SEPA
United States
Environmental Protection
Agency
Guidance for Estimating Natural Visibility
Conditions Under the Regional Haze Rule
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EPA-454/B-03-005
September 2003
Guidance for Estimating Natural Visibility
Conditions Under the Regional Haze Program
Contract No. 68-D-02-0261
Work Order No. 1-06
U.S. Environmental Protection Agency
Office of Air Quality Planning and Standards
Emissions, Monitoring and Analysis Division
Air Quality Trends Analysis Group
Research Triangle Park, NC
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DISCLAIMER
This report is a work prepared for the United States Government by Battelle. In no event
shall either the United States Government or Battelle have any responsibility or liability for any
consequences of any use, misuse, inability to use, or reliance upon the information contained
herein, nor does either warrant or otherwise represent in any way the accuracy, adequacy,
efficacy, or applicability of the contents hereof.
ACKNOWLEDGMENTS
The Environmental Protection Agency wishes to acknowledge the assistance and input
provided by the following advisors in the preparation of this guidance document:
Rodger Ames, National Park Service, Cooperative Institute for Research in the Atmosphere
(CIRA); Shao-Hang Chu, USEPA; Rich Damberg, USEPA; Tammy Eagan, Florida Dept. of
Environmental Protection; Neil Frank, USEPA; Eric Ginsburg, USEPA; Dennis Haddow, U.S.
Fish and Wildlife Service; Ann Hess, Colorado State University; Hari Iyer, Dept. of Statistics,
Colorado State University; Mike Koerber, Lake Michigan Air Directors Consortium; Bill
Leenhouts, U.S. Fish and Wildlife Service; William Malm, National Park Service (CIRA);
Debbie Miller, National Park Service; Tom Moore , Western Regional Air Partnership; Janice
Peterson, U.S. Department of Agriculture, Forest Service; Marc Pitchford, National Oceanic and
Atmospheric Administration, Air Resources Laboratory; Rich Poirot, State of Vermont, Dept. of
Environmental Conservation; Bruce Polkowsky, National Park Service; Tom Rosendahl,
USEPA; David Sandberg, U.S. Department of Agriculture, Forest Service; Jim Sisler, National
Park Service (CIRA); Tim Smith USEPA; Ken Walsh, SAIC.
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Guidance for Estimating Natural Visibility
Conditions Under the Regional Haze Program
TABLE OF CONTENTS
List of Figures iv
List of Tables v
Abbreviations and Acronyms vi
Glossary of Terms vii
1. INTRODUCTION 1-1
1.1 What is regional haze?
1.2 What is meant by the term "natural visibility conditions?"
1.3 What is the purpose of the Guidance for Estimating Natural
Visibility Conditions Under the Regional Haze Rule? 1-2
1.4 Does this guidance document apply to Tribal Class I areas as
well as mandatory Federal Class I areas? 1-3
1.5 What is the statutory and regulatory background for the
regional haze program? 1-4
1.6 What visibility metric will be used for estimating natural conditions,
setting goals, and tracking progress? 1-4
1.7 What are the key requirements and milestones for
State implementation plans, pertaining to the estimation of
natural visibility conditions under the regional haze rule? 1-5
1.8 What other factors should be considered in developing progress goals? .... 1-7
1.9 What progress reviews and future SIP revisions are required
under the regional haze rule? 1-8
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Guidance for Estimating Natural Visibility
Conditions Under the Regional Haze Program
1.10 Should estimates of natural visibility conditions reflect
contemporary conditions and land use patterns, or historic conditions? 1-9
1.11 What estimates of natural conditions are referenced in the regional haze
rule and preamble? 1-9
1.12 How are the natural visibility conditions at a mandatory
Federal Class I area determined? 1-10
1.13 What approaches for estimating natural conditions are discussed
in this guidance document? 1-10
1.14 How are natural emissions from fire taken into account in
estimates of natural PM and visibility levels? 1-12
1.15 How does the need to consider the fire component for natural
visibility conditions interface with EPA's general policies regarding
fire emissions? 1-13
1.16 Can a State delay submittal of its control strategy SIP and associated
mandatory Federal Class I area progress goals until it has developed
a "refined" estimate of natural conditions? 1-14
2. DEFAULT APPROACH TO ESTIMATING NATURAL
VISIBILITY CONDITIONS 2-1
2.1 What are the default estimates of the natural concentrations for the
PM2 5 components? 2-1
2.2 What should be done if the default estimate for any naturally contributed
species exceeds the corresponding measured concentrations? 2-2
2.3 How are the long-term relative humidity data used to determine
f(RH) values? 2-2
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Guidance for Estimating Natural Visibility
Conditions Under the Regional Haze Program
2.4 How is the default natural light extinction at a mandatory
Federal Class I area calculated? 2-4
2.5 How are the default bext values used to estimate natural
visibility in deciview units? 2-5
2.6 How are the 20% best visibility days and the 20% worst
visibility days determined in the default approach?
3. REFINED ESTIMATION APPROACHES REGIONAL
& SITE-SPECIFIC APPLICATION 3-1
3.1 Why might States want to use a refined approach to estimate
natural visibility conditions? 3-1
3.2 What are some of the approaches that could be used by States to
refine the default natural visibility estimates? 3-1
3.3 Which refined approach is most appropriate for States to use? 3-2
3.4 What should States do if they want to use a refined approach,
rather than the default approach to estimate natural visibility conditions? ... 3-2
3.5 How might an infrequent natural impact be quantified? 3-3
3.6 Can natural visibility estimates be made on a
sample-period-by-sample-periodbasis? 3-3
Appendix A - Annual Average f(RH) and Monthly Average f(RH)
Values at All Mandatory Federal Class I Areas A - 1
Origin of Relative Humidity and f(RH) Values A - 2
Appendix B - Default Natural bext, dv, and 10th and 90th Percentile
dv Values at All Mandatory Federal Class I Areas B-l
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Guidance for Estimating Natural Visibility
Conditions Under the Regional Haze Program
List of Figures
Figure 1-1 Example of method for determining mandatory Federal Class I area
rate of progress to be analyzed in SIP development process.
(a HI values for 2004 are based on 2000-2004 data, etc.) 1-6
Figure 1-2 Types of Data Used in Approach for Estimating
Natural Visibility Conditions 1-11
Figure 2-1 Estimates of the Default 10% Natural Haze Index Values (in dv)
(Note different color scales for the two parts of the figure) 2-9
Figure 2-2 Estimates of the Default 90% Natural Haze Index Values (in dv)
(Note different color scales for the two parts of the figure) 2-10
Figure A-l Monthly Average f(RH) Values for February
(all weather stations shown) A - 15
Figure A-2 Monthly Average f(RH) Values for May
(all weather stations shown) A - 16
Figure A-3 Monthly Average f(RH) Values for August
(all weather stations shown) A - 17
IV
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Guidance for Estimating Natural Visibility
Conditions Under the Regional Haze Program
List of Tables
Table 2-1 Average Natural Levels of Aerosol Components'1 2-2
Table A-l Values for f(RH) determined from the growth of ammonium sulfate A - 5
Table A-2 Recommended Monthly Site-Specific f(RH) Values for Each
Mandatory Federal Class I Area, Based on the Representative
IMPROVE Site Location A - 6
Table A-3 Monthly Site-Specific f(RH) Values for Each Mandatory Federal
Class I Area, Based on the Centroid of the Area
(Supplemental Information) A - 10
Abbreviations and Acronyms
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Guidance for Estimating Natural Visibility
Conditions Under the Regional Haze Program
b^ - Total light extinction
CAA- Clean Air Act
CAAA - 1990 Clean Air Act Amendments
CASTNet - Clean Air Status and Trends Network
CM - Coarse mass
EPA - United States Environmental Protection Agency
f(RH) - Relative humidity adjustment factor
IMPROVE - Interagency Monitoring of protected Visual Environments
LAC - Light absorbing carbon
Mm"1 - Inverse megameter (10~6 m"1)
NAAQS - National Ambient Air Quality Standards
NWS - National Weather Service
OC - Organic carbon
OMC - Organic carbon mass
OP - Pyrolized organics
PM - Particulate matter
PM2 s - Particulate matter with an aerodynamic diameter less than 2.5 microns
PM10 - Particulate matter with an aerodynamic diameter less than 10 microns
RH - Relative humidity
SIP - State Implementation Plan
TOR - Thermal optical reflectance
VI
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Conditions Under the Regional Haze Program
Glossary of Terms
Aerosols - Suspensions of tiny liquid and/or solid particles in the air.
Coarse mass - Mass of particulate matter with an aerodynamic diameter greater than 2.5 microns but
less than 10 microns.
Deciview (dv) - The unit of measurement of haze, as in the haze index (HI) defined below.
Default approach - The basic approach recommended by EPA to estimate the natural visibility
conditions. States may choose to adopt the default values for natural visibility conditions or, with
sufficient technical justification, propose alternatives to the basic approach or generate refined estimates.
EPA believes that the default values that are provided in this document are adequately justified and
believes that it can propose for approval States' use of them. However, EPA may not guarantee approval
prior to receiving and fully considering public comment on any proposed actions.
Default values - the values obtained from adopting the default approach to estimating natural visibility
conditions.
Fine particulate matter - particulate matter with an aerodynamic diameter less than 2.5 microns (PM25).
Fine soil - Particulate matter composed of material from the Earth's soil, with an aerodynamic diameter
less than 2.5 microns. The fine soil mass is calculated from chemical mass measurements of fine
aluminum, fine silicon, fine calcium, fine iron, and fine titanium as well as their associated oxides.
Haze index (HI) - A measure of visibility derived from calculated light extinction measurements, that is
designed so that uniform changes in the haze index correspond to approximately uniform incremental
changes in visual perception, across the entire range of conditions from pristine to highly impaired. The
haze index [in units of deciviews (dv)] is calculated directly from the total light extinction [bext expressed
in inverse megameters (Mm"1)] as follows:
HI = 10 In (bext/10)
Least-impaired days - The clearest, or least hazy, days.
Light absorbing carbon - Carbon particles in the atmosphere that absorb light; sometimes reported as
elemental carbon.
Light extinction - A measure of how much light is absorbed or scattered as it passes through a medium,
such as the atmosphere. The aerosol light extinction coefficient refers to the absorption and scattering by
aerosols, and the total light extinction coefficient refers to the sum of the aerosol light extinction
coefficient, the absorption coefficient of gases (such as NO2), and the atmospheric light extinction
coefficient due to molecular light scattering (Rayleigh scattering).
VII
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Guidance for Estimating Natural Visibility
Conditions Under the Regional Haze Program
Mandatory Federal Class I areas - Certain National Parks (over 6,000 acres), wilderness areas (over
5,000 acres), national memorial parks (over 5,000 acres), and international parks that were in existence as
of August 1977. Appendix A lists the mandatory Federal Class I areas.
Most impaired days - the dirtiest, or haziest, days.
Nitrate - Solid or liquid particulate matter containing ammonium nitrate [NH4NO3] or other
nitrate salts. Atmospheric nitrate aerosols are often formed from the atmospheric oxidation of
oxides of nitrogen (NOX).
Organic carbon - Aerosols composed of organic compounds, which may result from emissions
from incomplete combustion processes, solvent evaporation followed by atmospheric
condensation, or the oxidation of some vegetative emissions.
Particulate matter - Material that is carried by liquid or solid aerosol particles with
aerodynamic diameters less than 10 microns (in the discussions of this report). The term is used
for both the in situ atmospheric suspension and the sample collected by filtration or other means.
Rayleigh scattering - Light scattering by gases in the atmosphere. At an elevation of 1.8
kilometers, the light extinction from Rayleigh scattering is approximately 10 inverse megameters
(Mm'1).
Relative humidity - The partial pressure of water vapor at the existing atmospheric temperature
divided by the saturated vapor pressure of water at that temperature, expressed as a percentage.
Sulfate - Solid or liquid particulate matter composed of sulfuric acid [H2SO4], ammonium
bisulfate PSTH4HSO4], or ammonium sulfate [(NH4)2SO4], or other sulfate salts. Atmospheric
sulfate aerosols are often formed from the atmospheric oxidation of sulfur dioxide.
Total carbon - Sum of the light absorbing carbon and organic carbon.
Visibility impairment - Any humanly perceptible change in visibility (light extinction, visual range,
contrast, coloration) from that which would have existed under natural conditions. This change in
atmospheric transparency results from added particulate matter or trace gases.
1. INTRODUCTION
1.1 What is regional haze?
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Guidance for Estimating Natural Visibility
Conditions Under the Regional Haze Program
Regional haze is visibility impairment caused by the cumulative air pollutant emissions
from numerous sources over a wide geographic area. Visibility impairment is caused by
particles and gases in the atmosphere. Some particles and gases scatter light while others absorb
light. The net effect is called "light extinction." The result of the scattering and absorption
processes is a reduction of the amount of light from a scene that is returned to the observer, and
scattering of other light into the sight path, creating a hazy condition.
The primary cause of regional haze in many parts of the country is light scattering
resulting from fine particles (i.e., particulate matter less than 2.5 microns in diameter, referred to
as PM2 5) in the atmosphere. These fine particles can contain a variety of chemical species
including carbonaceous species (i.e., organics and elemental carbon), as well as ammonium
nitrate, sulfates, and soil. Additionally, coarse particles between 2.5 and 10 microns in diameter
can contribute to light extinction. Each of these components can be naturally occurring or the
result of human activity. The natural levels of these species result in some level of visibility
impairment, in the absence of any human influences, and will vary with season, daily
meteorology, and geography.
1.2 What is meant by the term "natural visibility conditions?"
The term "natural visibility conditions" represents the ultimate goal of the regional haze
program, consistent with the national visibility goal set forth in section 169A of the Clean Air
Act (CAA). The national visibility goal is to remedy existing and prevent future human-caused
impairment of visibility in mandatory Federal Class I areas. Regional haze strategies are to
make reasonable progress towards this goal.
Natural visibility conditions represent the long-term degree of visibility that is estimated
to exist in a given mandatory Federal Class I area in the absence of human-caused impairment.
It is recognized that natural visibility conditions are not constant, but rather they vary with
changing natural processes (e.g., windblown dust, fire, volcanic activity, biogenic emissions).
Specific natural events can lead to high short-term concentrations of particulate matter and its
precursors. However, for the purpose of this guidance and implementation of the regional haze
program, natural visibility conditions represents a long-term average condition analogous to the
5-year average best-and worst-day conditions that are tracked under the regional haze program.
1.3 What is the purpose of the Guidance for Estimating Natural Visibility Conditions
Under the Regional Haze Rule?
The purpose of this document is to provide guidance to the States in implementing the
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Guidance for Estimating Natural Visibility
Conditions Under the Regional Haze Program
regional haze program under the Clean Air Act. The regional haze regulations were published
by EPA in 1999.J They are designed to protect visual air quality in 156 National Parks and
wilderness areas (known as "mandatory Federal Class I areas"), across the country. As part of
the program, States will develop goals and implement strategies for improving visibility in each
mandatory Federal Class I area. Estimates of natural visibility conditions are needed by the
States for the goal development process. This guidance document describes "default"2 and
"refined" approaches for estimating natural conditions. The EPA believes that natural conditions
estimates developed using the default approach will be adequate to satisfy the requirements of
the regional haze rule for the initial State implementation plan (SIP) submittals due no later than
2008.
This document provides guidance to EPA Regional, State, and Tribal air quality
management authorities and the general public, on how EPA intends to exercise its discretion in
implementing Clean Air Act provisions and EPA regulations, concerning the estimation of
natural conditions under the regional haze program. The guidance is designed to implement
national policy on these issues. Sections 169A and 169B of the Clean Air Act (42) U.S.C. § §
7491,7492 and implementing regulations at 40 CFR 51.308 and 51.309 contain legally binding
requirements. This document does not substitute for those provisions or regulations, nor is it a
regulation itself. Thus, it does not impose binding, enforceable requirements on any party, nor
does it assure that EPA may approve all instances of its application, and thus the guidance may
not apply to a particular situation based upon the circumstances. The EPA and State decision
makers retain the discretion to adopt approaches on a case-by-case basis that differ from this
guidance where appropriate. Any decisions by EPA regarding a particular SIP demonstration
will only be made based on the statute and regulations, and will only be made following notice
and opportunity for public review and comment. Therefore, interested parties are free to raise
questions and objections about the appropriateness of the application of this guidance to a
particular situation; EPA will, and States should, consider whether or not the recommendations
in this guidance are appropriate in that situation. This guidance is a living document and may be
;64 Federal Register 35769, July 1, 1999.
In the context of this guidance, the term "default" refers to the basic approach recommended by EPA to
estimate the natural visibility conditions and the values obtained from adopting this approach. States are welcome to
adopt the default values for natural visibility conditions or, with sufficient technical justification, to propose
alternatives to the basic approach or to generate refined estimates. In theabsence of refinement, EPA recommends
that the default values provided in this document be adopted.
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Guidance for Estimating Natural Visibility
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revised periodically without public notice. The EPA welcomes public comments on this
document at any time and will consider those comments in any future revision of this guidance
document.
Readers of this document are cautioned not to regard statements recommending the use
of certain procedures or defaults as either precluding other procedures or information or
providing guarantees that using these procedures or defaults will result in actions that are fully
approvable. As noted above, EPA cannot assure that actions based upon this guidance will be
fully approvable in all instances, and all final actions may only be taken following notice and
opportunity for public comment.
1.4 Does this guidance document apply to Tribal Class I areas as well as mandatory
Federal Class I areas?
Not directly, although the procedures for estimating natural conditions that are described
in this guidance can be used by Tribes if desired. The CAA and the regional haze rule call for
the protection of visibility in 156 "mandatory Federal Class I areas."3 Tribes can establish Class
I areas for the purposes of the prevention of significant deterioration (PSD) program, but the
CAA does not provide for the inclusion of Tribal areas as mandatory Federal Class I areas
subject to section 169A and 169B of the CAA. For this reason, progress goals and natural
conditions estimates do not have to be established for Tribal Class I areas.
However, Tribes may find it advantageous for a number of reasons to participate in
regional planning organizations (RPO) for regional haze and to develop regional haze tribal
implementation plans (TIPs). Participation in an RPO may allow some Tribes to build capacity
and enhance their air quality management capabilities. Under the Tribal Air Rule, Tribal
governments may elect to implement air programs in much the same way as States, including
development of Tribal implementation plans.4 In this way, Tribes can work with other States
and
3 Areas designated as mandatory Class I areas are those National Parks exceeding 6,000 acres, wilderness
areas and national memorial parks exceeding 5,000 areas, and all international parks which were in existence on
August 7, 1977. Visibility has been identified as an important value in 156 of these areas. See 40 CFR part 81,
subpart D. The extent of a Class I area includes subsequent changes in boundaries, such as park expansions. (CAA
section 162(a)). States and tribes may designate additional areas as Class I, but the requirements of the visibility
program under section 169A of the CAA apply only to "mandatory Class I areas," and do not affect these additional
areas. For the purpose of this guidance document, the term "Class I area" will be used interchangeably with
"mandatory Federal Class I area."
4 See 63 Federal Register 7254 (February 12, 1998), and 40 CFR Part 49.
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Guidance for Estimating Natural Visibility
Conditions Under the Regional Haze Program
Tribes on the development and adoption of specific emissions reduction strategies designed to
protect air quality across a broad region including Tribal and State lands.
1.5 What is the statutory and regulatory background for the regional haze program?
In section 169A of the 1977 Amendments of the Clean Air Act, Congress established a
national visibility goal as the "prevention of any future, and the remedying of any existing,
impairment of visibility in mandatory Federal Class I areas which impairment results from
manmade air pollution." States are required to develop implementation plans that make
"reasonable progress" toward this goal.
The EPA issued initial visibility regulations in 1980s that addressed visibility impairment
in a specific mandatory Federal Class I area that is determined to be "reasonably attributable" to
a single source or small group of sources. Regulations to address regional haze were deferred
until improved techniques could be developed in monitoring, modeling, and in understanding the
effects of specific pollutants on visibility impairment. The 1990 Clean Air Act Amendments
included language in Section 169B to focus attention on regional haze issues. That section
called for EPA to establish the Grand Canyon Visibility Transport Commission, and to issue
regional haze rules within 18 months of receipt of a final report from the Commission. The EPA
issued regional haze regulations in 1999.6
As noted in question 1.2 above, estimates of "natural visibility conditions," which are the
national visibility goal of the Clean Air Act, are needed as part of the implementation process for
the regional haze program.
1.6 What visibility metric will be used for estimating natural conditions, setting goals, and
tracking progress?
According to the Regional Haze Rule, baseline visibility conditions, progress goals, and
changes in natural visibility conditions must be expressed in terms of deciview (dv) units. The
deciview is a unit of measurement of haze, implemented in a haze index (HI) that is derived from
calculated light extinction, and that is designed so that uniform changes in haziness correspond
approximately to uniform incremental changes in perception, across the entire range of
conditions, from pristine to highly impaired. The HI is expressed by the following formula:
5 See 45 Federal Register 80084 (December 2, 1980).
6 See 64 Federal Register 35713 (July 1, 1999). See also 40 CFR 51.300-309.
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Guidance for Estimating Natural Visibility
Conditions Under the Regional Haze Program
HI = 10 ln(bex/10)
where
bext represents total light extinction expressed in inverse megameters (i.e., Mm"1 = 10"6 m"1).
1.7 What are the key requirements and milestones for State implementation plans,
pertaining to the estimation of natural visibility conditions under the regional haze rule?
The regional haze rule requires States to develop SIPs that include 1) reasonable progress
goals for improving visibility in each mandatory Federal Class I area, and 2) a set of emission
reduction measures to meet these goals. A State that does not have any Class I areas will not
establish any progress goals in its SIP, but it is required to consult with nearby States having
Class I areas that may be impacted by emissions from the State. A State without any Class I
areas will also need to adopt emission reduction strategies to address its contribution to visibility
impairment problems in Class I areas located in other States.
Specifically, a State is required to set progress goals for each Class I area in the State that:
• provide for an improvement in visibility for the 20% most impaired (i.e., worst
visibility) days over the period of the implementation plan, and
• ensure no degradation in visibility for the 20% least impaired (i.e., best visibility)
days over the same period.
Baseline visibility conditions for the 20% worst and 20% best days are to be determined using
monitoring data collected during calendar years 2000-2004. Baseline conditions for 2000-2004,
progress goals, and tracking changes over time are to be expressed in deciview units via the haze
index.
Most States (and Tribes as appropriate) participating in regional planning organizations
will submit regional haze implementation plans, including estimates of natural conditions and
proposed progress goals, in the 2007-2008 time frame7. In developing any progress goal, the
Note that in the May 2002 American Corn Growers decision, the DC circuit court of appeals raised
concerns with some of the deadlines for regional haze SIPs in the 1999 regional haze rule. While these issues are
not fully resolved, EPA intends to seek solutions that will ensure that the schedule for regional haze implementation
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Guidance for Estimating Natural Visibility
Conditions Under the Regional Haze Program
Baseline 29
Conditions
Haze Index
(Deciview)
Estimated
Natural 11--
Conditions
I
Required Analysis for
1st Implementation
Period = 4.2 detiviews
2000-4 2018
2064
Year1
Figure 1-1
Example of method for determining mandatory Federal Class I
area rate of progress to be analyzed in SIP development process.
(a HI values for 2004 are based on 2000-2004 data, etc.)
State will need to analyze and consider in its set of options the rate of improvement between
2004 (when 2000-2004 baseline conditions are set) and 2018 that, if maintained in subsequent
implementation periods, would result in achieving estimated natural conditions in 2064. In the
example in Figure 1-1, baseline conditions for the 20% worst days exceed estimated natural
conditions by 18 deciviews. The rate the State must analyze and consider for the 2018 progress
goal is equal to 18 divided by 60 years = 0.3 deciviews per year x 14 years (2004 to 2018) = 4.2
deciviews. The State must demonstrate in the SIP whether it finds that this rate is reasonable or
not, taking into consideration the relevant statutory factors. If it finds that this first rate is not
reasonable, the State shall include a demonstration supporting its finding that an alternate rate is
reasonable.
In order to determine the 2004-2018 progress rate for this analysis, the State should calculate
baseline conditions in accordance with EPA guidance on tracking progress and use this guidance
document for estimating natural conditions.
plans is fully harmonized with the schedule for implementation plans addressing PM2 5 nonattainment.
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1.8 What other factors should be considered in developing progress goals?
Other important issues to be considered in developing mandatory Federal Class I area
progress goals include the reasonable progress factors in the CAA, consultation with Tribes and
other States, and emission reductions due to other Clean Air Act programs. The reasonable
progress factors8 to consider in developing any progress goal are:
the costs of compliance;
• the time necessary for compliance;
• the energy and non-air quality environmental impacts of compliance; and
• the remaining useful life of any existing source subject to such requirements.
The EPA plans to develop additional guidance on how to address these factors in the goal setting
process.
Because visibility impairment results from human activities and their emissions
transported over long distances - hundreds of miles in many cases - addressing impairment can
be effective only through efforts among multiple States. For this reason, States are required to
consult with other States (and Tribes, as appropriate) in developing mandatory Federal Class I
area progress goals and long-term strategies to meet these goals. If a State is reasonably
anticipated to cause or contribute to impairment in a mandatory Federal Class I area in another
State, it is required to consult with that State on the development of that State's progress goals,
and it must include strategies in its SIP that address its contribution to the haze in that State's
mandatory Federal Class I area. Emissions reductions from other States may likewise be taken
into account in setting mandatory Federal Class I area goals. The EPA supports the regional
planning organization process currently under way as the most effective means to address the
requirements of the regional haze program, and it is expected that much of the consultation,
apportionment demonstrations, and technical documentation needed for SIPs will be facilitated
and developed by the regional planning organizations.
Progress goals should also take into account any emission reduction strategies in place or
on the way in order to meet other Clean Air Act requirements. For example, emission reduction
strategies implemented to attain the PM2 5 and ozone NAAQS, and national mobile source
measures such as the Tier II or heavy duty diesel regulations, should be taken into account in
8 See CAA section 169A(g).
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Guidance for Estimating Natural Visibility
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developing mandatory Federal Class I area progress goals for regional haze. Thus, EPA does not
expect any progress goals for regional haze to be less ambitious than the level of visibility
improvement expected from other programs.9
1.9 What progress reviews and future SIP revisions are required under the regional haze
rule?
After the initial SIPs are approved, States will conduct formal progress reviews (in the
form of a SIP revision) every 5 years from the date of SIP submittal (e.g., in 2013 if the initial
SIP is submitted in 2008). Progress will be reviewed in terms of changes in visibility based on
monitoring data, and in terms of the implementation of emission reduction measures contained in
the plan. If progress is not consistent with the visibility and emission reduction goals established
in the original SIP, the State must evaluate the reason for lack of progress and take any
appropriate further action. If the lack of progress is primarily due to emissions from within the
State, then the State must revise its implementation plan within 1 year to include additional
measures to make progress. If the lack of progress is primarily due to emissions from other
States, then the State must reinitiate the regional planning process to address this problem in the
next major SIP revision (e.g., in 2018). If the State finds that international emissions sources are
responsible for a substantial increase in emissions in any Class I area or causing a deficiency in
visibility progress, the State must submit a technical demonstration to EPA in support of its
finding. Similarly, the State should submit a technical demonstration if the State finds that
unusual events (e.g., large wildfires), have affected visibility progress during the 5-year period.10
Given that progress is determined based upon long-term averaging, the EPA believes that it is
unlikely that such events will have a significant effect in most cases. See Section 1.14 for
additional information about consideration of natural emissions from fire.
States will be required to conduct a comprehensive SIP revision in 2018 and every 10
years thereafter. This process will involve re-evaluating rates of progress for each mandatory
Federal Class I area within the State as noted above and establishing new visibility improvement
goals for these areas. The revised SIP should also include any revised emission reduction
measures needed to meet the new mandatory Federal Class I area progress goals.
1.10 Should estimates of natural visibility conditions reflect contemporary conditions and
9 See regional haze rule, 40 CFR Section 51.308(d) (1) (vi).
;°64 Federal Register 35747 (Thursday, July 1, 1999).
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land use patterns, or historic conditions?
For the purposes of this guidance, estimates of natural visibility conditions should reflect
contemporary conditions and land use patterns. That is, estimates should attempt to calculate the
degree of visibility impairment that exists today, given current vegetative landscapes, when
human emissions contributions are removed. We believe that this is a more practical approach
than attempting to speculate about what visibility conditions would have existed under the
vegetative landscapes that existed 3 or 4 centuries ago, i.e., prior to the arrival of European
settlers.
1.11 What estimates of natural conditions are referenced in the regional haze rule and
preamble?
Section 308(d)(2)(iii) of the regional haze rule states that "[natural visibility conditions
must be calculated by estimating the degree of visibility impairment existing under natural
conditions for the most impaired and least impaired days, based on available monitoring
information and appropriate data analysis techniques.]" In the preamble to the regional haze
rule, EPA states that "it will be appropriate to derive regional estimates of natural visibility
conditions by using estimates of natural levels of visibility-impairing pollutants in conjunction
with the IMPROVE methodology for calculating light extinction from measurements of the five
main components of fine particle mass (sulfate, nitrate, organic carbon, elemental carbon, and
crustal material)." As described elsewhere in this document, in addition to the five main
components of fine particle mass, terms for coarse particle mass and Rayleigh scattering are also
included in the calculation of light extinction.
The 1991 peer-reviewed report of the National Acid Precipitation Assessment Program
(NAPAP) provides annual average estimates of natural concentrations for these six main
components of PM for the eastern and western regions of the country.11 By applying
assumptions for average extinction efficiencies for each PM component and for the effect of
humidity, the NAPAP report also included estimates of natural visibility conditions on an annual
average basis. Those estimates are equivalent to about 9.6 deciviews in the eastern region and
5.3 deciviews in the western region of the United States.
In the regional haze preamble, EPA used the NAPAP estimates for natural concentrations
of PM mass components, but used assumptions for average extinction efficiencies and annual
;; National Acid Precipitation Assessment Program, 1991. Acid Deposition: State of Science and
Technology. Report 24. Visibility: Existing and Historical Conditions - Causes and Effects. Table 24-6,
Washington, DC.
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average humidity, based on updated methodologies developed under the IMPROVE program.
Using this approach, EPA found that an appropriate estimate for natural conditions for the 20%
worst days would be approximately 11-12 deciviews in the east and 8 deciviews in the west.
The preamble further stated that "with each subsequent SIP revision, the estimates of
natural conditions for each mandatory Federal Class I area may be reviewed and revised as
appropriate as the technical basis for estimates of natural conditions improve." Possible
approaches for refining natural conditions estimates are discussed later in this document.
1.12 How are the natural visibility conditions at a mandatory Federal Class I area
determined?
The general approach to estimating natural visibility conditions is based on the
IMPROVE methodology for calculating visibility extinction. Using estimates of the natural
concentrations of the primary components of particulate matter, along with estimates of the
extinction efficiencies of these species, and site-specific factors to account for the effects of
relative humidity on light scattering by particles, values for the annual average light extinction at
each mandatory Federal Class I area are calculated. Figure 1-2 summarizes the approach to
estimating natural visibility conditions.
1.13 What approaches for estimating natural conditions are discussed in this guidance
document?
Chapter 2 of this guidance document describes the default approach for estimating
natural visibility conditions for each mandatory Federal Class I area. This approach (see Figure
1-2) relies on the NAPAP estimates for PM mass components and the IMPROVE methodology
for calculating light extinction. Important enhancements incorporated in this approach include
the use of 10-year average relative humidity data from more than 300 weather stations, for
development of appropriate relative humidity adjustment factors (f(RH)), and statistical
techniques for estimating values for the 20% most impaired and 20% least impaired days. The
EPA believes that this approach provides an adequate estimate of natural conditions for the
purpose of developing initial visibility improvement goals and expects to be able to propose to
approve goals in SIP submissions relying on this approach.
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Estimates of Natural
Concentrations
of the Primary
Components of PMj 5
Site-Specific
f(RH) Factors
Calculated bex[
(IMPROVE
Methodology)
Species Specific
Extinction
Efficiencies
Decrview
Values
Figure 1-2 Types of Data Used in Approach for Estimating
Natural Visibility Conditions
Chapter 3 of this guidance describes some alternative approaches by which States may refine
their natural conditions estimates based on additional data and analyses. For example, one
possible refined approach would involve updating the estimates of natural PM mass
concentrations for each PM component, based on recent peer-reviewed literature, rather than
using the NAPAP default values. These methods do not represent an exhaustive list and States
are free to develop alternative approaches that will provide natural visibility conditions estimates
that are technically and scientifically supportable. Any refined approach should be based on
accurate, complete, and unbiased information and should be developed using a high degree of
scientific rigor.
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1.14 How are natural emissions from fire taken into account in estimates of natural PM
and visibility levels?
Because some of the fires producing particulate emissions are naturally occurring, and
would occur in the absence of human activities, the estimate of natural visibility conditions must
take fire into account.
Appendix A of the NAPAP report discusses the approach used to estimate natural mass
levels for each PM component. The estimates are based on compilations of natural versus
man-made emission levels, ambient measurements in remote areas, and regression studies using
man-made and/or natural tracers. Uncertainties are recognized in the estimates of each PM
component. The report recognizes that estimated natural levels of both organic carbon and
elemental carbon include contributions from fire emissions. The NAPAP report includes organic
carbon as the most significant natural PM component by mass in both the eastern and western
regions. Because most of the studies cited in the NAPAP Appendix were conducted in relatively
remote areas, it is reasonable to assume that the contribution of fire to PM mass in the NAPAP
estimates represents the natural regional contribution by fire. The NAPAP estimates included
contributions from smoke but no distinction was made at the time between natural and man-
made fire. Nonetheless, these are the best estimates available in the literature for current
contributions from natural sources. Since the estimate of natural visibility conditions is a long-
term (5-year) average, and because we expect to be able to further refine estimates over time
based on improved information and methods, a regional contribution by fire emissions to overall
natural visibility conditions should be adequate for the purpose of developing initial progress
goals.
Data should be available for EPA and States to develop improved estimates of the
contribution of fire emissions to natural visibility conditions in mandatory Federal Class I areas
over time. Information from a number of additional activities and technical tools should be
available over the coming years, including:
implementation of a coordinated fire data system or fire tracking system;
the collection of multiple years of speciated PM data in mandatory Federal Class I
areas, and the assessment of potential contributions by natural fire events using
data from the fire tracking system;
• development of chemical analysis techniques to identify carbon attributed to fire
versus other sources;
development of improved emissions factors and tracking of fire activity levels;
and
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improved regional scale fire modeling, or remote sensing tools to retrospectively
determine whether smoke from a fire impacted a Class I airshed.
1.15 How does the need to consider the fire component for natural visibility conditions
interface with EPA's general policies regarding fire emissions?
The purpose of this document is to address the identification of methodologies for States
to use in estimating natural visibility conditions, including the contribution from fire. This
document is not intended to identify or dictate potential emission sources and control
requirements.
The EPA acknowledges the need to allow the use of fire as an efficient and economical
land management tool. The use of fire has proven benefits in maintaining the health of fire-
tolerant and fire-dependent plant and animal ecosystems. In some cases, fire may be the only
viable alternative to maintaining species diversity, enhancing productivity, or eliminating the
threat of disease or catastrophic wildfires. The EPA, in partnership with the U.S. Department of
Agriculture (USD A), and the Department of the Interior (DOI), will work with Federal and
private land managers to develop alternatives to fire where applicable but will allow fire as a
viable option in the maintenance of forest land and agricultural (cropland, rangeland,
pastureland) ecosystems. The EPA has participated in the review of the USDA/DOI Wildland
Fire Management Policies (1995 and 2001) and in the development of the 10-Year
Comprehensive Strategy which establishes fire management priorities. The EPA is also actively
involved with USDA and their Agricultural Air Quality Task force in addressing fire as a
management tool for crop production and rangeland management. The EPA expects to amend
the 1998 Interim Air Quality Policy on Wildland and Prescribed Fires to incorporate the final
policy on burning for agricultural crop production and rangeland management. The EPA's
overall policy approach encourages the use of smoke management plans to minimize the impacts
of burning activities on air quality and visibility impairment and provide some flexibility to areas
with certified smoke management programs if it is determined that emissions from these fires
contribute significantly to the National Ambient Air Quality Standards (NAAQS) violations.
States/tribes are aware of their responsibility to meet air quality standards and develop
plans on how they will meet the standards. It is EPA's view that smoke management plans are
best negotiated and implemented at the local level, taking into account regional impacts, and that
sources of emissions from burning are treated in an equitable manner. Recognizing the State's
responsibility to meet air quality standards, EPA encourages flexibility for local decisions on
smoke management by States, locals, or tribal authorities. To address the NAAQS, reduce
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human health risk or exposure, or improve visibility in Class I areas, EPA encourages State and
local air regulatory authorities to include their respective State/local agriculture, forestry, and
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park management agencies in stakeholder discussions and decisions, to ensure equitable and
appropriate viable options for maintaining cropland, rangeland, pastureland, and forest land
ecosystems while meeting air quality goals and standards.
The EPA understands the benefits of a tracking system to keep accurate accounting of
fire emissions for emissions inventory, modeling, and attainment demonstrations and for the
purposes of making sound decisions regarding burn and no burn days. The EPA is currently
working with USDA and USDOI to develop a shared data system that would allow access to
information useful to Federal, State, and local agencies. Some States or regional organizations
have already started to develop their own tracking system for the area. The EPA is not endorsing
any particular tracking system and will work with the States and regional planning organizations
to make sure their tracking systems will interface with the Federal Tracking System to be
developed.
In some cases, regional organizations have found it useful to classify fire emissions into
two categories, natural and man-made, for the purposes of estimating natural visibility
conditions. While EPA is not expressing an opinion on the importance of classifying fires, it
supports those organizations who wish to do so for the purposes of estimating visibility
conditions. However, the EPA does not require the distinction between natural and man-made
fires. The EPA believes that it is important to recognize that any such classification of fire
should not be construed to suggest any classification of emission sources for purposes of
identifying those that are subject to control requirements. The criteria used to classify fires may
or may not be the same criteria used to determine culpable sources and potential control
requirements. Identifying culpable sources and potential control requirements to meet SIP
requirements is beyond the scope and purpose of this document.
1.16 Can a State delay submittal of its control strategy SIP and associated mandatory
Federal Class I area progress goals until it has developed a "refined" estimate of natural
conditions?
No, States cannot use the development of a refined estimate of natural visibility
conditions as a reason for delaying the submittal of regional haze control strategy SIPs required
by statute and regulation. The EPA believes that the default approach to estimating natural
visibility conditions presented in this document is adequate for the development of progress
goals for the first implementation period under the regional haze rule. In addition, the timeline
for implementing the regional haze program already includes a significant amount of lead time
for developing these SIPs, and EPA does not believe that SIP due dates may be extended beyond
the existing regulatory requirements. The EPA expects that States will need to begin assessing
progress goals and emission reduction strategies beginning in the 2004-2005 time frame, in order
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to leave adequate time for air quality modeling, analysis of the statutory factors, consultation
with other States or Tribes, development of regional recommendations, and adoption of
individual State regulations by 2007-8. Because the process of planning and implementing
strategies and evaluating progress is an iterative one, there will be future opportunities to refine
progress goals based on new information about natural visibility conditions, rates of growth and
development, and the effectiveness of controls.
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2. DEFAULT APPROACH TO ESTIMATING NATURAL VISIBILITY CONDITIONS
This section of the guidance document presents the default approach to be used in
estimating the natural visibility conditions for both the 20% most and 20% least impaired days.
2.1 What are the default estimates of the natural concentrations for the PM25 components?
The estimates of the annual averages for the natural levels of fine particle constituents
and of coarse particles are drawn from the 1990 report of NAPAP.12 That report draws published
data from a variety of sources and presents estimates for the natural levels of sulfates, organics,
light absorbing carbon (also referred to as elemental carbon), ammonium nitrate, soil dust, and
coarse particles for the eastern and western regions of the United States. The estimates presented
in that report include significant uncertainties which indicate that the actual natural levels for
these species are likely to fall within a range around the values reported. However, with minor
adjustments, these estimates provide the starting point for calculating natural visibility
conditions in the mandatory Federal Class I areas.
The approach to estimating natural conditions presented in the NAPAP report defines
two separate regions of the United States: (1) the East, which consists of all the States east of the
Mississippi River, and up to one tier of States west of the Mississippi; and (2) the West,
including the desert/mountain regions of the Mountain and Pacific time zones. Geographically,
these two subregions show strong differences in haze sources, vegetation, relative humidity, and
regional haze levels. Within these two subregions, spatial variations in the natural aerosol levels
would be expected. As a result, States near the boundary between East and West should choose
which set of NAPAP estimates are most appropriate and adopt those values.
Table 2-1 presents the default estimated natural concentrations of the particulate species
for the East and the West along with estimates of the dry extinction efficiencies for each species.
These concentration estimates are used with the respective estimates of the dry extinction
efficiencies to establish the light extinction attributed to natural sources in the East and West. As
Table 2-1 shows, the natural concentration estimates differ between the East and West only in
the concentrations of sulfate and organic species.
;2Trijonis, J.C., NAPAP State of Science & Technology, Vol. Ill, 1990.
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Table 2-1 Average Natural Levels of Aerosol Components"
Ammonium sulfate b
Ammonium nitrate
Organic carbon mass c
Elemental carbon
Soil
Coarse Mass
a: After Trijonis, see footnote
b: Values adjusted to represen
Average Natural
West (ng/m3)
0.12
0.10
0.47
0.02
0.50
3.0
Concentration
East (ug/m3)
0.23
0.10
1.40
0.02
0.50
3.0
12
t chemical species in current IMPROVE li|
Error
Factor
2
2
2
2-3
1/2-2
1/2-2
*ht extinction algori
Dry
Extinction
Efficiency
(m2/g)
3
3
4
10
1
0.6
ithm; Trijonis
estimates were 0.1 |J.g/m3 and 0.2 |J.g/m3 of ammonium bisulfate.
c: Values adjusted to represent chemical species in current IMPROVE light extinction algorithm; Trijonis
estimates were 0.5 |ag/m3 and 1.5 |ag/m3 of organic compounds.
2.2 What should be done if the default estimate for any naturally contributed species
exceeds the corresponding measured concentrations?
Contributions by natural sources to haze are defined as "those not from man-made
sources," accordingly, neither natural nor man-made contributions to haze can exceed the total
haze levels over any period of time. The default natural concentration estimates are for long-
term average conditions, and so may be larger than the measured current concentrations for short
periods, but should not exceed the average concentration over several annual cycles. If the
average measured level of any of the six particle species (for the baseline period, or for any other
5-year period), is smaller than the corresponding default natural values, then the default values
should be replaced by values that are equal to or less than the measured values. This would
constitute a refinement of the default as discussed in Section 3.
2.3 How are the long-term relative humidity data used to determine f(RH) values?
The U.S. EPA recently sponsored a project to examine measured hourly relative humidity
data over a 10-year period (1988-1997) within the United States, to derive month-specific
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climatological mean humidity correction factors for each mandatory Federal Class I area.13
These relative humidity (RH) factors were calculated from available hourly relative humidity
data from 292 National Weather Service (NWS) stations across the 50 States and the District of
Columbia, as well as from 29 IMPROVE and IMPROVE protocol monitoring sites, 48 Clean Air
Status and Trends Network (CASTNet) sites, and 13 additional sites administered by the
National Park Service.
The hourly RH measurements from each site were converted to hourly f(RH) values
using a non-linear weighting factor curve, based on a modified ammonium sulfate growth curve
(see Appendix A), applied to the 10 years of surface relative humidity data.
The annual average f(RH) values for all mandatory Federal Class I areas are tabulated in
Appendix A of this document. Those values are used in the default approach to establishing
natural visibility conditions. The 12 monthly averagedf(RH) values for each of these Class I
areas are also tabulated in Appendix A. In most regions there is a seasonal cycle of relative
humidity, which is evident in the appropriate monthly f(RH) values. The monthly f(RH) values
may be used in refined estimates of the natural visibility conditions (Chapter 3). Note that Table
A-2 and supplementary Table A-3 only includes f(RH) values for the designated mandatory
Federal Class I areas. However, the software program needed to calculate/(??//,) values for other
sites is available for use by States, Tribes, and other agencies or interested parties, upon request
to EPA.
13 U.S. EPA, Interpolating Relative Humidity Weighting Factors to Calculate Visibility Impairment and
the Effects of IMPROVE Monitor Outliers, prepared by Science Applications International Corporation, Raleigh,
NC, EPA Contract No. 68-D-98-113, August 30, 2001.
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2.4 How is the default natural light extinction at a mandatory Federal Class I area
calculated?
The calculation of natural light extinction is based on the IMPROVE methodology.
Using the values in Table 2-1, the natural light extinction can be calculated from Equation 1 :
bext = ($)f(RH)[SULFATE} +
(3)f(RH)[NITRATE]
+(4)[<9MC]
+(W)[LAC] (1)
+(0.6)[CM]
+10
where bext is the calculated total light extinction in inverse megameters. (Note: A value of 10
Mm"1 is used for all mandatory Federal Class I areas as an estimate of the light extinction caused
by the light scattering from gas molecules, i.e., Rayleigh scattering). Relative humidity
correction factor s,f(RH), are included for the sulfate and nitrate species as these are hygroscopic
(i.e., absorb water) and their extinction efficiencies change with relative humidity. Annual
average site-specific/(7?//) values for 154 of the 156 mandatory Federal Class I areas (Appendix
A) have been determined from historical data and are used in the default approach to establish
site-specific natural visibility conditions.
Example calculations with Equation 1 will illustrate the use of the default approach.
Looking at two examples in the East, and referring to Table 2-1 for default concentrations and
Appendix A for annual f(RH) values, we see that the natural total light extinction for the Acadia
National Park (Maine) is:
bext = 3(3.4)[0.23] + 3(3.4)[0.1] + 4[1.4] + 10[0.02] + 1[0.5] + 0.6[3.0] + 10
= 21.5 Mm'1
Similarly, for the Everglades National Park (Florida) bext is:
bext = 3(2.7)[0.23]+ 3(2.7)[0.1] + 4[1.4]+ 10[0.02]+ 1[0.5] + 0.6[3.0] + 10
= 20.8MW"1
In the West, we see that Bandelier National Monument (New Mexico) has a default natural light
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extinction of:
bext = 3(1.9)[0.12] + 3(1.9)[0.1] + 4[0.47] + 10[0.02] + 1[0.5] + 0.6[3.0] + 10
= 15.6M/T1
and Yellowstone National Park (Wyoming) has a default bext of:
bext = 3(2.1)[0.12] + 3(2.1)[0.1] + 4[0.47] + 10[0.02] + 1[0.5] + 0.6[3.0] + 10
= 15.8M//T1
The default natural light extinction values have been calculated by this approach for 154 of the
156 mandatory Federal Class I areas and are listed in Appendix B.
2.5 How are the default bext values used to estimate natural visibility in deciview units?
The default light extinction values are used to calculate estimates for the annual average
HI values (in dv units) at each mandatory Federal Class I area. These default HI values are
determined from Equation 2:
=10111(^/10) (2)
where bext is the default total light extinction in Mm"1 as calculated by Equation 1. From the
examples above, the default annual average HI value for Acadia National Park is:
//7=101n(2L5/10)
= 7.7 dv.
For the Everglades National Park, the default HI value is:
//7=101n(20.8/10)
= 7.3 dv.
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The default HI value for Bandelier National Monument is:
///=101n(15.6/10)
= 4.4 dv.
and for Yellowstone National Park the default HI is:
///=101n(15.8/10)
= 4.6 dv.
The calculated annual average HI values for each mandatory Federal Class I area are presented
in Appendix B along with the default total light extinction (6
2.6 How are the 20% best visibility days and the 20% worst visibility days determined in
the default approach?
The calculated HI value represents an estimate of the annual average of daily natural
visibility in dv units. If daily HI values for the natural background visibility in dv units were
available, those values could be arranged in order, and the averages of the best 20% and the
worst 20% of the values could be calculated to establish the regional haze rule goals for each
mandatory Federal Class I area. However, since daily natural visibility ///values are not
available, the default approach provides only an estimate of the annual average natural
background visibility, and the averages for the best and worst 20% must be estimated.
Ames and Malm14 have shown that the frequency distributions of daily calculated HI
values for sites in the East and in the West, can each be well represented by normal distributions.
Consequently, the average HI values for the 20% best visibility days and the 20% worst
visibility days can be estimated from 10th and 90th percentile ///values, respectively. That is,
Rodger Ames and William Malm, Recommendations for Natural Condition Deciview Variability: An
Examination of IMPROVE Data Frequency Distributions, Proceedings of "Regional Haze and Global Radiation
Balance - Aerosol Measurements and Models: Closure Reconciliation and Evaluation," October 2-5, 2002, Bend,
Oregon.
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since the frequency distributions appear to behave normally, the 10th and 90th percentile HI
values (pW and/>90, respectively) for a mandatory Federal Class I area can be estimated from
the following equations:
plO=~HI -l.2Ssd (3)
and,
(4)
where sd represents the standard deviation (in dv units) of the daily ///values for that area, and
HI is the annual average of the ///values. Estimates of sd for current visibility conditions for
eastern and western sites were derived from a database of current visibility conditions. At each
site, daily HI values were calculated from the calculated light extinction values, and the mean
and standard deviation of the daily HI values were determined. Comparison of sites within the
same region showed that, in the East, the current visibility conditions have on average an HI
value of approximately 1 8 dv, with an average sd of approximately 5 dv. In the West, the
current visibility conditions showed an average HI of approximately 8 dv and an average sd of
approximately 2.4 dv. More important in the present context, by inspection of the relationships
between sdand HI, Ames and Malm14 inferred best estimates of the lvalues for natural
visibility in both the West and East. In the West this best estimate of the natural visibility sdis 2
dv, whereas in the East the best estimate of the natural visibility sd is 3 dv.
These estimates of the standard deviation of natural contributions to visibility impairment
can be used in Equations 3 and 4 above, along with the default natural ///values, to estimate the
averages of the 20% best and 20% worst natural visibility contributions.
For example, the calculated 10th and 90th percentile natural ///values for Acadia National Park
are:
plO =7.7 -1.28(3) =3.8
p90 = 7.7 + 1.28(3) = 1 1.5
Appendix B provides the default 10th and 90th percentile natural visibility ///values in dv
units for each of the 156 mandatory Federal Class I areas. Figure 2-1 is a map of the 10th
percentile default HI at mandatory Federal Class I areas across the United States, indicating a
range from approximately 2 dv in the West to 4 dv in the East. Figure 2-2 is a map of the 90th
percentile ///, which ranges from approximately 7 dv in the west to 1 1 dv in the East. Note that
different color scales apply to the East and West portions of Figures 2-1 and 2-2, as indicated in
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the figures. Higher natural ///values in the northwest than the southwest United States are due
to higher RH in the northwest. Higher natural condition organic carbon mass concentrations in
the East are primarily responsible for higher default 10th and 90th percentile natural ///values in
the East relative to the western United States. As noted in Section 2.1, States near the boundary
between East and West have the option of choosing which set of default natural background
conditions to use.
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Default Natural Conditions 10th percentile dv
Figure 2-1 Estimates of the Default 10% Natural Haze Index Values (in dv)
(Note different color scales for the two parts of the figure)
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Default Natural Conditions 90th percentile dv
Figure 2-2 Estimates of the Default 90% Natural Haze Index Values (in dv)
(Note different color scales for the two parts of the figure)
3. REFINED ESTIMATION APPROACHES REGIONAL & SITE-SPECIFIC APPLICATION
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3.1 Why might States want to use a refined approach to estimate natural visibility
conditions?
There are a variety of circumstances under which States might wish to adopt a refined
approach to estimating natural visibility conditions. For example, if the default estimates of the
natural background conditions are close to the current visibility conditions, small uncertainties
can have significant impacts on States' ability to meet SIP goals. In some regions, natural
sources are known to exhibit predictable seasonal influences on visibility. Therefore, States
might wish to use refined estimates of natural visibility conditions to account for these
influences. Also, States which receive significant visibility impacts from biomass smoke might
wish to distinguish more explicitly between man-made and natural sources. These examples are
non-exhaustive, and there may be many other circumstances under which States find it desirable
to develop more refined estimates. In all such cases, they should be prepared to support
alternative approaches with sufficient information so that EPA and the reviewing public can
verify their accuracy and validity.
3.2 What are some of the approaches that could be used by States to refine the default
natural visibility estimates?
A refined approach is essentially one that uses species concentration estimates that differ
from the NAPAP default values given in Table 2-1. Several possible refined approaches which
can be adopted are described in this document, and States may identify others that are more
appropriate for their own situations.
One possible refined approach is to revise the NAPAP default estimates of the natural
concentrations of one or more of the composite components, and repeat the calculations with the
refined concentrations. This approach might be adopted where there is an offset between the
regional natural concentrations and the NAPAP default estimates. In this approach, the visibility
calculations (i.e., Equations 1-4) would be carried out using refined annual average
concentration estimates and the default annual average f(RH) values. Note that any refined
natural concentration estimates must retain the distinction between natural and anthropogenic
components. For example, the natural concentration estimate for a species can never exceed the
actual measured concentration of that species over a 5-year period.
In cases where constant values for natural species concentrations may not be appropriate,
a second possible approach could estimate natural visibility using species concentrations that
vary (e.g., seasonally, monthly, or climatologically). This approach might adopt the NAPAP
default estimates for some species, and temporally varying estimates for others. Alternatively,
the NAPAP estimates might be used for some seasons or time periods and other technically
justified estimates or measurements for the remaining time periods. This approach would use the
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refined concentration estimates and if the time-varying species is hygroscopic (i.e., sulfate or
nitrate), it would also use the appropriate monthly average f(RH) values (Appendix A).
Finally, a refined approach might account for infrequent natural events, such as forest
fires or wind-blown dust, as major influences on visibility. Such an approach would require
estimating the frequency and magnitude of the natural contribution to particle concentrations
during the events.
3.3 Which refined approach is most appropriate for States to use?
To determine which approach is most appropriate, States should first identify whether
any of the particle species concentrations are thought to deviate significantly from the NAPAP
default values. Once identified, States should classify the deviations as either a constant offset
(e.g., NAPAP sulfate values are too low near the sea coast), a systematic temporal variation (e.g.,
natural organics are seasonally higher in the summer), or an infrequent natural variation (e.g.,
dust produced by a natural sand dune area during wind events). The refinement of particle
species concentrations could follow a range of different approaches, from using different annual
average species concentrations, to using seasonal or monthly concentrations, to using different
natural concentrations for individual sample events. Such refined approaches may require
alternative methods to predict the 10th and 90th percentile natural condition ///values. The EPA
encourages flexibility in the approaches used so that default and refined annual average,
seasonal, monthly, and event-specific species concentrations may be intermingled to provide the
best estimates of natural visibility for each of the mandatory Federal Class I areas.
3.4 What should States do if they want to use a refined approach, rather than the default
approach to estimate natural visibility conditions?
States wishing to employ a refined approach should supply demonstrations that the
refined approach is technically sound and provides regionally representative estimates of natural
visibility conditions. The proposed refined approach must be based upon particle species
classification into natural and man-made components (i.e., in any given time period, the natural
particle species concentration cannot exceed the measured concentration), and should be
submitted to EPA for approval prior to implementation.
States wishing to adopt a refined approach based on a constant offset of the natural
concentrations of the particle species should provide technical justification for revising the
NAPAP default concentrations. Using the refined concentrations, the natural visibility condition
should then be calculated based on an approach that is consistent with the methodology that is
used to track trends, such as the default approach.
A-3
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Guidance for Estimating Natural Visibility
Conditions Under the Regional Haze Program
States wishing to adopt a refined approach based on estimates of annually varying
(seasonally, monthly, climatologically, etc.) natural particle concentrations should also provide
technical justification for the estimates of the natural particle species concentrations. For
example, if seasonal variations in particle species are the basis for the refined approach, then
estimates should be provided of natural concentrations in every season for every pertinent
species. Those particle species components that do not vary significantly should be treated using
a constant estimate of the natural concentrations (e.g., use NAPAP value for each season).
In any case, the appropriate mechanism for putting a refined estimation approach in place
is to incorporate the approach in a new or revised SIP. The justification for the proposed refined
approach will thereby be considered as part of the normal SIP review process.
3.5 How might an infrequent natural impact be quantified?
Infrequent events affecting the visibility at specific mandatory Federal Class I areas could
be addressed by using a constant or temporally varying value for species affected by the event
during all non-event periods, and a different value for those same species for sampling periods
during the event. For example, consider a forest fire, which affects particulate organic and
elemental carbon. The contribution of the fire event to the natural levels of those species during
the fire might be estimated by assuming all of the observed increment above the mean of the
sample periods immediately pre- and post-fire event was the result of the fire. Multiple pre- and
post-event sample periods could be used to strengthen the comparison. Alternatively, an air
quality model might be used to estimate the impact of the smoke plume on particle carbon levels,
or other air quality measurements might be used to estimate the impact of the event.
3.6 Can natural visibility estimates be made on a sample-period-by-sample-period basis?
Yes, such calculations can be done, but refined concentration estimates should be
justified to support such an approach. In that case, the calculation of the current bext would first
be done for each sample day, using Equation 1, the appropriate monthly f(RH) values, and the
daily monitoring data for each species. The resulting daily bext values would then be converted to
an HI value in dv units by Equation 2. Those HI values would then be sorted, and the highest
20% and lowest 20% identified, indicating the days with the most and the least visibility
impairment, respectively. (This procedure is described in detail in a separate guidance document
3-3
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Guidance for Estimating Natural Visibility
Conditions Under the Regional Haze Program
for tracking progress). For each of the days in these two groups, the natural contribution to light
extinction would then be estimated. The average of each of these two groups of natural
contributions would then be calculated.
As noted above, in any given time period the natural concentration of a species estimated
by this calculation cannot exceed the actual measured concentration. Furthermore, if this
approach is taken, natural visibility conditions (i.e., the averages of the 20% worst and 20% best
natural HI values) should be estimated for as many years as possible to ensure that the average
results are more representative of the long-term conditions.
3-1
-------
Appendix A
Annual Average f(RH) and Monthly Average f(RH)
Values at All Mandatory Federal Class I Areas
A-l
-------
Guidance for Estimating Natural Visibility
Conditions Under the Regional Haze Program
Appendix A
Origin of Relative Humidity and f(RH) Values
In terms of visibility reduction caused by fine particles, it is appropriate to treat relative
humidity differently for different objectives. If the objective is the most reliable short-term
estimate of visibility, then the measured or estimated relative humidity for the specific time and
location of the aerosol speciation data is most appropriate. If the objective is to assess the long-
term changes in man-made visibility impairment, it is appropriate to use relative humidity that is
the same for the baseline period and future periods. In other words, it is more appropriate to
eliminate the confounding effects of varying relative humidity, if the purpose is to track the
visibility effects of air pollution emissions over extended time periods.
A number of approaches were considered to prevent variations in the relative humidity
adjustment factor from confounding efforts to track progress related to emission controls. The
simplest approach would use the same typical or overall average adjustment factor for all Class I
areas at all times. However, this would enhance the contributions of hygroscopic particle species
in dry locations and during typically dry seasons above what they truly should be while reducing
their contributions in moist locations and seasons. Such distortions of the contributions to haze
by hygroscopic particle species are unnecessary if a set of Class I area-specific adjustment
factors are used that reflect seasonal changes in relative humidity.
A second approach would be to review relative humidity data over a long period of time
to derive climatological estimates for relative humidity adjustment factors. These climatological
estimates would then be used to estimate visibility extinction coefficients. These estimates are
more likely to reflect "typical" relative humidity at the different mandatory Federal Class I areas
during different times of year and, thus, are more likely to be more appropriate for establishing
trends in visibility at the mandatory Federal Class I areas.
Recently, the U.S. EPA sponsored a project to examine measured hourly relative
humidity data over a 10-year period within the United States, to derive month-specific
climatological mean humidity correction factors for each mandatory Federal Class I area.15 The
results of that work are presented in the table below and the draft report is available at:
http://www.epa.gov/ttn/naaqs/pm/pm25_tech.html
;J U.S. EPA, Interpolating Relative Humidity Weighting Factors to Calculate Visibility Impairment and the
Effects of IMPROVE Monitor Outliers, prepared by Science Applications International Corporation, Raleigh, NC,
EPA Contract No. 68-D-98-113, August 30, 2001.
A-2
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Guidance for Estimating Natural Visibility
Conditions Under the Regional Haze Program
These relative humidity factors have been calculated from available hourly relative humidity
data from 292 National Weather Service stations across the 50 States and District of Columbia as
well as from 29 IMPROVE and IMPROVE protocol monitor sites, 48 CASTNet sites, and 13
additional sites administered by the National Park Service.
The hourly RH measurements from each site were converted iof(RH) values using a non-
linear weighting factor curve, based on a modified ammonium sulfate growth curve. Values
above 95% RH were set equal to thef(RH) corresponding to 95% RH. For days in which at least
16 hours of valid RH data were available, daily averages were determined from these hourly
f(RH) values at each site. Monthly averages were then calculated from the daily f(RH) averages
at each site.
The monthly average f(RH) values were interpolated at 1/4-degree increments using the
inverse distance weighting technique (with a distance interpolation exponent of 1):
where the monthly f(RH)g of the grid cell is calculated fromf(RH)w at the weather station, and the
horizontal distance between the grid cell center and the weather station, xwg, summed over all the
weather stations within a 250-mile radius with valid f(RH) values for that month.
In most regions there is a seasonal cycle of relative humidity which is accounted for by
this process of appropriate f(RH) values for each month of the year from the daily-averaged
values. Thus, the 12 monthly-averaged/fK^) values determined in this way for each Class I area
should be used for all aerosol speciation data or model predictions for that location. However, a
more complicated approach has also been investigated, as described below.
The regional haze regulation requires separate tracking of visibility changes for the worst
20% and best 20% of visibility days. If there is a significant correlation in any month at any site
between daily relative humidity and the sulfate or nitrate concentrations, then use of the
monthly-averaged/(??#) will systematically over- or under-predict the contribution to visibility
impairment of the aerosol species. Fortunately, this concern can be tested at a number of
locations in all regions of the country using the IMPROVE database. If the use of monthly-
averaged values were found to cause large systematic biases in any region of the country, the
Class I areas in those regions would require twof(RH) values for each month. One value would
be the average f(RH) associated with relative humidity conditions that correspond to the worst
20% and the other value associated with relative humidity conditions that correspond to the best
A-3
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Guidance for Estimating Natural Visibility
Conditions Under the Regional Haze Program
20% of the light extinction values. Therefore there is the potential that some Class I area
locations could require up to 24f(RH) values for use in calculating extinction for aerosol data.
The U.S. National Park Service has tested this possibility, by examining data for each of
the 12 months from 20 mandatory Federal Class I areas where relative humidity measurements
are made. In nearly all cases, no statistically significant correlations were found between
measured concentrations of SO42", NO3" and [SO42" + NO3"] vs. daily values of relative humidity
in a large majority of months. Furthermore, deciview calculations were made using day-specific
vs. climatological values for the relative humidity adjustment factor for each of 10 years in 15
mandatory Federal Class I areas. In 14 of the 15 areas, little if any difference was observed in
the year to year calculations for the mean deciview values for the 20% worst and 20% best days,
nor was there any difference in the trends. Some difference in the mean deciview value for the
worst 20% days was observed in one mandatory Federal Class I area. However, the overall trend
in the mean worst and best deciview values for this site was similar using the two types off(RH)
values. These results suggest there is a relatively weak correlation between hygroscopic
components of PM and relative humidity and that the choice of a "climatological" vs. "day-
specific" method for computing/(7?//) has little apparent effect on observed trends in visibility.
Consequently, the simpler climatological approach is used in regional haze calculations.
A-4
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Guidance for Estimating Natural Visibility
Conditions Under the Regional Haze Program
Table A-l Values for f(RH) determined from the growth of ammonium sulfate
RH
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
f(RH)
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
RH
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
f(RH)
1.00
1.00
1.00
1.02
1.04
1.06
1.08
1.10
1.13
1.15
1.18
1.20
1.23
1.26
1.28
1.31
1.34
1.37
1.41
1.44
1.47
1.51
1.54
1.58
1.62
1.66
1.70
1.74
1.79
1.83
1.88
1.93
1.98
RH
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
f(RH)
2.03
2.08
2.14
2.19
2.25
2.31
2.37
2.43
2.50
2.56
2.63
2.70
2.78
2.86
2.94
3.03
3.12
3.22
3.33
3.45
3.58
3.74
3.93
4.16
4.45
4.84
5.37
6.16
7.40
9.59
14.1
26.4
A-5
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Guidance for Estimating Natural Visibility Conditions Under the Regional Haze Rule
Table A-2 Recommended Monthly Site-Specific f(RH)
Based on the Representative
Class 1 Area
Acadia
Agua Tibia
Alpine Lakes
Anaconda - Pintler
Ansel Adams
Arches
Badlands
Bandelier
Bering Sea (a)
Big Bend
Black Canyon of the Gunnison
Bob Marshall
Bosque del Apache
Boundary Waters Canoe Area
Breton
Bridger
Brigantine
Bryce Canyon
Cabinet Mountains
Caney Creek
Canyonlands
Cape Romain
Capitol Reef
Caribou
Carlsbad Caverns
Chassahowitzka
Chiricahua NM
Chiricahua W
Cohutta
Crater Lake
Craters of the Moon
Cucamonga
Denali
Desolation
Diamond Peak
Dolly Sods
Dome Land
Eagle Cap
Eagles Nest
Emigrant
Everglades
Fitz patrick
Flat Tops
Site Name
Acadia
Agua Tibia
Snoqualmie Pass
Sula
Kaiser
Canyonlands
Badlands
Bandelier
Big Bend
Weminuche
Monture
Bosque del Apache
Boundary Waters
Breton
Bridger
Brigantine
Bryce Canyon
Cabinet Mountains
Caney Creek
Canyonlands
Cape Romain
Capitol Reef
Lassen Volcanic
Guadalupe Mountains
Chassahowitzka
Chiricahua
Chiricahua
Cohutta
Crater Lake
Craters of the Moon
San Gabriel
Denali
Bliss
Crater Lake
Dolly Sods
Dome Land
Starkey
White River
Yosemite
Everglades
Bridger
White River
1
100
80
71
110
50
59
33
31
55
73
38
23
20
65
5
49
75
29
50
15
52
90
32
18
39
39
12
86
69
93
102
95
86
8
109
76
56
96
19
65
56
Code
ACAD1
AGTI1
SNPA1
SULA1
KAIS1
CANY1
BADL1
BAND1
BIBE1
WEMI1
MONT1
BOAP1
BOWA1
BRET1
BRID1
BRIG1
BRCA1
CABI1
CACR1
CANY1
ROMA1
CAPI1
LAVO1
GUMO1
CHAS1
CHIR1
CHIR1
COHU1
CRLA1
CRMO1
SAGA1
DENA1
BLIS1
CRLA1
DOSO1
DOME1
STAR1
WHRI1
YOSE1
EVER1
BRID1
WHRI1
Site St
ME
CA
WA
MT
CA
UT
SD
NM
TX
CO
MT
NM
MN
LA
WY
NJ
UT
MT
AR
UT
SC
UT
CA
TX
FL
AZ
AZ
GA
OR
ID
CA
AK
CA
OR
WV
CA
OR
CO
CA
FL
WY
CO
LAT
44.38
33.38
47.38
45.88
37.13
38.38
43.63
35.88
29.38
37.63
47.13
33.88
47.88
29.13
42.88
39.38
37.63
47.88
34.38
38.38
32.88
38.38
40.63
31.88
28.63
32.13
32.13
34.88
42.88
43.38
34.38
63.75
38.88
42.88
39.13
35.63
45.13
39.13
37.63
25.38
42.88
39.13
LONG
-68.37
-116.87
-121.37
-114.12
-119.12
-109.87
-101.87
-106.37
-103.12
-107.87
-113.12
-106.87
-91.62
-89.12
-109.87
-74.37
-112.12
-115.62
-94.12
-109.87
-79.62
-111.37
-121.62
-104.87
-82.62
-109.37
-109.37
-84.62
-122.12
-113.62
-118.12
-148.75
-120.12
-122.12
-79.37
-118.12
-118.62
-106.87
-119.62
-80.62
-109.87
-106.87
Values for Each Mandatory Federal
IMPROVE Site Location
Jan
f(RH)
3.2
2.4
5.3
3.4
3.0
2.6
2.8
2.3
1.8
2.5
3.3
2.2
2.9
3.5
2.5
2.9
2.6
3.7
3.3
2.6
3.2
2.7
3.7
2.4
3.5
2.0
2.0
3.4
4.6
3.1
2.6
2.5
3.2
4.6
3.0
2.6
4.3
2.2
3.0
2.6
2.5
2.2
Feb
f(RH)
2.8
2.3
5.0
3.0
2.7
2.3
2.8
2.1
1.7
2.3
2.9
2.0
2.6
3.3
2.3
2.6
2.4
3.2
3.0
2.3
2.9
2.5
3.1
2.0
3.2
1.9
1.9
3.1
4.0
2.7
2.5
2.3
2.8
4.0
2.7
2.3
3.8
2.2
2.9
2.5
2.3
2.2
Mar
f(RH)
2.8
2.4
3.7
2.6
2.5
1.8
2.8
1.8
1.5
2.0
2.6
1.6
2.6
3.3
2.3
2.7
2.0
2.8
2.7
1.8
2.8
2.0
2.8
1.6
3.1
1.6
1.6
2.9
3.7
2.3
2.5
2.1
2.5
3.7
2.7
2.2
3.2
2.0
2.7
2.5
2.3
2.0
Apr
f(RH)
3.2
2.2
3.6
2.3
2.1
1.6
2.6
1.6
1.4
1.7
2.4
1.4
2.3
3.3
2.1
2.6
1.6
2.5
2.8
1.6
2.7
1.7
2.4
1.4
3.0
1.2
1.2
2.7
3.5
2.0
2.2
1.9
2.0
3.5
2.5
1.9
2.9
2.0
2.2
2.3
2.1
2.0
May
f(RH)
3.2
2.2
4.2
2.3
2.0
1.5
2.8
1.6
1.5
1.7
2.4
1.4
2.5
3.4
2.1
2.9
1.5
2.5
3.2
1.5
2.9
1.6
2.3
1.6
3.0
1.2
1.2
3.2
3.2
2.0
2.2
1.8
1.9
3.2
3.5
1.9
2.7
2.0
2.1
2.3
2.1
2.0
Jun
f(RH)
3.3
2.2
3.1
2.2
1.7
1.2
2.7
1.4
1.5
1.5
2.4
1.3
2.8
3.6
1.8
3.0
1.3
2.4
3.2
1.2
3.3
1.4
2.1
1.5
3.5
1.1
1.1
3.6
2.9
1.8
2.1
2.1
1.6
2.9
3.1
1.8
2.4
1.7
1.7
2.6
1.8
1.7
Jul
f(RH)
3.7
2.2
3.5
1.9
1.7
1.3
2.4
1.7
1.6
1.7
2.1
1.7
3.0
3.8
1.5
3.2
1.3
2.1
3.0
1.3
3.3
1.4
2.0
1.9
3.5
1.7
1.7
3.6
2.6
1.4
2.2
2.5
1.5
2.6
3.2
1.8
2.0
1.8
1.5
2.5
1.5
1.8
Class I Area,
Aug
f(RH)
3.7
2.3
3.4
1.8
1.7
1.5
2.4
2.0
1.8
2.0
2.0
1.9
3.1
3.8
1.5
3.4
1.5
2.1
3.0
1.5
3.6
1.6
2.0
2.2
3.7
2.0
2.0
3.7
2.7
1.4
2.2
2.9
1.5
2.7
3.5
1.8
2.1
2.1
1.5
2.8
1.5
2.1
Sep
f(RH)
3.9
2.3
3.8
2.0
1.8
1.5
2.3
1.9
1.9
1.9
2.3
1.9
3.2
3.6
1.8
3.4
1.5
2.4
3.2
1.5
3.5
1.6
2.1
2.4
3.7
1.7
1.7
3.7
2.9
1.6
2.3
2.8
1.7
2.9
3.5
1.9
2.4
2.1
1.6
2.9
1.8
2.1
Oct
f(RH)
3.5
2.2
4.9
2.5
1.9
1.6
2.3
1.7
1.7
1.7
2.7
1.6
2.7
3.4
2.0
3.2
1.6
2.9
3.2
1.6
3.4
1.7
2.3
1.7
3.5
1.5
1.5
3.5
3.6
2.0
2.2
3.0
1.8
3.6
3.1
1.9
3.3
1.8
1.8
2.7
2.0
1.8
Nov
f(RH)
3.4
2.1
5.5
3.3
2.3
2.0
2.9
2.0
1.7
2.2
3.2
1.8
3.1
3.4
2.5
2.8
2.0
3.6
3.1
2.0
3.1
2.1
3.1
1.9
3.4
1.6
1.6
3.2
4.6
2.7
2.2
2.9
2.4
4.6
2.8
2.0
4.2
2.1
2.3
2.5
2.5
2.1
Dec
f(RH)
3.5
2.2
5.3
3.4
2.7
2.3
2.8
2.3
1.7
2.4
3.3
2.2
3.1
3.5
2.4
2.9
2.4
3.8
3.3
2.3
3.1
2.5
3.5
2.3
3.6
2.1
2.1
3.4
4.7
3.0
2.3
3.0
3.0
4.7
3.1
2.2
4.5
2.1
2.7
2.6
2.4
2.1
A-6
-------
Guidance for Estimating Natural Visibility Conditions Under the Regional Haze Rule
Table
Class 1 Area
Galiuro
Gates of the Mountains
Gearhart Mountain
Gila
Glacier
Glacier Peak
Goat Rocks
Grand Canyon
Grand Teton
Great Gulf
Great Sand Dunes
Great Smoky Mountains
Guadalupe Mountains
Haleakala
Hawaii Volcanoes
Hells Canyon
Hercules - Glade
Hoover
Isle Royale
James River Face
Jarbidge
John Muir
Joshua Tree
Joyce Kilmer - Slickrock
Kaiser
Kalmiopsis
Kings Canyon
La Garita
Lassen Volcanic
Lava Beds
Linville Gorge
Lostwood
Lye Brook
Mammoth Cave
Marble Mountain
Maroon Bells - Snowmass
Mazatzal
Medicine Lake
Mesa Verde
Mingo
Mission Mountains
Mokelumne
Moosehorn
A-2 Recommended Monthly Site-Specific f(RH)
Based on the Representative
Site Name
Chiricahua
Gates of the Mountains
Crater Lake
Gila Cliffs
Glacier
North Cascades
White Pass
Grand Canyon, Hance
Yellowstone
Great Gulf
Great Sand Dunes
Great Smoky Mountains
Guadalupe Mountains
Haleakala
Hawaii Volcanoes
Hells Canyon
Hercules - Glade
Hoover
Isle Royale
James River Face
Jarbidge
Kaiser
Joshua Tree
Great Smoky Mountains
Kaiser
Kalmiopsis
Sequoia
Weminuche
Lassen Volcanic
Lava Beds
Linville Gorge
Lostwood
Lye Brook
Mammoth Cave
Trinity
White River
Ike's Backbone
Medicine Lake
Mesa Verde
Mingo
Monture
Bliss
Moosehorn
39
74
86
42
72
81
79
48
66
4
53
10
32
108
107
77
28
97
25
7
68
110
101
10
110
89
98
55
90
87
13
62
3
9
104
56
46
63
54
26
73
95
2
Code
CHIR1
GAMO1
CRLA1
GICL1
GLAC1
NOCA1
WHPA1
GRCA2
YELL2
GRGU1
GRSA1
GRSM1
GUMO1
HALE1
HAVO1
HECA1
HEGL1
HOOV1
ISLE1
JARI1
JARB1
KAIS1
JOSH1
GRSM1
KAIS1
KALM1
SEQU1
WEMI1
LAVO1
LABE1
LIGO1
LOST1
LYBR1
MACA1
TRIN1
WHRI1
IKBA1
MELA1
MEVE1
MING1
MONT1
BLIS1
MOOS1
Site St
AZ
MT
OR
NM
MT
WA
WA
AZ
WY
NH
CO
TN
TX
HI
HI
OR
MO
CA
Ml
VA
NV
CA
CA
TN
CA
OR
CA
CO
CA
CA
NC
ND
VT
KY
CA
CO
AZ
MT
CO
MO
MT
CA
ME
LAT
32.13
46.88
42.88
33.13
48.63
48.63
46.63
35.88
44.63
44.38
37.63
35.63
31.88
20.75
19.25
44.88
36.63
38.13
47.38
37.63
41.88
37.13
34.13
35.63
37.13
42.63
36.38
37.63
40.63
41.63
35.88
48.63
43.13
37.13
40.88
39.13
34.38
48.38
37.13
36.88
47.13
38.88
45.13
LONG
-109.37
-111.62
-122.12
-108.12
-114.12
-121.12
-121.37
-111.87
-110.37
-71.12
-105.62
-83.87
-104.87
-156.25
-155.25
-116.87
-92.87
-119.12
-88.12
-79.62
-115.37
-119.12
-116.37
-83.87
-119.12
-124.12
-118.87
-107.87
-121.62
-121.62
-81 .87
-102.37
-73.12
-86.12
-122.87
-106.87
-1 1 1 .62
-104.37
-108.37
-90.12
-113.12
-120.12
-67.37
Values for Each Mandatory Federal
IMPROVE Site Location
Jan
f(RH)
2.0
2.8
4.6
2.1
3.9
4.5
4.8
2.5
2.5
2.8
2.4
3.6
2.4
2.7
3.0
3.7
3.2
3.1
3.1
2.9
2.9
3.0
2.4
3.6
3.0
4.5
2.9
2.5
3.7
4.0
3.2
3.0
2.8
3.3
4.0
2.2
2.2
3.0
2.8
3.2
3.3
3.2
3.0
Feb
f(RH)
1.9
2.5
4.0
1.9
3.4
4.1
4.2
2.4
2.3
2.6
2.3
3.0
2.0
2.6
2.9
3.1
2.9
2.7
2.6
2.7
2.6
2.7
2.3
3.0
2.7
3.9
2.6
2.3
3.1
3.4
3.0
2.9
2.6
3.0
3.4
2.2
2.0
2.9
2.6
2.9
2.9
2.8
2.7
Mar
f(RH)
1.6
2.4
3.7
1.6
3.1
3.6
3.8
2.0
2.2
2.6
2.0
3.0
1.6
2.5
2.9
2.4
2.6
2.5
2.7
2.6
2.1
2.5
2.3
3.0
2.5
3.7
2.5
2.0
2.8
3.1
2.9
3.0
2.7
2.9
3.2
2.0
1.8
2.9
2.2
2.7
2.6
2.5
2.7
Apr
f(RH)
1.2
2.3
3.5
1.3
2.9
3.4
3.6
1.6
2.1
2.8
1.9
2.8
1.4
2.5
2.9
2.1
2.6
2.0
2.5
2.4
2.1
2.1
2.0
2.8
2.1
3.5
2.2
1.7
2.4
2.8
2.7
2.3
2.6
3.0
2.9
2.0
1.4
2.2
1.7
2.6
2.4
2.0
2.9
May
f(RH)
1.2
2.3
3.2
1.3
3.0
3.3
3.4
1.4
2.1
2.9
1.9
3.2
1.6
2.4
2.9
2.0
3.0
1.9
2.4
2.9
2.2
2.0
2.0
3.2
2.0
3.3
2.1
1.7
2.3
2.6
3.2
2.2
2.8
4.1
2.8
2.0
1.3
2.2
1.7
2.9
2.4
1.9
2.9
Jun
f(RH)
1.1
2.2
2.9
1.2
3.0
3.0
3.1
1.2
1.9
3.0
1.7
3.6
1.5
2.3
2.9
1.8
3.0
1.6
2.9
3.1
2.0
1.7
1.9
3.6
1.7
3.1
1.8
1.5
2.1
2.4
3.6
2.5
2.9
4.7
2.6
1.7
1.2
2.4
1.3
3.0
2.4
1.6
3.1
Jul
f(RH)
1.7
2.0
2.6
1.9
2.5
2.9
2.9
1.4
1.7
3.3
1.9
3.6
1.9
2.4
3.0
1.5
3.0
1.5
3.2
3.2
1.6
1.7
1.5
3.6
1.7
2.9
1.7
1.7
2.0
2.2
3.6
2.5
3.1
4.6
2.5
1.8
1.4
2.4
1.7
3.1
2.1
1.5
3.5
Class I Area,
Aug
f(RH)
2.0
1.9
2.7
1.9
2.5
3.1
3.0
1.7
1.6
3.5
2.3
3.6
2.2
2.4
3.0
1.4
3.0
1.5
3.4
3.3
1.4
1.7
2.0
3.6
1.7
3.0
1.7
2.0
2.0
2.2
3.9
2.3
3.3
3.5
2.6
2.1
1.7
2.1
2.0
3.1
2.0
1.5
3.6
Sep
f(RH)
1.7
2.1
2.9
1.8
3.0
3.5
3.5
1.7
1.8
3.6
2.2
3.7
2.4
2.3
3.0
1.6
3.2
1.6
3.5
3.4
1.4
1.8
2.0
3.7
1.8
3.1
1.8
1.9
2.1
2.4
3.9
2.2
3.4
3.5
2.7
2.1
1.6
2.2
1.9
3.2
2.3
1.7
3.8
Oct
f(RH)
1.5
2.4
3.6
1.6
3.3
4.2
4.3
1.7
2.1
3.2
1.9
3.4
1.7
2.5
3.0
2.2
2.9
1.8
2.9
3.0
1.6
1.9
2.0
3.4
1.9
3.6
1.9
1.7
2.3
2.8
3.4
2.4
3.2
3.2
2.9
1.8
1.5
2.3
1.8
2.9
2.7
1.8
3.3
Nov
f(RH)
1.6
2.7
4.6
1.8
3.7
4.7
4.9
2.0
2.4
3.0
2.3
3.3
1.9
2.7
3.3
3.4
3.0
2.3
3.3
2.7
2.4
2.3
1.9
3.3
2.3
4.4
2.3
2.2
3.1
3.6
3.1
3.2
2.9
3.1
3.6
2.1
1.8
3.1
2.2
3.0
3.2
2.4
3.2
Dec
f(RH)
2.1
2.7
4.7
2.2
3.8
4.7
5.0
2.3
2.5
2.9
2.4
3.5
2.3
2.6
3.0
3.8
3.2
2.8
3.3
3.0
2.8
2.7
2.1
3.5
2.7
4.4
2.5
2.4
3.5
4.0
3.2
3.2
2.9
3.4
3.9
2.1
2.1
3.1
2.6
3.2
3.3
3.0
3.2
A- 7
-------
Guidance for Estimating Natural Visibility Conditions Under the Regional Haze Rule
Table A-2 Recommended Monthly Site-Specific f(RH)
Based on the Representative
Class 1 Area
Mount Adams
Mount Baldy
Mount Hood
Mount Jefferson
Mount Rainier
Mount Washington
Mount Zirkel
Mountain Lakes
North Absaroka
North Cascades
Okefenokee
Olympic
Otter Creek
Pasayten
Pecos
Petrified Forest
Pine Mountain
Pinnacles
Point Reyes
Presidential Range - Dry River
Rawah
Red Rock Lakes
Redwood
Rocky Mountain
Roosevelt Campobello
Saguaro
Saint Marks
Salt Creek
San Gabriel
San Gorgonio
San Jacinto
San Pedro Parks
San Rafael
Sawtooth
Scapegoat
Selway - Bitterroot
Seney
Sequoia
Shenandoah
Shining Rock
Sierra Ancha
Simeonof
Sipsey
Site Name
White Pass
Mount Baldy
Mount Hood
Three Sisters
Mount Rainier
Three Sisters
Mount Zirkel
Crater Lake
North Absoraka
North Cascades
Okefenokee
Olympic
Dolly Sods
Pasayten
Wheeler Peak
Petrified Forest
Ike's Backbone
Pinnacles
Point Reyes
Great Gulf
Mount Zirkel
Yellowstone
Redwood
Rocky Mountain
Moosehorn
Saguaro
Saint Marks
Salt Creek
San Gabriel
San Gorgonio
San Gorgonio
San Pedro Parks
San Rafael
Sawtooth
Monture
Sula
Seney
Sequoia
Shenandoah
Shining Rock
Sierra Ancha
Simeonof
Sipsey
79
43
85
84
78
84
58
86
67
81
16
83
8
82
35
41
46
92
91
4
58
66
88
57
2
40
17
36
93
99
99
34
94
70
73
71
22
98
6
11
45
105
21
Code
WHPA1
BALD1
MOHO1
THSI1
MORA1
THSI1
MOZI1
CRLA1
NOAB1
NOCA1
OKEF1
OLYM1
DOSO1
PASA1
WHPE1
PEFO1
IKBA1
PINN1
PORE1
GRGU1
MOZI1
YELL2
REDW1
ROMO1
MOOS1
SAGU1
SAMA1
SACR1
SAGA1
SAGO1
SAGO1
SAPE1
RAFA1
SAWT1
MONT1
SULA1
SENE1
SEQU1
SHEN1
SHRO1
SIAN1
SIME1
SIPS1
Site St
WA
AZ
OR
OR
WA
OR
CO
OR
WY
WA
GA
WA
WV
WA
NM
AZ
AZ
CA
CA
NH
CO
WY
CA
CO
ME
AZ
FL
NM
CA
CA
CA
NM
CA
ID
MT
MT
Ml
CA
VA
NC
AZ
AK
AL
LAT
46.63
34.13
45.38
44.38
46.88
44.38
40.63
42.88
44.63
48.63
30.63
48.13
39.13
48.38
36.63
35.13
34.38
36.38
38.13
44.38
40.63
44.63
41.63
40.38
45.13
32.13
30.13
33.38
34.38
34.13
34.13
36.13
34.63
44.13
47.13
45.88
46.38
36.38
38.63
35.38
34.13
55.25
34.38
LONG
-121.37
-109.37
-121.87
-122.12
-122.12
-122.12
-106.62
-122.12
-109.37
-121.12
-82.12
-122.87
-79.37
-119.87
-105.37
-109.87
-111.62
-121.12
-122.87
-71.12
-106.62
-110.37
-124.12
-105.62
-67.37
-110.62
-84.12
-104.37
-118.12
-116.87
-116.87
-106.87
-120.12
-114.87
-113.12
-114.12
-85.87
-118.87
-78.37
-82.87
-110.87
-160.75
-87.37
Values for Each Mandatory Federal
IMPROVE Site Location
Jan
f(RH)
4.8
2.2
4.6
5.3
5.3
5.3
2.2
4.6
2.4
4.5
3.3
4.2
3.0
4.6
2.4
2.4
2.2
3.4
3.6
2.8
2.2
2.5
3.8
1.9
3.0
1.8
3.5
2.2
2.6
2.5
2.5
2.4
3.0
3.3
3.3
3.4
3.3
2.9
2.9
3.3
2.2
4.2
3.3
Feb
f(RH)
4.2
2.1
4.1
4.6
4.7
4.6
2.2
4.0
2.2
4.1
3.0
3.9
2.7
4.1
2.2
2.1
2.0
3.4
3.2
2.6
2.2
2.3
3.6
2.0
2.7
1.6
3.3
1.9
2.5
2.6
2.6
2.2
2.8
2.8
2.9
3.0
2.8
2.6
2.6
3.0
2.0
4.2
3.0
Mar
f(RH)
3.8
1.7
3.7
4.4
4.4
4.4
2.0
3.7
2.2
3.6
3.2
3.6
2.7
3.5
1.9
1.7
1.8
3.5
3.1
2.6
2.0
2.2
3.8
2.0
2.7
1.4
3.2
1.5
2.5
2.4
2.4
1.9
2.8
2.3
2.6
2.6
2.9
2.5
2.7
2.9
1.7
3.8
2.8
Apr
f(RH)
3.6
1.4
3.6
4.3
4.3
4.3
2.1
3.5
2.1
3.4
3.0
3.5
2.5
3.3
1.8
1.4
1.4
2.6
2.6
2.8
2.1
2.1
3.6
2.1
2.9
1.1
3.1
1.5
2.2
2.1
2.1
1.6
2.5
2.0
2.4
2.3
2.7
2.2
2.4
2.7
1.4
4.0
2.7
May
f(RH)
3.4
1.3
3.2
3.8
3.9
3.8
2.2
3.2
2.1
3.3
3.2
2.9
3.5
3.2
1.8
1.3
1.3
2.4
2.5
2.9
2.2
2.1
3.8
2.3
2.9
1.1
3.2
1.6
2.2
2.1
2.1
1.6
2.5
2.0
2.4
2.3
2.6
2.1
2.9
3.2
1.3
4.2
3.1
Jun
f(RH)
3.1
1.2
3.0
3.4
3.7
3.4
1.8
2.9
1.9
3.0
3.8
3.2
3.1
2.9
1.6
1.2
1.2
2.2
2.3
3.0
1.8
1.9
3.9
2.0
3.1
1.0
3.6
1.5
2.1
1.8
1.8
1.4
2.4
1.8
2.4
2.2
3.0
1.8
3.1
3.6
1.1
4.6
3.4
Jul
f(RH)
2.9
1.6
2.7
2.7
3.4
2.7
1.7
2.6
1.6
2.9
3.4
2.7
3.2
2.8
1.8
1.5
1.4
2.1
2.4
3.3
1.7
1.7
4.2
1.9
3.5
1.4
3.8
1.7
2.2
1.7
1.7
1.7
2.5
1.4
2.1
1.9
3.3
1.7
3.2
3.6
1.5
5.0
3.5
Class I Area,
Aug
f(RH)
3.0
1.9
2.8
2.7
3.6
2.7
1.8
2.7
1.5
3.1
3.6
3.3
3.5
2.9
2.1
1.8
1.7
2.2
2.4
3.5
1.8
1.6
4.2
1.9
3.6
1.7
3.8
1.9
2.2
1.8
1.8
2.0
2.6
1.4
2.0
1.8
3.6
1.7
3.5
3.9
1.8
5.2
3.5
Sep
f(RH)
3.5
1.7
3.2
3.1
4.2
3.1
2.0
2.9
1.8
3.5
3.6
3.8
3.5
3.4
2.1
1.6
1.6
2.2
2.5
3.6
2.0
1.8
3.7
2.0
3.8
1.5
3.7
2.0
2.3
1.9
1.9
1.9
2.7
1.5
2.3
2.0
3.7
1.8
3.5
3.9
1.6
4.5
3.5
Oct
f(RH)
4.3
1.6
4.1
4.3
5.1
4.3
1.9
3.6
2.0
4.2
3.4
4.3
3.1
4.1
1.8
1.6
1.5
2.4
2.5
3.2
1.9
2.1
3.4
1.8
3.3
1.4
3.5
1.7
2.2
1.8
1.8
1.7
2.6
2.0
2.7
2.5
3.3
1.9
3.0
3.5
1.5
3.7
3.3
Nov
f(RH)
4.9
1.9
4.8
5.2
5.5
5.2
2.1
4.6
2.3
4.7
3.3
4.5
2.8
4.7
2.2
2.0
1.8
2.4
2.9
3.0
2.1
2.4
3.6
2.0
3.2
1.5
3.4
1.8
2.2
1.9
1.9
2.1
2.4
2.9
3.2
3.3
3.5
2.3
2.7
3.2
1.8
3.9
3.1
Dec
f(RH)
5.0
2.3
4.8
5.3
5.6
5.3
2.1
4.7
2.4
4.7
3.4
4.4
3.1
4.8
2.4
2.3
2.1
2.9
3.3
2.9
2.1
2.5
3.4
1.9
3.2
2.0
3.6
2.0
2.3
2.1
2.1
2.3
2.6
3.3
3.3
3.4
3.4
2.5
2.9
3.3
2.2
4.2
3.3
A-8
-------
Guidance for Estimating Natural Visibility Conditions Under the Regional Haze Rule
Table A-2 Recommended Monthly Site-Specific f(RH)
Based on the Representative
Class 1 Area
South Warner
Strawberry Mountain
Superstition
Swanquarter
Sycamore Canyon
Teton
Theodore Roosevelt
Thousand Lakes
Three Sisters
Tuxedni
UL Bend
Upper Buffalo
Ventana
Virgin Islands (b)
Voyageurs
Washakie
Weminuche
West Elk
Wheeler Peak
White Mountain
Wichita Mountains
Wind Cave
Wolf Island
Yellowstone
Yolla Bolly - Middle Eel
Yosemite
Site Name
Lava Beds
Starkey
Tonto
Swanquarter
Sycamore Canyon
Yellowstone
Theodore Roosevelt
Lassen Volcanic
Three Sisters
Tuxedni
UL Bend
Upper Buffalo
Pinnacles
Virgin Islands
Voyageurs
North Absoraka
Weminuche
White River
Wheeler Peak
White Mountain
Wichita Mountains
Wind Cave
Okefenokee
Yellowstone
Trinity
Yosemite
87
76
44
14
47
66
61
90
84
103
64
27
92
106
24
67
55
56
35
37
30
60
16
66
104
96
Code
LABE1
STAR1
TONT1
SWAN1
SYCA1
YELL2
THRO1
LAVO1
THSI1
TUXE1
ULBE1
UPBU1
PINN1
VIIS1
VOYA2
NOAB1
WEMI1
WHRI1
WHPE1
WHIT1
WIMO1
WICA1
OKEF1
YELL2
TRIN1
YOSE1
Site St
CA
OR
AZ
NC
AZ
WY
ND
CA
OR
AK
MT
AR
CA
VI
MN
WY
CO
CO
NM
NM
OK
SD
GA
WY
CA
CA
LAT
41.63
45.13
33.63
35.38
35.13
44.63
46.88
40.63
44.38
59.75
47.63
35.88
36.38
18.75
48.38
44.63
37.63
39.13
36.63
33.38
34.63
43.63
30.63
44.63
40.88
37.63
LONG
-121.62
-118.62
-111.12
-76.12
-111.87
-110.37
-103.37
-121.62
-122.12
-152.75
-108.62
-93.12
-121.12
-155.75
-92.87
-109.37
-107.87
-106.87
-105.37
-105.62
-98.62
-103.37
-82.12
-110.37
-122.87
-119.62
Values for Each Mandatory Federal
IMPROVE Site Location
Jan
f(RH)
4.0
4.3
2.1
2.9
2.4
2.5
2.9
3.7
5.3
3.6
2.6
3.2
3.4
2.7
2.4
2.5
2.2
2.4
2.2
2.8
2.5
3.3
2.5
4.0
3.0
Feb
f(RH)
3.4
3.8
1.9
2.7
2.4
2.3
2.8
3.1
4.6
3.4
2.4
2.9
3.4
2.4
2.2
2.3
2.2
2.2
1.9
2.6
2.5
3.0
2.3
3.4
2.9
Mar
f(RH)
3.1
3.2
1.6
2.6
2.0
2.2
2.8
2.8
4.4
2.9
2.4
2.6
3.5
2.3
2.2
2.0
2.0
1.9
1.6
2.4
2.5
3.2
2.2
3.2
2.7
Apr
f(RH)
2.8
2.9
1.3
2.4
1.6
2.1
2.4
2.4
4.3
2.8
2.3
2.7
2.6
2.2
2.1
1.7
2.0
1.8
1.5
2.4
2.5
3.0
2.1
2.9
2.2
May
f(RH)
2.6
2.7
1.2
2.7
1.5
2.1
2.4
2.3
3.8
2.8
2.2
3.1
2.4
2.2
2.1
1.7
2.0
1.8
1.5
2.7
2.6
3.2
2.1
2.8
2.1
Jun
f(RH)
2.4
2.4
1.1
3.0
1.2
1.9
2.5
2.1
3.4
2.9
2.1
3.1
2.2
2.8
1.9
1.5
1.7
1.6
1.4
2.5
2.5
3.8
1.9
2.6
1.7
Jul
f(RH)
2.2
2.0
1.4
3.1
1.5
1.7
2.4
2.0
2.7
3.6
1.9
3.0
2.1
2.5
1.6
1.7
1.8
1.8
1.7
2.2
2.2
3.4
1.7
2.5
1.5
Class I Area,
Aug
f(RH)
2.2
2.1
1.7
3.2
2.0
1.6
2.2
2.0
2.7
3.9
1.8
3.0
2.2
2.7
1.5
2.0
2.1
2.1
1.9
2.4
2.2
3.6
1.6
2.6
1.5
Sep
f(RH)
2.4
2.4
1.6
3.1
1.9
1.8
2.2
2.1
3.1
3.8
1.9
3.2
2.2
2.9
1.8
1.9
2.1
2.1
2.0
2.7
2.1
3.6
1.8
2.7
1.6
Oct
f(RH)
2.8
3.3
1.5
3.0
1.8
2.1
2.3
2.3
4.3
3.4
2.2
3.0
2.4
2.5
2.0
1.7
1.8
1.8
1.7
2.5
2.2
3.4
2.1
2.9
1.8
Nov
f(RH)
3.6
4.2
1.7
2.7
2.0
2.4
3.0
3.1
5.2
3.5
2.6
3.0
2.4
2.8
2.3
2.2
2.1
2.2
1.8
2.6
2.6
3.3
2.4
3.6
2.3
Dec
f(RH)
4.0
4.5
2.1
2.9
2.3
2.5
3.0
3.5
5.3
3.7
2.6
3.2
2.9
2.7
2.4
2.4
2.1
2.4
2.1
2.8
2.5
3.4
2.5
3.9
2.7
a: No paniculate matter sampling or visibility monitoring
b:f(RH) values for Virgin Islands National Park were not
is conducted in the Bering Sea Wilderness.
calculated because of the limited RH data available.
A-9
-------
Guidance for Estimating Natural Visibility Conditions Under the Regional Haze Rule
Table A-3 Monthly Site-Specific f(RH) Values for Each Mandatory Federal Class I
Based on the Centroid of the Area (Supplemental Information)
Class 1 Area
Acadia
Agua Tibia
Alpine Lakes
Anaconda - Pintler
Ansel Adams
Arches
Badlands
Bandelier
Bering Sea (a)
Big Bend
Black Canyon of the Gunnison
Bob Marshall
Bosque del Apache
Boundary Waters Canoe Area
Breton
Bridger
Brigantine
Bryce Canyon
Cabinet Mountains
Caney Creek
Canyonlands
Cape Romain
Capitol Reef
Caribou
Carlsbad Caverns
Chassahowitzka
Chiricahua NM
Chiricahua W
Cohutta
Crater Lake
Craters of the Moon
Cucamonga
Denali
Desolation
Diamond Peak
Dolly Sods
Dome Land
Eagle Cap
Eagles Nest
Site Name
Acadia
Agua Tibia
Snoqualmie Pass
Sula
Kaiser
Canyonlands
Badlands
Bandelier
Big Bend
Weminuche
Monture
Bosque del Apache
Boundary Waters
Breton
Bridger
Brigantine
Bryce Canyon
Cabinet Mountains
Caney Creek
Canyonlands
Cape Romain
Capitol Reef
Lassen Volcanic
Guadalupe Mountains
Chassahowitzka
Chiricahua
Chiricahua
Cohutta
Crater Lake
Craters of the Moon
San Gabriel
Denali
Bliss
Crater Lake
Dolly Sods
Dome Land
Starkey
White River
Map ID
1
100
80
71
110
50
59
33
31
55
73
38
23
20
65
5
49
75
29
50
15
52
90
32
18
39
39
12
86
69
93
102
95
86
8
109
76
56
Code
ACAD1
AGTI1
SNPA1
SULA1
KAIS1
CANY1
BADL1
BAND1
BIBE1
WEMI1
MONT1
BOAP1
BOWA1
BRET1
BRID1
BRIG1
BRCA1
CABI1
CACR1
CANY1
ROMA1
CAPI1
LAVO1
GUMO1
CHAS1
CHIR1
CHIR1
COHU1
CRLA1
CRMO1
SAGA1
DENA1
BLIS1
CRLA1
DOSO1
DOME1
STAR1
WHRI1
Site
St
ME
CA
WA
MT
CA
UT
SD
NM
TX
CO
MT
NM
MN
LA
WY
NJ
UT
MT
AR
UT
SC
UT
CA
TX
FL
AZ
AZ
GA
OR
ID
CA
AK
CA
OR
WV
CA
OR
CO
LAT
44.37
33.41
47.42
45.98
37.65
38.64
43.74
35.78
60.45
29.31
38.58
47.75
33.79
47.95
29.73
42.98
39.46
37.62
48.21
34.41
38.46
32.94
38.36
40.50
32.14
28.75
32.01
31.84
34.92
42.90
43.47
34.25
63.72
38.98
43.53
39.11
35.70
45.10
39.69
LONG
68.26
116.98
121.42
113.42
119.20
109.58
101.94
106.27
172.79
103.19
107.70
113.38
106.83
91.50
88.88
109.76
74.45
112.17
115.71
94.08
109.82
79.66
111.05
121.18
104.48
82.55
109.39
109.27
84.58
122.13
113.55
117.57
148.97
120.12
122.10
79.43
118.19
117.29
106.25
Jan
f(RH)
3.3
2.4
4.3
3.3
3.0
2.6
2.6
2.2
2.0
2.4
3.6
2.1
3.0
3.7
2.5
2.8
2.6
3.8
3.4
2.6
3.3
2.7
3.7
2.1
3.8
2.0
2.0
3.3
4.6
3.1
2.5
2.5
3.2
4.5
3.0
2.5
3.8
2.2
Feb
f(RH)
2.9
2.4
3.8
2.9
2.7
2.3
2.7
2.1
1.9
2.2
3.1
1.9
2.6
3.5
2.4
2.6
2.4
3.3
3.1
2.3
3.0
2.4
3.1
2.0
3.5
2.0
1.9
3.1
3.9
2.7
2.4
2.3
2.8
4.0
2.8
2.3
3.2
2.2
Mar
f(RH)
2.8
2.4
3.5
2.5
2.4
1.8
2.6
1.8
1.6
1.9
2.8
1.6
2.7
3.7
2.3
2.7
1.9
2.9
2.9
1.7
2.9
2.0
2.8
1.6
3.4
1.6
1.6
3.0
3.7
2.3
2.4
2.1
2.4
3.6
2.8
2.2
2.5
2.0
Apr
f(RH)
3.4
2.2
3.9
2.4
2.1
1.6
2.4
1.6
1.5
1.9
2.6
1.4
2.4
3.6
2.2
2.6
1.6
2.6
3.0
1.6
2.8
1.7
2.5
1.5
3.2
1.3
1.2
2.8
3.4
2.0
2.2
1.9
2.0
3.7
2.6
1.9
2.1
2.0
May
f(RH)
3.1
2.2
2.9
2.4
1.9
1.6
2.8
1.6
1.6
1.9
2.7
1.4
2.3
3.8
2.1
3.0
1.5
2.7
3.6
1.5
3.2
1.6
2.4
1.6
3.3
1.3
1.3
3.4
3.2
2.0
2.1
1.9
1.8
3.2
3.1
1.8
2.0
2.1
Jun
f(RH)
3.0
2.2
3.2
2.3
1.7
1.3
2.7
1.4
1.6
1.6
2.7
1.3
2.9
4.0
1.8
3.2
1.3
2.7
3.6
1.2
3.7
1.4
2.2
1.6
3.9
1.1
1.1
3.8
3.0
1.8
2.1
2.2
1.6
3.1
3.4
1.8
1.9
1.9
Jul
f(RH)
3.4
2.3
2.9
2.0
1.6
1.4
2.5
1.7
1.7
1.7
2.3
1.8
3.1
4.3
1.5
3.4
1.3
2.3
3.4
1.3
3.6
1.4
2.1
1.8
3.9
1.8
1.8
4.0
2.8
1.4
2.1
2.5
1.5
2.9
3.5
1.8
1.6
1.8
Area
Aug
f(RH)
3.8
2.3
3.1
1.9
1.6
1.5
2.4
2.1
2.0
1.9
2.2
2.0
3.4
4.3
1.5
3.7
1.5
2.2
3.4
1.5
4.1
1.6
2.1
2.1
4.2
2.1
2.1
4.2
2.9
1.4
2.2
3.0
1.6
2.9
3.9
1.8
1.6
2.0
?
Sep
f(RH)
4.0
2.3
3.3
2.1
1.6
1.6
2.2
1.9
2.1
2.0
2.6
1.9
3.5
4.2
1.7
3.6
1.5
2.6
3.6
1.6
4.0
1.6
2.2
2.2
4.1
1.8
1.8
4.2
3.1
1.6
2.2
2.8
1.7
3.1
3.9
1.8
1.6
2.0
Oct
f(RH)
3.8
2.3
3.9
2.5
1.8
1.6
2.3
1.7
1.9
1.8
2.9
1.6
2.8
3.7
2.0
3.3
1.6
3.0
3.5
1.6
3.7
1.7
2.4
1.8
3.9
1.5
1.5
3.8
3.6
2.0
2.2
2.9
1.9
3.7
3.3
1.9
2.3
1.9
Nov
f(RH)
3.6
2.1
4.5
3.2
2.3
2.0
2.7
2.0
1.8
2.1
3.5
1.8
3.2
3.7
2.4
2.9
2.0
3.7
3.4
2.0
3.4
2.1
3.0
1.9
3.7
1.6
1.6
3.4
4.6
2.8
2.1
3.0
2.4
4.6
3.0
2.0
3.4
2.1
Dec
f(RH)
3.5
2.2
4.5
3.3
2.7
2.3
2.7
2.2
1.9
2.3
3.5
2.2
3.2
3.7
2.4
2.8
2.4
3.9
3.5
2.3
3.2
2.5
3.4
2.1
3.9
2.2
2.2
3.5
4.6
3.0
2.2
3.1
3.0
4.6
3.1
2.2
4.0
2.1
A -10
-------
Guidance for Estimating Natural Visibility Conditions Under the Regional Haze Rule
Table A-3 Monthly Site-Specific f(RH) Values for Each Mandatory Federal Class I
Based on the Centroid of the Area (Supplemental Information)
Class 1 Area
Emigrant
Everglades
Fitz patrick
Flat Tops
Galiuro
Gates of the Mountains
Gearhart Mountain
Gila
Glacier
Glacier Peak
Goat Rocks
Grand Canyon
Grand Teton
Great Gulf
Great Sand Dunes
Great Smoky Mountains
Guadalupe Mountains
Haleakala
Hawaii Volcanoes
Hells Canyon
Hercules - Glade
Hoover
Isle Royale
James River Face
Jarbidge
John Muir
Joshua Tree
Joyce Kilmer - Slickrock
Kaiser
Kalmiopsis
Kings Canyon
La Garita
Lassen Volcanic
Lava Beds
Linville Gorge
Lostwood
Lye Brook
Mammoth Cave
Marble Mountain
Maroon Bells - Snowmass
Site Name
Yosemite
Everglades
Bridger
White River
Chiricahua
Gates of the Mountains
Crater Lake
Gila Cliffs
Glacier
North Cascades
White Pass
Grand Canyon, Hance
Yellowstone
Great Gulf
Great Sand Dunes
Great Smoky Mountains
Guadalupe Mountains
Haleakala
Hawaii Volcanoes
Hells Canyon
Hercules - Glade
Hoover
Isle Royale
James River Face
Jarbidge
Kaiser
Joshua Tree
Great Smoky Mountains
Kaiser
Kalmiopsis
Sequoia
Weminuche
Lassen Volcanic
Lava Beds
Linville Gorge
Lostwood
Lye Brook
Mammoth Cave
Trinity
White River
Map ID
96
19
65
56
39
74
86
42
72
81
79
48
66
4
53
10
32
108
107
77
28
97
25
7
68
110
101
10
110
89
98
55
90
87
13
62
3
9
104
56
Code
YOSE1
EVER1
BRID1
WHRI1
CHIR1
GAMO1
CRLA1
GICL1
GLAC1
NOCA1
WHPA1
GRCA2
YELL2
GRGU1
GRSA1
GRSM1
GUMO1
HALE1
HAVO1
HECA1
HEGL1
HOOV1
ISLE1
JARI1
JARB1
KAIS1
JOSH1
GRSM1
KAIS1
KALM1
SEQU1
WEMI1
LAVO1
LABE1
LIGO1
LOST1
LYBR1
MACA1
TRIN1
WHRI1
Site
St
CA
FL
WY
CO
AZ
MT
OR
NM
MT
WA
WA
AZ
WY
NH
CO
TN
TX
HI
HI
OR
MO
CA
Ml
VA
NV
CA
CA
TN
CA
OR
CA
CO
CA
CA
NC
ND
VT
KY
CA
CO
LAT
38.20
25.39
43.27
39.97
32.56
46.87
42.49
33.22
48.51
48.21
46.54
35.97
43.68
44.31
37.73
35.63
31.83
20.81
19.43
45.34
36.69
38.14
47.99
37.62
41.89
37.39
34.03
35.43
37.28
42.27
36.82
37.96
40.54
41.71
35.89
48.60
43.15
37.22
41.52
39.15
LONG
119.75
80.68
109.57
107.25
110.32
111.81
120.85
108.25
114.00
121.04
121.48
111.98
110.73
71.22
105.52
83.94
104.80
156.28
155.27
116.57
92.90
119.45
88.83
79.48
115.43
118.84
116.18
84.00
119.18
123.93
118.76
106.81
121.57
121.34
81.89
102.48
73.12
86.07
123.21
106.82
Jan
f(RH)
3.2
2.7
2.5
2.3
2.0
2.9
4.0
2.1
4.0
4.2
4.3
2.4
2.6
2.8
2.4
3.3
2.0
2.7
3.2
3.7
3.2
3.1
3.1
2.8
3.0
2.9
2.4
3.3
3.0
4.5
2.8
2.3
3.8
4.0
3.3
3.0
2.7
3.4
4.4
2.2
Feb
f(RH)
2.8
2.6
2.3
2.2
1.8
2.6
3.4
1.9
3.5
3.7
3.8
2.3
2.4
2.6
2.3
3.0
2.0
2.6
2.9
3.1
2.9
2.8
2.5
2.6
2.6
2.6
2.3
3.1
2.7
3.9
2.6
2.2
3.2
3.4
3.0
2.9
2.6
3.1
3.8
2.1
Mar
f(RH)
2.5
2.6
2.2
2.0
1.5
2.4
3.1
1.6
3.2
3.4
3.4
1.9
2.2
2.6
2.0
2.9
1.6
2.6
3.0
2.5
2.7
2.5
2.7
2.7
2.1
2.4
2.2
2.9
2.5
3.8
2.4
1.9
2.9
3.1
3.0
2.9
2.6
2.9
3.7
2.0
Apr
f(RH)
2.1
2.4
2.1
2.0
1.2
2.3
2.8
1.3
3.1
3.8
4.2
1.5
2.1
2.8
1.9
2.7
1.5
2.5
3.0
2.2
2.7
2.1
2.4
2.4
2.1
2.1
2.0
2.7
2.1
3.5
2.1
1.8
2.5
2.7
2.7
2.3
2.6
2.6
3.3
2.0
May
f(RH)
1.9
2.4
2.1
2.0
1.2
2.3
2.7
1.4
3.2
2.9
2.8
1.4
2.1
2.9
1.9
3.2
1.6
2.4
3.0
2.1
3.3
1.9
2.2
3.0
2.2
1.9
2.0
3.3
1.9
3.5
1.9
1.8
2.4
2.6
3.3
2.3
2.8
3.2
3.4
2.1
Jun
f(RH)
1.7
2.7
1.8
1.8
1.1
2.3
2.5
1.2
3.4
3.2
3.4
1.2
1.8
3.2
1.8
3.9
1.5
2.3
2.9
2.0
3.3
1.6
2.6
3.3
2.2
1.7
1.9
3.8
1.7
3.3
1.8
1.6
2.2
2.4
3.9
2.6
3.0
3.5
3.2
1.7
Jul
f(RH)
1.5
2.6
1.5
1.7
1.5
2.0
2.3
2.1
2.8
2.9
3.0
1.4
1.5
3.5
1.9
3.8
1.9
2.5
3.1
1.6
3.3
1.5
3.0
3.4
1.6
1.7
2.0
4.0
1.6
3.2
1.7
1.7
2.1
2.3
4.1
2.7
3.3
3.7
3.2
1.9
Area
Aug
f(RH)
1.6
2.9
1.5
1.9
1.8
1.9
2.3
2.0
2.6
3.1
3.2
1.7
1.5
3.8
2.3
4.0
2.2
2.4
3.2
1.6
3.3
1.5
3.2
3.7
1.4
1.7
2.0
4.2
1.7
3.2
1.7
2.1
2.1
2.3
4.5
2.4
3.6
3.9
3.2
2.2
1
Sep
f(RH)
1.6
3.0
1.7
1.9
1.6
2.1
2.4
1.8
3.2
3.3
3.1
1.6
1.7
4.0
2.2
4.2
2.2
2.4
3.2
1.8
3.4
1.6
3.8
3.6
1.4
1.7
2.0
4.2
1.7
3.3
1.8
2.0
2.2
2.4
4.4
2.3
3.7
3.9
3.2
2.1
Oct
f(RH)
1.9
2.8
2.0
1.8
1.5
2.4
2.8
1.6
3.5
3.9
3.8
1.6
2.0
3.4
1.9
3.8
1.8
2.5
3.2
2.4
3.1
1.8
2.7
3.2
1.6
1.9
2.0
3.8
1.9
3.6
1.9
1.8
2.4
2.7
3.7
2.4
3.3
3.4
3.4
1.8
Nov
f(RH)
2.4
2.6
2.4
2.2
1.6
2.8
3.7
1.8
3.8
4.4
4.4
1.9
2.4
3.1
2.4
3.3
1.9
2.8
3.7
3.5
3.1
2.3
3.3
2.8
2.4
2.2
1.9
3.3
2.3
4.4
2.3
2.2
3.1
3.5
3.2
3.2
2.9
3.2
4.1
2.1
Dec
f(RH)
2.9
2.7
2.4
2.2
2.1
2.8
3.8
2.2
3.9
4.4
4.6
2.3
2.6
2.9
2.4
3.4
2.2
2.7
3.2
3.9
3.3
2.8
3.3
3.0
2.8
2.6
2.0
3.5
2.7
4.3
2.5
2.3
3.5
3.8
3.4
3.2
2.8
3.5
4.2
2.1
A-11
-------
Guidance for Estimating Natural Visibility Conditions Under the Regional Haze Rule
Table A-3 Monthly Site-Specific f(RH) Values for Each Mandatory Federal Class I
Based on the Centroid of the Area (Supplemental Information)
Class 1 Area
Mazatzal
Medicine Lake
Mesa Verde
Mingo
Mission Mountains
Mokelumne
Moosehorn
Mount Adams
Mount Baldy
Mount Hood
Mount Jefferson
Mount Rainier
Mount Washington
Mount Zirkel
Mountain Lakes
North Absaroka
North Cascades
Okefenokee
Olympic
Otter Creek
Pasayten
Pecos
Petrified Forest
Pine Mountain
Pinnacles
Point Reyes
Presidential Range - Dry River
Rawah
Red Rock Lakes
Redwood
Rocky Mountain
Roosevelt Campobello
Saguaro
Saint Marks
Salt Creek
San Gabriel
San Gorgonio
San Jacinto
San Pedro Parks
San Rafael
Site Name
Ike's Backbone
Medicine Lake
Mesa Verde
Mingo
Monture
Bliss
Moosehorn
White Pass
Mount Baldy
Mount Hood
Three Sisters
Mount Rainier
Three Sisters
Mount Zirkel
Crater Lake
North Absoraka
North Cascades
Okefenokee
Olympic
Dolly Sods
Pasayten
Wheeler Peak
Petrified Forest
Ike's Backbone
Pinnacles
Point Reyes
Great Gulf
Mount Zirkel
Yellowstone
Redwood
Rocky Mountain
Moosehorn
Saguaro
Saint Marks
Salt Creek
San Gabriel
San Gorgonio
San Gorgonio
San Pedro Parks
San Rafael
Map ID
46
63
54
26
73
95
2
79
43
85
84
78
84
58
86
67
81
16
83
8
82
35
41
46
92
91
4
58
66
88
57
2
40
17
36
93
99
99
34
94
Code
IKBA1
MELA1
MEVE1
MING1
MONT1
BLIS1
MOOS1
WHPA1
BALD1
MOHO1
THSI1
MORA1
THSI1
MOZI1
CRLA1
NOAB1
NOCA1
OKEF1
OLYM1
DOSO1
PASA1
WHPE1
PEFO1
IKBA1
PINN1
PORE1
GRGU1
MOZI1
YELL2
REDW1
ROMO1
MOOS1
SAGU1
SAMA1
SACR1
SAGA1
SAGO1
SAGO1
SAPE1
RAFA1
Site
St
AZ
MT
CO
MO
MT
CA
ME
WA
AZ
OR
OR
WA
OR
CO
OR
WY
WA
GA
WA
WV
WA
NM
AZ
AZ
CA
CA
NH
CO
WY
CA
CO
ME
AZ
FL
NM
CA
CA
CA
NM
CA
LAT
33.92
48.50
37.20
36.98
47.40
38.58
45.12
46.19
34.12
45.38
44.55
46.76
44.30
40.55
42.34
44.77
48.54
30.74
47.32
39.00
48.85
35.93
35.08
34.31
36.49
38.12
44.21
40.70
44.67
41.56
40.28
44.88
32.25
30.12
33.61
34.27
34.18
33.75
36.11
34.78
LONG
111.43
104.29
108.49
90.20
113.85
120.03
67.26
121.50
109.57
121.69
121.83
122.12
121.87
106.70
122.11
109.78
121.44
82.13
123.35
79.65
120.52
105.64
109.77
1 1 1 .80
121.16
122.90
71.35
105.94
111.70
124.08
105.55
66.95
110.73
84.08
104.37
117.94
116.90
116.65
106.81
119.83
Jan
f(RH)
2.1
3.0
2.5
3.3
3.6
3.2
3.0
4.3
2.2
4.3
4.4
4.4
4.4
2.2
4.3
2.4
4.1
3.5
4.5
3.0
4.2
2.3
2.4
2.2
3.2
3.6
2.8
2.1
2.7
4.4
1.7
3.0
1.8
3.7
2.1
2.5
2.7
2.5
2.3
2.8
Feb
f(RH)
1.9
2.9
2.3
3.0
3.1
2.8
2.7
3.8
2.0
3.8
3.9
4.0
3.9
2.2
3.6
2.3
3.7
3.2
4.1
2.8
3.7
2.1
2.2
2.0
2.8
3.3
2.6
2.1
2.5
3.9
1.9
2.7
1.6
3.4
1.9
2.5
2.8
2.4
2.1
2.7
Mar
f(RH)
1.7
2.9
1.9
2.8
2.7
2.4
2.7
3.4
1.7
3.5
3.6
3.6
3.6
2.0
3.3
2.2
3.4
3.1
3.8
2.8
3.4
1.8
1.7
1.7
2.6
3.1
2.6
2.0
2.3
4.6
1.9
2.7
1.4
3.4
1.5
2.4
2.6
2.4
1.8
2.7
Apr
f(RH)
1.3
2.3
1.5
2.6
2.5
2.0
3.0
4.4
1.4
3.9
3.7
4.7
3.7
2.1
3.0
2.2
3.7
3.0
4.1
2.6
3.7
1.7
1.4
1.4
2.4
2.7
2.8
2.1
2.1
3.9
2.1
3.0
1.1
3.4
1.5
2.2
2.3
2.2
1.6
2.4
May
f(RH)
1.3
2.2
1.5
3.0
2.6
1.9
3.0
2.9
1.3
3.0
3.1
3.1
3.1
2.2
2.9
2.1
2.9
3.6
3.2
3.2
2.9
1.7
1.3
1.3
2.3
2.5
3.0
2.3
2.1
4.5
2.3
3.0
1.1
3.5
1.7
2.2
2.2
2.1
1.6
2.3
Jun
f(RH)
1.1
2.5
1.3
3.2
2.6
1.6
3.1
3.5
1.2
3.2
3.1
3.7
3.1
1.9
2.6
1.9
3.2
3.7
3.5
3.5
3.2
1.5
1.2
1.1
2.0
2.3
3.4
2.0
1.9
4.7
2.0
3.1
1.1
4.0
1.6
2.1
1.9
2.0
1.4
2.3
Jul
f(RH)
1.5
2.5
1.6
3.3
2.3
1.5
3.4
3.1
1.6
2.9
2.9
3.3
3.0
1.7
2.5
1.7
2.9
3.7
3.1
3.7
2.9
1.8
1.5
1.4
2.0
2.5
3.7
1.8
1.7
4.9
1.8
3.4
1.4
4.1
1.8
2.2
1.8
2.1
1.7
2.5
Area
Aug
f(RH)
1.7
2.2
2.0
3.5
2.2
1.6
3.8
3.3
1.9
3.0
2.9
3.5
2.9
1.9
2.5
1.6
3.2
4.1
3.5
4.1
3.2
2.1
1.8
1.8
2.1
2.6
4.0
2.0
1.6
4.7
2.0
3.8
1.8
4.4
2.0
2.2
1.9
2.1
2.0
2.5
1
Sep
f(RH)
1.6
2.2
1.9
3.5
2.5
1.7
3.9
3.1
1.7
3.1
3.0
3.4
3.0
2.0
2.6
1.8
3.5
4.0
3.7
4.0
3.3
2.0
1.7
1.6
2.1
2.6
4.3
2.0
1.8
4.3
1.9
3.9
1.6
4.2
2.1
2.2
1.9
2.1
1.9
2.4
Oct
f(RH)
1.5
2.4
1.7
3.1
2.9
1.9
3.5
3.9
1.6
3.9
3.8
4.1
3.8
1.9
3.1
2.0
3.9
3.8
4.4
3.3
3.9
1.7
1.6
1.5
2.3
2.7
3.5
1.9
2.1
3.7
1.8
3.5
1.4
3.8
1.8
2.3
1.9
2.1
1.7
2.5
Nov
f(RH)
1.7
3.2
2.1
3.1
3.5
2.4
3.2
4.5
1.8
4.5
4.6
4.7
4.6
2.1
4.1
2.4
4.4
3.5
4.8
3.0
4.4
2.0
1.9
1.7
2.5
2.9
3.1
2.1
2.6
3.8
1.8
3.3
1.6
3.7
1.8
2.1
1.9
2.0
2.1
2.3
Dec
f(RH)
2.1
3.2
2.3
3.3
3.6
2.9
3.2
4.6
2.2
4.6
4.5
4.7
4.6
2.1
4.3
2.4
4.4
3.6
4.8
3.1
4.5
2.2
2.3
2.1
2.9
3.3
3.0
2.0
2.7
3.4
1.7
3.2
2.1
3.8
2.1
2.2
2.2
2.1
2.2
2.5
A-12
-------
Guidance for Estimating Natural Visibility Conditions Under the Regional Haze Rule
Table A-3 Monthly Site-Specific f(RH) Values for Each Mandatory Federal Class I
Based on the Centroid of the Area (Supplemental Information)
Class 1 Area
Sawtooth
Scapegoat
Selway - Bitterroot
Seney
Sequoia
Shenandoah
Shining Rock
Sierra Ancha
Simeonof
Sipsey
South Warner
Strawberry Mountain
Superstition
Swanquarter
Sycamore Canyon
Teton
Theodore Roosevelt
Thousand Lakes
Three Sisters
Tuxedni
UL Bend
Upper Buffalo
Ventana
Virgin Islands (b)
Voyageurs
Washakie
Weminuche
West Elk
Wheeler Peak
White Mountain
Wichita Mountains
Wind Cave
Wolf Island
Yellowstone
Yolla Bolly - Middle Eel
Yosemite
Zion
Site Name
Sawtooth
Monture
Sula
Seney
Sequoia
Shenandoah
Shining Rock
Sierra Ancha
Simeonof
Sipsey
Lava Beds
Starkey
Tonto
Swanquarter
Sycamore Canyon
Yellowstone
Theodore Roosevelt
Lassen Volcanic
Three Sisters
Tuxedni
UL Bend
Upper Buffalo
Pinnacles
Virgin Islands
Voyageurs
North Absoraka
Weminuche
White River
Wheeler Peak
White Mountain
Wichita Mountains
Wind Cave
Okefenokee
Yellowstone
Trinity
Yosemite
Zion
Map ID
70
73
71
22
98
6
11
45
105
21
87
76
44
14
47
66
61
90
84
103
64
27
92
106
24
67
55
56
35
37
30
60
16
66
104
96
51
Code
SAWT1
MONT1
SULA1
SENE1
SEQU1
SHEN1
SHRO1
SIAN1
SIME1
SIPS1
LABE1
STAR1
TONT1
SWAN1
SYCA1
YELL2
THRO1
LAVO1
THSI1
TUXE1
ULBE1
UPBU1
PINN1
VIIS1
VOYA2
NOAB1
WEMI1
WHRI1
WHPE1
WHIT1
WIMO1
WICA1
OKEF1
YELL2
TRIN1
YOSE1
ZION1
Site
St
ID
MT
MT
Ml
CA
VA
NC
AZ
AK
AL
CA
OR
AZ
NC
AZ
WY
ND
CA
OR
AK
MT
AR
CA
VI
MN
WY
CO
CO
NM
NM
OK
SD
GA
WY
CA
CA
UT
LAT
44.18
47.17
45.86
46.26
36.50
38.52
35.39
33.82
54.92
34.34
41.33
44.30
33.63
35.31
34.03
44.09
47.30
40.70
44.29
60.15
47.55
35.83
36.22
18.33
48.59
43.95
37.65
38.69
36.57
33.49
34.74
43.55
31.31
44.55
40.11
37.71
37.25
LONG
114.93
112.73
114.00
86.03
118.82
78.44
82.78
110.88
159.28
87.34
120.20
118.73
111.10
76.28
116.18
110.18
104.00
121.58
122.04
152.60
107.87
93.21
121.59
64.79
93.17
109.59
107.80
107.19
105.42
105.83
98.59
103.48
81.30
110.40
122.96
119.70
113.01
Jan
f(RH)
3.3
3.2
3.5
3.3
2.5
3.1
3.3
2.1
4.3
3.4
3.6
3.9
2.1
2.9
2.4
2.5
2.9
3.8
4.5
3.5
2.7
3.3
3.2
2.8
2.5
2.4
2.3
2.3
2.1
2.7
2.5
3.4
2.5
4.0
3.3
2.7
Feb
f(RH)
2.9
2.8
3.0
2.8
2.4
2.8
3.0
2.0
4.1
3.1
3.1
3.3
1.9
2.7
2.3
2.4
2.8
3.2
4.0
3.3
2.5
3.0
2.9
2.4
2.3
2.2
2.2
2.2
1.9
2.6
2.5
3.1
2.4
3.4
3.0
2.4
Mar
f(RH)
2.3
2.6
2.6
2.9
2.4
2.8
2.9
1.7
3.6
2.9
2.7
2.8
1.6
2.6
2.2
2.2
2.8
2.9
3.6
2.9
2.5
2.7
2.8
2.4
2.2
1.9
1.9
1.9
1.6
2.4
2.5
3.1
2.3
3.1
2.8
2.0
Apr
f(RH)
2.0
2.4
2.3
2.7
2.2
2.5
2.7
1.3
3.9
2.8
2.4
2.9
1.3
2.5
2.0
2.1
2.3
2.5
3.7
2.7
2.3
2.8
2.4
2.3
2.1
1.7
1.9
1.8
1.5
2.4
2.5
3.0
2.2
2.8
2.3
1.6
May
f(RH)
2.0
2.5
2.4
2.6
1.9
3.1
3.4
1.3
3.9
3.3
2.3
2.3
1.3
2.9
2.0
2.1
2.3
2.4
3.1
2.7
2.2
3.4
2.3
2.3
2.1
1.7
1.9
1.8
1.5
3.0
2.7
3.3
2.2
2.7
2.1
1.5
Jun
f(RH)
1.8
2.4
2.3
3.1
1.8
3.4
3.9
1.1
4.3
3.7
2.1
2.4
1.1
3.2
1.9
1.9
2.5
2.2
3.1
2.9
2.2
3.4
2.1
3.1
1.8
1.5
1.7
1.6
1.4
2.7
2.5
3.7
1.9
2.5
1.8
1.3
Jul
f(RH)
1.4
2.1
1.9
3.6
1.7
3.5
4.1
1.5
5.0
3.9
1.9
2.0
1.5
3.4
2.0
1.6
2.4
2.1
3.0
3.6
2.0
3.4
2.2
2.7
1.6
1.6
1.8
1.8
1.8
2.3
2.3
3.7
1.7
2.4
1.5
1.2
Area
Aug
f(RH)
1.4
2.0
1.9
4.0
1.6
3.9
4.5
1.8
5.2
3.9
1.9
2.0
1.7
3.5
2.0
1.5
2.2
2.1
2.9
4.0
1.8
3.4
2.3
3.0
1.5
2.0
2.1
2.2
2.0
2.5
2.3
4.1
1.6
2.5
1.5
1.4
1
Sep
f(RH)
1.5
2.3
2.1
4.1
1.8
3.9
4.4
1.6
4.5
3.9
2.0
1.9
1.6
3.4
2.0
1.7
2.2
2.2
3.0
3.9
1.9
3.6
2.2
3.2
1.8
1.9
2.0
2.1
2.0
2.9
2.2
4.0
1.8
2.6
1.5
1.4
Oct
f(RH)
2.0
2.6
2.6
3.4
1.9
3.2
3.8
1.5
3.8
3.6
2.3
2.6
1.5
3.1
2.0
2.0
2.3
2.4
3.8
3.5
2.2
3.3
2.4
2.6
2.0
1.7
1.8
1.8
1.7
2.6
2.2
3.7
2.1
2.7
1.8
1.6
Nov
f(RH)
2.9
3.1
3.3
3.6
2.3
3.0
3.3
1.7
4.0
3.3
3.1
3.7
1.7
2.8
1.9
2.4
3.0
3.1
4.6
3.5
2.7
3.2
2.5
2.9
2.4
2.1
2.1
2.2
1.8
2.7
2.6
3.5
2.5
3.3
2.4
2.0
Dec
f(RH)
3.3
3.1
3.5
3.5
2.3
3.1
3.4
2.1
4.3
3.4
3.4
4.1
2.1
2.9
2.0
2.5
3.0
3.5
4.6
3.7
2.7
3.3
2.9
2.8
2.5
2.3
2.2
2.3
2.1
2.8
2.6
3.5
2.5
3.6
2.8
2.4
a: No paniculate matter sampling or visibility monitoring
b:f(RH) values for Virgin Islands National Park were not
is conducted in the
calculated because
Bering Sea Wilderness.
of the limited RH data available.
A-13
-------
Guidance for Estimating Natural Visibility Conditions Under the Regional Haze Rule
A-14
-------
Guidance for Estimating Natural Visibility Conditions Under the Regional Haze Rule
Monthly Average Relative Humidity Weighting Factors (February)
-1997)
Relative Humidity
Weighting Factors
• >e
• 5.5-6.0
* 5.0-5.5
i 4.5-5.0
4.0-4.5
I 3.5-4.0
3.0-3.5
3 2.5-3.0
| 2.0-2.5
• 1.5-2.0
• 1.0-1.5
4. NWS Site
$ NFS Site
U IMPROVE Site
CASTNet Site
Figure A-l Monthly Average f(RH) Values for February
(all weather stations shown)
A -15
-------
Guidance for Estimating Natural Visibility Conditions Under the Regional Haze Rule
Monthly Average Relative Humidity Weighting Factors (May)
Relative Humidity
Weighting Factors
NPS Site
IMPROVE Site
CASTNet Site
Figure A-2 Monthly Average f(RH) Values for May
(all weather stations shown)
A-16
-------
Guidance for Estimating Natural Visiblity Conditions Under the Regional Haze Program
Monthly Average Relative Humidity Weighting Factors (August)
(1988 -1997)
Relative Humidity
Weighting Factors
• >6
• 5.5-6.0
5.0-5.5
4.5-5.0
4.0-4.5
3.5-4.0
3.0-3.5
I 2.5-30
• 2.0-2.5
I 1.5-2.0
• 1.0-1.5
NWS Site
NFS Site
IMPROVE Site
CASTNet Site
Figure A-3 Monthly Average f(RH) Values for August
(all weather stations shown)
A-17
-------
Appendix B
Default Natural bext, dv, and 10th and 90th Percentile
dv Values at All Mandatory Federal Class I Areas
B-l
-------
Appendix B
Default Natural b^ dv, and 10th and 90th Percentile
dv Values at All Mandatory Federal Class I Areas
Mandatory Federal Class 1 Area
Acadia NP
Agua Tibia Wilderness
Alpine Lake Wilderness
Anaconda-Pintler Wilderness
Arches NP
Badlands NP
Bandelier NM
Bering Sea
Big Bend NP
Black Canyon of the Gunnison NM
Bob Marshall Wilderness
Bosque del Apache
Boundary Waters Canoe Area
Breton
Bridger Wilderness
Brigantine
Bryce Canyon NP
Cabinet Mountains Wilderness
Caney Creek Wilderness
Canyonlands NP
Cape Romain
Capitol Reef NP
Caribou Wilderness
Carlsbad Caverns NP
Chassahowitzka
Chiricahua NM
Chiricahua Wilderness
Cohutta Wilderness
Crater Lake NP
Craters of the Moon NM
Cucamonga Wilderness
Denali Preserve NP
Desolation Wilderness
Diamond Peak Wilderness
Dolly Sods Wilderness
Dome Land Wilderness
Eagle Cap Wilderness
State
ME
CA
WA
MT
UT
SD
NM
AK
TX
CO
MT
NM
MN
LA
WY
NJ
UT
MT
AR
UT
SC
UT
CA
NM
FL
AZ
AZ
GA
OR
ID
CA
AK
CA
OR
WV
CA
OR
Lat.
44.35
33.42
47.55
45.95
38.73
43.81
35.79
60.46
29.33
38.57
47.68
33.79
48.06
29.87
42.99
39.49
37.57
48.18
34.41
38.23
32.99
38.06
40.49
32.12
28.69
32.01
31.86
34.93
42.92
43.39
34.24
63.31
38.9
43.53
39
35.84
45.22
Lon.
-68.24
-116.99
-121.16
-113.5
-109.58
-102.36
-106.34
-172.75
-103.31
-107.75
-113.23
-106.85
-91 .43
-88.82
-109.49
-74.39
-112.17
-115.68
-94.08
-109.91
-79.49
-111.15
-121.21
-104.59
-82.66
-109.34
-109.28
-84.57
-122.13
-113.54
-117.59
-151.19
-120.17
-122.1
-79.37
-118.23
-117.37
bext
(Mm-1)
21.40
15.86
16.99
16.03
15.58
16.06
15.62
15.48
15.68
16.17
15.54
20.89
21.57
15.71
21.05
15.58
16.27
21.14
15.60
21.22
15.63
16.05
15.61
21.46
15.47
15.45
21.39
16.74
15.80
15.85
16.27
15.80
16.84
21.13
15.70
16.12
Ann. Avg.
(dv)
7.61
4.61
5.30
4.72
4.43
4.74
4.46
4.37
4.50
4.80
4.41
7.37
7.69
4.52
7.44
4.43
4.87
7.49
4.45
7.52
4.47
4.73
4.46
7.63
4.36
4.35
7.60
5.15
4.57
4.61
4.86
4.57
5.21
7.48
4.51
4.78
Best Days
(dv) (a|
3.77
2.05
2.74
2.16
1.87
2.18
1.90
1.81
1.94
2.24
1.85
3.53
3.85
1.96
3.60
1.87
2.31
3.65
1.89
3.68
1.91
2.17
1.90
3.79
1.80
1.79
3.76
2.59
2.01
2.05
2.30
2.01
2.65
3.64
1.95
2.22
Worst Days
(dv) (a|
11.45
7.17
7.86
7.28
6.99
7.30
7.02
6.93
7.06
7.36
6.97
11.21
11.53
7.08
11.28
6.99
7.43
11.33
7.01
11.36
7.03
7.29
7.02
11.47
6.92
6.91
11.44
7.71
7.13
7.17
7.42
7.13
1.11
11.32
7.07
7.34
B-2
-------
Appendix B
Default Natural b^ dv, and 10th and 90th Percentile
dv Values at All Mandatory Federal Class I Areas
Mandatory Federal Class 1 Area
Eagles Nest Wilderness
Emigrant Wilderness
Everglades NP
Fitzpatrick Wilderness
Flat Tops Wilderness
Galiuro Wilderness
Gates of the Mountains Wilderness
Gearhart Mountain Wilderness
Gila Wilderness
Glacier NP
Glacier Peak Wilderness
Goat Rocks Wilderness
Grand Canyon NP
Grand Teton NP
Great Gulf Wilderness
Great Sand Dunes NM
Great Smoky Mountains NP
Guadalupe Mountains NP
Haleakala NP
Hawaii Volcanoes NP
Hells Canyon Wilderness
Hercules-Glades Wilderness
Hoover Wilderness
Isle Royale NP
James River Face Wilderness
Jarbidge Wilderness
John Muir Wilderness
Joshua Tree NM
Joyce-Kilmer-Slickrock Wilderness
Kaiser Wilderness
Kalmiopsis Wilderness
Kings Canyon NP
La Garita Wilderness
Lassen Volcanic NP
Lava Beds NM
Linville Gorge Wilderness
Lostwood
State
CO
CA
FL
WY
CO
AZ
MT
OR
NM
MT
WA
WA
AZ
WY
NH
CO
TN
TX
HI
HI
OR
MO
CA
Ml
VA
NV
CA
CA
TN
CA
OR
CA
CO
CA
CA
NC
ND
Lat.
39.67
38.18
25.35
43.24
39.95
32.6
46.86
42.51
33.21
48.64
48.21
46.52
36.3
43.82
44.3
37.77
35.6
31.91
20.71
19.41
45.54
36.68
38.11
48.01
37.59
41.77
36.97
33.92
35.44
37.28
42.26
36.92
37.95
40.49
41.76
35.88
48.59
Lon.
-106.29
-119.77
-80.98
-109.6
-107.3
-110.39
-111.82
-120.86
-108.47
-113.84
-121
-121.47
-112.79
-110.71
-71 .28
-105.57
-83.52
-104.85
-156.16
-155.34
-116.59
-92.9
-119.37
-88.83
-79.44
-115.35
-118.88
-115.88
-83.99
-119.17
-123.92
-118.61
-106.83
-121.41
-121.52
-81.9
-102.46
bext
(Mm-1)
15.72
15.81
20.77
15.73
15.70
15.40
15.93
16.33
15.51
16.48
16.88
16.93
15.51
15.74
21.10
15.74
21.39
15.64
16.02
16.33
16.09
21.03
15.78
20.91
20.96
15.75
15.80
15.72
21.40
15.80
16.74
15.79
15.69
16.08
16.37
21.36
16.11
Ann. Avg.
(dv)
4.52
4.58
7.31
4.53
4.51
4.32
4.66
4.90
4.39
5.00
5.24
5.26
4.39
4.53
7.47
4.54
7.60
4.47
4.71
4.91
4.76
7.43
4.56
7.38
7.40
4.54
4.58
4.52
7.61
4.57
5.15
4.57
4.50
4.75
4.93
7.59
4.77
Best Days
(dv) (a|
1.96
2.02
3.47
1.97
1.95
1.76
2.10
2.34
1.83
2.44
2.68
2.70
1.83
1.97
3.63
1.98
3.76
1.91
2.15
2.35
2.20
3.59
2.00
3.54
3.56
1.98
2.02
1.96
3.77
2.01
2.59
2.01
1.94
2.19
2.37
3.75
2.21
Worst Days
(dv) (a|
7.08
7.14
11.15
7.09
7.07
6.88
7.22
7.46
6.95
7.56
7.80
7.82
6.95
7.09
11.31
7.10
11.44
7.03
7.27
7.47
7.32
11.27
7.12
11.22
11.24
7.10
7.14
7.08
11.45
7.13
7.71
7.13
7.06
7.31
7.49
11.43
7.33
B-3
-------
Appendix B
Default Natural b^ dv, and 10th and 90th Percentile
dv Values at All Mandatory Federal Class I Areas
Mandatory Federal Class 1 Area
Lye Brook Wilderness
Mammoth Cave NP
Marble Mountain Wilderness
Maroon Bells-Snowmass Wilderness
Mazatzal Wilderness
Medicine Lake
Mesa Verde NP
Minarets Wilderness
Mingo
Mission Mountains Wilderness
Mokelumne Wilderness
Moosehorn
Mount Adams Wilderness
Mount Baldy Wilderness
Mount Hood Wilderness
Mount Jefferson Wilderness
Mount Rainier NP
Mount Washington Wilderness
Mount Zirkel Wilderness
Mountain Lakes Wilderness
North Absaroka Wilderness
North Cascades NP
Okefenokee
Olympic NP
Otter Creek Wilderness
Pasayten Wilderness
Pecos Wilderness
Petrified Forest NP
Pine Mountain Wilderness
Pinnacles NM
Point Reyes NS
Presidential Range-Dry River Wilderness
Rainbow Lake Wilderness
Rawah Wilderness
Red Rock Lakes
Redwood NP
Rocky Mountain NP
State
VT
KY
CA
CO
AZ
MT
CO
CA
MO
MT
CA
ME
WA
AZ
OR
OR
WA
OR
CO
OR
WY
WA
GA
WA
WV
WA
NM
AZ
AZ
CA
CA
NH
Wl
CO
MT
CA
CO
Lat.
43.13
37.2
41.51
39.1
34.13
48.49
37.25
37.74
37
47.48
38.57
45.09
46.2
33.95
45.37
44.61
46.86
44.3
40.75
42.33
44.74
48.83
30.82
47.77
38.99
48.89
35.9
34.99
34.31
36.48
38.06
44.2
46.42
40.69
44.64
41.44
40.35
Lon.
-73.02
-86.15
-123.21
-107.02
-111.56
-104.35
-108.45
-119.19
-90.19
-113.87
-120.06
-67.29
-121.49
-109.54
-121.73
-121.84
-121.72
-121.88
-106.68
-122.11
-109.8
-121.35
-82.33
-123.74
-79.65
-120.44
-105.62
-109.79
-111.8
-121.19
-122.9
-71 .34
-91.31
-105.95
-111.78
-124.03
-105.7
bext
(Mm-1)
20.99
21.58
16.65
15.70
15.44
16.07
15.73
15.78
21.03
16.21
15.80
21.22
16.86
15.51
16.83
16.91
17.05
17.03
15.71
16.50
15.74
16.86
21.41
17.02
21.14
16.84
15.65
15.54
15.47
16.12
16.20
21.15
20.99
15.72
15.81
16.90
15.67
Ann. Avg.
(dv)
7.41
7.69
5.10
4.51
4.35
4.74
4.53
4.56
7.43
4.83
4.58
7.52
5.22
4.39
5.21
5.25
5.34
5.33
4.52
5.01
4.53
5.22
7.61
5.32
7.49
5.21
4.48
4.41
4.36
4.78
4.83
7.49
7.42
4.52
4.58
5.25
4.49
Best Days
(dv) (a|
3.57
3.85
2.54
1.95
1.79
2.18
1.97
2.00
3.59
2.27
2.02
3.68
2.66
1.83
2.65
2.69
2.78
2.77
1.96
2.45
1.97
2.66
3.77
2.76
3.65
2.65
1.92
1.85
1.80
2.22
2.27
3.65
3.58
1.96
2.02
2.69
1.93
Worst Days
(dv) (a|
11.25
11.53
7.66
7.07
6.91
7.30
7.09
7.12
11.27
7.39
7.14
11.36
7.78
6.95
111
7.81
7.90
7.89
7.08
7.57
7.09
7.78
11.45
7.88
11.33
111
7.04
6.97
6.92
7.34
7.39
11.33
11.26
7.08
7.14
7.81
7.05
B-4
-------
Appendix B
Default Natural b^ dv, and 10th and 90th Percentile
dv Values at All Mandatory Federal Class I Areas
Mandatory Federal Class 1 Area
Roosevelt Campobello International Park
Saguaro NM
Salt Creek
San Gabriel Wilderness
San Gorgonio Wilderness
San Jacinto Wilderness
San Pedro Parks Wilderness
San Rafael Wilderness
Sawtooth Wilderness
Scapegoat Wilderness
Selway-Bitterroot Wilderness
Seney
Sequoia NP
Shenandoah NP
Shining Rock Wilderness
Sierra Ancha Wilderness
Simeonof
Sipsey Wilderness
South Warner Wilderness
St. Marks
Strawberry Mountain Wilderness
Superstition Wilderness
Swanquarter
Sycamore Canyon Wilderness
Teton Wilderness
Theodore Roosevelt NP
Thousand Lakes Wilderness
Three Sisters Wilderness
Tuxedni
UL Bend
Upper Buffalo Wilderness
Ventana Wilderness
Virgin Islands NP (b)
Voyageurs NP
Washakie Wilderness
Weminuche Wilderness
West Elk Wilderness
State
ME
AZ
NM
CA
CA
CA
NM
CA
ID
MT
ID
Ml
CA
VA
NC
AZ
AK
AL
CA
FL
OR
AZ
NC
AZ
WY
ND
CA
OR
AK
MT
AR
CA
VI
MN
WY
CO
CO
Lat.
44.85
32.17
33.6
34.27
34.12
33.75
36.11
34.76
43.99
47.16
46.12
46.25
36.51
38.47
35.38
33.85
54.91
34.32
41.31
30.11
44.29
33.5
35.39
35.01
44.04
46.96
40.7
44.04
60.14
47.54
36.17
36.21
18.35
48.47
44.1
37.61
38.75
Lon.
-66.94
-110.61
-104.41
-117.94
-116.84
-116.64
-106.81
-119.81
-115.06
-112.74
-114.86
-86.09
-118.56
-78.49
-82.85
-110.9
-159.28
-87.44
-120.2
-84.15
-118.74
-111.27
-76.39
-112.09
-110.17
-103.46
-121.58
-121.91
-152.61
-107.89
-92.41
-121.6
-64.74
-92.8
-109.57
-107.25
-107.21
bext
(Mm-1)
21.22
15.35
15.58
15.86
15.74
15.78
15.63
16.03
15.82
16.05
16.09
21.23
15.79
20.98
21.40
15.46
17.21
21.28
16.09
21.54
16.37
15.40
20.91
15.53
15.74
16.08
16.10
17.01
16.58
15.87
21.04
16.09
20.64
15.73
15.68
15.71
Ann. Avg.
(dv)
7.52
4.28
4.43
4.61
4.54
4.56
4.47
4.72
4.59
4.73
4.76
7.53
4.57
7.41
7.61
4.36
5.43
7.55
4.76
7.67
4.93
4.32
7.38
4.40
4.53
4.75
4.76
5.31
5.06
4.62
7.44
4.76
7.25
4.53
4.50
4.51
Best Days
(dv) (a|
3.68
1.72
1.87
2.05
1.98
2.00
1.91
2.16
2.03
2.17
2.20
3.69
2.01
3.57
3.77
1.80
2.87
3.71
2.20
3.83
2.37
1.76
3.54
1.84
1.97
2.19
2.20
2.75
2.50
2.06
3.60
2.20
3.41
1.97
1.94
1.95
Worst Days
(dv) (a|
11.36
6.84
6.99
7.17
7.10
7.12
7.03
7.28
7.15
7.29
7.32
11.37
7.13
11.25
11.45
6.92
7.99
11.39
7.32
11.51
7.49
6.88
11.22
6.96
7.09
7.31
7.32
7.87
7.62
7.18
11.28
7.32
11.09
7.09
7.06
7.07
B-5
-------
Appendix B
Default Natural b^ dv, and 10th and 90th Percentile
dv Values at All Mandatory Federal Class I Areas
Mandatory Federal Class 1 Area
Wheeler Peak Wilderness
White Mountain Wilderness
Wichita Mountains
Wind Cave NP
Wolf Island
Yellowstone NP
Yolla Bolly Middle Eel Wilderness
Yosemite NP
Zion NP
State
NM
NM
OK
SD
GA
WY
CA
CA
UT
Lat.
36.57
33.48
34.75
43.58
31.33
44.63
40.09
37.85
37.32
Lon.
-105.4
-105.85
-98.65
-103.47
-81.3
-110.51
-122.96
-119.54
-113.04
bext
(Mm-1)
15.70
15.56
20.60
15.97
21.33
15.77
16.25
15.81
15.56
Ann. Avg.
(dv)
4.51
4.42
7.23
4.68
7.58
4.56
4.85
4.58
4.42
Best Days
(dv) (a|
1.95
1.86
3.39
2.12
3.74
2.00
2.29
2.02
1.86
Worst Days
(dv) (a|
7.07
6.98
11.07
7.24
11.42
7.12
7.41
7.14
6.98
(a) Values for the best and worst days are estimated from a statistical approach described in Section 2.6 of this document.
(b) f(RH) values for Virgin Islands National Park were not calculated because of the limited RH data available. As such no
estimates for Natural Visibility Conditions are presented at this time.
B-6
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TECHNICAL REPORT DATA
(Please read Instructions on reverse before completing)
1. REPORT NO.
EPA-454/B-03-005
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
Guidance for Estimating Natural Visibility Conditions Under the
Regional Haze Program
5. REPORT DATE
September 2003
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
U.S. EPA/OAR/OAQPS/EMAD/AQTAG
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Office of Air Quality Planning and Standards
Emissions, Monitoring and Analysis Division
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
68-D-02-0261
Work Order No. 1-06
12. SPONSORING AGENCY NAME AND ADDRESS
Director
Office of Air Quality Planning and Standards
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVERED
Guidance document
14. SPONSORING AGENCY CODE
EPA/200/04
15. SUPPLEMENTARY NOTES
16. ABSTRACT
The purpose of this document is to provide guidance to the States in implementing the regional haze program under the
Clean Air Act. As part of the program, States will develop goals and implement strategies for improving visibility in
each mandatory Federal Class I area. Estimates of natural visibility conditions are needed by the States for the goal
development process. This guidance document describes "default"16 and "refined" approaches for estimating natural
conditions. EPA believes that natural conditions estimates developed using the default approach will be adequate to
satisfy the requirements of the regional haze rule for the initial SIP submittals due no later than 2008. This document
provides guidance to EPA Regional, State, and Tribal air quality management authorities and the general public, on
how EPA intends to exercise its discretion in implementing Clean Air Act provisions and EPA regulations, concerning
the estimation of natural conditions under the regional haze program.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b. IDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Regional Haze, Haze Index
Air Pollution control
18. DISTRIBUTION STATEMENT
19. SECURITY CLASS (Report)
Unclassified
21. NO. OF PAGES
Unlimited
20. SECURITY CLASS (Page)
Unclassified
EPA Form 2220-1 (Rev. 4-77) PREVIOUS EDITION IS OBSOLETE
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United States
Environmental Protection
Agency
Office of Air Quality Planning and Standards
Emissions, Monitoring and Analysis Division
Research Triangle Park, NC
Publication No. EPA-454/B-03-005
September 2003
Postal information in this section where appropriate.
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