The SOURCE_GROUPS file is used to define groups of sources when processing emissions for source apportionment. Movesmrg and Smkmerge read this file when SMK_SRCGROUP_OUTPUT_YN is set to Y.

When reading the SOURCE_GROUPS file, SMOKE will skip lines with data that doesn't apply to the current source category. Lines that contain a plant ID or point ID will be skipped when processing area, biogenic, or mobile sources. Lines containing an SCC will be skipped when processing biogenic sources.

If SMOKE encounters lines with duplicate grouping information (i.e. FIPS, SCC, point source characteristics), an error will be printed to the log and the program will quit.

Multiple grouping criteria can be assigned to the same source group ID by using additional lines. In the example below, all sources with SCCs 2102001000, 2102002000, and 2102004000 will be assigned to source group 1.

1 0 2102001000
1 0 2102002000
1 0 2102004000

If the source grouping file contains a line with all blank or zero source characteristics, SMOKE will use the given source group number as the default group rather than zero. For example, if the following line is included in the SOURCE_GROUPS file, the default source group number will be 40 instead of 0.

40 0 0 0 0  # default group number will be 40 instead of 0

The format of the SOURCE_GROUPS file is shown in Table 6.102, “Format for SOURCE_GROUPS”.