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Weather Dynamics
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The study of how the motion of
water and air cause weather
patterns.
The main components of Earth that
affect weather are the atmosphere,
the land forms, and the various
forms of water (solid, liquid, and
gas).
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Weather – the set of environmental
conditions encountered from one
day to the next.
Climate – the set of environmental
conditions averaged over many
years.
Example of a weather description:
“It’s raining today.”
Example of a climate description: “It
often rains in October.”
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Longitude: the angle measured east or west of
the 0o line, which passes through Greenwich,
England. Lines of longitude run from pole to
pole.
Latitude: the measured north or south of the
equator .
Equatorial Region: area between the Tropics of
Cancer and Capricorn
Polar Regions: areas north of the Arctic Circle
and south of the Antarctic Circle.
Mid-latitude Regions: areas between the
tropics and polar regions.
Methods of heat
transfer that distribute
energy around the
Earth:
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The transfer of energy by waves.
Radiation does not require a
medium.
Visible light is only one member of
the electromagnetic spectrum.
Some other waves from this
spectrum include microwaves, Xrays, infrared waves, etc.
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The transfer of energy through the
collision of particles.
E.g. frying pan
Some materials are better
conductors of heat than others.
E.g. Metals conduct heat better than
rock or sand.
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The transfer of energy vertically by
movement of particles in a fluid.
(water or atmosphere)
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The transfer of energy horizontally
by movement of particles in a fluid.
(water or atmosphere)
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The Sun is Earth’s main source of
electromagnetic radiation.
Not all solar energy reaching Earth’s
atmosphere actually reaches the planet.
Much is reflected back into space. (fig. 4,
pg. 506)
A certain amount is also reflected from
the Earth’s surface, depending on the
surface features.
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The albedo (ability to reflect light) of a
material will determine the amount of
energy reflected.
clean snow – high albedo
black soil – low albedo
Any material that absorbs a high
percentage of radiant energy is called a
heat sink. (e.g. oceans) Substances that
make good heat sinks have high heat
capacities.
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The measure of how much heat one
gram of a substance requires to raise
its temperature by 1o Celsius.
(Fig. 5, pg. 506 )
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The term “latent” means hidden. When a
substance changes state, it absorbs or
releases energy without changing
temperature.
Latent Heat of Fusion (Melting) – the
amount of heat energy required to change a
unit mass of a substance from a solid to a
liquid.
Latent Heat of Vaporization – the amount
of heat energy required to change a unit
mass of a substance from a liquid to a gas.
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Consists of air and moisture that
surrounds the Earth.
Common atmospheric gases: oxygen
(21%), nitrogen (78%), carbon dioxide,
ozone and water vapor.
Density depends on height above sea
level.(most dense at sea level)
Altitude is height above sea level.
The atmosphere is thickest above the
equator – warmer air takes up more
space because it expands (less dense).
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The atmosphere has a number of layers,
each with its own properties
As the altitude above Earth proceeds, we
move into different layers.
The Layers of The
Atmosphere:
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Layer closest to the Earth’s surface; it
extends to an altitude of about 16 km at
the equator and about 8 km at the poles.
Contains most of the atmosphere’s
moisture, and most of our weather
systems/patterns.
As the altitude increases in the
troposphere, the temperature decreases
6oC per km.
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Very thin layer that separates the
troposphere from the stratosphere.
The temperature increases due to the
slightly greater amount of ozone present.
Ozone absorbs more ultraviolet radiation
causing the temperature increase.
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Contains very little moisture and extends
for some 50 km.
It exists from about 12-60 km of altitude
above Earth’s surface.
It is a warm layer as it contains more
ozone than any other layer, and protects
the Earth from UV radiation.
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This is the middle layer. (meso means
middle)
Similar concentration to other layers
with the exception of ozone and water
vapor.
Very cold, with temperatures reaching
as low as -75oC.
Layer extends from about 50 to 80 km.
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Temperature is much higher. (avg. ~
30oC)
Higher temperature is due to x-ray
absorption.
The radiation causes this layer to
become ionized, which produces the
aurora borealis (northern lights).
Layer extends from 80 to ~500 km.
Very thin outer layer of very little
atmosphere.
 Most common element is
hydrogen.
 Temp. is extremely cold, and is
often considered part of outer
space.
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The change in temperature over
a distance.
 The troposphere has a
temperature gradient of -60 C per
1000 m or 1 km(vertical distance
upward)
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Pressure changes across a set
distance. A pressure gradient can be
vertical or horizontal.
Closed lines on a weather map can
indicate a pressure gradient. To
show a high pressure gradient
(resulting in high winds), lines are
bunched together.
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The pressure the air exerts as gravity pulls it
toward the Earth. Atmospheric pressure is
greatest at sea level where the air molecules are
closer together.
Atmospheric pressure generally decreases with
altitude but falling/rising air will also affect
atmospheric pressure. Atmospheric pressure is
measured in kilopascals. (See text p.512, fig
4(a)) The average atmospheric pressure at sea
level is 100kPa.
Complete # 2, 3, 4, 5, and 6 on pg. 513.
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Wind is a movement of air in the
atmosphere.
Prevailing winds affect large areas/weather
around the world.
They are a result of:
- differences in temperature /pressure from
the equator to the poles, causing air to move
- rotation of the Earth
The apparent change in direction of a
moving mass in a rotating system is called
the Coriolis Effect.
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Cold, dense air near the poles sinks
and moves towards the equator.
Due to the Earth’s rotation
(Coriolis), this air twists to the right
in the Northern Hemisphere. (left in
the S. Hem.)
The resulting winds are Easterlies.
Polar
Easterlies
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Convection currents occur from the
equator to ~ 30o latitude.
Some of this warm air meets cold polar
air and low pressure forms at ~ 60o
latitude.
Surface air moving north turns to the
right (left in the south).
The resulting winds are Westerlies.
Mid-Latitude
Westerlies
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Air from equatorial convection currents
sinks at ~ 30o latitude and moves back
toward the low pressure at the equator.
This air twists to the right in the
N.Hemisphere forming the NE Trade
Winds.
This air twists to the left in the
S.Hemisphere forming the SE Trade
Winds.
NE Trade
Winds
SE Trade
Winds
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These are high speed winds in the upper
troposphere near the middle latitudes.
The air pressure within the troposphere is
greatest near the equator because the layer is
thicker at the equator.
The high pressure air will move toward the
poles, turning right in the N.Hemisphere.
(left in the S.Hemisphere)
As a result, jet streams always flow west to
east.
***Jet streams constantly shift latitude as they
separate tropical and polar air masses.
Jet
Streams
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The Earth revolves in its orbit around the
Sun.
Though undetectable, the Earth moves
nearly 30 km/s in its orbit.
The Earth rotates on its axis (W  E);
one full rotation every 24 hours.
The Earth is tilted on its axis (23.5o)
ALL of these factors produce seasons that
are opposite in the Northern and
Southern Hemispheres.
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The Earth’s orbit is elliptical, so we are not
always the same distance from the Sun.
The Earth is actually closest to the Sun
during our winter solstice, and farthest from
the Sun during our summer solstice.
The orientation (tilt) of the Earth causes the
Sun’s rays to strike the surface at different
angles.
The angle of incidence affects the amount of
energy transferred.
-Winter Solstice
- shortest day of the year
- N. Hem. is at its max tilt away from Sun
- Sun’s rays are at it’s steepest angle
Vernal Equinox
-Summer Solstice
- longest day of year
-N. Hem is at it’s max tilt towards the Sun
Autumnal Equinox
Complete # 1-3 on pg 509.
 And # 1 and 2 on pg 519.
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THE HYDROSPHERE
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The hydrosphere consists of all the water
(salt and fresh) on Earth.
~ 70% of the Earth’s surface is water.
Only 2.5 % of all water is fresh.
Of all the fresh water on Earth, over 87%
is ice (glaciers and polar caps).
Over 12% of fresh water is under ground
(i.e. groundwater).
Very little usable fresh water exists. (only
0.4% of fresh water is on the surface or in
the atmosphere)
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Evaporation: surface water (lakes, ponds,
etc.) changing to water vapor in the air.
Sublimation: ice changing to water vapor.
Transpiration: water leaving plants as
water vapor into the air.
Condensation: water vapor becoming
liquid.
Precipitation: water that falls to Earth as
a liquid or solid.
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Radiant energy from the Sun causes
surface water to evaporate, and ice to
sublimate.
Transpiration from plants adds to the
water vapor in the air.
Water vapor rises, cools, and condenses
into clouds and fog.
Precipitation (rain, snow, etc.) falls from
the clouds , and the process repeats.
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Draw a fully labeled illustration
of the water cycle.
MAJOR OCEAN
CURRENTS
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Oceans have a huge affect on weather
dynamics.
They occupy a large portion of the Earth’s
surface. Water’s high heat capacity will affect
temperature and temp. changes in a given
area.
There is a vast amount of water at the equator
where the sun is most direct. Ocean currents
act as conveyor belts to transport energy
around the world.
See p. 525, Fig. 1. Note that the
directions/flow of major ocean currents are
similar to that of the prevailing winds.
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(i) Solar heating of the oceans near the equator
results in convection currents.
(ii) Continents redirect water to move along
their edge.
(iii) Earth’s rotation (eastward) has influence.
Currents on the east side of oceans tend to be
fast; west side currents are usually wider and
slower.
(iv) Salt content has an influence.
Evaporation causes sea water to become
saltier and sink – results in convection
currents.
“A Tale of Two Islands”
Worksheet
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Complete the following Questions:
Page 527, # 1, 2, 3, and 5.
CLOUDS
Clouds are formed when warm,
moist air rises. It then cools at
elevation and condenses into tiny
water droplets (or ice particles)
on dust particles.
 There are 3 categories of clouds
based on formation:
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Formed when a land mass is heated.
Warmed air rises, cools, and condenses.
Often develop where sea breezes occur.
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Form at the frontal zone where two large air
masses meet.
The warmer mass is forced up over the cooler
mass.
As it rises, it cools and condenses into clouds.
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Formed when air is forced to rise up
a mountain.
As it nears the top, it cools and
condenses into clouds.
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Cloud type that forms near the ground.
Forms when warm, moist air moves over a colder
surface. (e.g. ocean)
Cool surface causes the warm air to cool and
condense at ground level.
2 Main Groups:
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Lumpy or “pillowy” clouds that result when strong
upward motions exist in the atmosphere.
Grow vertically.
They indicate that the atmosphere is unstable, and
are usually associated with stormy or severe weather.
Can form by all 3 formation types.
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Wide , spread out, smooth, layered clouds.
They indicate that the air motion is horizontal
rather than vertical.
Usually created from an air mass that is rising
slowly.
Usually indicates a stable atmosphere.
Normally formed by frontal formation.
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If either class of clouds is NOT lowlying, include the prefixes:
alto – medium level
cirro – high level (cirrus – high,
thin clouds)
May also contain the term “nimbus”,
which means rain-bearing.
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Complete ALL questions (#1-8) on “A Global
Weather Model” – pg. 536-7.
Weather Test #1 – on all material covered up to
this point. (Ch. 13)
Meteorology : the study of the
atmosphere and weather
forecasting.
 Studied by meteorologists.
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Orbiting spacecraft
that gather data and
images, and relays
them to weather
stations on the
ground.
Two types:
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Orbit at around
36000 km above the
equator.
Provide images that
show cloud cover,
physical features,
etc.
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At about 1000 km
above the poles.
Gather data used to
detect changes in
air temp, assess
water vapor at
different levels and
global wind
patterns.
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Helium-filled balloons launched 2 or
more times per day at stations across
N.America.
Carry instruments that collect data
on temp, pressure, humidity, etc.
Also determine wind speed and
direction.
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Instruments used at weather stations.
Instrument
Weather Factor Measured
Thermometer
Temperature
Anemometer
Wind speed and direction
Aneroid barometer
Atmospheric pressure
Rain Gauge
Rainfall
Hydrometer or psychrometer
Relative humidity
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All collected data is gathered, stored,
and analyzed by computer software.
Computers linked to satellite
communication systems allows info
to be sent around the world.
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A weather system is a set of temp, wind,
pressure and moisture conditions for a
region, that moves as a unit over a period of
days.
North American Systems:
In the mid-latitudes of N.America, weather
is difficult to forecast because it changes so
often.
Much easier to forecast near the equator
(hot/humid) and near the poles (cool/dry).
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The basis of weather systems in
N.America.
They are large bodies of air in which
temp and moisture content are fairly
uniform.
Vary in size, from 100 – 1000 km
across
Air Mass
Temperature
Moisture
Content
Where They Form
Maritime
Polar
Cool
Moist
Over the North Pacific and
Atlantic Oceans
Continental
Polar
Cold
Dry
Over mid-polar regions of
N.America
Maritime
Tropical
Warm
Moist
Over the South Pacific and
Atlantic Oceans
Continental
Tropical
warm
Dry
Over mid-southern U.S. and
northern Mexico
Maritime
Polar
Continental
Polar
Maritime
Polar
Continental
Polar
Continental
Tropical
Maritime
Tropical
Maritime
Tropical
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A front is the leading edge of an air
mass.
It is therefore also the boundary
where different air masses meet.
There are 4 types of fronts:
1.
Cold Front
- the leading edge of a cold air mass
- When a mass of cold air pushes under a mass of warm air
and pushes it upward, a cold front forms.
- Active storms are sometimes associated with a cold front
and followed by cool, fair weather.
2.
Warm Front
- Is the leading edge of a warm air mass. As it
approaches the humidity will increase before it
arrives.
- It will be very high while its there, and will show
a slight decrease after it leaves. Rain showers are
associated with warm fronts.
3.
Occluded Front
- In most weather systems, the trailing cold fronts move more
quickly than the leading warm fronts. Because cold fronts
move more quickly, they often "catch" the warm front; an
occluded front occurs.
The warm is lifted above the Earth’s surface and is cut
off (occluded) from the cooler air below.
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4. Stationary Fronts
Stationary Fronts occur when two unlike air masses
face one another, and there is little movement of air.
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- On a weather map, a stationary front is drawn as a
solid line with half-circles and triangles pointing in
opposite directions.
- The air on either side of a stationary front remains still
for some time.
C
B
D
A
FRONTS
(1) Front forms between cold and warm air masses
(2) Jet stream pulls air up from both masses, leaves low
pressure near ground
(3) The low pressure attracts air near the surface
(4) Rising air swirls (Coriolis)
(5) Warm/moist air rises, condenses into
cumulonimbus clouds (precipitation)
(6) Occluded front forms (warm over cold)
(7) Surface air stops drawing upward; precipitation
slows, air pressure increases near the ground and the
storm weakens.
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Cyclogenesis: the process of forming a
cyclone
Cyclone: a low pressure system that
rotates counter-clockwise (in the N.
Hemisphere) and usually brings cloudy,
stormy weather.
Anticyclone: a high pressure that
rotates clockwise (in the N. Hemisphere)
and brings clear skies.
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Warm, high pressure systems: form
at 30o latitude , when air from
equatorial convection currents
moving north becomes “cooler” and
descends.
Cold, high pressure systems: occur
in central Canada and the Arctic,
from cold, dry descending Arctic air .
Complete p. 549, # 1, 2, 3, 4 and 6.
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Regional air movement occurs in a
small area and is caused by
temperature differences between:
- day and night
- the air over land and water
Usually created by warm air rising
over cold and creating convection
currents.
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occurs when air is heated
heated air becomes less dense and rises
on top
rising air cools and falls, while the cool
air below warms and rises
a cycle is created known as a convection
current
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Caused by the heating of the land by the
sun.
Mild winds in the morning.
Moderate winds by mid-day.
Winds die off in the evening.
Birds use them to help them glide.
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Occur during the daytime.
The Sun warms the land faster than
the water.
Air rises from the land and is
replaced by cooler air from above the
water, creating a sea breeze.
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Occur during the evening/night.
The air above the land cools faster
than the air above the water.
Warmer air above the water rises,
and is replaced by the cooler air
above the land creating a land
breeze.
Complete an illustration of a
sea and land breeze.
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When warm air masses move across a
large body of water, they can absorb a lot
of moisture.
In winter, this air can cool rapidly when it
hits land, and can quickly condense
resulting in severe snow events.
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Occur in Western Canada.
Moist air proceeds up the west side of the
Rockies.
The air condenses quickly (moisture
removed), which releases a lot of energy
and warms the air.
Warm, dry winds proceed down the east
side of the Rockies, causing a drastic rise
in temperature.
Complete page 555, # 1-3.
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