**A Technical Evaluation of Smoke Dispersion from the Hogback and
Shortoff Prescribed Fires and Possible Impacts on Air Quality in Bryson
City, NC**

Prepared by Air Specialists, Cindy Huber and Bill Jackson

Finalized August 8, 2007

Revised August 29, 2007

On March 22, 2007 the fine particulate monitor in Bryson City, NC
registered concentrations above normal from about 1700 until 0900 the
following day, March 23, 2007. The concentrations were high enough to
cause the 24-hour average for March 22, 2007 to exceed the new 24-hour
fine particulate National Ambient Air Quality threshold of 35 micrograms
per cubic meter.

Satellite imagery (Figure 1) reveals two fires burning on March 22, one
in southwestern NC and another in southeastern Tennessee. These are
prescribed fires that were being conducted by the US Forest Service
(Figure 2). The focus of this evaluation is to determine the likelihood
that smoke from one or both of these prescribed fires affected the air
quality in Bryson City and contributed to higher than normal nighttime
fine particulate measurements.

![](media/image1.wmf){width="4.80625in" height="3.502083333333333in"}

> Figure 1. MODIS image from March 22, 2007 showing fires (red outline)
> in southwestern NC and southeastern TN.

![](media/image2.jpeg){width="5.246527777777778in"
height="4.054166666666666in"}

> Figure 2. Locations of prescribed burns and fine particulate monitors
> used for this evaluation.

**Air Quality at Bryson City, NC**

Smoke from wildland fire contains particulate matter, primarily fine
particulate less than 2.5 microns in diameter (PM~2.5~). High
concentrations of PM~2.5~ can have a negative impact on people\'s health
and reduce visibility along roadways and scenic views. To help people
understand the relationship between pollutant concentration and human
health, the Environmental Protection Agency has developed a system that
color codes air quality data based on human health effects (Appendix A)
and it is called the Air Quality Index (AQI). The index is color-coded
from green (no effect) to maroon (hazardous for all people). When the
AQI value for any pollutant is color-code green or yellow it carries no
cautionary health statement. But at the next level, AQI equals orange,
people who are sensitive to air pollutants or have other health
problems, may experience health effects. This means they are likely to
be affected at lower levels than the general public. Sensitive groups of
people include the elderly, children, and people with either lung
disease or heart disease. The general public is not likely to be
adversely affected when the AQI equals orange. Everyone may begin to
experience health effects when AQI equals red, and those sensitive to
air pollutants may experience more serious health effects. Purple and
maroon, the next two levels in the AQI, represent increasingly hazardous
conditions for human health.

Elevated fine particulate concentrations were measured at the continuous
PM~2.5~ monitor (AIRS Site ID: 371730002) in Bryson City on March 22-23,
2007. The continuous monitoring conducted by North Carolina Division of
Air Quality meets Federal Reference methods criteria established by the
Environmental Protection Agency. The highest hourly average
concentrations were measured between 1700 March 22 and 0900 March 23,
and reached a maximum of 170 micrograms per cubic meter at 1700 March 22
(Figure 3). This value is equivalent to a 1-hour AQI value of code red
which has an associated "unhealthy" level of health concern. The average
PM~2.5~ concentrations returned to normal levels for the monitoring site
at about 1000, March 23.

![](media/image3.wmf){width="5.2375in" height="3.5881944444444445in"}

> Figure 3. Fine particulate measurements from the Bryson City, NC
> Federal Reference Monitor for March 21-24, 2007.

Figure 4 shows how the inclusion of higher hourly concentrations on
March 22 contributed to increases in the daily average PM~2.5~
concentrations. Daily averages are important because there is a National
Ambient Air Quality Standard (NAAQS) for PM~2.5~ which states must
attain. The red line in Figure 3 shows the new 24-hour standard for
PM~2.5~, which is 35 micrograms per cubic meter. (The standard was
lowered from 65 to 35 micrograms per cubic meter in September 2006,
based on current health effects research.)

![](media/image4.wmf){width="4.690972222222222in"
height="3.2131944444444445in"}

> Figure 4. Comparison of daily average concentrations to the 24-hour
> National Ambient Air Quality Standard for fine particulate (PM~2.5~).

**What happened to the smoke dispersed from the Hogback and Shortoff
prescribed fires on March 22, 2007?**

**Fire Activity:** On March 22, 2007 prescribed burning was taking place
at two sites, the Hogback prescribed fire on the Ocoee District of the
Cherokee National Forest in TN and the Shortoff prescribed fire on the
Tusquitee District of the Nanatahala National Forest in NC. The areas
are approximately 35 miles apart (Figure 2).

[Hogback Prescribed Fire:]{.underline} The Cherokee National Forest (TN)
implemented the Hogback prescribed fire using a combination of hand
ignition and aerial ignition from a helicopter. The burn unit covers
1875 acres and elevation varies from 1000-2100 feet. Ignition began
around noon on March 22 and was completed by 1700 the same day. It is
estimated that fuels were consumed on about 1700 acres of the burn unit.
The active fire phase continued into the night until about midnight. The
Fire Emissions Production Simulator (FEPS) was used to estimate hourly
fine particulate emissions (Figure 5) and heat release rate from the
burn unit. Maximum emissions from the prescribed fire probably occurred
between 1400 and 1700 the afternoon of March 22.

![](media/image5.wmf){width="4.417361111111111in" height="3.04375in"}

> Figure 5. Hourly fine particulate emissions estimates from the Hogback
> prescribed fire using FEPS.

The Morristown, TN National Weather Service (NWS) office provides daily
fire weather forecasts for both areas (east Tennessee and southwestern
NC) where prescribed burning was planned. The NWS also provides spot
weather forecasts for specific burn units at the request of the Forest.
The following chart summarizes the weather parameters reported in both
the fire weather and spot weather forecasts for the Hogback prescribed
fire.

  ----------------------- ----------------------- -----------------------
  March 22, 2007          Fire Weather Forecast   Spot Weather Forecast
                          (0515)                  (0721)

  Mixing Height (above    6100                    5500
  mean sea level)                                 

  Transport Winds (miles  From SW at 17 mph       from SW at 20 mph
  per hour)                                       

  Dispersion              93                      97

  Sky/Weather             Partly Cloudy\*         Partly Cloudy\*

  Surface Temperature     72-77                   Max 76
  (^o^F)                                          

  Relative Humidity (%)   35-40                   Min 38

  Windspeed at 20 ft      From SW at 7 mph        From SW at 7-12 mph,
  above ground (miles per                         with occasional higher
  hour)                                           winds
  ----------------------- ----------------------- -----------------------

\*According to the Georgia Forestry Commission website a Partly Cloudy
day is interpreted to have 30% to 50% cloud cover
(<http://weather.gfc.state.ga.us/Info/WXexp.aspx>).

The NWS forecasts predicted transport winds from the SW at speeds of
17-20 mph on March 22, which would have moved smoke from the Hogback
prescribed fire toward Knoxville, TN which is located NE of the burn
unit.

Weather observations and measurements are taken on-site the day of the
burn, for all prescribed fires conducted by the US Forest Service.
Observed surface winds were of variable low speeds and from the SW
throughout the day. Weather measurements are also taken automatically at
remote stations located across the National Forest System.

This network of weather stations is called RAWS (Remote Automated
Weather Stations) and the closest site to the burn unit is Coker Creek
(CCKT1, elevation 1700 feet). Data from this site shows that surface
winds on March 22 were from the S and SW. Surface wind speeds were 6-7
mph during the afternoon hours. Winds became more variable on March 23
shifting from S to SSW throughout the day. Based on the combination of
predicted and observed weather information, it is unlikely that smoke
from the Hogback prescribed fire would have affected the Bryson City
monitor.

[Shortoff prescribed fire:]{.underline} The Shortoff prescribed fire was
accomplished using a combination of hand ignition and aerial ignition
from a helicopter. The burn unit covers 1644 acres and elevation varies
from 2000-3900 feet. The burn actually began on March 21, 2007 when the
Forest used hand ignition of fuels on the perimeter of the burn to
prepare control lines used to contain the fire. This began at
approximately 1200 hours and continued until about 1800. The fire was
allowed to burn (in what is called a "backing" fire) through the night
and into the next day. Hand ignition resumed on March 22 at 1000 to
complete preparation of the control lines. It is estimated that 300
acres had burned before aerial ignition began.

Aerial ignition was used on March 22 to treat the interior of the burn
unit, and began at approximately 1345-1400. All ignitions were completed
by 1600 and the active/flaming fire phase ceased in the burn unit about
1700. It is estimated that fuels were consumed on 95 percent of the
area, or 1561 acres. FEPS was used to estimate hourly fine particulate
emissions (Figure 6) and heat release rate from the burn unit. Maximum
emissions from the prescribed fire probably occurred between 1500 and
1700 the afternoon of March 22.

![](media/image6.wmf){width="4.592361111111111in"
height="2.839583333333333in"}

> Figure 6. Hourly fine particulate emissions estimates from the
> Shortoff prescribed fire using the Fire Emissions Production
> Simulator.

National Weather Service forecasts were obtained for the Shortoff
project and the following chart summarizes the parameters from both the
fire weather and spot weather forecasts for the Shortoff prescribed fire
on March 21 and 22.

  ----------------------- ----------------------- -----------------------
  March 21, 2007          Fire Weather Forecast   Spot Weather Forecast
                          (0515)                  (1456 on March 20,
                                                  2007)

  Mixing Height (above    6600                    6400
  mean sea level)                                 

  Transport Winds (miles  From S at 17 mph        from S at 18 mph
  per hour)                                       

  Dispersion              98                      102

  Sky/Weather             Partly Cloudy\*         Partly Cloudy\*

  Surface Temperature     64-69                   Max 68
  (^o^F)                                          

  Relative Humidity (%)   43-48                   Min 50

  Windspeed at 20 ft      From S at 7 mph         From S at 6-9 mph
  above ground (miles per                         
  hour)                                           

  Nightime dispersion                             Decreasing to near zero
  conditions                                      (reflects light
                                                  transport winds and
                                                  mixing height
                                                  decreasing near
                                                  surface)
  ----------------------- ----------------------- -----------------------

\*According to the Georgia Forestry Commission website a Partly Cloudy
day is interpreted to have 30% to 50% cloud cover
(<http://weather.gfc.state.ga.us/Info/WXexp.aspx>).

  ----------------------- ----------------------- -----------------------
  March 22, 2007          Fire Weather Forecast   Spot Weather Forecast
                          (0515)                  (0641)

  Mixing Height (above    6000                    5500
  mean sea level)                                 

  Transport Winds (miles  From SW at 16 mph       from SW at 20 mph
  per hour)                                       

  Dispersion              81                      84

  Sky/Weather             Partly Cloudy\*         Partly Cloudy\*

  Surface Temperature     71-75                   Max 75
  (^o^F)                                          

  Relative Humidity (%)   33-38                   Min 37

  Windspeed at 20 ft      From SW at 6 mph        From SW at 7-12 mph
  above ground (miles per                         
  hour)                                           
  ----------------------- ----------------------- -----------------------

\*According to the Georgia Forestry Commission website a Partly Cloudy
day is interpreted to have 30% to 50% cloud cover
(<http://weather.gfc.state.ga.us/Info/WXexp.aspx>).

Weather forecasts for March 22 predicted transport winds from the SW at
speeds of 16-20 mph, which would have moved smoke from the Shortoff
prescribed fire unit toward Bryson City. Considering that the Shortoff
prescribed fire unit is only 33 miles from Bryson City, smoke could have
traveled to Bryson City in about 2 hours.

Field measurements taken near the burn at Barlow High Top (elevation
2280 feet) on March 22 showed ground level wind speeds of 3-5 mph in the
morning increasing to 8 by afternoon. Surface winds were from the SE
when burning began on March 22, and became variable form SSE, S or SSW
during the afternoon, and shifted to the S by the evening. Perhaps most
important for smoke dispersion is the observation that cloud-cover
increased from about 30% in the morning to 80% at 1600; affecting
stability of the atmosphere. This will be important in the smoke
dispersion modeling discussion that follows.

The nearest representative RAWS station for the Shortoff prescribed fire
unit would be Wayah, (TOPN7, elevation 2160 feet) but data is not
available for March 21 and 22. The next closest station is Tusquitee
(TSQN7, elevation 1000 feet), which is considerably lower than the burn
unit. However, for the record, data from the Tusquitee site is
comparable to the field observations taken at Barlow High Top. Another
nearby site in Jackson County (315902) located at 2800 feet elevation
also matched the field observations at Barlow High Top (Appendix B).

**Smoke Dispersion Modeling**: Atmospheric dispersion models have many
uses. Two that are of particular interest to fire managers are
predictive modeling of smoke dispersion to help inform the decision for
the burn, and retrospective modeling to help understand where and how
smoke actually dispersed. Provided with information about the Hogback
and Shortoff prescribed fires and the weather, it is possible to conduct
dispersion modeling to estimate the direction and ground-level
particulate concentrations within the smoke plumes on March 22, and in
doing so consider the likelihood that smoke from these fires affected
Bryson City air quality monitor.

The VSMOKE-GIS model was run using as much measured or observed
meteorological data as possible, to get post-burn estimates of smoke
dispersion. VSMOKE allows modeling of only one burn at a time, and
assumes that smoke is dispersed to the mixing height, but not above it.
More advanced models will be needed to assess the possibility that: 1)
smoke moved through the mixing height and was dispersed by different
wind conditions, and/or 2) the plumes merged and affected Bryson City
and other downwind communities.

VSMOKE predictions of daytime smoke dispersion from the Hogback and
Shortoff prescribed fires are shown in Figure 7. The colors in the
"plumes" represent different fine particulate concentrations (Appendix
A, EPA Air Quality Index) at ground level for the hour with highest
estimated emissions. For Hogback this occurred at 1600, for Shortoff at
1500. VSMOKE results are most reliable at distances less than 30 miles
downwind; and therefore the plume plots are truncated at 30 miles.
Details of the modeling can be found in the VSMOKE reports for each burn
located in Appendix C.

![](media/image7.jpeg){width="5.9944444444444445in"
height="4.631944444444445in"}

Figure 7. VSMOKE-GIS results showing ground-level fine particulate
concentrations for time of peak emissions from the Shortoff and Hogback
prescribed fires.

The plume plots show that smoke from the Hogback prescribed fire was not
traveling toward Bryson City; the NWS forecast predicted transport winds
from the SW; and observations taken on-site also showed surface winds
from the SW. All indications are that the smoke from the Hogback
prescribed fire probably did not affect Bryson City (located to the east
of the Hogback fire) and no additional analysis is warranted.

On the other hand, the plume plots show that smoke from the Shortoff
prescribed fire was traveling toward Bryson City. VSMOKE shows that
ground level concentrations were elevated for a considerable distance
downwind. The presence of ground-level smoke downwind from the burn was
confirmed by Forest personnel observations (at about 1700) of noticeable
smoke near Topton, NC which is located at the head of the Nantahala
River gorge. Aerial observations of smoke dispersion also indicate that
smoke was moving toward Bryson City from the Shortoff prescribed fire.
During the peak active burning period from about 1430 to 1600, the NC
Division of Forestry spotter plane reported that the smoke was rising to
about 10,000 feet and the plume was going toward Sylva, NC (Jackson
County). However, it should be kept in mind that this is a view of the
plume from above and that a portion of the smoke remains below the
mixing height (research has demonstrated that about 25 percent of the
smoke is dispersed at ground level). At 1630 the helicopter pilot who
was conducting the aerial ignition reported that the smoke column was
rising and dispersing well to the northeast (consistent with predicted
transport winds from the southwest). At 1700 the helicopter pilot
reported that smoke seemed to be dropping down in the Nantahala River
Gorge areas of Cherokee, Macon and Swain Counties (directly in the
modeled plume path shown in Figure 7).

It seems likely that some emissions from the Shortoff prescribed fire
could have been transported to Bryson City. Maximum emissions occurred
at 1500, and predicted transport winds would have moved the plume toward
Bryson City at 16-20 miles per hour. This would put whatever smoke
remained in the "plume" over Bryson City at 1700, the same time that the
air quality monitors registered an increase in fine particulate. Aerial
observers could see a visible plume during the afternoon and early
evening and reported that it was moving in the direction of Bryson City.
They also reported the plume "dropping down" at 1700. About an hour
before sunset (approximately 1700 in March) it is typical for a
surface-based inversion to begin. This inversion tends to trap smoke
closer to the ground and results in the plume appearing to drop or be
pushed toward the earth. Furthermore, emissions/smoke that were below
6000 feet elevation when they reached the Great Smoky Mountains (a
Federally mandated Class 1 area) would have become trapped on the east
side of the mountains and dispersed down slope during the night, which
would include Bryson City.

VSMOKE predicted the maximum ground-level fine particulate
concentrations of 92 micrograms per cubic meter, 25 miles from the
Shortoff prescribed fire (see Appendix C, Shortoff VSMOKE report). This
pattern of dispersion is probably due to the relatively low mixing
height of 1800 feet above ground level (even though this is above US
Forest Service, Region 8 minimum standards) and near neutral stability
at the time when maximum emissions were released. (Weather observations
taken on-site at Barlow High Top showed that cloud cover increased about
10 % each hour from 0900 (30%) to 1600 (80%), changing conditions from
moderately unstable to near neutral between early morning and early
afternoon.) It appears that the mixing height was not adequate to
overcome the near neutral stability conditions and the large amount of
smoke entering the atmosphere over a relatively short period of time.

The HYSPLIT (<http://www.arl.noaa.gov/ready/hysplit4.html>) model was
the second tool used to examine what direction smoke released from the
Shortoff Mountain would travel. HYSPLIT is a complete system for
computing simple air parcel trajectories to complex dispersion and
deposition simulations. The model forecast was operated in the forecast
mode with the smoke released from the burn site at 1500. The HYSPLIT
results predict the smoke released from the burn unit at 1500 would have
reached Bryson City between 1700 and 1800 on March 22, 2007 (Figure 8).

![](media/image8.wmf){width="5.160416666666666in"
height="3.9305555555555554in"}

Figure 8. Predicted trajectory of the smoke released at 1500 (blue arrow
on lower left) from the Shortoff Mountain prescribed fire. Each arrow
shows the approximate location of the smoke dispersion for each hour to
1800 (upper right blue arrow).

**What can we learn from this evaluation?**

Good smoke dispersion requires a balance between adequate atmospheric
conditions and the amount of fuel consumed (and emissions released) over
each hour. If large amounts of fuel are consumed over a short period of
time, the ventilation index must be high (high mixing height and
transport wind speed) and stability class unstable (fewer clouds and
moderate surface winds) in order to achieve maximum dilution and
dispersion.

To demonstrate the effects of mixing height and atmospheric stability on
smoke dispersion we used VSMOKE and the Shortoff prescribed fire inputs
for all parameters; changing only mixing height and/or stability class.
VSMOKE modeling results in the table below show that a change in either
mixing height or stability class results in similar substantial
reductions of particulate matter downwind. Of course the greatest
reductions occur when mixing height increases considerably and the
atmosphere is more unstable. Had the stability class of the atmosphere
been more unstable and mixing height greater on the day of the Shortoff
prescribed fire, then ground level concentrations would have been lower
and the potential impacts to Bryson City decreased or eliminated.

  ------------ ------------- ---------------- -------------- ----------------
                             **Downwind Fine                 
                             Particulate                     
                             Concentrations                  
                             in micrograms                   
                             per cubic                       
                             meter**                         

  **Mixing     **Stability   **At 10 miles**  **At 30        **At 50 miles**
  Height in    Class**                        miles**        
  feet**                                                     

  1800         Near Neutral  170              80             60

  5000         Near Neutral  105              45             35

  1800         Mod Unstable  95               50             40

  5000         Mod Unstable  47               30             27
  ------------ ------------- ---------------- -------------- ----------------

One additional analysis was conducted for this evaluation. The NC
Division of Forestry currently posts Voluntary Smoke Management
Guidelines for prescribed burning on their website
(<http://www.dfr.state.nc.us/fire_control/fire_menu.htm>). We used these
guidelines and found that for the fuel loading (and estimated
consumption) on the Shortoff prescribed fire unit and the weather
conditions on March 22, a mixing height of 5600 feet above ground level
was needed. VSMOKE was run again for the Shortoff prescribed fire unit,
changing only the mixing height from 1800 to 5600 feet above ground
level. Figure 9 shows that higher fine particulate concentrations would
not have extended as far downwind, if the mixing height had been higher
on the day of the burn.

> ![](media/image9.jpeg){width="5.950694444444444in"
> height="4.615277777777778in"}
>
> Figure 9. VSMOKE-GIS modeling results for the Shortoff prescribed fire
> with mixing height increased to 5600 feet above ground level.

**APPENDIX A**

**EPA's Air Quality Index (AQI) for Particulate Matter ~2.5~ (PM~2.5~)
including the breakpoints of PM ~2.5~ concentrations for the Air Quality
Index rankings**

+-----------+----------+-------+--------+-----------+----------------+
| **PM~2.5~ | *        | **    | **Visi | **Level   | **Cautionary   |
| 24-hr     | *PM~2.5~ | Index | bility | of Health | Statements**   |
| Avg.      | 1-hr     | Val   | (Mi    | Concern** |                |
| Conc      | Avg.     | ues** | les)** |           |                |
| entration | Conce    |       |        |           |                |
| (u        | ntration |       |        |           |                |
| g/m^3^)** | (ug      |       |        |           |                |
|           | /m^3^)** |       |        |           |                |
+-----------+----------+-------+--------+-----------+----------------+
| 0.0 --    | 0.0 --   | 0-50  | ##     | ## Good   | None           |
| 15.4      | 40.0     |       |  \> 10 |           |                |
+-----------+----------+-------+--------+-----------+----------------+
| 15.5 --   | 40.1 --  | 51 -- | 5.1 -- | **M       | None           |
| 40.4      | 80.0     | 10    | 10.0   | oderate** |                |
|           |          | 0\*\* |        |           |                |
+-----------+----------+-------+--------+-----------+----------------+
| 40.5 --   | 80.1 --  | 101 - | 3.1 -- | **        | People with    |
| 65.4      | 175.0    | 150   | 5.0    | Unhealthy | respiratory or |
|           |          |       |        | for       | heart disease, |
|           |          |       |        | Sensitive | the elderly,   |
|           |          |       |        | Groups**  | and children   |
|           |          |       |        |           | should limit   |
|           |          |       |        |           | prolonged      |
|           |          |       |        |           | exertion.      |
+-----------+----------+-------+--------+-----------+----------------+
| 65.5 --   | 175.1 -- | 151   | 1.6 -- | **Un      | People with    |
| 150.4     | 300.0    | --    | 3.0    | healthy** | respiratory or |
|           |          | 200   |        |           | heart disease, |
|           |          |       |        |           | the elderly    |
|           |          |       |        |           | and children   |
|           |          |       |        |           | should avoid   |
|           |          |       |        |           | prolonged      |
|           |          |       |        |           | exertion,      |
|           |          |       |        |           | everyone else  |
|           |          |       |        |           | should limit   |
|           |          |       |        |           | prolonged      |
|           |          |       |        |           | exertion.      |
+-----------+----------+-------+--------+-----------+----------------+
| 150.5 --  | 300.1 -- | 201   | 1.0 -- | **Very    | People with    |
| 250.4     | 500      | --    | 1.5    | Un        | respiratory or |
|           |          | 300   |        | healthy** | heart disease, |
|           |          |       |        |           | the elderly    |
|           |          |       |        |           | and children   |
|           |          |       |        |           | should avoid   |
|           |          |       |        |           | any outdoor    |
|           |          |       |        |           | activity,      |
|           |          |       |        |           | everyone else  |
|           |          |       |        |           | should avoid   |
|           |          |       |        |           | prolonged      |
|           |          |       |        |           | exertion.      |
+-----------+----------+-------+--------+-----------+----------------+
| 250.5 +   | 500.0 +  | 301 - | **\<   | **Ha      | Everyone       |
|           |          | 500   | 1.0**  | zardous** | should avoid   |
|           |          |       |        |           | any outdoor    |
|           |          |       |        |           | exertion;      |
|           |          |       |        |           | people with    |
|           |          |       |        |           | respiratory or |
|           |          |       |        |           | heart disease, |
|           |          |       |        |           | the elderly    |
|           |          |       |        |           | and children   |
|           |          |       |        |           | should remain  |
|           |          |       |        |           | indoors.       |
+-----------+----------+-------+--------+-----------+----------------+

Health index rankings are based on 1-hour and 24-hour concentration
averages. EPA developed the health indices based on 24-hour averages.
Idaho State's Department of Environmental Quality developed health
indices based on 1-hour averages.

\*\* An AQI of 100 for PM~2.5~ corresponds to a PM~2.5~ level of 40
micrograms per cubic meter (24-hr avg.).

**APPENDIX B**

  ------------------------------------------------------ ---------- ----------- ---------- ------------ ---------- ------------ ----------- ----------- ----------- -------------- --------------
  ***Jackson County Weather Station (315902) Elevation:                                                                                                                            
  2800 feet***                                                                                                                                                                     

  ***Obs***                                              ***Ob***   ***Dry***   *** ***    ***Wind***              ***Temp***               ***RH%***               ***Precip***   ***Precip***

  ![](media/image10.png){width="0.20833333333333334in"   ***Tm***   ***Tmp***   ***RH***   ***Dir***    ***SP***   ***Max***    ***Min***   ***Max***   ***Min***   ***Dur***      ***Amt***
  height="0.15625in"}***Date***                                                                                                                                                    

  22-Mar-07                                              0          54          79         112          4          66           49          100         52          0              0 

  22-Mar-07                                              1          54          78         90           5          66           49          100         52          0              0 

  22-Mar-07                                              2          53          79         107          4          66           49          100         52          0              0 

  22-Mar-07                                              3          54          82         83           4          66           49          100         52          0              0 

  22-Mar-07                                              4          51          86         40           2          66           49          100         52          0              0 

  22-Mar-07                                              5          53          77         224          3          66           49          99          52          0              0 

  22-Mar-07                                              6          53          82         76           1          66           50          99          52          0              0 

  22-Mar-07                                              7          52          85         220          1          66           51          97          52          0              0 

  22-Mar-07                                              8          54          80         322          1          66           51          88          52          0              0 

  22-Mar-07                                              9          57          75         15           3          66           51          86          52          0              0 

  22-Mar-07                                              10         61          62         8            3          66           51          86          52          0              0 

  22-Mar-07                                              11         64          58         12           3          66           51          86          52          0              0 

  22-Mar-07                                              12         69          45         242          5          69           51          86          45          0              0 

  22-Mar-07                                              13         66          46         198          10         69           51          86          45          0              0 

  22-Mar-07                                              14         69          42         233          7          69           51          86          42          0              0 

  22-Mar-07                                              15         68          41         217          7          69           51          86          41          0              0 

  22-Mar-07                                              16         70          41         222          8          70           51          86          41          0              0 

  22-Mar-07                                              17         66          44         199          8          70           51          86          41          0              0 

  22-Mar-07                                              18         63          49         218          7          70           51          86          41          0              0 

  22-Mar-07                                              19         61          52         216          9          70           51          86          41          0              0 

  22-Mar-07                                              20         59          56         202          4          70           51          86          41          0              0 

  22-Mar-07                                              21         59          59         33           2          70           51          86          41          0              0 

  22-Mar-07                                              22         57          64         165          3          70           51          86          41          0              0 

  22-Mar-07                                              23         52          72         101          3          70           51          86          41          0              0 
  ------------------------------------------------------ ---------- ----------- ---------- ------------ ---------- ------------ ----------- ----------- ----------- -------------- --------------

**APPENDIX C**

**Hogback Prescribed Fire** (Polk/Monroe County, TN) on the Ocoee
District of the Cherokee National Forest (Assumes 1700 acres of 1875
were blackened)

**VSMOKE-GIS results appear in Figure 7 of the main paper.**

Prepared by: Cindy Huber

Date: 8/8/2007

The smoke dispersion modeling analysis (using VSmoke and/or VSmoke-GIS)
for this project was performed for 1130.0 acres to be burned on
03/22/2007 at the time period of 1600 hours. This time period has
daytime dispersion characteristics to disperse the pollutants from the
fire. The location of the fire is at approximately 35.285 degrees
latitude and -84.473 degrees longitude (356653.011 meters east and
1250873.42 meters north using US Albers projection). The emission rate
of PM2.5 (fine particles) this hour was 1022.0 grams/second, and carbon
monoxide was 12605.3 grams/second. The heat release rate was 388911.4
megawatts. Both emission rates and the heat release rates were
calculated using the Fire Emission Production Simulator (FEPS) model.
The estimated background concentration of fine particles and carbon
monoxide of the air carried with the winds into the fire are 20
micrograms/cubic meter and 5 parts per million, respectively. The
proportion of the smoke subject to plume rise was -0.75 percent, which
means 75 percent of the smoke is being dispersed gradually as it rises
to the mixing height, and 25 percent is dispersed at ground level.

The meteorological conditions used in this model run were:

1.) Mixing height was 4000 feet above ground level (AGL).

2.) Transport wind speed, and surface wind speed were 20 and 7 miles per
hour, respectively.

3.) The sky had 30 percent cloud cover, and the clouds were located 5000
feet above the ground.

4.) Surface temperature was 78 degrees Fahrenheit, and the relative
humidity was 38 percent.

5.) The calculated stability class from VSmoke was slightly unstable.

The VSmoke model produces three types of outputs that estimate: a.) The
ability of the atmosphere to disperse smoke and the likelihood the smoke
will contribute to fog formation, b.) Downwind concentrations of
particulate matter and carbon monoxide, and c.) Visibility conditions
downwind of the fire.

The Dispersion Index (DI) is an estimate of the ability of the
atmosphere to disperse smoke to acceptably low average concentrations
downwind of one or more fires. This value could represent an area of
approximately 1000 square miles under uniform weather conditions.
Typically, the Dispersion Index value should be greater than 30 when
igniting a large number of acres within an area. The calculated
Dispersion Index value was 75, which predicts the atmosphere has a good
capacity to disperse smoke.

Combining the Dispersion Index and relative humidity values provide an
estimate (like is used in insurance actuary tables) of the likelihood of
the smoke contributing to fog formation. The Low Visibility Occurrence
Risk Index (LVORI) ranges from 1 (lowest risk) to 10 (greatest risk) and
usually you want the value to be less than 4. The base line risk of
having low visibility as a result of smoke contributing to fog formation
is about 1 in 1000 accidents. The Low Visibility Occurrence Risk Index
value for this VSmoke analysis was 1 and this is equal to the base line.

High concentrations of particulate matter, especially fine particles
(PM2.5), and carbon monoxide can have a negative impact on people\'s
health. The Environmental Protection Agency has developed a color coding
system called the Air Quality Index (AQI) to help people understand what
concentrations of air pollution may impact their health. When the AQI
value is color code orange then people who are sensitive to air
pollutants, or have other health problems, may experience health
effects. This means they are likely to be affected at lower levels than
the general public. Sensitive groups of people include the elderly,
children, and people with either lung disease or heart disease. The
general public is not likely to be affected when the AQI is code orange.
Everyone may begin to experience health effects when AQI values are
color coded as red. People who are sensitive to air pollutants may
experience more serious health effects when concentrations reach code
red levels.

This analysis shows the air quality at downwind distances less than 0.98
miles from the edge of the fire may have a 1-hour particulate matter
concentrations predicted to be code red or worse, while distances less
than 4.94 miles are predicted to be code orange or worse. At distances
less than 656 feet from the edge of the fire the one-hour carbon
monoxide concentrations are predicted to be code red or worse, and
distances less than 0.25 miles from the fire are predicted to be code
orange or worse.

![](media/image11.png){width="4.620138888888889in"
height="3.1083333333333334in"}

![](media/image12.png){width="4.624305555555556in" height="3.525in"}

Smoke can also have an impact on how far and how clearly we can see on a
highway or in viewing scenery. The fine particles in the smoke are known
to be able to scatter and absorb light, which can reduce visibility
conditions. The visibility estimates from VSmoke are valid only when the
relative humidity is less than 70 percent. Also, the visibility
estimates assume the smoke is passing in front of a person who is
looking through the plume of smoke. The visibility thresholds used for
this modeling analysis were to maintain a contrast ratio of greater than
0.05 and a visibility distance of 0.25 miles. Visibility conditions may
exceed the threshold less than 328 feet from the edge of the fire.

![](media/image13.png){width="4.496527777777778in"
height="3.0256944444444445in"}

The VSMOKE-GIS model estimates the distance downwind of the fire that
pre-selected fine particulate matter concentrations (41, 81, 176, 301,
and 501 micrograms per cubic meter) are predicted to occur. The map of
results can be viewed in Figure 7 of the main report. The VSmoke-GIS
analysis had daytime dispersion characteristics to disperse the
pollutants from the fire and this is the same as the VSmoke analysis.
The downwind spacing interval was set at 0.025 kilometers, and the model
ceased making downwind estimates at 30 miles from the edge of the fire.
The stability class used for the VSmoke-GIS analysis was slightly
unstable and this is the same as the calculated stability from VSmoke.

**Shortoff Prescribed Fire** (Clay County, NC) on the Tusquitee District
of the Nantahala National Forest (Assumes 95% of the acres in the burn
unit were blackened; 1561 acres)

**VSMOKE-GIS results appear in Figure 7 of the main paper.**

Prepared by: Cindy Huber

Date: 8/6/2007

The smoke dispersion modeling analysis (using VSMOKE and/or VSMOKE-GIS)
for this project was performed for 931 acres to be burned on 3/22/2007
at the time period of 1500 hours. This time period has daytime
dispersion characteristics to disperse the pollutants from the fire. The
location of the fire is at approximately 35.109 degrees latitude and
-83.868 degrees longitude (412096.048 meters east and 1231394.321 meters
north using US Albers projection). The emission rate of PM2.5 (fine
particles) this hour was 1695.1 grams/second, and carbon monoxide was
20788.5 grams/second. The heat release rate was 708123.5 megawatts. Both
emission rates and the heat release rates were calculated using the Fire
Emission Production Simulator (FEPS) model. The estimated background
concentration of fine particles and carbon monoxide of the air carried
with the winds into the fire are 20 micrograms/cubic meter and 5 parts
per million, respectively. The proportion of the smoke subject to plume
rise was -0.75 percent, which means 75 percent of the smoke is being
dispersed gradually as it rises to the mixing height, and 25 percent is
dispersed at ground level.

The meteorological conditions used in this model run were:

1.) Mixing height was 1800 feet above ground level (AGL), for the upper
elevations of the burn unit (from the spot weather forecast).

2.) Transport wind speed (from the spot weather forecast) and surface
wind speed (from field observations) were 20 and 8 miles per hour,
respectively.

3.) The sky had 70 percent cloud cover (based on field observations and
the satellite image in Figure 1 of the main report), and the clouds were
located 5000 feet above the ground.

4.) Surface temperature was 74 degrees Fahrenheit, and the relative
humidity was 45 percent (both from on-site measurements).

5.) The calculated stability class from VSMOKE was near neutral.

The VSMOKE model produces three types of outputs that estimate: a.) The
ability of the atmosphere to disperse smoke and the likelihood the smoke
will contribute to fog formation, b.) Downwind concentrations of
particulate matter and carbon monoxide, and c.) Visibility conditions
downwind of the fire.

The Dispersion Index (DI) is an estimate of the ability of the
atmosphere to disperse smoke to acceptably low average concentrations
downwind of one or more fires. This value could represent an area of
approximately 1000 square miles under uniform weather conditions.
Typically, the Dispersion Index value should be greater than 30 when
igniting a large number of acres within an area. The calculated
Dispersion Index value was 38, which predicts the atmosphere has a fair
to good capacity to disperse smoke.

Combining the Dispersion Index and relative humidity values provide an
estimate (like is used in insurance actuary tables) of the likelihood of
the smoke contributing to fog formation. The Low Visibility Occurrence
Risk Index (LVORI) ranges from 1 (lowest risk) to 10 (greatest risk) and
usually you want the value to be less than 4. The base line risk of
having low visibility as a result of smoke contributing to fog formation
is about 1 in 1000 accidents. The Low Visibility Occurrence Risk Index
value for this VSMOKE analysis was 1 and this is equal to the base line.

High concentrations of particulate matter, especially fine particles
(PM2.5), and carbon monoxide can have a negative impact on people\'s
health. The Environmental Protection Agency has developed a color coding
system called the Air Quality Index (AQI) to help people understand what
concentrations of air pollution may impact their health. When the AQI
value is color code orange then people who are sensitive to air
pollutants, or have other health problems, may experience health
effects. This means they are likely to be affected at lower levels than
the general public. Sensitive groups of people include the elderly,
children, and people with either lung disease or heart disease. The
general public is not likely to be affected when the AQI is code orange.
Everyone may begin to experience health effects when AQI values are
color coded as red. People who are sensitive to air pollutants may
experience more serious health effects when concentrations reach code
red levels.

This analysis shows the air quality at downwind distances less than 9.85
miles from the edge of the fire may have a 1-hour particulate matter
concentrations predicted to be code red or worse, while distances less
than 31.14 miles are predicted to be code orange or worse. At distances
less than 0.78 miles from the edge of the fire the one-hour carbon
monoxide concentrations are predicted to be code red or worse, and
distances less than 1.96 miles from the fire are predicted to be code
orange or worse.

![](media/image14.png){width="4.490277777777778in"
height="3.0131944444444443in"}

![](media/image15.png){width="4.75in" height="3.609027777777778in"}

Smoke can also have an impact on how far and how clearly we can see on a
highway or in viewing scenery. The fine particles in the smoke are known
to be able to scatter and absorb light, which can reduce visibility
conditions. The visibility estimates from VSMOKE are valid only when the
relative humidity is less than 70 percent. Also, the visibility
estimates assume the smoke is passing in front of a person who is
looking

through the plume of smoke. The visibility thresholds used for this
modeling analysis were to maintain a contrast ratio of greater than 0.05
and a visibility distance of 0.25 miles. Visibility conditions may
exceed the threshold less than 413 feet from the edge of the fire.

![](media/image16.png){width="4.607638888888889in" height="3.1in"}

The VSMOKE-GIS model estimates the distance downwind of the fire that
pre-selected fine particulate matter concentrations (41, 81, 176, 301,
and 501 micrograms per cubic meter) are predicted to occur. The map of
results can be viewed in Figure 7 of the main report. The VSMOKE-GIS
analysis used daytime dispersion characteristics to disperse the
pollutants from the fire and this is the same as the VSMOKE analysis.
The downwind spacing interval was set at 0.025 kilometers, and the model
ceased making downwind estimates at 30 miles from the edge of the fire.
The stability class used for the VSMOKE-GIS analysis was near neutral
and this is the same as the calculated stability from VSMOKE.

**Shortoff Prescribed Fire** (Clay County, NC) on the Tusquitee District
of the Nantahala National Forest (Assumes 95% of the acres in the burn
unit were blackened; 1561 acres)

**Modeled to show dispersion under the NC Voluntary Smoke Management
Guidelines, VSMOKE-GIS results appear in Figure 8 of the main paper.**

Prepared by: Cindy Huber

Date: 8/8/2007

The smoke dispersion modeling analysis (using VSmoke and/or VSmoke-GIS)
for this project was performed for 931 acres to be burned on 3/22/2007
at the time period of 1500 hours. This time period has daytime
dispersion characteristics to disperse the pollutants from the fire. The
location of the fire is at approximately 35.109 degrees latitude and
-83.868 degrees longitude (412096.048 meters east and 1231394.321 meters
north using US Albers projection). The emission rate of PM2.5 (fine
particles) this hour was 1695.1 grams/second, and carbon monoxide was
20788.5 grams/second. The heat release rate was 708123.5 megawatts. Both
emission rates and the heat release rates were calculated using the Fire
Emission Production Simulator (FEPS) model. The estimated background
concentration of fine particles and carbon monoxide of the air carried
with the winds into the fire are 20 micrograms/cubic meter and 5 parts
per million, respectively. The proportion of the smoke subject to plume
rise was -0.75 percent, which means 75 percent of the smoke is being
dispersed gradually as it rises to the mixing height, and 25 percent is
dispersed at ground level.

The meteorological conditions used in this model run were:

1.) Mixing height was 5600 feet above ground level (AGL). This is the
mixing height that would be required under the current Voluntary Smoke
Guidelines in North Carolina (This assumes consumption of 9000 tons of
fuel on a day with fair to good smoke dispersion or a Burn Category 5
day. Burn Category 5 requires a ventilation rate of 112,000 or higher,
and carries a warning of Burn with Caution, Good Smoke Dispersion, and
Potential Severe Fire Behavior. Given the transport wind speed of 20
mph, a mixing height of 5600 would be needed to get a ventilation rate
of 112,000.)

2.) Transport wind speed, and surface wind speed were 20 and 8 miles per
hour, respectively.

3.) The sky had 70 percent cloud cover, and the clouds were located 5000
feet above the ground.

4.) Surface temperature was 74 degrees Fahrenheit, and the relative
humidity was 45 percent.

5.) The calculated stability class from VSmoke was near neutral.

The VSmoke model produces three types of outputs that estimate: a.) The
ability of the atmosphere to disperse smoke and the likelihood the smoke
will contribute to fog formation, b.) Downwind concentrations of
particulate matter and carbon monoxide, and c.) Visibility conditions
downwind of the fire.

The Dispersion Index (DI) is an estimate of the ability of the
atmosphere to disperse smoke to acceptably low average concentrations
downwind of one or more fires. This value could represent an area of
approximately 1000 square miles under uniform weather

conditions. Typically, the Dispersion Index value should be greater than
30 when igniting a large number of acres within an area. The calculated
Dispersion Index value was 58, which predicts the atmosphere has a good
capacity to disperse smoke.

Combining the Dispersion Index and relative humidity values provide an
estimate (like is used in insurance actuary tables) of the likelihood of
the smoke contributing to fog formation. The Low Visibility Occurrence
Risk Index (LVORI) ranges from 1 (lowest risk) to 10 (greatest risk) and
usually you want the value to be less than 4. The base line risk of
having low visibility as a result of smoke contributing to fog formation
is about 1 in 1000 accidents. The Low Visibility Occurrence Risk Index
value for this VSmoke analysis was 1 and this is equal to the base line.

High concentrations of particulate matter, especially fine particles
(PM2.5), and carbon monoxide can have a negative impact on people\'s
health. The Environmental Protection Agency has developed a color coding
system called the Air Quality Index (AQI) to help people understand what
concentrations of air pollution may impact their health. When the AQI
value is color code orange then people who are sensitive to air
pollutants, or have other health problems, may experience health
effects. This means they are likely to be affected at lower levels than
the general public. Sensitive groups of people include the elderly,
children, and people with either lung disease or heart disease. The
general public is not likely to be affected when the AQI is code orange.
Everyone may begin to experience health effects when AQI values are
color coded as red. People who are sensitive to air pollutants may
experience more serious health effects when concentrations reach code
red levels.

This analysis shows the air quality at downwind distances less than 4.94
miles from the edge of the fire may have a 1-hour particulate matter
concentrations predicted to be code red or worse, while distances less
than 15.61 miles are predicted to be code orange or worse. At distances
less than 0.62 miles from the edge of the fire the one-hour carbon
monoxide concentrations are predicted to be code red or worse, and
distances less than 1.24 miles from the fire are predicted to be code
orange or worse.

![](media/image17.png){width="4.613888888888889in"
height="3.095833333333333in"}

![](media/image18.png){width="4.624305555555556in"
height="3.5131944444444443in"}

Smoke can also have an impact on how far and how clearly we can see on a
highway or in viewing scenery. The fine particles in the smoke are known
to be able to scatter and absorb light, which can reduce visibility
conditions. The visibility estimates from VSmoke are valid only when the
relative humidity is less than 70 percent. Also, the visibility
estimates assume the smoke is passing in front of a person who is
looking through the plume of smoke. The visibility thresholds used for
this modeling analysis were to maintain a contrast ratio of greater than
0.05 and a visibility distance of 0.25 miles. Visibility conditions may
exceed the threshold less than 413 feet from the edge of the fire.

![](media/image19.png){width="4.620138888888889in"
height="3.1083333333333334in"}

The VSMOKE-GIS model estimates the distance downwind of the fire that
pre-selected fine particulate matter concentrations (41, 81, 176, 301,
and 501 micrograms per cubic meter) are predicted to occur. The map of
results can be viewed in Figure 8 of the main report. The VSmoke-GIS
analysis had daytime dispersion characteristics to disperse the
pollutants from the fire and this is the same as the VSmoke analysis.
The downwind spacing interval was set at 0.025 kilometers, and the model
ceased making downwind estimates at 30 miles from the edge of the fire.
The stability class used for the VSmoke-GIS analysis was near neutral
and this is the same as the calculated stability from VSmoke.