2.3 Test Air Concentration Calculation


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From the top bar of the main menu select the Concentration / Setup Run tab to open the setup menu. Press the Save button to close the menu, accepting the default settings. Then select the Concentration / Run Model tab which immediately starts the concentration model calculation. When it completes, press the Exit button to close the window. Then select the Display / Concentration / Contours tab to open the display menu. Press the Execute Display button to show the test case concentration result.

  1. The Setup Run menu creates a CONTROL file which contains the starting time, location, name of the meteorological data file, details of the pollutant emission, concentration grid, and output file name.

  2. The Run Model tab starts the concentration model simulation which creates a binary gridded concentration output file called cdump.

  3. The Concentration Display tab runs a concentration plotting program which reads the binary air concentration cdump file to create the Postscript graphics file concplot.ps.

  4. The final plume Postscript graphic is automatically displayed using Ghostview.

  5. All the output files are written to the HYSPLIT working directory and in addition to the above named files the directory also contains diagnostic files such as MESSAGE, VMSDIST, CONC.CFG, and if needed WARNING.

The display of the air concentration plume graphic means that all the HYSPLIT components have been correctly installed. In the unlikely event that the installation failed and the graphic was not displayed suggests that there may be issues requiring system administrator support. Consider the following:

  • You have permission to install software.
  • You have write permission to the directories in which the software was installed.
  • You are not installing on top of a previous version of HYSPLIT.

Because a plume simulation may consist of thousands of individual trajectories but with an additional turbulent component to the motion to account for atmospheric dispersion, the simpler trajectory calculation will be explored first in more detail in the next few sections.