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Sawtooth
Wilderness Area |
Site Name
IMPROVE: SAWT1
Region
Central Rockies
Terrain
Terrain is shown in the 2 km terrain map and the 20 km terrain map.
The Sawtooth Wilderness Area occupies 217,088 acres in the western portion
of the Sawtooth National Recreation Area in central Idaho. The Wilderness
Area consists primarily of the Sawtooth Mountains, a central headwaters
source that includes headwaters of the North and Middle Forks of the Boise
River, South Fork of the Payette River, and the Salmon River. Terrain is
steep craggy peaks and deep valleys. Elevations range from 1,800 to 2,000 m
(~6,000 ft) where the Payette South Fork and Boise Middle Forks exit the
Wilderness on the west side, to 3,285 m (10,776 ft) at the summit of
Thompson Peak. It includes approximately 40 peaks with elevations of 10,000
ft or higher.
The IMPROVE site representing the Sawtooth Wilderness is SAWT1, located in
the Stanley Basin 4 km outside of the northeastern Wilderness boundary, at
the USFS Stanley Warehouse, elevation 1,980 m (6,494 ft). It is 60 to 80 m
(~200 ft) lower in elevation than the Wilderness boundary.
Representativeness
SAWT1 is representative of aerosol characteristics in Sawtooth Wilderness
when the atmosphere is well mixed. It should be generally representative of
lower Wilderness elevations at all times. The monitoring site is in the
Stanley Basin, a mountain basin with bottom elevation near 1,930 m (6,330
ft) that is subject to strong surface radiation inversions, especially in
the winter. Lowest nearby Wilderness locations are approximately 2,160 m
(7,080 ft) and higher. SAWT1 is 50 m (150 ft) above the floor of the basin
and could at times be beneath the inversion and disconnected from air at
higher Wilderness elevations.
Nearby Population/Industrial Centers and Local Sources
This central Idaho Wilderness area is remote from any major source regions.
The nearest population centers are Boise and the Snake River Plain, 130 km
(80 mi) straight line distance to the southwest and south with major
intervening mountainous terrain. Locally, the site may be affected by
pollutant accumulation in the basin, including smoke from wild and
prescribed vegetative burning.
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. SAWT1 is in a fairly isolated and
essentially enclosed basin. The
Stanley Idaho
RAWS should be very representative of concurrent aerosol monitoring at
SAWT1, although the site was not installed until August 2002. The
Horton Peak
Idaho RAWS site is at a high exposed ridge location across the Salmon
River valley from the southern Wilderness boundary and may give a little
better representation of regional wind flow concurrent with aerosol
monitoring.
The closest and most representative upper air site is at Boise Idaho
Municipal (BOI). 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, with frequent easterly flows from the Canadian interior in
the winter. Lower basin elevations such as the SAWT1 sit may frequently be
shielded from synoptic flows and upper level transport because of
surrounding mountains and strong surface inversion episodes. This is
especially true during periods of weak synoptic forcing and regional
stagnation.
Inversions/Trapping
Stanley Basin is subject to strong nocturnal surface based temperature
inversions that can trap pollutants locally. SAWT1 is at a relatively low
level within the basin and may at times be beneath the inversion, separated
from upper level synoptic flow that may cross the basin without stirring or
mixing with the air below. In the summer the inversion is typically broken
on a daily basis by convection, but in the winter cold pools may persist for
days because surface heating is insufficient to break up the inversion. In
the summer regional subsidence inversions during periods of high pressure
and stagnation can result in regional aerosol buildup over periods of days.
High regional aerosol concentrations may occur during summertime stagnation
and subsidence inversion periods in conjunction with western wildland fires.
Climatological Statistics
Stanley Idaho
climate data are representative of SAWT1 and the Stanley Basin. Other
Idaho Climate
Summaries are available from the
Western Regional Climate Center.
Meteorological Indicators for Local Sources
Keywords
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