United States Air and Energy Engineering

Environmental Protection Research Laboratory

Agency Research Triangle Park, NC 27711

Research and Development EPA/600/SR-95/004 February 1995

E AP

The Development and

Improvement of Temporal

Allocation Factor Files

Theresa Moody, J. David Winkler, Terry Wilson, and Sharon Kersteter

Project Summary

Emissions inventories have traditionally been developed to produce

estimates of annual or daily emissions. To be used as input to photochemical and other atmospheric

simulation models, hourly emissions

estimates are usually required. Ideally, hourly emissions would be measured or calculated directly at the

emissions source; however, this approach is normally impractical due to

technical and resource restraints. As

an alternative, hourly emissions estimates can be obtained using surrogate temporal allocation factors from

"temporal profiles" assigned to specific emissions source categories.

Hourly emissions may then be estimated by applying the appropriate

temporal allocation factors to available annual, seasonal, or daily emissions 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 simulation 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 estimates 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 improvements to the current methods for

developing temporal allocation factors,

and to collect and use data to improve

an existing temporal allocation factor

(TAF) file. The TAF file will be used as

a source of national default allocation

factors by the emissions model processing systems that calculate temporally 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 documented in a separate report of the same

title (see Project Report ordering information at back).

Methodology

Relevant literature references were identified, 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 developed to date was found to be those for

the NAPAP effort. Major limitations of the

NAPAP factors are that they were developed 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 pertaining to production/consumption from

various energy industries

• California Air Resources Board

(CARB) AB-2588 “Hot Spots”

pooled source test reports
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• Texas Air Control Board (TACB)

stationary source operating schedule 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 resource recovery facilities; acidmodes field study data; and Urban

Airshed Model Emissions Preprocessor System temporal profiles

Source Category Prioritization

Emissions source categories were prioritized to ensure attention for categories

that are major national contributors to air

pollution. The prioritization reflected only

point source data available from the Aerometric 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 Register notice were reviewed. This notice

listed industry groups and source categories targeted for Maximum Achievable Control 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 combine these data, a number of intermediate

data processing steps were required. The

product of this effort was a single TAF file

in a flat ASCII format. Figure 1 shows the

final TAF file format. Key fields for this file

are AIRS Source Classification Category

(SCC) code, season (winter, spring, summer, fall), and a day code (weekday, Saturday, 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 TAF file also

includes hourly allocation factors for hours

00 through 24, along with a flag to identify

the source of these data. The final TAF

file resides on EPA's mainframe computer

at the National Computer Center in Research Triangle Park, NC.

A three-tiered approach was used to

produce the final TAF file data. Tier 1

provided a baseline TAF file, covering all

source categories, but including only

monthly data. Tier 1 data are useful for

constructing seasonal allocation profiles.

These profiles were constructed predominantly 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 temporal resolution for a large number of categories. 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

CARB reports, CEM data, and other data

sources. The data in the Tier 3 files represent efforts focused on improving the default operating profiles for a few important

emissions sources. Tier 3 data are the

most detailed and desirable data available in the final TAF 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 TAF file is well-documented, allowing future updates and improvements. TAF profiles are based on

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 TAF file data

was developed for this project. A limited

implementation of the plan for the highest

priority SCC categories revealed inconsistent and unexpected data for some SCC

categories. Resources available for this

project did not permit review of all SCC

categories. Inconsistencies in TAF profiles 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

TAF 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 TAF profiles for

electric utilities.

This project focused primarily on improving temporal profiles for stationary

point sources. TAF 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

Field Field

Variable Name Format Width Description/Validation

______________________________________________________________________________________________________________________________________________________________________________________________________________________

SCC Numeric 10 Source Classification Code (Point area or mobile)

DAY_CODE Numeric 1 Day scenario identifier

(1=Weekday, 2=Saturday, 3=Sunday)

SEA_CODE Numeric 1 Season scenario identifier

1=Spring, 2=Summer, 3=Fall, 4=Winter)

DAY_FRAC Real 7.5 a Day scenario fraction

(65 x weekday fraction) + (13 x Saturday fraction)

 + (13 x Sunday fraction) = 1.0

SEA_FRAC Real 7.5 a Seasonal scenario fraction

(Spring fraction + Summer fraction + Fall fraction

 +Winter fraction = 1.0)

SEA_FLAG Character 4 Seasonal profile data source or combination

method identifier

DAY_FLAG Character 4 Daily profile data source or combination method

identifier

HOUR_FLAG Character 4 Hourly profile data source or combination method

identifier

HOUR1-HOUR24 Real 7.5 Diurnal profile

______________________________________________________________________________________________________________________________________________________________________________________________________________________

a 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.
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approach was beyond the scope of this

project and would require additional calendar time and resources to design the

surveys, obtain Office of Management and

Budget clearance, and perform the surveys. One product of this study was statistical methods for the analysis of temporal

data. The application of these methods to

quality assure the TAF file data would be

appropriate. In addition, the development

of computer software to access and analyze the TAF file data was recommended.

The availability of an improved TAF file

does not eliminate the need to collect

actual data for temporally resolved emissions when these data are needed for an

emissions inventory. Whenever inventory

development resources permit, actual data

should still be collected and quality assured for inventory projects where seasonal, daily, or hourly emissions estimates

are needed. The TAF file provides an

improved database of default values that

should be used when actual data cannot

be collected.

used to improve point source data for

additional categories and to expand the

geographic base for point source temporal data. The report lists recommendations 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
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United States

Environmental Protection Agency

Center for Environmental Research Information

Cincinnati, OH 45268

Official Business

Penalty for Private Use

$300

EPA/600/SR-95/004

BULK RATE

POSTAGE & FEES PAID

EPA

PERMIT No. G-35

Theresa Moody, J. David Winkler, Terry Wilson, and Sharon Kersteter are 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