wind and air circulation
DESCRIPTION
Wind and Air Circulation. Wind is the horizontal movement of air parallel to Earth’s surface. Wind is caused by differences in air pressure – which in turn is caused by changes in atmospheric conditions (Ex: water vapor, temperature, etc…). - PowerPoint PPT PresentationTRANSCRIPT
Wind and Air Circulation
Wind is the horizontal movement of air parallel to Earth’s surface.
An anemometer is an instrument that measures wind speed.
Wind is caused by differences in air pressure – which in turn is caused by changes in atmospheric
conditions (Ex: water vapor, temperature, etc…)
Air pressure gradient is the difference in air pressure over a specific distance.
An isobaric map illustrates the pressure gradient of an area.
When the air pressure gradient is steep, the
isobars are close together.
HIGH WINDS
When the air pressure gradient is gentle, the isobars are further apart.
LOW WINDS or NO WINDS
Wind DirectionWinds moves from areas of high
pressure to areas of low pressure.
Due to the Coriolis Effect, the wind direction is deflected to the
right in the Northern Hemisphere and to the left in the Southern Hemisphere.
A weather vane (wind vane) is an instrument that determines the
direction of wind.
The weather vane will point in the direction that the wind is coming from.
The wind is coming from the northwest and is blowing to the southeast.
Convection CellsThe atmosphere is
heated by insolation. Due to the changes in intensity and duration of insolation, unequal
heating leads to difference in air
pressure.
This will lead to the creation of
convection cells – the rising of warm/less dense air and the
descending of cool/more dense air.
Regions where air comes together to
form a vertical current is called convergence.
Regions where air spreads away from a
vertical current is called divergence.
convergence
divergence
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A jet stream is a strong, easterly flowing wind found in the upper troposphere. Jet streams influence the formation and direction of weather patterns.
Jet Stream
Jet Stream
Jet streams help to steer
air masses and fronts.
Planetary Winds and Pressure Belts
How do the winds seem to blow?
Winds blow towards low pressure.
Winds blow away from high pressure.
L H
Planetary Winds and Pressure Belts
High Pressure
Low Pressure
Due to the Coriolis Effect, winds that move
away from a high pressure belts are
deflected to the right in the Northern Hemisphere.
These winds would be deflected to the left in
the Southern Hemisphere.
These are known as planetary winds.
Pressure Belts
Planetary Winds
Planetary Winds and Pressure Belts
The position of Earth’s pressure belts and the
planetray winds that are created will change as different points of the
Earth are exposed to direct insolation during Earth’s
revolution around the Sun.
As a result, different locations on Earth’s
surface will experience seasonal shifts in weather
patterns.
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Weather Movement in the United States Generally speaking, weather patterns
move from the southwest to the northeast in the US due to the
southwest prevailing winds.
Surface Ocean Currents
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Surface ocean currents are caused by wind blowing over the oceans
thus transferring energy to it.
The direction of movement of these ocean currents is a
reflection of the Coriolis Effect (clockwise in
Northern Hemisphere and counterclockwise in Southern Hemisphere) and the landmasses
surrounding the oceans.
As is true of prevailing winds, the positions of surface ocean currents will change seasonally
due to different areas of Earth’s surface receiving maximum insolation as Earth revolves around
the Sun.
Weather Station Model
Wind Direction
The wind blows along the shaft.
The wind originates from the southwest and has a speed of
15 knots at this location.
Wind Speed
Whole feather = 10 knots
Half Feather = 5 knots
1 knot = 1.15 mi/hr