Site Name

IMPROVE: NOCH1 (Northern Cheyenne-Tribal Site)

Region

Northern Great Plains

Terrain

The Northern Cheyenne Reservation Area is located in southeastern Montana. Terrain varies from low, grass- covered hills to high, steep outcroppings and narrow valleys. Elevations range from 1,000 to 1,500 m (3,000 to 5,000 ft).

The IMPROVE site representing the Northern Cheyenne Reservation Area, NOCH1, is located on rolling plains land 9 km east of Lame Deer, the nearest town. The site elevation is 1332 m (4370 ft). The surrounding terrain is low hills which can be taken as relatively flat on the scale of synoptic winds. 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 the Northern Cheyenne Reservation Area.

Nearby Data Stations

This map shows the location of the nearest air quality and meteorological monitoring sites, with respect to the Northern Cheyenne Reservation Area. Meteorology is not presently monitored at the site. Historical meteorological data from the Badger Peak Montana RAWS site located 4.5 km east of the IMPROVE site in similar terrain at an elevation of 1,323 m (4,340 ft) should be reasonably representative of meteorology of the Northern Cheyenne Reservation Area.

The nearest upper air site is the Glasgow Montana RAOB site, which conducts atmospheric soundings twice daily, located 284 km north of the NOCH1 IMPROVE site. Vertical atmospheric data from Glasgow should be the best available representation of vertical atmospheric structure at Northern Cheyenne Reservation Area.

Wind Patterns

The monitoring site is well exposed to prevailing synoptic wind patterns due to the relatively plain topography of the region. This monitoring region is affected by 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.

Long term (1961-2002) wind patterns can be seen in Billings, Montana wind roses.  Local wind directions are a consequence of this synoptic pattern and are predominantly south-westerly in the winter. During the rest of the year there is a higher frequency of south-westerly or north-easterly flow. Badger Peak wind roses from the Badger Peak Montana RAWS site show annual and seasonal wind direction distributions that should be representative of the Northern Cheyenne Reservation Area. These wind roses are based on data for the period January1, 1986 through March 30, 2004.

Inversions/Trapping

Because of the rolling flat terrain in the region, inversions in the Northern Cheyenne Reservation Area are probably 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 Badger Peak Montana RAWS site.

Meteorological Indicators


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