Site Name
Nearest IMPROVE site is the White River National Forest
site, WHRI1, near Aspen.
Region
Southern Rocky
Mountains
Terrain
Terrain is shown in the 2 km
terrain
map
and the 20 km terrain
map.
West Elk Wilderness is located in west-central
Colorado. Terrain is high peaks and basins. Elevations vary from ~2,300 m
(7,500 ft) to the highest peak elevation of 3,974 m (13,035 ft). A high
glacial basin surrounded by peaks drains to the south via the Blue Mesa
Reservoir to the Gunnison River and to the north via Coal Creek to the North
Fork of Gunnison River, thence to the Colorado River near Grand Junction.
There is no IMPROVE site in the immediate vicinity of West Elk Wilderness.
The nearest IMPROVE site is the White River National Forest site, WHRI1,
located near Aspen at an elevation of 3,418 m (11,211 ft) and ~50 km (30 mi)
northeast of the Wilderness.
Data Representativeness
The White River National Forest site, WHRI1, is at a
high elevation and should be representative of aerosol composition and
concentration at similar elevations in West Elk Wilderness Area. At this
high elevation it may be above regional haze. It will probably not be
representative of lower elevations in the West Elk Wilderness, which may
frequently be isolated within lower level terrain-induced radiation
inversions.
Nearby
Population/Industrial Centers and Local Sources
Nearby Data Stations
Nearby monitoring network
stations are shown in the data network
map
and at the
US Climate Archive
and
RAWS station US Climate Archive sites. There are no network
data stations within the Wilderness Area boundary. For surface
meteorological data, the
Gothic CASTNET site,
at an elevation of 2,926 m (9,597 ft) and about 40 km northeast of the
Wilderness Area and in similar terrain, should be reasonably representative
of similar elevations in the West Elk Wilderness Area except for wind data
which may be channeled or steered locally. The Black Canyon RAWS site,
elevation 2,610 m (8,560 ft) and 40 km (25 mi) southwest of the Wilderness
area may also provide data reasonably representative of West Elk Wilderness
Area, except for wind data. Upper air structure is best represented by upper
air data from the Grand Junction NWS site, 120 km west-northwest of the
Wilderness Area.
Wind Patterns
Grand Junction long-term
wind roses show predominantly southeasterly flow, with additional
northwesterly flow during winter. These wind roses may be influenced by
terrain channeling by the Colorado River valley near Grand Junction, but
should be indicative of transport flow into the West Elk Wilderness Area at
high altitudes. At lower elevations within the Wilderness Area wind
patterns during light regional wind and stagnation periods will show a
pronounced diurnal pattern consistent with mountain/valley upslope/downslope
flow.
Transport pathways into the West Elk Wilderness Area
are primarily via upper level transport from distant source regions,
consistent with regional haze. Locally, transport from local sources such
as wildland fires will be upslope/downslope within the drainage channels
exiting north and south from the Wilderness Area. There is probably not the
same potential for lower level transport from distant sources as there is in
areas connected to major river corridors such as the Colorado River.
Inversions/Trapping
The deep canyons and basins of the Wilderness Area
are subject to frequent diurnal radiation temperature inversions that could
trap aerosols locally, especially during wildland fire episodes. Regional
stagnation and subsidence inversions could occur, especially during summer
months. From May to October, long term records show an average of nearly
one air stagnation event per month during this period in western Colorado,
where a stagnation event is defined as stagnation conditions that persist
for 4 days or longer (Wang
and Angell, 1999).
Higher elevations will typically be above trapped
local haze and may also be above regional haze trapped below large-scale
subsidence inversions.
Climatological Statistics
Regional normals means and extremes are compiled for
the
Grand Junction
NWS station. Climate data representative of West Elk
Wilderness Area is also collected at the Gothic CASTNET site and Black
Canyon RAWS site described in the Nearby Data Stations section.
Meteorological
Indicators for Local Sources