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Global Weather
Dynamics
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• Definition of Weather Dynamics
• Weather Climate
• Transfer of Energy
• Conduction
• Convection Advection
• Radiation
• Reflection/Absorption
• Atmosphere Atmospheric Pressure
• Prevailing Wind Patterns
• Hydrosphere
• Water Cycle
• Major Ocean Currents
• Clouds and Fog

In this tutorial we will cover the basics of
Weather Dynamics.
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Weather Dynamics
Weather dynamics is the study of how the motion
of water and air causes weather patterns.

• Important notes about weather dynamics
• Things are always in motion.
• The Earths energy is always balanced.
• The suns energy sets water and air in motion.

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The difference between Weather Climate
Before we go any further, you must understand the
difference between Weather Climate.
Weather is

• The set of environmental conditions encountered
  from day to day.

Climate is

• The set of environmental conditions averaged
  over many years.

Example Lets say Ganders weather in January
is cloudy with temperatures of -18ºC. But
the climate for this time of year -9 ºC and
flurries of snow.
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The Transfer of Energy

• Conduction
• Conduction is the transfer of energy through the
  collision of particles (vibration). It occurs
  most easily in metal, and to a small extent in
  rock.

• Convection Advection
• Convection Advection are the transfer of energy
  by the movement of particles in a fluid (such as
  water) or gas (such as the components of the
  atmosphere).
• Convection transfers energy vertically
  advection transfers energy horizontally.

• Radiaton
• Radiation is the transfer of energy by means of
  waves. Radiation does not require a medium so it
  can travel through space.
• Different kinds of radiation are
• Infrared radiation
• Ultraviolet waves
• X-rays
• Gamma rays

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• Reflection/Absorption
• Reflection is the redirection of energy when it
  hits a surface.
• Things with a high albedo relfect things easier,
  so the higher the albedo the larger the portion
  of energy it reflects. So, if the albedo is
  lower, than less energy is reflected.
• An exemple of reflective surfaces is
• Clean snow

• Reflection/Absorption
• Absorption is when energy is taken into a surface
  when it hits it.
• Any material that absorbs energy and becomes
  warmer is called a heat sink.
• An exemple of absorption is
• Black soil

An example of reflection absorption
This picture shows waves of light from the sun
being absorbed and reflected by the Earth.
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The Atmosphere Atmopsheric Pressure
The atmosphere consists of many layers
The atmosphere is the blanket of air and moisture
that surrounds the Earth. Most dense at sea
level, where the molecules are pressed together
by the weight of the air above, the atmosphere
becomes less dense as the molecules, and the
vacuum of space begins. The atmosphere is
comprised of 78 Nitrogen, 21 Oxygen, 1
other gases (argon, carbon dioxide, neon, helium,
krypton, hydrogen, ozone).
Atmospheric pressure is the pressure the Earth
exerts as gravity pulls it towards the centre of
the Earth, it is greatest at sea level, where the
molecules are closest together. At higher
altitudes atmospheric pressure decreases. Atmosph
eric pressure is measured in Kilopascals (kPa).
1 kPa is equal to 1,000 Pa. Atmospheric
pressure is measured with the aneroid barometer.
Here are the five main layers -
Troposphere - Stratosphere - Mesosphere -
Thermosphere - Exosphere
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Prevailing Wind Patterns
The Coriolis effect occurs when things that move
long distances appear to change direction, due to
the Earths rotation.
Prevailing winds are caused by a combination of
convection currents and Earth s eastward
rotation. Prevailing winds help to distribute
large amounts of solar energy from the equator to
the colder parts of the world. Prevailing winds
also carry moisture, helping to cause a variaty
of precipitaion such as snow and rain.
Some winds are local or regional, which means
they are very small. But major wind patterns
cover much larger areas. Winds that affect large
areas are called prevailing winds.
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This map shows the major large-scale of
prevailing winds.
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The Hydrosphere
All of the Earth s water (fresh and salt) form
what is called the Hydrosphere. Approximately
70 of the Earths surface is water.
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The Water Cycle
Because so much of the Earths surface is covered
by water, our weather system depends greatly on
water in its three states (solid, liquid, gas
vapour). Energy, mostly from the sun, causes
water to evaporate or ice to sublimate. The
invisible water rises, and eventually, as the
pressure and temperature decrease, this vapour
condences into fog, mist clouds.
This picture shows the water cycle
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Major Ocean Currents
As you have seen, oceans are particularly
important in weather dynamics. One reason is
that they occupy so much of the Earths surface.
This map illustrates the world ocean currents.
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• Causes of Ocean Currents
• Since there is a vast volume of water at the
  equator, where the radiation of the sun is
  direct. Since warm water is less dense than cold
  water, the warm water moves northward or
  southward at the surface, and is replaced by cold
  water from below, starting a convection current.

• Effects of Ocean Currents
• Ocean currents are responsible for coastal
  regions being cooler in summer and warmer in
  winter, than regions several kilometres inland.
  Large bodies of water and their currents moderate
  the climate. Ocean currents also affect the
  pressure of the air above them.

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Clouds and Fogs
How do clouds form?

• Convective Clouds
• Convective clouds are produced when air near the
  ground absorbs energy from heated surfaces,
  becomes warmer and less dense, and rises into the
  atmosphere carrying vapour with it. As the
  pressure gets lower, it expands and cools because
  the particules lose energy as they get farther
  apart. The water vapour cools until it forms
  clouds.

• Frontal Clouds
• Frontal clouds form when the front of a large
  moving air mass meets another air mass at a
  different temperature. The warmer air mass moves
  over the cooler one and the warm air rises, then
  cools down and forms clouds.

• Orographic Clouds
• Orographic clouds form when air moves up a
  mountain expands at the lower pressure, and
  cools. Moisture in this rising air condences in
  the colder air as it goes up the mountain,
  producing clouds.

• Fog
• Fog is actually a cloud that forms near the
  ground. The most common form of fog is produced
  on clear nights when energy from the surface
  radiates upwards but is not reflected back to
  earth by any cloud. Thus, the air near the
  ground cools, allowing water vapour to condence
  into fog.

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Classifying Clouds

• Cumulus Clouds
• Cumulus clouds have a billowing, rounded shape.
  These clouds, which tend to grow vertically,
  usually indicate instable weather.

• Stratus Clouds
• Stratus clouds are flattened, layered shapes.
  These tend to grow horizontally, indicate stable
  conditions.

• Classifications
• Alto Medium-level clouds
• Cirrus High-level clouds
• Nimbus Rain-holding clouds

This diagram shows the different types of clouds
and their levels of altitude.
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And this concludes our tutorial.
All pictures information for this tutorial can
be found in the Nelson Science 10 Textbook.