1. Deciviews from Look Rock, Great Smoky Mountains National Park
SSACgnp.TD883.LV1.7
Deciviews from Look Rock, Great Smoky Mountains National Park
How Hazy Is It?
06/30/ :45 PM EDT Visual range is approximately 83 mi.
Core Quantitative Literacy Topics
Algorithm
Supporting Quantitative Literacy Topics
Scientific notation
Logarithm; logarithmic scale
Unit conversions
Comparing numbers
Core Geoscience Subject
Air quality
Len Vacher, Department of Geology, University of South Florida, Tampa
Jim Renfro, Great Smoky Mountains National Park
Susan Sachs, Appalachian Highlands Science Learning Center, Great Smoky Mountains National Park
© 2010 University of South Florida Libraries. All rights reserved. 1

2. Getting started North Carolina
After completing this module you should be able to:
Know in a general way how far you can see from a Smoky Mountain lookout.
Know what deciviews are.
Know that haziness results from scattering and absorption of light.
Know what particles in the air are responsible for the scattering and absorption of light.
Describe what an algorithm is.
Describe how the Haze Index is like the Richter Magnitude.
North Carolina
And you should also know where Great Smoky Mountains National Park is. 2

3. The setting – Great Smoky Mountains National Park
Great Smoky Mountains National Park protects 524,000 acres of temperate mountains ranging in elevation from 875 to 6,640 feet in the Southern Appalachians. This range in altitude mimics the latitudinal changes you would experience driving north or south across the eastern United States, say from Georgia to Maine. Plants and animals common in the southern United States thrive in the lowlands of the Smokies while species common in the northern states find suitable habitat at the higher elevations. This makes the Smokies one of the most biologically diverse areas in the nation. In recognition of the park's unique natural resources, the United Nations has designated Great Smoky Mountains National Park as an International Biosphere Reserve. The Smokies is also the most visited National Park in the entire country, with over 9 million visitors each year.
A huge inventory of all species has added almost 900 new species to science and over 6,300 new park records. Pictured is a Tardigrade, with 18 new species discovered.
Elk were reintroduced in the Smokies in 2001
The Smokies has over 2,000 miles of streams and 900 miles of trails.
The endemic Red-cheeked salamander (above). The park is referred to as the Salamander Capital. 3

4. The problem A clear day A hazy day
Some days are hazier than others. How can you quantify how hazy the day is? How much worse is one day than another?
The Great Smoky Mountains National Park Look Rock air quality station houses a digital camera which takes high resolution pictures of the view every fifteen minutes. The “good day” image is from 3 pm EDT September The “hazy day” image is from 3 pm EDT August How much hazier was it on that hazy day?
The air quality station is at the Look Rock observation tower, a popular destination ½ mile off the Foothills Parkway. Come enjoy the 360-degree panoramic view. 4

5. Quantifying visibility
Comment. “Visibility is more than being able to see a black object at a distance for which the contrast reaches a threshold value. Coming upon a mountain …, an observer does not ask, ‘How far do I have to back away before the vista disappears?’ Rather, the observer will comment on the color of the mountain, on whether geological features can be seen and appreciated, or on the amount of snow cover resulting from a recent storm system.” (W.C. Malm, Introduction to Visibility)
Map of field of view
Definition. Visual range (VR). The greatest distance that a large dark object can just be seen by a human observer, under uniform lighting conditions, against the background sky. (EPA 2001, Visibility in Mandatory Federal Class I Areas, )
How does one quantify visibility in terms of the underlying factors that affect it so that one can track improvement or impairment?
We start with the fundamentals: scattering and absorption of light.

6. Scattering and absorption
The phenomenon behind the diminished view is the scattering and absorption of photons (wave-like particles of light). You see an object in your line of sight (such as the scenic geologic feature in the diagram) because of photons from a light source (the sun here) that reflect off the object and then follow your line of sight to your eye.
But you see not only those photons. You also see ones that scatter into your line of sight because of their encounter with small particles in the air.
And you don’t see the ones that are scattered out of the line of sight or are absorbed by particles in the air.
Malm, 1999, Fig. 1.5

7. Measuring scattering and absorption
These diagrams show the fate of photons as they pass through the chamber of two measuring instruments. The measurement of interest is the intensity of light that reaches the detection plate relative to the intensity of light that enters it. The fractional loss of intensity per unit distance is known as the light extinction coefficient.
Malm, 1999, Fig. 5.2
In the transmissometer (upper diagram), the detection plate is perpendicular to the path of the incoming photons. It measures light extinction from both scattering and absorption.
In the nephelometer (lower diagram), the detection plate is parallel to the path of the incoming photons. It measures light extinction from scattering only.
The little squiggles represent photons, which behave both like waves and particles. Photons of blue light have shorter wavelengths than photons of red light.
Malm, 1999, Fig. 5.3

8. Measurements at Look Rock, 1
The Web cam images on Slide 4 are from the visibility monitoring station at Look Rock. The Look Rock station is part of the Interagency Monitoring of Protected Visual Environments (IMPROVE) program, which was established in Monitoring for the program was initiated in 1988 at 20 sites, one of which was Look Rock, which actually began monitoring in The monitoring program was expanded to 110 sites in 2001.
One of the instruments at the Look Rock site is a nephelometer, which measures the light extinction due to scattering every 15 minutes. The visual ranges shown with the two images on Slide 4 were calculated from these measurements. On the good day shown on that slide, the visual range was 132 miles. On the hazy day it was only 7 miles. These values apply to the time of the images. We will use an IMPROVE method to calculate a 24-hr average for those dates from the particles in the air.

9. Measurements at Look Rock, 2
Not only can light extinction be measured optically with a transmissometer or nephelometer, it can be calculated from the concentrations of the various kinds of particles that scatter and absorb the light. It is probably evident why this approach would work: Increase the number of atmospheric particles, and you increase the amount of light scattering and absorption.
All IMPROVE sites are equipped to determine the light extinction from the amount of particles in the air.
Useful words
Aerosol – Suspensions of tiny liquid and/or solids in the air.
Particulate matter – Material that is carried by liquid or solid aerosol particles with aerodynamic diameters less than 10 microns (i.e., less than 1/100th of a mm).
PM2.5 – Particles that are smaller than 2.5 microns (1/400th of a mm)
Rayleigh scattering – the natural scattering due to the molecules of the gases that make up air.
The strategy: Measure the concentrations of the constituents in the particulate matter of the aerosols. Calculate the light extinction due to each constituent. Then add them up.

10. A look at some data
Here are the concentrations of the major constituents of the particulate matter on the good visibility day at Look Rock shown on Slide 4. The concentrations are in micrograms per cubic meter.
The first five constituents compose the PM2.5 fraction. The sulfate and nitrate of the ammonium sulfate and ammonium nitrate are generally formed in the atmosphere from sulfur dioxide (sulfate) and nitrogen oxide emissions (nitrate). The main source of nitrogen oxides is the combustion of fossil fuels in general, and the main source of sulfur dioxide is the combustion of coal in particular. The ammonium component is from ammonia, derived mainly from animal wastes and cleansers. Organic carbon aerosols are largely from vegetation and its combustion. Elemental carbon is soot from various sources. Soil is from wind erosion, agricultural practices, heavy construction and unpaved roads. The coarse mass is from the same sources but consists of larger particles (between 2.5 and 10 microns). The “soil” and “coarse mass” are collectively referred to as crustal material.
Click on the Excel worksheet above and save immediately to your computer. Complete the spreadsheets at each of the tabs starting with “Slides ” Yellow cells contain given values, and orange cells contain formulas. The spreadsheet at the “EOM Answers” tab is for your answers to the end-of-module questions.
These data and the rest of the numbers in the complete spreadsheet developed in the next slides are based on information from VIEWS (Visibility Information Exchange Web System).

11. Method of calculation: the IMPROVE algorithm
The core quantitative-literacy subject of this module is the concept of algorithm. An algorithm is a step-by-step procedure that one uses to calculate one or more outputs from one or more inputs. For example, the following is an algorithm.
To convert from Fahrenheit to Centigrade, start with the temperature in degrees Fahrenheit. Subtract 32 degrees and you get the number of degrees Fahrenheit that the original temperature exceeds the freezing point of water. Take that number and multiply by 5 and divide by 9. The result will be the temperature in degrees Centigrade.
Can you state this procedure in the form of an equation? Often algorithms can be stated as an equation expressing a function.
More often, algorithms can be stated as a succession of equations. One works through them one step at a time. The main thing is to stay organized and keep your calm. A spreadsheet can help.
The IMPROVE equation is such an algorithm. You start with the measured concentrations from the air-quality monitoring site and work your way, step-by-step, through a succession of equations to calculate the extinction coefficient and other dependent variables quantifying visibility and haze. You can use a spreadsheet to organize your work and crunch the numbers. 11

12. Getting started with the IMPROVE algorithm
We will be using the RHR1 algorithm, so it is entered in Row 2 of your spreadsheet.
Some particles scatter light more effectively than others, so there is an efficiency multiplier. Organic carbon particles, for example, scatter light more than sulfate particles.
Column C in your spreadsheet lists the efficiencies for the six constituents.
Ammonium sulfate and ammonium nitrate particles are hygroscopic, meaning that they attract and absorb water molecules. This increases the size of the particles and light scattering. How much depends on the relative humidity. So, for these constituents, there is an additional multiplier, fRH (function of relative humidity). The Views Web site includes the fRH values along with the constituent concentrations for each measurement day.
Column D in your spreadsheet lists the fRH for the two hydroscopic particles.

13. The calculation: calculating extinction
Part 1 of our calculation by the IMPROVE algorithm determines the light extinction coefficient.
The units of the light extinction coefficient are inverse megameters (Mm)-1, which means 1/(106 m). These are the units you get if you multiply concentration in micrograms per cubic meter times efficiency in meters- squared per gram.
The total extinction coefficient (Cell B23), is the sum of several partial extinction coefficients. For the first (ammonium sulfate), find the product of its concentration, efficiency and fRH. Do the same for the ammonium nitrate. For organic carbon, elemental carbon, soil, and coarse mass, use the product of only their concentration and efficiency. Use formulas in the orange cells. Numbers that are in the yellows cells are given values. Format results to tenths.
Cell B21 is a subtotal, the extinction due to the six aerosol constituents. We added to this the extinction due to the gas molecules of the air (Rayleigh extinction in Cell B22) to obtain the total extinction coefficient in Cell B23. 13

14. IMPROVE algorithm: from extinction coefficient to visual range and Haze Index
Part 2 completes the algorithm by adding results calculated from the total extinction coefficient.
The standard visual range (SVR, in km) is calculated by dividing a constant, 3912, by the total light extinction coefficient. The constant is 10× what the SVR would be for Rayleigh scattering alone (no particulate matter). Calculate the SVR in km in Cell B26 and convert the result to miles in Cell B27.
The Haze Index (HI) is a scale designed to quantify the haze from the particulates. The units of the Haze Index are deciviews (dv). It is calculated as 10 times the natural logarithm (a built-in function in Excel) of the total extinction coefficient divided by 10. That’s
=10*LN(B23/10)
In the language of Excel for this spreadsheet. Calculate the HI in dv in Cell B28. 14

15. Another day, another deciview from Look Rock
Now you will see the power of setting up an algorithm on a spreadsheet.
On Aug 4, 2007 (the hazy day of Slide 4), the constituent concentrations were as follows (all in micrograms per cubic meter):
ammonium sulfate 22.17
ammonium nitrate, 0.119
organic carbon, 3.59
elemental carbon, 0.524
soil, 0.776
coarse mass, 3.24
The relative humidity was a little lower, so the fRH value was 3.00.
What are the values for the visual range and Haze Index for new date?
All you have to do is enter the six new concentrations into Cells B6 through B11, and the new fRH value into Cells D6 and D7, and the spreadsheet will do the rest! (Don’t forget to enter the new date.) 15

16. Comparing results 9/18/04 HI = 15 deciviews SVR = 92 km 8/4/07
The haze index was 106% higher and the standard visual range 82% lower on 8/4/07 than on 9/18/04.
The light extinction coefficient was 445% higher on 8/4/07 (233 (Mm)-1) than on 9/18/04 (43 (Mm) -1). Fully 93% of the 190 (Mm) -1difference was from the 179 (Mm) -1 increase due to the additional ammonium sulfate in the air. 16

17. Epilog
The “RHR” of “RHR Algorithm” stands for the Regional Haze Rule, which was implemented by the Environmental Protection Agency in 1999 (see Appendix). The RHR calls for states to develop plans to assure that visibility improves on the worst days and there is no loss of visibility on the best days at Federal Class I areas. For the purpose of the RHR, the worst days are represented by the average of the deciview level (Haze Index) on the worst 20% of the days, and the best days are represented by the average of the deciview level on the best 20% of the days. Sept (our “good day” example) is one of the best 20%, and Aug (our “hazy day”) is one of the worst 20%.
There has been marked improvement in visual range since 1999, as sulfate has been reduced by the reductions of sulfur dioxide emissions. Note the inverse relation between ammonium sulfate and visual range on the 20% worst days.
There is reason for optimism that the views in the Smokies that were shrinking for decades in the second half of the 20th century will continue to expand as air quality regulations in the region take effect. 17

18. A mathematical view of deciviews
The Haze Index (deciviews) is a logarithmic scale of extinction. This is so because you calculate HI by taking the natural logarithm of the light extinction coefficient. This spreadsheet shows the cardinal feature of a logarithmic scale: Each time you increase the scale by an increment of 1 dv (e.g., from HI=15 to 16 deciviews), you multiply the measured quantity (extinction) by a factor. For HI, the factor is … (see Column C). Another way to say that is that each step of the HI scale corresponds to a % increase of the light extinction coefficient. Thus if HI increases from 15 to 18 deciviews (three steps), the new light extinction coefficient is ( )^3, or 1.35× as large (i.e., 35% larger).
Use the tab labeled “Haze Index” in the template from Slide 10 for this exercise.
The formula in Cell B2 is =10*EXP(A2/10).
The EXP (exponential) function reverses the LN (natural logarithm) function.
The scale for earthquake magnitude works the same way because it is also a logarithmic scale. The variable analogous to the light extinction coefficient is the energy released by an earthquake. The multiplier is (rather than for the HI). For example, the magnitude of the Loma Prieta earthquake (1989) was 6.9, and the magnitude of the San Francisco earthquake (1906) was 7.8; therefore, the energy released by the San Francisco earthquake was 31.6^0.9 or ~22× the energy released by the Loma Prieta earthquake. 18

19. End-of-module assignment
The correlation between sulfate pollution and poor visibility at Great Smoky Mountains N.P. is unmistakable as shown in this module. Not only does high sulfate in the air impair visibility; it leads to acid rain and is also a public health issue. It contributes to PM2.5, which is one of EPA’s six criteria pollutants for air quality. The EPA’ s National Ambient Air Quality Standard for a 24-hr average PM2.5 is 35.5 micrograms per cubic meter. For the hazy day (8/4/07), the 24-hr average PM2.5 was 49.3 micrograms per cubic meter at Look Rock, and the park put out a health advisory. Suppose the PM2.5 of that day were 14.3 micrograms per cubic meter less and the difference was due solely to a reduction in ammonium sulfate. Use your spreadsheet for 8/4/07 to calculate what the Haze Index (deciviews) would have been on that date (i.e., keep everything else the same; change only the value for ammonium sulfate).
2. States are required to set progress goals for improving visibility from baseline conditions (represented by ) to 2018 (represented by ) for their Class I areas. The goal is that the rate of improvement, when sustained, would achieve natural conditions in 60 years (2064). Natural conditions for the Smokies are estimated to be 11 deciviews. Use your spreadsheet for 9/18/04 to determine what ammonium sulfate concentration would be necessary (keeping everything else the same) to achieve 11 deciviews on that day.
3. The Smoky Mountains are named for their misty clouds. Describe how regional haze is something different.
4. What Haze Index and Standard Visual Range correspond to Rayleigh scattering? That is, suppose there are no particulates in the air. Use either of your spreadsheets to find out.

20. Appendix: from the Clean Air Act to the Regional Haze Rule
Creation of the Environmental Protection Agency (EPA). Passage of the Clean Air Act, the main purpose of which is to establish Federal standards for various pollutants from stationary and mobile sources and to provide for the regulation of polluting emissions via state implementation plans. Clean Air Act Timeline.
1977. Clean Air Act Amendments. Defines a national visibility goal: “the prevention of any future, and the remedying of any existing, impairment of visibility in mandatory Federal Class I areas which impairment results from manmade air pollution.”
1990. Clean Air Act Amendments, Charges the EPA in conjunction with the NPS and other federal land managers to expand visibility-related monitoring at Federal Class I sites and to provide Congress with regular assessments.
The 156 Federal Class I areas include national parks more than 6,000 acres in area. How many of these are there?
1999. EPA promulgates the Regional Haze Rule.
Return to Slide 17 20