|
| |
|
Task 1:
Refined Tribal Assessments by Region |
| |
| 1.4 Discussion |
| |
| Overall there was a decrease
in the representative distances in 12 out of 15 regions from this
study compared to the initial effort. On average the distance decreased
around 30 percent. Keep in mind that in the first effort a correlation analysis was done
for only 8 out of 15 regions and a 150 km representative
distance was chosen as a default value for the remaining 7 regions. Considering only those regions that had enough
sites in phase I with this effort, the decrease was around 14 percent. The California Coast, Colorado Plateau and North
Central Lowland Plains regions showed an increase from last time. The
Northern Great Plains region varied the least with a decrease of only 7
percent. The North Central Lowland Plains changed the most, increasing
by 90 percent. |
| |
| Region |
Phase II |
Phase I |
Change |
| California Coast Ranges |
239 |
150 |
59% |
| Cascade Range |
107 |
139 |
-23% |
| Central Rocky Mountains |
96 |
140 |
-32% |
| Colorado Plateau |
125 |
91 |
38% |
| Columbia Plateau |
106 |
150 |
-29% |
| Great Basin |
98 |
150 |
-34% |
| Klamath Mountains |
101 |
150 |
-33% |
| Mexican Highlands |
129 |
161 |
-20% |
| North Central Lowland Plains |
285 |
150 |
90% |
| Northern Great Plains |
195 |
210 |
-7% |
| Sierra Nevada Range |
103 |
130 |
-21% |
| Southern California Ranges |
101 |
150 |
-33% |
| Southern Pacific Rain Forests |
92 |
150 |
-38% |
| Southern Rocky Mountains |
90 |
142 |
-37% |
| Southwest Deserts |
96 |
150 |
-36% |
|
| Variations in the
representative distances could be attributable from one or more of the
following factors: |
 | variations in the aerosol compositions from variations in meteorology |
| variations in aerosol composition from emission changes such as
frequency of regional and local fires, and dust events |
| change in the methodology to include more sites (minimum 4 sites in
each region) |
| changes in the network (a few new sites started in later years) |
| slight changes in the reported IMPROVE concentrations over time in the
database |
|
| |
| 1.4.1 Tribal areas not
represented |
| |
| A
summary table tabulates the tribes
that have some or all of their area not represented by an IMPROVE or IMPROVE
protocol site. Only three regions had all tribal areas represented by
a site. The California Central Valley region is the only region with no
site. There are seven tribes located in this region, covering a large
area from northern California to the San Joaquin Valley. The Great
Basin region had the most tribal areas not represented, 29. Many of
the tribes in the Great Basin region are located in northcentral Nevada, far
from a site. There were 15 tribes in the Mexican Highlands regions
identified as not represented. However, the majority of the tribes are
located in northern New Mexico in the northern extent of the region. A
slight change in the definition of the physiographic region would pull in
the northern New Mexican IMPROVE sites, Bandelier (BAND1), and San Pedro
Parks (SAPE1). |
| |
| 1.4.2 Effects of removing
the Walker River site |
| |
| The Walker River tribal site,
WARI1, was discontinued in November 2005 after collecting over two years of
data in
Schurz, Nevada. We performed an analysis to compare the
regional correlations with and without the WARI1 site. Recall that the
other sites in the Great Basin region include Death Valley National Park
(DEVA1), Great Basin National Park (GRBA1), Zion National Park (ZION1 and
ZICA1), and Lava Beds National Monument (LABE1).
Including the
WARI1 site, the representative distance in the Great Basin region was 98 km.
After removing the WARI1 site, the representative distance increased
to 180 km. An increase in the region representative distance implies
that the WARI1 site may not correlate with the other sites in one or more
fine particle species.
If we compare 2004 data from all sites in the
region a few differences stand out. Note that 2004 is the only complete
calendar year from WARI1 to compare with the other sites. During that
year the WARI site has the highest worst 20% extinction of all the sites at
46.5 Mm-1. It also has the highest best 20% extinction at 10.1 Mm-1,
which is about twice that of the second highest site, DEVA1. If we
examine how the fraction of each
species contributes to the total extinction over time, it shows that the
WARI1 site has a higher winter time nitrate component compared to the other Great Basin region sites
in 2004 and 2005 (not shown). This is also reflected in the
worst 20% days. This is not surprising since the site is located
in a small town with some limited agricultural activities along the Walker
River. Some of the episodes that affected WARI1,
similarly affected DEVA1 and to some extent the ZICA1 site. All of the
Great Basin region sites experience spring high wind events and its
accompanying dust. All sites except LABE and DEVA, have their highest
aerosol extinction day in the spring. The maximum fine soil
concentration sample at WARI1 (23.25 µg/m3) also occurred at the same time
as the maximum at DEVA1 (11.58 µg/m3). This strong dust signature occurs at
least once a year usually from southerly moving cold front bring high winds
to the surface. This can be seen clearly from satellites. The Great Basin
region covers a large area, including the majority of the state of Nevada and
a large
portion of western Utah. The Walker River tribal site is located in the west-central
portion of the region, not covered by another IMPROVE or IMPROVE protocol
site. The closest site to WARI1 is the Hoover Wilderness site (HOOV1)
at 104 km to the southwest in the Sierra Nevada Range region. The
following table lists the tribes
in the Great Basin region that are not represented by an IMPROVE site as a
result of this site shutting down. |
| |
| 1.4.3 Effects of removing
the Spokane site |
|
| The Spokane tribal site,
SPOK1, was discontinued in June 2005 after collecting over three full
calendar years of
data near
Ford, Washington. We performed an analysis to compare the
regional correlations with and without the SPOK1 site. Recall that the
other sites in the Columbia Plateau region include Columbia River Gorge
(CORI1), Craters of the Moon (CRMO1), Hells Canyon (HECA1), Jarbidge
Wilderness (JARB1) and Starkey (STAR1).
Including the
SPOK1 site, the representative distance in the Columbia Plateau region was
106 km.
After removing the SPOK1 site, the representative distance decreased
slightly to 102 km. A small change of 4 km indicates that the SPOK1 site correlates
well with the other sites. Correlations plots are shown
here.
|
| |
| |
| |
Last updated 5 November 2007
|
