Simulations using Emissions Grids

Simulations using Emissions Grids
Previous	HOME	Next	HIGHLIGHTS Complex emission scenarios Emissions matrix Defining an emissions file

There are two approaches to modeling more complex emission scenarios. The first is an extension of the use of the CONTROL file in creating an emission matrix using three locations, the first two representing the lower left and upper right grid corners, respectively, and the third point representing the grid spacing, similar to what was done for the trajectory error example shown previously. In this case we will start sources every 0.5 degrees between the grid corners (27.0, -82.0) and (30.0, -79.0). The model is then run from the Concentration / Special Simulations / Run Matrix menu. Run with all the settings from the previous example for Florida except change the output to a 6 hour average concentration instead of a snapshot.

Prior to executing the model, the initial 3-location CONTROL file is automatically rewritten to a new CONTROL file showing 49 locations. From the Concentration Display menu turn off the source location labeling (see graphic below) before creating the 6-h average concentration graphic (bottom left) for each of the 49 source locations. This graphic may be too noisy for some applications so there is an option to remove the black contour lines from the graphic. Set the contour outlines to none in the Concentration Display menu and execute the display to create a considerably simplified graphic (below right).

The modified CONTROL file could also be edited manually to customize the emission rate.

Another approach is to define an emissions file, which tabulates hourly emission rates by location. An emission text file, defines the grid to which those emissions data will be accumulated. A simulation using this approach for the same case is shown to the right. The CONTROL file must define the lower left and upper right corners of the desired emission domain, which may be larger or smaller than the data available. The results shown here are almost identical to the control file emission run. The MESSAGE file shows that 49 sources were simulated using the emission file. Due to the continuous emissions at many locations, these simulations may require the maximum number of particles be increased from the default value. Information on the format of the emissions file and the emission text file can be found in the HYSPLIT User's Guide under Advanced / Special Topics (S441).

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