| |
Haleakala National Park |
(Also see Hawaii
Volcanoes NP Meteorological Description Page)
Site Name
IMPROVE:
HALE1 (Haleakala National Park)
Region
Hawaii (Maui)
Terrain
Haleakala National Park consists of
30,183 acres in central to eastern portions of the island of Maui, 24,719
acres of which are designated wilderness. Slopes of the Haleakala, or East
Maui, volcano comprise central and western Park areas. The Kipahulu Valley
occupies eastern Park areas. Park elevations range from 3,055 m (10,023 ft)
at the summit of Haleakala to sea level at the mouth of Kipahulu Valley on
the extreme eastern boundary. The Park thus includes a wide variety of
climate zones, from high mountain elevations above the Marine Boundary
Layer, to leeward lowlands that are dry relative to windward lowlands at the
same elevation. The Hawaiian Regional Description page includes a detailed
description of the climate zones of Hawaii. A detailed discussion is also
found in the Meteorological Description Page for the similar Hawaii
Volcanoes National Park.
The Haleakala National Park IMPROVE site is HALE1, located at an elevation
of 1,158 m (3,799 ft) on the northward slope of Haleakala, ~5.7 km northwest
of the Park Boundary. Terrain in the area is depicted in this detailed 20 km
terrain map and 2 km terrain map.
Representativeness
In general, aerosol measurements at HALE1 should be representative of
ambient concentrations at National Park locations at the same elevation.
However, the extreme climate variability over the range of elevation and
exposure in the National Park compels caution in aerosol source attribution,
especially with the sensitivity of particle size to moisture. Rainfall
gradients in Hawaii are among the steepest in the world. The HALE1 site has
exposure to northeasterly trade winds and may be more susceptible to rain
caused by orographic lifting than are most National Park areas on the
leeward side. Being at an elevation that is lower than the typical Marine
Boundary Layer height most of the time, the HALE1 IMPROVE site may
frequently be more representative of aerosols near the surface with
different back trajectories than those of upper air aerosols transported
from distant global scale source regions by upper level winds.
Nearby Population/Industrial Centers and Local Sources
Kahului Hawaii and the Wailuku area are about 24 km west-northwest and
downslope from HALE1, with no major intervening terrain features. The major
active volcano, Kilauea on the Big Island, is 188 km southeast of HALE1.
With northeasterly trade winds, SO2 emissions from Kilauea have been
observed to be eddy-transported clockwise around the west side of the Big
Island, and impact on Haleakala National Park is possible. See the Hawaii
Volcanoes NP Meteorological Description Page for a discussion of SO2
emissions from Kilauea. Agriculture (sugarcane) field burning may contribute
to high aerosol concentrations at HALE1 during the burning season. Sea salt
spray is a natural aerosol source.
Nearby Meteorological Network Data Stations
This map shows the location of the nearest air quality and meteorological
monitoring sites relative to the HALE1 IMPROVE site. The nearest RAWS site
is Kaupo Gap Hawaii, ~19 km southeast from HALE1, established in January,
1991. It is on the southerly slope of Haleakala and may have different local
wind direction patterns. The closest long-term NWS meteorological monitoring
station is the Honolulu Hawaii NWSFO. Hilo/Gen (PHTO) is the nearest (172 km
southeast from HALE1) upper air site, accessible via the University of
Wyoming Dept of
Atmospheric Science web page.
Wind Patterns
During trade-wind conditions, which predominate 80 to 95% of the time from
May through September, and 50 to 80% during the rest of the year, prevailing
wind directions at HALE1 should be generally northeast to southwest,
typically with speeds of 5 mps or greater. Downslope winds from Haleakala
should be evidenced at the site by nighttime southeasterly directions, and
daytime northwesterly directions. Exceptions to these conditions would occur
during frontal passages associated with synoptic weather systems, and, at
the site elevation, during upper atmosphere low pressure system passages.
Monthly Kahului wind roses (link to Kahului Hawaii wind roses archived) show
typical wind patterns at this sea level station 24 km northwest of HALE1,
with northeasterly surface flow year round and an additional southerly
component in the winter.
Inversions/Trapping
The predominant inversion phenomenon is the Trade-layer inversion, or Marine
Boundary Layer. The Marine Boundary Layer is more constant and has less
diurnal variability than continental inversions because of the oceanic
influence. Typical trade-layer inversion heights in the vicinity of
Haleakala NP are around 2000 m above sea level, with some variability (+/-
~1000 m) due to seasonal effects. The HALE1 site, at an elevation of 1158 m
(3799 ft), would thus probably be within this layer most of the time when
trade-wind conditions predominate. During this condition, relative humidity
will be typically be high, 70% or greater. When the Marine Boundary Layer
height is below the monitoring site, relative humidity will be much lower.
Climatological Statistics
Honolulu Hawaii
Normals Means and Extremes are representative of Hawaii sea level
climate characteristics. Other
Hawaii Climate
Summaries are available from the
Western Regional Climate Center.
Meteorological Indicators
Keywords
|
Last updated 10 December 2004
|