Continuation of the notes for the second exam
Climatic Variability - Keynote pdf
Latitude - Keynote pdf
Pacific Ocean - Keynote pdf
Atmospheric Circulation - Keynote pdf
Terrain - Keynote pdf
A major feature of Hawaii's climate is its low variability.
Only two seasons:
Kau is the warm season when the sun is almost directly overhead and
winds are reliably from the northeast.
Ho'oilo is the season of cooler temperatures, a lower sun, more variable winds,
and extensive rains.
The mountainous topography makes Hawaii one of the most spatially diverse on Earth.
Rainfall, solar radiation, temperature, humidity, and wind exhibit spectacular changes over short distances.
Rainfall in Waikiki
is averages 50 cm/yr.
A desert is defined as <25 cm/yr.
Tantalus averages 400 cm/yr.
Temperatures range from freezing cold on the 4000 m mountaintops to hot on the leeward side of the largest mountains.
The large variations in climate result in a large range of biodiversity.
In this respect, Hawaii resembles a continent in miniature, with ecosystems ranging from deserts to tropical rain forests to frozen alpine tundra, all within close proximity.
The primary controls on Hawaii's climate are
Ranging from 19 to 22oN latitude, the islands lie near the boundary between the tropics and the subtropics, which is centered at 30oN.
It is a region
of persistent Trade Winds and high atmospheric pressure.
At these low latitudes, intensity of solar radiation varies little throughout
the year.
The daylight hours in Hawaii vary by only 2.5 hr annually in Hawaii, whereas in Montreal the yearly variation is almost 7 hours.
Hawaii is one of the most isolated lands on Earth, surrounded
by 1000s of kilometer of water in all directions.
Therefore the atmosphere is strongly influenced by the oceans, which
Because of ocean water's Several factors are responsible for low variability of ocean temperatures compared to land temperatures:
As opposed to the continentals, where land surfaces strongly influence the atmosphere, Hawaii has one of Earth's most pronounced maritime climates.
The ocean moderates the temperature of maritime climates
The Hadley Cell of the general atmospheric circulation system profoundly influences the climate of the islands.
Warm, moist, low-density air rises at the equator and cool, dry, high-density
air descends at 30oN in the center of the subtropical climatic region.
The return of air to the equator across the surface is the source of the persistent
Northeast Trade Winds.
A prominent temperature inversion, the Trade Wind inversion, forms at over
this region, especially in the summer.
Temperature inversions form as sinking air meets rising air, creating a situation
in which moist surface air cannot continue to ascend.
The Trade Wind inversion forms between 1500 m and 3000 m, where the clouds
form.
These low altitude clouds are much less effective a producing rain, so the Hawaii
region has relatively low annual rainfall.
And the mountaintops commonly are cloudless deserts.
Winter weather brings more rain because the high-pressure system to the north
weakens in the winter.
This brings Kona winds and rain, especially to the leeward side of the islands.
The varying terrain of Hawaii also significantly affects the climate patterns.
In mountainous regions the wind is force to rise up and over the slopes causing
the orographic precipitation that is so common to the islands.
Low lying areas are dry because the air does not ascend much.
On the largest volcanoes, the trade wind inversion prevents the atmosphere from ascending, and the wind must flow around the mountain.
Cloud formation and rainfall associated with the interaction of trade winds, the inversion, and island topography are responsible for the incredible climatic diversity of Hawaii.
The notes for the second exam are continued in Tsunamis