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San Rafael Wilderness Area |
Site Name
IMPROVE:
RAFA1
Region
California Coast Ranges
Terrain
Terrain is shown in the 2 km terrain
map and the 20 km terrain
map.
The San Rafael Wilderness Area comprises some 200,000 acres in the San
Rafael and Sierra Madre Mountain Ranges in southern California, near the
southernmost extent of the Coast Ranges that separate the coast from the
Central Valley and deserts of interior California. These east-west ranges
form part of the barrier between the southernmost extent of the central
California valley and the Santa Barbara Coast 30 km (20 mi) to the south of
the southeastern Wilderness boundary. The Sisquoc River flows west towards
the Pacific Ocean through the heart of the Wilderness from its headwaters
near the eastern boundary, between the Sierra Madre range on the north and
the San Rafael range on the south. Elevations range from 355 m (1,166 ft)
near the confluence of the Sisquoc River with Manzana Creek in the west to
over 2070 m (6,800 ft) on Big Pine Mountain near the eastern boundary.
The IMPROVE site representing the San Rafael Wilderness is RAFA1, located
near the crest of a low ridge a few km outside the southern Wilderness
boundary at an elevation of 953 m (3,126 ft).
Representativeness
The RAFA1 IMPROVE site should be quite representative of Wilderness
conditions in general. It is on a well-exposed ridge location near the
southern boundary at an elevation near the midrange of Wilderness
elevations. It may be less representative of lower Wilderness elevations
along the Sisquoc River valley if and when they are within a lower level
valley inversion. The lower Sisquoc River is also subject to occasional
penetration of onshore flow from the Pacific Ocean that can bring high
humidity and fog, although this may be a relatively infrequent occurrence.
Nearby Population/Industrial Centers and Local Sources
The San Rafael Wilderness is centrally located with respect to three areas
with potential to impact visibility therein. The southern Central Valley of
California to the north, an agricultural valley with potential for impacting
visibility during Santa Ana conditions; coastal areas of Santa Barbara
County; and the Los Angeles basin from which emissions may be channeled into
the Wilderness via a coastal river valley near Ojai or transported aloft
during easterly upper airflow during the winter or with return flow of
emissions transported over the Ocean.
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. No network meteorological monitoring
sites are shown within Wilderness boundaries. There is a RAWS site, the
Figueroa
California RAWS site, very close to the RAFA1 IMPROVE site that should
provide good representation for meteorological conditions concurrent with
RAFA1 aerosol monitoring. Long term data may also be available from the
Santa Ynez Airport.
Twice daily upper air data is collected at the Vandenburg AFB RAOB site on
the coast 50 km (30 mi) west of the San Rafael Wilderness.
Wind Patterns
Regional winds are generally from the north or northwest throughout the
year, a consequence of the semi-permanent high pressure that lies off the
Pacific Coast. Southerly and easterly winds occur during the winter,
especially in the morning. Upper-level winds from the south and east are
infrequent during the summer. This pattern is indicated in monthly
Santa Maria Wind Roses, from Santa Maria
located on the coast west of San Rafael Wilderness Area. There are local and
seasonal phenomena that modify this overall pattern. During the winter, when
the Pacific High weakens, high pressure in the interior can cause easterly
winds that can take the form of Santa Ana foehn desert winds that may bring
windblown dust (PM10) into the area. At times this situation may also bring
windblown dust from the agricultural areas of the southern Central Valley
into northern Wilderness areas. Also during Santa Ana conditions, urban
pollutants emitted in Santa Barbara, Ventura County, and the South Coast Air
Basin (the Los Angeles region) are moved out to sea. These pollutants can
then be moved back onshore into Santa Barbara County in what is called a
"post Santa Ana” condition, and can effect all of the county. During
regional stagnation periods, diurnal onshore/offshore flow may extend into
lower reaches of the Sisquoc River valley bringing high humidity and
resulting fog. This could also be a transport mechanism for local emissions
from coastal Santa Barbara county areas. Also, during regional stagnation
periods, a diurnal upslope/downslope pattern is likely in the Siquoc River
valley generally, with upslope flow from west to east during the day and
reverse downslope drainage flow at night.
Potential local transport routes into the Wilderness include Los Angeles
Basin emissions transported directly during easterly wind conditions either
aloft or through valley channels near the eastern Wilderness, Central Valley
windblown agricultural dust transported into the northern Wilderness areas
of the Sierra Madre range, local emissions carried into the lower Sisquoc
River valley via upslope/downslope or onshore/offshore flow, and return flow
transport of South Coast emissions carried out to sea.
Inversions/Trapping
Within Santa Barbara County, surface temperature inversions (0 – 150 m,
0-500 ft) are most frequent during the winter. Coastal surface inversions or
marine inversions may not extend into higher Wilderness elevations, and the
most likely trapping and accumulation situation is a prolonged summertime
subsidence inversion (300 – 600 m, 1000-2000 ft). The subsidence inversion
is very common during summer along the California coast. When inversions
that could confine aerosols within the lower Sisquoc River valley occur,
either subsidence or surface inversions, they may not be observed as higher
concentrations at the RAFA1 IMPROVE site, located near a ridge crest
elevation of 953 m (3,126 ft), up to 600 m (2,000 ft) above the valley
bottom.
Climatological Statistics
Climate date representative of higher Wilderness elevations can be accessed
from the
Figueroa California RAWS site, located close to the RAFA1 IMPROVE site.
New Cuyama
Fire Station, California Climate Data, or data from the Santa Ynez SAO
station, may be representative of lower elevations. Long term
Santa Barbara
Normals Means and Extremes represent low elevation coastal locations.
Keywords
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Last updated 13 November 2004
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