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Gearhart Wilderness Area |
(Also see Crater Lake National Park)
Site Name
IMPROVE:
CRLA1 (Crater Lake National Park)
Region
Cascade Range
Gearhart Mountain Wilderness is represented by the Crater Lake National Park
IMPROVE site, CRLA1, and is thus included as part of the same physiographic
region, the Cascade Range. The Wilderness itself is in the high desert of
central and eastern Oregon east of the Cascade Range and could marginally be
included in the Columbia Plateau region.
Terrain
Terrain is shown in the 2 km terrain
map and the 20 km terrain
map.
The Gearhart Mountain Wilderness comprises 22,809 acres on the flanks of
Gearhart Mountain in south central Oregon, primarily the northern slope and
eastern drainages of Gearhart Mountain, the dominant topographic feature.
Elevations range from near 1,800 m (5,900 ft) at the North Fork of the
Sprague River in the northern Wilderness to 2,550 m (8,364 ft) at the summit
of Gearhart Mountain.
The IMPROVE site representing Gearhart Mountain Wilderness is CLRA1, The
Crater Lake National Park IMPROVE site. CLRA1 is located just outside of the
crater rim in Crater Lake National Park. It is 110 km (~70 mi)
west-northwest of Gearhart Mountain Wilderness near the crest of the Cascade
Range.
Representativeness
The CLRA1 IMPROVE site should be representative of regional aerosol
characteristics, including Gearhart Mountain Wilderness, during periods of
uniform regional haze.
Nearby Population/Industrial Centers and Local Sources (with respect to
CRLA1 IMPROVE site)
There are no major source regions close to CLRA1. The lower Willamette
Valley of western Oregon, from Portland to Eugene, is over 100 miles distant
on the opposite side of the Cascade crest. Central California valleys are
more distant, to the south. Nearest communities are Medford and Grants Pass,
in the Rogue River valley, where the major industry is timber.
Nearby Meteorological Data Stations
Nearby meteorological monitoring network stations, with respect to CRLA1,
are shown in the data network map and at the
RAWS station US Climate Archive site. The nearest site with
representative hourly data that includes wind data is the
Mount Stella
Oregon RAWS site,
located 12 km west of the Crater Lake National Park boundary at an exposed
elevation of 1,438 m (4,715 ft).
Medford WSO AP
data is representative of regional climate at lower elevations. Upper air
data is also collected at the Medford RAOB station.
Wind and Transport Patterns
Synoptic winds in the region are generally northwesterly (from the
northwest), with an additional component of more southerly winds in the
winter with the weakening of the Pacific High Pressure System. This pattern
is indicated in monthly Medford Oregon Wind Roses from Medford, in the Rogue River valley 50 miles
southwest of CRLA1 at an elevation 1,330 m (4,362 ft), although there may be
some modification of surface wind directions due to local terrain effects.
There may be some upvalley transport flow towards CRLA1 via the upper Rogue
River valley, although the site itself is some 600 m (2000 ft) higher in
elevation than the Rogue River valley floor near Medford and Grants Pass.
With respect to Gearhart Mountain Wilderness, wind directions at well
exposed surface locations in eastern Oregon may be better represented by
Redmond Oregon Wind Roses which
show a higher frequency of wintertime southerly flow than occurs at Medford.
Potential local transport routes to the CRLA1 IMPROVE site include emissions
in the Rogue River valley transported directly via diurnal upslope/downslope
flow, mixed upwards with afternoon mixing, or trapped regionally under a
persistent subsidence inversion. Highest summertime measured concentrations
at CRLA1 are likely associated with regional forest fire events or transport
from distant source regions.
Inversions/Trapping
The inner crater at Crater Lake National Park is susceptible to surface
based trapping inversions, especially in the winter, although pollutant
buildup within the rim would not affect aerosol measurements at CRLA1, which
is outside and downslope from the rim. In the summer, the Rogue River valley
nighttime boundary layer could be mixed upwards to the CRLA1 elevation. On a
synoptic scale, persistent summer subsidence inversions caused by stagnant
high pressure over the region can result in aerosol buildup over periods of
days. Subsidence inversion heights with typical elevations of 2,000 to 3,000
m (6,000 to 10,000 ft) could hold aerosol accumulations at the CRLA1 site.
Highest concentrations likely result when this warming and drying condition
leads to major forest fires in Southern Oregon and northern California.
Climatological Statistics
Crater Lake Climate data
from Crater Lake National Park Headquarters gives long-term climate
statistics for Crater Lake in the vicinity of CRLA1, excluding wind
statistics. Medford Oregon Normals Means and Extremes
are representative of lower elevations in the Rogue River valley. Eastern
Oregon locations near Gearhart Mountain Wilderness may be better represented
by Lakeview Oregon Climate Data. Lakeview is 50 km (30 mi) southeast of the Wilderness. Other
Oregon Climate
Summaries and Northern
California Climate Summaries are available from the
Western Regional Climate Center.
Keywords
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Last updated 9 December 2004
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