EPA-450/4-88-015
Workbook for Plume Visual Impact
Screening and Analysis
^r, Bou/e l?,h n
60604-3590 ' J00f
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Air Quality Planning and Standards
Technical Support Division
Research Triangle Park NC 27711
September 1988
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This report has been reviewed by the Office of Air Quality Planning and Standards, US EPA, and has been approved for
publication. Mention of trade names or commercial products is not intended to constitute endorsement or recommendation for
use. Copies of this report are available, for a fee, from the National Technical Services, 5285 Port Royal Road, Springfield VA
22161.
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ACKNOWLEDGMENTS
This workbook was prepared by Douglas A. Latimer, Gaia Associates,
San Rafael, CA, and Robert G. Ireson, Systems Applications, Inc., San
Rafael, CA. This work was sponsored by the U. S. Environmental Protection
Agency (EPA) and the National Park Service (NPS). The authors are partic-
ularly grateful for the guidance and helpful comments provided by the NPS
and EPA Project Officers, David B Joseph and Jawad S. Touma. William
Malm, Donald Henderson, and Ronald Henry provided advice and reviewed
sections of this workbook. Marianne Dudik of Systems Applications, Inc.
restructured and enhanced the VISCREEN model developed by the authors.
in
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CONTENTS
Acknowl edgments i i i
Nomenclature vi i
1 INTRODUCTION 1
2 GENERAL CONCEPTS 5
What Makes a Plume Visible 5
What Causes Plume Contrast 8
Plume Effects on Light Transmission 10
Plume Contrast Against the Sky 16
Plume Contrast Against Terrain 17
Plume Perceptibi 1 ity 19
3 LEVEL-1 SCREENING 21
Assumptions in Level-1 Screening 22
Preparing Level-1 Input 22
Exercising the Screening Model VISCREEN 24
4 LEVEL-2 SCREENING 39
Selecting Particle Size Distributions 39
Determining Worst-Case Plume Dispersion Conditions 41
Accounting for Complex Terrain 49
Exercising VISCREEN 50
Alternative Use of Plume Visibility Models 50
5 LEVEL-3 ANALYSIS 51
Objectives of Level-3 Analysis 51
Suggestions for Level-3 Analysis 55
Frequency Distribution of Dispersion Conditions 55
Calculating Plume Visual Impacts 56
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Coupling Magnitude and Frequency 57
Interpreting the Cumulative Frequency Curve 57
Summarizing Results 58
Optional Use of VISCREEN 58
References « 59
Appendix A: Perceptibility Thresholds and Recommended
Screening Analysis Criteria for Plumes and
Haze Layers
Appendix B: The Plume Visual Impact Screening Model (VISCREEN)
Appendix C: Examples of Plume Visual Impact Screening and Analysis
Appendix D: VISCREEN Listing
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NOMENCLATURE
~ Light absorption coefficient of an air parcel,
proportional to concentrations of nitrogen dioxide
and aerosol (e.g., soot) that absorb visible radiation
(ra-1)
— Light extinction coefficient of an air parcel, the sum of
absorption and scattering coefficients (m )
bR — Light scattering coefficient of particle-free air caused
1
by Rayleigh scatter from air molecules (m )
bscat ~~ Light scattering coefficient resulting from Rayleigh
scatter (air molecules) and Mie scatter (particles), the
sum of bp and bsp (m"1)
O
(bexj./m) — Light extinction efficiency per unit species mass (m /g)
(bscat/V) — Light scattering efficiency per unit aerosol volume
concentration (m /cm )
b. — Light scattering coefficient caused by particles only
^ i
(m-1)
C ~ Contrast at a given wavelength of two colored objects such
as plume/sky or sky/terrain
Snin ~~ Contrast that is just perceptible, a threshold contrast
Cpiume — Contrast of a plume against a viewing background such as
the sky or a terrain feature
Cr — Contrast of a terrain feature at distance r against the
sky
ACr — Change in sky/terrain contrast caused by a plume or extra
extinction
CQ ~ Intrinsic contrast of a terrain feature against the sky.
The sky/terrain contrast at r = 0. For a black object,
C0 = -1
vn
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d — Distance between the emission source and the observer (m)
AE(L*a*b*) — Color difference parameter used to characterize the
perceptibility of the difference between two colors. In
the context of this workbook, it is used to characterize
the perceptibility of a plume on the basis of the color
difference between the plume and a viewing background such
as the sky, a cloud, or a terrain feature. Color
differences are due to differences in three dimensions:
brightness (L*) and color hue and saturation (a*, b*)
Fs -- Solar insolation or flux incident on an air parcel within
pi
a given wavelength band (watt m~ ym"1)
I — Light intensity or radiance for a given line of sight and
911
wavelength band (watt m~ sr~1pm~1). Subscripts t and h
refer to terrain and horizon, respectively.
Iohi — Light intensity reflected from an object such as a terrain
? 1 1
feature (watt m sr urn )
p(x,e) — Phase function, a parameter that relates the portion of
total scattered light of a given wavelength x that is
scattered in a given direction specified by the scattering
angle 9
Q — Emission rate of a species, such as SC^, or plume flux at
a given downwind distance, which may be less than the
emission rate because of surface deposition and chemical
conversion (g s ). Subscripts refer to species
considered (e.g., SC^, SOT, and particulate)
r — Distance along the line of sight from the viewed object to
the observer (m)
rQ — Object-observer distance (m)
r_ — Distance from observer to centroid of plume material (m)
rv — Visual range, a parameter characteristic of the clarity of
the atmosphere, inversely proportional to the extinction
coefficient. It is the farthest distance at which a black
object is perceptible against the horizon sky (m)
rVQ — Background visual range without plume (m)
t ~ Time (s)
vm
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u ~ Wind speed (m s )
WD ~ Wind direction
x — Downwind distance from emission source (m)
xmin»xmax "~ Dl'starice along plume axis from emission source to the
closest and most distant Class I area boundaries (m)
x — Wavelength of light (m)
p — Density of a particle (g m~3)
a — Horizontal angle between a line of sight and the plume
centerline
s — Vertical angle between a line of sight and the horizontal
Y — Plume offset angle, horizontal angle between the line
between the emission source and the observer and the plume
centerline
$ — Azimuthal line-of-sight angle, horizontal angle between
the line connecting the emission source and the observer
and the line of sight
4» — Vertical angular subtense of plume
x — Concentration of a given species in an air parcel (g m )
T — Optical thickness of a plume, the line-of-sight integral
of the extinction coefficient. Subscripts refer to the
component of the total, or plume, optical thickness (e.g.,
particulate, SO^, N02)
[ ] ~ Denotes the concentration of the species within brackets
u — Albedo of the plume or background atmosphere, the ratio of
the scattering coefficient to the extinction coefficient
e ~ Scattering angle, the angle between direct solar radiation
and the line of sight. If the observer were looking
directly at the sun, 9 would equal 0°. If the observer
were looking away from the sun, 9 would equal 180°.
ix
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1 INTRODUCTION
This guidance document is designed to assist the user in the evaluation of
plume visual impact as required by the Prevention of Significant Deteri-
oration (PSD) and visibility regulations of the U.S. Environmental Protec-
tion Agency (EPA). Sources of air pollution can cause visible plumes if
emissions of particulates and nitrogen oxides are sufficiently large. A
plume will be visible if its constituents scatter or absorb sufficient
light so that the plume is brighter or darker than its viewing background
(e.g., the sky or a terrain feature such as a mountain). PSD Class I
areas such as national parks and wilderness areas are afforded special
visibility protection designed to prevent such plume visual impacts to
observers within a Class I area.
The objective of this document is to provide guidance on the assessment of
plume visual impacts, including the use of a plume visual impact screening
model (VISCREEN), which can be used to calculate the potential visual
impact of a plume of specified emissions for specific transport and dis-
persion (meteorological) conditions. VISCREEN can be applied in two suc-
cessive levels of screening (Levels 1 and 2) without the need for exten-
sive input specification. If screening calculations using VISCREEN
demonstrate that during worst-case meteorological conditions a plume is
either imperceptible or, if perceptible, is not likely to be considered
objectionable (i.e., "adverse" or "significant" in the language of the EPA
PSD and visibility regulations), further analysis of plume visual impact
would not be required as part of the air quality review of a source. How-
ever, if screening demonstrates that criteria are exceeded, plume visual
impacts cannot be ruled out, and more detailed plume visual impact analy-
sis to ascertain the magnitude, frequency, location, and timing of plume
visual impacts would be required. Such detailed plume visual impact
analysis is called Level-3 analysis and is carried out by more sophistica-
ted plume visibility models such as PLUVUE II. Figure 1 shows a logic
flow diagram of the three levels of plume visual impact screening and
analysis.
This guidance document and the screening model VISCREEN are designed to
replace the procedures described in the "Workbook for Estimating Visi-
bility Impairment" (Latimer and Ireson, 1980). The procedures described
in this document are simplified by use of the screening model VISCREEN,
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Level-I
Screen
Using VISCREEN
INPUT:
• NOx and paniculate
emissions
• Background visual range
• Distance to Gass I area
Calculate contrast and AE
values on worst-case
assumptions using VISCREEN
Level-2
Screen
Using VISCREEN,
a Plume
Visibility Model
INPUT: All of the
above plus:
• Worst-case meteorology
• Size distributions
Calculate worst-day visual
impacts based on actual area
conditions using one or more
of the following:
(1) VISCREEN
(2) Plume visibility model
Level-3
Analysis
Using Plume
Visibility
Model
INPUT: All of the
above, plus:
• Joint frequency of wind
speed, wind direction,
stability, mixing depth,
and background ozone
concentration and visual
range
Visual
impact is not
judged to be
adverse or
significant
Calculate magnitude and frequency
of occurrence of visual impact
using plume visibility models
Visual
impact is not
judged to be
adverse or
significant
Is
impact judge
to be adverse
or significant
by govern:
ment^.
'es
Visual
impact is
judged to be
adverse or
ignificant
Analyze Alternatives
• Better emission controls
• Alternative sites
• Scaled-down source size
FIGURE 1. Logic flow diagram for 3-level plume visual impact analysis.
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instead of the hand calculation encouraged by the earlier document.
VISCREEN is designed to evaluate plume visual effects along the plume's
entire length for two different viewing backgrounds and for two different
sun angles. One important design feature of VISCREEN that distinguishes
it from the earlier EPA Visibility Workbook is the evaluation of the
potential perceptibility of plumes using recent psychophysical concepts
(see Appendix A).
In addition, to simplify the plume visual impact screening and analysis
process, this guidance is limited to assessing the visibility of a plume
itself, not whether the plume contributes to reductions in general visi-
bility. Thus, a source's contribution to regional haze is not considered
in this guidance. Although regional haze is the most extensive and seri-
ous form of visibility impairment throughout the United States and in
Class I areas, it is caused by multiple sources located throughout a
region. A single emission source may contribute to such a problem but is
generally not the sole (or even major) contributor. The protection and
improvement of regional visibility must be achieved through broader regu-
latory action than is possible with the review of a single emission
source. In addition, regional haze analysis requires a different analysis
tool: regional dispersion models, rather than plume models. However, the
process of assuring that plume visual impacts are not objectionable to
visitors to Class I areas may contribute to the broader visibility
protection issue by limiting industrial source siting near Class I
areas.
These guidelines are designed to be brief and straightforward. The reader
interested in more detail is advised to refer to the 1980 EPA Visibility
Workbook (Latimer and Ireson, 1980). In addition, citations for several
references regarding visibility and visibility modeling are provided in
the reference section of this document. These sources can be consulted if
the reader is interested in the details of visibility modeling, the
derivation of formulas used in VISCREEN, and the broader regulatory, pol-
icy, and technical issues associated with visibility protection.
This guidance document is organized as follows: Section 2 provides a
brief overview of the concepts used in plume visual impact screening and
analysis including a description of parameters used to characterize the
perceptibility of plumes. Section 3 provides a step-by-step procedure for
implementation of the simplest, Level-1 screening analysis. Section 4
provides guidance on Level-2 screening, including the determination of
worst-case meteorological conditions. Section 5 provides suggestions
regarding the most detailed, Level-3 plume visual impact analysis that is
required only if a source fails both the Level-1 and -2 screening tests.
A discussion of plume perceptibility threshold research is presented in
Appendix A. Technical documentation and a listing of the plume visual
impact screening model VISCREEN are provided in Appendixes B and D,
respectively. Examples of plume visual impact screening and analysis
calculations are provided in Appendix C.
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GENERAL CONCEPTS
In this section we oresent a brief overview of the concepts required to
understand Lhe technical approach used in plume visual impact screening
and analysis. More detailed background information can be obtained from
the references cited in the back of this document.
First, we discuss what makes a plume visible. Then, we present an over-
view of light scattering and absorption in the atmosphere and the emis-
sions that are responsible. Next we describe the specific geometries
assumed for plume visual impact analysis and present the basic formulas
describing plume visual impact. Finally, we discuss plume perceptibility
screening criteria.
WHAT MAKES A PLUME VISIBLE
The objective of plume visual impact screening and analysis is to deter-
mine whether or not a plume is visible as an object itself. To understand
what makes a plume visible, we first ask what makes any object visible.
Any viewed object is visually perceptible to a human observer if the light
emanating from the object and impinging on the retina of the eye is
sufficiently different from light emanating from other objects so that the
difference or contrast between the given object and surrounding objects
(its viewing background) produces a perceptible signal to the optic nerve
and the brain. Visual perception requires contrast. Contrast can be
large as in the case of this black type on white paper, or contrast can be
small as in the case of touch-up paint that doesn't quite match.
Since the human eye responds differently to different wavelengths of
light, the eye responds to color as well as brightness. The range of
wavelengths to which the human eye responds is called the visible spectrum
and ranges from the short-wavelength (0.4 micrometer, pm) blue to the
middle-wavelength (0.55 ym) green to the long-wavelength (0.7 ym) red.
Contrast can be defined at any wavelength as the relative difference in
the intensity (called spectral radiance) between the viewed object and its
background:
C =
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where C is the contrast and IQbj and lKac|< are the light intensities (or
spectral radiances) of the object and its background.
If the viewed object is brighter than its background, it will have a posi-
tive contrast. For example, a white cloud viewed against a dark blue sky
will have a positive contrast. If the object is darker than the back-
ground, its contrast is negative. For example, a distant mountain is
usually visible because of a negative contrast against the horizon sky
(unless the .Mountain is snow-covered, in which case its contrast is gener-
ally positive).
Figure 2 illustrates the concept of contrast at different wavelengths with
four hypothetical objects. Object 1 has spectral radiance distribution
defined by 1^ over the visible spectrum. Because Object 1's spectral
radiance is uniform over all visible wavelengths, it is nominally white.
Object 2 is darker than Object 1 because spectral radiances at all wave-
lengths are lower than those for Object 1. In addition, Object 2 is a
different color because there is relatively more light at the red end of
the visible spectrum than at the blue end. The contrast of Object 2
against Object 1 is negative at all wavelengths, but blue contrasts are
more negative than both green and red wavelengths. As a result Object 2
would appear dark red (brown) compared to Object 1. Similarly, Object 3
would appear as a dark blue, and Object 4 would appear as an even darker
gray (or black). If Object 3 were the viewing background for Object 2,
its contrast at the blue end of the visible spectrum would be negative,
while its contrast at the red end would be positive. Thus, contrasts at
all wavelengths in the visible spectrum characterize the brightness and
color of a viewed object (such as a visible plume) relative to its viewing
background.
In the plume visual impact screening model VISCREEN, contrasts at three
wavelengths (0.45, 0.55, and 0.65 pm) are used to characterize blue,
green, and red regions of the visible spectrum. In the plume visibility
model PLUVUE, calculations are performed for 39 wavelengths. Thus, we can
ascertain whether a plume will be brighter or darker or discolored
compared to its viewing background by evaluating its contrasts in the
blue, green, and red portions of the visible spectrum. If plume contrast
is positive, the plume is brighter than its viewing background; if
negative, the plume is darker. If contrasts are different at different
wavelengths, the plume is discolored. If contrasts are all zero, the
plume is indistinguishable from its background (i.e., imperceptible).
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o
u
4/
&
V)
Wavelengths used
in V (SCREEN ,
i I
0.4
x
0.45
(blue)
0.55
(green)
0.65
(red)
0.7
Vavelength of Light
FIGURE 2. Example distributions of light intensity
of four objects.
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WHAT CAUSES PLUME CONTRAST
The contrast of this black text against the white paper is caused by dif-
ferences in the amount of light reflected from the page. Almost all of
the light impinging on the white paper is reflected, and almost none of
the light impinging on the black ink is reflected; hence, the text has a
large negative contrast (C = -1). Plume contrast is caused by a somewhat
different set of physical processes: plume contrast results from an
increase or decrease in light transmitted from the viewing background
through the plume to the observer.
This increase or decrease in light intensity (spectral radiance) is caused
by plume constituents that scatter and/or absorb light. There are only
two common plume constituents that scatter or absorb light. Particulates,
depending on their nature, can scatter light or both scatter and absorb
light. Nitrogen dioxide (Nf^) absorbs light of all wavelengths in the
visible spectrum but it is a stronger absorber at the blue end of the
spectrum.
We can characterize the atmospheric optical properties of a plume in a
manner analogous to the way plume concentrations are characterized.
Instead of using mass concentration (yg/m ), which is the mass of a given
species per unit volume of ambient air, we use parameters called the light
scattering coefficient (bscat)» the light absorption coefficient (babs),
and their sum, the light extinction coefficient (bext). These coef-
ficients are essentially the concentrations of the equivalent light scat-
tering, absorption, and extinction cross-sectional area. They are cross-
sectional area per unit volume of air; hence, their units are m /m or m .
These coefficients are similar to concentration in that they are propor-
tional to the mass concentrations of the particulates and N02 that scatter
and/or absorb light; however, since different chemical species have dif-
ferent light extinction efficiencies, there is no simple one-to-one rela-
tionship between mass concentration and light extinction. For example,
submicron particles between 0.1 and 1 ym are much more effective in scat-
tering light per unit mass than are either smaller or larger particles.
Soot is a stronger light absorber than N02 per unit mass. Table 1 shows
the light extinction efficiency of several common constituents of plumes
and background atmospheres. Light extinction coefficient (bext) is the
product of the mass concentration and the light extinction efficiency of
the given species.
Plume visual impact models account for the concentrations of various spe-
cies in a plume (e.g., N02» submicron particulate, coarse particulate, and
soot) and their light scattering and absorption properties at various
visible wavelengths (e.g., blue, green, red).
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TABLE 1. Typical light extinction efficiencies for
constituents of plumes and background atmospheres.
Light Extinction
Efficiency at
x = 0.55 urn
Constituent (m2/g)
Soot 13
Hygroscopic fine particles including 4-8
(S0~) and nitrates (NO")
Fine particles (0.1 < D < 1 urn) 3
Coarse particles (1 < D < 10 pm) 0.4
Nitrogen dioxide (N02) 0.17
Giant particles (D > 10 ym) < 0.04
Sources: Latimer et al.t 1978, 1985; Latimer and
Ireson, 1980
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PLUME EFFECTS ON LIGHT TRANSMISSION
Figure 3 shows a schematic of the viewing situation that is mathematically
represented in a plume visual impact model. A plume of limited dimensions
is embedded in an otherwise uniform background atmosphere. The observer's
line of sight intersects the center of the plume at distance r_ from the
observer and it intersects a viewing background object (e.g., a mountain)
at distance rQ. The direct rays from the sun are at angle e with respect
to the line of sight. The change in the spectral light intensity at any
point along the line of sight (either inside or outside the plume) as a
function of distance r along the line of sight is:
where
r = the distance along the line of sight from the object to
the observer;
, e)= the scattering distribution or phase function for scat-
tering angle e (see Figure 3 for definition of e) modi-
fied to account for multiple, as well as single, light
scattering;
o
Fs(x) = the solar flux (watt/m /ym) incident on the atmosphere,
bscat (x) = the light scattering coefficient, which is the sum of the
Rayleigh scattering (due to air molecules), bR, and the
scattering due to particles, bsp:
W»> = bR(x) + V1' : (2)
bext (x) = the 1-i9nt extinction coefficient, which is the sum of the
scattering, t>scat(x), and absorption, (x) babs,
coefficients:
On the right-hand side of Equation (1), the first term represents light
absorbed and scattered out of the line of sight; the second term repre-
sents light scattered into the line of sight. The values of bscat and
babs can be evaluated if the aerosol and N02 concentrations and such
characteristics as the refractive index and the size distribution of the
10
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Viewing
Background
Object
FIGURE 3. Geometry of plume, observer, viewing background,
and sun.
11
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aerosol are known. Except in the cleanest atmospheres, bs__t is dominated
by bsp; also, unless soot is present, babs is dominated by the absorption
coefficient due to NOg. Scattering and absorption are wavelength-depen-
dent, and effects are greatest at the blue end (x = 0.4 urn) of the visible
spectrum (0.4 < x < 0.7 ym). The Rayleigh scattering coefficient bR is
proportional to x ; the scattering coefficient caused by particles is
generally proportional to x~n, where 0 < n < 2. Also, N02 absorption is
greatest at the blue end. This wavelength dependence causes the natural
blue sky coloration as well as discoloration of the atmosphere.
For a uniform atmosphere, without inhomogeneities caused by plumes (where
bscat and bext do not vary with distance r along the line of sight), Equa-
tion (1) can be solved to find the intensity and coloration of the horizon
sky:
_ p(x.e)
'ext
00
(4)
The perceived intensity of distant bright and dark objects will approach
this intensity as an asymptote, as illustrated by Figure 4.
Atmospheric coloration is determined by the wavelength-dependent scatter-
ing and absorption in the atmosphere. The spectral distribution of I(x)
for x over the visible spectrum determines the perceived color and light
intensity of the viewed object. The relative contributions of scattering
(aerosols plus air) and absorption (N02) to coloration can be illustrated
by rearranging Equation (1):
1
P(X.G)
dr
'scat
(x)
Fs(x)
TOO
(5)
Note from Equation (4) that when light absorption is negligible compared
with light scattering (i.e., b . « b .), the clear horizon intensity,
_ g . „ . . SCflL cXu
I(x), is simply:
Fs(x)
(6)
We now can rewrite Equation (5):
TTU dr"
'scat'
100
- 1
(7)
12
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K*.r0)
IhU)
LIGHT INTENSITY OF HORIZON
Object-Observer Distance r
FIGURE 4. Effect of an atmosphere on the perceived light
intensity of objects.
13
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Equation (7) is thus an expression relating the effects of light scatter-
ing and light absorption to the change in spectral light intensity with
distance along a sight path. On the right-hand side of Equation (7), the
first term is the effect of light scattering, and the second term is the
effect of light absorption (NC^). As noted previously, since bscat and
^abs (<*ue to ^2) are strong functions of wavelength and are greater at
the blue end (x = 0.4 ym), atmospheric coloration can result.
Equation (7) makes clear that N0£ always tends to cause a decrease in
light intensity since the second term in Equation (7) is always nega-
tive. However, particles may brighten or darken a plume, depending on
whether the first term in Equation (7) is positive or negative. If, at a
given point along the sight path, I(x) is greater than the clean horizon
sky intensity I^g(x), then the quantity in brackets in the first term on
the right-hand side of Equation (7) will be negative, which means that the
net effect of scattering will be to remove light from the line of sight.
This effect would occur if a bright, white cloud or distant snowbank were
observed through an aerosol that did not contain h^. If, however, I(x)
is less than Iho(x)» tnen the quantity in brackets in Equation (7) will be
positive, which means that the net effect of scattering will be to add
light to the line of sight. This effect would occur if a distant, dark
mountain were observed through an aerosol that did not contain N02; scat-
tering would cause the mountain to appear lighter. Only light absorption
can cause I(x) to be less than Iho,(x)» and whenever I(x) < I^gO), scat-
tering will add light to the sight path, thereby masking the coloration
caused by N02 light absorption.
The mathematical expressions used in this document and the plume visual
impact screening model VISCREEN are simply solutions to Equation (1) for
different boundary conditions and for different values of bscat., bext,
j)(e) and FS as they are affected by natural and man-made light scatterers
and absorbers. The plume visibility models use similar formulations, but
most account for multiple scattering effects.*
Now a plume (either ground-based or elevated) may be visible because it
contrasts with a sky viewing background as shown in Figure 5(a) or it con-
trasts with a terrain feature as shown in Figure 5(b). The plume visual
impact screening model VISCREEN evaluates both of these possible viewing
backgrounds.
* Multiple scattering is light scattered into the line of sight after
previous scattering (i.e., light reflected from terrain features and
light scattered from other portions of the atmosphere).
14
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V////////////////77
(a) Plume Visible Against the Sky
(b) Plume Visible Against Terrain
FIGURE 5. Two viewing situations in which plumes may be
visible.
15
-------
Formulas for contrasts representative of both types of viewing situations
can be derived by solving Equation (1) for appropriate boundary condi-
tions.
Plume Contrast Against the Sky
Let us consider now the geometry shown in Figure 3, namely, the case of a
plume embedded in an otherwise uniform background atmosphere. If we
ignore the effects of multiple scattering, Equation (1) can be solved for
the contrast between the plume and the horizon sky background (see Figure
5a) as observed at distance rD from the plume as follows (Latimer and
Ireson, 1980):
plume
_ h-plume ~ h
«p(-bextrp)
background
(8)
where
1^ = spectral radiance of horizon sky (without plume present)
^h-plume = sPectra1 radiance of plume viewed in front of horizon sky
p^ = average phase function for the plume constituents and the
background atmosphere
u> = average albedo of plume and background, where albedo is the
ratio of light scattering to total light extinction
Tplume = Plume optical thickness along the line of sight (increment
above background)
fbextdr
'plume
16
-------
bext = background atmosphere's light extinction coefficient
r_ - distance between plume centerline and observer
Note that, depending on whether the product of the phase function and the
albedo (p~u>) for the plume is larger or smaller than that for the back-
ground, the plume will be brighter (C > 0) or darker (C < 0) than the
background horizon sky. Also note that the contrast is dependent on the
plume optical thickness (Tplume); as Tp]ume approaches zero, Cplume
approaches zero. Plume contrast also diminishes as the plume-observer
distance rp increases.
Plume Contrast Against Terrain
To characterize the types of visibility impairment represented in Figure
5(b), we need to calculate a change in sky/terrain contrast caused by a
plume:
C
with plume
r
without plume
where
J.L __ T . ,___ "* * I
C
C
- t-plume h-plume
r with plume h-plume
- !t " rh
T
without plume h
Cr = the sky-terrain contrast of a terrain
feature at distance r from an observer
It, Ih = the spectral radiances of a terrain
feature and the horizon sky (unaffected by
plume)
^t-plume* ^h-plume = tjie $Pectral radiances of plumes viewed in
front of horizon sky and terrain
For simplicity we assume that the terrain that is viewed behind the plume
has an intrinsic radiance, Iphj, which is a function of the horizon sky
radiance Ih, namely, Iobj = (1 + C0)Ih. Cg is the intrinsic contrast. If
the terrain were black, Cg would equal -1.
17
-------
Again solving Equation (1) and ignoring multiple light scattering, we can
derive the following expression for the change in terrain contrast caused
by the plume (Latimer and Ireson, 1980):
ACr = -CQ exp(-bextr0)
where rQ = distance between the terrain object and the observer.
Equations (8) and' (9) are the analytical expressions at the heart of the
plume visual impact screening model VISCREEN. Careful examination of
these two equations illustrates the following sensitivities:
1. Plume contrasts (against both the sky and terrain) increase
with increasing plume light extinction (i.e., as concentrations
of particulates and N02 in a plume increase).
2. Plume contrasts increase if the line of sight is oriented to
intersect a larger amount of plume material (i.e., the line of
sight is along the plume centerline).
3. Plume contrasts increase for sun angles and for particle size
distributions that tend to maximize the difference (both posi-
tive and negative) between the phase functions for the back-
ground atmosphere and for the plume.
4. Plume contrasts increase if the plume is moved closer to the
observer.
5. Plume contrasts increase with decreasing light extinction of the
background atmosphere (i.e., with increasing background visual
range).
6. Plume contrasts against terrain are maximum if the terrain
object is relatively close to the observer and the terrain's
intrinsic contrast is maximum (e.g., if it were black).
Since screening calculations are designed to be conservative estimates of
worst-case conditions, situations are selected to (1) maximize the concen-
trations and light scattering efficiencies of optically active plume con-
stituents, the intersection of the line of sight and the plume, the back-
ground visual range, the intrinsic contrast of terrain objects, and the
difference between background and plume phase functions; and (2) minimize
the distance between the observer and the plume. Once conservative
estimates of worst-case conditions are specified, the plume visual impact
18
-------
screening model VISCREEN uses Equations (8) and (9) to calculate plume
contrasts. If such contrast values are larger than screening criteria,
the possibility that the plume will cause significant visual impact cannot
be ruled out, and less conservative, more realistic estimates would be
required.
PLUME PERCEPTIBILITY
The perceptibility of a plu^s is a function of the plume contrast at all
visible wavelengths. Percepcioiiity is a function of changes in both
brightness and color. The color difference parameter, AE, was developed
to specify the perceived magnitude of color and brightness changes and is
used as the primary basis for determining the perceptibility of plume
visual impacts in screening analysis. Although a AE of 1 and a contrast
of 0.02 have been traditionally assumed to be the threshold of percepti-
bility, a survey of the literature (see Appendix A) suggests a broad range
of perceptibility thresholds. The most sensitive observers are able to
detect contrasts or color changes one-half this magnitude, and the casual
observer may require contrast or color changes more than two times larger
than these "traditional" values. In addition, the literature suggests
that perceptibility thresholds increase for very wide and for very narrow
plumes, with plumes less than 0.02° being essentially imperceptible.
Figure 6 summarizes the range of perceptibility thresholds supported in
the literature.
The plume visual impact screening model VISCREEN is designed to ascertain
whether the plume from a facility has the potential to be perceptible to
untrained observers under "reasonable worst case" conditions. If either
of two screening criteria is exceeded, more comprehensive (and realistic)
analyses should be carried out. The first criterion is a AE value of 2.0;
the second is a green (0.55 vim) contrast value of 0.05. In the case of
sufficiently narrow or broad plumes, the higher perception thresholds (for
diffuse-edged plumes) are used instead of the above criteria.
19
-------
1.0
0.1
c
o
0.01
0.001
Howell and Hess (1978) data:
Square-wave gratings (sharp edge)
Sine-wave gratings (diffuse edge)
Upper bound (screening criterion)
Perceptibility
"Threshold"
Data of Malm et al.
(1986) for sharp-
edged plumes
0.1 1.0
Plume Vertical Angular Subtense* (°)
10
FIGURE 6. Plume perceptibility threshold as a function of plume
thickness (
-------
LEVEL-1 SCREENING
This section describes the process of Level-1 plume vi-y'al impact screen-
ing using the screening model VISCREEN and trie brief ii.put required to
initiate the screening process. Details of the plume visual impact
screening model are provided in Appendix B.
ASSUMPTIONS IN LEVEL-1 SCREENING
Level-1 screening is designed to provide a conservative estimate of plume
visual impacts (i.e., impacts that would be larger than those calculated
with more realistic input and modeling assumptions). This conservatism is
achieved by the use within the screening model VISCREEN of worst-case
meteorological conditions: extremely stable (F) atmospheric conditions,
coupled with a very low wind speed (1 m/s) persisting for 12 hours, with a
wind that would transport the plume directly adjacent to the observer (as
shown schematically in Figure 7).
PREPARING LEVEL-1 INPUT
Through the use of default parameters, the input required for Level-1
plume visual impact screening is limited to the following:
Emission rates of particulates (including soot and primary sulfate)
and nitrogen oxides (including primary
Distance between the emission source and (1) the observer, (2) the
closest Class I area boundary, and (3) the most distant Class I area
boundary*
* It should be noted that although VISCREEN is designed primarily for
assessing plume visual impacts in Class I areas, it can also be applied
1n PSD Class II areas. In such cases these distances can be specified
arbitrarily.
21
-------
Assumed Vorst-Case_
~ Plume Centerlines
Boundary of
Class I Area
Minimum distance
to Class I area (d)
Emission
Source
FIGURE 7. Determining distances for Level-1 screening.
22
-------
Background visual range appropriate for the region in which the Class
I area is located.
Before using VISCREEN, the analyst should summarize the emission rates for
Primary particulate matter
Nitrogen oxides (NOX)
Primary nitrogen dioxide (NC^)
Soot (elemental carbon)
Primary sulfate (SOT)
S02 emissions are not required as input to VISCREEN because over the short
distances (< 200 km) and stable plume transport conditions typical of
plume visual impact screening, secondary sulfate (S0~) is not formed to a
significant degree in plumes. More sophisticated plume visibility models
treat both secondary sulfate and nitrate.
These emissions can be provided in any units convenient to the analyst
since VISCREEN will prompt the analyst for his/her choice of units of mass
(e.g., grams, kilograms, metric tonnes, pounds, or tons) and time (e.g.,
seconds, minutes, hours, days, or year). Thus, emissions can be specified
in g/s or ton/yr or whatever combination is desired.
Emission rates should be the maximum short-term rates expected during the
course of a year. The values used for plume visual impact screening
generally would be the maximum emission rates for which the air quality
permit is being applied and would correspond to those used for short-term
(i.e., 1-, 3-, and 24-hour average) air quality impact analyses.
For almost every emission source, the emission rates of the last three
species (primary N02» soot, and sulfate) can be assumed to be zero. How-
ever, if N02 is directly emitted from the emission source (e.g., from a
chemical process such as a nitric acid plant) as opposed to being formed
in the atmosphere from NOX emissions, this primary N02 can be con-
sidered. Even if primary N02 emissions are set to zero, VISCREEN assumes
that 10 percent of NOX emissions is initially converted to N02 either
within the stack of the source or within the first kilometer of plume
transport (Latimer et al., 1978). If soot is known to be emitted (e.g.,
if diesel vehicles are a component of the emissions source), its emission
rate should be provided separately from that of other particulates.
Finally, some sources (such as oil-fired power plants or smelters) may
have a significant component of primary sulfate in a size range that has
maximum light scattering efficiency. If so, primary sulfate (S04=)
emissions should be specified and input separately from either particulate
23
-------
or soot. In summary, for most sources the analyst need only input the
total particulates and NOX emission rates (the first two categories of
emissions required by VISCREEN); only the small fraction of emission
sources producing nonzero primary NC^, soot, and sulfate requires input of
these emissions to VISCREEN.
Using a topographic map of appropriate scale, the analyst should identify
the portion of the Class I area that is closest to the emission source and
measure (or compute) the distance between the emission source and this
closest boundary. This distance is the distance between the emission
source and the observer that should be input to VISCREEN (d in Figure
7). Then the analyst should draw plume centerlines offset by half a 22.5°
sector width (i.e., 11.25°) on either side of this hypothetical, worst-
case observer location as shown in Figure 7. The analyst should determine
the downwind distance (along these assumed plume centerlines) to the
closest (*m-jn) and most distant (*max) Class I area boundaries (even if
these two distances are on opposite sides of the observer). If either
xmin is greater than d, set xmin equal to d for the sake of conserva-
tism. There may be certain shapes of Class I areas where the plume
centerlines drawn on opposite sides of the observer cross boundaries more
than once. In such cases the smallest xmin and the largest xmax should be
used to be conservative (see Figure 8).
The last input needed to perform a Level-1 screening analysis is the back-
ground visual range of the region in which the Class I area is located.
Figure 9 provides recommended background visual ranges for the contiguous
United States.
With emissions, distances, and visual range as the only inputs required
for Level-1 screening, the analyst can exercise the screening model
VISCREEN.
EXERCISING THE SCREENING MODEL VISCREEN
The plume visual impact screening model VISCREEN is designed for use on
an IBM-compatible personal computer with minimal memory requirements.
VISCREEN is written in FORTRAN 77. VISCREEN can be run simply by insert-
ing the VISCREEN program diskette in the A drive and typing ArVISCREEN.
The model first requests the names of two disk files (that it will create)
to which results will be written. These include a summary file, which
will contain a formatted, tabular presentation of results, and a results
file, which includes arrays of results that can be read into spreadsheet
programs for further analyses, plotting, et cetera.
24
-------
Emission source
Lines of sight for
every 5 ° of azimuth
Plume offsety
angle Y
(= 11.25° for
Level-1 screening)^
Plume Centerline
Terrain viewing background
assumed to be at far edge
of plume
in (downwind distance
I to closest Class I area
boundary)
Boundary of
Class I Area
^max (downwind distance
to most distant Class I
area boundary)
Plume subtending
22,5 ° sector width
horizontal
FIGURE 8. Geometry of plume and observer lines of sight used for plume
visual impact screening.
25
-------
I • • • • • »\ • A •
/••••••*C
»••••• -rT%W _
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/7~*»*.".*.*.-* ' • "^
y /.• • • j^^«L"«"«
in
=5
T3
Ol O)
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ra .i-
= (fl
CO >,
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-* O)
U (U
>e s_
^3 U
CO
"(O >>
c +->
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5»^
O) -Q
CT*
26
-------
The model will request the inputs previously discussed (emissions, dis-
tances between emissions source, observer, and Class I area, and the back-
ground visual range). It will also ask whether you want default input
parameters. For Level-1 plume visual impact screening, the analyst should
use the default input offerred in VISCREEN. Once the analyst has provided
the requested input and confirmed this selection of input, VISCREEN will
begin its calculations. (Execution may take several minutes if VISCREEN
is run without a math coprocessor.)
After program execution, VISCREEN will display a summary of the Level-1
screening calculations similar to that shown in Figure 10. All four tests
are based on the screening criteria UE = 2, Cp(x = 0.55 urn) = 0.05] and
the perception threshold curve for diffuse-edged plumes shown in Figure 6.
VISCREEN will identify whether the given plume passes or exceeds four
tests. The first two tests refer to visual impacts caused by plume par-
cels located inside the boundaries of the given Class I area. The last
two tests are for plume parcels located outside the boundaries of the
Class I area.
The first two tests are used to determine visual impacts when so-called
integral vistas are not protected (or are not of concern in the given
analysis). An integral vista is a view from a location inside a Class I
area of landscape features located outside the boundaries of tl\e Class I
area. The Federal Land Manager for a given Class I area should be contac-
ted to determine whether analyses for integral vistas are required. If
not, the VISCREEN analysis results for plume parcels located outside the
Class I area could be ignored (the last two tests), and results for par-
cels within the Class I area (first two tests) would be used for screen-
ing. If integral vistas are protected as well as the within-area views,
VISCREEN results for parcels located inside and outside the Class I area
should be used to determine whether the emission source passes the given
level of screening (i.e., all four tests should be used). For views both
inside and outside the Class I area, calculations are performed for two
assumed plume-viewing backgrounds: the horizon sky and a dark terrain
object. VISCREEN assumes that the terrain object is black and located
adjacent to the plume on the side of the centerline opposite the obser-
ver. In the example shown in Figure 10, the plume from the power plant
fails all four screening tests.
After the display of the screening test summary, VISCREEN will ask the
analyst whether the calculated results for lines of sight (plume parcels)
with maximum predicted visual impact should be displayed. If selected,
VISCREEN displays a summary similar to that shown in Figure 11. This sum-
mary shows calculated plume perceptibility (color difference) aE
parameters for four lines of sight corresponding to plume parcels located
inside/outside of the Class I area and in front of sky/terrain viewing
27
-------
OVERALL RESULTS OF PLUME VISIBILITY SCREENING
SOURCE: Public Electric Coal 13
CLASS I AREA: Longview NP
INSIDE class I area --
Plume delta E EXCEEDS screening criterion for SKY background
Plume delta E DOES NOT EXCEED screening criterion for TERRAIN background
Plume contrast DOES NOT EXCEED screening criterion for SKY background
Plume contrast DOES NOT EXCEED screening criterion for TERRAIN background
OUTSIDE class I area —
Plume delta E EXCEEDS screening criterion for SKY background
Plume delta E EXCEEDS screening criterion for TERRAIN background
Plume contrast EXCEEDS screening criterion for SKY background
Plume contrast DOES NOT EXCEED screening criterion for TERRAIN background
SCREENING CRITERIA: DELTA E = 2.0
GREEN CONTRAST = .050
FIGURE 10. Sample VISCREEN screening summary.
28
-------
VIEW ANGLES (DEGREES) DIST (KM) PLUME PERCEPTIBILITY DELTA E(L*A*B*)
no phi alpha psi x rp forward backward
Line of sight with maximum perceptibility for plume viewed
against a SKY background INSIDE class I area.
33 84.4 84.4 1.39 80.0 15.7 4.7 * 2.4 *
Line of sight with maximum perceptibility for plume viewed
against a TERRAIN background INSIDE class I area.
33 84.4 84.4 1.39 80.0 15.7 1.5 .6
Line of sight with maximum perceptibility for plume viewed
against a SKY background OUTSIDE class I area.
7 35.0 133.8 .96 63.5 21.6 5.7 * 2.7 *
Line of sight with maximum perceptibility for plume viewed
against a TERRAIN background OUTSIDE class I area.
1 5.0 163.8 .29 24.9 55.8 3.4 * 1.2
* Exceeds screening criteria
FIGURE 11. Sample VISCREEN summary for lines of sight
with maximum plume perceptibility.
29
-------
backgrounds. These four lines of sight were selected by VISCREEN (from as
many as 37 lines of sight for which plume contrast calculations were made)
as the plume parcels with maximum predicted visual impact (i.e., the
largest ratio of the calculated plume AE parameter or contrast to the
screening criterion).* The lines of sight (LOS's) are described by a view
number. The plume is viewed in 5° increments of azimuth (see Figure 8)
starting from the emission source. Thus, view No. 1 would be the plume
parcel 5° to the right (or left) of the emission source. The last three
views or lines of sight are for plume parcels 1 kilometer downwind from
the source and at the nearest and most distant Class I area boundaries.
These are includea to describe the plume appearance for LOS's nearly
across the source, and at the points of plume entry and exist from the
Class I area. In addition to view number, the lines of sight are
described by three angles (see Figure 12):
4> (phi), which is the azimuthal angle (in degrees) between the line
connecting the source and observer and the line of sight;
a (alpha), the angle (in degrees) between the line of sight and the
plume centerline; and
4» (psi), the vertical angle (in degrees) subtended by the plume (see
Figure 3).
In addition, two distances relevant to the given plume parcel are provided
that are critical to the identification of perceptibility. The plume
parcel's downwind distance (x) and the distance between the observer and
the plume (rp) are provided (in kilometers). A third distance is that
from the observer to terrain background (rQ).
Results are provided for two assumed worst-case sun angles. The "forward
scatter" case refers to a situation in which the sun is in front of the
observer such that the scattering angle (e) is 10°. Such a sun angle will
tend to maximize the light scattered by plume particulates and maximize
the brightness of the plume. (In reality, such a sun angle may or may not
occur during worst-case conditions for the given line of sight). The
"backward scatter" case refers to a situation in which the sun is behind
the observer such that the scattering angle is 140°. A plume is likely to
* The largest ratio, rather than the largest AE and contrast values, is
used because a broad or narrow plume may have large AE or contrast and
yet be imperceptible (see Figure 6).
30
-------
Emission
Source
Viewing Background
Observer.
22.5
Wide Plume
FIGURE 12 . Distances and angles that specify a given line of sight.
31
-------
appear the darkest with such a sun angle. Asterisks denote values that
exceed the screening criteria.
After displaying the summary of lines of sight with maximum calculated
plume visual impact, VISCREEN asks whether AE's for lines of sight are to
be displayed. If this option is selected, VISCREEN will show all the
lines of sight analyzed in the screening procedure. These results are
displayed in order of view number, first for the sky background cases and
second for the terrain background cases. Several screens of output are
necessary to show all the lines of sight (as many as eight screens, four
for each of the two viewing backgrounds). Figure 13 is a sample of such
output.
After viewing the AE summaries and output, the analyst is given the option
of viewing plume contrast values at 0.55 ym. Plume contrasts at three
wavelengths of light are calculated by VISCREEN, and are written to the
results file. These may be useful in characterizing the relative
brightness and color of the plume compared to its viewing background. A
summary of lines of sight with maximum negative or positive green contrast
is provided (see example in Figure 14). Since maximum plume per-
ceptibility may occur for lines of sight different from those of maximum
plume contrast, the lines of sight summarized here may be different from
those in the AE summary. As for the AE summary, asterisks denote
contrasts whose absolute values exceed the screening criterion. In a
fashion similar to that for the AE summary, VISCREEN gives the analyst the
option of viewing the green plume contrast values for all lines of sight
(Figure 15) In some cases, because VISCREEN calculates results for lines
of sight every 5 degrees, one or several of the lines of sight be be
physically unrealistic. The analyst should review each line of sight,
paying particular attention to those for which screening criteria are
exceeded, to verify that screening decisions are not based on unrealistic
geometries. For example, the 10 degree forward scatter scenarios are only
possible for views to the east (mornings), south (high latitudes and
winter periods), and west (evenings). Screening decisions should be based
on the worst case impacts associated with realistic geometries.
After these VISCREEN outputs are displayed, the analyst is asked whether
additional calculations are to be made with changed emissions, distances,
and so on. Unless the analyst is interested in evaluating the effect of
alternative emissions or siting distances, additional VISCREEN analyses
will not be needed for Level-1 screening.
The summary and results files, with filenames as entered by the user when
VISCREEN was invoked, are written to the disk as the program executes. If
multiple runs of VISCREEN are carried out (e.g., with changed emissions),
results for these runs are appended to the end of the files. The summary
32
-------
PLUME DELTA E AGAINST A SKY BACKGROUND
VIEW
no
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
Please
ANGLES (DEGREES)
phi
5.0
10.0
15.0
20.0
25.0
30.0
35.0
40.0
45.0
50.0
55.0
60.0
65.0
70.0
75.0
80.0
85.0
90.0
press
alpha
163.8
158.8
153.8
148.8
143.8
138.8
133.8
128.8
123.8
118.8
113.8
108.8
103.8
98.8
93.8
88.8
83.8
78.8
[ENTER]
ps1
.29
.42
.55
.66
.77
.87
.96
1.04
1.12
1.19
1.25
1.30
1.34
1.37
1.38
1.39
1.39
1.37
24
38
46
52
57
60
63
65
68
69
71
73
74
76
77
78
80
81
for more,
DIST
X
.9
.3
.8
.7
.2
.7
.5
.9
.0
.9
.6
.2
.6
.1
.4
.8
.2
.6
Q to
(KM) PLUME PERCEPTIBILITY DELTA E(
rp
55.8
43.1
35.3
30.1
26.4
23.7
21.6
20.0
18.8
17.8
17.1
16.5
16.1
15.8
15.6
15.6
15.7
15.9
quit
forward
2
3
4
5
5
5
5
5
5
5
5
5
5
5
4
4
4
4
.3
.7
.8
.3
.5
.7
.7
.6
.5
.4
.3
.2
.1
.0
.9
.8
.7
.6
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
backward
1.
1.
2.
2.
2.
2.
2.
2.
2.
2.
2.
2.
2.
2.
2.
2.
2.
2.
4
6
0
3 *
5 *
6 *
7 *
7 *
7 *
7 *
6 *
6 *
5 *
5 *
5 *
4 *
4 *
3 *
FIGURE 13. Sample VISCREEN AE output.
33
-------
-GREEN PLUME CONTRAST-
VIEW ANGLES DISTANCES (KM) forward backward screening
no phi alpha x rp ro contrast contrast criterion
Line of sight with maximum contrast for plume viewed
against a SKY background INSIDE class I area.
33 84.4 84.4 80.0 15.7 32.0 -.004 -.033 .05
Line of sight with maximum contrast for plume viewed
against a TERRAIN background INSIDE class I area.
33 84.4 84.4 80.0 15.7 32.0 .020 .011 .05
Line of sight with maximum contrast for plume viewed
against a SKY background OUTSIDE class I area.
2 10.0 158.8 38.3 43.1 57.0 -.008 -.064 * .05
Line of sight with maximum contrast for plume viewed
against a TERRAIN background OUTSIDE class I area.
2 10.0 158.8 38.3 43.1 57.0 .044 .038 .05
Absolute value exceeds screening criteria
FIGURE 14. Sample VISCREEN summary for lines of
sight with maximum plume contrast.
34
-------
PLUME CONTRAST AGAINST A SKY BACKGROUND
VIEW
no
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
ANGLES
phi
95.0
100.0
105.0
110.0
115.0
120.0
125.0
130.0
135.0
140.0
145.0
150.0
155.0
.1
84.4
148.2
alpha
73.8
68.8
63.8
58.8
53.8
48.8
43.8
38.8
33.8
28.8
23.8
18.8
13.8
168.6
84.4
20.6
DISTANCES (KM)
X
83.0
84.5
86.2
87.9
89.9
92.1
94.8
97.9
101.8
106.9
113.9
124.4
142.2
1.0
80.0
120.0
rp
16.3
16.7
17.4
18.3
19.4
20.8
22.6
24.9
28.1
32.4
38.8
48.6
65.7
79.0
15.7
44.4
ro
34.5
36.3
38.6
41.5
45.3
50.3
57.0
66.3
80.0
101.8
141.4
234.5
701.9
79.5
32.0
156.9
forward
contrast
-.004
-.004
-.004
-.004
-.004
-.004
-.004
-.003
-.003
-.003
-.003
-.002
-.001
.051
-.004
-.002
-GREEN PLUME CONTRAST-
backward screening
contrast criterion
When you're ready, please press [ENTER] for
more lines of sight (Q to quit)
-.032
-.032
-.032
-.031
-.031
-.031
-.030
-.029
-.028
-.026
-.023
-.018
-.011
-.037
-.033
-.020
.05
.05
.05
.05
.05
.05
.05
.05
.05
.05
.05
.05
.05
.11
.05
.05
FIGURE 15. Sample VISCREEN summary for all lines of sight.
35
-------
file is designed for inclusion in a report (e.g., a PSD permit applica-
tion) describing the results of the analysis. It contains all information
needed for a reviewing agency to duplicate the VISCREEN results, including
emissions, particle characteristics, meteorology, and geometry.
Obviously, reports prepared by the users of VISCREEN should include the
rationale for selecting these inputs, especially if non-default values are
chosen. The summary report automatically identifies Level-1 analyses by
their use of default values. Figure 16 shows an example of a Level-1 sum-
mary report.
The results file is not designed for inclusion in reports, but rather to
facilitate the user's preparation of additional graphics displays. Such
displays can be created by commercially available "spreadsheet" programs
and graphics packages, or by user-developed programs. For example, this
file can be used to plot plume AE as a function of viewing azimuth. As
described more fully in Appendix B, the results file includes all user
inputs, as well as VISCREEN-calculated values for plume-observer geometry
variables (e.g., downwind distance and plume thickness) and all optical
parameters for each line of sight. Optical parameters include contrast
values at three wavelengths (red, green, and blue), AE, and the applicable
screening criterion for each combination of line-of-sight, scattering
angle, and viewing background. The file is formatted with spaces separa-
ting variables, allowing it to be read into commercially available
"spreadsheet" programs. It also includes an entry showing the number of
lines-of-sight for which results are presented.* This entry can be read
as an index limit by programs written in FORTRAN or other languages.
This is necessary for scenarios in which the user specifies a
relatively large observer-source-terrain angle, causing VISCREEN to
calculate results for fewer than the normal 34 lines-of-sight.
36
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Visual Effects Screening Analysis for
Source: Public Electric Coal 13
Class I Area: Longview NP
***
Input Emissions for
Level-1 Screening
Particulates
NOx (as N02)
Primary N02
Soot
Primary S04
10.00 G /S
120.00 G /S
.00 G /S
.00 G /S
.00 G /S
**** Default Particle Characteristics Assumed ***
Transport Scenario Specifications:
Background Ozone:
Background Visual Range:
Source-Observer Distance:
M1n. Source-Class I Distance:
Max. Source-Class I Distance:
Plume-Source-Observer Angle:
Stability: 6
Wind Speed: 1.00 m/s
.04 ppm
110.00 km
80.00 km
80.00 km
120.00 km
11.25 degrees
RESULTS
Asterisks (*) Indicate plume Impacts that exceed screening criteria
Maximum Visual Impacts INSIDE Class I Area
Screening Criteria ARE Exceeded
Delta E Contrast
Backgrnd Theta Az1 Distance Alpha Crit Plume Crit Plume
SKY
SKY
TERRAIN
TERRAIN
10.
140.
10.
140.
84.
84.
84.
84.
80
80
80
80
.0
.0
.0
.0
84.
84.
84.
84.
2
2
2
2
.00
.00
.00
.00
4
2
1
.743*
.369*
.495
.593
.05
.05
.05
.05
-.004
-.033
.020
.011
Maximum Visual Impacts OUTSIDE Class I Area
Screening Criteria ARE Exceeded
Delta E Contrast
Backgrnd Theta Azi Distance Alpha Crit Plume Crit Plume
SKY
SKY
TERRAIN
TERRAIN
10.
140.
10.
140.
35.
35.
5.
5.
63
63
24
24
.5
.5
.9
.9
134.
134.
164.
164.
2
2
2
2
.00
.00
.00
.00
5.
2.
3.
1.
657*
662*
406*
197
.05
.05
.05
.05
-.006
-.048
.043
.040
FIGURE 16. Sample Level-1 summary report.
37
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LEVEL-2 SCREENING
As shown 1n Figure 1, Level-2 plume visual impact screening is done if the
Level-1 results exceed the screening criteria. The objective of Level-2
screening is identical to that of Level-1—the estimation of worst-day
plume visual impacts—but in Level-2 screening more realistic (less con-
servative) input, representative of the given source and the Class I area,
is provided. This situation-specific input may include particle size
distributions for plume and background that are different from those used
in the default Level-1 analysis. Median background visual range based on
on-site measurements rather than the map shown in Figure 9 might be
used. However, the most important potential difference in input between
Level-1 and Level-2 analysis centers on meteorology and plume transport
and dispersion patterns. While the Level-1 analysis assumes F stability,
a 1 m/s wind speed, and a wind direction that would carry plume material
very close to the observer, in the Level-2 analysis, meteorological data
and the topography representative of the source area and the Class I area
may suggest that worst-case plume dispersion conditions are different.
SELECTING PARTICLE SIZE DISTRIBUTIONS
If the Level-1 default parameters are selected, VISCREEN assigns best
estimates of particle size and density for the emitted and background
atmosphere particulate (see Table 2). However, some situations may not
be adequately characterized by the default particle size and density
parameters. In such cases, Level-2 screening should be carried out with
different parameters.
For example, the Level-1 screening default for background fine particles
assumes a mass median diameter of 0.3 ym; however, in certain humid areas,
the background fine particulate mode may be larger (0.5 urn), and in cer-
tain dry desert areas, such as the southwestern United States, the fine
mode may be smaller (0.2 pm). If the analyst has measurements of
background particle size distributions and densities that are different
from default parameters, these site-specific values should be used and
documented.
-------
TABLE 2. Default particle size and density
specifications. (Source: Seigneur et al.t
1983)
Particle Type
Background fine
Background coarse
Plume parti cu late
Plume soot
Plume primary sulfate
Mass Median
Diameter (urn)
0.3
6
2
0.1
0.5
Density
(g/cm3)
1.5
2.5
2.5
2
1.5
40
-------
Also, 1f information regarding the size distribution of emitted particu-
late is available, this data should be used to specify emitted particulate
sizes and densities. In many cases, particulate emission rate estimates
for a source will be calculated from emission factors that do not specifi-
cally identify the expected size distribution. In such cases the default
primary particle size distribution should be used. If more detailed
information on actual size distributions is available, appropriate non-
default values should be used in Level-2 analyses. In general, larger
particles (greater than 10 pm in diameter) have relatively small
effects. Thus, if both PM-10 and TSP emission rates are available, it
will usually be appropriate to use the PM-10 rate for primary particle
emissions. However, if the TSP emission rate is substantially higher than
that for PM-10, the large particle effects may be appreciable. In this
case the TSP rate should be used, along with appropriate size distribution
parameters.
Another alternative exists if there are two distinct processes contribu-
ting to primary particle emissions (e.g., fuel combustion emissions from a
boiler and fugitive dust from materials handling), and if there are no
primary sulfate emissions from the source. In such cases the primary sul-
fate emission input can be used for one of the processes, with appropriate
modification to particle density and size distribution inputs. If this
approach is used, the data and rationale for each input to the Level-2
analysis should be thoroughly documented by the analyst, and reviewed with
the permitting agency and Federal Land Manager.
DETERMINING WORST-CASE PLUME DISPERSION CONDITIONS
Probably the most important input specification for Level-2 screening
analysis is for meteorological conditions: the worst-case wind direction
and speed and atmospheric stability. Therefore, the joint frequency dis-
tribution of these parameters as measured at or near the location of the
emission source or the Class I area is important input for Level-2 plume
visual impact screening.
It is essential to consider the persistence as well as the frequency of
occurrence of these conditions. For example, plume discoloration will
generally be most intense during light-wind, stable conditions. However,
the transport time to a Class I area increases as the wind speed
decreases. As the transport time approaches 24 hours, it is increasingly
probable that the plume will be broken up by convective mixing and by
changes in wind direction and speed; thus it will not be visible as a
plume or a discolored layer.
41
-------
Ideally, one would prefer to have a meteorological data base with detailed
spatial and temporal coverage. However, this is rarely possible because
of cost considerations. Several alternative approaches can be used to
fill in missing data, but they all involve making assumptions. For
example, if a complete meteorological data base is available only at the
site of the proposed emissions source, one might assume that conditions at
the site are representative of conditions at other locations in the
region. However, in regions of complex terrain, this assumption may not
be appropriate. Often, data collected at ground level are assumed to
represent conditions at the effective stack height, which is a poor
assumption when the plume is several hundred meters above ground or the
site is located in complex terrain.
Any assessment of plume visual impacts is limited by the availability,
representativeness, and quality of meteorological data. The Level-1
screening analysis discussed in the previous section does not require the
user to input any meteorological data; rather, conservative assumptions
are made regarding worst-case stability, wind speed, and wind direction.
The Level-2 screening analysis assumes that the analyst has at least one
year of meteorological data from the site of the proposed emissions
source, a nearby site within the region, or the Class I area(s) poten-
tially affected by emissions. For a detailed discussion of the meteoro-
logical data input requirements, refer to the EPA Guidelines on Air
Quality Models (Revised) (1986) and Supplement A (1987) [EPA 450/2-78-
027R].
The meteorological data base discussed previously should be used to
prepare tables of joint frequency of occurrence of wind speed, wind
direction, and stability class similar to those shown in Figure 17. These
tables should be stratified by time of day. If meteorological data are
available at hourly intervals, it is suggested that these tables be
stratified as follows: 0001-0600, 0601-1200, 1201-1800, and 1801-2400.
If data are available twice daily, morning and afternoon data should be
tabulated separately. With this stratification, diurnal variation in
winds and stability is more easily discernible. If meteorological data
are not available, the assumptions regarding meteorology used in the
Level-1 analysis are used to assess impact.
On the basis of maps showing the source, observer location, and topo-
graphy, the analyst should select the wind direction sector that would
transport emissions closest to a given class I area observer point so that
the frequency of occurrence of impact can be assessed as discussed
below. For example, in the schematic diagram shown in Figure 18, west
winds would transport emissions closest to observer A, whereas either
west-southwest or west winds would transport emissions closest to observer
B. Observer C would be affected by emissions transported by west-
northwest and northwest winds, but primarily by west-northwest winds.
-------
•MORNING HOURS ONLY (0001-0600); OTHER SETS
OF TABLES FOR OTHER TIMES OF DAY
B
•»
/
1
c
0
^M
U
10 Total
N
NNE
NE
ENE
E
ESE
£E
SSE
S
ssw
sw
wsw
w
WNW
NW
NNW
Total
MP.
^
m^m
FIGURE 17. Joint frequency distribution tables required to estimate worst-case
meteorological conditions for plume visual impact.
43
-------
EMISSIONS
SOURCE
FIGURE 18. Schematic diagram showing emissions source, observer
locations, and wind direction sectors.
44
-------
For situations influenced by complex terrain, determination of this worst-
case wind direction and its frequency of occurrence is much more diffi-
cult. The analyst should use professional judgment in this determina-
tion. In such situations, determination of the worst-case wind direction
and its frequency of occurrence should be made on the basis of the follow-
ing factors:
Location(s) for which meteorological data were collected relative to
terrain features, emissions source, and potentially affected class I
areas.
Likely plume trajectories for each wind direction (and possibly wind
speed and stability) based on either data or professional judgment.
For example, potential channeling, convergence, and divergence of
flows should be assessed (see Figure 19).
The next step is to construct a table (see the example in Table 3) that
shows worst-case dispersion conditions ranked in order of decreasing
severity and the frequency of occurrence of these conditions associated
with the wind direction that could transport emissions toward the class I
area. Dispersion conditions are ranked by evaluating the product azu,
where oz is the Pasquill-Gifford vertical diffusion coefficient for the
given stability class and downwind distance x along the stable plume tra-
jectory identified earlier, and u is the maximum wind speed for the given
wind speed category in the joint frequency table. The dispersion condi-
tions are then ranked in ascending order of the value ozu. This is illus-
trated in Table 3. The downwind distance in this hypothetical case is
assumed to be 100 km. Note that F,l (stability class F associated with
wind speed class 0-1 m/s) is the worst dispersion condition, since it has
the smallest value of azu (90 m/s). The second worst diffusion condition
in this example is E,l, followed by F,2, F,3, and so on.
The next column in Table 3 shows the transport time along the minimum tra-
jectory distance from the emissions source to the Class I area, based on
the midpoint value of wind speed for the given wind speed category. For
example, for the wind speed category, 0-1 m/s, a wind speed of 0.5 m/s
should be used to evaluate transport time; for 1-2 m/s, 1.5 m/s; and so
on. The times necessary for a plume parcel to be transported 100 km are
56, 19, 11, 8, and 6 hours for wind speeds of 0.5, 1.5, 2.5, 3.5, and 4.5
m/s, respectively.
For the Level-2 screening analysis, we assume it is unlikely that steady-
state plume conditions will persist for more than 12 hours. Thus, if a
transit time of more than 12 hours is required to transport a plume parcel
from the emissions source to a Class I area for a given dispersion condi-
tion, we assume that plume material is more dispersed than a standard
45
-------
BOUNDARIES OF
16 CARDINAL WIND
DIRECTION
SECTORS
ELEVATED TERRAIN
SHOWN IN SHADED
FIGURE 19. Example of map showing emissions source, elevated
areas, and stable plume trajectories.
46
-------
TABLE 3. Example table showing worst-case meteorological conditions for plume
visual impact calculations.
Disperson
Condition
(stability,
wind speed)
F.I
E,l
F.2
F.3
E,2
F.4
D,l
E.3
E.4
az U
(m2/s)
90
175
180
270
350
360
430
525
700
Transport
Time
(hours)
56*
56*
19*
11
19*
8
56*
11
8
Frequency of Occurrence of
Given Dispersion Condition
Associated with Worst-Case
Wind Direction^ for Given
Time of Day (percent)
0-6
0.2
0.3
0.2
0.2
0.4
0.3
0.0
0.1
0.5
6-12
0.1
0.2
0.1
0.2
0.3
0.2
0.2
0.1
0.3
12-18
0.0
0.1
0.0
0.0
0.0
0.0
0.5
0.0
0.1
18-24
0.2
0.2
0.2
0.2
0.2
0.2
0.1
0.1
0.3
Frequency and
Cumulative
Frequency
(percent)
f
0.0
0.0
0.0
0.2
0.0
0.3
0.0
0.1
0.5
cf
0.0
0.0
0.0
0.2
0.2
0.5
0.5
0.6
1.1
* Transport times to Class I areas during these conditions are longer than
12 hours, so they are not added to the cumulative frequency summation.
* For a given Class I area.
Note: Distance downwind, values of o7, and transport times are based on X
min
47
-------
Gaussian plume model would predict. This enhanced dilution would result
from daytime convective mixing and wind direction and speed changes.
To obtain the worst-case meteorological conditions, it is necessary to
determine the dispersion condition (a given wind speed and stability class
associated with the wind direction that would transport emissions toward
the Class I area) that has a ozu product with a cumulative probability of
1 percent. In other words, the dispersion condition is selected such that
the sum of all frequencies of occurrence of conditions worse than this
condition totals 1 percent (i.e., about four days per year). The 1-per-
centile meteorology is assumed to be indicative of worst-day plume visual
impacts when the probability of worst-case meteorological conditions is
coupled with the probability of other factors being ideal for maximizing
plume visual impacts. Dispersion conditions associated with transport
times of more than 12 hours are not considered in this cumulative fre-
quency for the reasons stated above.
This process is illustrated by the example shown in Table 3, which indi-
cates that the first three dispersion conditions would cause maximum plume
visual impacts because the ozu products are lowest for these three condi-
tions. However, the transport time from the emissions source to the Class
I area associated with each of these dispersion conditions is greater than
12 hours. With the fourth dispersion condition (F,3), emissions could be
transported in less than 12 hours. The frequency of occurrence (f) of
this condition is added to the cumulative frequency summation (cf). For
this hypothetical example, the meteorological data are stratified into
four time-of-day categories. The maximum of each of the four frequencies
is used to assess the cumulative frequency. This is appropriate since we
are concerned with the number of days during which, at any time, disper-
sion conditions are worse than or equal to a given value.
Note that the worst-case, stable, light-wind dispersion conditions occur
more frequently during the nighttime hours.* In our example, the fol-
* Although plume visual impact is usually not an issue at night, night-
time dispersion conditions need to be considered because maximum plume
visual impacts are often observed in the morning after a period of
nighttime transport. For these situations, the nighttime meteorological
conditions are most indicative of plume dispersion when the plume is
viewed at sunrise. In cooler seasons, stable stagnant conditions may
persist during daytime hours
48
-------
lowing additional worst-case dispersion conditions add to the cumulative
frequency: F,4; E,3; and E,4. Dispersion conditions with wind speeds
less than 2 m/s (F,l; E,l; F,2; E,2; and D,l) were not considered to cause
an impact because of the long transit times to the Class I area in this
example. Thus, their frequencies of occurrence were not added to the
cumulative frequency summation. The result of this example analysis is
that dispersion condition E,4 is associated with a cumulative frequency of
1 percent, so we would use this dispersion condition to evaluate worst-
case visual impacts for the Level-2 screening analysis for this example
case.
It should also be noted that if the location of the observer in the Class
I area is at or near the boundary of one of the 16 cardinal wind direction
sectors, it may be appropriate to interpolate the joint frequencies of
wind speed, wind direction, and stability class from the two wind direc-
tion sectors, on the basis of the azimuth orientation of the observer
relative to the center of the wind direction sectors.
ACCOUNTING FOR COMPLEX TERRAIN
If the observer is located on elevated terrain or if elevated terrain is
between the emissions source and the observer, dispersion patterns may be
significantly different from those obtained from the procedures outlined
above. For such situations, adjustments to the worst-case meteorological
conditions determined by these procedures may be necessary.
For example, consider the elevated terrain feature illustrated by the
shaded area in Figure 16. It is unlikely that a stable plume parcel would
remain intact after transport to either Observer A or B. Either the
stable plume would be transported around the elevated terrain feature,
resulting in a longer plume transport distance, or the plume would be
broken up by turbulence encountered during the straight-line transport up
and over the terrain feature. Also, stable plume transport in the direc-
tion of Observer C would be blocked by elevated terrain. On the other
hand, Observer D would be in a position where straight-line stable trans-
port is not only possible but very likely in the drainage flow off the
elevated terrain feature.
Accounting for elevated terrain can be a detailed and time-consuming pro-
cess, requiring complex-terrain windfield models and other sophisticated
tools. Although such analytical options are encouraged, we suggest a
simpler screening approach based on assumed enhancements to dispersion
caused by elevated terrain.
49
-------
If the observer is located on terrain at least 500 meters above the
effective stack height for stable conditions (Observer C in Figure
16) or such elevated terrain separates the emission source and the
observer (Observers A and B in Figure 16), the worst-case stability
class should be shifted one category less stable.
EXERCISING VISCREEN
The plume visual impact screening model VISCREEN can be run as described
previously for the Level-1 analysis. However, for Level-2 analysis, the
default parameters are not selected. The analyst selects particle size
distribution and density parameters suitable for the source and region in
question (although default particle sizes and densities can still be used
if desired). Meteorological conditions (stability, wind speed,, and plume
offset angle) appropriate for the worst-case analysis are used. If
available, visual range and ambient ozone data from locations near the
source area and Class I area can be used instead of Level-1 default
values. Median values of both should be used, if available.
ALTERNATIVE USE OF PLUME VISIBILITY MODELS
As an alternative to the use of the screening model VISCREEN, the analyst
may wish to apply plume visibility models (refer to EPA Guideline on Air
Quality Models (Revised) EPA 450/2-78-027R, Supplement A, and any future
supplements]. Although model input requirements are more extensive for
these more sophisticated models, the models are expected to be more real-
istic (less conservative) than VISCREEN. Several alternative plume and
sun positions should be tested to assure that realistic worst-case scat-
tering angles are analyzed (VISCREEN analyses only worst-case scattering
angles).
50
-------
LEVEL-3 ANALYSIS
In Level-3 analysis, the objective is broadened from conservative analysis
of worst-case conditions to a realistic analysis of all conditions that
would be expected to occur in a typical year in the region that includes
both the emission source and the observer. Level-3 analysis is no longer
considered screening because it is a comprehensive analysis of the magni-
tude and frequency of occurrence of plume visual impacts as observed at a
sensitive Class I area vista.
It is important to determine the frequency of occurrence of visual impact
because the adversity or significance of impact is dependent on how fre-
quently an impact of a given magnitude occurs. For example, if a plume is
perceptible from a Class I area a third of the time, the impact would be
considered much more significant than if it were perceptible only one day
per year. The assessment of frequency of occurrence of impact should be
an integral part of Level-3 visual impact analysis.
OBJECTIVES OF LEVEL-3 ANALYSIS
In this section we discuss how one can determine both the magnitude and
frequency of occurrence of plume visual impact. This procedure entails
making several runs with a plume visibility model for different values of
the following important input parameters that are likely to vary over the
course of a typical year:
Emission rates (if variable)
Wind speed
Wind direction
Atmospheric stability
Mixing depth
Background ozone concentration
Background visual range
Time of day and season
Orientation of observer, plume, and sun
51
-------
Viewing background (whether it is sky, cloud, or snow-covered, sun-
lit, or shaded terrain).
Because of the large number of variables important to a visual impact cal-
culation, several model calculations are needed to assess the magnitude
and frequency of occurrence of visual impact. It would be ideal to calcu-
late hourly impacts over the course of a year or more using hourly values
of the above variables. However, such an extensive data base is rarely
available for use. Even if it were available, the computing costs
involved would be prohibitive. It is therefore preferable to select a few
representative, discrete values for each of these variables to represent
the range (i.e., the magnitude and frequency of occurrence) of visual
impact over a given period of time, such as a season or year.
It is possible to imagine a worst-case impact condition that would never
occur in the real atmosphere; this condition could be represented on a
cumulative frequency plot, such as that of Figure 20, as point A. The
impact is great, but it almost never occurs. If another worse-case situa-
tion less extreme than point A were selected, the magnitude of impact
would be less, but it might occur with some nonzero frequency, about one
day per year, for example (the reasonable worst-case impacts for Level-1
and Level-2 analyses). It is possible to select various values of all the
important input variables and to assess the frequency with which those
conditions resulting in impacts worse than a given impact would occur. By
this process, several points necessary to specify the frequency distribu-
tion could be obtained (for example, points B, C, and D in Figure 17).
With average (50-percentile) conditions, a negligible impact, as shown at
point E in Figure 17, might be found. In Figure 17, the ordinate could be
any of the parameters used to characterize visibility impairment, such as
visual range reduction, plume contrast, blue-red ratio, or &E, and the
abscissa could represent cumulative frequency over a season or a year.
In a visual impact assessment, it is recommended that one select various
combinations of upper-air wind speed, wind direction, and atmospheric sta-
bility; background ozone concentration; and background visual range to
specify the frequency distribution of plume visual impact as shown in
Figure 17. If one has a large, concurrent data base of all five of these
variables, it would be desirable to calculate a five-way joint-probability
distribution matrix and to use these joint probabilities to calculate fre-
quency of occurrence of impact. However, in most situations, such a data
base is not available, and one must treat the various worst-case events as
independent probabilities. With this assumption, the probability of
worst-case impacts can be roughly estimated by multiplying the independent
probabilities. This can be represented as follows:
-------
I
25 50 75
Cumulative Frequency of Occurrence (3»)
100
FIGURE 20. Example of a frequency distribution of
plume visual impact.
53
-------
f(y > y1) =
)
(10)
where f(y > y1) is the cumulative frequency of impact y greater than y1,
and f(x^ > x.j') is the cumulative frequency of variable x^ having values
that would cause greater impact than the value x^'.
In such an application, one might obtain an estimate of cumulative fre-
quency by using the joint frequency distribution of upper-air wind speed
and wind direction and the separate frequency distributions of upper-air
stability and other parameters critical to plume visual impact. For
example, a cumulative frequency distribution of the plume perceptibility
parameter AE can be estimated as follows:
where
f(AE > AE') = f(u < u1, WD < WD1) • f(s > s')
• f (other factors)
(U)
f(AE > AE1) = the frequency of occurrence of AE values
greater than AE1. AE1 is calculated on the
basis of a wind speed u', wind direction WD1,
stability s1, ozone concentration [O^]', and
visual range ry'.
f(u < u', WD < WD1) = the frequency of occurrence of wind speeds
less than u1 for wind directions within a
specified value (WD') of the worst-case wind
direction.
f(s > s')
f(other factors)
the frequency of occurrence of stabilities
greater than s1.
the frequency of occurrence of background
ozone concentrations greater than [0-t]' (that
would cause higher plume N0£ concentrations),
background visual range values greater than ry',
and plume dimensions (oy, oz) worse than assumed
values (Pasquill-Gifford).
Note that this equation assumes the statistical independence of winds,
stability, and other factors. If enough data are available, joint
frequency distributions should be used. This is especially important if
there are known conditions that contradict the assumption of independence
(e.g., terrain-induced stable drainage that flows). Each of the input
54
-------
parameters that are important to the visibility model calculation varies
significantly over the period of a year.
SUGGESTIONS FOR LEVEL-3 ANALYSIS
The most exacting way to obtain plume visual impact cumulative frequency
distributions would be to apply a plume visibility model for every time
period (e.g., every daylight hour or 3-hour period) with the appropriate
emissions, wind speed, wind direction, stability, background ozone, back-
ground visual range, sun angle, and viewing background. Thus, one would
have a calculation for every daytime period in the course of a year. If
done every 3 hours, this would be approximately 1460 model applications
(365 days/yr X 12 hr/day of daylight/3 hr = 1460 time periods). Such a
method is not practical with current plume visual impact analysis hardware
and software.
Thus, the analyst needs to estimate the plume visual impact cumulative
frequency distribution using a limited set of plume visibility model runs
and appropriate assumptions. There is no simple procedure that can be
recommended for all Level-3 analyses. Limited comparisons of Level-3 pre-
dictions with measurements suggest that magnitudes and frequencies of
plume visual impact are reasonably well estimated by the following sug-
gested procedures. It is recommended, however, that any chosen procedures
for performing a given Level-3 analysis be reviewed by the permitting
authority and the Federal Land Manager of the affected Class I area before
analysis commences.
Frequency Distribution of Dispersion Conditions
A joint frequency distribution of wind speed, wind direction, and sta-
bility should be prepared separately for the following times of day: mid-
night to 0600, 0600 to noon, noon to 1800, and 1800 to midnight. This
breakdown is necessary to identify the time of day of impacts. These dis-
tributions should be compiled for the entire year (or if possible, two or
more years) and for each of the four seasons. Seasonal analysis of plume
visual impact may be important for the Federal Land Manager and state to
assess the number of visitors potentially impacted by a given plume. If
worst-case plume visual impacts occur under stable transport conditions,
they will most likely occur during the early morning hours. In such
cases, it is recommended that the midnight to 0600 frequency distributions
be given the primary attention in Level-3 analysis. However, for com-
pleteness, the 0600 to noon and noon to 1800 distributions should be used
to characterize the frequency of midday and afternoon plume visual
impacts.
55
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Calculating Plume Visual Impacts
Plume visual impacts should be calculated for a representative sample (or
possibly each) of the the categories of stability, wind speed, and wind
direction in the joint frequency distribution. Since the objective is to
estimate the cumulative frequency curve (similar to that shown in Figure
19), plume visual impact should be calculated for the most distant plume
position (from the observer) within the given wind direction and the
highest wind speed appropriate for a given category of the distribution.
For example, for the frequency distribution cell representing F, 0-1 m/s,
plume calculations should be made for 1 m/s, not a lower value, and for
the most distant plume position (11.25° offset is recommended for the
worst-case wind direction sector). This approach is necessary because the
abscissa of the cumulative frequency plot is the frequency of conditions
that produce impacts larger than the ordinate value of plume visual impact
magnitude (AE). Plume visual impact should be calculated for a number of
the cells of the frequency distribution (perhaps 20 or more). The largest
impact magnitudes are likely to occur for wind directions that would carry
the plume closest to the observer, light wind speeds, and stable condi-
tions. To fill in conditions causing lower magnitudes (but higher
cumulative frequencies), the analyst should identify a sample of wind
directions, wind speeds, and stabilities that represent typical con-
ditions. For example, all the 72 combinations of 8 plume positions or
wind directions (e.g., worst case and three adjacent 22.5° sectors to the
left and right, representing plume offset angles of 11.25, 33.75, 56.25,
and 78.75°, 3 wind speeds (e.g., 0-2, 2-5, and 5-10 m/s), and 3 stabili-
ties (e.g., F, E, and D) could be used as the input for 72 plume visi-
bility model runs. These runs would be made using median background ozone
concentration and visual range values. Sun angles would be specified by
the date and time of the simulation. The worst-case sun angles should be
determined by sensitivity analysis for one of the worst-case combinations
of meteorological conditions before the full complement of model runs (72
in our example above) is made. Since worst-case meteorological conditions
generally occur in the morning, it is suggested that simulation date/times
of an hour after sunrise and an hour before sunset on 21 March, 21 June,
21 September, and 21 December be analyzed in the sensitivity test, and the
worst-case date/time be used for all subsequent model runs. Model runs
should be made for the appropriate viewing backgrounds for each line of
sight and each plume position. If terrain is found to be the plume's
viewing background, the appropriate distance between the observer and the
terrain feature should be provided as part of the model input.
56
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Coupling Magnitude and Frequency
Each of the (for example, 72) model calculations should be evaluated to
select the two maximum plume AE's for conditions when the plume parcel is
inside and outside the Class I area's boundary, respectively. (If discus-
sions with the Federal Land Manager of the given Class I area suggest that
only within-area plume parcels are of concern, only the former AE need be
compiled.) The inside and outside AE's separately should be put in
descending order of magnitude and coupled with the corresponding frequency
of dispersion conditions. Cumulative frequencies should be added by sum-
ming the individual frequencies (see Table 3). If a wind direction, sta-
bility, or wind speed class was skipped in the sampling of the cells in
the frequency distribution, the frequencies for all conditions expected to
cause greater plume visual impact should be added and coupled with the
given plume visual impact AE. Separate magnitude/frequency tables should
be compiled for inside/outside views, each time of day, and each season.
Interpreting the Cumulative Frequency Curve
Cumulative frequency distribution curves of plume visual impacts prepared
using the procedures described in the preceding paragraphs should be
interpreted in light of the assumptions and simplifications underlying the
various steps. Several factors that can be particularly significant
include the use of median values for visual range and background ozone
concentration; the persistence of stable conditions for long transport
distances; and the use of Pasquill-Gifford coefficients as the sole
determinant of plume dispersion. For specific cases, the combined effect
of such assumptions can be that estimated frequencies of a specific level
of effects (say, AE greater than 5) may be higher or lower than would
actually occur.
Cumulative frequency curves based solely on the joint frequency of wind
speed, wind direction, and atmospheric stability ignore the probability of
occurrence of other factors that affect plume visual impacts. This proba-
bility appears as "f(other factors)" in Equation 11. In our experience,
wind speed, direction and stability are the principal determinants of
plume visual impacts. In some cases, however, these "other factors" could
be significant. Obviously, if data and resources allow, analyses can be
expanded to incorporate joint frequency distributions for all key para-
meters. However, the number of model simulations required will increase
geometrically with the addition of each new dimension. For example,
treating three visual ranges (e.g., 50th, 75th, and 90th percent!les)
triples the number of simulations. Further, the data required to develop
such joint frequency distributions are not available for many areas.
57
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No explicit formal guidance can be provided at this time for interpreting
cumulative frequency curves. The analyst should, however, identify which
transport scenarios have both high visual effects and high frequencies of
occurrence. Similarly, the analyst should verify that the transport
scenarios modeled include those under which visual impacts will be
greatest. If it is likely that simplifying assumptions may have led to
bias in the cumulative frequency curves, then the factors leading to this
conclusion should be described for consideration by the permitting agency,
the Federal Land Manager, and other reviewers.
Summarizing Results
Cumulative frequency plots similar to Figure 17 should be made for each
season, time of day, and inside/outside combination. In addition, the
number of mornings and afternoons in each season that AE's are greater
than 2 should be tabulated.
Optional Use of VISCREEN
As a low-cost, easy-to-apply, but more conservative estimate of plume
visual impact, the analyst may wish to use VISCREEN as the model for
generating plume visual impact magnitudes in the Level-3 analysis.
VISCREEN could be used either in place of, or in addition to, a plume
visibility model. VISCREEN can also be used to choose meteorological
scenarios to be further analyzed with a plume visibility model.
50
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REFERENCES
Blackwell, H. R. 1946. Contrast thresholds of the human eye. J. Optical
Society of America. 36:624-643.
Booker, R. L., and C. A. Douglas. 1977. "Visual Range Concepts in
Instrumental Determination and Aviation Application." NBS monograph
159, U.S. Department of Commerce.
Cornsweet, T. 1970. Visual Perception. Academic Press, New York.
Faugeras, 0. D. 1979. Digital color image processing within the frame-
work of a human visual model. IEEE Trans. Acoust., Speech Sig. Pro-
cess, Vol. ASSP-27, pp. 380-393.
Gordon, J. I. 1979. "Daytime Visibility: A Conceptual Review." Scripps
Institution of Oceanography, Visibility Laboratory, La Jolla, Cali-
fornia.
Hall, C. F., and E. L. Hall. 1977. A nonlinear model for the spatial
characteristics of the human visual system. IEEE Trans. Syst.. Man,
Cybern.. SMC-7, pp. 161-170.
Henry, R. C. 1979. "The Human Observer and Visibility—Modern Psycho-
physics Applied to Visibility Degradation. View on Visibility—Regu-
latory and Scientific." Air Pollution Control Association, Pitts-
burgh, Pennsylvania.
Henry, R. C., and J. F. Collins. 1982. "Visibility Indices: A Critical
Review and New Directions." Prepared for Western Energy Supply and
Transmission Associates. Environmental Research & Technology, Inc.,
Westlake Village, California (ERT Document P-A771).
Howell, E. R., and R. F. Hess. 1978. The functional area for summation
to threshold for sinusoidal gratings. Vision Res.. 18:369-374.
Jaeckel, S. M. 1973. Utility of color-difference formulas for match
acceptability decisions. Appl. Optics. 12:1299-1316.
59
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Johnson, R. W. 1981. Daytime visibility and nephelometer measurements
related to its determination. Atmos. Environ., 16:1835-1846.
Judd, D. B., and G. Wyszecki. 1975. Color in Business, Science, and
Industry. John Wiley & Sons, New York.
Koenig, A., and E. Brodhun. 1888, 1889. Experimentelle Untersuchungen
uber die psychophysische Fundamental forme1 in Bezug auf den Gesichts-
sinn. Sitzungssberichte preussischen Akademie der Wissenschafteji,
26:917-931; 27:641-644.
Latimer, D. A., and R. G. Ireson. 1980. Workbook for Estimating Visi-
bility Impairment. U.S. Environmental Protection Agency, Research
Triangle Park, North Carolina (EPA-450/4-80-031).
Latimer, D. A., R. W. Bergstrom, S. R. Hayes, M. K. Liu, J. H. Seinfeld,
G. Z. Whitten, M. A. Wojcik, and M. J. Hillyer. 1978. "The
Development of Mathematical Models for the Prediction of Anthropo-
genic Visibility Impairment." U.S. Environmental Protection Agency,
Research Triangle Park, North Carolina (EPA-4503-78-110a,b,c).
Loomis, R. J., M. J. Kiphart, D. B. Garnand, W. C. Malm, and J,. V.
Molenar. 1985. "Human Perception of Visibility Impairment." Paper
presented at the Annual Meeting of the Air Pollution Control Associa-
tion, Detroit, Michigan, June 1985.
Lowry, E. M. 1931. The photometric sensibility of the eye and the pre-
cision of photometric observations. J. Optical Society of America,
21:132.
Lowry, E. M. 1951. The luminance discrimination of the human eye.
Journal of the Society of Motion Picture and Television Engineers,
57:87.
Malm, W., M. Kleine, and K. Kelley. 1980. "Human Perception of Visual
Air Quality (Layered Haze)." Paper presented at the 1980 Conference
on Visibility at the Grand Canyon.
Malm, W. C., D. M. Ross, R. Loomis, J. Molenar, and H. Iyer. 1986. "An
Examination of the Ability of Various Physical Indicators to Predict
Perception Thresholds of Plumes as a Function of Their Size and
Shape." Paper presented at the Air Pollution Control Association
International Specialty Conference on Visibility, Grand Teton
National Park, September 7-10, 1986.
60
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Mathai, C. V., and I. H. Tombach. 1985. Assessment of the technical
basis regarding regional haze and visibility impairment. AeroViron-
ment Inc., Monrovia, California (AV-FR-84/520).
Middleton, W.E.K. 1952. Vision Through the Atmosphere. University of
Toronto Press, Toronto, Canada.
Optical Society of America, Committee on Colorimetry. 1963. "The Science
of Color." Optical Society of America, Washington, D.C.
Seigneur, C. et al. 1983 "User's Manual for the Plume Visibility Model
(PLUVUE II)." Systems Applications, Inc., San Rafael, California
(SYSAPP-83/221)
Stevens, R. K., T. G. Dzubay, C. W. Lewis, and R. W. Shaw. 1984. Source
apportionment methods applied to the determination of the origin of
ambient aerosols that affect visibility in forested areas. Atmos.
Environ.. 18:261-272.
Systems Applications, Inc. 1985. "Modeling Regional Haze in the
Southwest: A Preliminary Assessment of Source Contribution."
Systems Applications, Inc., San Rafael, California (SYSAPP-85/038).
Tombach, I., and D. Allard. 1980. Intercomparison of visibility measure-
ment methods. J. Air Pollut. Control Assoc., 30:134-142.
Tombach, I., and D. Allard. 1983. "Comparison of Visibility Measurement
Techniques: Eastern United States." Electric Power Research Insti-
tute, Palo Alto, California (EPRI EA-3292).
61
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Appendix A
PERCEPTIBILITY THRESHOLDS AND RECOMMENDED SCREENING
ANALYSIS CRITERIA FOR PLUMES AND HAZE LAYERS
-------
Appendix A
PERCEPTIBILITY THRESHOLDS AND RECOMMENDED SCREENING
ANALYSIS CRITERIA FOR PLUMES AND HAZE LAYERS
INTRODUCTION
The plume from an emissions source is visible to an observer if the con-
stituents of the plume, such as particulates and nitrogen dioxide, scatter
or absorb enough light out of or into the observer's line of sight so that
the plume contrasts with its viewing background. If this plume contrast
is sufficiently large (either positively, signifying a bright plume, or
negatively, signifying a dark plume), the plume becomes perceptible.
Thus, the objective of plume visibility Impact analysis is first to deter-
mine the plume contrast and second to determine whether that contrast will
be perceptible. Some plumes are not visible because the concentration of
optically active species in the plume (I.e., those that scatter or absorb
light) 1s low. In addition, other factors, such as the position of the
plume relative to the observer and the nature of the haze through which
the plume 1s viewed, can affect plume visibility.
The objective of this appendix 1s to review the literature regarding per-
ceptibility thresholds in order to recommend criteria for use in plume
visibility impact screening and analysis. A perceptibility threshold
would be a suitable criterion for visibility impact analysis if the policy
objective were to be very strict (I.e., to prevent any visible plumes in a
given location). A perceptibility threshold also may help to define the
lower bound for less strict criteria (that would prevent significant plume
impacts but allow a few days of marginally perceptible plumes).
PERCEPTIBILITY PARAMETERS
Contrast is the parameter most commonly used in the published literature
to describe the sensitivity of the human eye-brain system. Contrast is
also the most easily calculated plume visibility parameter, since it can
be based on a single wavelength of light and does not require calculations
at other wavelengths in the visible spectrum as do more sophisticated
parameters.
A-l
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Contrast is the relative difference in light intensity (radiance) of two
viewed objects and can be calculated as follows:
I, - I,
c--v
where 1^ and l^ are the light intensities at a given wavelength for
objects 1 and 2 (e.g., a plume and its viewing background).
Another parameter commonly used in plume visual impact analysis is AE. t
is perhaps the best currently available plume perceptibility parameter
because it is based on the human eye/brain system's relative sensitivity
to all wavelengths in the visible spectrum. It is proportional to the
perceptibility of color differences and is essentially identical to just
noticeable differences (jnd). A AE value of 1 is commonly taken to be
1 jnd.
OVERVIEW OF THRESHOLD RESEARCH
The issue of defining the conditions under which a plume or haze layer
will be visible is part of the scientific field known as psychophysics.
Psychophysics is the branch of psychology that is concerned with subjec-
tive measurement. It relates physical stimuli to psychological response.
In the current context, we are interested in the effect that differences
in radiant energy (light) directed toward a human observer (the physical
stimulus) have on the psychological response of the eye/brain system of
the observer.
One of the oldest psychophysical determinations is the minimum physical
stimulus increment that the observer can just barely perceive. This
increment is called the just noticeable difference, differential thres-
hold, or difference limen. A just noticeable contrast is also called a
liminal contrast, and contrasts greater or less than this contrast are
called supraliminal and subliminal. The difference limen is never a
sharply defined value. Since an observer's sensitivity and attention vary
from moment to moment, it is common to define the limen as a statistical
measure. For example, the limen might be defined as that stimulus that
could be distinguished 50, 70, or 90 percent of the time. The difference
limen is often set at a value of 70 percent probability of distinguishing
two stimuli. One of the oldest laws of psychophysics is Weber's Law,
which states that the difference limen is a constant fraction of the
stimulus. Since contrast is defined as the relative difference in light
intensities of two objects and is itself a ratio, Weber's Law could be
A-2
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stated as follows: the Uminal contrast is a constant (regardless of the
light intensity). Later research has shown that Weber's Law is only
approximate.
The famous Koschmieder equation that inversely relates the visual range to
the light extinction coefficient was based on the assumption that the
liminal contrast for relatively large, sharp-edged objects observed in
daylight is 0.02, or 2 percent. Although there were no scientific data to
support this assumption made by Koschmieder in 1924, this contrast value
is widely used in visibility work for uniformity in discussion.
One of the largest research studies of liminal contrast was carried out by
Blackwell (1946). In this study, 19 young female observers made more than
2,000,000 observations, of which 450,000 were suitable for statistical
analysis (Middleton, 1952). Circular stimuli of various sizes ranging
from 0.6 to 360 minutes of arc were presented to the observers. These
studies indicated that for a typical daytime luminance of 100 candle/m ,
the liminal, or threshold, contrast ranges from a low of 0.003 (or 0.3
percent) for stimuli subtending 121 minutes of arc (2°) viewed for unlimi-
ted times to contrasts as high as 0.02 (or 2 percent) for stimuli subtend-
ing 10 minutes of arc viewed for limited periods. Thus, Blackwell's data
suggest that the human observer is more sensitive than Koschmieder assumed
him to be, at least under laboratory conditions.
The data of Koenig and Brodhun (1888, 1889) suggest that for typical day-
light luminances, the Uminal contrast is independent of the wavelength of
light over the range tested (0.43 to 0.67 urn) and is on the order of 0.01,
or 1 percent. For luminances greater than about 100 candles/m , Lowry
(1931, 1951) reported a liminal contrast of 0.014, or 1.4 percent.
Recent psychophysical research (Cornsweet, 1970; Hall and Hall, 1977;
Faugeras, 1979; Howell and Hess, 1978; Malm et al., 1986) has documented
the fact that the response of the human eye/brain system to brightness
contrast is a strong function of the spatial frequency of the contrast.
Spatial frequency is defined as the reciprocal of the distance between
sine-wave crests (or troughs) measured in degrees of angular subtense of a
sine-wave grating. Thus, spatial frequency has units of cycles/degree
(cpd). Any pattern of light intensities, whether it is a sine-wave,
square-wave, step-function or any other pattern, can be resolved by
Fourier analysis into a sum of sine-wave curves of different magnitude and
frequency. To a first approximation, the spatial frequencies (f) corre-
sponding to a Gaussian plume of width (w) are within the order of magni-
tude centered on f = 1/w. The human eye/brain system is most sensitive
to spatial frequencies of approximately 3 cycles/degree (cpd). Thus, we
might expect that plumes of width 0.33° (inverse of 3 cpd) to be the most
easily perceptible. Figure A-l summarizes the research of Howell and Hess
A-3
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Contrast
OJ
3
CT
OJ
(O
03
Q.
O
c
O
c
3
rt3
to
m
to
OJ
>
i_
3
O
>>
4->
>
to
IT3
-4->
C
O
C3
A-4
-------
(1978). The sensitivity of the human eye-brain system drops off signifi-
cantly at high spatial frequency (due to visual acuity) and also to a less
extent at low spatial frequency (i.e., broad, diffus objects). The human
visual system is much more sensitive to images with sharp, distinct edges
(e.g., square waves) than to images with diffuse, indistinct edges (e.g.,
sine waves or Gaussian plumes). At 3 cpd the human visual system has a
sensitivity* to square waves of 300 (corresponding to a threshold contrast
of 2/300, or 0.0066) and to sine waves of 230 (contrast of 0.0086). Thus,
at this most sensitive frequency, the eye/brain system is 1.3 times more
sensitive to square waves than to sine waves. At lower spatial frequen-
cies, the difference in sensitivities increases significantly (see Figure
A-l). The fall-off in sensitivity at high spatial frequencies is con-
sistent with the data of Blackwell (1946) and with the known responses of
lens systems such as the human eye (Cornsweet, 1970).
To this point, we have discussed perception threshold research that is
based on the use of contrast as the quantitative parameter. Before pro-
ceeding to the research of Malm and co-workers that specifically addresses
the perception thresholds of plumes and haze layers, we discuss the limi-
ted work that has been performed using the AE parameter. The AE parameter
is designed to be proportional to the perceptibility of differences in
brightness and color (Judd and Wyszecki, 1975). It is generally accepted
that a AE of 1 corresponds to 1 just-noticeable difference (jnd). Thus, a
AE of 1 is roughly the liminal, or threshold, color difference. Applying
the AE formulas to a 2 percent contrast, Latimer et al. (1978) calculated
a AE of 0.78 and concluded that "AE's less than 1 would be imper-
ceptible." Jaeckel (1973) presented data on the probability that obser-
vers would accept given color differences as a match. He found that
approximately 30 percent of observers could distinguish a AE of about 1,
50 percent could distinguish a AE of 2, and more than 90 percent could
distinguish a AE of 4.
Essentially all of the work specifically addressed to the perception
threshold of plumes and layered haze has been carried out by Malm and co-
workers at Colorado State University. Their laboratory studies were based
on actual or computer-generated color slides of plumes and layered haze.
* Howell and Hess (1978) define sensitivity as the inverse of modulation
contrast which is (Ij - \2)/(l\ + l^>" This definition of contrast is
approximately half the contrast defined earlier (Ij - I2)/I2- Thus, we
multiply modulation contrast by two to obtain contrasts used for visi-
bility.
A-5
-------
Malm, Kleine, and Kelley (1980) studied the perception threshold for com-
puter-generated white and N02 Gaussian plumes. The response to white and
N02 plumes resulted in essentially identical contrasts. Fifty percent of
the observers were able to identify a plume with a contrast of 0.014 and
AE of 2.3, 75 percent a contrast of 0.020 and AE of 3.3, and 90 percent a
contrast of 0.025 and AE of 4.1.
The most detailed study to date of plume perceptibility thresholds is the
work of Malm et al. (1986). In this study sharp-edged (square wave)
plumes were generated by computer and overlaid on color slides of a
natural scene. Plumes of various contrasts and sizes (ranging from 0.1 to
3° wide) were shown to observers. These researchers found that the detec-
tion thresholds for such computer-generated square-wave plumes were a
relatively strong function of the vertical plume width. The highest
visual sensitivity was found for 0.36° plumes, which is consistent with
the previously noted maximum sensitivity at a spatial frequency of 3 cycles
/degree. Maximum sensitivity was 200 (corresponding to a contrast of
0.005) for the 0.36° plume, and sensitivities for all size plumes were
approximately 100 or greater (contrasts of 0.01 or smaller). These thres-
holds were defined at the 70 percent probability of detection point. This
threshold contrast of 0.005 is consistent with the threshold contrast of
0.007 of Howell and Hess (1978).
Table A-l summarizes the research described previously. Under laboratory
conditions in which observers are attentive and trained, the detection
threshold (for 50 percent detection) for objects of optimum size with dis-
tinct edges is in the range 0.003-0.007. For conditions in which the
stimulus has a diffuse edge (such as would be the case with a Gaussian
plume) or is different from the optimum-sensitivity size, threshold con-
trasts appear to be higher, approximately 0.009. The evidence for AE
thresholds is not as clear-cut. The data of Jaeckel (1973) and Malm,
Kleine, and Kelley (1980) support 70 percent detection thresholds for AE
of 3, while the estimates of Latimer et al. (1978) and the more recent
data of Malm et al. (1986) suggest a AE threshold of less than one.
It is instructive to consider the relationship between contrast (which has
been used in most perception research) and AE. For monochromatic con-
trasts (those involving brightness change, but not color change):
thus
* *
Aa = Ab =0
AE(L*a*b*) = l(Aa*)2 + (Ab*)2 + (AL*)2] AL*
A-6
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TABLE A-l. Summary of contrast and color change threshold data.
Contrast
0.003*
0.014
0.007*
0.009*
0.0165
—
—
—
__
0.006
0.009
0.014
0.020
0.025
0.01
0.005**
0.010++
-* —
Delta E
—
—
—
1
2
3
4
1.0
1.5
2.3
3.3
4.2
—
—
1.2
Percent
Detection
50
?
?
?
?
30
50
70
90
10
25
50
75
90
90
70
70
100
Edge Reference
Sharp Blackwell (1946)
Sharp Lowry (1931, 1951)
Sharp Howell and Hess (1978)
Diffuse
Sharp
Sharp Jaeckel (1973)
Sharp
Sharp
Sharp
Diffuse (Malm, Kleine, Kelley (1980)
Diffuse
Diffuse
Diffuse
Diffuse
Sharp Loomis et al. (1985)
Sharp Malm et al. (1986)
Sharp
Sharp
* The most sensitive contrast reported for largest size of stimulus and
largest luminance and longest response time evaluated (probably the
minimum possible threshold).
* The most sensitive contrast reported at a spatial frequency of 3
cycles/degree.
* Threshold contrast for sharp objects at low spatial frequencies.
** Minimum threshold for 0.36° wide plumes.
** Maximum threshold for all size plumes tested.
A-7
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since
/Y \1/3
L* = 116 l-\ - 16 , and
* -1/3 1/3
4L •
i
J •
If Y1 = (1 + C)Y ,
AL* = 116/f-j [(1 + C)1/3 - 1]
where
AE(L*a*b*) = color difference parameter
AL* = change in perceived brightness
V, Y, YQ = Y tristimulus values for an object (e.g., a plume), a
viewing background, and a white reference, respectively
C = contrast between observed object (e.g., a plume) and its
viewing background
For bright viewing backgrounds (Y = 100), this formula yields the follow-
ing approximate formula;*
AE = 36 C
Thus, the laboratory-derived threshold contrast of 0.009 for diffuse-edged
objects is the equivalent AE of 0.34. The "traditional" (Koschmieder)
threshold contrast of 0.02 is the equivalent AE of 0.76. Conversely, the
"traditional" just-noticeable-difference AE of 1 is the same as a contrast
of 0.026.
* This relationship assumes a bright viewing background and object. A
smaller AE would result for darker viewed objects. This finding is
consistent with the psychophysical experimental evidence that suggests
that higher contrasts are required between two dark objects for them to
be discerned.
\-&
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RECOMMENDATIONS FOR PLUME SCREENING CRITERIA
The concept underlying the use of screening analyses, such as Level-1 and
Level-2, is that for some facilities whose emission rates are sufficiently
low, or that are located far enough away from sensitive areas, it may be
possible to use relatively simple calculations to determine that plume
visual effects will be negligible. In this way, complex and costly
analytical approaches will only be required for those cases in which they
are needed to determine whether visual impacts are unacceptable. Per-
ceptibility thresholds establish a lower bound for Level-1 and Level-2
screening criteria. If, under transport and viewing conditions that con-
servatively describe "reasonable worst case" scenarios, 1t can be shown
that a plume's visual effects are below the threshold of perceptibility,
there is clearly no need to conduct more sophisticated analyses.
As noted in the preceding paragraphs, the perceptibility of an object
(e.g., a plume) may depend on both the observer and the viewing condi-
tions. Under controlled conditions, trained observers looking for
specific objects having sharp edges may have "ower perception thresholds
than do casual observers in natural conditions.
The literature suggests that the perceptibility threshold for trained and
attentive observers in a laboratory environment is on the order of 0.3-0.7
percent contrast and a AE of 0.1-0.3. In the natural environment, the
observer is likely to be much less sensitive to contrast and color differ-
ences because he or she 1s not specifically "looking for plumes and haze
layers." Thus, the use of laboratory-derived estimates of perceptibility
thresholds as screening criteria would be unnecessarily conservative.
Henry (Henry, 1979; Henry and Collins, 1982; Henry, private communication,
1987) suggests that the field threshold may be 2 to 4 times greater than
the laboratory threshold. Although this speculation is not based on
empirical evidence, it 1s consistent with our experience with "prevailing
visibility" measurements. For example, airport visibility observations
appear to correlate best with light extinction measurements when a con-
trast threshold of 5 percent 1s assumed 1n the Koschmieder equation (Gor-
don, 1979; Tombach and Allard, 1983). In their review of regional haze,
Mathai and Tombach (1985) make the following observation:
Laboratory and field experiments of the same sort gave simi-
lar results, but most field data suggest a higher contrast
threshold than do laboratory data, most probably because the
attention and target search conditions differ. Field experi-
ments during World War II have suggested a threshold contrast
of about 0.05 to be more appropriate for ordinary viewing,
and additional recent research (Booker and Douglass, 1977;
A-9
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Johnson, 1981; Tombach and Allard, 1980 and 1983; Stevens et
al., 1984) further support[s] the conclusion that a value
near 0.05 1s more representative of normal viewing than the
traditional 0.02 [contrast threshold used in the Koschmieder
equation]. Simply explained, for normal casual viewing of
nonspecific scenic features, the perception threshold is
greater than it is when a specific target is being sought in
earnest with a relatively long time or a known distinctive
form available to identify it.
Laboratory thresholds appear to underestimate actual thresholds for the
casual observer (e.g., a visitor to a national park or wilderness area who
is not specifically searching for plumes or haze layers). The above-
suggested threshold contrast of 0.05 is an order-of-magnitude larger than
the laboratory-derived threshold contrast of 0.005. For bright viewing
objects, a contrast of 0.05 translates to a AE of approximately 2.
On the other hand, if we use the factor of 4 recommended by Henry (Henry
and Collins, 1982; Henry, personal communication, 1987) to relate labora-
tory conditions to field conditions, the above-mentioned thresholds
derived for the laboratory convert to the following values for field
observation: a contrast of - 0.02 and a AE of - 0.8. These values may be
construed as the approximate "best estimate" thresholds of percepti-
bility. We emphasize that these values are estimates of the percepti-
bility threshold for the casual observer in the field; a sensitive obser-
ver may be able to detect plumes having much lower contrasts (0.003-0.007)
and lower A£ (0.1-0.3).
In summary, we suggest that the following values characterize our current
understanding of perceptibility:
Contrast aE
Lower-bound threshold
(sensitive observer in laboratory) 0.005 0.2
Best-estimate threshold
(sensitive observer in field) 0.02 0.8
Upper-bound threshold
(casual observer in field) 0.05 2
Figure A-2 synthesizes the results of this review of perceptibility thres-
holds. The abscissa (x-axis) shows the vertical width (angular subtense)
of a plume. The ordinate (y-axis) is the just-perceptible contrast. The
A-10
-------
1.0
0.1
0.01
0.001
Howell and Hess (1978) data:
Square-wave gratings (sharp edge)
Sine-wave gratings (diffuse edge)
Upper bound (screening criterion)
Perceptibility
"Threshold"
Data of Malm et al.
(1986) for sharp-
edged plumes
0.1 1.0
Plume Vertical Angular Subtense* (°)
10
FIGURE A-2. Plume perceptibility threshold as a function of plume
thickness (f). See definition of f in the Glossary in the front of this
workbook and in Figure 3.
A-ll
-------
two curves show the data of Howell and Hess (1978) for sharp and diffuse
edged objects, and the circles show the data of Malm et al. (1986) for
sharp-edged plumes. These two separate and Independent experiments are
remarkably consistent, indicating that plumes of approximately 0.3-0.5
degree vertical angular width are most easily perceptible. Diffuse-edged
objects have larger perceptibility thresholds than sharp-edged objects.
The diffuse-edged curve derived from Howell and Hess (1978) data is taken
to be the lower bound of perceptibility for plumes. The "best estimate"
and "upper bound" are also shown for comparison. For very thin plumes
(< 0.1° width) and very wide plumes (> 5° width) the Howell and Hess
(1978) data are assumed to define the threshold.
For Levels 1 and 2 plume visual impact screening, we recommend that the
higher set of threshold values (contrast of 0.05; AE of 2) be used as the
criteria for screening. For very wide or narrow plumes the Howell and
Hess (1978) diffuse-edge thresholds should be taken as the criteria for
screening (see Figure A-2).
A-12
-------
Appendix B
THE PLUME VISUAL IMPACT SCREENING MODEL (VISCREEN)
-------
Appendix B
THE PLUME VISUAL IMPACT SCREENING MODEL (VISCREEN)*
The plume visual Impact screening model (VISCREEN) was designed to provide
the user with a simple, easy-to-use analytical tool for performing Level-1
and -2 screening calculations of potential plume visual impacts,
especially in PSD Class I areas where visibility is a protected value.
VISCREEN is a simple plume visibility model. The objective of the model
is to calculate the contrast and the color difference of a plume and its
viewing background. Because VISCREEN is to be used for screening calcula-
tions, it was designed to be conservative (i.e., to overpredict potential
plume visual impacts). Therefore, VISCREEN calculates larger plume visual
impacts, for the same input specifications, than do more sophisticated
models such as PLUVUE and PLUVUE II.
VISCREEN is designed to operate on the simplest and most modestly equipped
IBM PC or compatible. It will operate with 256K memory. It will utilize
a math coprocessor, 1f Installed, with substantial improvement in execu-
tion speed. VISCREEN 1s coded 1n FORTRAN 77. A listing of the source
code 1s presented 1n Appendix D. Figure B-l schematically illustrates the
logic flow of VISCREEN. Each of the major calculation steps in VISCREEN
1s described, in succession, in the following sections.
INPUT
Because VISCREEN 1s designed to be straightforward, the input requirements
have been scaled down to the minimum necessary to describe the variety of
emissions, meteorological and background conditions, and the plume/
observer geometries an analyst is likely to encounter in Level-1 and -2
plume visual impact screening. Input 1s requested by screen prompts.
* See Latimer et al. (1978) and Latimer and Ireson (1980) for derivations
of many of the VISCREEN descriptions and algorithms.
B-l
-------
Emissions
Distances between
emission source and
observer and Class I
area boundaries
Visual range
Particle size, density
Meteorology
I Input I"
"^
Determine
line-of-sight
geometries
Calculate background
atmosphere's
optical properties
I
Calculate plume size,
concentration, NO2
formation, and optical
thickness
Calculate plume
contrasts and
radiances for sky
and terrain viewing
backgrounds
Calculate plume AE
values for sky and
terrain viewing
backgrounds
Determine whether
plume contrast or AE
values exceed the
screening criteria
Display screening
summary and AE's
and contrasts for
worst-case or all
lines of sight
Write summary
and output files
Yes
No
f Stop J
Subroutine
SZPAS
Subroutine
CHROMA
FIGURE B-l. Logic flow diagram of the plume visual Impact
screening model (VISCREEN).
B-2
-------
VISCREEN first requests names for two disk files that will be created.
The summary file presents an abbreviated summary of inputs and screening
results. The results file contains all inputs used in the analysis, as
well as geometry, AE, and contrast calculations for each line of sight and
wavelength. This file is designed to allow its use as input to user-
developed graphics routines or commercially available spreadsheet pro-
grams.
The second set of inputs describes the emissions. The user is given a
choice of units to input mass emission rates of various species that are
likely to cause visual effects. The units of these emission rates are
mass per unit time. Mass can be specified in metric units (grams, kilo-
grams, metric tonnes) or in English units (pounds or tons). Time can be
specified in seconds, minutes, hours, days, or years. The emission rate,
whatever the units used, should be the maximum short-term (i.e., hour)
emission rate likely to occur in the course of operation of the emission
source. The emissions that almost all analyses will consider are particu-
lates and nitrogen oxides (NOX); however, VISCREEN will also allow the
user to input such.species as (1) primary nitrogen dioxide (NC^) if this
species is directly emitted by the given chemical process, (2) primary
sulfate (SO^) if this species is directly emitted or if a second particle
size mode needs to be specified, and (3) elemental carbon (soot) if the
emission source is a diesel engine or other source with incomplete combus-
tion. However, for the vast majority of commonly encountered emission
sources involving either fugitive emissions or combustion emissions, the
analyst would only have to input particulate and NOX emissions.
The third set of inputs contains the distances that characterize the view-
ing situation. The first is the distance between the emission source and
the observer. The next two are the distances along the plume centerline
from the emission source to the closest and most distant Class I area
boundaries. Finally, the background visual range distance is specified.
The next set of inputs is requested only if the user indicates that the
default specifications built into VISCREEN (see Table B-l) are not
acceptable for a given screening analysis. These include the particle
size and density for the emitted particulate and primary sulfate and for
background fine and coarse particulate, the background ozone concentration
(used to calculate NO to N02 conversion in the plume), wind speed, atmo-
spheric stability class, and the offset angle between the plume centerline
and the line between the emission source and the observer. For Level-1
analyses, the default parameters would be used, and none of the above
inputs would need to be specified. In most Level-2 analyses the default
particle size and density specifications would be acceptable; only the
meteorological input specifications would have to be changed from the
Level-1 default values.
B-3
-------
TABLE B-l. Default specification for VISCREEN.
Particle Specifications
Mass Median
Type Diameter D (pro)
Background fine
Background coarse
Plume par ticu late
Plume sulfate
Plume soot
0.3
6
2
0.5
0.1
Density
P(g/cm3)
1.5
2.5
2.5
1.5
2
Wind speed = 1 m/s
Stability = F
Background [03] = 0.04 ppm
Plume offset angle y = 11.25°
B-4
-------
VISCREEN summarizes the inputs after specification and allows the user to
correct mistakes before proceeding. If necessary, emission rates are con-
verted to grams per second.
GEOMETRY OF PLUME, OBSERVER, CLASS I AREA,
VIEWING BACKGROUND, AND LINES OF SIGHT
The next section of VISCREEN computes the angles and distances that
describe a variety of lines of sight relevant to the given situation.
Figure 7 (in the main text) illustrates the set of lines of sight and geo-
metries for a typical Level-1 and -2 screening calculation. Figure B-2
summarizes the angles and distances that describe a single line of
sight. The plume is always assumed to be 22.5° wide, and the viewing
background is always assumed to be adjacent to the plume on the side of
the plume centerline opposite the observer. VISCREEN computes plume
visual impacts for lines of sight at 5° increments for the azimuthal
angle and for lines of sight corresponding to distance x (along the
plume centerline) of 1 kilometer, and xmi-n and xmax (the distances along
the plume centerline from the emission source to the closest and most dis-
tant Class I area boundaries). The angle a and the distances rp and rQ are
needed for all subsequent plume visual impact calculations. These
parameters can be solved for by noting the following relationships that
hold for all triangles: (1) the sum of the three interior angles equals
180° and (2) the ratio of the length of a triangle leg to the sine of the
opposite angle is equal for all three legs of the triangle.
For the lines of sight where $ is known, angle a can be solved directly as
follows:
a = 180° -
Since
For lines of sight where x is known, angle $ must be calculated as
follows:
B-5
-------
Emission
Source
Viewing Background
Observer.
22.5
Wide Plume
FIGURE B-2. Distances and angles that specify a given line or sight.
B-6
-------
«, = tan-l x sin r
d - x cos
Similar calculations are used to determine the distance rQ.
The plume offset angle y is set to be equal to 11.25° for all Level-1
screening calculations, and most Level-2 screening analyses will be per-
formed for such a plume offset. VISCREEN can be run for any arbitrary
offset angle between 0 and 180°; however, angles less than 11.25° and
greater than 168.75° are not recommended because these plume positions,
which are extremely rare, result in lines of sight along the plume axis
that are not calculated with precision using the assumptions coded in
VISCREEN.
OPTICAL PROPERTIES OF THE BACKGROUND ATMOSPHERE
The optical properties of the background atmosphere are then calculated
for each of the three wavelengths used in VISCREEN: 0.45, 0.55, and 0.65
ym. These optical properties include the extinction coefficient and the
phase function for the forward and backward scatter sun angles assumed in
the screening process. Sun angles are defined by the scattering angle 0,
which is the angle between the line of sight and the direct solar beam.
VISCREEN uses two scattering angles—10 and 140°~to calculate potential
plume visual impacts for cases where plumes are likely to be brightest
(0 = 10°) and darkest (0 = 140°). Figure B-3 and Table B-2 show typical
phase functions for these two worst-case sun angles for typical size dis-
tributions. The differences between phase functions for given particle
size distributions and pure air (Rayleigh scattering) are greatest in for-
ward scatter (10° is a reasonable estimate of a worst-case bright plume
situation) and in back scatter (140° is a reasonable estimate of a worst-
case dark plume situation).
The scattering coefficient caused by particles is determined by subtract-
ing the Rayleigh scattering coefficient:
bsp(x = 0.55 urn) = bscat(x = 0.55) - bR(x = 0.55)
where bR(x = 0.55 um) = 11.62 x 10'V1.
On the basis of the data of Whitby and Sverdrup (1978) and calculations of
Latimer et al. (1978), the fraction of bsp caused by coarse particles is
assumed to be 0.33. Thus, we have
B-7
-------
0 = 10°, forward
scatter situation
used in VISCREEN
——0.1 urn
(RAYLEIGH
SCATTER)
.;• = 140C, back scatter
situation used in
VISCREEN
PHASE FUNCTIONS AT X =0.55
ARE SHOWN FOR PARTICLE SIZE DIS-
TRIBUTIONS WITH INDICATED MASS
MEDIAN DIAMETER (DG) AND GEO-
METRIC STANDARD DEVIATION (a = 2.0)
60 80 100 120
Scattering Angle e (degrees)
FIGURE B-3. Phase functions for various particle size distributions.
B-8
-------
UJ
LU
O
•o
I/I
I/I
c
o
V.
I/I
•o
Q.
CM
OQ
CO
O>
o
s-
Q.
d)
N
oo
X
II
CO
o
« ~ Q -
^^ ^O ^D ^O ^J} 00 ^O
Oj ir> <9-cvj«—••—ii—1<—1000
OOOOOOOOO
C O CO
•^ E
4J U
U CM
_«/! E(
CO «—i tO O
CMCVIi—••—IOOOOO
C 3.
-^
•t— Q
^J W
OOOO«—ICNJIOVOO
I/I (U
g
(O fO
B-9
-------
bsp-submicron = °-67 bsp »
bsp-coarse = ^-33 &Sp .
The phase function for each of the scattering components can now be
determined. Phase functions for the submicron and coarse background aero-
sols are specified in Table B-2.
The Rayleigh scattering phase function (for air) is a function of the
scattering angle 0, but it is independent of wavelength x and can be
approximated quite well by the following relationship:
p(0) = 0.75 [1 -i- (cos e)2]
The scattering coefficients at different wavelengths (i.e., x = 0.45 and
0.65 urn) can be determined from the relationship:
bsp(x) = bsp(x * 0.55 ' *
where values of n are given in Table B-2 for various particle size distri-
butions and n = 4.1 for Rayleigh scatter.
The average background atmosphere phase functions are calculated for each
wavelength x and scattering angle e as follows:
x'0) background
PLUME DISPERSION, N02 FORMATION, AND OPTICAL CONDITIONS
The plume is treated as a Gaussian distribution in the vertical and a uni-
form distribution in the horizontal over the width of the 22.5° sector.
The line of sight is always assumed to be horizontal in VISCREEN; thus,
optical thickness is calculated as follows:
X. y1\ V /. p< + VN09 M
•—* 1 11 2
Tplume
,9 -in
(ZTT) o U Sin a
B-10
-------
where the summation is over all particles (participate, SO^, and soot),
is the light extinction efficiency per unit aerosol volume, and
bext/M is the light extinction efficiency per unit mass of N02.
The amount of N02 in the plume is calculated by assuming that 10 percent
of initial NO ' " " ..... '
is converted to N02 via the reaction with
02 and the rest is
titrated with ambient 0-j. For conservatism, the solar photodissociation
of N0£ and the further reaction of N02 to form HNO^ (realistic assumptions
for stable plume conditions near sunrise) are ignored. In this conversion
the plume concentration of NOX is calculated as follows:
it x
(2ir)
o 4.
2 tan
(nr
N02 concentrations in the plume are calculated as follows:
h + [N02]p , if [NOX] > h
[M02] =<
[NOX] + [N02]p
if [NOX] < h
where
[N02]
h
[N02P]
[031
plume centerline N02 concentration,
0.1 [NOX] + [03],
primary (directly emitted) N02
background ozone concentration
The scattering efficiency for each particle size mode is taken from the
bscat/v shown *n Tab^e B-2. Scattering at different wavelengths is scaled
using the parameter n (also shown in Table B-2) as follows:
'scat
(x = 0.55
(0*55)
-n
B-ll
-------
The light absorption efficiency for NC^ was taken by averaging efficien-
cies centered on the three wavelengths (x = 0.45, 0.55, 0.65 urn) to obtain
the following light absorption efficiencies: 0.691, 0.144, and 0.015
m/g. The light absorption efficiency of soot was assumed to be 10 m^/g
for all wavelengths.
To avoid gross overestimates of plume optical thickness (and potential
division by zero) for small a's, the minimum a is assumed to be 5°. The
effect of limited persistence of worst-case stable meteorological condi-
tions is treated in VISCREEN by assuming that input stable dispersion con-
ditions (with stability categories of E and F) persist for a maximum of 12
hours. For plume parcels located in positions that would require longer
transport times, additional dispersion is assumed by increasing the wind
speed for the given plume parcel so that the transport time exactly equals
12 hours. This is a crude way of accounting for stable plume breakup
after long transport times. Plumes with stability classes of A, B, C, or
D are assumed to persist for all transport times including those greater
than 12 hours.
PLUME CONTRAST
The contrast of the plume against sky and black terrain viewing back-
grounds is calculated conservatively by considering single scattering and
ignoring multiple scattering (Latimer and Ireson, 1980) as follows:
Plume Contrast
'plume
plume
- 1
background
Reduction in Sky/Terrain Contrast Caused by Plume
r = exp(-bextr0)
where
pplume' ^background "
average phase functions for plume and back-
ground atmosphere, respectively, f) is a
function of x and 0,
B-12
-------
u> , = ratio of light scattering to light extinction
plume ,
r in plume
"background = 1 (assumin9 no absorption)
These contrast values are calculated for each wavelength (x = 0.45, 0.55,
and 0.65 urn) and each scattering angle (o = 10 and 140°).
Light intensities for later use in calculating the color difference
parameter A£ are calculated from the contrast values as follows:
The sky background light intensity for each scattering angle (e) and wave-
length of light (x) is calculated as follows:
FS(X) p(x, e)
rsky = 4l
where FS(X) is the radiant flux from the sun (see Glossary in front of
Workbook).
Similarly, a white reference is
* -- *— O •
o 2ir
The light intensity of the plume against the sky is (Latimer et al.,
1978):
plume-sky ~ ^ "*" plume^ sky
The light intensity of the terrain background (assumed to be black) viewed
at distance rQ is
terrain = ^ ' exP^bext ro> Lsky •
The light intensity of the plume viewed against the dark terrain viewing
background is then
plume terrain ~ terrain "*" r sky
B-13
-------
PLUME AE VALUES
The color difference parameter AE is calculated from the three light
intensities using the following equation:
AE(L*a*b*) = [(AL*)2 + (Aa*)2 + (Ab*)2J1/2
where
L* = 116 (Y/YQ)1/3 - 16,
/X \1/3
500I/)L*
x \ ' /Y ^
f - f
V \ a
X = I(x) x ,
Y = I(x) y ,
Z = I(x) 2 .
In these equations, the tristimulus values XQ, YQ, ZQ define the color of
the nominally white object-color stimulus from a perfectly diffuse reflec-
tor normal to the direct solar beam (IQ defined above). The AL*, Aa*, and
Ab* refer to the difference in these three functions between the plume and
its viewing background (either sky or terrain).
The three chromaticity tristimulus weighting functions x, y, and z were
determined for each of the wavelengths by averaging the values shown in
Figure B-4 over the wavelengths centered on x = 0.45, 0.55, and 0.65 urn.
These average weighting factors and other parameters used in VISCREEN are
summarized in Table B-3.
COMPARISON OF CALCULATIONS WITH SCREENING CRITERIA
The calculated contrast and AE values are compared to the default screen-
ing criteria described in Appendix A (i.e., AE = 2, contrast = 0.05, and
the Howell and Hess curve for diffuse-edge objects) or to user-specified
criteria. The vertical plume dimension for each line of sight is calcula-
ted using the following formula:
B-14
-------
400
500 600
Wavelength, x (nm)
Source: Judd and Wyszecki (1975).
FIGURE B-4. Weighting values x(x), y(x), z(x)
B-15
-------
TABLE B-3. Average chromaticity tristimulus weighting
functions, NC^ light absorption efficiency, and solar flux
used in VISCREEN.
Parameter
IT
y
"z
babs2- N0;
(watt m"2
Blue, 0.45 ym
(0.36-0.50 ym)
0.1196
0.0935
0.7012
,/M 0.691
1712
sr-1)
Wavelength x
Green, 0.55 ym
(0.51-0.60 ym)
0.6317
0.8229
0.0159
0.144
1730
Red, 0.65 ym
(0.61-0.74 ym)
0.1838
0.0753
0.0000
0.015
1414
B-16
-------
-1 ' °2
* « tan —-—-
P
This plume width is used with the diffuse-edge curve in Figure A-2 to
determine the minimum perceptible contrast. The green (x = 0.55 ym) plume
contrast for each scattering angle and viewing background is then compared
to this minimum perceptible contrast and the screening contrast threshold
of 0.05. A secondary test is made by comparing the plume AE with the
minimum perceptible A£ and the screening AE of 2. If the plume contrast
is greater than both contrast values, or the plume AE is greater than both
AE thresholds, the given line of sight fails the screening test. To find
the minimum perceptible AE, the equivalent AE is calculated for an object
having the minimum perceptible (Howell and Hess) contrast from the sky and
the terrain viewing backgrounds (see Appendix A). This approach is
believed to provide a conservative underestimate of threshold AE,
especially for dark terrain viewing backgrounds for which higher contrasts
may be needed to distinguish a plume.
OUTPUT
VISCREEN generates a summary file and a results file in addition to the
screen display during a user's sessions. The files store the inputs and
results to provide the user with a record of a run. The user is queried
by VISCREEN for the names of the files.
The summary file (see Figure 16) is designed to provide a concise, single-
page summary of the inputs and the results of a run. Only the user-
supplied inputs are provided; defaults are not printed to save space. The
results included in the summary file display maximum visual impacts inside
and outside of the Class I area, with any screening criteria exceedances
indicated. Format of the summary file is self-explanatory.
The results file contains all inputs and results that may be used for
other analyses. The format of the results file is designed to allow the
file to be imported into commercially available spreadsheet programs. In
this way, users can design their own tabular and graphical displays of
VISCREEN results. The content and output formats for the results file are
provided in Table B-4. There are three sections to the file. The first
section (records 1 through 11) contains the inputs for the run. Section
two (records 12 and 13+) contains the number of lines of sight (record 12,
included so that a user-developed program can know how many records of
information to read), followed by one record for each line of sight (LOS).
These LOS records include LOS geometry information, screening threshold,
and AE values. The final section is similar to the second, in that it
B-17
-------
Table B-4. Output format for the VISCREEN results file
Record
No. Contents
1 Source name
2 Class I area name
3 Mass unit
= 1 grams
= 2 kilograms
= 3 metric tonnes
= 4 pounds
= 5 tons
Time flag
= 1 seconds
= 2 minutes
= 3 hours
= 4 days
= 5 years
4 Particulate emission rate
NOx emission rate
N02 emission rate
Soot emission rate
S04 emission rate
5 Source-Observer distance
Min. Source-Class I distance
Max. Source-Class I distance
Background visual range
6 Default flag
- 1 used default value
= 0 user input value
Background Fine Particulate Density (g/cm3)
Background Fine Particulate Size index (urn)
= 1 0.1
= 2 0.2
= 3 0.3
= 4 0.5
= 5 1.0
= 6 2.0
= 7 5.0
= 8 6.0
= 9 10.0
Format
A
A
15
15
F10.3
F10. 3
F10. 3
F10.3
F10. 3
F10.3
F10.3
F10. 3
F10.3
15
F10.3
15
Default flag
Background Coarse Particulate density
Background Coarse Particulate size index
15
F10.3
15
B-18
-------
Table B-4 (concluded). Output format for the VISCREEN results file
Record
No. Contents Format
8Default flag15
Plume Partlculate density F10.3
Plume Partlculate size Index 15
9 Default flag 15
Plume Soot density F10.3
Plume Soot size index 15
10 Default flag 15
Plume Primary S04 density F10.3
Plume Primary S04 size index 15
11 Default flag 15
Background Ozone (ppm) F10.3
Wind speed (m/s) F10.3
Stability index 15
11A (Record not included in Level-1 runs)
Default flag, plume offset angle I5.F10.3
12 Number of lines of sight 15
13+ Line of sight (LOS) IX,12
LOS classification 12
= 0 outside Class I area
= 1 inside Class I area
Azimuthal angle F8.1
Angle between LOS and plume F7.1
Source-observed plume distance F7.1
Observer-observed plume distance F7.1
Observer-terrain distance behinde plume F7.1
PSI F5.2
Green Contrast threshold F7.3
Screening threshold and delta E for:
sky, forward scatter 2F7.2
sky, backward scatter 2F7.2
terrain, forward scatter 2F7.2
terrain, backward scatter 2F7.2
14 Number of lines of sight 15
15+ Line of sight number IX,12
LOS classification 12
Azimuthal angle F8.3
Green Contrast threshold F7.3
Green contrast for:
forward scatter, sky and terrain background 2F7.3
backward scatter, sky and terrain background 2F7.3
Blue contrast (as for green) 4F7.3
Red contrast (as for green) 4F7.3
Note: Records 13+ and 15+ are repeated for each line of sight.
B-19
-------
begins with the number of LOS's, and is followed by one record for each
LOS. These contain LOS identifiers, the green contrast screening
criterion, and green, blue and red contrast values for each line of sight
and viewing background. Figure B-5 shows an example of a complete results
file.
CONSERVATISM OF VISCREEN
VISCREEN is designed for use in Level-1 and -2 plume visual impact screen-
ing calculations. The objective of the screening exercise is to identify
emission sources that have the potential to cause adverse visibility
impairment. Because these sources can be analyzed further (with more
sophisticated models) in a more detailed manner (e.g., using Level-3
analysis), the screening model should yield output that is consistently
conservative. That is, it should calculate plume visual impacts that are
likely to be greater than those that would actually be encountered and
those that would be calculated in Level-3 analysis. This conservatism is
necessary to avoid approving an emission source that passes a screening
test, but could have problems that would be revealed by a more detailed
analysis. It also eliminates the need for facilities with negligible
effects to carry out more complicated and costly assessments.
VISCREEN was designed to be conservative by making the following model
assumptions:
1. It is assumed that the line of sight is horizontal so that it
intersects the most plume material. Nonhorizontal lines of
sight intersect less plume material because horizontal disper-
sion of plumes exceeds vertical dispersion, especially under
stable conditions.
2. N02 conversion is conservatively treated by assuming the plume
is uniformly mixed in the 22.5° sector. This enhanced disper-
sion mixes the plume with more ambient 0^, resulting in greater
conversion. However, the assumed enhanced dispersion does not
decrease the line-of-sight integral of plume material for the
assumed horizontal viewing conditions. Only the vertical
dimensions of the plume determine the magnitude of the plume
material that intersects the horizontal line of sight.
3. Worst-case sun (scattering) angles are assumed. The forward
scatter case (0 = 10°) yields very bright plumes because the
sun is placed nearly directly in front of the observer. This
geometry would rarely occur in reality. The backward scatter
case (0 = 140°) yields the darkest possible plumes. Thus, the
B-20
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-------
screening calculations are likely to yield the brightest and
darkest possible plumes. It is left to more detailed PLUVUE
modeling to identify realistic worst-case sun angles that would
occur at specific times of interest.
4. Multiple scattering is ignored in VISCREEN. Light scattered
into the line of sight from directions other than directly from
the sun tend to slightly decrease the plume contrast for the
worst-case sun angles assumed.
5. For terrain viewing backgrounds, the terrain is assumed to be
black (the darkest possible) and located as close to the obser-
ver and the plume as possible. This assumption yields the
darkest possible background against which particulate plumes are
likely to be most visible. In reality, terrain viewing back-
grounds (if indeed terrain is behind the plume) would be less
dark and would be located farther from the observer.
6. Meteorological conditions are assumed to persist for at least 12
hours. After 12 hours, some additional dispersion is assumed in
VISCREEN (by increased wind speeds), but the plume is still con-
sidered to remain intact. More realistic treatment of the per-
sistence of worst-case dispersion conditions would most likely
yield lower plume visual impacts.
7. Default meteorological conditions assumed for the most conserva-
tive Level-1 screening (F, 1 m/s, y = 11.25°) are extreme and
are expected to be more conservative than worst-case conditions
identified in the more realistic Level-2 and -3 analyses.
8. The screening threshold (AE = 2; contrast of 0.05) was selected
at the upper bound of the perceptibility threshold, representing
a reasonable estimate for casual observers in the field.
B-24
-------
Appendix C
EXAMPLES OF PLUME VISUAL-IMPACT SCREENING AND ANALYSIS
-------
Appendix C
EXAMPLES OF PLUME VISUAL-IMPACT SCREENING AND ANALYSIS
The objective of this appendix is to assist the reader in understanding
how specific screening and analyses might be carried out in different
situations and at different levels of analysis. The detailed instructions
provided in the text of this document are not repeated here. Rather, the
examples are accompanied by limited commentary so that the reader obtains
an overview of different plume visibility screening alternatives. Any
application of plume visual-impact screening and analysis technology will
differ depending on the circumstances of the given scenario.
This appendix provides examples of visibility screening and more detailed
analyses for six different scenarios:
LEVEL-1 AND LEVEL-2 SCREENING
1. The first example that was presented in Latimer and Ireson
(1980), a coal-fired power plant, for which Level-1 and -2
screening calculations were performed.
2. The second example that was presented in Latimer and Ireson
(1980), a cement plant, for which Level-1 and -2 screening cal-
culations were performed.
3. A paper mill located very close to a Class I area for which
Level-1 and -2 screening calculations were performed.
LEVEL-3 ANALYSIS
4. A large coal-fired power plant located 90 km from a western
national park, for which Level-1, -2, and -3 screening and
analyses were carried out.
C-l
-------
5. A very large coal-fired power plant close to three areas of con-
cern located in different directions from the plant, for which
Level-1, -2, and -3 screening and analysis were performed.
6. A very small emission source located extremely close to a
western Class I area, for which all three levels of screening
and analysis were performed.
EXAMPLE 1: COAL-FIRED POWER PLANT (1980 WORKBOOK EXAMPLE 1)
This example is based on a hypothetical coal-fired power plant proposed
for a site approximately 70 km from a Class I PSD area in Nevada. The
emissions rates for this hypothetical power plant are projected to be 25
g/s of participates, 380 g/s of nitrogen oxides (as N02), and 120 g/s of
sulfur dioxide. Figure C-l shows the relative locations of the proposed
site and the Class I area. The Federal Land Manager has identified the
view toward the mountains to the west as integral to the visitors'
experience of the Class I area.
For conservatism, the observer is placed on the boundary of the Class I
area closest to the power plant, which in this case is at the southwestern
corner of the Class I area. (Although more visitors would be located at
the visitors' center, the Federal Land Manager has stated that all
locations in the Class I area are of interest because of widespread visi-
tor use.) From measurements made off of a topographical map (see Figure
C-l), the distance from the proposed plant site to this closest corner is
70 km. Since the lines drawn at an 11.25° angle on both sides of the line
between the plant site and the nearest corner of the Class I area are out-
side the Class I area, the closest Class I area boundary is also selected
to be 70 km, for conservatism.
Exhibit C-l shows the results of the VISCREEN analysis for this example.
The source fails the Level-1 test with a maximum AE of 17.8, nearly nine
times the screening threshold. Its maximum contrast of -0.140 (for the
backward-scattering scenario) is nearly identical to the 1980 Workbook
Level-1 screening calculation of -0.146. The plume is also predicted to
be visible against terrain with a contrast of +0.107 (for the forward-
scattering scenario), a slightly higher value than the 0.0814 calculated
in the 1980 Workbook.
To characterize worst-case meteorological conditions for Level-2 screen-
ing, we obtained meteorological data from an airport 100 km west of the
proposed power plant. Although the intervening terrain is not flat, we
judged that the 850-mb wind and stability data are the best available data
source. For the trajectory passing to the northwest of the Class I area,
C-2
-------
O
O)
ce:
C-3
-------
Level-1 Screening
Input Emissions for
Participates 25.00 6 /S
NOx (as N02) 380.00 6 /S
Primary N02 .00 G /S
Soot .00 G /S
Primary S04 .00 G /S
Default Particle Characteristics Assumed
Transport Scenario Specifications:
Background Ozone:
Background Visual Range:
Source-Observer Distance:
Min. Source-Class I Distance:
Max. Source-Class I Distance:
Plume-Source-Observer Angle:
Stability: 6
Wind Speed: 1.00 m/s
.04 ppm
170.00 km
70.00 km
70.00 km
90.00 km
11.25 degrees
RESULTS
Asterisks (*) indicate plume impacts that exceed screening criteria
Maximum Visual Impacts INSIDE Class I Area
Screening Criteria ARE Exceeded
Delta E Contrast
Backgrnd Theta Azi Distance Alpha Crit Plume Cnt Plume
SKY 10.
SKY 140.
TERRAIN 10.
84.
84.
84.
70.0
70.0
70.0
84.
84.
84.
2.00 17.807*
2.00 10.828*
2.00 8.852*
.05 -.005
.05 -.140*
.05 .107*
TERRAIN 140. 84. 70.0 84. 2.00 4.004* .05 .041
Maximum Visual Impacts OUTSIDE Class I Area
Screening Criteria ARE Exceeded
Delta E Contrast
Backgrnd
SKY
SKY
TERRAIN
TERRAIN
Theta Azi Distance Alpha Crit
10.
140.
10.
140.
35.
35.
15.
15.
55
55
41
41
.6
.6
.0
.0
134.
134.
154.
154.
2
2
2
2
.00
.00
.00
.00
Plume
20.
11.
15.
4.
.370*
.101*
.827*
.791*
Crit
.05
.05
.05
.05
Plume
-.007
-.207*
.205*
.143*
EXHIBIT C-l. Level 1 screenina analysis for Example 1.
C-4
-------
we tabulated winds from the southwest and west-southwest for both morning
and afternoon soundings. From these tabulations, a frequency of occur-
rence (Table C-l) was developed. The cumulative frequency entries show
that on three to four days per year conditions with ozu values of 212 nr/s
(E stability, 2 m/s) can be expected. Note that the bulk of the contribu-
tion to the cumulative frequency (0.9 percent out of 1.0 percent) repre-
sents the 1200 GMT E,2 dispersion conditions. This corresponds to
approximately 5:00 a.m. LST. Note also that the afternoon sounding fre-
quency of E,2 dispersion conditions was relatively high (0.6 percent, or
about two days per year).
Exhibit C-2 summarizes the VISCREEN analysis using the meteorological con-
ditions of E and 2 m/s (less extreme than the Level-1 F and 1 m/s). The
maximum plume perceptibility for plume parcels located within the Class I
area occurs when the sun is in front of the observer (forward-scatter
conditions) and the plume is observed against the sky. For these condi-
tions, the plume AE is 8.9, about 4.5 times larger than the screening
threshold. Given the geometry shown in Figure C-l, the possibility could
not be ruled out that such a forward-scatter situation would occur. Even
if such a sun angle were not possible, the second test for a backward
scatter sun angle indicates that the plume would be quite visible,
exceeding both the AE and the green contrast screening thresholds. The
even larger impacts calculated for plume parcels outside the Class I area
are relevant in this example since they could occur within an identified
integral vista. The maximum green contrasts for the plume parcels located
outside the Class I area were 0.231 in forward scatter and -0.129 in back-
ward scatter. These values require careful interpretation, however, as
they are for the line of sight through a plume parcel only 1 km from the
source.
Although not shown here, a Level-3 analysis would be required for this
plant because of the failure of both the Level-1 and -2 tests for lines of
sight within the Class I area.
EXAMPLE 2: CEMENT PLANT AND RELATED OPERATIONS (1980 WORKBOOK EXAMPLE 2)
A cement plant has been proposed, along with related quarrying, materials
handling, and transportation facilities, for a location 20 km from a Class
I area. Terrain in the vicinity is relatively flat, and no external
vistas from the Class I area (a national park) are considered integral to
park visitor experience. Visibility at some locations within the park
boundaries is of concern, however.
The point in the Class I area closest to the proposed site is shown in
Figure C-2 as Point A. This point is 20 km away from the proposed
C-5
-------
TABLE C-l. FREQUENCY OF OCCURRENCE OF SW AND WSW WINDS BY DISPERSION
CONDITION AND TIME OF DAY
Dispersion
Condition
F, 1
E, 1
0, 1
F, 2
E, 2
D, 2
F, 3
E, 3
F, 4
D, 3
F, 5
E, 4
D, 4
F, 6
E, 5
°zu
(m2/s)
83
106
123
166
212
246
249
318
332
369
415
424
492
498
530
Transport Time
(hrs)
33
33
33
11
11
11
7
7
5
7
4
5
5
4
4
_ _ *
Time of Day
OOZ
0
0
0
0.1
0.6
1.6
0
0.6
0
3.4
0
0.4
2.4
0
0.2
12Z
0
0
0
0
0.9
0.8
0
1.4
0
1.2
0.1
1.2
1.5
0
1.8
Frequency
(*)
N/A
N/A
N/A
0.1
0.9
1.6
0
1.4
0
3.4
0.1
1.2
2.4
0
1.8
Cumulative
Frequency
(*)
N/Af
N/Af
N/Af
0.1
1.0
2.6
2.6
4.0
4.0
7.4
7.5
8.7
11.1
11.1
12.9
OOZ refers to midnight Greenwich mean time (GMT) and 12Z to noon GMT.
* Persistence of stable meteorological conditions for over 12 hours is not con-
sidered likely. Therefore, conditions requiring greater than 12-hour trans-
port time are included in the cumulative frequency computation,, but would not
be selected as representative of the "1-percentile event."
C-6
-------
*** User-selected Screening Scenario Results ***
Input Emissions for
Participates
NO* (as N02)
Primary N02
Soot
Primary S04
25.00 6 /S
380.00 G /S
.00 G /S
.00 G /S
.00 G /S
PARTICLE CHARACTERISTICS
Density Diameter
Primary Part.
Soot
Sulfate
2.5
2.0
1.5
Transport Scenario Specifications.
Background Ozone:
Background Visual Range:
Source-Observer Distance:
Mm. Source-Class I Distance:
Max. Source-Class I Distance:
Plume-Source-Observer Angle:
Stability: 5
Wind Speed: 2.00 m/s
.04 ppm
170.00 km
70 00 km
70.00 km
90 00 km
11.25 degrees
RESULTS
Asterisks (*) indicate plume impacts that exceed screening criteria
Maximum Visual Impacts INSIDE Class I Area
Screening Criteria ARE Exceeded
Delta £ Contrast
Backgrnd Theta Azi Distance Alpha Crit Plume Crit Plume
s
-------
Proposed
Cement Plant
lass I
Area Boundary
20
Scale
I
40 km
FIGURE C-2. Relative locations of Example 2 proposed cement
plant and Class I area.
C-8
-------
plant. Lines drawn 11.25° on either side of the line between the site and
Point A intersect the Class I area boundary at distances (for conservatism
in Level-1 screening) of 23 and 25 km. Since these distances are greater
than the minimum distance, the minimum distance to the Class I area boun-
dary (xmin) is set equal to 20 km, as suggested by the Workbook. The most
distant Class I area boundary (xmax) for analyses on Point A is 80 km away
from the cement plant site.
On the basis of discussions with the Federal Land Manager, the closest
point that is likely to be visited within the Class I area is 58 km away
from the site (Point B). The two dashed lines shown in Figure C-2, which
are drawn at 11.25° on opposite sides of the line connecting the plant
site and Point B, intersect the closest boundary at 40 and 44 km and the
most distant boundary at 117 and 90 km. For conservatism, xmi-n is set at
40 km and xmax is set at 117 km. Also for conservatism, Level-1 analysis
was performed using Point A, while Point B was used for Level-2 analysis.
The proposed project would cause elevated emissions from numerous process
points and ground-level emissions of fugitive dust. (Estimated emissions
rates and particle-size distributions are shown in Table C-2.) In the
Level-1 and -2 screening, for conservatism, all the elevated and ground-
based emissions were lumped together as if they originated from a single
source. Thus, the particulate emissions were specified as the sum of the
process and fugitive emissions. In the Level-1 analysis, Level-1 default
particle specifications were used rather than the known particle size
distributions. Exhibit C-3 summarizes the VISCREEN analysis results.
Since integral vistas are not protected at this Class I area, only the
within-park Impacts were relevant. Even so, every case considered-
forward and backward scatter as well as sky and terrain viewing
backgrounds—showed an impact exceeding the Level-1 screening criteria.
Thus, further screening and analysis were warranted.
The Level-2 analysis separately specified the process and fugitive emis-
sions with their known particle-size distributions (while still assuming
the two plumes overlapped). This was carried out by letting the primary
particulate signify the fugitive emissions and the primary sulfate signify
the process emissions. Particle sizes were specified to agree with Table
C-2. The less severe worst-case meteorology was found to be D and 1
m/s. Exhibit C-4 shows that VISCREEN calculated impacts were not in
excess of the screening criteria. The marked difference in Level-1 and
Level-2 results arises in part from the less conservative meteorology and
geometry of the Level-2 scenario. A major factor also, however, is the
significant change in particle size characteristics used for the fugitive
emissions.
C-9
-------
***
Input Emissions for
Particulates
NOx (as N02)
Primary N02
Soot
Primary S04
Level-1 Screening
***
4.93
2.72
.00
.00
.00
MT /DAY
MT /DAY
MT /DAY
MT /DAY
MT /DAY
**** Default Particle Characteristics Assumed
Transport Scenario Specifications:
Background Ozone:
Background Visual Range:
Source-Observer Distance:
Min. Source-Class I Distance:
Max. Source-Class I Distance:
Plume-Source-Observer Angle:
Stability: 6
Wind Speed: 1.00 m/s
.04 ppm
60.00 km
20.00 km
20.00 km
80.00 km
11.25 degrees
RESULTS
Asterisks (*) indicate plume impacts that exceed screening criteria
Maximum Visual Impacts INSIDE Class I Area
Screening Criteria ARE Exceeded
Delta E Contrast
Backgrnd Theta Azi Distance Alpha Crit Plume Crit Plume
SKY
SKY
TERRAIN
TERRAIN
10.
140.
10.
140.
145.
145.
84.
84.
28
28
20
20
.5
.5
.0
.0
24.
24.
84.
84.
2
2
2
2
.00
.00
.00
.00
18.
4.
27.
4.
245*
677*
724*
859*
.05
.05
.05
.05
.287*
-.186*
.279*
.134*
Maximum Visual Impacts OUTSIDE Class I Area
Screening Criteria ARE Exceeded
Delta E Contrast
Backgrnd Theta Azi Distance Alpha Crit Plume Crit Plume
SKY 10. 10. 9.6 159.
SKY 140. 10. 9.6 159.
TERRAIN 10. 35. 15.9 134.
TERRAIN 140. 35. 15.9 134.
2.00 22.273*
2.00 5.425*
2.00 30.404*
2.00 6.276*
.05 .346*
.05 -.224*
.05 .326*
.05 .190*
EXHIBIT C-3. Level 1 screening analysis for Example 2.
C-10
-------
TABLE C-2. Estimated project emissions.
Emissions
Emissions Rates
Particulate Matter
Process Sources
(effective stack height = 50 m)
DG = 1 um
0.395 MT/day
-3
p = 2 g cm
Fugitive Emissions
DG * 10 ym
4.54 MT/day
3
"J
p = 2 g cm
Sulfur Oxides
(effective stack height
Nitrogen Oxides
(effective stack height
50 m)
50 m)
7.26 MT/day
2.72 MT/day
C-ll
-------
*** User-selected Screening Scenario Results ***
Input Emissions for
Particulates 4.54 MT /DAY
NOx (as N02) 2.72 MT /DAY
Primary N02 .00 MT /DAY
Soot .00 MT /DAY
Primary S04 .40 MT /DAY
PARTICLE CHARACTERISTICS
Density Diameter
Primary Part.
Soot
Sulfate
2.0
2.0
2.0
9
1
5
Transport Scenario Specifications:
Background Ozone:
Background Visual Range:
Source-Observer Distance:
Min. Source-Class I Distance:
Max. Source-Class I Distance:
Plume-Source-Observer Angle:
Stability: 4
Wind Speed: 1.00 m/s
.04 ppm
60.00 km
58.00 km
40.00 km
117.00 km
11.25 degrees
RESULTS
Asterisks (*) indicate plume impacts that exceed screening criteria
Maximum Visual Impacts INSIDE Class I Area
Screening Criteria ARE NOT Exceeded
Delta E Contrast
Backgrnd Theta Azi Distance Alpha Crit Plume Crit Plume
SKY
SKY
TERRAIN
TERRAIN
10.
140.
10.
140.
35.
35.
35.
35.
46.1
46.1
46.1
46.1
134.
134.
134.
134.
2
2
2
2
.00
.00
.00
.00
.657
.307
.724
.155
.05
.05
.05
.05
.003
-.012
.009
.006
Maximum Visual Impacts OUTSIDE Class I Area
Screening Criteria ARE NOT Exceeded
Delta E Contrast
Backgrnd Theta Azi Distance Alpha Crit Plume Crit Plume
SKY
SKY
TERRAIN
TERRAIN
10.
140.
10.
140.
0.
0.
0.
0.
1
1
1
1
.0
.0
.0
.0
169.
169.
169.
169.
2
2
2
2
.00
.00
.00
.00
.802
.421
1.988
.636
.05
.05
.05
.05
.008
-.013
.018
.018
EXHIBIT C-4. Level 2 screening analysis for Example 2.
C-12
-------
EXAMPLE 3: PAPER MILL
A paper mill is proposed near a Class I area (see Figure C-3). Anticipa-
ted paper mill emissions are shown in Table C-3.
The closest point in the Class I area is Point A, which is 7.8 km from the
mill. However, Point B is the location in the Class I area that is
closest to the mill, relatively frequently visited, and unobstructed by
tree cover. Point A was used for Level-1 screening and Point B for Level-
2 screening.
Although a plume-rise analysis shows that the plume from the largest emis-
sion source (the power boiler) would not be at the same elevation as
plumes from other sources, and, thus, that plumes would not overlap, for
conservatism all emissions are lumped together as a single plume. Exhibit
C-5 shows the result of Level-1 VISCREEN calculations for this plume and
the closest Class I area boundary. With plume AE values ranging from 10.2
to 25.7 for views against the sky (views of distant terrain were not pos-
sible at this Class I area), the screening clearly shows the significant
potential for adverse plume visual impacts. The plume contrast values
indicate that the plume would be bright (positive contrast) in forward
scatter (sun in front of observer) and dark (negative contrast) in back-
ward scatter (sun behind observer).
An analysis of on-site data indicated that the worst-case meteorology
could be characterized by F and 3 m/s, rather than the F and 1 m/s assumed
in Level-1 screening. Exhibit C-6 summarizes VISCREEN results using this
meteorology and Point B geometry (see Figure C-3). Although impacts are
substantially lower (ranging from AE's of 4.0 to 8.6), they are still
considerably above the Level-2 screening criteria for both scattering
angles assumed. Since the plume-rise analysis indicated that the plume
from the largest emitter at the mill would not overlap plumes from other
sources, a final analysis was performed with emissions from this single
largest emission source—the power boiler. Exhibit C-7 summarizes the
VISCREEN results. AE's range from 2.2 to 4.7, down considerably from the
more conservative Level-1 and -2 analyses, but still considerably in
excess of the screening threshold. Thus, a Level-3 analysis would be war-
ranted in this case, and the possibility of adverse plume visual impact
could not be ruled out without additional analysis.
EXAMPLE 4: POWER PLANT IN THE WESTERN UNITED STATES
A power plant located in the western United States north of a Class I area
was scheduled to be expanded from two to four units of 400 MWe each.
Table C-4 summarizes the emissions for the base and expanded scenarios for
C-13
-------
Paper Mill
7.8 km
N
FIGURE C-3. Relative locations of paper mill and Class I area used in
example 3.
C-14
-------
TABLE C-3. Paper mill stack emissions data.
Stack Stack Exit Exit
Height Diam. Velocity Temp.
(Ft) (In) (Ft/Sec) (°F)
Emissions
(Metric Tons/Day)
PM
SO,
NOV
Power Boiler 200 144 25.36
Recovery Boiler 275 114 94.06
Smelt Tank 250 72 23.00
Lime Kiln 260 50 26.02
Total:
155 1.022
380 .491
155 .130
160 .087
1.756 2.027
4.069 1.560
.064
.091 .454
1.72 5.97
4.03
C-15
-------
Level-1 Screening
Input Emissions for
Participates
NOx (as N02)
Primary N02
Soot
Primary S04
1.72 HT /DAY
4.03 MT /DAY
.00 MT /DAY
.00 MT /DAY
.00 MT /DAY
**** Default Particle Characteristics Assumed
Transport Scenario Specifications:
Background Ozone: .04 ppm
Background Visual Range: 60.00 km
Source-Observer Distance: 7.80 km
Min. Source-Class I Distance: 7.80 km
Max. Source-Class 1 Distance: 13.00 km
Plume-Source-Observer Angle: 11.25 degrees
Stability: 6
Wind Speed: 1.00 m/s
RESULTS
Asterisks (*) indicate plume impacts that exceed screening criteria
Maximum Visual Impacts INSIDE Class I Area
Screening Criteria ARE Exceeded
Delta E Contrast
Backgrnd Theta Azi Distance Alpha Crit Plume Crit Plume
SKY
SKY
TERRAIN
10.
140.
10.
153.
153.
84.
13
13
7
.0
.0
.8
16.
16.
84.
2
2
2
.00
.00
.00
25,
10,
34,
.677*
.235*
.701*
.05
.05
.05
.201*
-.245*
.247*
TERRAIN 140. 84.
7.8 84. 2.00 5.013* .05 .086*
Maximum Visual Impacts OUTSIDE Class I Area
Screening Criteria ARE Exceeded
Delta E Contrast
Backgrnd Theta Azi Distance Alpha Crit Plume Crit Plume
SKY
SKY
TERRAIN
TERRAIN
10.
140.
10.
140.
2.
2.
2.
2.
1
1
1
1
.0
,0
.0
.0
167.
167.
167.
167.
2.
2.
2
2
,00
,00
.00
.00
31.
8.
52.
16.
191*
757*
,827*
,779*
.05
.05
.05
.05
.577*
-.337*
.597*
.564*
EXHIBIT C-5. Level 1 screening analysis for Example 3.
C-16
-------
*** User-selected Screening Scenario Results ***
Input Emissions for
Particulates
NOx (as N02)
Primary N02
Soot
Primary S04
.72
.03
.00
.00
.00
MT /DAY
MT /DAY
MT /DAY
MT /DAY
MT /DAY
PARTICLE CHARACTERISTICS
Density Diameter
Primary Part.
Soot
Sulfate
2.5
2.0
1.5
6
1
Transport Scenario Specifications:
Background Ozone:
Background Visual Range:
Source-Observer Distance:
Min. Source-Class I Distance:
Max. Source-Class I Distance:
Plume-Source-Observer Angle:
Stability: 6
Wind Speed: 3.00 m/s
.04 ppm
60.00 km
9.30 km
8.00 km
13.00 km
11.25 degrees
RESULTS
Asterisks (*) indicate plume impacts that exceed screening criteria
Maximum Visual Impacts INSIDE Class I Area
Screening Criteria ARE Exceeded
Delta E Contrast
Backgrnd Theta Azi Distance Alpha Crit Plume Crit Plume
SKY
SKY
TERRAIN
TERRAIN
10.
140.
10.
140.
144.
144.
47.
47.
13
13
8
8
.0
.0
.0
.0
25.
25.
122.
122.
2
2
2
2
.00
.00
.00
.00
8.
3.
15.
1.
558*
984*
596*
948
.05
.05
.05
.05
.062*
-.076*
.105*
.034
Maximum Visual Impacts OUTSIDE Class I Area
Screening Criteria ARE Exceeded
Delta E Contrast
Backgrnd Theta Azi Distance Alpha Crit Plume Crit Plume
SKY
SKY
TERRAIN
TERRAIN
10.
140.
10.
140.
1.
1.
1.
1.
1
1
1
1
.0
.0
.0
.0
167.
167.
167.
167.
2
2
2
2
.00
.00
.00
.00
19
5
36
9
.745*
.156*
.760*
.265*
.05
.05
.05
.05
.335*
-.204*
.403*
.294*
EXHIBIT C-6. Level 2 screening analysis for Example 3 (all emissions),
C-17
-------
*** User-selected Screening Scenario Results ***
Input Emissions for
Particulates
NOx (as N02)
Primary N02
Soot
Primary S04
1.02 MT /DAY
2.03 MT /DAY
.00 MT /DAY
.00 MT /DAY
.00 MT /DAY
PARTICLE CHARACTERISTICS
Density Diameter
Primary Part.
Soot
Sulfate
2.5
2.0
1.5
Transport Scenario Specifications:
Background Ozone: .03 ppm
Background Visual Range: 60.00 km
Source-Observer Distance: 9.30 km
Min. Source-Class I Distance: 8.00 km
Max. Source-Class I Distance: 13.00 km
Plume-Source-Observer Angle: 11.25 degrees
Stability: 6
Wind Speed: 3.00 m/s
RESULTS
Asterisks (*) indicate plume impacts that exceed screening criteria
Maximum Visual Impacts INSIDE Class I Area
Screening Criteria ARE Exceeded
Delta E Contrast
Backgrnd Theta Azi Distance Alpha Crit Plume Crit Plume
SKY
SKY
TERRAIN
TERRAIN
10.
140.
10.
140.
144.
144.
47.
47.
13,
13.
8
8
.0
.0
.0
.0
25.
25.
122.
122.
2
2
2
2
.00
.00
.00
.00
4,
2.
10.
1,
,724*
,184*
,096*
,150
.05
.05
.05
.05
.041
-.044
.064'
.020
Maximum Visual Impacts OUTSIDE Class I Area
Screening Criteria ARE Exceeded
Delta E Contrast
Backgrnd Theta Azi Distance Alpha Crit Plume Crit Plume
SKY
SKY
TERRAIN
TERRAIN
10.
140.
10.
140.
1.
1.
1.
1.
1
1,
1
1
.0
.0
.0
.0
167.
167.
167.
167.
2
2
2
2
.00
.00
.00
.00
14.
3.
29.
6.
179*
630*
335*
406*
.05
.05
.05
.05
.236*
-.144*
.306*
.192*
EXHIBIT C-7. Level 2 screening analysis for
Example 3 (power boiler emissions).
C-18
-------
TABLE C-4. Emissions parameters for Example 4 Power Plant,
Parameter
Stack height (ft)
(m)
Flue gas flow rate (acfm)
(nr/sec)
Flue gas temperature (°F)
(Q1S \
" /
Particulate emissions
Density (g/cnr)
Mass median diameter (pm)
Geometric standard deviation
Flue gas concentration
(ug/m^)
Flue gas opacity (%)
Mass emissions rate (g/sec)
Nominal control efficiency (%)
Sulfur dioxide (SC^) emissions
Flue gas concentration (ppm)
Mass emissions rate (g/sec)
Nominal control efficiency (%)
Nitrogen oxide emissions
Flue gas concentration (ppm)
Mass emissions rate (as NOp) (g/sec)
Emissions
Unit 1 or 2
600
183
1,555,980
734
138
332
2.0
1.7
1.5
25,100
20
18.4
99.5
93
132
80
366
372
per Unit
Unit 3 or 4
600
183
1,555,980
734
138
332
2.0
1.7
1.5
10,100
9
7.4
99.8
47
66
90
314
319
C-19
-------
each boiler unit. Figure C-4 summarizes the geometry of the plant, the
Class I area, and typical stable plume trajectories. The Federal Land
Manager was concerned about the view from the observer location shown in
this figure, because from this vantage point an observer has an unobstruc-
ted view north, where a plume from the power plant would probably be
transported. Since the vista of concern and the Class I area itself are
both elevated relative to the position of stable plumes, it was; felt that
stable plume transport into the Class I area was unlikely, but that a view
of a stable plume, as shown in Figure C-4, would be of concern.
Level-1 and -2 analyses were carried out using VISCREEN. These analyses
indicated that adverse visibility impairment could not be ruled out. As a
result, a Level-3 analysis was performed. PLUVUE was run for several
plume transport scenarios to characterize the cumulative frequency distri-
bution of plume visual impact for mornings in the four seasons. Since the
calculated plume visual impact magnitudes were to be coupled with the
cumulative frequency of conditions worse than the indicated impact, plume
positions for each wind direction sector modeled were selected so that the
plume impact was the minimum for the given sector (see Figures C-5 and
C-6). Plume visual impacts were calculated as a function of azimuth of
view and plotted as shown in Figure C-7. (A relatively close terrain fea-
ture caused the "blip" at the 45° azimuth.) The maximum plume A£ (over
all the possible azimuths) was determined for each plume transport
scenario corresponding to given meteorological conditions. The individual
scenarios were ordered in descending value of AE. The cumulative frequen-
cies for each season are plotted in Figure C-8. These results are sum-
marized in Table C-5.
EXAMPLE 5: COAL-FIRED POWER PLANT NEAR SEVERAL SENSITIVE AREAS
IN THE SOUTHWESTERN UNITED STATES
A large coal-fired power plant was proposed for location in the south-
western United States near three Class I areas. Table C-6 summarizes the
proposed plant emissions. VISCREEN modeling showed significant impacts
in each sensitive area for both the Level-1 and -2 scenarios. Thus, a
Level-3 analysis was carried out using the PLUVUE model.
Several plume trajectories were selected to represent the range of impacts
possible for each of the three sensitive areas (see Figure C-9). Meteoro-
logical data were available from the proposed power plant site. These
data were stratified by time of day and season (see Figure C-10). Table
C-7 summarizes the wind speed and stability assumed for each wind direc-
tion (plume trajectory). Table C-8 illustrates the wind direction sectors
C-20
-------
FIGURE C-4. Location of Example 4 power plant relative to
Class I area.
C-21
-------
FIGURE C-5. Plume trajectories corresponding to various wind
directions used in the visibility impact assessment.
C-22
-------
POTENTIALLY 1MPACTE
LINES OF SIGHT
POTEKT1ALLY IKPACTED
LINES OF Sl&HT
(a) North Wind Direction
(b) North-Northwesterly Wind Direction
POTENTIALLY I»ACT£0
LINES OF SIGHT
POTENTIALLY IMPACTED
LINES OF SIGHT
(c) Southwesterly Wind Direction
(d) North-Northeasterly Wind Direction
FIGURE C-6. Schematic diagram showing plume-observer geometry with least impact for given
wind direction sector.
C-23
-------
VICMINC
1-CUM WT. 2-unm SBJtCI.
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70
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Z 20
tw
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So
2«
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l-o-
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40.
ss.
30.
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520.
S|5.
10.
s.
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«s
90
US
KIINUIM
180
125 270
(a) 1 m/s wind speed, stable condition, 348.8 degree wind direction
FIGURE C-7. Examples of calculated plume visibility impairment dependent
on wind direction, azimuth of line of sight, and
viewing background.
C-24
-------
•MUMCD m«INC WCKCMimO:
I-CLtat MT. 2-MH1U MJCCT.
J-&IBT MJCCT. «-BL«K IBJCCT.
70.
Seo.
i50'
tol
* «.
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*•
2 20.
M
••lo.
0.
I.
I.
• I
Si.
go.
-0
S^
i:
-0,
M.
M.
«s
i as
MIHUTM
t*o
225
170
SCO
(b) 1 m/s wind speed, stable condition, 11.3 degree wind direction
FIGURE c-7(Continued)
C-25
-------
MSUMCO HICNIMC MCRWMtM:
l-CLt«« V.1. Z-MHIU MJCCT.
S-CfBT IBJtCT. 1-BlBCK »8JtCt.
M
JJS
1(0 22S 270
MCUIOCHECSI
J1S
SCO
(c) 1 m/s wind speed, stable condition, 22.5 degree wind direction
FIGURE c-7(Concluded)
C-26
-------
days
(a) Winter
days
(b) Spring
days
(c) Summer
days
(d) Autumn
FIGURE C-8. Predicted frequency of occurrence of plume visual impact perceptible
from a Class I area. Number of mornings in the designated season with an impact
greater than the indicated value.
C-27
-------
TABLE C-5. Summary of the frequency of occurrence of power plant plume visual
impact predicted for Example 4.
Number of Mornings with AE(L*a*b*) Greater
2.5
Season
Winter
Spring
Summer
Fall
Units
1 and 2
4
1
2
3
Units
1 through 4
6
2
3
5
Units
1 and 2
2
< 1
1
4
5
Units
1 through 4
3
1
1
2
than Indicated Value
Units
1 and 2
< 1
0
0
< 1
10
Units
1 through 4
1
0
0
< 1
Annual Total
10
16
< 2
C-28
-------
TABLE C-6. Emission values for a proposed southwestern U.S. power plant,
Capacity: 2000 Mwe (four 500-Mwe units)
Stack height: 400 ft
Mass emission rates (total, all stacks)*
S02: 937 g/s = 90 tons/day
NOV: 1240 g/s = 120 tons/day
X
Particulate: 8 tons/day
Fly ash particle-size distribution
Mass median diameter: 2.0 ym
Geometric standard deviation: 2.0
* Based on emission factors for S02, NOX, and particulate of 0.34,
0.45, and 0.03 lb/105 Btu, respectively.
C-29
-------
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C-32
-------
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FIGURE C-10. Example of on-site meteorological data (winter night,
December-February, 6 p.m.-6 a.m.; 3074 valid data points).
-------
TABLE C-7. Wind speeds and maximum transport distances associated with
transport condition scenarios.
Trajectories to
Area 1
Areas 2 and 3
Nominal
Wind Speed
(m/s)
1.0
1.0
3.0
7.0
2.0
2.0
4.0 .
6.0
Stability
D
E, F
D, E, F
D
D
E, F
D, E, F
D, E, F
Wind Speed Range
Included in
Computing Frequency
of Trajectories
(m/s)
0.0 < u < 1.0
0.0 < u < 1.0
1.0 < u < 3.0
3.0 < u < 7.0
1.0 < u < 2.0
1.0 < u < 2.0
2.0 < u < 4.0
4.0 < u < 6.0
Assumed Maximum
Transport Distance*
(km)
100
50
150
200
200
100
200
200
On the basis of the nominal wind speed and transport time of about 12 hours for E
and F stability categories and 24 hours for neutral (D stability) conditions.
C-34
-------
TABLE C-8. Wind direction classes and modeled plume trajectories.
Trajectory to
Area 1
Area 2
Area 3
Nominal
Wind Direction
ENE
SSE
WSW
NNW
E
ESE
SE
SSE
SW
WSW
WNW
NW
Modeled
Wind Direction
of Trajectory
78.75°
168.75°
258.75°
348.75°
156ot
151ot
149ot
ot
143
236.25°
258.75°
281.25°
303.75°
Wind Sectors Included
in Computing Frequency
of Trajectories*
N, NNE, NE, ENE
S, SSW, SW, WSW
W, WNW
NW, NNW
E (100%), ESE (25%)
ESE (75%), SE (50%)
SE (50%), SSE (75%)
SSE (25%), S (100%)
WSW (100%)
W (60%)
W (40%)
WNW (100%)
The wind sectors associated with each trajectory are those for which the
actual trajectory would be as close, or closer than, the trajectory
modeled. The percentages 1n parentheses indicate those cases in which
winds within a specific sector were apportioned to two different
trajectories. For example, 60 percent of the winds in the west
sector were assigned to the 258.75° trajectory toward Area 3; the
remaining 40 percent were assigned to the 281.25° trajectory.
Wind directions for Area 2 plume trajectories correspond to the final
leg of the plume trajectory (see Figure C-9b).
C-35
-------
that were associated with each plume trajectory so that cumulative fre-
quencies of various plume visual impacts could be derived. Table C-9 sum-
marizes the results of PLUVUE model runs for each of the meteorologi-
cal/plume scenarios. For the observer in Area 2, the plume would be
viewed against terrain backgrounds rather than the sky; thus, for these
vistas, white and gray terrain backgrounds were assumed to represent snow-
covered and sunlit terrain, respectively. The frequency of occurrence of
meteorological conditions associated with each scenario for each time of
day and season is also shown in Table C-9. From these summary tables,
cumulative frequency curves similar to those shown in Figure C-ll were
plotted for each area and each time of day/season.
EXAMPLE 6: CONSTRUCTION SITE NEAR A CLASS I AREA
A facility was proposed to be located only 1.9 km from the eastern boun-
dary of a Class I area (see Figure C-12). Three phases of construction or
operation were identified. Each of these phases (PI, P2, and P3) has its
own set of emissions (see Table C-10). Because diesel engines were used
during construction, emissions of NOX and soot were relatively high. In
addition, fugitive dust emissions from the construction vehicles' disrup-
tion of the native soil were high. However, these emissions would have
relatively high particle sizes.
Level-1 and -2 screening was performed, using VISCREEN, for each of the
three phases of construction/operation. For every emissions, sun angle,
and viewing background scenario, impacts were calculated to be consider-
ably in excess of the screening thresholds. Thus, a Level-3 analysis was
performed. Figure C-13 shows the plume trajectories that were modeled for
each of three observer locations. Since soot was an important emitted
species and PLUVUE is not capable of treating soot, the PLUVUE II model
was applied. A sensitivity analysis was carried out to determine the
emitted species most responsible for plume visual impacts. As shown in
Table C-ll, all three species (diesel exhaust or soot, NOX, and fugitive
dust) were important contributors; however, soot and NOX appeared to be
the largest contributors because both species absorb light, which results
in dark plumes. Because of the large number of wind speed/wind direc-
tion/stability scenarios for which the plume would be visible, over 200
PLUVUE II runs were made. Table C-12 summarizes the output from one of
these runs. For each run the maximum &E was selected from all the lines
of sight that were modeled. Tables C-13 and C-14 summarize these maximum
AE's. AE's were ordered by descending value (see Table C-15) and coupled
with frequencies of meteorological conditions (see Table C-16). Plumes
were predicted to be visible almost every day from observer location #1.
Plumes were also predicted to be visible from observer locations #2 and
13, but at lower frequencies.
C-36
-------
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i^r^»o««n«
* «M fit*, i
ii">»w«DP»»f"»p»
|1
T
•t^nbfwn»»»vtia»^«fipa««0«a«0v»%vw«««m«0ar»nnN«
K e D » » « e> d r> «N e & » »•' e* B» e r ci e> e; •;* e^ t: e> a* «l ei & ~ » » » e * a>
^ f^ ^ i^ «• ir r>
* e*« e e* a
•» »o "si «f — • n '•• .• •
ft e R e" a r. tj e c* i
T — •.«.«/•• tfi O« «••"»•• %s fs
*oi» »tt*bb c e*c e o~ —
c e
s/»
Miti« MU.
X
e
i!
si
VI O.
i:
o «
c f>
o> >e
u »—
V) U
C-39
-------
i 1 i
s a 5 g 2
""SI I
TJ
.!««
i >- r- L.
— 0. _l «i
BS -M
I 3
• _J
CL
C
TJ
W1
CT
C
SNOONM31JB JO M3BHnN
S-
o
in
a>
3
UJ
JL
53N1NKOH JO JOBHHN
C-40
-------
FIGURE C-12. Source and observer locations for Exanple 6.
C-41
-------
TABLE C-10. Emissions used as PLUVUE-II input for three
phases of construction and operation (tons per day).
Phase
NOx
Diesel
Exhaust
Fugitive
Oust
Phase 1 Construction (Pi) 0.95 0.06 0.15
Phase 2 Construction CP2) 2.75 0.28 0.61
Phase 3 Operation (P3) 0.59 0.0] 0.24
C-42
-------
FIGURE C-13a. Plume orientations for which plume visual impacts
were calculated from the perspectives of individual observers—
observer No. 1.
C-43
-------
FIGURE C-13b. Observer No. 2.
C-44
-------
FIGURE c-13c. Observer No. 3.
C-45
-------
TABLE C-ll. Sensitivity of plume visual Impact to emitted species.
Visual Range Blue-Red
Reduction (%) Ratio
Base Case
Diesel Exhaust Only
NOX Only
Fugitive Dust Only
15.2
9.8
5.7
1.7
0.987
0.988
0.998
0.996
Plume
Contrast
-0.016
-0.015
-0.011
-0.005
AE(l*a*b*)
0.641
0.586
0.497
0.175
Run Description:
Spring 0800 AM
Wind direction - E
Wind speed * 2 m/s
Stability - D
Observer II
Emissions: Phase Construction (PI)
Downwind distance: 3 km
C-46
-------
TABLE C-12. Examples of PLUVUE-II output.
EMISS DBS DATE TIME STAB WS WD
(M/S)
WD
w
WD
ENE
1 12/21 0800
DISTANCE (KM)
SKY BACKGROUND
REDUCTION OF VISUAL
RANGE (%)
BLUE-RED RATIO
PLUME CONTRAST AT
0.55um
PLUME PERCEPTIBILITY
DELTA E(L*A*B*)
DISTANCE (KM)
SKY BACKGROUND
REDUCTION OF VISUAL
RANGE (%)
BLUE-RED RATIO
PLUME CONTRAST AT
0.55 urn
PLUME PERCEPTIBILITY
DELTA E(L*A*B*)
DISTANCE (KM)
SKY BACKGROUND
REDUCTION OF VISUAL
RANGE (%)
BLUE-RED RATIO
PLUME CONTRAST AT
0.55 yffl
PLUME PERCEPTIBILITY
DELTA E(L*A*B*)
D ;
1.
.497
.919
-.032
3.110
1.
.550
.918
-.030
3.203
1.
.215
.965
-.011
1.315
7- WSW
3.
.454
.937
-.028
2.492
3.
.541
.935
-.024
2.629
3.
.063
.983
-.007
.585
5.
.500
.948
-.026
2.212
5.
.595
.945
-.023
2.352
5.
.133
.971
-.014
1.102
7.
.548
.960
-.024
1.873
7.
.642
.957
-.021
2.015
7.
.201
.970
-.017
1.243
10.
.646
.975
-.022
1.436
10.
.736
.972
-.018
1.574
10.
.312
.976
-.019
1.182
15.
.862
.992
-.018
.894
15.
.938
.989
-.015
1.007
15.
.533
.991
-.019
.859
C-47
-------
0)
en
3
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t
<— i
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3
cn
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a
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3
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00
c
c
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e
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c
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e
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C
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C
e
00
c
^
c
o
o
c
c
4
00
c
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^
c
o
o
c
c
m s> r-
(9 — S
an ^ ^r 01 cji
s ao
^ ^
00 00 C9 ^m
* * CM CV
00 — — 00 OO
— » » — —
— 00
(M »
UJ f> 10 «r *
IM uj ui (M rj
oo (M fi an on
-•»*--
uj to n
tvi » m
S (M CM S S
an — — p-
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s u) ui as a»
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an (M CM an ao
S IM CM S S
— r-
— (M
CM CS O CM S
— rn m — —
an p^i ro on ao
S CM CM S S
,M-rMrO-<9«U) Z Z 01 Z in 2 Ul Z
UIUIUIUIuJUIUIUJUJaJ3 Ul 33 Ul 3 33 3
U.QQQUIUIUjUIU.U.U.OQQQaQQQQQOQOQQ
C-48
-------
TABLE C-14. Summary of maximum AE's calculated for each
of the PLUVUE runs for Observers #2 and #3 for each nhase.
Stab. W:
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
5 ,m/s
2
->
L*
•7
2
2
T
t.
2
1
L.
n
£
2
1
1
1
\
1
1
3
3
3
3
3
3
5
5
5
5
5
5
WD
NNU
N
NNE
NE
ENE
E
ESE
SE
BSE
S
NNU
NNE
SE
NNE
E
ESE
NNW
ENE
SE
NNE
E
ESE
NNUI
ENE
SE
NNE
E
ESE
Pi
0.5
0.4
0.4
0.5
1 .0
0.4
0.2
0.2
0.2
0.7
5.4
3.2
0.3
0.7
0.2
0.2
0.5
0. 1
Obs,*2
P2
1 .0
2. 1
0.9
1 .6
17.1
1 . 1
1 .7
7.9
0.5
2.0
1 .2
P3
0.5
0.2
0.4
17.3
0.7
0.5
0.4
0.4
1 .6
1 .0
PI
0.5
0.4
0.4
0.4
0.4
0.7
4.4
0.5
0.3
0.2
0.6
3.3
10.0
0.3
0.5
3.3
0.2
0.4
2.3
Obs.f3
P2
6.6
1 .2
18.0
27.3
0.8
1 .0
5.3
0.4
1 .2
3.9
RO
0.2
0.4
2.7
0.3
18.2
28.5
0.2
0.4
2.1
0.1
1 .0
3.0
ENE 24.8 25.2
NOTE: All runs performed with a winter morning (0800)
sun angle.
C-49
-------
TABLE C-15. Transport scenarios ordered by maximum plume AE
for each observer location and phase of construction and operation.
TABLE
Stab. WS,
D
E
F
D
D
F
£
D
E
F
D
E
E
D
F
D
D
E
F
D
D
E
F
D
E
3-5
n/s
1
1
2
2
n
3
«1
L.
3
3
5
1
1
5
5
2
2
2
o
L.
3
n
L.
3
3
5
5
5
a
WD
Ul
Ul
Ul
U
wsw
w
U
U
U
W
ENE
ENE
Ul
Ul
ENE
ENE
E
ENE
ENE
UNU
ENE
ENE
ENE
ENE
ENE
TABLE 3-5d
Stab. WS.
0
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
m/s
1
1
2
1
3
2
5
2
n
£
2
2
3
2
3
5
2
2
5
WD
NNE
SE
ENE
NNU
ENE
NE
ENE
NNW
ESE
N
NNE
NNU
S
SE
NNW
SSE
SE
SE
Obs.fi
Pi
5.0
4.9
4.0
3.2
3. 1
3.0
3.0
2.4
2.3
2.1
2.1
1 .E
1 .6
1.6
1 .4
1 .3
1 .2
1.2
1 . 1
1 .1
1 .0
0.9
0.8
0.7
0.7
Obs.tZ
PI
5.4
3.2
1 .0
0.7
0.7
0.5
0.5
0.5
0.4
0.4
0.4
0.3
0.2
0.2
0.2
0.2
0.2
0.1
1
Stab.
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
'ABLE 3-!
WS ,m/s
1
1
2
2
3
3
1
1
1
5
5
n
£.
2
1
L.
3
3
3
5
5
5
5b ,
WD
W
WSW
W
WSW
W
WSW
WNW
ENE
E
W
WSW
WNW
ENE
E
ENE
WNW
E
ENE
WNW
E
Dbs.tl
P2
8.4
8.2
5.9
5.7
4.6
4.5
3.9
3.8
3.6
3.3
3.3
2.6
2.5
2.4
2.0
2.0
1 .9
1 .4
1 .4
1 .3
TABLE 3-5f Obs.*2
Stab.
D
D
D
D
D
D
D
D
D
D
D
WS.m/s
1
1
5
5
3
2
3
3
1
5
2
WD
ENE
SE
ENE
SE
NNW
ENE
ENE
SE
NNW
NNW
SE
P3
25.2
17.3
1 .6
1 .0
0.7
0.5
0.5
0.4
0.4
0.4
0.2
1
Stab.
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
ABLE 3-:
WS.11/5
1
1
2
2
3
3
1
1
1
5
5
2
2
2
3
3
3
5
5
5
5c
1
WO
WSW
W
WSW
W
W
WSW
WNW
E
ENE
WSW
W
WNW
E
ENE
WNW
E
ENE
ENE
E
WNW
Dbs.tl
P3
2.0
2.0
1 .3
1 .3
! .0
1 .0
0.9
0.8
0.8
0.7
0.7
0.6
0.5
0.5
0.4
0.4
0.4
0.3
0.3
0.3
TABLE 3-5e Obs.f2
Stab.
D
D
D
D
D
D
D
D
D
D
D
D
WS,m/s
1
1
3
2
5
3
1
5
3
2
2
5
WD
ENE
SE
SE
ENE
ENE
ENE
NNW
SE
NNW
NNW
SE
NNW
P2
24.8
17.1
7.9
2.1
2.0
1 .7
1 .6
1 .2
1 .1
1 .0
0.9
0.6
C-50
-------
TABLE C-15. Concluded.
TABLE 3-5g Obs.*3
TABLE 3-5h Obs.13
TABLE 3-5i Obs.«3
Stab.
D
D
D
D
D
D
D
D
D
D
D
D
0
D
D
D
D
D
D
WS ,m/s
1
2
3
1
5
2
1
1
L.
2
3
5
T
*•
2
2
2
3
"1
L.
5
2
WD
ESE
ESE
ESE
E
ESE
E
NNE
SE
NNU
E
E
NE
NNE
ENE
N
NNE
SSE
NNE
S
Pi
10.0
4.4
3.3
3.3
2.3
0.7
0.6
0.5
0.5
0.5
0.4
B.A
0.4
0.4
0.4
0.3
0.3
0.2
0.2
Stab.
D
D
D
D
D
D
D
D
D
D
US .m/s
1
1
2
3
5
5
1
3
3
5
WD
ESE
E
ESE
ESE
ESE
E
NNE
E
NNE
NNE
P2
27.3
18.0
6.E
5.3
3.9
1 .2
1 .2
1 .0
0.6
0.4
Stab.
D
D
D
D
D
D
D
D
D
D
D
0
US,m/5
1
1
5
2
3
5
3
2
1
3
2
5
WD
ESE
E
ESE
ESE
ESE
E
E
E
NNE
NNE
NNE
NNE
P3
28.5
18.2
3.0
2.7
2.1
1 .0
0.4
0.4
0.3
0.2
0.2
0.1
C-51
-------
TABLE C-16. Frequency of worst-case morning plume AE's for observers #1,
#2, and #3 in Class I area.
Delta
Wind
Speed
< n/s )
Wind
Direct ion
PI
Max
•
Avg.
P2
Max.
E
P3
AVQ.
Max
•
AVQ.
OBSERVER *1
1
1
2
3
5
WSW.W,
NE...
NE. . .
NE...
NE.. .
UNW
SE
SE
SE
SE
5.
4.
3.
! .
0.
0
9
0
0
7
4.8
4.7
2.8
0.9
0.G
8
3
~i
t.
1
1
.2
.6
.4
.9
.3
8.0
3.6
2.4
1.9
1 .3
2.
0.
0.
0.
0.
0
8
5
4
3
1 .9
0.8
0.5
0.4
0.3
OBSERVER i2
1
1
2
3
5
ENE.E,
NE. ..
NNE. . .
NNE . . .
NNE. . .
ESE
SE
SSE
SSE
SSE
5.
3.
1 .
0.
0.
4
1
i.
0
7
5
1 .5
0.9
0.2
0.2
0.1
24
17
7
2
1
.8
. 1
.9
i
.2
5.4
4.2
1 .9
1.2
0.5
25.
17.
1 .
1 .
0.
2
3
6
0
4
4.5
3.6
0.4
0.3
0.2
OBSERVER «3
1
1
2
3
5
SE.ESE
NE. ..
NNE. .
NNE. .
NNE. .
,SSE
SSE
.5
.5
.5
10.
4.
3.
0.
0.
0
4
3
5
2
3.9
1 .5
1 .0
0.2
0.2
27
18
6
0
0
.3
.0
.6
.6
.4
8.1
4.0
3.0
0.5
0.4
28.
18.
2.
0.
0.
5
2
7
2
1
6.1
3.3
1 .0
0.2
0.1
f _ Occ^rence Ll^
Ann. Wint.Spr. Sun. Fall
9.8 17.6 3.4 3.7 13.B
31.4 49.6 12.9 15.4 45.9
65.0 80.3 42 .,5 59.8 77.4
77.8 84.0 60.,3 80.8 87.0
86.1 86.9 74.3 93.0 91.4
1.0 0.8
2.2 2.4
14.2 11.1
17.4 15.1
0.0
0.4
9.8
1.4
2.3
1.9
2.9
5.8
14.3 29.9 16.3
19.0 15.5 16.3 34.1 16.3
2.3 2.5 1.1 2.3 3.3
3.2 2.6 1.1 4.7 4.1
18.3 12.8 12.4 29.0 20.3
22.2 14.0 17.3 36.9 22.2
24.0 15.2 19.2 41.' 22.5
C-52
-------
Appendix D
VISCREEN LISTING
-------
< 1> ******** Version 1.00 09 September 1988 *********
< 2>
< 3> PROGRAM VISCREEN
< 4>
< 5> £***********************************************************************
< 6> C
< 7> C Systems Applications, Inc. (415) 472-4011
< 8> C 101 Lucas Valley Road
< 9> C San Rafael, Ca 94903
< 10> C
< 11> C Telefax: 415/472-0907 Telex: 469287
< 12> C
< 13> c********************************************************
< 14> C
< 15> C VISCREEN is designed to calculate visual effects parameters
< 16> C (delta E and contrast) for a plume as observed from a given
< 17> C vantage point. Parameters are calculated using three wavelengths
< 18> C of light (0.4, 0.55, 0.7 urn) and for backgrounds against sky
< 19> C and dark terrain. VISCREEN is designed to calculate these
< 20> C parameters for emission sources of particulate, NO, N02, and
< 21> C soot. The emissions are assumed to create an infinitely long,
< 22> C straight plume whose position is specified by the program user.
< 23> C VISCREEN can be used for the first two levels of plume visual
< 24> C impact screening. It is not designed for analyses of regional
< 25> C haze. As implied by its name, VISCREEN is designed as a
< 26> C conservative screening tool. Additional analysis using a more
< 27> C refined plume visibility model should be conducted for sources
< 28> C that exceed screening criteria with VISCREEN.
< 29> C
< 30> c**********************************************************************
< 31> C
< 32> C The major variables used in VISCREEN include the following:
< 33> C
< 34> C ALPHA - angle between the line of sight and plume
< 35> C centerline
< 36> C BABS - light absorption coefficient (m-1)
< 37> C BABSN - light absorption coefficient for N02 (m2/g)
< 38> C BEXT - light extinction (scat + abs) coefficient (m-1)
< 39> C BSCAT - light scattering coefficient (m-1)
< 40> C BSCATV - light scattering per unit volume (m2/cm3)
< 41> C CGREEN - green plume contrast screening criterion (= 0.05)
< 42> C CMASS - conversion factor from units of input to grams
< 43> C CPLUME - contrast of plume against sky
< 44> C CTIME - conversion factor from units of input to seconds
< 45> C D - density for fine, coarse, plume particulate, soot,
< 46> C and primary S04 (DFINE,DCOARS,DPART,DSOOT,DS04)
< 47> C DCPLUM - double precision variable for CPLUME calculation
< 48> C DDELCR - double precision variable for contrast against terrain
< 49> C DELAB - delta E (L*A*B*), color difference parameter
< 50> C DELSKY - delta E for plume against the sky
-------
**
Page
C
52> C
53> C
54> C
55> C
56> C
57> C
88 >
89>
90>
91>
92>
93>
94>
95>
96>
58> C
59> C
60> C
61> C
62>
63>
64>
65>
66>
67> C
68> C
69> C
70> C
71> C
72> C
73> C
74> C
75> C
76> C
77> C
78> C
79>
80>
81>
82>
83>
84>
85>
86>
87> C
97> C
98>
99>
100>
101>
DELTER
DELCR
DIST
FLCK
FS
GAMMA
IERR
I LAMB
IPLTUS
IPSMRY
ISIZE
I STAB
ITHETA
LAMBDA
L1DFLT
LMDFLT
LPDFLT
LTDFLT
NSCAT
03
OMEGA
P
PBACK
PHI
PLUSKY
PLUTER
PRAY
Q
RO
RP
RV
SKY
SKYMAX
TAUPLU
TERAIN
TERMAX
THRESH
U
X
XMIN
XMAX
XBAR
delta E for plume against terrain
contrast of plume against terrain
distance between emission source and observer (km)
double precisioin check for underflow (=l.e-20)
solar light intensity
offset angle between plume centerlirie and line
between emissions source and observer
error flag returned from OPENA and RESPND
index for wavelength of
character path name for
character path name for
1= 0
( =
.4
0,ok)
urn)
between
line of
sight
light (e.g.,
result file
summary file
index for particle size distribution
index for stability (1=A;2=B;...6=F)
index for scattering angle tneta (angle
ray between sun and observer and the
wavelength of light (0.4, 0.55, 0.7 urn)
Level 1 default flag (=l,use defaults)
Meteorology default flag (=1, use defaults)
Particulate profile default flag (=l,use defaults)
Green & Delta E threshold default flag (=l,use default:
wavelength dependence of light scattering
ambient ozone concentration (ppm)
albedo (ratio of bscat to bext)
phase function (f of ISIZE, ILAMBDA, ITHETA)
phase function for background atmosphere
azimuthal angle between line connecting emission
source and observer and line of sight
radiance of plume when observed against the sky
radiance of plume when observed against terrain
phase function for Rayleigh (particle-free) atmosphere
emission rate for plume particulate, NOx, N02, soot,
and S04 (QPART,QNOX,QN02,QSOOT,QS04)
distance between observer and the terrain background
viewed behind plume (km)
distance between observer and observed portion of
plume (km)
background visual range (km)
radiance of sky without plume
maximum delta E for plume against the sky
plume optical thickness
radiance of terrain without plume
maximum delta E for plume against terrain
threshold delta E for screening success/failure (=
wind speed (meters/sec)
downwind distance between emission source and
observed plume parcel (km)
distance along plume to closest Class I area
boundary (km)
distance along plume to most distant Class I area
boundary (km)
chromaticity weighting function (also YBAR and ZBAR)
=2.0)
-------
**
Page
102> C
103> C
104>
105> C
106> C
XCAPO
chromaticity tristimulus value (also YCAPO and ZCAPO)
for white reference
108> C
109> C
110> C
111> C
112> C
113> C
114> C
115> C
116> C
117> C
118> C
119> C
120> C
121> C
122> C
123> C
124> C
125> C
126> C
127> C
128> C
129> C
130> C
131> C
132> C
133> C
134> C
135> C
136> C
137>
138>
139>
140>
142>
143>
144>
145>
146>
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150>
DATE
PROGRAMMER
MODIFICATION
Inc.
12/06/87 D. A. Latimer
Gaia Associates
1268 Idyl berry Rd
San Rafael CA 94903
(415) 499-0955
01/07/88 M. C. Causley
Systems Applications,
101 Lucas Valley Rd
San Rafael CA 94903
(415) 472-4011
02/08/88 R. G. Ireson
Systems Applications, Inc.
05/31/88 M. C. Causley
Systems Applications, Inc.
08/23/88 M. C. Causley
Systems Applications, Inc.
09/09/88 M. C. Causley
Systems Applications, Inc.
Original algorithm
Develop I/O structure
Restructure screening checks
Implement narrow plume threshold
Revise output formats
Trap math underflow where
contrast values are very
small (CPLUME.DELCR)
Finalize version 1.00
152>
COMMON/COLOR/DELAB,XBAR(3),YBAR(3),ZBAR(3)
COMMON/REF/XCAPO,YCAPO,ZCAPO
COMMON /IO/ ITERM,ISMRY,ILOTUS
COMMON /IFI/ IPSMRY,IPLTUS
COMMON /COMR/ ALPHA(39), BABS,BEXT(3),
+ CPLUME(3,2,39), DELCR(3,2,39), DIST, GAMMA,
& 03, P(3,2,9), PHI(39), RP(39), RV, TAU, X(39),
& U,OMEGA,XMIN,XMAX,DFINE,DCOARS,DPART,DSOOT,DS04,
& SKYMAX(2),TERMAX(2),THRESH,CGREEN,
& QPARTI,QPART,QNOXI,QNOX,QN02I,QN02,QSOOTI,QSOOT,QS04I,
& QS04,RO(39),PRAY(2),PBACK(3,2),SCTANG(2),SKY(3,2),
& TERAIN(3,2,39),PLUSKY(3,2,39),PLUTER(3,2,39),DELSKY(2,39),
& DELTER(2,39),SPECB(3),SPECP(3),
& PSI(39),PERTHR(39),THRSKY(2,39),THRTER(2,39),RATIO,
-------
**
Page
< 153> & RATSKY(2),RATTER(2)
< 154> COMMON /COMI/ ISIZE,ISTAB,ITHETA,IFINE,ICOARS,IPART,ISOOT,
< 155> & IS04,ISKYMX(2),ITERMX(2),IANS,IEMISS,IDIST,IPAR,IMET,
< 156> & L1DFLT,LSCLAS(39),MXANG,MXLOS,IMASS,ITIME,
< 157> & LMDFLT,LPDFLT,LTDFLT
< 158> INTEGER IERR,IANS
< 159> COMMON /CRGI/ LFIRST,ISCYMX(2),RATSCY(2),ITRCMX(2),RATTRC(2)
< 160> COMMON /COMC/ MASS,TIME,SOURCE,RECEPT,CLASSI,OBJSKY,OBJTER
< 161> CHARACTER*2 OBJSKY(2,39),OBJTER(2,39)
< 162> CHARACTER*3 MASS(5),TIME(5)
< 163> CHARACTER*? CLASSI(2)
< 164> CHARACTER*24 SOURCE,RECEPT
< 165> C
< 166> DOUBLE PRECISION DCPLUM,DDELCR,FLCK
< 167> REAL CGREEN,BABSN(3),BSCATV(9),LAMBDA(3),NSCAT(9),CMASS(5),
< 168> & CTIME(5),LAMB,PDUM(54),FS(3),ANGLE(13),CONT(13)
< 169> INTEGER IERR,IANS
< 170> CHARACTER*40 CSTR,IPSMRY,IPLTUS
< 171> LOGICAL LFLAG
< 172> C
< 173> DATA FLCK / l.OE-20 /
< 174> DATA LAMBDA/0.45,0.55,0.65/
< 175> DATA NSCAT/2.8,2.1,1.6,1.0,0.2,4*0./
< 176> DATA BSCATV/1.7,4.5,6.,6.7,5.,2.6,0.9,0.8,0.4/
< 177> DATA BABSN/0.691,0.144,0.015/
< 178> DATA ANGLE/0.02,0.025,0.033,0.05,0.1,0.2,0.33,0.5,1.,2.,5.,10.,
< 179> & 16.67/
< 180> DATA CONT/2.,0.572, 0.182,0.058,0.0190,0.010,0.0086,0.0084,
< 181> & 0.0100,0.0154,0.032,0.06,0.10/
< 182> DATA PDUM/
< 183> & 5.17,7.76,9.61,11.94,15.09,15.84,10.98,8.39,7.28,
< 184> & 0.330,0.199,0.172,0.169,0.174,0.143,0.082,0.064,0.046,
< 185> & 4.24,6.49,8.11,10.33,13.64,16.07,13.64,11.67,9.23,
< 186> & 0.429,0.247,0.193,0.165,0.166,0.156,0.094,0.085,0.055,
< 187> & 3.64,5.62,7.14,9.27,12.54,15.47,14.83,12.83,10.55,
< 188> & 0.517,0.296,0.219,0.175,0.170,0.170,0.136,0.106,0.075/
< 189> DATA FS/1712., 1730., 1414./
< 190> DATA CMASS/1.,1.E3,1.E6,453.6,9.072E5/
< 191> DATA CTIME/1.,60.,3600.,86400.,3.154E7/
< 192> C
< 193> c***********************************************************************
< 194> C
< 195> CALL INIT (IERR)
< 196> IF (IERR.NE.O) GO TO 999
< 197>
< 198> C INITIALIZE SOME MORE VARIABLES
< 199>
< 200> PI=ACOS(-1.)
< 201> RAD=PI/180.
< 202> SQRT2P = SQRT(2.*PI)
< 203> TWOTAN = 2. * TAN(RAD*22.5/2.)
-------
**
Page
204>
205>
206>
207>
208>
209>
210>
K = 1
DO 5 ILAMB = 1,3
XCAPO - XCAPO +
YCAPO = YCAPO +
ZCAPO - ZCAPO +
DO 5 ITHETA
DO 5 ISIZE
FS(ILAMB)/(2.*PI)
FS(ILAMB)/(2.*PI)
FS(ILAMB)/(2.*PI)
1,MXAN6
1,9
XBAR(ILAMB)
YBAR(ILAMB)
ZBAR(ILAMB)
P(ILAMB, ITHETA, ISIZE) = PDUM(K)
K = K + 1
CONTINUE
WRITE
WRITE
WRITE
WRITE
WRITE
URTTF
HIM 1 L
WRITE
WKlIt UU 1 SUKtLN 1NIKU
/* *\ i i
(*,*) '===========================================
/**)''
(*!*)' WELCOME TO PROGRAM VISCREEN! (Ver 1.00)'
(* *) / /
/* *\> a — — —
(**)''
212>
213>
214>
215> c**********************************************************************
216>
217> C PROGRAM INPUT
218> C
219>
220> C
221> C
222> C
223>
224>
225>
226>
227>
228>
229>
230> C
231> C
232> C
233>
234>
235> C
236>
237>
238>
239>
240>
241>
242>
243>
244>
245>
246> C
247>
248>
249>
250>
251>
252>
253>
254> C
==='
OPEN SUMMARY AND RESULTS FILE
CALL OPENA (IERR)
IF (IERR.NE.O) GO TO 999
WRITE (*,*) ' '
WRITE (*,'(A\)')' Input the name of the emissions source: '
CALL RESPND (4,IDUM,RDUM,CSTR,IERR)
IF (IERR.NE.O) GO TO 999
SOURCE = CSTR(1:24)
WRITE (V(A\)')' Input the name of the receptor (Class I area):
CALL RESPND (4,IDUM,RDUM,CSTR,IERR)
IF (IERR.NE.O) GO TO 999
RECEPT = CSTR(1:24)
SET DEFAULT FLAGS FIRST TIME AROUND
LMDFLT
LPDFLT
LTDFLT
L1DFLT
LFIRST
BACK TO HERE (LABEL 10) FOR SUBSEQUENT RUNS
-------
**
Page
< 255>
< 256> 10 CONTINUE
< 257> IF(IEMISS.EQ.O) GO TO 150
< 258> 11 WRITE (*,*) ' '
< 259> WRITE (*,*)'Select the units of mass for emission',
< 260> & ' rates--'
< 261> WRITE (*,*)'l=gram (g); 2=kg; 3*metric tonne (mt); 4=lb; 5=ton:
< 262> WRITE (*,'(A\)')' Enter no. (1-5): '
< 263> CALL RESPND (2,IMASS,RDUM.CSTR,IERR)
< 264> IF (IERR.NE.O) GO TO 999
< 265> IF (IMASS.LT.l .OR. IMASS.GT.5) THEN
< 266> WRITE (*,*) ' Invalid mass unit = ',IMASS,' try again...'
< 267> GO TO 11
< 268> ENDIF
< 269>
< 270> 15 WRITE (*,*) ' '
< 271> WRITE (*,*)'Select the units of time for emission rates--'
< 272> WRITE (*,'(A\)')' l=sec; 2=min; 3=hr; 4=day; 5=yr:',
< 273> & ' Enter no. (1-5): '
< 274> CALL RESPND (2,ITIME,RDUM,CSTR,IERR)
< 275> IF (IERR.NE.O) GO TO 999
< 276> IF (ITIME.LT.l .OR. ITIME.GT.5) THEN
< 277> WRITE (*,*) ' Invalid unit of time = ',ITIME,' try again...'
< 278> GO TO 15
< 279> ENDIF
< 280>
< 281> 100 CONTINUE
< 282> WRITE (*,*) ' '
< 283> WRITE (*,*) 'Input the emission rates for the following',
< 284> & ' species: '
< 285> WRITE (*,'(A,A,A,A,A\)')' Particulates (',MASS( IMASS),'/',
< 286> & TIME(ITIME),' ): '
< 287> CALL RESPND (3,IDUM,QPARTI,CSTR,IERR)
< 288> IF (IERR.NE.O) GO TO 999
< 289> WRITE (*,'(A,A,A,A,A\)')' NOx (as N02) (',MASS(IMASS),'/',
< 290> & TIME(ITIME),' ): '
< 291> CALL RESPND (3,IDUM,QNOXI,CSTR,IERR)
< 292> IF (IERR.NE.O) GO TO 999
< 293>
< 294> QN02I = 0.
< 295> QSOOTI = 0.
< 296> QS04I = 0.
< 297> WRITE (*,*)' '
< 298> WRITE (*,'(A\)')' Do you want to use default (zero) emission ',
< 299> & ' rates for primary N02,'
< 300> WRITE (V(A\)')' soot, and sulfate (y/n)? '
< 301> CALL RESPND (1,IANS,RDUM,CSTR,IERR)
< 302> IF (IERR.NE.O) GO TO 999
< 303> IF(IANS.EQ.l) GO TO 110
< 304>
< 305> WRITE (*,'(A,A,A,A,A\)')' Primary N02 (',MASS(IMASS),'/',
-------
**
Page
306> & TIME(ITIME)/ ): '
307> CALL RESPND (3,IDUM,QN02I,CSTR,IERR)
308> IF (IERR.NE.O) GO TO 999
309> WRITE (V(A,A,A,A,A\)') ' Soot (',MASS(IMASS),'/',
310> & TIME(ITIME),' ): '
311> CALL RESPND (3,IDUM,QSOOTI,CSTR,IERR)
312> IF (IERR.NE.O) GO TO 999
313> WRITE (*,'(A,A,A,A,A\)')' Primary S04 (',MASS(IMASS),'/',
314> & TIME(ITIME),' ): '
315> CALL RESPND (3,IDUM,QS04I,CSTR,IERR)
316> IF (IERR.NE.O) GO TO 999
317>
318> 110 WRITE (*,*)' '
319> WRITE (*,*)'SUMMARY: Emissions for ',SOURCE
320> WRITE (*,*)'Particulates ',QPARTI,' ',MASS(IMASS),'/'.TIME(ITIME)
321> WRITE (*,*)'NOx (as N02) ',QNOXI,' ',MASS(IMASS),'/',TIME(ITIME)
322> WRITE (*,*)'Primary N02 ',QN02I,' ',MASS(IMASS),'/',TIME(ITIME)
323> WRITE (*,*)'Soot ',QSOOTI,' ',MASS(IMASS),'/'JIME(ITIME)
324> WRITE (*,*)'Primary S04 ',QS04I,' '.MASS(IMASS),'/',TIME(ITIME)
325> WRITE (*,*)' '
326> WRITE (*,'(A\)')
327> & ' Are these the emission rates you meant to use (y/n)? '
328> CALL RESPND (1,IANS,RDUM,CSTR,IERR)
329> IF (IERR.NE.O) GO TO 999
330> IF(IANS.EQ.O) THEN
331> WRITE (*,*)'You may now enter new values of emission rates.'
332> GO TO 100
333> END IF
334>
335> 150 CONTINUE
336> IF(IDIST.EQ.O) GO TO 200
337> WRITE (*,*)' '
338> WRITE (*,*)'Input the distance between the emissions source and'
339> WRITE (V(A\)')' the observer (in kilometers): '
340> CALL RESPND (3,IDUM,DIST,CSTR,IERR)
341> IF (IERR.NE.O) GO TO 999
342> WRITE (*,*) ' '
343> WRITE (*,*)'Input the distance between the emissions source ',
344> & 'and the'
345> WRITE (V(A\)')' closest Class I area boundary (in kilometers): '
346> CALL RESPND (3,IDUM,XMIN,CSTR,IERR)
347> IF (IERR.NE.O) GO TO 999
348> WRITE (*,*) ' '
349> WRITE (*,*)'Input the distance between the emissions source ',
350> & 'and the'
351> WRITE (V(A,A\)')' most distant Class I area boundary ',
352> & ' (in kilometers):'
353> CALL RESPND (3,IDUM,XMAX,CSTR,IERR)
354> IF (IERR.NE.O) GO TO 999
355>
356> 190 CONTINUE
-------
**
Page 8
357> WRITE (*,*) ' '
358> WRITE (V(A,A\)')' Input the background visual range for ',
359> & 'the area (km): '
360> CALL RESPND (3,IDUM,RV,CSTR,IERR)
361> IF (IERR.NE.O) GO TO 999
362> WRITE (*,*)' '
363>
364> 200 CONTINUE
365> IF(IPAR.EQ.O) GO TO 250
366> IF (LFIRST.EQ.l) THEN
367> WRITE (*,*) ' '
368> WRITE (*,'(A,A\)')' Do you wish to use Level-1 default ',
369> & 'parameters (y/n)? '
370> CALL RESPND (1,IANS,RDUM,CSTR,IERR)
371> IF (IERR.NE.O) GO TO 999
372> IF (IANS.EQ.1) GO TO 360
373> ENDIF
374> L1DFLT = 0
375> LPDFLT = 0
C
378> C LEVEL-2, NON-DEFAULT INPUT SPECIFICATION
379> C
380> £**********************************************************************
381> 225 CONTINUE
382> WRITE (*,*) 'SPECIFICATION OF PARTICLE DENSITY AND SIZE '
383> WRITE (*,*) ' '
384> WRITE (*,*) 'Enter the density and the index corresponding to the'
385> WRITE (*,*) ' mass median diameter of the size distribution for '
386> WRITE (*,*) ' BACKGROUND fine and coarse particulate, and'
387> WRITE (*,*) ' PLUME particulate, soot, and primary sulfate).'
388> WRITE (*,*) ' '
389> WRITE (*,*)'Mass median diameter (in urn): 1=0.1 urn; 2=0.2 urn; '
390> WRITE (*,*)' 3=0.3 urn; 4=0.5 urn; 5=1 urn; 6=2 urn; 7=5 urn; 8=6 urn;'
391> WRITE (*,*) ' 9=10 urn.
392> WRITE (*,*) ' '
393> WRITE (*,*) 'Enter density (g/cm3) and size index'
394> WRITE (*,'(A\)') ' (default values are shown in parentheses): '
395> WRITE (*,*) ' '
396> WRITE (V(A\)') ' Background Fine Particulate Density (1.5): '
397> CALL RESPND (3,IDUM,DFINE,CSTR,IERR)
398> IF (IERR.NE.O) GO TO 999
399> 227 WRITE (*/(A\)') ' Background Fine Particulate Size Index (3): '
400> CALL RESPND (2,IFINE,RDUM,CSTR,IERR)
401> IF (IERR.NE.O) GO TO 999
402> IF (IFINE.LT.l .OR. IFINE.GT.9) THEN
403> WRITE (*,*) ' Invalid size index = ',IFINE,' try again...'
404> WRITE (*,*) ' '
405> GO TO 227
406> ENDIF
407>
-------
**
Page
< 408>
< 409>
< 410>
< 412> 229
< 413>
< 414>
< 415>
< 416>
< 417>
< 418>
< 419>
< 420>
< 421>
< 422>
< 423>
< 424>
< 425> 231
< 426>
< 427>
< 428>
< 429>
< 430>
< 431>
< 432>
< 433>
< 434>
< 435>
< 436>
< 437>
< 438> 233
< 439>
< 440>
< 441>
< 442>
< 443>
< 444>
< 445>
< 446>
< 447>
< 448>
< 449>
< 450>
< 451>
< 452> 235
< 453>
< 454>
< 455>
< 456>
< 457>
< 458>
WRITE (*,*) ' '
WRITE (V(A\)') ' Background Coarse Particulate Density (2.5):
CALL RESPND (3,IDUM,DCOARS,CSTR,IERR)
IF (IERR.NE.O) GO TO 999
WRITE (V(A\)') ' Background Coarse Particulate Size Index (8):
CALL RESPND (2,ICOARS,RDUM,CSTR,IERR)
IF (IERR.NE.O) GO TO 999
IF (ICOARS.LT.l .OR. ICOARS.GT.9) THEN
WRITE (*,*) ' Invalid size index = MCOARS,' try again...'
WRITE (*,*) ' '
GO TO 229
ENDIF
WRITE (*,*) ' '
WRITE (V(A\)') ' Plume Particulate Density (2.5): '
CALL RESPND (3,IDUM,OPART,CSTR,IERR)
IF (IERR.NE.O) GO TO 999
WRITE (V(A\)') ' Plume Particulate Size Index (6): '
CALL RESPND (2,IPART,RDUM,CSTR,IERR)
IF (IERR.NE.O) GO TO 999
IF (IPART.LT.l .OR. IPART.GT.9) THEN
WRITE (*,*) ' Invalid size index = MPART,' try again...'
WRITE (*,*) ' '
GO TO 231
ENDIF
WRITE (*,*) ' '
WRITE (V(A\)') ' Plume Soot Density (2.0):
CALL RESPND (3,IDUM,DSOOT,CSTR,IERR)
IF (IERR.NE.O) GO TO 999
WRITE (V(A\)') ' Plume Soot Size Index (1):
CALL RESPND (2,ISOOT,RDUM,CSTR,IERR)
IF (IERR.NE.O) GO TO 999
IF (ISOOT.LT.l .OR. ISOOT.GT.9) THEN
Invalid size index = ',ISOOT,
WRITE (*,*)
WRITE (*,*)
GO TO 233
ENDIF
try again.
WRITE (*,*) ' '
WRITE (V(A\)') ' Plume Primary S04 Density (1.5): '
CALL RESPND (3,IDUM,DS04,CSTR,IERR)
IF (IERR.NE.O) GO TO 999
WRITE (V(A\)') ' Plume Primary S04 Size Index (4): '
CALL RESPND (2,IS04,RDUM,CSTR,IERR)
IF (IERR.NE.O) GO TO 999
IF (IS04.LT.1 .OR. IS04.GT.9) THEN
WRITE (*,*) ' Invalid size index = ',IS04,' try again.
WRITE (*,*) ' '
GO TO 235
-------
**
Page
10
459>
460>
461>
462>
463>
464>
465>
466>
467>
468>
469> 250
470>
471>
472>
473>
474>
475>
476>
477>
478> 300
479>
480>
481>
482>
483> 310
484>
485>
486>
487>
488>
489>
490>
491>
492>
493>
494> 350
495>
496>
497>
498>
499>
500>
501>
502> C
503> C
504>
505>
506>
507>
508>
509>
ENDIF
WRITE (*,*) ' '
WRITE (*,*)' Are you sure these are the
& 'you want for '
WRITE (V(A\)T particle densities and
CALL RESPND (1,IANS,RDUM,CSTR,IERR)
IF (IERR.NE.O) GO TO 999
IF(IANS.EQ.O) GO TO 225
CONTINUE
IF(IMET.EQ.O) GO TO 360
LMDFLT = 0
WRITE (*,*)' '
WRITE (*,*)' Enter Background Ozone (03)
WRITE (V(A\)T (default = 0.04 ppm)
CALL RESPND (3, IDUM,03,CSTR, IERR)
IF (IERR.NE.O) GO TO 999
CONTINUE
WRITE (*,*)' '
WRITE (*,'(A\)')' Enter the wind speed (
CALL RESPND (3,IDUM,U,CSTR, IERR)
IF (IERR.NE.O) GO TO 999
WRITE (*,*) 'Enter the stability index--
WRITE (V(A\)') ' (1-A; 2=B; 3=C; 4=D;
CALL RESPND (2,ISTAB,RDUM,CSTR,IERR)
IF (IERR.NE.O) GO TO 999
IF (ISTAB.LT.l .OR. ISTAB.GT.6) THEN
WRITE (*,*) ' Invalid stability index
WRITE (*,*) ' '
GO TO 310
ENDIF
CONTINUE
WRITE (*,*) ' '
WRITE (*,*)' Enter the plume offset angle
values ',
sizes (y/n)? '
Concentration in ppm '
. i
in meters/sec) : '
/
5=E; 6-F): '
= MSTAB,' try again...'
(i.e., the angle between'
WRITE (*,*)' the plume centerline and the line between the '
WRITE (*,*)' observer and the emissions
source) in degrees. '
WRITE (*,'(A\)')' Default is 11.25 degrees (1/2 sector width): '
CALL RESPND (3, IDUM, GAMMA, CSTR, IERR)
IF (IERR.NE.O) GO TO 999
---CHECK TO SEE IF GAMMA IS ACCEPTABLE.
WRITE (*,*) ' '
IF(GAMMA.LT.11.25) THEN
IF NOT, REJECT OR WARN USER
WRITE (*,*)'Your input value is less than recommended minimum!'
IF(GAMMA.LE.O.) GO TO 350
WRITE (V(A\)')' Do you still want to
& ' input value (y/n)?
use your ' ,
/
-------
** Page 11
510> CALL RESPND (1,IANS,RDUM,CSTR,IERR)
511> IF (IERR.NE.O) GO TO 999
512> IF(IANS.EQ.O) GO TO 350
513> END IF
514> IF(GAMMA.GT.180.) THEN
515> WRITE (*,*)'Your value is greater than maximum of 180 degrees!'
516> WRITE (V(A\)')' Please input value less than 180 degrees: '
517> CALL RESPND (3,IDUM,GAMMA,CSTR,IERR)
518> IF (IERR.NE.O) GO TO 999
519> END IF
520> IF(GAMMA.GT.168.75) THEN
521> WRITE (*,*)'Your input value is greater than recommended',
522> & ' maximum!'
523> WRITE (V(A\)')' Do you still want to use your ',
524> & 'input value (y/n)? '
525> CALL RESPND (1,IANS,RDUM,CSTR,IERR)
526> IF (IERR.NE.O) GO TO 999
527> IF(IANS.EQ.O) GO TO 350
528> END IF
529>
530> C END OF NON-DEFAULT SPECIFICATION
531> C
532>
533> C
534> C PRINT A SUMMARY OF MAJOR INPUT VALUES
535> C
536>
537>
538> 360 CONTINUE
539> WRITE (*,*) ' '
540> WRITE (*,*) 'SUMMARY OF ALL EMISSIONS AND METEOROLOGICAL INPUT'
541> WRITE (*,*) ' '
542> WRITE (*,*) 'Emissions for ',SOURCE,' in ',MASS(IMASS),'/',
543> & TIME(ITIME),':'
544> WRITE (*,*)' Particulate = ',QPARTI
545> WRITE (*,*)' NOx = ',QNOXI
546> WRITE (*,*)' Primary N02 = '.QN02I
547> WRITE (*,*)' Soot = ',QSOOTI
548> WRITE (*,*)' Primary S04 = '.QS04I
549> WRITE (*,*) ' '
550> WRITE (*,*) 'Meteorological and Ambient Data for ',RECEPT
551> WRITE (*,*) ' '
552> WRITE (*,*) ' Wind speed (m/s) = ',U
553> WRITE (*,*) ' Stability Index « ',ISTAB
554> WRITE (*,*) ' Visual Range (km) = ',RV
555> WRITE (*,*) ' Ozone Cone, (ppm) = ',03
556> WRITE (*,*) ' Plume Offset Angle= ',GAMMA,' degrees'
557> WRITE (*,*) ' '
558> WRITE (*,*) 'Distances Between '.SOURCE,' and ',RECEPT
559> WRITE (*,*) ' '
560> WRITE (*,*) ' Source-Observer = ',DIST, ' km'
-------
**
Page 12
561> WRITE (*,*) ' Min. Source-Class I = ',XMIN, ' km'
562> WRITE (*,*) ' Max. Source-Class I = ',XMAX, ' km'
563> WRITE (*,*) ' '
564> WRITE (*,'(A,A\)')' Are these input values ready for ',
565> & 'execution (y/n)? '
566> CALL RESPND (1,IANS,RDUM,CSTR,IERR)
567> IF (IERR.NE.O) GO TO 999
568> IF(IANS.EQ.O) GO TO 9000
569> WRITE (*,*) ' '
570> WRITE (V(A,A\)')' Do you want to use the default ',
571> & 'screening threshold (y/n)? '
572> CALL RESPND (1,IANS,RDUM,CSTR,IERR)
573> IF (IERR.NE.O) GO TO 999
574> IF (IANS.EQ.1) GO TO 370
575> LTDFLT = 0
576> WRITE (*,*) ' '
577> WRITE (*,'(A,F5.2,A\)') ' Input delta E threshold (default = ',
578> & THRESH,'): '
579> CALL RESPND (3,IDUM,THRESH,CSTR,IERR)
580> IF (IERR.NE.O) GO TO 999
581> WRITE (*,*) ' '
582> WRITE (V(A,A,F5.2,A\)') ' Input green contrast threshold ',
583> & '(default = ',CGREEN/ ): '
584> CALL RESPND (3,IDUM,CGREEN,CSTR,IERR)
585> IF (IERR.NE.O) GO TO 999
586>
587> 370 CONTINUE
588>
589> C WRITE OUTPUT HEADER INFO TO SUMMARY FILE AND
590> C INPUTS TO FULL RESULTS FILE
591> C
592> IF ((LTDFLT*LMDFLT*LPDFLT).EQ.O) L1DFLT - 0
593> CALL SMRPT1 (IERR)
594> CALL WINPTS (IERR)
595> C
597> C
598> C PROGRAM EXECUTION
599> C
600> c****************************************************************
601> C
602> C STORING ARRAYS INITIALIZED
603> C
604> CALL INIT2 (IERR)
605> C
606> C STEP 1: CONVERT ALL EMISSION RATES TO GRAMS/SECOND
607> C UNLESS THAT'S HOW THEY ARE ON INPUT
608> C
609> CONVER = CMASS(IMASS)/CTIME(ITIME)
610> QPART = QPARTI*CONVER
611> QNOX = QNOXI*CONVER
-------
** Page 13
< 612> QN02 = QN02I*CONVER
< 613> QSOOT = QSOOTI*CONVER
< 614> QS04 = QS04I*CONVER
< 615> C
< 616> C --ASSUME 10% OF INITIAL NO IS CONVERTED THERMALLY TO N02
< 617> QN02 = QN02 + 0.1*QNOX
< 618> QNOX = 0.9*QNOX
< 619> C
< 620> C STEP 2: DETERMINE PLUME-OBSERVER GEOMETRY FOR EVERY LINE OF SIGHT
< 621> C CORRESPONDING TO 5 DEGREES OF AZIMUTH SCAN STARTING FROM
< 622> C THE SOURCE
< 623> C
< 624> 375 CONTINUE
< 625> GAMMA2 = GAMMA + 11.25
< 626> IMAX = (180.-GAMMA)/5 -2
< 627> DO 400 IVIEW = l.IMAX
< 628> C ---OBSERVER LINES OF SIGHT ARE DRAWN FOR EACH 5 DEGREES
< 629>
< 630> PHI(IVIEW) = IVIEW*5.
< 631>
< 632> C ---ANGLE ALPHA: SINCE SUM OF INTERIOR ANGLES OF TRIANGLE TOTALS 180.
< 633>
< 634> ALPHA(IVIEW) = 180. - PHI(IVIEW) - GAMMA
< 635>
< 636> C ---SINCE THE RATIOS OF THE LENGTHS OF THE SIDES OF A TRIANGLE TO THE
< 637> C SINE OF THE OPPOSITE ANGLE ARE EQUAL,
< 638>
< 639> X(IVIEW) = DIST * SIN(RAD*PHI(IVIEW))/SIN(RAD*ALPHA(IVIEW))
< 640> RP(IVIEW) = DIST * SIN(RAD*GAMMA)/SIN(RAD*ALPHA(IVIEW))
< 641> ALPHA2 = ALPHA(IVIEW) - 11.25
< 642> R0(IVIEW) = DIST * SIN(RAD*GAMMA2)/SIN(RAD*ALPHA2)
< 643> IF(ALPHA2.LT.O.) RO(IVIEW) = RP(IVIEW)
< 644> IF(RP(IVIEW).GT.999.) RP(IVIEW) = 999.
< 645> IF(RO(IVIEW).GT.999.) RO(IVIEW) = 999.
< 646> 400 CONTINUE
< 647> C
< 648> C STEP 2A: DETERMINE PLUME-OBSERVER GEOMETRY FOR THREE ADDITIONAL
< 649> C LINES OF SIGHT DESIGNED TO PASS THROUGH THE PLUME PARCEL
< 650> C LOCATED 1 KM DOWNWIND FROM SOURCE, AT THE NEAREST CLASS
< 651> C I AREA BOUNDARY, AND AT THE MOST DISTANT CLASS I AREA
< 652> C BOUNDARY.
< 653> C
< 654> X(IMAX+1) = 1.
< 655> X(IMAX+2) = XMIN
< 656> X(IMAX+3) = XMAX
< 657> DO 450 IVIEW = IMAX+l,IMAX+3
< 658> DPRIME = X(IVIEW) * COS(RAD*GAMMA)
< 659> DDOUBL = DIST - DPRIME
< 660> H = X(IVIEW) * SIN(RAD*GAMMA)
< 661> PHI(IVIEW) = (l./RAD) * ATAN(H/DDOUBL)
< 662> IF(PHI(IVIEW).LT.O.) PHI(IVIEW) = PHI(IVIEW) + 180.
-------
** Page 14
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ALPHA(IVIEW) = 180. - GAMMA - PHI(IVIEW)
RP( IVIEW) = X( IVIEW) * SIN(RAD*GAMMA)/SIN(RAD*PHI( IVIEW))
ALPHA2 * ALPHA( IVIEW) - 11.25
IF(ALPHA2.LT.11.25)ALPHA2 = 11.25
R0( IVIEW) = DIST * SIN(RAD*GAMMA2)/SIN(RAD*ALPHA2)
IF(ALPHA2.LT.O.) RO(IVIEW) = RP(IVIEW)
IF(RP(IVIEW).GT.999.) RP(IVIEW) = 999.
IF(RO(IVIEW).GT.999.) RO(IVIEW) = 999.
CONTINUE
STEP 3: CALCULATE THE ATMOSPHERE OPTICAL CHARACTERISTICS
USING KOSCHMIEDER EQUATION ASSUMING VISUAL RANGE IS RELATED TO
THE LIGHT EXTINCTION AT 0.55 UM (ILAMBDA = 2)
BEXT(2) = 3.912/(RV*1000.)
BRAY = 11.62E-6
BSP = B€XT(2) - BRAY
IF(BSP.LT.O.) THEN
WRITE (*,*) 'Your chosen value of background visual range',
& 'is too high. Please try again!'
GO TO 190
END IF
BSFINE = 0.67 * BSP
BSCOAR » 0.33 * BSP
RAYLEIGH PHASE FUNCTION AT THETA = 10 AND 140 DEGREES; ALL LAMBDA
(CALCULATED FROM EQUATION: PRAY = 0.75*(1.+(COS(THETA))**2)
PRAY(l) - 1.4774
PRAY(2) - 1.1901
DO 500 ILAMB =1,3
BSF = BSFINE * (LAMBDA(ILAMB)/0.55)**(-NSCAT(IFINE))
BSC = BSCOAR * (LAMBDA(ILAMB)/0.55)**(-NSCAT(ICOARS))
BSR = BRAY * (LAMBDA(ILAMB)/0.55)**(-4.1)
BEXT(ILAMB) = BSF + BSC + BSR
DO 500 ITHETA =1,2
PBACK( ILAMB, ITHETA) = ( BSF*P(ILAMB, ITHETA, IFINE) +
& BSC*P(ILAMB, ITHETA, ICOARS) +
& BSR*PRAY( ITHETA) ) / BEXT(ILAMB)
SKY (I LAMB, ITHETA) = FS(ILAMB)/(4.*PI) * PBACK{ ILAMB, ITHETA)
CONTINUE
STEP 4: CALCULATE THE PLUME DIMENSIONS, CONCENTRATIONS, AND
OPTICAL THICKNESS FOR EACH OF THE LINES OF SIGHT
IVIEW = 1, IMAX+3
IHI = IMAX + 3
DO 550 IVIEW = l.IHI
;
STEP 4A: CALCULATE THE PLUME N02 CONCENTRATION RESULTING FROM
-------
** Page 15
< 714> C TITRATION WITH AMBIENT OZONE, ASSUMING THE PLUME IS
< 715> C UNIFORMLY SPREAD HORIZONTALLY IN A 22.5 DEGREE SECTOR.
< 716> C
< 717> XM = X(IVIEW) * 1000.
< 718> IF(XM.LT.100.) XM = 100.
< 719> C
< 720> C IF THE STABILITY IS 5 OR 6 (E OR F), WE ASSUME THAT SUCH
< 721> C CONDITIONS PERSIST FOR ONLY 12 HOURS. IF THE TRANSPORT TIME
< 722> C NECESSARY TO TRANSPORT IS LONGER, WE INCREASE WIND SPEED U SUCH
< 723> C THAT THE TRANSPORT TIME TO THE GIVEN DISTANCE IS EXACTLY 12
< 724> C HOURS. THIS IS AN APPROXIMATE WAY TO ACCOUNT FOR PERSISTENCE
< 725> C OF EXTREME CONDITIONS AND FOR THE SUBSEQUENT INCREASED DISPERSION
< 726> C AFTER 12 HOURS.
< 727> C
< 728> UNEW = U
< 729> IF(ISTAB.GT.4) THEN
< 730> TRANST = X(IVIEW)*1000./U/3600.
< 731> IF(TRANST.GT.12.) THEN
< 732> TRANST = 12.
< 733> UNEW » X(IVIEW)*1000./3600./TRANST
< 734> END IF
< 735> END IF
< 736> SZ = SZPAS(ISTAB,XM)
< 737> XNOX = QNOX*l.E6*5.315E-4/(SQRT2P*SZ*UNEW*TWOTAN*XM)
< 738> XNOX2 = XNOX
< 739> IF(XNOX.GT.03) XNOX2 - 03
< 740> IF(XNOX.EQ.O.) THEN
< 741> QNOX2 = 0.
< 742> ELSE
< 743> QNOX2 = XNOX2/XNOX*QNOX
< 744> END IF
< 745> C
< 746> C STEP 4B: CALCULATE THE OPTICAL THICKNESS
< 747> C
< 748> ALPHAP = ALPHA(IVIEW)
< 749> IF (ALPHAP.LT.5.) ALPHAP = 5.
< 750> DENOM = SQRT2P * SZ * UNEW * SIN(RAD * ALPHAP)
< 751> DO 550 ILAMB = 1,3
< 752> LAMB = LAMBDA(ILAMB)
< 753> SPART = QPART*BSCATV(IPART)/
< 754> & DPART*(LAMB/0.55)**(-NSCAT(IPART))
< 755> SS04 = QS04*BSCATV(IS04)/DS04*(LAMB/0.55)**(-NSCAT(IS04))
< 756> SSOOT = QSOOT*BSCATV(ISOOT)/DSOOT*(LAMB/0.55)**(-NSCAT(ISOOT))
< 757> SCAT = SPART + SS04 + SSOOT
< 758> ABSP = (QN02 + QNOX2) * BABSN(ILAMB) + QSOOT * 10.
< 759> PEXT = SCAT + ABSP
< 760> IF(PEXT.EQ.O.) THEN
< 761> OMEGA = 1.
< 762> ELSE
< 763> OMEGA = SCAT/PEXT
< 764> END IF
-------
**
Page 16
< 765> TAUPLU = PEXT / DENOM
< 766> C
< 767> C STEP 4C: CALCULATE THE VERTICAL ANGULAR SUBTENSE OF THE PLUME,
< 768> C PSI, AS VIEWED FROM THE GIVEN DISTANCE, RP.
< 769> C
< 770> PSI(IVIEW) = (l./RAD) * ATAN( 4.3 * SZ / (RP(IVIEW) * 1.E3))
< 771> C
< 772> C STEP 4D: CALCULATE THE THRESHOLD CONTRAST BY INTERPOLATING THE
< 773> C DATA OF HOWELL AND HESS (1978) FOR THE CALCULATED VALUE
< 774> C OF PSI.
< 775> J = 13
< 776> DO 520 I = 2,13
< 777> IF (PSI(IVIEW).LT.ANGLE(I)) THEN
< 778> J = I
< 779> GO TO 530
< 780> END IF
< 781> 520 CONTINUE
< 782>
< 783> 530 CONTINUE
< 784> C
< 785> PERTHR(IVIEW) - (PSI(IVIEW)-ANGLE(J-1))/(ANGLE(J)-ANGLE(J-1))
< 786> & * (CONT(J) - CONT(J-l)) + CONT(J-l)
< 787> C
< 788> C
< 789> C STEP 5: CALCULATE PLUME CONTRAST AGAINST SKY AND TERRAIN FOR
< 790> C BOTH FORWARD AND BACKWARD SCATTER CASES
< 791> C
< 792> DO 550 ITHETA = 1,MXANG
< 793> IF(SCAT.EQ.O.) THEN
< 794> PPLUME = 0.
< 795> ELSE
< 796> PPLUME = (SPART * P(ILAMB,ITHETA,IPART) +
< 797> & SS04 * P(ILAMB,ITHETA,IS04) +
< 798> & SSOOT * P(I LAMB,ITHETA,ISOOT)) /SCAT
< 799> END IF
< 800> C
< 801> C CONTRAST AGAINST SKY
< 802> C
< 803>
< 804> DCPLUM = (PPLUME*OMEGA/PBACK(I LAMB,ITHETA)-!.) *
< 805> & (1. - EXP(-TAUPLU)) * EXP(-BEXT(ILAMB)*RP(IVIEW)*1.E3)
< 806> IF (DCPLUM.GT.-FLCK .AND. DCPLUM.LT.FLCK) DCPLUM = 0.0
< 807> CPLUME(ILAMB,ITHETA,IVIEW) = FLOAT(DCPLUM)
< 808> C
< 809> C RADIANCE OF PLUME AGAINST SKY
< 810> C
< 811> PLUSKY(ILAMB,ITHETA,IVIEW) = (1. +
< 812> & CPLUME(ILAMB,ITHETA,IVIEW))*PBACK(ILAMB,ITHETA) *
< 813> & FS(ILAMB)/(4.*PI)
< 814> IF(PLUSKY(ILAMB,ITHETA,IVIEW).LT.O.)
< 815> & PLUSKY(ILAMB,ITHETA,IVIEW)=0.
-------
**
Page 17
< 816> C
< 817> C CONTRAST AGAINST TERRAIN -- SET TO MAX OF GREEN CONTRAST
< 818> C
< 819> C
< 820> DDELCR = EXP(-BEXT(ILAMB)*RO(IVIEW)*1.E3)*
< 821> & (1. - (EXP(-TAUPLU)X(l. + CPLUME(ILAMB,ITHETA,IVIEW))))
< 822> IF (DDELCR.GT.-FLCK .AND. DDELCR.LT.FLCK) DDELCR = 0.0
< 823> DELCR(ILAMB,ITHETA,IVIEW) = FLOAT(DDELCR)
< 824> C
< 825> C RADIANCE OF TERRAIN
< 826>
< 827> TERAIN(ILAMB,ITHETA,IVIEW) =* (l.-EXP(-BEXT(ILAMB)*
< 828> & RO(IVIEW)*1.E3))
< 829> & * PBACK(ILAMB,ITHETA) * FS(ILAMB)/(4.*PI)
< 830> IF (TERAIN(ILAMB,ITHETA,IVIEW).LT.O.)
< 831> & TERAIN(ILAMB,ITHETA,IVIEW)=0.
< 832> C
< 833> C RADIANCE OF PLUME AGAINST TERRAIN
< 834> PLUTER (ILAMB,ITHETA,IVIEW) = (l.-EXP(-BEXT(ILAMB)*
< 835> & RO(IVIEW)*1.E3) + DELCR(ILAMB,ITHETA,IVIEW)) *
< 836> & PBACK(ILAMB,ITHETA) * FS(ILAMB)/(4.* PI)
< 837> IF (PLUTER(ILAMB,ITHETA,IVIEW).LT.O.)
< 838> & PLUTER(ILAMB,ITHETA,IVIEW)=0.
< 839> 550 CONTINUE
< 840>
< 841> DO 570 IVIEW = 1, IHI
< 842> DO 570 ITHETA = 1, MXANG
< 843> DO 560 I LAMB = 1,3
< 844> SPECP(ILAMB) = PLUSKY(ILAMB,ITHETA,IVIEW)
< 845> SPECB(ILAMB) = SKY(ILAMB,ITHETA)
< 846> 560 CONTINUE
< 847> CALL CHROMA(SPECP,SPECB)
< 848> DELSKYfITHETA,IVIEW) = DELAB
< 849> DO 561 ILAMB = 1,3
< 850> SPECP(ILAMB) = (1. + PERTHR(IVIEW) ) * SKY(ILAMB,ITHETA)
< 851> 561 CONTINUE
< 852> CALL CHROMA(SPECP,SPECS)
< 853> THRSKY(ITHETA,IVIEW) = DELAB
< 854> IF (THRSKY(ITHETA,IVIEW).LT.THRESH)
< 855> & THRSKY(ITHETA,IVIEW) = THRESH
< 856> DO 565 ILAMB =1,3
< 857> SPECP(ILAMB) = PLUTER(ILAMB,ITHETA,IVIEW)
< 858> SPECB(ILAMB) = TERAINJILAMB,ITHETA,IVIEW)
< 859> 565 CONTINUE
< 860> CALL CHROMA(SPECP,SPECB)
< 861> DELTER(ITHETA,IVIEW) = DELAB
< 862> DO 567 ILAMB =1,3
< 863> SPECP(ILAMB) = (1.+PERTHR(IVIEW))*TERAIN(ILAMB,ITHETA,IVIEW)
< 864> 567 CONTINUE
< 865> CALL CHROMA(SPECP,SPECS)
< 866> THRTER(ITHETA,IVIEW) = DELAB
-------
** Page 18
< 867> IF (THRTER(ITHETA,IVIEW).LT.THRESH)
< 868> & THRTER(ITHETA,IVIEW) = THRESH
< 869> C
< 870> C SCREENING CRITERIA FOR GREEN CONTRAST
< 871> C
< 872> IF (PERTHR(IVIEW).LT.CGREEN) PERTHR(IVIEW) = CGREEN
< 873> C
< 874> 570 CONTINUE
< 876> C
< 877> C EVALUATION AND OUTPUT OF CALCULATED PLUME DELTA E AND CONTRAST
< 878> C
< 879> C IN THIS SECTION WE DETERMINE WHETHER ANY OF THE CALCULATED
< 880> C DELTA E OR CONTRAST VALUES ARE GREATER THAN SCREENING CRITERIA.
< 881> C RESULTS ARE SEGREGRATED BY WHETHER EFFECTS ARE VIEWED AGAINST
< 882> C A SKY OR A TERRAIN BACKGROUND AND WHETHER EFFECTS ARE CAUSED
< 883> C BY PLUME PARCELS LOCATED INSIDE OR OUTSIDE THE CLASS I AREA.
< 884> C
< 886> C
< 887> C STEP 1: DETERMINE WHETHER SCREENING THRESHOLD IS EXCEEDED AND
< 888> C WHERE. THIS IS DONE SEPARATELY FOR VIEWS AGAINST SKY
< 889> C AND TERRAIN AND FOR VIEWS OF PARCELS INSIDE OR OUTSIDE,
< 890> C
< 891> DO 580 IVIEW - 1, IHI
< 892> DO 580 ITHETA = 1, MXANG
< 893> OBJSKY(ITHETA,IVIEW) - ' '
< 894> OBJTER(ITHETA,IVIEW) = ' '
< 895> C
< 896> IF(DELSKY(ITHETA,IVIEW).GE.THRSKY(ITHETA,IVIEW))
< 897> & OBJSKY(ITHETA,IVIEW)(1:1) = '*'
< 898> CKGRN = ABS(CPLUME(2,ITHETA,IVIEW))
< 899> IF(CKGRN.GE.PERTHR(IVIEW))
< 900> & OBJSKY(ITHETA,IVIEW)(2:2) = '*'
< 901> C
< 902> IF(DELTER(ITHETA,IVIEW).GE.THRTER(ITHETA,IVIEW))
< 903> & OBJTER(ITHETA,IVIEW)(1:1) = '*'
< 904> CKGRN « ABS(DELCR(2,ITHETA,IVIEW))
< 905> IF(CKGRN.GE.PERTHR(IVIEW))
< 906> & OBJTER(ITHETA,IVJEW)(2:2) = '*'
< 907> C
< 908> 580 CONTINUE
< 909> DO 600 IVIEW = l.IHI
< 910> ICLASS = 2
< 911> IF((X(IVIEW).GE.XMIN).AND.(X(IVIEW).LE.XMAX)) ICLASS = 1
< 912> LSCLAS(IVIEW) = ICLASS
< 913> DO 600 ITHETA = 1, MXANG
< 914> C
< 915> C DELTA E CHECKS
< 916> RATIO = DELSKY(ITHETA,IVIEW)/THRSKY(ITHETA,IVIEW)
< 917> IF(DELSKY(ITHETA,IVIEW).GE.SKYMAX(ICLASS))
-------
** Page 19
< 918> & SKYMAX(ICLASS) = DELSKY(ITHETA,IVIEW)
< 919> IF(RATIO. GE. RATSKY(ICLASS)) THEN
< 920> ISKYMX(ICLASS) = IVIEW
< 921> RATSKY(ICLASS) = RATIO
< 922> END IF
< 923> RATIO = DELTER(ITHETA,IVIEW)/THRTER(ITHETA,IVIEW)
< 924> IF (DELTER(ITHETA,IVIEW).GE.TERMAX(ICLASS))
< 925> & TERMAX(ICLASS) = DELTER(ITHETA,IVIEW)
< 926> IF(RATIO. GE. RATTER(ICLASS)) THEN
< 927> ITERMX(ICLASS) = IVIEW
< 928> RATTER(ICLASS) = RATIO
< 929> END IF
< 930> C
< 931> C --NOW DO CONTRAST CHECKS
< 932> CKGRN = ABS(CPLUME(2,ITHETA,IVIEW))
< 933> RATIO = CKGRN/PERTHR(IVIEW)
< 934> IF(RATIO. GE. RATSCY(ICLASS)) THEN
< 935> ISCYMX(ICLASS) = IVIEW
< 936> RATSCY(ICLASS) = RATIO
< 937> END IF
< 938> CKGRN = ABS(DELCR(2,ITHETA,IVIEW))
< 939> RATIO = CKGRN/PERTHR(IVIEW)
< 940> IF(RATIO. GE. RATTRCJICLASS)) THEN
< 941> ITRCMX(ICLASS) = IVIEW
< 942> RATTRC(ICLASS) = RATIO
< 943> END IF
< 944> C
< 945> 600 CONTINUE
< 946> WRITE (*,610) SOURCE,RECEPT
< 947> 610 FORMAT(1X,///,IX,'OVERALL RESULTS OF PLUME VISIBILITY SCREENING',/
< 948> & /,IX,'SOURCE: ',A24,/,IX,'CLASS I AREA: '.A24/1X)
< 949> DO 700 ICLASS =1,2
< 950> WRITE (*,611) CLASSI(ICLASS)
< 951> 611 FORMAT (2X,A,' class I area --')
< 952> IF (RATSKY(ICLASS).GE.l.) THEN
< 953> WRITE (*,*) 'Plume delta E EXCEEDS screening criterion for ',
< 954> & 'SKY background'
< 955> ELSE
< 956> WRITE (*,*) 'Plume delta E DOES NOT EXCEED screening ',
< 957> & 'criterion for SKY background'
< 958> ENDIF
< 959> IF (RATTER(ICLASS).GE.l.) THEN
< 960> WRITE (*,*) 'Plume delta E EXCEEDS screening criterion for ',
< 961> & 'TERRAIN background'
< 962> ELSE
< 963> WRITE (*,*) 'Plume delta E DOES NOT EXCEED screening ',
< 964> & 'criterion for TERRAIN background'
< 965> ENDIF
< 966>
< 967> IF (RATSCY(ICLASS).GE.l.) THEN
< 968> WRITE (*,*)'Plume contrast EXCEEDS screening criterion for ',
-------
** Page 20
< 969>
< 970>
< 971>
< 972>
< 973>
< 974>
< 975>
< 976>
< 977>
< 978>
< 979>
< 980>
< 981>
< 982> 700
< 983 >
< 984>
< 985> 705
< 986>
< 987> C
< 988> C
< 989> C
< 990>
< 991>
< 992> C
< 993> C
< 994> C
< 995>
< 996> 710
< 997>
< 998>
< 999>
< 1000>
< 1001>
< 1002>
< 1003> 720
< 1004>
< 1005>
< 1006>
< 1007> 721
< 1008>
< 1009>
< 1010>
< 1011>
< 1012> 730
< 1013>
< 1014>
< 1015> 740
< 1016> 750
< 1017>
< 1018>
< 1019>
& 'SKY background'
ELSE
WRITE (*,*) 'Plume contrast DOES NOT EXCEED screening ',
& 'criterion for SKY background'
ENDIF
IF (RATTRC( ICLASS). GE.l.) THEN
WRITE (*,*)' Plume contrast EXCEEDS screening ',
& 'criterion for TERRAIN background'
ELSE
WRITE (*,*)' Plume contrast DOES NOT EXCEED screening ',
& 'criterion for TERRAIN background'
ENDIF
WRITE (*,*)' '
CONTINUE
WRITE (*,705) THRESH, CGREEN
FORMAT (1X/1X,' SCREENING CRITERIA: DELTA E - ',
& F4.1/3X,' GREEN CONTRAST = ',F5.3)
CALL REPORTING SUBROUTINE TO OUTPUT RESULTS
CALL SMRPT2 (I ERR)
CALL WRESLT (IHI.IERR)
rnNTTNIIP UTTH OUTPUT TO QPRPFN
------ l*Un 1 1NUC Him UU 1 ru 1 1 U oUrVL.L.M
WRITE (*,710)
FORMAT (lX/lX,'Do you want to see calculated results for lines ',
& 'of',/, IX, 'sight with maximum delta E (y/n)? '\)
CALL RESPND (1, IANS,RDUM,CSTR, IERR)
IF (IERR.NE.O) GO TO 999
IF(IANS.EQ.O) GO TO 805
WRITE (*,720)
WRITE (*,721)
FORMAT (IX, 'VIEW', 4X, 'ANGLES (DEGREES) ' ,7X, 'DIST (KM)',
& 2X,' PLUME PERCEPTIBILITY DELTA E(L*A*B*)7
& 2X, 'no', 6X, 'phi', 2X, 'alpha', 3X, 'psi ' ,5X, ' x ',3X,'rp',
& 6X,' forward ',2X,' backward')
FORMAT (IX,' ',5X, '---',
&9 Y ' ' "3 Y ' ' £ Y ' ' 4. Y ' 'QY' ' flY
£ A ) •. — — — j J A j - — — ^ 0 A j j H A ) y 7 A ) 9 OA )
9. I > \
* /
DO 800 ICLASS =1,2
WRITE (*,730)
FORMAT(5X,/,lX,'Line of sight with maximum perceptibility for ',
& 'plume viewed ')
WRITE (*,740) CLASSI( ICLASS)
FORMAT(10X, 'against a SKY background ',A7,' class I area.')
FORMAT(10X, 'against a TERRAIN background ',A7,' class I area.')
I = ISKYMX( ICLASS)
WRITE (*,760) I, PHI(I), ALPHA(I), PSI(I), X(I), RP(I),
& DELSKY(1,I),OBJSKY(1,I)(1:1),DELSKY(2,I),OBJSKY(2,I)(1:1)
-------
**
Page
21
1020> 760
1021>
1022>
1023>
1024>
1025>
1026> 800
1027>
1028> 809
1029>
1030> 805
1031>
1032> 810
1033>
1034>
1035>
1036>
1037>
1038>
1039>
1040> 815
1041>
1042>
1043> 820
1044>
1045>
1046>
1047>
1048>
1049>
1050>
1051>
1052>
1053> 830
1054>
1055>
1056>
1057>
1058>
1059>
1060>
1061>
1062>
1063>
1064> 850
1065>
1066>
1067>
1068>
1069>
1070>
FORMAT(2X,I2,2X,2F7.1,F7.2,2F7.1,6X,F7.1,1X,A1,7X,F7.1,1X,A1)
WRITE (*,730)
WRITE (*,750) CLASSI(ICLASS)
I = ITERMX(ICLASS)
WRITE (*,760) I, PHI(I), ALPHA(I), PSI(I),X(I), RP(I),
& DELTER(1,I),OBJTER(1,I)(1:1),DELTER(2,I),OBJTER(2,I)(1:1)
CONTINUE
WRITE (*,809)
FORMAT(1X,' '/2X,'* Exceeds screening criteria')
CONTINUE
WRITE (*,810)
FORMAT(lX/lX/Do you want to see calculations for all',
& ' lines of sight (y/n)? '\ )
CALL RESPND (1,IANS,RDUM,CSTR,IERR)
IF (IERR.NE.O) GO TO 999
IF(IANS.EQ.O) GO TO 900
ICOUNT = 1
RAST = IMAX + 3
CONTINUE
IHIGH = 0
CONTINUE
ROW = IHIGH + 1
IHIGH = ROW + 17
IF (IHIGH.GT.RAST) IHIGH = RAST
IF(ICOUNT.EQ.l) THEN
WRITE (*,*) ' '
WRITE (*,830) 'PLUME DELTA E AGAINST A SKY BACKGROUND'
ELSE
WRITE (*,*) ' '
WRITE (*,830) 'PLUME DELTA E AGAINST A TERRAIN BACKGROUND'
FORMAT (1X,A60)
END IF
WRITE (*,720)
DO 850 I = ROW, IHIGH
IF(ICOUNT.EQ.l) THEN
WRITE (*,760) I, PHI(I), ALPHA(I), PSI(I), X(I), RP(I),
& DELSKY(1,I),OBJSKY(1,I)(1:1),DELSKY(2,I),OBJSKY(2,I)(1:1)
ELSE
WRITE (*,760) I, PHI(I), ALPHA(I), PSI(I),X(I), RP(I),
& DELTER(1,I),OBJTER(1,I)(1:1),DELTER(2,I),OBJTER(2,I)(1:1)
END IF
CONTINUE
WRITE (V(A\)')' Please press [ENTER] for more, Q to quit',
& ' '
CALL RESPND (5,IANS,RDUM,CSTR,IERR)
IF (IERR.NE.O) GO TO 999
IF (IANS.EQ.2) GO TO 900
IF (IHIGH.LT. RAST) GO TO 820
-------
** Page 22
C
C
1071>
1072>
1073>
1074>
1075> C
1076> 900
1077> C
1078>
1079>
1080>
1081>
1082>
1083> 5000
1084>
1085>
1086>
1087>
1088>
1089>
1090>
1091>
1092>
1093>
1094>
1095>
1096> 6000
1097>
1098> 7100
1099>
1100>
7200
1102>
1103>
1104>
1105>
1106>
1107>
1108>
1109>
< 1113> 7300
1116> 7400
1117> 7500
1120>
ICOUNT = ICOUNT + 1
IF (ICOUNT.EQ.3) GO TO 900
GO TO 815
CONTINUE
DISPLAY CONTRAST VALUES THIS TIME RATHER THAN DELTA E
DO 5000 1-1,2
SKYMAX(I) * 0.
TERMAX(I) * 0.
CONTINUE
DO 6000 IVIEW = l.IHI
ICLASS = LSCLAS(IVIEW)
DO 6000 ITHETA = l.MXANG
DO 6000 I LAMB -1,3
IF(ABS(CPLUME(ILAMB,ITHETA,IVIEW)).GE.SKYMAX(ICLASS)) THEN
SKYMAX(ICLASS) - ABS(CPLUME(ILAMB,ITHETA,IVIEW))
ISKYMX(ICLASS) - IVIEW
END IF
IF (ABS(DELCR(ILAMB,ITHETA,IVIEW)).GE.TERMAX(ICLASS)) THEN
TERMAX(ICLASS) - ABS(DELCR(ILAMB,ITHETA,IVIEW))
ITERMX(ICLASS) = IVIEW
END IF
CONTINUE
WRITE (*,7100)
FORMAT(lX,///,lX,'Do you want to see calculated results for',
& ' lines of',/,IX,'sight with maximum green contrast? (y/n) '\)
CALL RESPND (1,IANS,RDUM,CSTR,IERR)
IF (IERR.NE.O) GO TO 999
IF(IANS.EQ.O) GO TO 8050
FORMAT(48X,'-GREEN PLUME CONTRAST-'/1X,'VIEW',5X,
&'ANGLES',8X,'DISTANCES (KM)',11X,'forward',6X,'backward',IX,
& 'screening'/2X,'no',5X,'phi',2X,'alpha',4X,' x ',
& 4X,'rp',5X,'ro',8X,'contrast' ,5X,'contrast',IX,'criterion'/
a i y /_ / j y / _/ py ' ___' dy ' ' 4Y ' ' 5Y '--'
&OY ' ' CY ' ' 1Y ' ' 1
OA, - , 3 A , - ,1A, J
WRITE (*,7200)
DO 8000 ICLASS -1,2
WRITE (*,7300)
FORMAT(5X,/,lX,'Line of sight with maximum contrast for plume',
& ' viewed')
WRITE (*,7400) CLASSI(ICLASS)
FORMAT(10X,'against a SKY background ',A7
FORMAT(10X,'against a TERRAIN background
I = ISCYMX(ICLASS)
WRITE (*,7600) I, PHI(I), ALPHA(I), X(I), RP(I), RO(I),
& CPLUME(2,1,I),OBJSKY(1,I)(2:2),CPLUME(2,2,I),
& OBJSKY(2,I)(2:2),PERTHR(I)
' class I area.')
,A7,' class I area.')
-------
**
Page
23
1122> 7600
1123>
1124>
1125>
1126>
1127>
1128>
1129> 8000
1130>
1131> 8090
1132>
1133> C
1134> 8050
1135>
1136> 8100
1137>
1138>
1139>
1140>
1142>
1143>
1144> 8150
1145>
1146>
1147>
1148>
1149>
1150>
8200
1152>
1153>
1154>
1155> 8300
1156>
1157>
1158>
1159>
1160>
1162>
1163>
1164>
1165>
1166>
1167>
1168>
1169>
1170>
FORMAT(2X,I2,2X,5F7.1,6X,F7.3,1X,A1,4X,F7.3,1X,A1,2X,F6.2)
WRITE (*,7300)
WRITE (*,7500) CLASSI(ICLASS)
I = ITRCMX(ICLASS)
WRITE (*,7600) I, PHI(I), ALPHA(I), X(I), RP(I), RO(I),
& DELCR(2,1,I),OBJTER(1,I)(2:2),DELCR(2,2,I),OBJTER(2,I)(2:2),
& PERTHR(I)
CONTINUE
WRITE (*,8090)
FORMAT (IX,' - '/2X,'* Absolute ',
& 'value exceeds screening criteria')
CONTINUE
WRITE (*,8100)
FORMAT(1X,/1X,' Do you want to see green contrast values for all',
& ' lines of sight (y/n)? '\)
CALL RESPND (1,IANS,RDUM,CSTR,IERR)
IF (IERR.NE.O) GO TO 999
IF(IANS.EQ.O) GO TO 9000
ICOUNT = 1
I LAST = IMAX + 3
CONTINUE
IHIGH = 0
CONTINUE
ROW = IHIGH + 1
IHIGH = ILOW + 17
IF(IHIGH.GT.ILAST) IHIGH = ILAST
IF( ICOUNT. EQ.l) THEN
WRITE (*,8300) 'PLUME CONTRAST AGAINST A SKY BACKGROUND'
ELSE
WRITE (*,8300) 'PLUME CONTRAST AGAINST A TERRAIN BACKGROUND'
FORMAT (1X//1X,A60)
END IF
WRITE (*,7200)
DO 8500 I = ILOW, IHIGH
IF( ICOUNT. EQ.l) THEN
WRITE (*,7600) I, PHI(I), ALPHA(I), X(I), RP(I), RO(I),
CPLUME(2,1,I),OBJSKY(1,I)(2:2),CPLUME(2,2,I),
OBJSKY(2,I)(2:2),PERTHR(I)
ELSE
WRITE (*,7600) I, PHI(I), ALPHA(I), X(I), RP(I), RO(I),
& DELCR(2,1,I),OBJTER(1,I)(2:2),DELCR(2,2,I),
& OBJTER(2,I)(2:2),PERTHR(I)
END IF
8500 CONTINUE
WRITE (V(A\)')' When you"re ready, please press [ENTER] for ',
& ' more lines of sight (Q to quit)'
CALL RESPND (5,IANS,RDUM,CSTR,IERR)
1172> IF (IERR.NE.O) GO TO 999
-------
**
Page
24
1173>
1174>
1175>
1176>
1177>
1178> C
1179> 9000
1180>
1181> 910
1182>
1183>
1184>
1185>
1186>
1187>
1188>
1189>
1190>
1191> 915
1192> 920
1193> 930
1194> 940
1195>
1196> 950
1197>
1198>
1199>
1200>
1201>
1202>
1203>
1204>
1205>
1206>
1207>
1208>
1209>
1210>
1211> 1000
1212>
1213>
1214>
1215>
1216>
1217>
1218>
1219> 999
1220>
1221> CDECK
1222> C
1223>
IF (IANS.EQ.2) GO TO 9000
IF(IHIGH.LT.ILAST) GO TO 8200
I COUNT = I COUNT + 1
IF(ICOUNT.EQ.3) GO TO 9000
GO TO 8150
CONTINUE
WRITE (*,910)
FORMAT(lX,//,lX,'Do you want to quit (y/n)? '\)
CALL RESPND (1,IANS,RDUM,CSTR, IERR)
IF (IERR.NE.O) GO TO 999
IF(IANS.EQ.l) GO TO 1000
LFIRST = 0
DO 915 I = 1,2
SKYMAX(I) = 0.
TERMAX(I) - 0.
RATSKY(I) - 0.
RATTER(I) = 0.
CONTINUE
FORMAT(lX,//,lX,'Do you want to change emissions? (y/n)'\)
FORMAT(lX,//,lX,'Do you want to change distances? (y/n)'\)
FORMAT(lX,//,lX,'Do you want to change particle sizes or ',
& 'densities? (y/n)'\)
FORMAT(lX,//,lX,'Do you want to change meteorology? (y/n)'\)
WRITE (*,920)
CALL RESPND (1,IEMISS,RDUM,CSTR, IERR)
IF (IERR.NE.O) GO TO 999
WRITE (*,930)
CALL RESPND (1,IDIST,RDUM,CSTR,IERR)
IF (IERR.NE.O) GO TO 999
WRITE (*,940)
CALL RESPND (1, IPAR,RDUM,CSTR,IERR)
IF (IERR.NE.O) GO TO 999
WRITE (*,950)
CALL RESPND (1,IMET,RDUM,CSTR,IERR)
IF (IERR.NE.O) GO TO 999
GO TO 10
CONTINUE
WRITE (* *) ' *******************'
WRITE (* *)' '
WRITE (* *) ' VISCREEN summary report file is: MPSMRY
WRITE (* *) ' VISCREEN results file is: ',IPLTUS
WRITE (**)''
WRITE (**)''
WRITE /* *\ ' ********************
STOP
END
SZPAS
FUNCTION SZPAS(I,X)
-------
**
Page 25
1224>
1225>
1226>
1227>
1228>
1229>
1230>
1231>
1232>
1233>
1234>
1235>
1236>
1237>
1238>
1239>
1240>
1241>
1242>
1243>
1244>
1245>
1246>
1247>
1248>
1249>
1250>
1251>
1252>
1253>
1254>
1255>
1256>
1257>
1258>
1259>
1260>
1261>
1262>
1263>
1264>
1265>
1266>
1267>
1268>
1269>
1270>
1271>
1272>
1273>
1274>
SAVE
C
C PASQUILL-GIFFORD VERTICAL DISPERSION COEFFICIENT (SIGMA Z).
C
REAL A(7),B(7),C(7),D(7),LOGX
DATA A/1.157,-.031027,-.0045741,.011157,-.0005092,.0037608,O./
DATA B/2.815,.050674,.0040771,-.093465,-.10332,-.12889,O./
DATA C/3.316,1.0827,.92084,.72583,.67969,.65602,O./
DATA D/2.804,2.0327,1.7824,1.4901,1.3284,1.1391,0./
IF(I.EQ.7) GO TO 1
LOGX=ALOG10(X/1000.)
SZPAS=10.**(A(I)*LOGX*LOGX*LOGX+B(I)*LOGX*LOGX+C(I)*LOGX+D(I))
RETURN
1 LOGX=ALOG10(X)
SZPAS=10.**(-.0086351*LOGX*LOGX*LOGX-.036447*LOGX*LOGX+1.1243*LOGX
1 -1.8981)
RETURN
END
CDECK CHROMA
C
SUBROUTINE CHROMA(SPECB,SPECR)
SAVE
£*****
C***** CALCULATES VARIOUS COLORATION PARAMETERS SUCH AS CHROMA-
C***** TICITY COORDINATES,LUMINANCE,VALUE, AND DELTA E.
£*****
COMMON/COLOR/DELAB,
1XBAR(3),YBAR(3),ZBAR(3)
COMMON/REF/XCAPO,YCAPO,ZCAPO
DIMENSION SPECB(3),SPECR(3)
XCAP=0.
YCAP=0.
ZCAP=0.
XCAPR=0.
YCAPR=0.
ZCAPR=0.
DO 10 1=1,3
XCAP=XCAP+SPECB(I)*XBAR(I)
YCAP=YCAP+SPECB(I)*YBAR(I)
ZCAP=ZCAP+SPECB(I)*ZBAR(I)
XCAPR=XCAPR+SPECR(I)*XBAR(I)
YCAPR=YCAPR+SPECR(I)*YBAR(I)
ZCAPR=ZCAPR+SPECR(I)*ZBAR(I)
10 CONTINUE
VAL=116.*(YCAP/YCAPO)**.333-16.
VALR=116.*(YCAPR/YCAPO)**.333-16.
ASTAR=500.*((XCAP/XCAPO)**.333-(YCAP/YCAPO)**.333)
ASTARR=500.*((XCAPR/XCAPO)**.333-(YCAPR/YCAPO)**.333)
-------
**
Page
26
1275>
1276>
1277>
1278>
1279>
1280>
1281>
1282>
1283>
1284>
1285>
1286>
1287>
1288>
1289>
1290>
1291>
1292>
1293>
1294>
1295>
1296>
1297>
1298>
1299>
1300>
1301>
1302>
1303>
1304>
1305>
1306>
1307>
1308>
1309>
1310>
BSTAR=200.*((YCAP/YCAPO)**.333-(ZCAP/ZCAPO)**.333)
BSTARR=200.*((YCAPR/YCAPO)**.333-(ZCAPR/ZCAPO)**.333)
VALD=VAL-VALR
ASTARD=ASTAR-ASTARR
BSTARD=BSTAR-BSTARR
DELAB=SQRT(VALD*VALD+ASTARD*ASTARD+BSTARD*BSTARD)
RETURN
END
CDECK BLOCK DATA
C
BLOCK DATA
COMMON/COLOR/DELAB,
1 XBAR(3),YBAR(3),ZBAR(3)
COMMON/REF/XCAPO,YCAPO,ZCAPO
DATA XBAR/0.1196, 0.6317, 0.1838/
DATA YBAR/0.0935, 0.8229, 0.0753/
DATA ZBAR/0.7012, 0.0159, O.OOOO/
DATA XCAPO,YCAPO,ZCAPO/3*0./
END
CDECK INIT
SUBROUTINE INIT (IERR)
SAVE
SET VALUES FOR SOME COMMON BLOCK VARIABLES
1312>
1313>
1314>
1315>
1316>
1317>
1318>
1319>
1320>
1321>
1322>
1323>
1324>
1325>
COMMON /IO/ ITERM,ISMRY,ILOTUS
COMMON /COMR/ ALPHA(39), BABS,BEXT(3),
& CPLUME(3,2,39), DELCR(3,2,39), DIST, GAMMA,
& 03, P(3,2,9), PHI(39), RP(39), RV, TAU, X(39),
& U,OMEGA,XMIN,XMAX,DFINE,DCOARS,OPART,DSOOT,DS04,
& SKYMAX(2),TERMAX(2),THRESH,CGREEN,
& QPARTI,QPART,QNOXI,QNOX,QN02I,QN02,QSOOTI,QSOOT,QS04I,
& QS04,RO(39),PRAY(2),PBACK(3,2),SCTANG(2),SKY(3,2),
& TERAIN(3,2,39),PLUSKY(3,2,39),PLUTER(3,2,39),DELSKY(2,39),
& DELTER(2,39),SPECB(3),SPECP(3),
& PSI(39),PERTHR(39),THRSKY(2,39),THRTER(2,39),RATIO,
& RATSKY(2),RATTER(2)
COMMON /COMI/ ISIZE,ISTAB,ITHETA,IFINE,ICOARS,IPART,ISOOT,
& IS04,ISKYMX(2),ITERMX(2),IANS,IEMISS,IDIST,IPAR,IMET,
& L1DFLT,LSCLAS(39),MXANG,MXLOS,IMASS,ITIME,
& LMDFLT,LPDFLT,LTDFLT
COMMON /COMC/ MASS,TIME,SOURCE,RECEPT,CLASSI,OBJSKY,OBJTER
CHARACTER*2 OBJSKY(2,39),OBJTER(2,39)
CHARACTER*3 MASS(5),TIME(5)
CHARACTER*7 CLASSI(2)
CHARACTER*24 SOURCE,RECEPT
-------
**
Page
27
< 1326> C
s T?97s r
< 1328> C
< 1329>
<• Tigris r
V 13-J\JS U
< 1331> C
< 1332>
< 1333>
< 1334>
< 1335>
< 1336>
< 1337> C
< 1338>
< 1339>
< 1340>
< 1341>
< 1342> C
< 1343> C
< 1344> C
< 1345>
< 1346>
< 1347>
< 1348>
< 1349>
< 1350>
< 1351>
< 1352>
< 1353>
< 1354>
< 1355> C
* TJRfis r
x 1 03U>>? \f
< 1357> C
< 1358>
< 1359>
< 1360>
< 1361>
< 1362> C
< 1363>
< 1364>
< 1365>
< 1366>
< 1367>
< 1368> 10
< 1369> C
< 1370> C
< 1371> C
< 1372>
< 1373>
< 1374>
< 1375>
< 1376> C
IERR = -1
THF^F ^Hnill 1
ITERM = 1
ISMRY = 7
I LOTUS = 8
MXANG = 2
MXLOS = 39
IEMISS = 1
IDIST = 1
IPAR = 1
IMET = 1
SET DEFAULT
DFINE = 1.5
IFINE = 3
DCOARS =2.5
ICOARS = 8
DPART =2.5
I PART = 6
DSOOT =2.0
I SOOT = 1
DS04 =1.5
IS04 = 4
CCT nFFAIII T
oC 1 UtTHUL 1
03 = 0.04
U - 1.
I STAB = 6
GAMMA = 11.25
DO 10 I = 1, 2
SKYMAX(I) = 0.
TERMAX(I) = 0.
RATSKY(I) = 0.
RATTER(I) = 0.
CONTINUE
SET DEFAULT
THRESH =2.0
CGREEN =0.05
SCTANG(l) = 10.
SCTANG(2) = 140.
DRFAI 1 Y RF PARAMFTFR9
r\LMLL. T DC rnrVHrlL 1 Cr\o
PARTICLES CHARACTERISTICS
MFT Awn RArkT^pniiNn n?nwF
DC 1 MMU Dn^M3t\UUIlU \JL\J\\L.
THRESHOLDS AND SCATTER ANGLES
-------
**
Page
28
< 1377> C
< 1378> C
< 1379>
< 1380>
< 1381>
< 1382>
< 1383>
< 1384>
< 1385>
< 1386>
< 1387>
< 1388>
< 1389> C
< 1390>
< 1391>
< 1392> C
< 1393>
< 1394> C
< 1395> C
< 1396> C
< 1397> 999
< 1398>
< 1399> CDECK
< 1400> C
< 1401>
< 1402>
< 1403> C
< 1404> C
< 1405> C
< 1406> C
< 1408> C
< 1409>
< 1410>
< 1411>
< 1412>
< 1413>
< 1414>
< 1415>
< 1416>
< 1417>
< 1418>
< 1419>
< 1420>
< 1421> C
< 1423> C
< 1424>
< 1425> C
< 1426>
< 1427>
SET LABELS
MASS(l) = 'G'
MASS(2) = 'KG'
MASS(3) = 'MT'
MASS(4) = 'LB'
MASS(5) = 'TON'
TIME(l) = 'S'
TIME(2) = 'MIN'
TIME(3) = 'HR'
TIME(4) = 'DAY'
TIMEJ5) = 'YR'
CLASSI(l) - 'INSIDE'
CLASSI(2) = 'OUTSIDE'
IERR = 0
RETURN
END
INIT2
SUBROUTINE INIT2 (IERR)
SAVE
REINIT SOME IMPORTANT RESULTS ARRAYS
COMMON /COMR/ ALPHA (39), BABS,BEXT(3) ,
& CPLUME(3,2,39), DELCR(3,2,39) , DIST, GAMMA,
& 03, P(3,2,9), PHI(39J, RP(39), RV, TAU, X(39),
& U, OMEGA, XMIN,XMAX,DFINE,DCOARS,DPART,DSOOT,DS04,
& SKYMAX(2) ,TERMAX(2) , THRESH, CGREEN,
& QPARTI,QPART,QNOXI,QNOX,QN02I,QN02,QSOOTI,QSOOT,QS04I,
& QS04,RO(39),PRAY(2),PBACK(3,2),SCTANG(2),SKY(3,2),
& TERAIN(3,2,39),PLUSKY(3,2,39),PLUTER(3,2,39),DELSKY(2,39),
& DELTER(2,39),SPECB(3),SPECP(3),
& PSI(39),PERTHR(39),THRSKY(2,39),THRTER(2,39),RATIO,
& RATSKY(2),RATTER(2)
COMMON /CRGI/ LFIRST,ISCYMX(2) ,RATSCY(2) , ITRCMX(2) ,RATTRC(2)
IERR = -1
DO 10 I - 1, 2
SKYMAX(I) = -1.
-------
** Page 29
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1477>
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10
C
C
C
999
TERMAX(I) = -1.
RATSKY(I) = -1.
RATTER(I) = -1.
RATSCY(I) = -1.
RATTRC(I) = -1.
CONTINUE
IERR = 0
RETURN
END
CDECK OPENA
C
SUBROUTINE OPENA (IERR)
SAVE
C
C OPEN OUTPUT FILES FOR VISCREEN PROGRAM
C
£************************************************************************
C
COMMON /IFL/ IPSMRY,IPLTUS
COMMON /IO/ ITERM,ISMRY,ILOTUS
C
LOGICAL LFLAG
CHARACTERMO IPSMRY, IPLTUS
CHARACTER*2 IVAL
CHARACTER*40 CSTR
C
£********************+******+**********************************************
C
IERR = -1
C
C SUMMARY REPORT FILE
C
100
CONTINUE
WRITE (*,*) 'Path &
WRITE (V(A,A\)')
file name for Summary Report'
(max 40 characters including file name &',
& ' extension): '
READ (*,1000) IPSMRY
INQUIRE (FILE=IPSMRY,EXIST=LFLAG)
IF (LFLAG) THEN
WRITE (V(A\)') ' File Exists, do you want to overwrite it?
CALL RESPND (1,IYES.RNUM,CSTR,IERR)
IF (IYES.EQ.O) GO TO 100
OPEN (ISMRY,FILE=IPSMRY,STATUS='OLD')
ENDFILE ISMRY
REWIND ISMRY
ELSE
OPEN (ISMRY,FILE=IPSMRY,STATUS='NEW')
ENDIF
-------
**
Page
30
< 1479> C
< 1480> C
< 1481> C
< 1482> 200
< 1483>
< 1484>
< 1485>
< 1486>
< 1487>
< 1488>
< 1489>
< 1490>
< 1491>
< 1492>
< 1493>
< 1494>
< 1495>
< 1496>
< 1497>
< 1498>
< 1499> C
< 1500>
< 1501> C
< 1502> C
< 1503> C
< 1504>
< 1505> 1000
< 1506>
< 1507> CDECK
< 1508> C
< 1509>
< 1510>
< 1511> C
< 1512> C
s 1 CI-JN r
V 1 3 1 J^ O
< 1514> C
< 1515> C
< 1516> C
< 1517> C
< 1518> C
< 1519> C
< 1520> C
< 1521> C
< 1522> C
< 1523> C
< 1524> C
< 1525> C
< 1526> C
< 1527> C
< 1528> C
< 1529> C
INPUT AND LOTUS FORMAT RESULTS FILE
CONTINUE
WRITE (*,*) ' '
WRITE (*,*) 'Path & file name for Results Output'
WRITE (V(A,A\)') ' (max 40 characters including file name & '
& 'extension): '
READ (*,1000) IPLTUS
INQUIRE (FILE=IPLTUS,EXIST=LFLAG)
IF (LFLAG) THEN
WRITE (*,'(A\)') ' File Exists, do you want to overwrite it?
CALL RESPND (1,IYES,RNUM,CSTR,IERR)
IF (IYES.EQ.O) GO TO 200
OPEN ( I LOTUS , F I LE- 1 PLTUS , STATUS= ' OLD ' )
ENDFILE I LOTUS
REWIND ILOTUS
ELSE
OPEN ( ILOTUS, FILE=IPLTUS,STATUS='NEW')
END IF
IERR - 0
RETURN
FORMAT (40A)
END
RESPND
SUBROUTINE RESPND (IFLAG, INUM,RNUM,CSTR,IERR)
SAVE
ficj IICCD DCCpnKKF FROM THF TFRMTNAI
uul UOCr\ fxuOrUliOC ri\UI" Int. ICixrllliML
TRAPPING ERRORS AS WE GO
ARGUMENTS:
IFLAG I RESPONSE TYPE FLAG
= 1 YES/NO
= 2 INTEGER
= 3 REAL
= 4 CHARACTER STRING
= 5 QUITTING ?
INUM I INTEGER RETURNED ARG FOR IFLAG =0,1
NUMERIC INTEGER OR
= 0 NO FOR IFLAG = 0
= 1 YES
= 2 QUIT, YES I WANT TO
RNUM R REAL RETURNED ARG
CSTR C CHARACTER RETURNED ARG
-------
**
Page
31
C
C
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1531> C
1532> C
1533> C
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1537> C
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1545> C
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1547>
1548>
1549>
1550>
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1552>
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1556> C
1557> C
1558> C
1559> 100
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1576>
1577> 200
1578>
1579>
1580>
IERR I ERROR FLAG RETURNED
= 0 OKEY-DOKEY
< 0 OPPS OF SOME KIND
C
C
C
COMMON /IO/ ITERM,ISMRY,ILOTUS
REAL RNUM
INTEGER INUM,IFLAG,IERR,ICNT,MXERR
CHARACTER CSTR*40,YESNO*3
DATA MXERR / 3 /
BRANCH ON RESPONSE TYPE WANTED
ICNT = 0
IERR = -1
IF (IFLAG.EQ.l) GO TO 100
IF (IFLAG.EQ.2) GO TO 200
IF (IFLAG.EQ.3) GO TO 300
IF (IFLAG.EQ.4) GO TO 400
IF (IFLAG.EQ.5) GO TO 500
GO TO 999
YESNO ANSWER
CONTINUE
INUM = 0
READ (*,'(3A)',ERR=910) YESNO
IF (YESNO(lrl).EQ.'Y' .OR. YESNO(l:l).EQ.'y') THEN
INUM = 1
IERR = 0
GO TO 999
ELSE
IF (YESNO(1:1).EQ.'N' .OR. YESNO(l:l).EQ.'n') THEN
INUM = 0
IERR = 0
GO TO 999
ENDIF
ENDIF
GO TO 910
INTEGER RESPONSE
CONTINUE
READ (*,*,ERR=920) INUM
IERR = 0
GO TO 999
-------
**
Page 32
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1582> C
1583> C
1584> 300
1585>
1586>
1587>
1588> C
1589> C
1590> C
1591> 400
1592>
1593>
1594>
1595> C
1596> C
1597> C
1598> 500
1599>
1600>
1601>
1602>
1603>
1604>
1605>
1606>
1607>
1608> C
1609> C
1610> C
1611> 910
1612>
1613>
1614>
1615> C
1616> 920
1617>
1618>
1619>
1620> C
1621> 930
1622>
1623>
1624>
1625> C
1626> 940
1627>
1628>
1629>
1630> C
1631> 950 ICNT = ICNT + 1
REAL RESPONSE
CONTINUE
READ (*,*,ERR=930) RNUM
IERR = 0
GO TO 999
CHARACTER STRING INPUT
CONTINUE
READ (*/(40A)',ERR=940) CSTR
IERR = 0
GO TO 999
IS HE A QUITER
CONTINUE
INUM = 0
READ (V(3A)',ERR-910) YESNO
IF (YESNO(lrl).EQ.'Q' .OR. YESNO(1:1).EQ.'q') THEN
INUM - 2
IERR = 0
GO TO 999
END IF
IERR = 0
GO TO 999
ERROR MESSAGES
ICNT = ICNT + 1
IF (ICNT.GT.MXERR) GO TO 999
WRITE (V(A\)') ' Please answer Y or N: '
GO TO 100
ICNT = ICNT + 1
IF (ICNT.GT.MXERR) GO TO 999
WRITE (*,'(A\)') ' Error...Please re-enter number: '
GO TO 200
ICNT = ICNT + 1
IF (ICNT.GT.MXERR) GO TO 999
WRITE (*,'(A\)') ' Error...Please re-enter number: '
GO TO 300
ICNT = ICNT + 1
IF (ICNT.GT.MXERR) GO TO 999
WRITE (V(A\)') ' Illegal character string, Try again:
GO TO 400
-------
**
Page
33
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1677>
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1679>
1680>
1681>
1682>
IF (ICNT.GT.MXERR) GO TO 999
WRITE (V(A\)') ' Enter Q to quit:
GO TO 400
999 RETURN
END
CDECK SMRPT1
C
SUBROUTINE SMRPT1 (IERR)
SAVE
SUBROUTINE OUTPUTS HEADER & INPUT RECORDS FOR
THE SUMMARY REPORT
COMMON /IO/ ITERM,ISMRY,ILOTUS
COMMON /COMR/ ALPHA(39), BABS,BEXT(3),
& CPLUME(3,2,39), DELCR(3,2,39), DIST, GAMMA,
& 03, P(3,2,9), PHI(39), RP(39), RV, TAU, X(39),
& U,OMEGA,XMIN,XMAX,DFINE,DCOARS,DPART,DSOOT,DS04,
& SKYMAX(2),TERMAX(2),THRESH,CGREEN,
& QPARTI,QPART,QNOXI,QNOX,QN02I,QN02,QSOOTI,QSOOT,QS04I,
& QS04,RO(39),PRAY(2),PBACK(3,2),SCTANG(2),SKY(3,2),
& TERAIN(3,2,39),PLUSKY(3,2,39),PLUTER(3,2,39),DELSKY(2,39),
& DELTER(2,39),SPECB(3),SPECP(3),
& PSI(39),PERTHR(39),THRSKY(2,39),THRTER(2,39),RATIO,
& RATSKY(2),RATTER(2)
COMMON /COm/ ISIZE,ISTAB,ITHETA,IFINE,ICOARS,IPART,ISOOT,
& IS04,ISKYMX(2),ITERMX(2),IANS,IEMISS,IDIST,IPAR,IMET,
& L1DFLT,LSCLAS(39),MXANG,MXLOS,IMASS,ITIME,
& LMDFLT,LPDFLT,LTDFLT
COMMON /COMC/ MASS,TIME,SOURCE,RECEPT,CLASSI,OBJSKY,OBJTER
CHARACTER*2 OBJSKY(2,39),OBJTER(2,39)
CHARACTER*3 MASS(5),TIME(5)
CHARACTER*? CLASS I(2)
CHARACTER*24 SOURCE,RECEPT
C
Q**********************************************************
C
C TABLE A
C
WRITE (ISMRY,1000) SOURCE,RECEPT
1000 FORMAT (/15X,'Visual Effects Screening Analysis for'/
& 15X,' Source: ',A/
& 15X,' Class I Area: ',A)
IF (L1DFLT.EQ.1) THEN
WRITE (ISMRY.1001)
ELSE
WRITE (ISMRY.1002)
ENDIF
-------
**
Page 34
< 1683> 1001 FORMAT (//15X,' *** Level-1 Screening ***')
< 1684> 1002 FORMAT (//15X,'*** User-selected Screening Scenario Results ***')
< 1685> C
< 1686> C TABLE B
< 1687> C
< 1688> WRITE (ISMRY,*)'Input Emissions for '
< 1689> WRITE (ISMRY,1010) QPARTI,MASS(IMASS),TIME(ITIME),
< 1690> & QNOXI,MASS(IMASS),TIME(ITIME),
< 1691> & QN02I,MASS(IMASS),TIME(ITIME),
< 1692> & QSOOTI,MASS(IMASS),TIME(ITIME),
< 1693> & QS04I,MASS(IMASS),TIME(ITIME)
< 1694> 1010 FORMAT (/' Particulates ',F8.2,2X,A3,'/',A3/
< 1695> & ' NOx (as N02) ',F8.2,2X,A3,'/',A3/
< 1696> & ' Primary N02 ',F8.2,2X,A3,'/',A3/
< 1697> & ' Soot ',F8.2,2X,A3,'/',A3/
< 1698> & ' Primary S04 ',F8.2,2X,A3,'/',A3)
< 1699> WRITE (ISMRY,*)' '
< 1700> C
< 1701> IF (LPDFLT.EQ.l) THEN
< 1702> WRITE (ISMRY,1003)
< 1703> 1003 FORMAT (/5X, '**** Default Particle Characteristics Assumed')
< 1704> ELSE
< 1705> WRITE (ISMRY,1004)
< 1706> 1004 FORMAT (/15X,'PARTICLE CHARACTERISTICS'/
< 1707> & 15X,'Density',7X,'Diameter'/
< 1708> & 15X, '====«=',7X, '««==«=')
< 1709> WRITE (ISMRY, 1005) DPART,IPART,DSOOT, ISOOT.DS04., IS04
< 1710> 1005 FORMAT (IX,'Primary Part. ',F6.1,7X,I6/
< 1711> & IX,'Soot ',F6.1,7X,I6/
< 1712> & IX.'Sulfate ',F6.1,7X,16)
< 1713> ENDIF
< 1714> C
< 1715> C TABLE C
< 1716> C
< 1717> WRITE (ISMRY,1006)
< 1718> 1006 FORMAT (/15X,'Transport Scenario Specifications:'/)
< 1719> WRITE (ISMRY,1007) 03,RV,DIST,XMIN,XMAX,GAMMA
< 1720> 1007 FORMAT (5X,'Background Ozone: ',F8.2,' ppm'/
< 1721> & 5X,'Background Visual Range: ',F8.2,' km'/
< 1722> & 5X,'Source-Observer Distance: ',F8.2,' km'/
< 1723> & 5X,'Min. Source-Class I Distance: ',F8.2,' km'/
< 1724> & 5X,'Max. Source-Class I Distance: ',F8.2,' km'/
< 1725> & 5X,'Plume-Source-Observer Angle: ',F8.2,' degrees')
< 1726> C
< 1727> WRITE (ISMRY,1008) ISTAB,U
< 1728> 1008 FORMAT (5X,'Stability: ',I3/
< 1729> & 5X,'Wind Speed: ',F6.2,' m/s')
< 1730>
< 1731> C
< 1732> IERR = 0
< 1733> 999 RETURN
-------
**
Page 35
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1735>
1736>
1737>
1738>
1739>
1740>
1741>
1742>
1743>
1744>
1745>
1746>
1747>
1748>
1749>
1750>
1751>
1752>
1753>
1754>
1755>
1756>
1757>
1758>
1759>
1760>
1761>
1762>
1763>
1764>
1765>
1766>
1767>
1768>
1769>
1770>
END
CDECK SMRPT2
C
SUBROUTINE SMRPT2 (IERR)
SAVE
1772>
1773>
1774>
1775>
1776>
1777>
1778>
1779>
1780>
1781>
1782>
1783>
1784>
1001
C
C
C
SUBROUTINE OUTPUTS RESULT SUMMARY TO
THE SUMMARY REPORT
COMMON /IO/ ITERM.ISMRY.ILOTUS
COMMON /COm/ ALPHA(39), BABS,BEXT(3),
& CPLUME(3,2,39), DELCR(3,2,39), DIST, GAMMA,
& 03, P(3,2,9), PHI(39), RP(39), RV, TAU, X(39),
& U,OMEGA,XMIN,XMAX,DFINE,DCOARS,DPART,DSOOT,DS04,
& SKYMAX(2),TERMAX(2),THRESH,CGREEN,
& QPARTI,QPART,QNOXI,QNOX,QN02I,QN02,QSOOTI,QSOOT,QS04I,
& QS04,RO(39),PRAY(2),PBACK(3,2),SCTANG(2),SKY(3,2),
& TERAIN(3,2,39),PLUSKY(3,2,39),PLUTER(3,2,39),DELSKY(2,39),
& DELTER(2,39),SPECB(3),SPECP(3),
& PSI(39),PERTHR(39),THRSKY(2,39),THRTER(2,39),RATIO,
& RATSKY(2),RATTER(2)
COMMON /COMI/ ISIZE,ISTAB,ITHETA,IFINE,ICOARS,IPART,ISOOT,
& IS04,ISKYMX(2),ITERMX(2),IANS,IEMISS,IDIST,IPAR,IMET,
& L1DFLT,LSCLAS(39),MXANG,MXLOS,IMASS,ITIME,
& LMDFLT,LPDFLT,LTDFLT
COMMON /COMC/ MASS,TIME,SOURCE,RECEPT,CLASSI,OBJSKY,OBJTER
CHARACTER*2 OBJSKY(2,39),OBJTER(2,39)
CHARACTER*3 MASS(5),TIME(5)
CHARACTER*7 CLASSI(2),IBACK(2)
CHARACTER*24 SOURCE,RECEPT
DATA IBACK / 'SKY '/TERRAIN'/
Ir*****
C
< 1771> C
1000
IERR = -1
WRITE (ISMRY,1000)
FORMAT (/28X,'R E S U L T S'//1X,'Asterisks (*) indicate',
& ' plume impacts that exceed screening criteria')
TABLE D RESULTS WITHIN CLASS I AREA
ICLASS = 1
ISMAX = ISKYMX(ICLASS)
WRITE (ISMRY.1001) CLASSI(ICLASS)
FORMAT (/10X,'Maximum Visual Impacts ',A,' Class I Area')
PASS OR FAIL ?
-------
** Page 36
< 1785> IF ((SKYMAX(ICLASS).GT.THRESH).AND.(RATSKY(ICLASS).GT.l.)) THEN
< 1786> WRITE (ISMRY,*) ' Screening Criteria ARE Exceeded'
< 1787> ELSE
< 1788> IF ((TERMAX(ICLASS).GT.THRESH).AND.(RATTER(ICLASS).GT.l.)) THEN
< 1789> WRITE (ISMRY,*) ' Screening Criteria ARE Exceeded'
< 1790> ELSE
< 1791> WRITE (ISMRY,*) ' Screening Criteria ARE NOT Exceeded'
< 1792> ENDIF
< 1793> ENDIF
< 1794> WRITE (ISMRY,1002)
< 1795> 1002 FORMAT (37X,'Delta E' ,7X,'Contrast'/35X,'«==« =',
< 1796> & 3X,'== ===='/lX,'Backgrnd',lX,'Theta',lX,
< 1797> & 'Azi',IX,'Distance',IX,'Alpha',IX,'Crit',2X,'Plume',3X,
< 1798> & 'Crit',2X,'Plume')
< 1799> WRITE (ISMRY,1005)
< 1800> 1005 FORMAT (IX,'========',IX,'-.»-»',IX,
< 1801> & '»-»', IX,' —', IX,'»»—', IX, '====',2X,'=—=',3X,
< 1802> & '====',2X,'=====')
< 1803> C
< 1804> C SKY
< 1805> C
< 1806> DO 100 IS = 1, 2
< 1807> WRITE (ISMRY,1003) IBACK(l),SCTANG(IS),PHI(ISMAX),X(ISMAX),
< 1808> & ALPHA(ISMAX),THRSKY(IS,ISMAX),DELSKY(IS,ISMAX),
< 1809> & OBJSKY(IS,ISMAX)(1:1),PERTHR(ISMAX),CPLUME(2,IS,ISMAX),
< 1810> & OBJSKY(IS,ISMAX)(2:2)
< 1811> 1003 FORMAT (2X,A7,1X,F4.0,1X,F4.0,2X,F5.1,3X,F4.0,1X,F5.2,1X,F6.3,
< 1812> & A1,1X,F5.2,1X,F6.3,A1)
< 1813> 100 CONTINUE
< 1814> C
< 1815> C TERRAIN
< 1816> C
< 1817> ITMAX = ITERMX(ICLASS)
< 1818> DO 101 IS = 1, 2
< 1819> WRITE (ISMRY,1003) IBACK(2),SCTANG(IS),PHI(ITMAX),X(ITMAX),
< 1820> & ALPHA(ITMAX),THRTER(IS,ITMAX),DELTER(IS,ITMAX),
< 1821> & OBJTER(IS,ITMAX)(1:1),PERTHR(ITMAX),DELCR{2,IS,ITMAX),
< 1822> & OBJTER(IS,ITMAX)(2:2)
< 1823> 101 CONTINUE
< 1824> C
< 1825> WRITE (ISMRY,*) ' '
< 1826> C
< 1827> C TABLE E RESULTS OUTSIDE CLASS I AREA
< 1828> C
< 1829> ICLASS = 2
< 1830> ISMAX = ISKYMX(ICLASS)
< 1831> WRITE (ISMRY,1001) CLASSI(ICLASS)
< 1832> C
< 1833> C PASS OR FAIL ?
< 1834> C
< 1835> IF ((SKYMAX(ICLASS).GT.THRESH).AND.(RATSKY(ICLASS).GT.l.)) THEN
-------
**
Page 37
< 1836>
< 1837>
< 1838>
< 1839>
< 1840>
< 1841>
< 1842>
< 1843>
< 1844>
< 1845>
< 1846> C
<• ift47-> r
^. 1 O*t / s \,
< 1848> C
< 1849>
< 1850>
< 1851>
< 1852>
< 1853>
< 1854> 200
< 1855> C
< 1856> C
< 1857> C
< 1858>
< 1859>
< 1860>
< 1861>
< 1862>
< 1863>
< 1864> 201
< 1865> C
< 1866> C
< 1867>
< 1868> 999
< 1869>
< 1870> CDECK
< 1871> C
< 1872>
< 1873>
< 1874> C
< 1875> C
< 1876> C
< 1877> C
WRITE (ISMRY,*) ' Screening Criteria ARE Exceeded'
ELSE
IF ((TERMAX(ICLASS).GT. THRESH). AND. (RATTER(ICLASS) .GT.l.)) THEN
WRITE (ISMRY,*) ' Screening Criteria ARE Exceeded'
ELSE
WRITE (ISMRY,*) ' Screening Criteria ARE NOT Exceeded'
END IF
ENDIF
WRITE (ISMRY, 1002)
WRITE (ISMRY, 1005)
CKY
DO 200 IS - 1, 2
WRITE (ISMRY, 1003) IBACK(l) ,SCTANG( IS) ,PHI(ISMAX) ,X(ISMAX) ,
& ALPHA(ISMAX),THRSKY(IS,ISMAX),DELSKY(IS,ISMAX),
& OBJSKY( IS, ISMAX) (1:1), PERTHR( ISMAX) ,CPLUME(2, IS, ISMAX) ,
& OBJSKY(IS,ISMAX)(2:2)
CONTINUE
TFRRflTN
— --- — --- Itrvrvnill •• — - — - — ~
ITMAX = ITERMX(ICLASS)
DO 201 IS = 1, 2
WRITE (ISMRY, 1003) IBACK(2),SCTANG( IS), PHI (ITMAX) ,X(ITMAX),
& ALPHA( ITMAX), THRTER( IS, ITMAX), DELTER( IS, ITMAX),
& OBJTER( IS, ITMAX) (1 : 1) , PERTHR( ITMAX) ,DELCR(2, IS, ITMAX) ,
& OBJTER(IS,ITMAX)(2:2)
CONTINUE
IERR = 0
RETURN
END
WINPTS
SUBROUTINE WINPTS (IERR)
SAVE
SUBROUTINE WRITES INPUTS TO HEADER OF
THE FULL RESULTS FILE
< 1878> £********************************************************************
< 1879> C
< 1880>
< 1881>
< 1882>
< 1883>
< 1884>
< 1885>
< 1886>
COMMON /I O/ ITERM, ISMRY, ILOTUS
COMMON /COm/ ALPHA(39), BABS,BEXT(3) ,
& CPLUME(3,2,39), DELCR(3,2,39), DIST, GAMMA,
& 03, P(3,2,9), PHI(39), RP(39), RV, TAU, X(39),
& U, OMEGA, XMIN,XMAX,DFINE,DCOARS,DPART,DSOOT,DS04,
& SKYMAX(2) ,TERMAX(2) .THRESH, CGREEN,
& QPARTI,QPART,QNOXI,QNOX,QN02I,QN02,QSOOTI,QSOOT,QS04I,
-------
** Page 38
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1909>
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1927>
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1929>
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1931>
1932>
1933>
1934>
1935>
1936>
1937>
1000
C
C
C
1001
C
C
C
C
C
C
& QS04,RO(39),PRAY(2),PBACK(3,2),SCTANG(2),SKY(3,2),
& TERAIN(3,2,39),PLUSKY(3,2,39),PLUTER(3,2,39),DELSKY(2,39),
& DELTER(2,39),SPECB(3),SPECP(3),
& PSI(39),PERTHR(39),THRSKY(2,39),THRTER(2,39),RATIO,
& RATSKY(2),RATTER(2)
COMMON /COMI/ ISIZE,ISTAB,ITHETA,IFINE,ICOARS,IPART,ISOOT,
& IS04,ISKYMX(2),ITERMX(2),IANS,IEMISS,IDIST,IPAR,IMET,
& L1DFLT,LSCLAS(39),MXANG,MXLOS,IMASS,ITIME,
& LMDFLT,LPDFLT,LTDFLT
COMMON /COMC/ MASS,TIME,SOURCE,RECEPT,CLASSI,OBJSKY,OBJTER
CHARACTER*2 OBJSKY(2,39),OBJTER(2,39)
CHARACTER*3 MASS(5),TIME(5)
CHARACTER*7 CLASSI(2)
CHARACTER*24 SOURCE,RECEPT
CHARACTER*! IQUOT
DATA IQUOT / " " /
IERR = -1
WRITE (ILOTUS,1000) IQUOT,SOURCE,IQUOT,IQUOT,RECEPT,IQUOT,
& IMASS,ITIME
FORMAT (A,A,A/A,A,A/215)
EMISSIONS
WRITE (ILOTUS,1001) QPARTI,QNOXI,QN02I,QSOOTI,QS04I
FORMAT (8F10.3)
GEOMETRY 1
WRITE (ILOTUS,1001) DIST,XMIN,XMAX,RV
PARTICLE CHARACTERISTICS
WRITE (ILOTUS,1002) L1DFLT,DFINE,IFINE,
&
&
&
&
1002
C
C
C
1003
C
C
C
L1DFLT,DCOARS,ICOARS,
L1DFLT,DPART,IPART,
L1DFLT,DSOOT,ISOOT,
L1DFLT,DS04,IS04
FORMAT (I5,F10.3,I5)
BACKGROUND OZONE AND MET
WRITE (ILOTUS,1003) L1DFLT,03,U,ISTAB
FORMAT (I5,2F10.3,I5)
PLUME OFFSET ANGLE
-------
** Page 39
< 1938>
< 1939> C
< 1940> C
< 1941>
< 1942> 999
< 1943>
1
1
i
< 1944> CDECK I
< 1945> C
< 1946>
< 1947>
< 1948> C
< 1949> C
< 1950> C
< 1951> C
< 1952> C***
< 1953> C
< 1954>
< 1955>
< 1956>
< 1957>
< 1958>
< 1959>
< 1960>
< 1961>
< 1962>
< 1963>
< 1964>
< 1965>
< 1966>
< 1967>
< 1968>
< 1969>
< 1970>
< 1971>
< 1972>
< 1973>
< 1974>
< 1975> C
< 1976>
< 1977> C
< 1978> C***
< 1979> C
< 1980>
< 1981>
< 1982>
< 1983>
< 1984>
< 1985>
< 1986>
< 1987>
< 1988>
**•
I
I
&
&
&
&
&
&
&
&
&
&
1
&
&
&
1
1
1
1
1
**i
1
1
&
&
&
WRITE (ILOTUS,1003) L1DFLT,GAMMA
IERR = 0
RETURN
END
WRESLT
SUBROUTINE WRESLT (NLOS,IERR)
SAVE
SUBROUTINE WRITES RESULTS TO
THE FULL RESULTS FILE
COMMON /IO/ ITERM,ISMRY,ILOTUS
COMMON /COMR/ ALPHA(39), BABS,BEXT(3),
CPLUME(3,2,39), DELCR(3,2,39), DIST, GAMMA,
03, P(3,2,9), PHI(39), RP(39), RV, TAU, X(39),
U,OMEGA,XMIN,XMAX,DFINE,DCOARS,DPART,DSOOT,DS04,
SKYMAX(2),TERMAX(2),THRESH,CGREEN,
QPARTI,QPART,QNOXI,QNOX,QN02I,QN02,QSOOTI,QSOOT,QS04I,
QS04,RO(39),PRAY(2),PBACK(3,2),SCTANG(2),SKY(3,2),
TERAIN(3,2,39),PLUSKY(3,2,39),PLUTER(3,2,39),DELSKY(2,39),
DELTER(2,39),SPECB(3),SPECP(3),
PSI(39),PERTHR(39),THRSKY(2,39),THRTER(2,39),RATIO,
RATSKY(2),RATTER(2)
COMMON /COm/ ISIZE,ISTAB,ITHETA,IFINE,ICOARS,IPART,ISOOT,
IS04,ISKYMX(2),ITERMX(2),IANS,IEMISS,IDIST,IPAR,IMET,
L1DFLT,LSCLAS(39),MXANG,MXLOS,IMASS,ITIME,
LMDFLT,LPDFLT,LTDFLT
COMMON /COMC/ MASS,TIME,SOURCE,RECEPT,CLASSI,OBJSKY,OBJTER
CHARACTER*2 OBJSKY(2,39),OBJTER(2,39)
CHARACTER*3 MASS(5),TIME(5)
CHARACTER*? CLASSI(2)
CHARACTER*24 SOURCE,RECEPT
INTEGER 1C
Q********************************************************^
IERR = -1
WRITE (ILOTUS.1000) NLOS
DO 100 LOS = 1, NLOS
1C = LSCLAS(LOS)
IF (IC.EQ.2) 1C = 0
WRITE (ILOTUS,1000) LOS,IC,PHI(LOS),ALPHA(LOS),X(LOS),
RP(LOS),RO(LOS),PSI(LOS),PERTHR(LOS),
(THRSKY(I,LOS),DELSKY(I,LOS),1=1,MXANG),
(THRTER(I,LOS),DELTER(I,LOS),1=1,MXANG)
-------
**
Page
40
1989>
1990>
1991>
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1993>
1994>
1995>
1996>
1997>
1998>
1999>
2000>
2001>
2002>
2003>
2004>
2005>
2006>
2007>
2008>
2009>
1000
100
C
C
C
1001
200
C
C
999
FORMAT
CONTINUE
URl
- - - — Hi\l
WRITE (IL
DO 200 LC
1C = L5
IF (1C.
WRITE (
&
&
&
FORMAT
CONTINUE
IERR = 0
RETURN
END
(1X,I2,I2,F8.1,4F7.1,F5.2,F7.
JE OUT CONTRAST ORDERED GREEN
.OTUS,1000) NLOS
»S - 1, NLOS
;CLAS(LOS)
EQ.2) 1C = 0
ILOTUS,1001) LOS,IC,PHI(LOS),
(CPLUME(2,J,
(CPLUME(1,J,
(CPLUME(3,J,
(1X,I2,I2,F8.3,15F7.3)
LOS)
LOS)
LOS)
3.10F7.2)
, BLUE, RED
PERTHR(LOS)
,DELCR(2,J,
,DELCR(1,J,
,DELCR(3,J,
,
LOS)
LOS)
LOS)
,J=1,MXANG),
,J=1,MXANG),
,J=1,MXANG)
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
i. REPORT NO.
EPA-450/4-88-015
2.
4. TITLE AND SUBTITLE
Workbook for Plume Visual Impact Screening and Analysis
3. RECIPIENT'S ACCESSION NO.
5. REPORT DATE
September 1988
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Douglas A. Latimer and Robert G. Ireson
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
10. PROGRAM ELEMENT NO.
Systems Applications, Inc.
101 Lucas Valley Road
San Rafael, CA 94903
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
Office of Air Quality Planning and Standards
Technical Support Division
U.S. Environmental Protection Agency
Research Triangle Park. NC 27711
13. TYPE OF REPORT AND PERIOD COVERED
14. SPONSORING AGENCY CODE
15 SUPPLEMENTARY NOTES
This document is a revision of the Workbook for Estimating Visibility Impairment,
EPA-450/4-80-031.
1R ABSTRACT
The Prevention of Significant Deterioration and visibility regulations of the U.S.
Environmental Protection Agency (EPA) require the evaluation of a type of visibility
impairment which can be traced to a single source or small group of sources known as
"plume blight". This Workbook presents current EPA guidance on the use of screening
procedures to estimate visibility impairment due to plume blight and is an update and
a revision to the earlier book. It is being issued as a draft for public comment until
a final version is incorporated into the Guideline on Air Quality Models (Revised).
It preserves the same 3-level screening approach and includes a new screening model
(VISCREEN) that can be run on a personal computer. The VISCREEN model is used for
both Level-1 and Level-2 screening analyses, and is designed to evaluate plume visual
effects along multiple lines of sight across the plume's length for two different
viewing backgrounds and for two different scattering angles. It also provides for
the evaluation of the potential perceptibility of plumes using recent psychophysical
concepts. The Workbook provides the technical basis for the model and contains
several example applications to illustrate the use of these methods.
1 7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
Air Pollution
Meteorology
Air Quality Dispersion Model
Visibility
Aerosols
Nitrogen Dioxide
b.lDENTIFIERS/OPEN ENDED TERMS
New Source Review
Air Pollution Control
c, COSATI Held/Group
13B
4A
4B
in HIS T niBUTION STATEMENT
Release Unlimited
19. SECURITY CLASS (Till! Report)
Unclassified
21 NO. OF PAGES
200
20 SECURITY CLASS iTIuspage)
Unclassified
27 PRICE
FPA Form 2270-1 (Rev. 4-77)
Pnrvious Em DON is OBSOLETE
------- |