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Gila Wilderness Area |
Site Name
IMPROVE:
GICL1
Region
The Mexican Highlands
Terrain
Terrain is shown in the 2 km terrain
map
and the 20 km terrain
map.
The large (> 0.5 million acres) Gila Wilderness is part of the Mogollon
Mountain range of southwestern New Mexico, just west of the Continental
Divide. It includes most of the headwaters of the Gila River’s West, Middle,
and East Forks. Terrain is dominated by the Gila River drainage, which flows
southward through the middle of the Wilderness. Highest elevations are in
the western portion at the crest of the Mogollon range, with highest
elevation 3,322 m (10,895 ft) at Whitewater Baldy Peak. Lowest elevations,
1,800 to 1,900 m (5,900 to 6,200 ft), are near the Gila River. The Gila
River is not technically within the Wilderness although it is surrounded by
it. Very generally, terrain slopes downward from northeast to southwest and
the region is sometimes included as part of the Mexican Highlands physiographic
region, sometimes as part of the Southern Rocky Mountain.
The IMPROVE monitoring site representing the Gila Wilderness is GICL1,
located on a bank just overlooking the Gila River in the east central part
of the Wilderness, elevation 1,776 m (5,825 ft).
Representativeness
The location of the Gila Wilderness IMPROVE site, GICL1, near the center of
the Wilderness should make it representative of Wilderness locations when
the atmosphere is well mixed. Its elevation is at the lower end of
Wilderness elevations so that there may be times when it is isolated within
shallow surface-based inversions that do not extend vertically to higher
Wilderness elevations.
Nearby Population/Industrial Centers and Local Sources
Nearby Meteorological Data Stations
Nearby meteorological monitoring network stations are shown in the data
network map. Locations and data from nearby RAWS monitoring sites can also be
accessed at the
RAWS station US Climate Archive website. The
Gila Center RAWS site, elevation 1,707 m, is at the same general
location as the GICL1 IMPROVE site and should be representative of lower
elevation Wilderness locations. Wind data may be influenced by the Gila
River drainage. The
McKenna RAWS site, elevation 2.622 m, is at a higher location in the
center of the Wilderness and may be more representative of exposed
Wilderness locations generally. This station was active from September, 1993
through September, 1998.
The Bear Wallow RAWS site, elevation 3,034 m, is located just outside
the northern Wilderness boundary and may be representative of high
Wilderness elevations near the crest of the Mogollon range.
The Gila Wilderness is approximately equidistant from three upper air RAOB
sites in the region, where atmospheric soundings are conducted twice daily:
Albuquerque, Santa Teresa New Mexico, and Tucson Arizona. The Albuquerque
site is ~ 230 km northeast, Santa Teresa site is ~ 200 km southeast, and
Tucson is ~ 250 km southwest.
Wind Patterns
Albuquerque wind roses show regional wind patterns. Most of the year but
especially in winter there is a strong northerly component that varies
according to the position of the jet stream. During summer the jet stream
migrates further north than usual, so that synoptic westerly winds aloft are
weaker and more southerly winds dominate, coinciding with the
North American Monsoon. During this 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 Mexican Highlands, produces frequent convective
precipitation events often associated with intense rainfall, lightning,
hail, and damaging winds. Southerly winds can also transport airborne
particulate material into the Wilderness from sources source regions to the
south and southeast, including Mexican sources
Locally, in the absence of strong regional pressure gradients, flows will be
dominated by upslope/downslope winds typical of mountainous areas. Daytime
upslope winds will be from the lower terrain to the south generally, and up
the Gila River drainage. Nighttime drainage flow will be down slope towards
the lower terrain to the south and down the Gila River drainage. This
diurnal upslope/downslope pattern is evident in wind roses from the
Gila Center RAWS site.
Potential local transport routes into the Gila Wilderness include upslope
flow, from the south, within the Gila River drainage, and long distance
transport via upward mixing from more distant source regions to the south
and southwest. Possible source regions include Mexico and Gulf Coast areas.
Inversions/Trapping
Wang
and Angell, 1999 describe two regions of the U.S. with high frequencies
of regional stagnation events, in the southwest and south-central U.S. The
Gila Wilderness is midway between these two regions and typically has 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. 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. Locally, diurnal surface based temperature inversions may occur
especially in the winter at lower elevations within the Wilderness and near
the Gila River valley.
Climatological Statistics
Albuquerque Normals, Means, and Extremes are representative of regional
climatology at lower elevations. More representative local data can be
accessed at the
Gila Center RAWS site or the
McKenna RAWS site. See Nearby Meteorological Data Stations discussion,
above.
Meteorological Indicators for Local Sources |
updated 15 November 2004 |