III. Winds & Fronts
http://www.youtube.com/watch?
v=8i3Zy4u4oxo
Winds
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Pressure
Gradient.
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What makes the wind blow?
All winds result from uneven heating
and pressure of the atmosphere.
Land heats faster than water.
Warm air over land expands and
becomes less dense (lower air
pressure).
Colder air rushes to fill in the lesser
pressure.
Winds always blow from high
pressure to lower.
The larger the difference between
the warm air (low air pressure) and
the colder air (higher pressure) the
stronger the winds. This pressure
difference is the pressure gradient
Air movements on the earth.
-Caused by a difference in air pressure due
to
unequal heating of the atmosphere.
1.
Two types of winds:
a. local
b. global
A. How wind develops:
Based on your knowledge about the pressure gradient ( the difference
between two pressure systems)which states would be susceptible to the
greatest wind speeds?
1. Heating the air, decreases pressure
(warm
air rises creating low pressure)
2. Cool air rushes into replace the warm air
(cooler dense air, produces high pressure)
3. As air goes from high to low pressure,
winds form.
B. Winds are created by….
1.
Sea breeze- warm air expands & rises
over land, & cool sea/lake air moves
toward the land.
C. Local Winds
2. Land breeze- warm air over water rises,
cool land air moves toward the water.
How would a Mountain Valley wind occur?
Winds occur on a larger
scale.
Read pages 556-558 Red text
Remember! Air rises over warm areas
and sinks over cold areas
Air rises in warm regions
where pressure is low
(convection)
ex the tropics
Air descends in cold areas
where pressure is high
(subsidence)
ex the poles
1. Don’t travel North and South because of the
Earth rotating on its axis.
a. 4 Types of Global Winds
– Doldrums: calm, warm winds at equator
– Trade Winds: 30° N&S of equator, gentle/sinking
air
– Prevailing Westerlies: 30-60° Strong (big
temp. diff.), impacts U.S. weather
– Polar Easterlies: 60-90° cold, weak winds from
poles
D. Global Winds
Polar Easterlies
c.
b.
Cool air descend
d.
Prevailing Westerlies
e.
Trade winds
f.
Doldrums
a.
e.
Trade winds
d.
Prevailing Westerlies
D. Global Winds
c.
Polar Easterlies
Warm air rises
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Coriolis
effect
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Here is how
it works.
Caused by earths rotation.
Felt by all objects, even air and ocean
currents, moving toward or away from
the equator.
 Suppose a rocket is fired from the North
Pole aimed directly at central Kansas.
Also that it will take the rocket an hour
to fly the distance.
 During that hour the earth will rote 15
degrees. So the rocket will land 15
degrees farther to the west. Aprox
1295 km away from the intended
target.
 Global winds have curved paths due
to earth’s rotation. This deflection
is called the CORIOLIS EFFECT.
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Coriolis Effect
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Wind and
Coriolis
The Coriolis effect deflects the
earth's winds.
 Air flows from high to low; the
C.e. turns the wind to the
right. The turning continues
until the C.e. exactly balances
the pressure gradient.
 In the northern hemisphere
the air flowing out from a high
turns to the right into a low
area which is receiving winds
blowing to the left or
counterclockwise.
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1. Pressure Gradient
Difference between the
High and low pressure
systems.. On a map
the highest winds will
occur were the isobars
are closest
2. The Coriolis effect
The tendency of an
object moving freely to
curve away from its
path of travel.
3. Friction.
Friction between the air
and the ground slows
surface winds.
Because the Cor. Effect
is weaker on slower
moving objects winds
are deflected less.
Factors that affect wind direction.
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Jet Stream- Happens 10
km up. Are bands of highspeed steady winds. Hundreds
of Km wide but very thin. Blow
generally from west to east.
200-400mph.
Complete the topic questions
from pg 558 Red text. 1-3 on a
separate sheet of paper
Honors only: Blue Text pg. 433
Crit. Thinking 13,15,16 and
Interpreting Maps 17-23
General global air masses
Two factors influence Global air
masses… Temp and Humidity.
Temperature
1. Air masses from N 50º latitude
POLAR (P)
2. Air masses from the tropics
TROPICAL (T)
F. North American Air Masses
Humidity
1. Air masses from over oceans
MARITIME (m)very humid.
2. Air masses from over land
CONTINENTAL (c) more dry.
North American Air Masses
2.
1.
cP
4.
mP
mP
3.
6.
5.
mT
cP
cT
Local Air Masses
7.
mT
Fronts.
G. Front
1. The Boundary between two different
air masses.
a. Water vapor drives storm
systems
Name: Cold Front
What’s happening: cold air replacing warm
air
Result: Lot’s of rain, cool temps,
thunderstorms, vertical cloud formation.
D. Types of Fronts
Name: Warm front
What’s happening: warm air replaces cold
air
Result: little rain/clouds, warmer temps.
Name: Stationary front
What’s happening: neither masses move
the other
Result: clouds & precipitation
Name: Occluded front
What’s happening: warm air mass caught
between cold air masses
Result: warm air cut off, cloudy & rain
 pg. 585 #’s 1-2 (red book)
 Sketch & color diagram 29.8
pg.
548 (black book)
 Pg. 555 do the critical thinking
Map.
 Front questions Blk Text pg. 549
#’s 6 and 7.
 Create, Draw & color a weather
Super Hero or Villain.
◦ Include your hero/villains powers and weaknesses
◦ Give your hero/villain a catchy name & costume
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