United States
Environmental Protection
Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park, NC 27711
Research and Development
EPA/600/SR-95/004 February 1995
EPA Project Summary
The Development and
Improvement of Temporal
Allocation Factor Files
Theresa Moody, J. David Winkler, Terry Wilson, and Sharon Kersteter
Emissions inventories have tradi-
tionally been developed to produce
estimates of annual or daily emis-
sions. To be used as input to photo-
chemical and other atmospheric
simulation models, hourly emissions
estimates are usually required. Ide-
ally, hourly emissions would be mea-
sured or calculated directly at the
emissions source; however, this ap-
proach is normally impractical due to
technical and resource restraints. As
an alternative, hourly emissions esti-
mates can be obtained using surro-
gate temporal allocation factors from
"temporal profiles" assigned to spe-
cific emissions source categories.
Hourly emissions may then be esti-
mated by applying the appropriate
temporal allocation factors to avail-
able annual, seasonal, or daily emis-
sions values. This approach has been
followed in previous air pollution
studies, including the National Acid
Precipitation Assessment Program
(NAPAP) and the Northeast Corridor
Regional Modeling Project. Since the
performance of atmospheric simula-
tion models is dependent upon the
availability of accurate, temporally
resolved emissions values, suitable
methodologies and databases must
be available to personnel responsible
for developing the daily emissions es-
timates needed for model inputs.
The purposes of this project were to
evaluate the quality and completeness
of data and methods being used for
temporal allocation of emissions data,
to identify and prioritize needed im-
provements to the current methods for
developing temporal allocation factors,
and to collect and use data to improve
an existing temporal allocation factor
(TAP) file. The TAP file will be used as
a source of national default allocation
factors by the emissions model pro-
cessing systems that calculate tempo-
rally resolved emissions estimates for
model input.
This Project Summary was developed
by EPA's Air and Energy Engineering
Research Laboratory, Research Triangle
Park, NC, to announce key findings of
the research project that is fully docu-
mented in a separate report of the same
title (see Project Report ordering infor-
mation at back).
Methodology
Relevant literature references were iden-
tified, acquired, and reviewed to evaluate
the quality and completeness of data and
methodologies being used for temporal
allocation of emissions data. The most
comprehensive set of temporal factors de-
veloped to date was found to be those for
the NAPAP effort. Major limitations of the
NAPAP factors are that they were devel-
oped only for the NAPAP point and area
source categories and were incompletely
documented. To augment these data, the
following data sources were identified:
Business and labor statistics data
Department of Energy data pertain-
ing to production/consumption from
various energy industries
California Air Resources Board
(CARS) AB-2588 "Hot Spots"
pooled source test reports
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Texas Air Control Board (TACB)
stationary source operating sched-
ule data
Southern Oxidant Study (SOS) data
Lake Michigan Ozone Study
(LMOS) data
Continuous Emissions Monitoring
(CEM) data
Other data sources, including
wastewater data from publicly
owned treatment works; operating
schedule/parameter data from re-
source recovery facilities; acid-
modes field study data; and Urban
Airshed Model Emissions Prepro-
cessor System temporal profiles
Source Category Prioritization
Emissions source categories were pri-
oritized to ensure attention for categories
that are major national contributors to air
pollution. The prioritization reflected only
point source data available from the Aero-
metric Information Retrieval System (AIRS)
Facility Subsystem. National area and
mobile source emissions data were not
available at the time of this study. To
check for consistency with previous U.S.
Environmental Protection Agency (EPA)
efforts, high priority source categories listed
in the September 24, 1992, Federal Reg-
ister notice were reviewed. This notice
listed industry groups and source catego-
ries targeted for Maximum Achievable Con-
trol Technology standard development.
The comparison demonstrated consistency
with the earlier prioritization effort.
Temporal Allocation Factor File
Development
Data were collected for the high priority
source categories. To process and com-
bine these data, a number of intermediate
data processing steps were required. The
product of this effort was a single TAP file
in a flat ASCII format. Figure 1 shows the
final TAP file format. Key fields for this file
are AIRS Source Classification Category
(SCC) code, season (winter, spring, sum-
mer, fall), and a day code (weekday, Sat-
urday, or Sunday). For each record in the
file, day and seasonal scenario fractions
are given, along with flags to identify the
sources of these data. The TAP file also
includes hourly allocation factors for hours
00 through 24, along with a flag to identify
the source of these data. The final TAP
file resides on EPA's mainframe computer
at the National Computer Center in Re-
search Triangle Park, NC.
A three-tiered approach was used to
produce the final TAP file data. Tier 1
provided a baseline TAP file, covering all
source categories, but including only
monthly data. Tier 1 data are useful for
constructing seasonal allocation profiles.
These profiles were constructed predomi-
nantly using monthly labor statistics and
energy consumption data. Tier 1 data were
used only for sources not included in Tier
2 or 3. Tier 2 data provide increased tem-
poral resolution for a large number of cat-
egories. Tier 2 data were created based
on information from TACB, SOS, and
LMOS for specific sources. These files
provided hourly profiles. Tier 2 data were
used for emissions sources not included
in Tier 3. Tier 3 data were developed from
CARS reports, CEM data, and other data
sources. The data in the Tier 3 files repre-
sent efforts focused on improving the de-
fault operating profiles for a few important
emissions sources. Tier 3 data are the
most detailed and desirable data avail-
able in the final TAP file.
Analysis and Conclusions
This project created comprehensive,
well-documented, representative national
default allocation profiles that may be used
to generate hourly emissions estimates
from annual estimates. The methodology
used to create the TAP file is well-docu-
mented, allowing future updates and im-
provements. TAP profiles are based on
Variable Name
Field
Format
Field
Width
activity, rather than emissions, making
them valid for allocating the emissions of
any pollutant. Still, there are many source
categories for which further improvements
would be desirable. Detailed, Tier 3 level
data could be collected and analyzed for
high priority categories.
A plan for analyzing the TAP file data
was developed for this project. A limited
implementation of the plan for the highest
priority SCC categories revealed inconsis-
tent and unexpected data for some SCC
categories. Resources available for this
project did not permit review of all SCC
categories. Inconsistencies in TAP pro-
files for electric utility boiler categories were
traced to CEM data. It was determined
that the CEM data obtained for this project
were inappropriate for the calculation of
TAP profiles. The CEM data, consisting of
only concentration measurements, were
found not to be accurate indicators of
source activity levels. The CEM data were
removed from the final TAP profiles for
electric utilities.
This project focused primarily on im-
proving temporal profiles for stationary
point sources. TAP profiles for many point
source categories were improved as the
result of this effort. A number of other
data sources are available that could be
Description/Validation
SCC
DAY_CODE
SEA CODE
Numeric
Numeric
Numeric
DAY FRAC Real
SEA FRAC Real
SEA_FLAG
DAY_FLAG
HOUR FLAG
Character
Character
Character
HOUR1-HOUR24 Real
10 Source Classification Code (Point area or mobile)
1 Day scenario identifier
(1=Weekday, 2=Saturday, 3=Sunday)
1 Season scenario identifier
1=Spring, 2=Summer, 3=Fall, 4=Winter)
7.5a Day scenario fraction
(65 x weekday fraction) + (13 x Saturday fraction)
+ (13 x Sunday fraction) = 1.0
7.5 a Seasonal scenario fraction
(Spring fraction + Summer fraction + Fall fraction
+Winter fraction = 1.0)
4 Seasonal profile data source or combination
method identifier
4 Daily profile data source or combination method
identifier
4 Hourly profile data source or combination method
identifier
7.5 Diurnal profile
Field width for field type real is defined as X. Y, where X represents the field width and Y represents
the allowable number of digits to the right of the decimal.
Figure 1. Final TAF file format.
2
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used to improve point source data for
additional categories and to expand the
geographic base for point source tempo-
ral data. The report lists recommenda-
tions for additional data sets that could be
examined. On the other hand, only one
existing source of area source temporal
data could be obtained for this study. To
improve temporal profiles for area source
categories, it may be necessary to collect
new information through surveys of the
most important source categories. This
approach was beyond the scope of this
project and would require additional cal-
endar time and resources to design the
surveys, obtain Office of Management and
Budget clearance, and perform the sur-
veys. One product of this study was sta-
tistical methods for the analysis of temporal
data. The application of these methods to
quality assure the TAP file data would be
appropriate. In addition, the development
of computer software to access and ana-
lyze the TAP file data was recommended.
The availability of an improved TAP file
does not eliminate the need to collect
actual data for temporally resolved emis-
sions when these data are needed for an
emissions inventory. Whenever inventory
development resources permit, actual data
should still be collected and quality as-
sured for inventory projects where sea-
sonal, daily, or hourly emissions estimates
are needed. The TAP file provides an
improved database of default values that
should be used when actual data cannot
be collected.
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Theresa Moody, J. David Winkler, Terry Wilson, andSharon Kersteterare with TRC
Environmental Corp., Chapel Hill, NC 27514.
Charles O. Mann is the EPA Project Officer (see below).
The complete report, entitled "The Development and Improvement of Temporal
Allocation Factor Files," (Order No. PB95-166153; Cost: $52.00; subject to
change) will be available only from
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at
Air and Energy Engineering Research Laboratory
U. S. Environmental Protection Agency
Research Triangle Park, NC 27711
United States
Environmental Protection Agency
Center for Environmental Research Information
Cincinnati, OH 45268
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