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Rawah Wilderness Area
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Site Name
IMPROVE: MOZI1 (Mount Zirkel), ROMO1 (Rocky Mountain National Park)
CASTNET: ROM406
Region
Southern Rockies
Terrain
Terrain is shown in the 2 km terrain
map and the 20 km terrain
map.
The Rawah Wilderness Area is in north central Colorado at the northern
terminus of the Front Range, on the eastern slopes of the Continental
Divide. Terrain is steep mountains and valleys, with elevations ranging from
2,550 m ( 8,400 ft) to 3,948 m (12,951 ft). Being primarily on the east slope of
the Divide it is in the rain shadow of the Rockies. West to east sloping
parallel drainages empty into the north-flowing headwaters of the Laramie
River.
Nearest IMPROVE sites are at Mt. Zirkel (MOZI1) and Rocky Mountain National
Park (ROMO1). ROMO1 is south of the Rawah Wilderness and generally within
the influence of the Front Range. MOZI1 is 65 to 70 km (~ 40 mi) to the west
and generally on the western extent of the Rocky Mountains.
Data Representativeness
Of the two nearest IMPROVE sites, Mt. Zirkel (MOZI1) and Rocky Mountain
National Park (ROMO1), ROMO1 is likely a bit more representative. It is
closer to the Rawah Wilderness, 40 km (25 mi) southeast of the southernmost
Rawah Wilderness Boundary, and is also generally east of the Continental
Divide. Neither site is specifically representative of impacts that may
occur as a result of emissions carried upslope from the North Platte Valley
that includes the Cheyenne and Laramie areas.
Also, see meteorological characterization discussions of Rocky Mountain
National Park and of the Mount Zirkel Wilderness Area.
Local Sources
Nearby Data Stations
Nearby monitoring network stations are shown in the data network
map and at
the US Climate Archive
and RAWS station US Climate
Archive sites. Except for Snotel sites, which usually collect
precipitation and temperature data daily or at six-hour intervals, there are
no meteorological data collection sites within the boundaries of the
Wilderness. The
Glendevey COOP site is located on the northeast boundary of the
Wilderness and has long term temperature and precipitation data. Nearest
stations with hourly data including wind data are the
Red Feather
Colorado RAWS site where data collection started in 1985, and the Rocky
Mountain NP CASTNET site ROM406 where data has been collected since 1994.
ROMO1 is located at the same site as the Rocky Mountain National Park
IMPROVE monitoring site, ROMO1.
The nearest long-term upper air station is at Denver/Stapleton, on the
plains at the foot of the Rockies. Either this station or Grand Junction
have regionally representative upper air data although both sites are in
terrain that is significantly different from terrain in Rawah Wilderness.
Wind Patterns
Wind patterns in the Rawah Wilderness Area are typical upslope/downslope
patterns, both at a local scale in the valleys and canyons within the
Wilderness, as well as at a mesoscale, with upslope/downslope flow from
lower elevations including the Laramie River valley and possibly the Front
Range. Mesoscale upslope flows may be particularly significant in bringing
pollutants into the Wilderness from sources in the Cheyenne and Laramie
areas, as well as from the large urbanized and agricultural areas from Fort
Collins to Pueblo. Upslope flows may at times be opposed at by prevailing
westerly winds. Front Range downslope winds can be enhanced by synoptic
features such as a low pressure trough over the Plains, and by a lee wave
effect when westerly winds cross the Divide into the Plains.
Rocky Mtn National Park wind roses are based on surface meteorological data
collected at the CASTNET site, ROM406, for the period 1995 – 2001 and
indicate annual and seasonal wind direction (direction from which the wind
is blowing) frequencies. Annual and seasonal wind roses may have some local
terrain effect but should be reasonably representative of represent exposed
locations at higher elevations of the Rawahs. Prevailing wind directions are
predominantly westerly, as indicated by the high frequency of northwesterly
wind directions in the seasonal and annual wind roses. Nighttime and daytime
wind roses show the diurnal pattern at ROM406. Nighttime winds are
predominantly from the northwest, the direction for night drainage as well
as for channeled westerly synoptic winds. The daytime wind rose shows a
significant southeast component, which is primarily a result of upslope
winds that occur both locally and as part of the Front Range upslope wind
pattern in the vicinity of the Rocky Mountain National Park and to some
extent in the Rawahs.
Transport pathways into the Rawah Wilderness include upslope flow from urban
and agricultural areas along the front range and Laramie River valley, as
well as upper level transport from distant source regions, consistent with
regional haze. Locally, transport from local sources such as wildland will
be upslope/downslope within valley and basins.
Inversions/Trapping
Emissions and pollutants are highly subject to trapping inversions in the
valleys and basins of the Rawah Wilderness. Higher elevations will typically
be above trapped local haze and may also be above regional haze trapped
below large-scale subsidence inversions. From May to October, long term
records show an average of about 0.5 air stagnation events per month during
this period in north central Colorado near the Rawahs, where a stagnation
event is defined as stagnation conditions that persist for 4 days or longer
(Wang and Angell,
1999).
Climatological Statistics
Climate data representative of the Rawah Wilderness is available at nearby
and representative data stations identified in the Nearby Data Stations
section.
Meteorological Indicators for Local Sources
Keywords
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Updated 30 April 2004
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