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MORE.TXT
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1994-01-26
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Clouds are attracted to low pressure areas; thus, you rarely see clouds
under high pressure conditions. Clouds are formed from water evaporating
from the earth. Adiabatic Rate is the rate at which the air temperature
falls with altitude. These rates are calculated in degrees per 1000 feet.
There are different rates depending whether you're calculating below the
clouds, or in the clouds. These rates can be affected by local conditions,
but are used as a good, standard measurement.
Assuming you don't have fog conditions, the Dry adiabatic rate starts at
ground level. This rate is 5.5 degrees F. per 1000 feet. The Wet adiabatic
rate varies, but it is 2 to 5 degrees F. per 1000 feet. The following
diagram helps explain this process:
Wind Direction --> Clouds formed by Orographic Lifting.
_ _ _
Above condensation level, ▒░ / \ As the air descends,
cooling takes place at 3.3 ░▒░▒ / \ it is no longer sat-
degrees F. per 1000 feet. \ \ / \ urated and therefore
/ \ warms at 5.5 degrees
Wind ░▒░▒░▒░ ____/ \ F. per 1000 feet.
Direction --> ░▒░▒░▒░▒░ / \
\ \ \ \ _/ <-- Condensation \__
Rising air cools \ \ \ / Begins \
before condensation / \
at 5.5 degrees F. / (Mt. Shasta) \
per 1000 feet. /________________________________\
Water vapor affects weather and climate in three ways:
1) Water vapor is the only gas in the atmosphere that condenses under normal
atmospheric conditions.
2) It is the most important gas in our atmosphere for absorbing both
shortwave solar radiation and long wave terrestrial radiation (radiation by
Earth). Thus, water vapor is critical in regulating air temperature near
the Earth's surface.
3) It is a source of 'latent' or stored energy. This is the energy that
drives the movement of air masses over the Earth. Latent heat is the heat
energy gained and stored by water molecules as they change state from ice,
to water, then to vapor. Latent heat energy is moved and expended over
large areas of the Earth.
Evapotranspiration is the process by which plants return water vapor to the
atmosphere. This quantity is quite substantial in farming communities.
The irrigation/evapotranspiration cycle is what's known as a 'consumptive'
use because it does not return water to the local vicinity.
Our great, natural deserts are primarily around the 30 degrees north
and 30 degrees south regions of the equator. Why? Those are the areas
in between some of the major global wind patterns. These are caused by
the 'Coriolis Effect' which is prompted by the Earth's rotation. In the
northern hemisphere, this area is between the Northeast Trade winds, and the
Westerlies. Old time sailing ships were known to get stuck in these areas
for months on end...many unknowing people died.
------------------------------------------------
- Seasons -
The Meteorological Season is from September 1 to August 30.
Summer Solstice : June 21 (summer starts)
Autumnal Equinox : September 22 (autumn starts)
Winter Solstice : December 21 (winter starts)
Vernal Equinox : March 20 (spring starts!)
Maximum Temperature : Late July
Minimum Temperature : Late January
High radiant energy absorbed : About June 20
Low radiant energy absorbed : About December 20