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Winds
Atmospheric Circulation Ch22.3 p561
Wind is horizontal air movement
Three causes of motion
1.
Convection
Pressure
Differences
3. Coriolis
Effect
2.
Convection Currents
Warm air rises
and cool air
sinks because
of density
 This
is called a
convection
current
Winds are caused by the uneven
heating of Earth’s surface.
 Land
heats up
and cools off
quicker than
water
 So the large
amount of water
on Earth
moderates our
temperatures
2. Pressure Differences
pressure differences
in the atmosphere that are a result of
temperature differences
WIND ALWAYS FLOWS
3. Coriolis Effect
The deflection of
objects to the
right in the
northern
hemisphere—
called the Coriolis
Effect
 Due
to rotation of
the earth
 effect
greatest
at poles,
decrease to
zero at equator
Coriolis Effect
Global Circulation Patterns
 Global
winds are
the result of
several cell-like
circulation
patterns brought
about by


uneven heating of
Earth’s surface
and compounded
by effects of the
Earth’s rotation.
Doldrums or ITCZ

At the equator hot
air rises and forms
an area known as
the doldrums
 At the boundary
between the
troposphere and
stratosphere it
spreads out to the
N or S
ITCZ—Intercontinental convergence zone
Horse latitudes

As it reaches
about 30 N and S
of the equator it
cools and
descends
 Sinking air causes
an area of dry
weather
 The sinking air
also causes an
area with weak
winds
 This caused
problems for ships
Trade Winds

Winds flowing south
from the horse
latitudes is deflected
to the west in the
northern
hemisphere
 These aided trading
by ship
Jet Stream

Jet streams are fast flowing, relatively
narrow air currents found in the atmosphere
at around 11 kilometers (36,000 ft) above the
surface of the Earth, just under the
tropopause.
 They form at the boundaries of adjacent air
masses with significant differences in
temperature, such as of the polar region and
the warmer air to the south.
Current jet stream data
Highs and Lows?

Winds circle
Clockwise and
out around a high
 Highs generally
mean cold dry air
that is sinking
 High pressure
usually = fair
weather
Low Pressure Systems

Winds circle
counterclockwise
and into a low


Warmer air rises and
cools and forms clouds
and precipitation
Low pressure usually =
rainy weather
Explore

Draw an H in the middle of your paper Draw a
1 inch circle lightly around the H.
 Place all five fingers inside the circle using
your left-hand if right handed and your right if
left-handed.
 Standing up if necessary, turn your hand
slowly clockwise and gradually spread your
fingers and thumb our as your hand turns.
Don’t move the map. You hand will end up flat
on the paper.

Bring your fingers back inside the circle.
 Number the starting position of each finger
and thumb with your thumb as number 1,
index finger 2, and so on.
 Slowly rotate your hand clockwise and
gradually spread out your fingers and thumb,
stopping after about one inch of motion.
Number the position of each finger again.
 Continue spreading and numbering every
inch or so, until your hand is completely flat
on the paper.
 Connect each number in a smooth arch,
Place arrows at the end of each arch. The
result should be a spiral pattern, typical of a
high pressure system.
Explore Low

Draw an L in the middle of your paper Draw a
1 inch circle lightly around the L.
 Place your non-writing hand, palm down on
the circle. Rotate your hand
counterclockwise, bring your thumb and
fingers up into the circle. Practice this twisting
motion without moving the paper.
 Place your palm down again, and number the
position of each finger and thumb, with the
thumb as one.

Slowly rotate counterclockwise and gradually
bring in your fingers and thumb, numbering
the position of the position of each finger after
about one inch of motion
 Connect each number in a smooth arch,
ending with an arrow pointed toward the
L. This pattern is typical of a low pressure
system.
Wind always blows from high to low
Local Wind Patterns
 Monsoons
 Land
breeze/Sea breeze
 Chinook
Monsoon
In winter, air flow is
from cooler (H
pressure) to warmer
(L pressure) ocean


Air from the land is dry
Dry season
In summer, air flow is
reversed


Air flows from the cooler
ocean to the hotter (L
pressure) land
Wet season
Sea Breeze

During the day land heats faster than the
water. The hot less dense air rises and cooler
air from the sea rushes in to take its place.
Land breeze
Since the air over land cools more rapidly than the
air over water, a temperature difference is
established, with cooler air present over land and
relatively warmer air located over water.
Chinook

A wind on the
eastern side of the
Rockies formed
when air descends
and is compressed
and warms
Effects:
 Rapid. Large
Temperature
Changes Can Occur
 Snow may melt or
evaporate through
sublimation
 Loss of moisture
due to significant
drops in humidity
Beaufort scale

Used to estimate
wind speeds
 Originally used by
sailors
Beaufort Scale on Water
Beaufort Scale on Land
Wind Energy
Wind and Pressure
Relationship Lab
Remember Topographic
Maps?
Contours are imaginary lines
that join points of equal
elevation on the surface of
the land
Now we will use these with
equal temperature and
pressure
Same Concept—Different Use
Isotherm=equ
al temperature
Isobar=equal
barometric
pressure
contour interval (CI)
1.
The contour intervals
vary
2.
Isobars often have
an interval of 4
3.
Read the directions or
look at examples to
see the contour level
Tips for understanding
contour lines.
 There
are a few rules that topographic
contours must obey, however, and once
you understand these rules the map
becomes an extremely useful and easy
to use tool.
1) Every point on a contour line
represents the exact same temperature
or pressure

As a result of this every contour line must
eventually close on itself to form an irregular
circle
 Contour lines on the edge of a map do not
appear to close on themselves because they
run into the edge of the map, but if you got
the adjacent map you would find that,
eventually, the contour will close on itself.
2) Contour lines can never
cross one another.
 Each
line represents a separate
temperature or pressure and you can’t
have two different temps or pressures at
the same point.
3)Points shown are reporting stations

There may be areas that do not report or have no
station
4) The closer contour lines are to one
another, the higher the wind speed.

Where is the
wind speed
high?
Where is it
low?
5) Inside a series of closed contours (the contours
make a circle) is a High
or Low pressure