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UL
Bend Wilderness Area |
Site Name
IMPROVE: ULBE1 (UL Bend)
Region
Northern Great Plains
Terrain
The U. L. Bend Wilderness Area IMPROVE site is located on rolling plain land
6 km south of Missouri River and 38 km northwest from Fergus, the nearest
town. Site elevation is 893 m (2930 ft). The surrounding terrain is
relatively flat. The site thus has good exposure to regional scale transport
winds. Surrounding ground cover is predominantly forest and moderate
grassland. Terrain in the area is depicted in detailed 20 km terrain
map and
2 km terrain map.
Representativeness
Aerosol data collected at the IMPROVE site should be representative of
visibility conditions within and surrounding UL Bend Wilderness Area.
Nearby Data Stations
This map shows the location of the nearest air quality and meteorological
monitoring sites, with respect to the UL Bend Wilderness Area. Meteorology
is not presently monitored at the site. Historical meteorological data from
the Armells
Montana RAWS site located nearby should be reasonably representative of
meteorology of the U. L. Bend Wilderness Area.
The nearest upper air site is Glasgow RAOB site, which conducts atmospheric
soundings twice daily, located 170 km northwest of the monitoring station.
Vertical atmospheric data from Glasgow should be the best available
representation of vertical atmospheric structure at U. L. Bend Wilderness
Area.
Wind Patterns
The monitoring site is well exposed to prevailing synoptic wind patterns due
to relatively plain topography of the region. This monitoring region is
affected from continental cold air mass from north and northwest during the
winter. Therefore, winter is characterized by frequent outbreaks of cold
continental air from the Canadian interior. A severe type of snowstorm that
frequently occurs during this synoptic condition is referred to as the
Alberta
Clipper. During the rest of the year the migration of the jet stream to
more northerly latitudes results in more frequent transport of warmer moist
air from the Gulf of Mexico and warm dry air from the southwestern U.S.
Glasgow wind roses illustrate the regional wind
patterns. Wind directions in the area are a consequence of this synoptic
pattern and are predominantly westerly flow in the winter. During the rest
of the year there is a higher frequency of westerly to easterly flow. The
following wind rose shown is from
Armells RAWS
site near to U. L. Bend Wilderness Area for
annual,
winter,
spring,
summer and
fall with
stronger westerly to easterly flow and less in other direction. Note that
this data is from October 1, 1991 to March 30, 2004.
Inversions/Trapping
Because of the rolling flat terrain in the region, inversions in the U. L.
Bend Wilderness Area probably are not surface based radiation trapping
inversions, but rather subsidence inversions associated with buildup and
stagnation of synoptic high pressure ridges. They tend to cover a large area
and are regional in nature. They may persist for periods of days until
ventilation occurs in conjunction with frontal passages or onset of stormy
low pressure systems.
Climatological Statistics
Billings,
Montana climate data is long term data that is representative of
regional climate characteristics. More local climate data can also be
accessed at the
Armells, Montana RAWS site. The
climate
summary of Glasgow also can be found at.
Meteorological Indicators
Keywords
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