Transcript Global and Local Winds

Global and Local Winds
Air Movement
• Wind is the horizontal movement
of air from high pressure to low
pressure. It is caused by
differences in air pressure
• The greater the difference, the
faster the wind moves
Air Pressure
• Differences in air pressure are caused
by the uneven heating of Earth
• Cool, denser air with a higher
pressure flows underneath the warm,
less dense air. This forces the warm
air to rise.
1. Wind Vane- measures
2.
3.
4.
wind direction.- tells
you where the wind is
coming from. Ex: a
north wind comes
FROM the north.
Barometer- measures
air pressure
Anemometer- measures
wind speed.
Wind chill factor- the
increased cooling a
wind causes.
Wind Chill
• Why does a cool breeze feel refreshing in
the summer, but cold in the winter?
• Wind blowing over your skin removes
body heat. The stronger the wind, the
colder you feel.
Local Winds
• Generally move short distances
and can blow in any direction
• Caused by geographic features
that produce temperature
differences
a.Caused by the unequal heating
of Earth’s surface within a
small area.
a.It takes more energy to warm up
and cool down a body of water
than it does to warm up land.
b.Wherever the cool air is located,
that is the type of breeze. Ex:
sea breeze- cool air is over the
sea.
Sea Breezes
• High pressure is created over the
ocean (cooler air) during the day
and low pressure (warmer air)
over land due to uneven
heating
• Air moves from the ocean to the
land creating a sea breeze
A. Sea Breeze
1. Happens during the day.
2. Land warms up faster than the water.
3. Air over the land becomes warmer
than air over the water.
4. The warm air expands and rises,
creating a low-pressure area.
5. Cool air blows inland from over the
water and moves underneath the
warm air, causing a sea breeze.
6. Sea Breezes blow FROM THE SEA.
Sea Breeze
Land Breezes
• Low pressure occurs over the
ocean during the night and
high pressure over land due to
the uneven heating of earth
• This causes wind to move from
the land to the ocean creating
a land breeze
B. Land Breeze
1.Happens at night.
2. Land cools more quickly than water.
3. Air over the land becomes cooler than air
over the water.
4. Warmer air over the water expands and
rises.
5. Cooler air from land moves beneath it.
6. Land Breezes blow FROM THE LAND.
Land Breeze
Sea and Land Breeze animation
• http://www.classzone.com/books/earth_sc
ience/terc/content/visualizations/es1903/e
s1903page01.cfm
Question 1
•What causes winds?
Answer
•Winds are caused by the
uneven heating of
Earth’s surface, which
causes pressure
differences
Teach Time
• Teach your neighbor about land and sea
breezes.
Pressure Belts
• Uneven heating produces
pressure belts which occur
every 30° latitude
Pressure Belts
•As warm air rises at the
equator and moves toward
the poles, it cools
•As it cools, some of the air
sinks around 30° north
and south of the equator
Pressure Belts
•At the poles, cold air
sinks and moves
towards the equator
•Around 60° north and
south, the air begins to
heat up and rise
A. Coriolis Effect
1. As the winds blow, Earth rotates from
West to East underneath them, making it
seem as if winds are curving.
2. Global winds in N. Hemisphere turn
toward right.
3. S. Hemisphere, winds curve toward left.
Global Winds
•The combination of pressure
belts and the Coriolis Effect
cause global winds
•These are polar
easterlies, westerlies,
and trade winds
Global Winds
1. Winds that blow steadily from specific
directions over long distances.
2. Created by the unequal heating of Earth’s
surface.
3. Near the equator, sun’s rays strike earth
directly. Near the poles, sun’s rays do
not strike Earths’ surface directly.
4. The sun’s energy is spread out over a
larger area, so it heats the surface less.
Therefore, temps. Near the poles are
lower than near the equator.
5. Temp. differences btwn equator and poles
create giant convection currents, movements
of air between the equator and poles.
6. Warm air rises at the equator and cold air
sinks at the poles.
7. Air pressure tends to be lower near the
equator and greater near the poles.
8. Winds at the surface blow from poles
toward equator. High in the atmosphere,
air flows away from the equator toward the
poles.
9. They curve because of Earth’s rotation.
Polar Easterlies
•Wind belts that extend from
the poles to 60° latitude
•Formed from cold sinking air
moving from the poles
creating cold
temperatures
E. Polar Easterlies
1. Cold air near poles sinks and flow back
toward lower latitudes (away from the
poles).
2. Mixing of warm and cold air along the
polar front has major effect on weather
in US.
Westerlies
•Wind belts found between
30° and 60° latitude
•Flow towards the poles
from west to east carrying
moist air over the Unites
States
D. Prevailing Westerlies
1. mid-latitudes, btwn 30 and 60 North and
South, winds blow toward poles are
turned toward the east by Coriolis effect.
2. Winds blow west to east.
3. PLAY IMPORTANT ROLE IN
WEATHER IN USA.
Trade Winds
•Winds that blow from
30° almost to the
equator
•Called the trade winds
because of their use by
early sailors
C. Trade Winds
1. Cold air over horse latitudes causes high
pressure when it sinks.
2. High pressure causes surface winds to blow
toward equator and away from it.
3. Winds that blow toward equator are turned west
by Coriolis effect.
4. Winds are high and they help ships get across
the ocean.
5. In the Northern Hemisphere, they move from
the NE. In the Southern Hemisphere, they move
from the SE.
Doldrums
•Located along the
equator where no
winds blow because
the warm rising air
creates and area of low
pressure
A. Doldrums
1. Near equator, sun heats surface
strongly. Warm air rises, creating low
pressure.
2. Cool air moves into area, but is warmed
rapidly and rises before it moves very
far.
3. Little or no wind there (very calm)
B. Horse Latitudes
1. Warm air rises at equator and flows both
north and south.
2. At 30 degrees north and south, air stops
moving toward poles and sinks.
3. Calm air is here.
Horse Latitudes
• Occur at about 30° north and
south of the equator where
the winds are very weak
• Most deserts on the Earth are
located here because of the
dry air
Jet Stream
•The jet streams are
narrow belts of high
speed winds that blow
in the upper troposphere
and lower stratosphere
•Separates warm air
from cold air
F. Jet Streams
1.Bands of high-speed winds
about 10km above Earth’s
surface.
2.They are hundreds of km wide
but only a few km deep.
3.Jet streams blow from west to
east at speeds of 200-400km/hr.
Question 2
•What are the three types
of global winds?
Answer
•Polar Easterlies
•Westerlies
•Trade Winds
Question 3
•What is the difference
between a land breeze
and a sea breeze?
Answer
•Sea breezes occur during
the day when the land is
warmer than water and a
land breeze occurs at
night when the water is
warmer than land
Bill Nye
http://www.youtube.com/watch?v=JfeaCU2
y6t4 – Wind
http://www.youtube.com/watch?v=dz4fgG9
ZCIc - Atmosphere
Mr. Parr Winds Blow
• http://www.youtube.com/watch?v=g4O9z
_R5ZSc