| |
Bridger Wilderness Area |
(Also see
Fitzpatrick Wilderness)
Site Name
IMPROVE:
BRID1
CASTNET: PND165 (Pinedale Wyoming)
Region
Central Rockies
Terrain
Terrain is shown in the 2 km terrain
map and the 20 km terrain
map.
The 428,169-acre Bridger Wilderness is located on the west slope of the Wind
River Range in Wyoming along the Continental Divide that constitutes its
eastern border. It includes the head of the Green River that drains most of
the west side of the Wind River Range. The Wilderness forms a triple divide
for three major western watersheds: the Columbia River, the Colorado River,
and the Missouri River. Wilderness terrain is essentially steep mountains
and valleys from the crest of the Continental Divide down to west slope
elevations near 2,400 m (7,900 ft). The Wind River Range includes numerous
peaks exceeding ~ 4,000 m (13,000 ft), the highest being Gannett Peak,
elevation 4,209 m (13,804 ft) on the boundary between the Bridger Wilderness
and the adjacent Fitzpatrick Wilderness to the east. The Wind River Range is
the eastern side of the upper Green River Basin, elevation ~ 2,300 m (7,544
ft) at river level.
The IMPROVE site representing the Bridger and Fitzpatrick Wildernesses is
BRID1, located at the White Pine Ski Area, 15 km (10 mi) northeast of
Pinedale Wyoming and 3 km outside of the Bridger Wilderness boundary. The
BRID1 monitoring site is situated on a small hilltop in a high basin on the
west slope of the Wind River Range at an elevation of 2,607 m (8,551 ft). It
is ~ 350 m (1,150 ft) above Fremont Lake 2 km to the west, and roughly the
same distance below the elevation of the nearest Bridger Wilderness boundary
to the northeast. It is 420 m (1,380 ft) higher than the upper Green River
Basin town of Pinedale. The Pinedale
Wyoming CASTNET site PND165 is located 5 km (3 mi) southwest of BRID1
and 219 m (718 ft) lower, elevation 2,388 m (7,833 ft).
Representativeness
The BRID1 IMPROVE site is at mid elevation on the west slope of the Wind
River Range, above Fremont Lake and the upper Green River Basin to the west
and near the lower range of Bridger Wilderness elevations. It should be very
representative of aerosol characteristics in the Wilderness and the region
generally. Because of the wide range of Wilderness elevations it may at
specific times be less representative of specific Wilderness locations such
as valley bottoms or high elevation ridges and summits separated from the
monitoring site by an intervening stable atmospheric layer.
Nearby Population/Industrial Centers and Local Sources
Salt Lake City is ~ 350 km (220 mi) southwest of BRID1. The Idaho
Falls/Pocatello area in the eastern Snake River Plain is ~ 200 km (120 mi)
west. Southwestern Wyoming is relatively highly industrialized, with a group
of five large trona plants, several sweet and sour gas plants, the Jim
Bridger and Naughton coal fired power plants that have undertaken emission
control measures in recent years, and other point sources associated with
natural gas production and transportation. The Jim Bridger Power Plant is
near Point of Rocks, 200 km (120 mi) south-southeast of BRID1. The Naughton
Power Plant is near Kemmerer, 180 km (110 mi) south-southwest. Results from
a study of air impacts on the Bridger and Fitzpatrick Wilderness Areas
resulting from southwest Wyoming and other sources, sponsored by the
Southwest Wyoming Technical Air Forum, is available at the
Wyoming DEQ Visibility webpage.
Highest aerosol concentrations at BRID1 from local/regional sources may
occur during regional wildfire events.
Nearby Meteorological Network Monitoring Stations
Nearby meteorological monitoring network stations are shown in the data
network map and at the
US Climate Archive
and RAWS station US Climate
Archive sites. The Pinedale
Wyoming CASTNET site PND165 is near BRID1 and should provide the best
representation of local meteorology concurrent with BRID1 aerosol
monitoring. The nearest first order NWS site is at Lander Wyoming, 90 km (60
mi) east of BRID1 in the upper Wind River basin east of the Continental
Divide. Historical data for this and other regional first order NWS stations
are available via the EPA
Technology Transfer Network website.
The closest upper air site is at Riverton Wyoming (RIW). This and other
upper air sites are accessible via the
University of Wyoming Dept
of Atmospheric Science web page.
Wind and Transport Patterns
Regionally, wind patterns and transport flows are dominated by westerly
synoptic flows. During the winter, as the Pacific High weakens and retreats
southward, more easterly transport flows from the central U.S. and Canada
are common. Surface topographic features modify this pattern locally.
Monthly Lander Wyoming wind roses
are indicative of the pattern, with southwesterly flow predominant at this
surface station and an additional significant southeasterly component in the
winter. Note that these surface wind patterns may differ from upper level
winds because of local terrain effects. Aerosol transport from distant
source regions to the BRID1 monitoring site may most often be associated
with predominantly westerly to southwesterly synoptic flow. Locally, BRID1
may see daytime mesoscale upslope flow from the south or west associated
with mountain valley circulation in the adjacent upper Bighorn River basin.
Surface wind direction frequencies based on 1996-2002 data from the
Pinedale Wyoming CASTNET site,
south of BRID1 and at a lower elevation, are shown in
Pinedale Wyoming wind roses.
A diurnal upslope/drainage pattern is evident; on an annual basis nighttime
low speed drainage flow is from higher terrain to the east-northeast, and
daytime upslope/synoptic flows are from the west-northwest. A wintertime
southeast synoptic flow component is evident.
Inversions/Trapping
BRID1 is at a location on the western slope of the Wind River Range, 350 m
higher than Fremont Lake to the west and more than 420 m above the floor of
the upper Green River Basin and the town of Pinedale. It is probably above
most strong winter surface inversions based at these lower elevations.
Afternoon mixing over the upper Green River Basin may extend upward to the
monitoring site on warm days, bringing basin air to the site. In the summer
regional subsidence inversions during periods of high pressure and
stagnation can result in widespread aerosol buildup over periods of days.
High summertime aerosol concentrations at BRID1 may result from regional
sources such as western wildland fires in conjunction with such episodes.
Climatological Statistics
Climate data derived from period of record measurements at the
Pinedale Wyoming CASTNET site
should be typical of trends at BRID1.
Lander Wyoming
Normals Means and Extremes are more representative of lower valley
bottom locations. Other
Wyoming Climate
Summaries are available from the
Western Regional Climate Center.
Meteorological Indicators for Local Sources
Keywords
|
Last updated 16 December 2004
|