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Craters of the Moon Wilderness Area |
Site Name
IMPROVE: CRMO1
Region
Columbia Plateau
Terrain
Terrain is shown in the 2 km terrain map and the 20 km terrain map.
The Craters of the Moon Wilderness area occupies 43,243 acres, over 80% of
the Craters of the Moon National Monument
along the northern edge of eastern Snake River Plain, a large geographic
area that spans most of southern Idaho. The Snake River Plain is bounded on
the north by the central Idaho mountains with elevations up to 3,000 m
(10,000 ft) and on the south by several ranges with elevations up to 2,100 m
(7,000 ft). Although the Snake River Plain is a distinct depression it is a
physiographic extension of the Columbia Plateau that covers most of eastern
Washington and Oregon. In places, it is 60 miles wide. Its west to east
orientation results in unimpeded exposure to surface winds from these
directions. Within the Wilderness Area, terrain consists of scattered
islands of volcanic cinder cones and sagebrush. Elevations range from the
plain elevation of about 1,500 m (5,000 ft) to 1,986 m (6,515 ft) at the top
of Big Cinder Butte. Terrain is generally flat to the south and west.
The IMPROVE site representing Craters of the Moon Wilderness is CRMO1,
located near the National Park Service Visitors Center. Site elevation is
1,817 m (5,960 ft).
Representativeness
CRMO1 is in an elevated well-exposed location and data from the site should
be very representative of aerosol concentrations and composition at
Wilderness locations and in the eastern Snake River Plain generally.
Nearby Population/Industrial Centers and Local Sources
The Snake River Plain is a large agricultural region extending to Boise and
Treasure Valley 300 km (200 mi) west, Idaho Falls and the upper Snake River
Plain 100 km (60 mi) east, and Twin Falls and Magic Valley some 80 km (50
mi) south from CRMO1. Agricultural related emission sources include stubble
field burning and plowing. Largest urban areas, with associated vehicle and
other urban emissions are Boise, Twin Falls, and Idaho Falls/Pocatello.
Other emission sources include the Idaho National Engineering Laboratory (INEL),
a DOE nuclear research center 25 km (15 mi) east of CRMO1 that has several
permitted point sources of NOx and SO2, and large mineral and chemical
plants in the Pocatello area, 100 km (60 mi) southeast. High aerosol
concentrations may result from wildland fires.
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
Arco Idaho RAWS
site is 23 km (14 mi) northeast of CRMO1 at similar elevation (1,640 m,
5,380 ft) and exposure and should provide the best hourly meteorological
data concurrent with aerosol monitoring at CRMO1.
A dense network of meteorological observing stations operates at INEL. These
stations have provided data for several climatological studies focused on
transport and diffusion referenced in Stewart et al, 2001.
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 Patterns
Regionally, wind patterns and transport flows are dominated by westerly
synoptic flows, with frequent easterly flows in the winter. In the eastern
Snake River Plain near CRMO1 these are channeled by the Plain orientation to
flows from either the southwest or northeast. This pattern is evident in
long-term monthly
Pocatello Idaho wind roses. With weak synoptic forcing, flow patterns in
the eastern Snake River Plain are characteristically daytime thermally
driven up-valley (from the southwest) and nocturnal down-valley (from the
northeast) valley flows. Strong up-valley flow, assisted by west to east
pressure gradients, can persist for many hours after sunset.
Although winds are generally oriented along the Snake River Plain's
longitudinal axis, they are also influenced by up- and down-slope flows from
the adjacent sidewalls and outflow from canyons that enter the plain from
surrounding mountain ranges. Near CRMO1, such flow may originate in the
nearby central Idaho mountains immediately to the north, notably the Big
Lost River valley that enters the Plain near Arco about 25 km northeast as
well as smaller drainages immediately to the north.
A more detailed discussion of wind flow patterns in the eastern Snake River
Plain is given in Stewart et al, 2001.
Inversions/Trapping
The Snake River Plain is a regional topographic depression, lower than
surrounding mountainous terrain, and is subject to severe winter inversion
conditions that can persist for days or weeks at a time. During these
periods weather systems may move over the area without stirring the air
below resulting in buildup of aerosols and other pollutants. The condition
can persist until valley air is displaced by colder arctic air from the east
that may in turn stagnate repeating the cycle. In the summer regional
subsidence inversions during periods of high pressure and stagnation can
result in aerosol buildup over periods of days. Subsidence inversion heights
are typically at elevations of 2,000 to 3,000 m (6,000 to 10,000 ft). High
regional aerosol concentrations may occur during summertime stagnation and
subsidence inversion periods in conjunction with western wildland fires.
Climatological Statistics
Pocatello Idaho normals means and extremes are representative of eastern
Snake River Plains locations including Craters of the Moon Wilderness and
Monument. Other
Idaho Climate Summaries are available from the
Western Regional Climate Center.
Meteorological Indicators for Local Sources
Keywords
Reference
Stewart, J.Q., C.D. Whiteman, W.J. Steenburgh, and X. Bian. 2001. A
Climatological Study of Thermally Driven Wind Systems of the US
Intermountain West. NOAA/Cooperative Institute for Regional Prediction and
Department of Meteorology, University of Utah and Pacific Northwest National
Laboratory. Submitted to Bulletin of the American Meteorological Society,
August, 2001.
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