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Agua
Tibia Wilderness Area |
Site Name
IMPROVE:
AGTI1
Region
Southern California Ranges
Terrain
Terrain is shown in the 2 km terrain
map and the 20 km terrain
map.
The Agua Tibia Wilderness Area comprises most of the Cleveland National
Forest, 15,934 acres, in the northwest part of the isolated Palomar Mountain
Range of southern California. The area is mountainous, cut by many deep
canyons that reach downward towards flatter terrain of coastal southern
California between Los Angeles and San Diego. Elevations range from near 500
m (1,700 ft) in the canyon bottoms to the 1,548 m (5,077 ft) Eagle Crag Peak
at the southeast corner of the Wilderness Area, although there are higher
elevations along the main part of the Palomar Range extending further to the
southeast. West of the Wilderness, canyons exit into the San Luis Rey River
drainage that empties into the Pacific Ocean near Oceanside, about 50 km (30
mi) southwest of the Wilderness.
The IMPROVE site representing the Agua Tibia Wilderness is AGTI1, located
close to Highway SR-79 near the northern Wilderness boundary at an elevation
of 507 m (1,663 ft) which is near the lower end of the range of Wilderness
elevations. It is also within the typical elevation range for the transition
zone between the coastal marine layer and the drier air above. The elevation
range for this transition zone is typically 300 to 600 m (1,000 to 2,000
ft).
Representativeness
The AGTI1 IMPROVE site is at an elevation of 507 m, thus very representative
of lower Agua Tibia Wilderness elevations in general. At this elevation it
may at times be within the coastal marine inversion, if and when the
inversion extends inland to this site that is about 50 km (30 mi) from the
coast. In such cases it would be less representative of higher Wilderness
elevations above the penetrating marine layer. Note that there may be a
question whether the marine layer extends this far inland. This condition
would be manifested by relatively high concurrent humidity.
Nearby Population/Industrial Centers and Local Sources.
The Wilderness is above the foothills of the sprawling and heavily populated
and industrialized South Coast Air Basin immediately to the north. The
Temecula Valley just to the west of the Wilderness is a rapidly growing
area, and associated urban emissions may thus also have increasing impact on
aerosol concentration in the Agua Tibia Wilderness.
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 identified network
meteorological monitoring sites within Wilderness boundaries. The
Palomar Mountain
Observatory Site is a COOP site with climate data representative of
higher Wilderness elevations. There are numerous surface meteorological
monitoring sites in coastal southern California that should provide data
that is regionally representative for lower elevations. These should include
sites at elevations and inland distances similar to the AGTI1 IMPROVE and
representative thereof.
The San Diego/Miramar RAOB site conducts atmospheric soundings twice daily
that should be regionally representative.
Wind Patterns
Overall, the prevailing wind direction in the larger southern California
region that includes the Agua Tibia Wilderness is south to southwesterly.
This is evident in Los Angeles wind roses. There are seasonal phenomena that modify this overall pattern.
During the winter, higher pressure over the Mohave Desert results in winds
blowing from the desert towards the California south coast. This frequently
takes the form of Santa Ana foehn desert winds, which may carry large
amounts of dust (PM10) into the area. Lower wilderness elevations on the
west side of the Palomar Mountains may at times experience afternoon sea
breezes during the summer if they penetrate far enough inland. Otherwise,
local circulations are likely to be typical mountain upslope/downslope,
especially in canyons exiting to the west.
Potential local transport routes into the Wilderness include emissions from
coastal urban areas to the west transported directly via upslope winds,
mixed upwards with afternoon mixing, or trapped regionally under a
persistent subsidence inversion. Windblown dust from desert regions to the
east may impact Wilderness locations during the winter when interior high
pressure is established and persistent.
Inversions
Marine inversions resulting from sea breeze penetration into coastal areas
west of the Wilderness may at times extend to lower elevations of the
western Wilderness during afternoon and overnight hours in the summer.
Higher wilderness elevations should generally be above this coastal
inversion that typically extends vertically to between 300 and 600 m (1,000
and 2,000 ft). This existence of this condition at the AGTI1 IMPROVE site
may be manifested by relatively high humidity readings at monitoring sites
at similar inland distances and elevations.
Climatological Statistics
A warm, dry Mediterranean climate prevails over mountain elevations of the
Cleveland National Forest that includes the Agua Tibia Wilderness; hot in
the summer, mild in the winter. Most of the precipitation comes as rain
during the winter months. Rain averages 25 inches annually and falls usually
from January through April. Climate data from the
Palomar Mountain
Observatory Site should be representative of higher wilderness
elevations.
Southern California Climate Summaries for stations at lower
elevations more representative of climate at lower Wilderness elevations,
and at the IMPROVE AGTI1 site are available from the
Western Regional Climate Center.
Keywords
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Last updated 13 November 2004
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