Site Name
IMPROVE:
PORE1
Region
California Coast Ranges, California Coast
Terrain
Terrain is shown in the 2 km terrain
map and the 20 km terrain
map.
Point Reyes Wilderness Area occupies 25,370 acres within the Point Reyes
National Seashore situated just north of San Francisco. Point Reyes National
Seashore is essentially a peninsula that extends into the Pacific Ocean some
20 km (12 mi) from the California mainland. The Wilderness consists
primarily of the complex terrain eastern section of the peninsula east of
and parallel to Highway 1, with elevations ranging from sea level to near
430 m (1,400 ft) at highest hilltops. Land is estuaries, windswept beaches,
coastal scrub grasslands, marshes, and some coniferous forest at higher
elevations.
The IMPROVE site representing the Point Reyes Wilderness is PORE1, located
centrally with respect to the three separate but closely grouped distinct
areas of the Wilderness, as shown in the 2 km terrain map and the 20 km
terrain map. Its elevation is 85 m (279 ft).
Representativeness
The PORE1 IMPROVE site is located centrally and at an elevation within the
small range of Wilderness elevations. It is very representative of aerosol
composition and concentration at Point Reyes Wilderness Area locations.
Nearby Population/Industrial Centers and Local Sources
The nearest major population and industrial center is the San Francisco Bay
area to which Point Reyes is almost adjacent but separated from by the Marin
Peninsula north of the Golden Gate. Downtown San Francisco is about 30 km
(20 mi) to the south. North Bay communities of Petaluma and San Rafael are
20 to 25 km (~15 mi) east, on the east side of the Bolinas Ridge.
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. The nearest network site that includes
hourly wind data is the
Barnaby
California RAWS site located at an exposed location near the crest of
Barnabe Mountain, elevation 378 m (1,240 ft). This site should be quite
representative of Point Reyes Wilderness Area locations.
Point Reyes
Light St California Climate Data, which does not include wind data, is
representative of the westernmost peninsula.
Twice daily upper air data collected at the Oakland RAOB site in the San
Francisco Bay Area and at the Vandenburg AFB RAOB on the coast near San Luis
Obispo to the south should characterize upper air structure in the Point
Reyes Wilderness Area. The Vandenburg site may be more representative of
lower altitudes at a maritime coastal site such as Point Reyes.
Wind Patterns
Prevailing winds at California coastal locations are generally from the
north or northwest throughout the year and especially in the summer months,
a consequence of the semi-permanent high pressure that lies off the Pacific
Coast. Southerly and easterly winds can occur during the winter, when the
Pacific High moves southward and weakens. This pattern is indicated in
monthly Arcata California Wind
Roses, from the Arcata/Eureka SAO (Surface Airways Observation) NWS site
on the California coast about 300 km (200 mi) north of Point Reyes, and is
also evident in data from the
Barnaby
California RAWS site. During the winter the southerly coastal winds
could be a mechanism for transport of Bay Area emissions to the Point Reyes
Wilderness Area.
The Point Reyes Wilderness Area is also subject to coastal land/sea breeze
circulation, with daytime sea breezes and weaker nighttime land breezes that
in some coastal locations can cause a sloshing effect, with transport and
return of near-coast emissions. This could be a mechanism for transport of
emissions from North Bay communities (Santa Rosa, Petaluma area) via the
Stemple Creek drainage that penetrates the coastal mountains just to the
north of the Point Reyes peninsula.
Potential local transport routes into the Point Reyes Wilderness Area
include Bay Area emissions transported northward during southerly flow along
the coast, especially in the winter months, and offshore flow from North Bay
communities associated with land/sea breeze circulation, especially during
the warmer months. The area is also subject to the influence of naturally
occurring marine aerosols.
Inversions/Trapping
Surface-based radiation inversions are infrequent in this coastal area. The
more common type of inversion, especially during the extended summer months
May to October, is the subsidence inversion over the eastern Pacific caused
by the persistent sub-tropical high-pressure system. Its base is typically
marked by a stratus cloud layer and is the height to which the atmosphere
pollutants can be mixed, the mixing height. High relative humidity below
drops drastically above. This situation is typical of California coastal
areas during the summer, and its inland extent can vary diurnally. Vertical
mixing is commonly restricted to 600 m (2,000 ft) or less.
Climatological Statistics
Eureka
California Normals Means and Extremes are representative of coastal
locations in Northern California.
Point Reyes
Light St California Climate Data, which does not include wind data, is
representative of the westernmost Point Reyes peninsula. More local data,
including representative wind data, are also accessible at the
Barnaby
California RAWS site.
Keywords