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Ansel Adams Wilderness Area |
(Also See Kaiser Wilderness
Area)
Site Name
IMPROVE:
KAIS1 (Kaiser Wilderness Area)
Region
Sierra Nevada Range
Terrain
Terrain is shown in the 2 km terrain
map and the 20 km terrain
map.
Formerly known as Minarets Wilderness, this Wilderness Area occupies 229,334
acres west of the Sierra Nevada crest, primarily the headwaters of the San
Joaquin North and Middle Forks. Elevations range from about 1,100 m (3,600
ft) where the San Joaquin River exits the Wilderness to the south, to 4,300
m (14,000 ft) at higher peaks near the Sierra Nevada crest in the north part
of the Wilderness. The San Joaquin River flows south and west from the
Wilderness and eventually opens up into the San Joaquin Valley 30 to 40 km
(20 to 25 mi) west of the Wilderness and just north of Fresno. This central
San Joaquin Valley area is the nearest major source region for anthropogenic
emissions that could affect visibility in the Wilderness.
The IMPROVE site representing Kaiser Wilderness Area is KAIS1, the Kaiser
Wilderness IMPROVE site, located 80 m (260 ft) below the crest of Chinese
Peak across Huntington Lake and the Big Creek drainage to the south. KAIS1,
elevation 2,573 m (8.439 ft), is about 15 km (10 mi) south of the
southernmost boundary of Ansel Adams Wilderness Area.
Representativeness
Data from KAIS1 should be representative of aerosol concentration and
composition in the Kaiser and Ansel Adams Wilderness Areas.
Nearby Population/Industrial Centers and Local Sources
The Ansel Adams Wilderness Area and vicinity are drained by the San Joaquin
River, which flows into the San Joaquin Valley, the nearest source region.
The San Joaquin River channel opens up into the San Joaquin Valley 30 to 40
km (20 to 25 mi) to the southwest, where the primary population center is
Fresno.
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
Mount Tom
California RAWS site is a mountain site, elevation 2,749 m (9,018 ft)
located 5 km north. Hourly data from that site includes wind data that
should be regionally representative. Lower elevation data, excluding wind
data, is collected at the
Huntington Lake
California COOP site. Data sites described for Sequoia and Kings Canyon
National Parks to the south, and Yosemite National Park to the north, may be
similarly representative of Kaiser Wilderness Area.
Upper air data is collected twice daily at the Oakland 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 evident in monthly Fresno California Wind Roses. KAIS1 is well exposed to regional winds and this pattern
should be generally consistent there as well. In the absence of synoptic
forcing, a diurnal mountain/valley flow pattern may be evident at KAIS1,
with easterly (from the east) drainage flows from higher slopes of the
Sierra Nevadas at night and westerly daytime upslope flow from the direction
of the San Joaquin Valley via the San Joaquin River. Although the site is
well above San Joaquin Valley elevations, transport and return of San
Joaquin Valley air at the KAIS1 IMPROVE site would be indicated by a diurnal
pattern of aerosol concentration during periods of stagnation over central
California.
Potential local transport routes into the Kaiser and Ansel Adams Wilderness
Areas include San Joaquin Valley emissions transported directly via diurnal
upslope/downslope flow, mixed upwards with afternoon mixing, or trapped
regionally under a persistent subsidence inversion. The most likely season
for incursion of San Joaquin emissions into the Kaiser and Ansel Adams
Wilderness Areas is summer, when afternoon upslope winds combined with
highest mixing heights in San Joaquin Valley provide optimal transport
conditions. Springtime incursions may be associated with agricultural and
forest prescribed burning in San Joaquin Valley and National Forest lands.
Autumn incursions are probably less frequent because of San Joaquin Valley
inversion that confines emissions to lower elevations.
Inversions/Trapping
Wintertime trapping inversions may be common in San Joaquin headwater
valleys and could restrict local emissions such as prescribed forest
burning. Wintertime surface based inversions are common in the San Joaquin
Valley, the principal source region for local emissions, although at heights
typically below Wilderness elevations. Fall and winter are less likely to
see Valley emissions transported to Kaiser and Ansel Adam Wilderness Areas
because of persistent low level San Joaquin Valley trapping inversions.
In the summer, the relatively shallow nighttime San Joaquin 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, at the lower end of Wilderness
elevations but still potentially affecting aerosols at the KAIS1 IMPROVE
site. 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), in the range of Wilderness elevations that are between
2,200 m (7,200 ft) and 3,146 m (10,320 ft).
Climatological Statistics
Huntington
Lake Climate Data represent lower Wilderness elevations.
Fresno
California Normal Means and Extremes are representative of climate
characteristics in the San Joaquin Valley. Other
Northern California
Climate Summaries are available from the
Western Regional Climate Center.
Keywords
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Last updated 13 November 2004
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