The AERMOD model supports many different forms of output to support the needs of modelers. The most common form of output is that of high values – concentrations not paired in time across the domain but ranked in order from highest to lowest for each individual receptor. There are situations which may require the modeler to analyze output from one or more individual hours or averaging periods. For these tasks, AERMOD can prepare an output file called the Post-Processing File (model keyword POSTFILE).
Post-Processing File Options in AERMOD View
Each POSTFILE requires a few input elements:
Averaging Period: Select the time step you wish to analyze. Output for each receptor at each time step will be written to the file. In the screenshot above, output at every 3-hour interval would be published.
Source Group ID: Identify the source group of interest. You can create one POSTFILE for each Averaging Period + Source Group ID combination.
Format: Choose from binary (UNFORM) or ASCII text (PLOT). Use the latter if you want to analyze the output using third-party software (e.g., large text file editors) as the binary option will not be readable.
File Name: Assign a unique file name.
A useful feature of AERMOD View which utilizes the POSTFILE output, is the ability to create hourly Plume Animations. As described in one of our previous Modeling Tips, the Plume Animation option creates a 1-hour average POSTFILE for each selected source group resulting in contour plots for each individual hour. These plots can then be animated and recorded.
Plume Animation File Options in AERMOD View
One important thing to keep in mind about POSTFILEs is that they can be prohibitively large in size. Make sure you have adequate disk space before starting your model run to avoid run failures.