Representative IMPROVE Site
IMPROVE site: MORA1
CASTNET site: MOR409
Region
Cascades
Terrain
The Mount Rainier National Park IMPROVE site is located at an elevation of 427 m (1,401 ft)
within the Nisqually River Valley, some 30 km (18.5 mi) west-southwest from the
summit of Mount Rainer as shown in this
figure. The orientation of the drainage is east to west, with an
elevation drop of about 60 ft/mile. Where the Nisqually River empties into Alder
Lake reservoir (3 miles) west of the site the River elevation is ~ 367 m 1,204
ft. The valley bottom at the monitoring site is about 1.5 km (0.9 mi) wide, with
the monitoring site at the northern edge of the valley bottom. Elevation rises
to 450 m (1,475 ft) at a distance of 2 km (1.25 mi) north and 3 km (1.9 mi) south
from the monitoring site.
Regional ground cover is predominantly fir and pine forest.
Nearby Population/Industrial Centers
The small community of Ashford (pop ~300) is located about 6 km (3.7 mi) east of
the site. The nearest major population center is Tacoma, some 50 to 60 km (~ 35
mi) due northwest. Washington State Highway 706, a main entrance to the National
Park from the west, goes through the valley within 1 km of the monitoring site.
The Centralia power plant, which has implemented emission controls in recent
years, is located near Centralia, 60 km (37 miles) due west from the monitoring
site
Wind Patterns
Generally, wind directions at site should be channeled to an east/west
direction. In absence of synoptic forcing, site should be characteristic of
mountain/valley circulations, with easterly (from the east) nighttime drainage
flow and westerly daytime upslope flow in the valley. The west to east
orientation of the valley may serve to enhance synoptic westerly wind flow.
Historical data show predominantly east and northeast directional flow during
October – December and westerly flow during January – February. The following
windroses, based on surface meteorological data collected at the site for the
period 1996 – 2001, show directional frequencies for all hours, for nighttime
hours indicative of drainage flow, and for afternoon hours indicative of upslope
flow.
Inversions/Trapping
This valley may be subject to inversion and trapping of pollutants during
periods of high pressure and stagnation. In those cases, the monitoring site,
located at the bottom of the valley, would be contained within the trapped
stable layer.
Meteorological Statistics
(Table of annual/seasonal precipitation, temp, rh, etc.)
Especially frequency of high RH and precipitation, which may provide moisture
needed for particle formation.
Meteorological Indicators
Five years of aerosol data show that most of the 20% worst extinction days
occurred during summer months, dominated by sulfates and OMC (Organic Mass by
Carbon). Site observers, familiar with conditions at the site, report that this
has not been associated with wildland fires over that time. Summertime maxima
likely result from greater summertime photochemical secondary aerosol
production, as well as longer upwind transport distances that occur during the
summertime. Meteorological indicators of enhanced light extinction would be
those associated with transport from nearest major source regions to the west
(e.g. Olympia, Tacoma), e.g. light westerly flow.
Nearby Data Stations
Meteorology (wind speed, wind direction, temperature, relative humidity,
precipitation) is monitored at the aerosol site. Meteorological data are
available at:
http://www.epa.gov/castnet//metdata.html
Keywords
Valley
Inversion
Channeling
Mountain/valley circulation