Basically – why and how the ocean and atmosphere MOVE!
There are many scales of
motion:
From
BIG to
very small
 Susan Howard
 Earth & Space Research
Today – I will just cover the basic
large scale, GLOBAL circulation.
www.ametsoc.org
The Ocean and Atmosphere
are in CONSTANT motion
NASA Movie: Perpetual Ocean
Model of ocean currents based on data from
satellites and other measurements.
NASA/Goddard Space Flight Center Scientific Visualization Studio
There are 2 main things that form the
Global Ocean and Atmospheric
circulation patterns
• Energy from the Sun
Warming from the sun Sets it in
Motion
• Rotation of the earth
The rotation directs the motion
 set up the climate system we know it.
Energy and the Sun
The Sun is constantly emitting energy, in the
form of “electrogmagnetic radiation”.
What is ELECTROMAGNETIC RADIATION?
•
•
•
•
•
Light
Infrared (Heat)
Xrays
Microwaves
Ultraviolet radiation (sunburns!)
Solar radiation travels
through space and hits the
earth and warms it.
The Heating of the Earth is Not Even!
UNEVEN HEATING: The daily amount of warming at a point on
the Earth depends on 3 things
Short length of day
Small angle of incidence/ low intensity
Large amounts of Ice cover
Noon in Antarctica
May 23rd, 2001
The Heating of the Earth is Not Even!
• Length of Day - How much sunlight a
point receives in a day
• Angle of Incidence (Intensity) – the angle
of the sunlight that reaches the earth
• Albedo – how much of this light is
reflected.
Length of Day
NH Summer
NH Winter
Source: Wikipedia
•
•
Earth is tilted with respect to Sun
Length of day changes throughout the year
Length of Day
Source: Wikipedia
Angle of Incidence
The angle the incoming light
makes with respect to the Earth
A beam of light shining straight down is more intense that
a beam of light shining at an angle
Angle of incidence
Wikipedia
Intensity of Radiation Varies with Latitude
The further you get
from equator, the less
radiation reaches the
earth per area
Source:
http://atschool.eduweb.co.uk/kingworc/departments/geography/nottingham/atmosphere/pages/solarradiationalevel.html
Because the Polar regions receive less radiation, they are cooler.
Because they are cooler – ice forms.
What does Sea Ice do?
It reflects the solar
radiation
High albedo – high reflection
Low albedo – high absorption
Radiation reflected
Radiation absorbed
Warms water
Ice cover – reflects radiation
So Ice makes the polar regions even cooler!
So, because of angle of incidence, length of day, & ice:
The Equator gets more heat than
the Poles ...
a lot more!
E
q
u
a
t
o
r
Warmer
Cooler
P
o
l
e
Average Annual Heating by Sun
Source: Wikipedia
Ocean temperature movie
From NOAA, Based on satellite measurements
What does this Uneven Heating do?
• Hot air and cold air behave differently
Hot air rises
Cold air will sink.
•
And this causes MOTION
How Wind Forms
Wind
Warm
air rises
Cold
air sinks
Convection Cell
Wind
Low
Pressure
High
Pressure
****Air likes to go from areas of High pressure to Low pressure
The GLOBAL Air Circulation is controlled by
these convection cells
Figure 7.5 in The Atmosphere, 8th edition,
Lutgens and Tarbuck, 8th edition, 2001.
So, we know:
1) The SUN heats the earth UNEVENLY – And this is
going to cause motion.
a. The uneven heating causes the rising and sinking of air
b. And this rising and sinking causes WIND.
c. The sun has set the atmosphere in motion
2) What going to now DIRECT this motion ?
ROTATION of the Earth
2) Rotation of the Earth
it helps DIRECT the circulation.
Coriolis Force
It works at right
angles to motion and
makes the motion
curve
Coriolis Force
Right in Northern Hemisphere
Equator
Left in Southern Hemisphere
Global Wind Patterns
With Rotation
No Rotation
http://www.srh.noaa.gov/jetstream/global/circ.htm
Global wind patterns
based on Solar heating and Rotation
Early Explorers relied on the global wind patterns to sail around the world
Summary Movie – Air circulation
Movie : Global Atmospheric Circulation
By Keith Meldahl, YouTube video
Sun’s Heating and Earth’s rotation create wind circulation
patterns
creates Global Surface Currents in Ocean
Wind motion creates Surface
Currents in Ocean
Map of basic surface currents
http://oceanmotion.org/html/background/wind-driven-surface.htm
Wind AND ocean currents
http://staff.orecity.k12.or.us/steve.tebor/atm%20currents/current/images/world_circulation.jpg
The Wind drives large scale surface currents
but that isn’t all.
Because of uneven heating, just like the
Atmosphere, the ocean also has Convection
Cells which drives DEEP circulation
Basic facts
Warm air rises
Warm WATER rises
Cold air sinks
Cold WATER sinks
Ocean Conveyer Belt
Ocean circulation – major currents
Movie : GFDL Ocean current move
Questions?