Weather 101:

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Weather 101 What Makes the Weather and Why
Does It Do What It Does?
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Part 1 Spinning Through The Solar System
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Its A Small World After All The relative size
of the Earth compared with the planets and the
sun.
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The Earths axis is tilted about 23 degrees from
the plain of the Earths orbit. This tilt
creates the the four seasons.
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The Earth is actually closer to the sun
(perihelion) during the Northern Hemisphere
Winter, about 3,000,000 miles closer. The slight
increase in Solar energy is dwarfed by the 23
degree tilt of the Earths axis.
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Most of the suns energy arrives in the form of
visible light and low infrared. It changes to
heat energy when it hits a surface, creating the
greenhouse effect.
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Although the atmosphere can be measured over 100
miles above the Earths surface, all of what we
call weather occurs within the first 10 miles.
This layer is called the troposphere and contains
most of the mass of the atmosphere.
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At sunrise and sunset, very little of the suns
energy reaches the Earths Surface. Most is
reflected or blocked by the Atmosphere!
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That is why it is so cold at the poles. Even in
the summer when the sun shines 24 hours a day, it
never gets very high in the sky and does little
to warm the frozen waste!
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Part 2 Spinning Around The Earth (The Coriolis
Effect)
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The Coriolis Effect is an apparent deflection to
the right of anything moving freely north or
south above the surface of the earth. It results
from the fact that, relative to the earth, an
object at the poles appears to be motionless,
while an object on the equator appears to by
moving east at nearly 1,000 miles per hour!
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As air at the surface flows from high pressure to
low pressure, the flow appears to be deflected to
the right. This results in the air spiraling into
the low in a counter-clockwise direction. Air
flowing away from high pressure produces a
clockwise flow.
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Unequal heating of the earths surface plus its
spinning (Coriolis Effect) produces global wind
patterns. Rising air near the equator (low
Pressure) and sinking air around 30 degrees north
and south (high pressure), help create the trade
winds and the prevailing westerlies.
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The hurricane has low pressure at the surface,
producing a counter-clockwise flow, with high
pressure at the top of the storm, producing a
clockwise flow of air around 40,000 feet.
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Part 3 Cycling Through the Water Cycle
condensation
precipitation
transpiration
evaporation
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Warm air can hold more water vapor than cold
air!
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Precipitation is almost always generated by humid
air rising into cooler air aloft, causing
condensation. The lifting can be orographic,
thermal or synoptic (fronts and jet streams).
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Evaporation has a cooling effect on the
environment, absorbing heat to make the change
from water to water vapor. Condensation gives
off heat, warming the environment and often
adding instability to the atmosphere. The heat
of condensation is a key ingredient in producing
Floridas afternoon thunderstorms and powering
tropical cyclones.
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Part 4 Putting It All Together
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Air has the tendency to take on the
characteristics of the surface it is sitting on.
If the surface is cold and dry, like Siberia and
Northern Canada, the air quickly becomes cold and
dry. A shift in the jet stream may cause this
mass of cold air to move south. The leading edge
of the cold air mass is called the cold front.
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The cold air is more dense than the warmer air
around it. As it moves, it displaces the warmer
air upward. The warm air cools as it ascends,
causing condensation, which produces clouds,
which produce precipitation.
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Air that sits over warm water will soon become
warm and very humid. The Gulf of Mexico and the
Caribbean provide ideal breeding grounds for
these warm, tropical air masses. The moist air
is often pulled northward by mid latitude low
pressure systems, providing fuel for much of the
rain for the eastern 2/3 of the United States.
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Since the warmer air is lighter, the only way to
have a warm front is if the colder air is
retreating. The warmer air will often ride up
and over the slowly retreating colder air,
producing a large area of clouds and rain. This
over-running rain can be quite heavy in slow
moving systems.
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Cirrus Clouds
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Alto cumulus clouds (mid-level)
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Cumulonimbus (thunderstorm)
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Nimbostratus (low clouds)