Hello…I’m a bit new to CMAQ still. But i was wondering what the option for setting the variable GR_EM_SYM_DATE to T or F does.
Briefly, this flag and the corresponding flag for inline point sources (STK_EM_SYM_DATE_###) allows you to provide “representative day” offline emission files (gridded and/or inline point sources) for some or all emission streams, i.e. emission files that have a date other than the date for which the model simulation is being performed. Without this flag set to T for a given stream, the model will crash if the date and time for which the simulation is being performed cannot be found in the emissions file specified for that stream.
Please see the following links for additional documentation:
overview of offline emissions configuration
defining and configuring gridded offline emission streams
defining and configuring inline point source emission streams
Please also see this known issue for CMAQv5.3.1 and use the stream-specific environment variables (GR_EM_SYM_DATE_### and STK_EM_SYM_DATE_###) instead of the global environment variable EMIS_SYM_DATE if you want to implement representative day emissions for some or all of your emission streams.