Transcript 13.6 Wind and Ocean Currents

13.6 Wind and Ocean
Currents
Science 10
Wind
Wind Patterns
A Little Background …

Atmospheric Pressure is the force
of the air pressing down on the
earth’s surface
◦ Atmospheric pressure is measured
using a barometer.
◦ Since air molecules are so spread out
(lots of empty space), we don’t feel
the pressure they exert

Differences in air pressure help
cause winds and affect air masses.
They are also factors in the
formation of storms such as
thunderstorms, tornadoes and
hurricanes.
What is Wind?
Wind is a movement of air in the atmosphere
How Wind Develops
 Caused by a difference in air pressure due to unequal
heating of the atmosphere.
Question:

Where on the planet does the surface get heated more
than other areas?
 At the Earth’s surface, wind always blows from areas of
high pressure to areas of low pressure
How are Winds Created?
Winds are created by….
1. Heating the air, decreases pressure (warm air rises
creating a low pressure)
↓
2. Cool air rushes in to replace the warm air(cooler dense
air, produces high pressure)
↓
3. As air goes from high to low pressure winds form
This is a CONVECTION style… Convection Current
Make your own ‘How are Winds Created?’ Graphic
Classifying Winds
I. Localized
affect only small areas
Types of Local Winds
 Sea Breezes- from sea to land
 Land Breezes- from land to sea
II. Prevailing winds
affect large areas, types to follow..
Which one do you think affects us more?...
Coriolis Effect & Causes of
Prevailing Winds Jigsaw

First: become an expert (5-10 minutes)
◦ Read notes/text
◦ Discuss within your group
◦ Determine how to teach others (as a group)

Next: switch with another group (A-D, BE, C-F) and teach each other
◦ Take turns teaching content
◦ Take notes on Coriolis effect / causes of
prevailing winds
The Coriolis Effect
Earth’s rotation causes anything that
moves LONG DISTANCES, such as
prevailing winds, to APPEAR to change
directions.
 The apparent change in direction of a
moving object in a rotating system is
called the CORIOLIS EFFECT.
Demo Video

Coriolis cont…
Evident on the Earth because as Earth rotates
eastward, an object travelling from north to
south will appear to move to the right
 In the southern hemisphere objects moving
from the pole appear to move to the left
 The Coriolis effect is more predominant closer
to the poles


Let’s look at this effect on the globe
Causes of Prevailing Winds
Due to a combination of convection
currents and coriolis effect
 air at the equator is warmed and
rises, forming a convection current called
the equatorial convection current

Effects of Prevailing Winds
Help distribute large amounts of solar
energy from the equator to the colder
parts of the world.
 Also carry moisture, causing a variety of
precipitation (snow, rain, etc…)

Prevailing Wind Terms:
Polar easterlies – occur between 60 degrees
latitude and the poles and moves east to west
 Mid-latitude westerlies – occurs between 30
degrees and 60 degrees latitude and move from
west to east
 Northeast trade winds – occur just north of
the equator and move east to west
 Southeast trade winds – occur just south of
the equator and move east to west


Label these on your map
Wind terms cont…
•
•
•
Gusts – occur because of a rapid air
pressure change and move in no fixed
direction
Squalls – gusts accompanied by rain
Wind speed indicator –
anemometer/weather vane
So…
Do you think the Coriolis
Effect and Wind affect how
water moves in the ocean?
-Take 1 min to discuss with a
student at your table, I will get
feedback from some of you!
Ocean Currents
Ocean Currents
• Mass
movement or flow of
ocean water
• River within the ocean
• Two types
–Surface and Deep
Surface Current
 Horizontal, stream-like
movements
of water that occur at or near the
surface of the ocean
 Can reach depths of several hundred
meters
Surface Current Animation
Surface Currents

Controlled by three factors
◦ Prevailing winds = Cause surface
currents to flow in the direction the
wind is blowing
◦ Coriolis Effect
◦ Continental Deflections = shape of
the land it flows up against
Deep Currents


Stream like movement of ocean water far
below the surface. THIS IS WAY DOWN
THERE!
Caused by changes in density
◦ Change in temperature
◦ Change in salinity (Salt in the water)
Causes, broken down…
Change in temperature
◦ Decreasing the temperature of water increases density (water
sinks… remember demo?)
 Change in salinity
◦ Increasing the salinity of water increases density (again, making
water sink)

Both of the above causes warmer less dense water from the equator
moves to replace it (water will always want to be level and that is
why the water that leaves gets replaced)
The Pic on the next page does a good job explaining this
phenomena…
Text (page 519 #1-4, 521 #1-2)
1.
2.
a) Northward b) northward c) to the right
A) the southeast trade winds: solar energy strikes
most directly near the equator. This causes the
land, water and air there to heat. The hot air
rises and moves southward to about 30oS
latitude. The rising moist air is replaced by the
cooler, drier air (convention current). At the
same time, the Coriolis effect causes the winds to
twist to the left. This results in the southeast
trade winds
2B mid-latitude westerlies: at 30oS, some
of the cool, decending air joins with the
mid-latitude convection currents to flow
southward. These winds also twist to the
left, causing the mid-latitude westerlies
 2C Polar easterlies: cold, dense air flows
northward from the area around the
south pole. It also twists to the left,
causing the polar easterlies


2D Southern Hemisphere jet streams:
caused by pressure differences at the
upper levels of the atmosphere. Air
pushed from the equator to 30oS twists
leftward, causing an upper airflow to the
east.

3. Along which latitude in the Southern Hemisphere are
deserts likely to be found? Explain why this happens.
◦ Most likely to be found at 30oS latitude – this is
because the air descending from the convection
currents is cool and dry
◦ Southern hemisphere deserts:Victoria and Gibson
deserts (Australia); Namib desert (Namibia)
4. You would fly high enough to join the jet stream
because it travels from west to east at a high speed
and would help the plane fly faster