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Capitol Reef National Park |
Site Name
IMPROVE: CAPL1
Region
Colorado Plateau
Terrain
Terrain is shown in the 2 km CAPL1 terrain
map and the 20 km CAPL1 terrain
map.
Capitol Reef National Park is located in south-central Utah and comprises
the Waterpocket Fold, a 100-mile long north-south wrinkle in the earth's
crust known as a monocline, shown in this south-looking aerial photo at the
Capitol Reef National Park website.
It is located at the eastern edge of high plateaus (Awapa Plateau, Aquarius
Plateau, elevations ~ 2,400 – 2,700 m (8,000 –9,000 ft)), where terrain at
plateau elevations begins to drop towards the Blue Hills and San Rafael
Desert (elevations ~ 1,500 – 1,800m (5,000 – 6,000 ft)) and ultimately to the
Colorado River at Cataract Canyon and Glen Canyon (Lake Powell, elevation
1,130m (3,706 ft)) 80 – 100 km (50 – 60 mi) southeast of the Park. The
north-south fold, with elevations in the 1,700 – 2,000 m (5,600 – 6,600 ft) is
traversed by several east-west canyons, most notably the Fremont River
canyon, that provide flow routes for plateau air drainage into the lower
elevation terrain to the east. Terrain orientation with respect to
large-scale features (plateau areas, Colorado River valley) has the same
general characteristics as Bryce Canyon National Park, and the two areas
should have similar meteorological factors contributing to haze.
There is a relatively slight general dip in terrain elevation just to the
west of the fold, between the fold and the higher plateau elevations. The
CAPL1 monitoring site is located in this small dip at an elevation of 1,890 m
(6,199 ft).
Representativeness
The CAPL1 site is located to the west of the fold, near or within the Sulfur
Creek and Fremont River drainage that leads to a natural wind corridor
through the Fold, and may be thus be more influenced by regional air and
channeled wind flow from the plateau interior than locations at the crest of
the fold. Nevertheless, aerosol data collected at the CAPL1 monitoring site
should be reasonably representative of aerosol concentration and composition
in Capitol Reef National Park.
Nearby Data Stations
Nearest monitoring network stations are shown in the data network
map and at the US
Climate Archive and RAWS
station US Climate Archive sites. Temperature and pecipitation data are
monitored at NWS Coop sites, data from which are accessible at the
Western Historical Climate
Summaries website. These include the
Capitol Reef NP
Coop monitoring station.
Upper air sites with data representative of upper air structure at Capitol
Reef NP are RAOB sites at Flagstaff, Arizona and Grand Junction, Colorado,
although low level surface wind directions at Grand Junction may be
channeled locally by the Colorado River valley.
Wind Patterns
There are no long-term wind speed and direction data sites in the immediate
vicinity of Capitol Reef NP. Wind roses are accessible for RAWS sites, the
nearest and most representative of which are probably
Escalante
and Flattop
Mountain.
Long-term wind roses from the
Flagstaff NWS site for
January,
April,
July, and
October, should be regionally representative of exposed areas such as
the crest of the Capitol Reef Fold. Flagstaff wind roses show a predominance
of south to south-westerly wind directions, especially in the summer, with a
significant frequency of more northerly wind directions during the fall and
winter. Exposed areas of Capitol Reef NP may show a more easterly component,
suggested by wind roses from
Escalante
and Flattop
Mountain.
At lower elevations on the east edge of the Park, an upslope/downslope
diurnal pattern may exist during light wind conditions, bringing lower
elevation Colorado River air into the park during the daytime, which may
have implications when combined with regional transport flow within the
Colorado River valley. At night, interior plateau air would tend to drain
through passes through the Fold in the direction of the Colorado River, in
particular through the Fremont River canyon where channeling and compression
may cause very strong winds, especially during periods of strong west to
east surface pressure gradients.
Potential transport routes into Capitol Reef NP include low level transport
into the area via Colorado River drainage and upper air transport via upward
mixing in source regions and advection aloft.
Inversions/Trapping
Capitol Reef NP is essentially part of the upper slopes on the west side of
the Colorado River valley, hence above any trapping surface-based inversions
with bases at lower Colorado River valley elevations. Park elevations on the
east side of the fold extend down to near 1,550 m (5,084 ft), which is still
400 to 500 m (1,300 to 1,600 ft) above the valley bottom at the Colorado
River.
Aerosol buildup may occur during large-scale subsidence inversions
associated with a surface high pressure that persists over periods of a few
days or longer, although Park elevations may still be above a subsidence
inversion that descends to a surface-based inversion. Such stagnation events
are most likely to occur during the extended summer (May - October), when
pressure and temperature gradients in the region are weakest, and wind
circulations therefore weaker. Long-term data have shown the southwestern
United States to be a region prone to regional stagnation episodes (Wang
and Angell, 1999).
Climatological Statistics
Climate data summaries for Park locations (temperature, precipitation,
snowfall) are available from the
Capitol Reef NP
Coop site. Long-term data including humidity data are collected at the
Escalante
site, which is at an elevation (2,440 m, 8,000 ft) typical of Park elevations,
located about 70 km (44 mi) south of CAPL1.
Meteorological Indicators for Local Sources
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