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Weather Systems
© Lisa Michalek
Energy in the Atmosphere
The sun is the major source of energy for Earth.
 Stars, including our sun, give off electromagnetic
energy over the wide range of wavelengths that
make up the electromagnetic spectrum.
Earth’s atmosphere filters out most of the short-wave
Most of the output from the sun that reaches the surface
of Earth is in the narrow band that we perceive as visible
Earth also radiates electromagnetic energy, mostly
in the infrared (heat) part of the spectrum.
Electromagnetic Spectrum
 Of
the solar radiation that
reaches Earth, about ¾
evaporates water from the
Evaporation is the change of state from liquid to
gas or vapor.
• Evaporation adds energy and matter to the
• Decreases when water is covered or cooled.
• Increases when water is uncovered, heated, and when
wind blows over it.
Three Stages of Water
 Ice,
liquid water, water vapor.
 Energy that is absorbed or released during a
change in state is called latent (hidden) heat,
a form of potential energy.
It is latent energy
because it does
not cause a change
in temperature.
Heat of Fusion
 When
the temperature of the ice reaches
0°C, it begins to melt.
As the ice changes to liquid, it absorbs 80
calories per gram.
The heat of fusion (the energy needed to melt
one gram of
ice is 80 cal/g).
The temperature of
the ice does not
change until all the
ice has melted.
Heat of Vaporization
When the temperature of the liquid water reaches
100°C, the boiling point of water, liquid water
changes to water vapor.
 The energy necessary to change one gram of a
substance from the liquid to the vapor state is
called the heat of vaporization.
The heat of vaporization
of water is 540 cal/g.
The gram of water absorbs
540 calories of latent heat
as it changes to vapor.
After all the liquid water
becomes vapor, the
temperature begins to
rise again.
Latent Heat Energy
 The
specific heat of water vapor is 0.5 cal/g°C.
 If the water vapor is cooled to 100°C, it will
condense and release the 540 calories of
latent heat it absorbed.
 As the cooling continues, the water will release
the heat it absorbed
while it was heated.
 It also releases the 80
calories per gram that
was needed to melt
the original ice.
Synoptic Weather Maps
weather map that shows a variety of
atmospheric field quantities.
 May show information about temperature, air
pressure, precipitation, and other weather
conditions at a
particular time and
over a large
geographic area.
Weather Station Symbols
Weather Station Symbols
Air Masses
 The
leading edges of air masses.
 When a front passes, precipitation often
accompanies the changes in temperature,
humidity, and atmospheric pressure.
 The character of an
air mass depends on
its geographic origin.
Weather Fronts
 Fronts
are shown by lines that separate two
air masses.
 Symbols along the fronts indicate the
direction the fronts are moving and what
kind of front they are.
 Stationary fronts are boundaries between
air masses that are not moving.
 Occluded fronts result from warm air being
pushed above the surface of Earth by
cooler air closing in from both sides.
Front Symbols
Natural Hazards
 Thunderstorms
Most occur in the summer when the air is warm
and moist.
Advancing cold fronts may push the warm air
upward, causing the formation of giant cumulus
clouds, and heavy precipitation.
Lightning, damaging hail, and
tornadoes are possible.
• Lightning strikes, flash floods
and tornadoes spawned by
thunderstorms cause about
100 fatalities per year in the US.
Natural Hazards
 Tornadoes
Most common in the spring and early summer
over the central US.
Are usually less than 0.3 miles (0.5 km) in
diameter and usually
last for 10 min or less.
Winds have been
measured by radar in
excess of 300 mi/hr.
Natural Hazards
 Hurricanes
Tropical depressions, areas of low pressure that
usually develop in the late summer and early
autumn in the Atlantic Ocean between South
America and Africa.
When winds exceed
74 mi/hr the designation
is changed from tropical
storm to a hurricane.
Tropical Storm Formation
Tropical Storm Categories
Wind Speed
Damage at
Storm Surge
Over 155

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