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Gates of the Mountains Wilderness Area |
Site Name
IMPROVE: GAMO1
Region
Central Rockies
Terrain
Terrain is shown in the 2 km terrain
map
and the 20 km terrain map.
The 28,562-acre Gates of the Mountains Wilderness is located in west central
Montana at the north end of the Big Belt Range. It is on the east side of
the Missouri River valley 30 km (20 mi) north of Helena and 80 km (50 mi)
southwest of Great Falls. Terrain includes limestone cliffs, deep canyons,
and craggy peaks. Elevations range from about 1,150 (3,770 ft) at the lowest
valley location near the Missouri River on the west side, to ~ 2,200 m
(7,216 ft) at summit locations.
The IMPROVE site representing Gates of the Mountains Wilderness is GAMO1,
located near the top of Hogback Mountain 4 km southeast of the Wilderness
boundary. The site elevation is 2,392 m (7,846 ft).
Representativeness
The GAMO1 IMPROVE site has an unobstructed vista into the Wilderness Area to
the northwest and is at an elevation above the highest Wilderness elevation.
It is thus very representative of visibility in the Gates of the Mountains
Wilderness Area. Its elevation is near the 760 mb standard pressure height
and it should thus also be very representative of regional aerosol
characteristics at this transport level.
Nearby Population/Industrial Centers and Local Sources
Local sources include the city of Helena, 36 km (22 mi) southwest of GAMO1
in the Missouri River valley, and some 1,150 m (3,772 ft) lower in
elevation. Great Falls is 80 km (50 mi) north. Missoula is 170 km (105 mi)
west. The site may be impacted by emissions from point sources along this
section of the Missouri River, lofted or dispersed and mixed upward to the
monitoring site elevation. Highest concentrations from local or regional
sources may occur during regional wildfire events.
Nearby Meteorological Network Monitoring Stations
Nearby meteorological 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 nearby meteorological network monitoring
sites at elevations close to the GAMO1 site elevation. The
Helena Montana
RAWS site and the Helena WSO are at valley locations over 1,000 m (3,000
ft) lower than GAMO1. Historical data from the Helena WSO, and from the
Missoula NWS station, are available via the
EPA Technology Transfer
Network website.
The closest upper air site is Great Falls Montana (TFX), 80 km (50 mi) north
of GAMO1. Data for this and other upper air sites are accessible via the
University of Wyoming Dept
of Atmospheric Science web page.
Wind and Transport Patterns
Regionally, wind patterns and transport flows are dominated by westerly
synoptic flows, with frequent easterly flows in the winter. Monthly
Missoula Montana
wind roses indicate this pattern, with northwesterly flow predominant at
this surface station and a significant east-southeasterly component in the
winter. Note that these surface wind patterns may differ somewhat from upper
level winds because of terrain effects. Because of its high elevation
relative to surrounding terrain, data from the GAMO1 may see the effect of
pollutant transport near the 760 mb level most of the time. It could also be
impacted by emissions from sources in the nearby Missouri River valley
lofted or mixed upward during afternoon mixing in warm months.
Inversions/Trapping
The GAMO1 IMPROVE site will be well above typical wintertime surface
inversions in surrounding canyons and valleys, and nocturnal inversions in
the Missouri River valley although valley emissions may be mixed upwards
towards the monitoring site elevation in the afternoon. The site may see
aerosol accumulation during summertime regional stagnation and subsidence
inversion episodes, especially in conjunction with regional wildfire events.
Climatological Statistics
Helena Montana
Normals Means and Extremes should be representative of lower elevations
near the Missouri River in this part of Montana. Other
Montana Climate
Summaries are available from the
Western Regional Climate Center.
Meteorological Indicators for Local Sources
Keywords
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