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Superstition Wilderness Area |
Site Name
IMPROVE:
TONT1 (Tonto National Monument)
Region
Southwest Deserts
Terrain
Terrain is shown in the 2 km terrain
map
and the 20 km terrain
map.
The Superstition Wilderness Area occupies 124,117 acres 30 to 40 km east of
Phoenix/Mesa in central Arizona. Elevations range from approximately 600 m
(2,000 ft) on the western boundary to 1,910 m (6,265 ft) on Mound Mountain.
In the western portion rolling land lies surrounded by steep to vertical
terrain. Terrain is less severe in the eastern portion that consists of
ridges and canyons radiating from Mound Mountain. Vegetation is primarily
Sonoran Desert type with semi-desert grassland and chaparral higher up.
The IMPROVE monitoring site representing the Superstition Wilderness Area is
TONT1, Tonto National Monument, at an elevation of 786 m (2,578 ft). It is
about 5 km north of the northwestern Wilderness boundary.
Representativeness
TONT1 should be representative of aerosol concentration and composition
within the Superstition Wilderness.
Nearby Meteorological Data Stations
Nearby meteorological monitoring network stations are shown in the data
network map
and at the RAWS station US
Climate Archive sites. There are no network meteorological data
monitoring sites within Wilderness boundaries. The
Roosevelt Arizona RAWS Site is located a few km north of the wilderness
near Roosevelt Arizona by Theodore Roosevelt Reservoir. Meteorological data
from this site includes wind data and should be representative of the
Wilderness Area. The
Superstition
COOP Site is located just outside the southwestern Wilderness boundary.
Regionally representative data is collected at National Weather Service
sites in the Phoenix/Mesa area. The nearest upper air site is Tucson.
Sounding data collected twice daily at Tucson should be representative of
regional upper air structure.
Wind Patterns
Wind patterns of the region are characterized by predominantly westerly
winds except during spring and summer.
Phoenix wind roses show the
prevailing westerly to southerly wind direction predominance on an annual
basis. A seasonal shift in wind from a westerly direction to a more
southerly direction, not clearly evident in the Phoenix wind roses that may
be steered locally, typically establishes itself in early July and persists
through mid-September and is associated with the
North American
Monsoon. The wind direction shift is more evident in wind data
from the
Roosevelt Arizona RAWS Site which shows the summertime shift to
southerly winds, especially southwesterly, although there may also be some
local effects here as well, due to some drainage flow from the mountains
directly south. During this Monsoon period, moisture bearing winds move into
the region from the southwest at the surface, from the Gulf of California,
and aloft from the southeast, from the Gulf of Mexico. Convective
instability associated with surface heating of the moist air, combined with
orographic uplift as air is transported towards higher terrain in the
direction of the Mogollon Rim, produces frequent convective precipitation
events often associated with intense rainfall, lightning, hail, and damaging
winds. Strongest thunderstorms are often found in the mountainous regions
such as the Superstition Wilderness. These thunderstorms are often
accompanied by strong winds and brief periods of blowing dust prior to the
onset of rain. South and southwesterly regional transport winds may also
carry emissions from nearby sources and source regions west of the
Wilderness, such as the nearby Phoenix/Mesa metropolitan area.
Potential local transport routes into Superstition Wilderness include
low-level mesoscale upslope flow from sources and source regions to the
west, directly through upwards mixing of urban emissions in the Phoenix area
to elevations of the western Wilderness, and perhaps along the Salt River
valley and mixed upwards to higher elevations of the eastern Wilderness.
Long distance transport into the Wilderness may occur via upward mixing from
more distant source regions in the southwest and transport into the
Wilderness via upper level flow, especially during the summer.
Inversions/Trapping
The southwestern U.S. region that includes the Superstition Wilderness is
subject to frequent stagnation events. In the central Arizona long-term data
indicate an average of at least one stagnation episode per month from May to
October, where an air stagnation episode is defined as stagnation conditions
that persist for 4 days or longer (Wang
and Angell, 1999). During this period, pressure and temperature
gradients in the region are weakest, and wind circulations weakest.
Subsidence inversions during these conditions may trap regional haze with
buildup over periods of several days.
Surface based radiation inversions in the Phoenix/Mesa valley can occur,
especially in the wintertime. Wilderness locations may be above this surface
inversion layer some of the time, but may be impacted if mixing caused by
surface heating lifts trapped pollutants to Wilderness elevations.
Climatological Statistics
Phoenix Normals
Means and Extremes are representative of regional climatology at lower
elevations. Data from the
Roosevelt
Arizona RAWS Site may provide additional meteorological data more
representative of eastern Wilderness locations.
Meteorological Indicators for Local Sources
Keywords
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Last updated 13 November 2004
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