Excerpt from: http://vista.cira.colostate.edu/TSS/Results/Emissions.aspx

Emissions Methods: Wild and Prescribed Fire Emissions

Fire Emissions

Fire emissions data for SMOKE have traditionally been represented as county-level area-source 

inventories that were placed in only the first vertical model layer. The representation of fire 

emissions for air quality modeling was enhanced by preparing the inventory data as point sources 

with specific latitude-longitude coordinates for each fire centroid and pre-computed plume rise 

parameters that were derived from individual fire characteristics. These new inventories consist 

of annual, daily, and hourly IDA-formatted emissions inventory files and ancillary data for 

allocating the inventories in space, time, and to the Carbon Bond-IV chemistry mechanism used 

in CMAQ and CAMx. The development of the fire emissions inventory is described in this

section. 

Source Categories

The fire emission inventories developed for the WRAP modeling efforts were organized into the 

following individual categories:

 Wildfires

 Agricultural fires 

 Wildland fire use

 Natural prescribed 

 Anthropogenic prescribed

 Non-Federal rangeland fires

 non-WRAP fires

For the non-WRAP fire emissions inventory, most of the data were modeled as area sources, with 

the exception of fire emissions for Canada, which were treated as elevated point sources.

The development of the fire emission inventory is described below. The discussion focuses on 

the development of the 2002 Base inventory; emissions modeling for the 2002 Planning 

inventory and the 2018 base year inventory use the same processing approach. Variations to the 

modeling approach and specific revisions and enhancements incorporated into the final modeling 

versions of the inventories have been described previously (refer to the Emission Overview 

Documentation). Specific revisions are noted with respect to data sources and source categories 

for the Plan02 and Base18 emissions inventories. 
Data sources

For the fire inventories in Base02 inventory, actual 2002 data were used as developed by the 

RPOs for the U.S., version 2 of the year 2000 Canadian inventory, and actual 2002 data for 

Ontario, Canada. There were no fire emissions in the BRAVO 1999 Mexico inventories, so 

Mexican fires were not included in the Base02 inventories. The inventories used consisted of 

both area- and point-source data for the U.S. and Canada. Air Sciences provided the WRAP 

inventories divided among six different fire categories: wildfires, agricultural fires, wildland fire 

use, natural prescribed, anthropogenic prescribed, and non-Federal rangeland fires (Air Sciences, 

Inc., 2005). These inventories consisted of annual, daily, and hourly IDA-formatted files with 

information on daily emissions totals and hourly plume characteristics for each fire. Similar point

source fire inventories for the VISTAS states were received from Alpine Geophysics (Stella, 

2005). In addition, county-level fire inventories represented as area sources for the VISTAS and 

CENRAP states were also included. Monthly temporal profiles received from Alpine 

Geophysics were used to distribute these annual inventories throughout the year. The area source 

inventories for the rest of the RPOs and Canada also contained fire emissions that were not 

distributed separately. These sources were modeled with the rest of the stationary-area-source 

sector. Finally, a 2002 fire inventory for Ontario, Canada was received from MANE-VU and 

formatted to take advantage of the SMOKE fire plume rise algorithm (Pouliot et al., 2005). 

For the development of the Plan02 inventories, the RMC received corrected U.S. data for only 

the updated portions of the Base02 inventories. The previous inventory data for the affected 

states were removed from the files used in the Base02 modeling and combined the remaining 

data with the updated information to build revised Base02 inventories. The resulting dataset was 

used to develop the Plan02 inventory. This substitution of only the revised portions of the 

inventories was a general approach applied to several emissions sectors. More specific 

approaches were also developed for preparing the Plan02 fire inventories as described below. 

Air Sciences, Inc., provided annual Baseline Phase III fire inventories for each of the five fire 

categories (wildfires, agricultural fires, prescribed fires, non-Federal rangeland prescribed fires, 

and wildland fire use) as three-file sets for each category. Consistent with the fire inventories for 

Phases I and II, each fire category consisted of an annual IDA file with physical fire event 

information, a daily IDA file with daily emissions by criteria pollutant, and an hourly IDA file 

with hourly pre-computed plume rise values. Upon receiving these data, the annual inventories 

are split into monthly files to avoid computer memory problems related to processing very large 

inventories with SMOKE. Additional information on the development of these fire inventories is 

available in WRAP-FEJF (2006).

Baseline fire emission inventories for 2018 (Base18a) for WRAP, CENRAP, and VISTAS were 

held constant at Plan02 emission levels. For the 2018b inventory, a number of revisions were 

incorporated as follows:

 The WRAP inventories for prescribed and agricultural fires were updated and errors 

corrected in the application of temporal and speciation profiles for non-Federal rangeland 

prescribed fires. 

 Air Sciences, Inc. provided revisions to the Phase III prescribed and agricultural fire 

inventories to estimate the emissions reductions from applying fire emissions reduction 
techniques (ERTs) to controllable fire emissions (Randall, 2006). They based the revised 

emissions on the same data that the RMC used in case Plan02b to illustrate the changes 

that resulted from controlling prescribed and agricultural fires between the Plan02b and 

Base18b emission scenarios.

 The temporal and speciation profiles applied to the non-Federal rangeland prescribed fires

were corrected. By not adding the SCC for this source to the input cross-reference files in 

the Plan02 and Base18a inventories, default temporal and speciation profiles were 

mistakenly applied to these emissions. The appropriate cross-reference for this source 

were added to the SMOKE input files in case Base18b. 

Emissions processing

SMOKE is instrumented to distribute point-source-formatted fire inventories to the vertical 

model layers either by using a pre-computed plume rise approach or by computing the plume rise 

dynamically using actual 2002 meteorology. Both approaches for modeling point source fire 

emissions were applied for the Base02 inventories. For the pre-computed plume rise approach, 

SMOKE reads an annual inventory file with information on fire locations, a daily inventory file 

with daily emission totals for each fire, and an hourly inventory file with hourly plume bottom, 

plume top, and layer 1 fractions for each fire. SMOKE uses this information to locate the fires on 

the horizontal model grid and to distribute the plume of each fire vertically to the model layers. 

Because some of these fires have plumes that reach the model top, the number of emissions 

layers for processing these inventories are set to the full 19 layers of the meteorology. This 

approach was applied to the point-source fires for the WRAP and VISTAS regions.

The alternative plume rise approach uses information on fuel loading and the heat flux of the 

fires to distribute the fires vertically to the model layers. The data are provided to SMOKE in the 

form of an annual inventory with information on fire locations and a daily inventory with daily 

emission totals for each fire, daily heat flux, and daily fuel loading. This approach to the point

source fires was applied for Ontario, Canada. 

All of the point-source fires used diurnal temporal profiles and speciation profiles for VOC and 

PM2.5 developed by Air Sciences during the preliminary 2002 modeling (Tonnesen et al., 2005). 

For the area source fires outside of the WRAP region, including Canada, monthly temporal 

profiles developed by VISTAS were applied.. While these profiles appear to be an improvement 

over the EPA defaults, they are specific to the VISTAS region and will misrepresent the 

seasonality of the fires in other regions of the modeling domain. Flat weekly temporal profiles, 

and the diurnal profiles developed by Air Sciences were also used in the fire emissions modeling. 

In addition, the forestland spatial surrogates were used to distribute these county level (province 

level for Canada) data to the model grid. Using spatial surrogates to locate fires is a crude 

approach that results in the artificial smearing of the emissions over too large an area. Both of 

these issues can be remedied by moving to a point source approach for representing these fires, 

similar to the approach used by Air Sciences for preparing the WRAP fire inventories. 
The RMC discovered several errors with the WRAP Phase II inventories. Some of these errors 

were fixed with corrections made by the RMC with guidance from Air Sciences, and others will 

be addressed by Air Sciences in Phase III of the 2002 WRAP fire inventories. The errors 

identified, with corrections, were as follows: 

 Missing or malformed dates in several agricultural burning events in CA. These events 

were intended to be dropped and were ultimately deleted from the inventories by the RMC.

 Missing dates in several prescribed burning events in AZ. These records were corrected 

by Air Sciences and redistributed to the RMC.

 Inconsistencies between the records in the hourly and annual inventory files for several 

agricultural burning events in CA. These records were corrected by Air Sciences and 

redistributed to the RMC. 

The quality assurance of the fire emissions followed the WRAP emissions modeling QA protocol

(Adelman, 2004) and a suite of graphical summaries. Tabulated summaries of the input data and 

SMOKE script settings were used to document the data and configuration of SMOKE. The 

graphical QA summaries include, for all emissions output species, daily time-series plots, annual 

time-series plots, and daily vertical profiles. These QA graphics for the 2002 inventories are 

available at http://pah.cert.ucr.edu/aqm/308/QA_base02a36.plots/allf/plots/.

Gridded Fire Emission Inventory Summaries

Summaries of the gridded fire source emissions for the Base02b, Plan02c and Base18b 

inventories by state and county, annual and seasonal periods, can be found on the TSS at: 

http://vista.cira.colostate.edu/tss/Results/Emissions.aspx. 

References

Adelman, Z. 2004: Quality Assurance Protocol – WRAP RMC Emissions Modeling with SMOKE, 

Prepared for the WRAP Modeling Forum by the WRAP Regional Modeling Center, Riverside, CA.

Air Sciences, Inc., 2005: 2002 Fire Emission Inventory for the WRAP Region – Phase II, Prepared for 

the Western Governors Association/WRAP by Air Sciences, Inc., Denver, CO.

Pouliot, G., T. Pierce, W. Benjey, S.M. O’Neill, and S.A. Ferguson, 2005: Wildfire Emissions Modeling: 

Integrating Blue Sky and SMOKE, in Proceedings of the 14th Annual Emissions Inventory 

Conference, Atlanta, GA. 

Randall, D., 2006: Technical Memorandum: Fire Emissions Inventory – Phase III Base-Control Case, 

Prepared for Western Regional Air Partnership Fire Emissions Joint Forum by Dave Randall, Air 

Sciences, Inc., April 28, 2006. 

Tonnesen, G. et al., 2005: Final Report for the WRAP RMC for the Project Period March 1, 2004 

through February 28, 2005, Prepared for the Western Governors Association by ENVIRON 

International Corporation, Novato, CA. 

http://pah.cert.ucr.edu/aqm/308/ppt_files/emissions/nh3/Volume_I_FinalReport.3-07.pdf
WRAP-FEJF (WRAP-Fire Emissions Joint Forum). 2006. WRAP Phase III & IV Fire Emission 

Inventories for the 2000-04 Baseline Period and 2018 Project Year. Western Governors Association 

– wrapair.org website. (http://www.wrapair.org/forums/fejf/tasks/FEJFtask7Phase3-4.html).