Site Name
IMPROVE: ROMO1, RMHQ1 (3/2/88 – 9/15/90)
CASTNET: ROM406
Region
Southern Rockies
Terrain
Terrain is shown in the 2 km terrain
map and the 20 km terrain
map.
Rocky Mountain National Park is
located abreast the Continental Divide in north central Colorado. Terrain is
mountainous and varied, with elevations ranging from near 2,500 m (8,000 ft)
at valley bottoms to a high of 4,347 m (14,259 ft) at Long’s Peak. Due to its
location on the Divide, the western slope is directly impacted by prevailing
westerly winds and receives more precipitation than the eastern slope which
is in the rain shadow of the Rockies. The town of Estes Park averages 13.1
inches of precipitation; the town of Grand Lake 19.95 inches per year. The
National Park includes the headwaters of the westward flowing Colorado River
and eastward flowing Cache la Poudre and Thompson Rivers.
The IMPROVE site, ROMO1, and CASTNET site, ROM406, are at the same location,
just east of the Park boundary, at an elevation near 2,750 m (9,020 ft). The
Rocky Mountain NP (Headquarters) site, RMHQ1, is located just within the
Parks eastern boundary, near US Highway 34, at an elevation of 2,400m (7,872
ft).
Data Representativeness
High elevations within the Park may periodically be above local and regional
haze, and in such cases not well-represented by measurements at ROMO1. The
ROMO1 site is near lower elevations of the upper Tahosa Cr. Drainage. ROMO1
aerosol measurements should be well representative of aerosol composition
and concentration at similar elevations within the Park east of the Divide.
The earlier IMPROVE site RMHQ1 was located in a moraine basin and may be
subject to bias by aerosols trapped and isolated locally during
surface-based radiation inversion conditions. Additional examination of site
exposure for these sites should be included in any analysis of aerosol
composition and source attribution.
Local Sources
Local sources include the town of Estes Park and particulate matter in
plumes from prescribed and wild fires.
Nearby Data Stations
The Rocky Mountain NP CASTNET site ROM406 has collected meteorological data
since 1994 and is located at the same site as the IMPROVE monitoring site,
ROMO1. ROM406 probably provides the best representative meteorological data
for the National Park, although wind directions may be influenced by local
terrain. Other nearby monitoring network stations are shown in the data
network map and at the
US Climate Archive and RAWS
station US Climate Archive sites. 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 Rocky Mountain National Park.
Wind Patterns
Wind patterns at Rocky Mountain National Park are typical upslope/downslope
patterns, both at a local scale in the valleys and canyons within the Park,
as well as at a mesoscale, influenced by the Front Range. Front Range
upslope winds may be particularly significant in bringing pollutants into
the Park area from the large urbanized and agricultural areas from Fort
Collins to Pueblo. 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. This sometimes
results in severe high-speed foehn winds, locally referred to as Chinook
winds, in lee side canyons such as the Big Thompson canyon. This may be
effective at times in ventilating the atmosphere above eastern National Park
locations.
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 represent exposed locations at higher elevations.
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.
Transport pathways into Rocky Mountain National Park include upslope flow
from urban and agricultural areas along the front range, as well as upper
level transport from distant source regions, consistent with regional haze.
Locally, transport from local sources such as wildland fires and emissions
within the Estes Park area 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 Rocky Mountain National Park. 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 Rocky Mountain
National Park, 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 Rocky Mountain National Park is available via
the ROM406 CASTNET site described in the Nearby Data Stations section.
Meteorological Indicators for Local Sources
Keywords