When an air dispersion modeling project requires emission variations that do not follow a repeating schedule, it can be a challenge to input the data to the model. Both AERMOD and CALPUFF come equipped with variable emissions options, but the options for temporally-varying emissions are fixed to repeating schedules (e.g., same hours every day or season, whole months, etc.).
What happens when emissions change from one hour to the next? The CALPUFF modeling system allows modelers to input specially-formatted external source emission files, and CALPUFF View has a number of visualization options for these files.
File specifications for CALPUFF external source files can be found in the appropriate user guide for the CALPUFF modeling system being employed (i.e., EPA-Approved, Version 6 / 7).
In CALPUFF View, go to the CALPUFF | External Source Files menu option.
The External Source Files window will appear. Supported source types vary by model version as shown below.
EPA-Approved / Version 6 (top) and Version 7 (bottom) modeling system external source types
Click the Add File button to add the source-specific file to the project. The buttons on the right side of the window provide additional tools for analyzing this data:
Building Downwash (BPIP) can be processed for external point sources
The file can be opened in a text editor (View) for editing
Source data are summarized in tabular view (Grid) for quick verification
Graph view to depict emissions variations in both graph and tabular displays
Window buttons for Point (left) and other (right) source types
Emissions variation graph for point sources
Once the files have been added, the external sources will be depicted using different colors in CALPUFF View’s main display. These colors can be customized using the Graphical Options Color Mapping settings.