The SMOKE system uses a more advanced emissions modeling approach for biogenic processing than it uses for the other source types. For biogenic emissions, the temporal processing is a true simulation model driven by ambient meteorology and other data. SMOKE currently supports two methods for computing biogenic land use: BEIS2 and BEIS version 3.09 and version 3.13 (hereafter referred to as BEIS3). The overall processing performed by both these models is quite different from the processing done for anthropogenic source categories. BEIS2 and BEIS3 start with spatial allocation of land use data as the first processing step (which is the same as importing the raw inventory data for anthropogenic sources). They next compute normalized emissions for each grid cell and land use category. The final step is adjusting the normalized emissions based on gridded, hourly meteorology data and assigning the chemical species to output a model-ready biogenic emissions file. The following two subsections provide more detail about the two biogenic models in SMOKE and give references to additional detail elsewhere.
SMOKE/BEIS2 can use either county land use or gridded land use data to generate the normalized emissions values. The land
use types that must be provided are specific to BEIS2 and can be created from either the BELD2 or BELD3 land coverage datasets.
The SMOKE Beld3to2 program can take the BELD3 data used in BEIS3 modeling and convert them for use in BEIS2 modeling. The Rawbio program uses either a county land use file (BCUSE) or gridded land use file (BGUSE), and it also uses BEIS2 normalized emission factors for either summer or winter. If the county land use data are used, Rawbio requires a spatial surrogates file (BGPRO) for spatially distributing the emissions to the grid cells. It combines these data and outputs normalized biogenic emissions.
If both summer and winter emission estimates will be included in the temporal allocation step, then Rawbio must be run twice--once for summer and once for winter.
The next step in creating biogenic emissions is making hour-specific adjustments to the normalized emissions based on the hourly gridded meteorology. The Tmpbio program reads the MCIP meteorology data and makes these adjustments; these include the effects of temperature and solar radiation. The winter emission factors are to be used during the winter period, which is defined as being after the first date of freezing ground temperature and before the last date of freezing ground temperature. The SMOKE Metscan program can determine this time period and create a gridded file that indicates whether each grid cell is in a winter or summer period for each day of the year. Using this file, which is optional, will cause Tmpbio to read and use both the winter and summer normalized emissions files from Rawbio. Whether the winter or summer normalized emissions are used for a given grid cell and hour is set by the output from the Metscan program.
Users can define the chemical species that are output from Tmpbio using the speciation profiles file, GSPRO. In this file you can set an environment variable (BIOG_SPRO) that indicates which speciation profile code should be used for biogenic emissions. Tmpbio looks for the “inventory pollutants” OVOC, NO, and TERP in the GSPRO file and splits and/or aggregates these data as specified by the chosen speciation profile. Tmpbio outputs two files with hourly, gridded, and speciated data, one file in moles/hour and a second file in grams/hour. The moles/hour
file must be combined with the anthropogenic files to create model-ready emissions and perhaps convert its units to moles/second
for CMAQ, which is explained in Section 2.18, “Creating model-ready emissions”. The grams/hour file can be read by Smkmerge to create state and county total emissions reports.