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Winds
What is wind?
• Answer:
Winds are caused by
differences in air
pressure.
What causes wind?
• Answer:
Most differences in air
pressure (wind) are caused
by the unequal heating of
the atmosphere.
What causes the most differences
in air pressure that causes wind?
• Answer:
Convection currents form when an area of
Earth’s surface is hearted by the sun’s rays. Air
over the heated surface expands and becomes
less dense. As the air becomes less dense, its
air pressure decreases. If a nearby area is not
heated as much, the air above the less-heated
area will be cooler and denser. The cool, dense
air with a higher pressure flows underneath the
warm, less dense air. This forces the warm air
to rise.
How are winds described?
• Answer:
Winds are described by
their direction and speed.
How are winds named?
• Answer:
The name of a wind tells you where the wind
is coming from.
For example: a south wind blows from the
south toward the north. A north wind
blows to the south.
Watch the demonstration
• The fan is the wind source (dah!)
• The wind vane is the straw arrow.
– The “tail” is larger than the point
• Note that when the wind blows, the point is
in the wind, indicating the direction FROM
which the wind is blowing.
What is an anemometer?
• Answer:
• An instrument used to measure wind
speed.
What is a wind vane?
• Answer:
An instrument to determine wind direction.
The wind swings the wind vane so that
one end points INTO the wind.
What is “wind-chill factor?”
• Answer:
The increased cooling a wind can
cause. The wind blowing over
your skin removes body heat.
The stronger the wind, the colder
you feel.
Local winds
• Answer:
Local winds are the winds that blow over
short distances. They are caused by the
unequal heating of Earth’s surface within a
small area. They only form when large
scale winds are weak.
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Warm air over land rises
Sea Breeze moves inland
Clouds develop aloft and move seaward
Upper level return land breeze
Cool air aloft sinks over water
Sea Breeze blows over the land
1.
Cool air over land sinks
2. Land Breeze moves out over water
3. Relatively warmer water heats air which then rises
4. Upper level return sea breeze
5. Cool air over land sinks
What are global winds?
• Answer:
The winds that blow steadily from specific
directions over long distances.
How are global winds like local
winds? How are they different?
• Answer:
Like local winds, global winds are
created by the unequal heating of
Earth’s surface. But unlike local
winds, global winds occur over a
large area.
How do global winds develop?
• Answer:
Temperature difference between the equator and
the poles produce giant convection currents in
the atmosphere. Warm air rises at the equator,
and cold air sinks at the poles. Therefore air
pressure tends to be lower near the equator and
greater near the poles. This difference in
pressure causes winds at Earth’s surface to
blow from the poles toward the equator. Higher
in the atmosphere, however, air flows away from
the equator toward the poles. Those air
movements produce global winds.
What is the Coriolis Effect?
• The way Earth’s rotation makes winds
curve is called the Coriolis effect.
HW: Draw the Global Winds in your NB.