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assume efficiencies at 0.5
maresimilar to those at
7.11. What color would you see during the day due to
the following constituents if they were in the air in high
concentrations: (a) soot particles, (b) nitrogen dioxide
gas, (c) haze particles containing mostly water, and (d)
ozone gas? Explain the process causing the color (e.g.,
absorption of blue light, scattering of green and red
light).
0.55
m.
7.7. If a person's liminal contrast ratio is 0.01 instead
of 0.02, what would be the expression for their
meteorological range? For a given total extinction coef-
ficient, how much further (in percent) can the person
see when their liminal contrast ratio is 0.01 instead of
0.02?
7.6. Visibility Project
Find an elevated location outside where, on a clear day,
it is possible to see a long distance over at least 75
percent (270 degrees) along the horizon circle without
obstruction by buildings or mountains. Predetermine
the distances to a set of landmarks that cover at least 50
percent (180 degrees) of the horizon circle, but not nec-
essarily in continuous sectors around the circle. At two
times during a single day (a morning and an afternoon),
(a) estimate the prevailing visibility and (b) make a list
of the colors you see in the sky along the horizon and
where you see them. Discuss your findings in terms of
differences between times of day. Comment on how the
relative humidity, wind, and large-scale pressure system
may have affected results if that information is avail-
able. Which of these factors do you believe had the
greatest effect on visibility?
7.8. Assume that the atmosphere contains 10,000
g
m
−
3
of liquid water and the density of liquid water is
1.0gcm
−
3
.For which size spherical particles is visi-
bility reduced the most at a wavelength of 0.55
m:
(a)
0.5-
m-diameter
particles,
(b)
10-
m-diameter
particles, or (c) 100-
m-diameter particles? Assume
single-particle scattering efficiencies in Figure 7.21
can
be
used
for
wavelengths
of
0.55
m.
Show
calculations.
7.9. Explain why soil often appears brown. What is the
difference between soil that appears brown and soil that
appears red?
7.10. If the visual range around 37 percent of the hori-
zon circle is 8 km, that around 15 percent of the circle
is 3 km, and that around the remaining 48 percent of
the circle is 12 km, what is the prevailing visibility?
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