(Also see Marble Mountain
Wilderness Area)
Site Name
IMPROVE:
TRIN1 (Trinity)
Region
Klamath Mountains
Terrain
Terrain is shown in the
2 km terrain map and the
20 km terrain map.
The Yolla Bolly – Middle Eel Wilderness area lies on ~ 150,000 acres in the
Klamath Mountains region near the southern extent of the Cascade Range in
northern California, just west of the north end of the Sacramento Valley
near Redding. On the west side the Wilderness is drained by the North and
Middle Forks of the Eel River which flow west into the Pacific Ocean near
Redwood National Park. On the east side it is drained by the South Fork of
Cottonwood Creek which flows to the northern Sacramento Valley between
Redding and Red Bluff and is a conduit to that source region via upvalley
transport flow. The lowest elevation, 792 m, is on the eastern boundary
where Cottonwood Creek exits the Wilderness, some 600 m above the northern
Sacramento Valley floor at Redding. The highest elevation is 2,467 m at the
peak of Mt Linn.
The IMPROVE site representing the Yolla Bolly – Middle Eel Wilderness Area,
and the Marble Mountain Wilderness Area ~ 100 miles to the north, is TRIN1
(Trinity), located midway between the two Wilderness Areas in the upper
Trinity River valley. TRIN1 is situated on a ridgecrest of Pettijohn
Mountain at an elevation of 1007 m. It is 40 to 50 miles north of Yolla
Bolly – Middle Eel Wilderness. Also, it is within the Trinity River valley
and separated from the northern Sacramento Valley by the intervening Trinity
Mountains crestline with elevations of 900 m and higher.
Representativeness
Because of distance and intervening terrain, TRIN1 is probably not
influenced by local transport from the Sacramento Valley to the same extent
as Yolla Bolly – Middle Eel Wilderness except when Valley emissions are
transported across the Trinity Range during southerly flow conditions. It
should be representative of aerosol characteristics at Yolla Bolly – Middle
Eel during periods of more uniform regional haze, resulting from regional
forest fire events or transport from more distant source regions on a global
scale.
Nearby Population/Industrial Centers and Local Sources
The closest source region with emissions that may contribute to aerosol and
haze in the Yolla Bolly – Middle Eel Wilderness, and at the TRIN1 IMPROVE
site, is the Sacramento Valley, with its northern extreme at nearby
communities of Redding and Red Bluff. The Sacramento Valley may thus provide
a link to emissions from the larger Sacramento and San Francisco Bay areas
during low level southerly flow.
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. A nearby meteorological network station with good exposure and data
for correlating with aerosol measurements at TRIN1 is the
Lowden
California RAWS site south of TRIN1 at an exposed elevation of 951 m,
close to the TRIN1 elevation. The
Redding Airport
California RAWS site and
Redding
Municipal California SAO site provide meteorological data representative
of the northern Sacramento Valley.
The upper air site closest to the Yolla Bolly – Middle Eel and Marble
Mountain Wilderness Areas, and the TRIN1 IMPROVE site, is the Medford Oregon
RAOB site
Wind and Transport Patterns
Synoptic winds in the region are generally northwesterly (from the
northwest), with an additional component of more southerly winds in the
winter with the weakening of the Pacific High Pressure System. This pattern
is indicated in monthly
Arcata California
Wind Roses, from a coastal site about 80 miles northwest of Yolla Bolly
– Middle Eel Wilderness Area and about 70 miles west of the TRIN1 IMPROVE
site.
In the interior northern Sacramento Valley, linked to the central California
valleys source region, flow and transport patterns are more in line with
valley orientation. At times, and especially during warm months from May to
October, there is a significant southerly component of flow in the
Sacramento Valley, evident in
Sacramento
California Wind Roses. Southerly flow from the Sacramento and Bay areas
is frequently caused or reinforced by a summertime thermal low over the
northern Sacramento Valley, a condition that may be the most conducive to
transport into the Yolla Bolly – Middle Eel Wilderness and towards the TRIN1
monitoring site.
Potential local transport routes into the Yolla Bolly – Middle Eel
Wilderness and the TRIN1 IMPROVE site include Sacramento Valley emissions
transported directly via diurnal upslope/downslope flow, mixed upwards with
afternoon mixing, or trapped regionally under a persistent subsidence
inversion. Highest summertime measured concentrations at TRIN1 may also be
associated with regional forest fire events or transport from distant source
regions.
Inversions/Trapping
Wintertime surface based inversions are common in the Sacramento Valley and
could extend upwards to lower Yolla Bolly – Middle Eel Wilderness elevations
on the east side, although probably not to the TRIN1 monitoring site which
is higher in elevation and further north. Fall and winter are less likely to
see Sacramento Valley emissions impacting the TRIN1 site for this reason.
In the summer, the relatively shallow nighttime Sacramento Valley boundary
layer is generally mixed to heights of at least 1,000 m (> 3,000 ft) above
the ground on a typical summer day, close to the TRIN1 site elevation.
Persistent summer inversions are usually larger scale subsidence inversions
associated with the establishment of the semi-permanent Pacific
high-pressure system and can result in 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), well above the TRIN1 site elevation.
Climatological Statistics
Redding
California Normals Means and Extremes are representative of the northern
Sacramento Valley. Other
Northern California
Climate Summaries are available from the
Western Regional Climate Center.
Keywords