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Canyonlands National Park |
Site Name
IMPROVE: CANY1
CASTNET: CAN407
Region
Colorado Plateau
Terrain
Terrain is shown in the 2 km terrain
map and the 20 km terrain
map.
Canyonlands National Park
is located in southeastern Utah. It consists of canyon lands in a large
region surrounding the confluence of the Green and Colorado Rivers. Terrain
is steep canyons, mesas, and plateaus, with elevations ranging from 1,128 m
(3,728 ft) on the Colorado River in Cataract Canyon to 2,170 m (7,120 ft) at
Cathedral Point. Highest rim locations are generally 1,800 to 2,000 m (5,900 to
6,560 ft). From rim locations, terrain descends vertically more fanned out
plateau elevations at ~ 1,500 m (~5,000 ft), and then in another more vertical
descent to river elevations.
The IMPROVE site, CANY1, is located on a high canyon rim point at the north
end of the NP. The CASTNET site, where meteorological data has been
collected since 1995, is at the same location.
Representativeness
Aerosol data collected at CANY1 should be representative of visibility
conditions at the Grand Canyon rim, including vistas overlooking the park.
It should represent conditions at lower canyon elevations when the
atmosphere is uniformly mixed. It may not represent aerosol concentrations
at lower canyon elevations when lower canyon elevations are within a stable
(inversion) layer with height below the monitoring site at the canyon rim.
Nearby Data Stations
Meteorology has been monitored at the
CASTNET Canyonlands NP site, CAN407, since 1995. Measurements
include wind speed, wind direction, stability, temperature, and relative
humidity. Other nearby monitoring network stations are shown in the data
network map and at the
US Climate Archive and
RAWS station US Climate Archive
sites. The nearest upper site with measurements representative of upper air
structure at Canyonlands NP is Grand Junction, Colorado.
Wind Patterns
Rim Locations:
Representative wind roses are based on surface meteorological data collected
at the CASTNET CAN407 site for the period 1995 – 2001 and indicate annual
and seasonal wind direction (direction from which the wind is blowing)
frequencies. Since both CAN407 and CANY1 are located at the same rim
location in the north part of the Park, these annual and seasonal wind roses
should be representative of wind conditions at canyon rim locations. Wind
roses show predominantly east-southeasterly flow, especially summer, with
higher frequencies of west-northwesterly flow in the other seasons,
especially winter. Nighttime (0100 – 0600) and daytime (1300-1700) annual
wind roses show a diurnal pattern. Daytime directions are mostly westerly
(northwest to south-southwest).
Lower Canyon Elevations:
Wind directions and resulting transport flow at lower canyon elevations
should be significantly different from those for rim locations. Directions
will be steered more in line with canyon orientation, and in side canyons
should have a well-defined diurnal drainage/upslope pattern. Interior
locations should thus be more susceptible to aerosol transport via canyon
winds. Average canyon flow near river levels should be predominantly
downriver during the winter and upriver during the summer, in line with
average synoptic scale pressure gradients.
Potential transport routes into Canyonlands NP include low-level transport
into the area via the Green and Colorado River (upstream) drainages, and the
Colorado River (downstream) drainage, with upward convective and upslope
mixing to rim locations, and upper air transport via upward mixing in
distant source regions and advection aloft into Park areas.
Inversions/Trapping
At lower canyon elevations within the canyon there is a potential for
trapping inversions, although there is downstream egress. Such cases could
result in significantly larger aerosol concentrations at interior locations
than at CANY1. These situations are most likely to occur in the fall and
winter, when surface cooling at the canyon bottom is greatest.
At canyon rim locations, inversions will not be trapping inversions of the
sort that occur in deep valleys and canyons, but subsidence inversions that
become established as air subsides over a surface high pressures area and
are associated with buildup and stagnation of synoptic high pressure ridges.
These 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. During these conditions aerosol concentration
and composition may be more uniform within the park.
Climatological Statistics
Canyonlands climate (temperature, precipitation) is typified by data from
the NWS COOP station at
The Needle.
Climate statistics can also be retrieved from
CASTNET data for Canyonlands,
station CAN407, from which the previously mentioned wind roses were derived.
Regional normals means and extremes are compiled for the
Grand Junction
NWS station.
Meteorological Indicators for Local Sources
Keywords
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