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Eagle
Cap Wilderness Area |
Also, see Strawberry Mountain Wilderness
Site Name
IMPROVE:
STAR1 (Starkey Oregon)
Region
Columbia Plateau
Terrain
Terrain is shown in the
2 km terrain map and the
20 km terrain map.
The Eagle Cap Wilderness Area comprises 358,461 acres in northeastern
Oregon. Terrain is characterized by bare peaks and ridges and U-shaped
glaciated valleys. Elevations range from 1,500 m (5,000 ft) in lower valleys
to near 3,050 m (10,000 ft) at the highest mountain summits. The Lostine and
Minam Rivers flow north from the center of the Wilderness towards Pendleton
and the Columbia, 130 km northwest.
The IMPROVE site representing Eagle Cap and Strawberry Mountain Wilderness
Areas is STAR1 (Starkey, Oregon). It is 65 km west of the Eagle Cap
Wilderness boundary, on a northeast facing slope at an elevation of 1,258 m
(4,126 ft), ~ 150 m (500 ft) higher than lower valley bottom locations to
the northeast. Higher peaks to the southwest have elevations near 1,430 m
(4,700 ft).
Representativeness
STAR1 is distant from the Wilderness Areas but should be representative of
regional aerosol concentrations and characteristics. It may not be as
representative of smaller scale features such as valley trapping inversions
at lower Wilderness elevations, especially in the Eagle Cap Wilderness.
Nearby Population/Industrial Centers
STAR1 and Eagle Cap and Strawberry Mountain Wilderness Areas are in eastern
Oregon, distant from most urban centers. Upwind source areas include
Portland and the Willamette Valley, west of the Cascade Range and 350 km
(220 mi) to the west. The nearest significant population center is Boise and
the Treasure Valley of southwestern Idaho, 240 km (150 mi) southeast. High
aerosol concentrations at STAR1 during the extended summer may result from
regional forest fires.
Nearby Meteorological Network Monitoring Sites
Nearby meteorological monitoring network stations with respect to the STAR1
IMPROVE site are shown in the data network
map and at the RAWS station
US Climate Archive site. Eighteen years of hourly data are available
from the J Ridge
Oregon RAWS site 15 km southeast of STAR1 in a well exposed location and
similar elevation of 1,579 m (5,180 ft). Meteorological data from this site
should be representative of concurrent meteorology at STAR1.
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 and Transport Potential
Synoptic winds in the region are generally westerly in the spring and summer
when the Pacific High is off the coast of northwestern U.S., potentially
contributing to transport from source regions to the west, including
Portland and the Willamette Valley as well as more distant source regions.
This flow is often assisted by the development of a typical summertime heat
low over the Columbia Plateau that can bring marine air, and higher
humidity, into the region via the Columbia Gorge. In the winter with the
weakening and southward retreat of the Pacific High, interior high pressure
over the Great Basin and Idaho and lower pressure west of the Cascades can
result in easterly gradient (synoptic) flow, with potential for transport
from sources to the east, including Boise and the Treasure Valley
agricultural region. These synoptic patterns are indicated in monthly
Pendleton Oregon wind roses
and Boise Idaho wind roses.
Note that these surface wind patterns may differ somewhat from upper level
winds because of terrain effects.
Inversions/Trapping
Locally, The STAR1 site is some 150 m (500 ft) above valley bottom terrain
to the northeast and could at times be within local wintertime surface
inversions that extend to this height, potentially isolating the site from
regional overlying air. Otherwise the site is representative of aerosol
characteristics at lower levels within the surface mixed layer over the
region. Mixing heights calculated for Spokane (Ferguson
and Rorig, 2003), representative of Columbia Plateau locations, show
winter heights generally below 300 m (1,000 ft). Spring and summer Spokane
mixing heights frequently reach to 1,500 m (4,920 ft). Calculated Fall
Spokane mixing heights were typically near 900 m. Higher level summertime
subsidence inversions associated with the establishment of the
semi-permanent Pacific high-pressure system could result in regional 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). Highest regional
aerosol concentrations may occur during summertime stagnation and subsidence
inversion periods in conjunction with western wildland fires.
Climatological Statistics
Spokane
Washington Normals Means and Extremes are representative of low
elevation locations in the central Columbia Plateau. Other
Washington Climate
Summaries and
Oregon Climate Summaries are available from the
Western Regional Climate Center.
Meteorological Indicators
Keywords (to be completed)
References
Ferguson, Sue and Miriam L. Rorig. Regional Pollution Potential in the
Northwestern United States. USDA Forest Service General Technical Report
PNW-GTR-590, October, 2003.
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Last updated 9 December 2004
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