(Also see Mount Adams Wilderness)
Site Name
IMPROVE:
WHPA1 (White Pass)
Region
Northern Cascade Range
Terrain
Terrain is shown in the 2 km terrain map and the 20 km terrain map.
The Goat Rocks Wilderness occupies 105,000 acres on the crest of the Cascade
Range between Mt Rainier and Mt Adams in southwestern Washington. On the
west side it includes headwaters tributaries of the Cowlitz River that flows
west to the Columbia River. On the east side it includes headwaters of the
Tieton River that flows towards Yakima Valley and the city of Yakima, 80 km
(50 mi) east. Elevations range from 2,500 m (8,201 ft) at the summit of
Gilbert Peak to near 900 m (3,000 ft) where streams exit the Wilderness on
the east and west boundaries.
The IMPROVE site representing Goat Rocks and Mt Adams Wilderness Areas is
WHPA1 located on the northern Goat Rocks Wilderness Area boundary at White
Pass Ski Resort near White Pass Washington, on the crest of the Cascade
range. The monitoring site elevation is 1,830 m (6,002 ft), corresponding to
a standard pressure height of 812 mb.
Representativeness
WHPA1 is at a well-exposed ridge crest location and should be very
representative of aerosol concentration and composition at similarly exposed
locations in the Goat Rocks and Mount Adams Wilderness Areas. Its elevation
and exposure should also make it representative of regional characteristics
and transport from distant source regions at pressure heights near 850 mb
that are relatively unperturbed by terrain effects. The site is near a ski
lift.
Nearby Population/Industrial Centers and Local Sources
The significant population centers and source regions nearest to the Goat
Rocks Wilderness and the WHPA1 IMPROVE site are Seattle and the Puget Sound
area 100 (60 mi) to the northwest and Portland Oregon 120 km (75 mi) to the
southwest. The Centralia power plant, which has implemented emission
controls in recent years, is located near Centralia Washington 100 km due
west near the Cowlitz River that has origins in the Goat Rocks Wilderness.
Regional forest fires are likely the cause of some of the highest aerosol
concentrations seen at WHPA1.
Nearby Meteorological Data Stations
Nearby meteorological monitoring network stations are shown in the data
network map and at the
RAWS station US Climate Archive
site. There are no stations with high time resolution (hourly) data near the
WHPA1 IMPROVE site, though there is a SNOTEL site nearby. The nearest RAWS
site, with hourly data including wind data is the
Hager Creek
Washington RAWS site elevation 1,098 m (3,600 ft), located on elevated
terrain overlooking the Cowlitz River valley just west of the western
Wilderness boundary. Data from that site may be generally representative of
concurrent meteorology at the WHPA1 site. A CASTNET site, MOR409 (Mount
Rainier NP), is located in the Nisqually River Valley downvalley from Mount
Rainier National Park (see Mount Rainier NP Meteorological Description
Page).
Wind Patterns
Synoptic winds in the region are generally westerly. During the winter, with
high pressure over the Great Basin and Idaho and low pressure west of the
Cascades easterly gradient (synoptic) flow is common. The WHPA1 IMPROVE site
is located near the crest of the Cascades and should be well exposed to
these upper airflows and to aerosols transported aloft from upwind sources.
Lower Goat Rocks Wilderness elevations may see more typical mountain/valley
circulation patterns, especially during periods of weak synoptic forcing,
which bring valley air to higher elevations during the day. At WHPA1,
aerosols transported with this mountain valley circulation would likely show
a diurnal pattern.
Inversions/Trapping
Because of WHPA1’s high elevation relative to surrounding terrain it should
be generally above surface based valley inversions in Wilderness Area
headwaters basins. Summertime subsidence inversions associated with the
establishment of the semi-permanent Pacific high-pressure system can result
in regional aerosol buildup over periods of days. Subsidence inversion
heights are typically at elevations of 2,000 to 3,000 m (6,000 to 10,000
ft), near the WHPA1 site elevation.
Climatological Statistics
Olympia
Washington Normals Means and Extremes are representative of low
elevation locations in western Washington source areas upwind of Goat Rocks
Wilderness.
Yakima Washington Normals Means and Extremes are representative of
climate characteristics at low elevation locations east of Goat Rocks
Wilderness Area. Other
Washington Climate
Summaries are available from the
Western Regional Climate Center.
Keywords