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Medicine Lake Wilderness Area |
Site Name
IMPROVE: MELA1 (Medicine Lake)
Region
Northern Great Plains
Weather in this area is typically unpredictable, with un-seasonal cold (or
warm) conditions possible at any time of the year.
Terrain
The Medicine Lake Wilderness Area IMPROVE site is located on flat land ~2000
ft North of Medicine Lake shore. Site elevation is ~ 605 m (1985 ft) msl,
which is 40 to 50 ft above the lake level (~1942 ft). Lowest elevations in
the area are nearby lakes, with no mountains or hills nearby. The site thus
has good exposure to regional scale transport winds. Surrounding terrain is
predominantly agricultural dry land 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 very representative of
visibility conditions within and surrounding Medicine Lake Wilderness Area.
Nearby Population/Industrial Centers
Population is sparse in the vicinity of the monitoring site. There are many
towns within the 20 miles of radius but the population is very less. The
nearest town is Medicine Lake with population 368 (2000 census) 1.5 mi west
from the monitoring site. The nearby towns are Plentywood (17 miles north),
Williston (46 miles southeast), Sydney (60 miles south), Wolfpoint (61 miles
southwest), and Glasgow (100 miles west). Major populated cities are Billing
(260 miles southwest, population was 89847 (2000 census)), Bismarck (210
miles southeast, population was 55532 (2000 census)) and Canadian city
Regina with population of 242827 is 135 miles north of monitoring site.
There are no major particulate sources nearby. The area is largely moderate
prairies, and there may be frequent emissions from prescribed burns or from
wild land fire during hot and dry periods
Nearby Data Stations
This map shows the location of the nearest air quality and meteorological
monitoring sites, with respect to the Medicine Lake Wilderness Area monitor.
Meteorology is not presently monitored at the site. The nearest CASTNET site
Theodore Roosevelt NP is located 120 mi south-east from the Medicine Lake
Wilderness site with meteorological monitoring. Historical meteorological
data from the Theodore Roosevelt National Park site probably provides good
representation of meteorological patterns at Medicine Lake Wilderness Area.
The nearest upper air site is Glasgow RAOB site, which conducts atmospheric
soundings twice daily, located 100 miles west of the monitoring station.
Other nearby upper air radiosonde launching sites are Bismarck and Rapid
City (310 miles) south. Vertical atmospheric data from Glasgow should be the
best available representation of vertical atmospheric structure at Medicine
Lake Wilderness Area.
Wind Patterns
The monitoring site is well exposed to prevailing synoptic wind patterns due
to plain topography of the region. 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. Long
term (1961-2002) wind patterns can be obtained from
Glasgow wind roses.
Wind directions in the area are a consequence of this synoptic pattern and
are predominantly southeasterly and northwesterly flow in the winter. During
the rest of the year there is a higher frequency of northwesterly to
southwesterly flow. The following wind roses shown for Medicine Lake Area (RAWS
site) for annual,
winter,
spring,
summer, and
fall with stronger northerly
to northwesterly flow in the winter. Note that this data is from Feb 1,
2003.
Diurnal variations in wind directions depend on terrain and water features
that establish diurnally varying gradients of temperature and pressure.
Nearby lakes in the region might presumably result in land/lake breeze
conditions on a very small and local scale. If such conditions exist, they
would probably be very local and occur during light wind or regional high
pressure and stagnation situations. Such local conditions would not have
great significance with respect to transport of particulate matter from
distant sources and source regions.
Inversions/Trapping
Because of the flat terrain in the region, inversions in the Medicine Lake
Wilderness Area probably are not trapping inversions, but rather subsidence
inversions associated with buildup and stagnation of synoptic high pressure
ridges. They thus 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
The EPA CASTNET website
has good climatology data for the region based on 5 years (1998 – 2002) of
monitoring at the Theodore Roosevelt CASTNET site. Climatological data for
Roosevelt National Park area should be very similar to Medicine Lake
Wilderness as the two sites are located in similar terrain and land cover
and are separated by ~100 miles. Winter conditions generally run from early
November through March. Temperatures can range from 50 degrees above zero to
50 below zero.
Meteorological Indicators
Keywords
Alberta Clipper
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