file are specified on the command line (or through the GUI) as follows:
The particle position file may be converted to a binary concentration file through the command line utility program par2conc.