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Section 13.1
A Closer Look at the Earth
 Weather: is a set of environmental conditions
encountered every day.
 Climate: is the set of environmental conditions
averaged over many years.
Main components of Earth that influence weather are …
 Land forms
Land
forms
 Atmosphere
 Water in its various
forms (solid, liquid, gas)
Atmosp
here
Water
Weather
Section 13.2
Earth’s Energy Balance
 Life on Earth depends on energy from the Sun.
 Changing weather is also directly related to the energy
from the Sun
 The energy from the Sun is in the form of
electromagnetic energy that makes the Earth warm
enough to support life.
 Energy can be transferred from one place to another in
four ways…
 1. Radiation
 2. Conduction
 3. Convection
 4. Advection
Radiation: is the transfer of energy in the
form of waves
The Electromagnetic Spectrum – shows all types of
radiation that can travel through space at the speed of
light.
Electomagnetic
Spectrum
1. visible
light
2. X-rays
3. gamma
rays
4. UV rays
5. infrared
radiation
6.
microwave
 Conduction…the transfer of energy through the
collision of particles, occurs mostly in solids but can
happen in water.
 Convection and Advection…transfer of energy by the
movement of particles in a fluid, liquid or gas.
 Since weather systems depend on the movement of
particles in the atmosphere and oceans. Convection and
advection apply to weather changes.
 Animation
Reflection and Absorption…
 Some electromagnetic waves are reflected back into
space from the atmosphere. Others are absorbed by
clouds , the oceans or the Earth’s surface.
 Heat sink…any object that gets warmer by absorbing
the Sun’s energy.
 Albedo effect the ability of an object to reflect (rather
than absorb) the sun’s rays. The higher the albedo, the
greater the object’s ability to reflect.
Answer questions 1,2 4 – 10 on page 507
…All of Earth’s water, both fresh and salt, liquid and
ice; the hydrosphere makes up around 70% of Earth’s
surface.
Water distribution in the hydrosphere…
 The vast majority of Earth’s water is in the oceans (salt
water), with smaller, but geologically important,
quantities of fresh water in lakes, rivers, and ground
water.
Distribution of Water on Earth
The Water Cycle
 Energy from the sun causes water to evaporate, or ice to




sublimate.
The invisible water vapour rises, and eventually, as the
pressure and temperature decrease, this vapour condenses
(changes from vapour to liquid) into fog, mist, and clouds.
The resulting precipitation falls to the ground, and the
cycle starts again.
Animation
YouTube - Water Cycle Animation(Nasa)
The Water Cycle . . .
 Because so much of Earth’s surface is covered by
water, our weather systems depend greatly on
water in its three states: solid, liquid, and gas.
The hydrosphere and human
habitat…
 Water-borne diseases caused by impure drinking
water kill approximately 6,000 children per day.
 3.575 million people die each year from water-
related diseases.
 Water borne diseases...
 Bilharzia...
 Ryanswell
 Ryan Hreljac
The hydrosphere and human habitat
 Fresh water is vital for human survival. We live, in
large part, near sources of water.
 We need clean drinking water.
 Weather systems on or near large bodies of water
greatly affect large numbers of people.
Questions…
Page 524…
#1, #2,#4, #5,
#6, #7
Section 13.11
Typical Cloud Formation
Water in lakes, rivers, oceans and plants gains energy
from the Sun. This energy causes the water molecules to
heat up and move more rapidly.
The water then changes from a liquid to a vapour.
Water vapour then rises in the heated, less dense air.
When it reaches higher elevations where it is colder, it
condenses into liquid. This is how clouds form.
Cloud droplet formation...
How do clouds form?
There are three main categories of cloud formation...
1. Convective clouds from
2. Frontal clouds...
previous slide ...
 ...produced when air near the
ground absorbs energy from
heated surfaces (oceans, lakes,
asphalt, concrete, dirt) becomes
warmer and less dense, and rises
in the atmosphere. As the warm
air rises, it carries water vapour
with it.
 ...form where the leading edge,
or front, of a large moving mass
of air meets another mass of air
at a different temperature.
Warm air masses contain more
water vapour. If a warm air mass
moves over a cold one ( figure 3,
531) the warm air rises, expands,
and cools. The moisture
condenses to form clouds.
Figure 3
3. Orographic clouds...
 ...form when air moves
up a mountain,
expands at the lower
pressure, and cools.
Moisture in this rising
air condenses in the
colder air as it goes up
the mountain,
producing clouds.
 Animation
Fog...
• is a cloud
that forms near the
ground.
• Mostly produced on clear
nights when surface energy
radiates upwards but is not
reflected back by any clouds.
• Air near the ground cools
allowing water vapour to
condense into fog.
• Fog also forms when warm air
passes over snow-covered
ground or when moist sea air
drifts over a cold current.
Classifying clouds
Clouds are classified on three different levels;
1. Shape – clouds that
are billowing, rounded
shape are called
cumulus. These
clouds grow vertically
and usually mean
unstable weather.
Clouds that are
mostly flattened
and have a layered
shape are stratus.
The usually form
horizontally, and
often when a warm
air mass overruns a
cold air mass. They
usually mean stable
weather.
2. Height – clouds are given names according to
their height in the atmosphere;



Low level clouds are not given any prefix, simply
known as cumulus or stratus
Mid level clouds begin with the prefix alto
High level clouds begin with the prefix cirrus
3. Moisture finally clouds that contain precipitation
are given the word nimbus.
Please do the following questions…
#’s 1,2,3,4,5 on page 534
Section 14.2
Weather Systems
 A weather system is a set of temperature, wind,
pressure and moisture conditions for a certain region
that move as a unit for a period of days.
 In some areas (ie. arctic) weather systems are easy to
forecast because there is little change.
 In most of North America, they are more difficult
because are influenced by ground and atmospheric
conditions from a larger geographical area.
Air Masses
 An air mass is a pocket of air with relatively the same
temperature and pressure. The air masses that affect
our weather are;
 Continental polar – cold and dry
 Maritime polar – cold and moist
 Continental tropical – hot and dry
 Maritime tropical – hot and moist
Front
 A front is simply the boundary where two different air
masses meet. There are four general types of fronts;
 Warm front – occurs when a warm air mass overtakes a
cold air mass. Usually move north and slower than cold
fronts.
 Cold front – occurs when a cold air mass pushes under a
warm air mass. Cold fronts tend to move west to east
and can move faster than warm fronts and bring about
more noticeable changes in weather.
Animation
 Occluded front – forms when a cold air mass catches up
to another cold air mass that has pushed under a warm
air mass. The result is a warm air mass sandwiched
between two cold masses.
 Stationary front – occurs
when the boundary
between a warm air mass
and a cold air mass remain
still for a period of time,
usually covering a large
geographical area. There is
no rotational movement of
air masses with a stationary
front.
Low Pressure Systems
 Bring cloudy skies and
stormy weather.
 Begin as cold and warm
front meet, creating a
low pressure area near
the ground.
 This low pressure area
pulls air near the surface
in causing a
counterclockwise
rotation.
High Pressure Systems
 Bring clear sunny skies and in Canada is a result of the
cold, descending arctic air.
 High pressure systems rotate clockwise (in the
Northern Hemisphere)
 Weather map – try forcasting!
 Please do questions…
 Page 549 #1,2
 Page 576 # 1,4
…is water that reaches the ground in either liquid or
solid form.
Section 14.5, page 556
Precipitation comes in four forms:
1. RAIN
2. SNOW – precipitation in the form of very small
ice crystals.
3. HAIL- precipitation in the form of small balls
of ice.
4. SLEET – precipitation in the form of snow or
hail, with rain.
There are three important points to remember about
precipitation:
1. Air cools as it rises.
2. As air cools, water vapour (which is invisible) condenses.
• Clouds begin to form. Clouds are made up of very tiny
drops of liquid water, which are held aloft by air currents
because they are so light.
3. If there is sufficient condensation, the cloud droplets will
start to merge together and eventually start to fall as they
get too heavy to stay aloft. This is precipitation.
Air may be caused to rise in one of three ways:
1.
As it crosses an area of higher elevation – causes
orographic precipitation.
2. It absorbs heat from the ground and rises –
causes convectional precipitation.
3.
Cooler, denser air flows underneath it forcing air
aloft – causes cyclonic precipitation.
Orographic Precipitation
http://www.nicholaskrebs.com/Hawaii/Kauai/Rain%20over%20Kahili%20Mountain.jpg
If there is enough
condensation,
precipitation occurs
Leeward side
As air descends down the
mountain, pressure increases
and the air warms up.
Windward side
Precipitation stops as
clouds evaporate as
air warms.
Air cools to the point
when condensation
occurs – clouds form
Rain shadow
Air expands as it
rises and cools
Warm, moist air
from the ocean
Mountain range
forces air to rise
Convectional Precipitation
http://www.okeechobeeeoc.com/images/thunderstorm.jpg
Air cools to the
point where
condensation
occurs – clouds
form
Warm air
expands as it
rises and it
cools
Solar radiation
heats the
ground
Warm air rises
(less dense)
Warm ground heats
the air above it
Condensation continues
and clouds grow
vertically
Warm air
continues to
rise
Heated ground
Summer thunderstorm
clouds develop (called
cumulonimbus)
Enormous amounts
of condensation
occur
Lightning
Updrafts of
warm air
Heavy rainfall occurs
because of large
amount of
condensation.
Downdrafts
of cold air
Heated ground
Eventually the cooling
effects of the rain, the
cold down drafts, and the
lack of solar heating
because of the clouds
stop the updrafts as the
ground cools off.
The rain stops.
The down drafts and
the clouds disappear
Cyclonic or Frontal
Precipitation
http://www.engineering.usu.edu/uwrl/atlas/photos/ch2storm.gif
How Air Masses Influence Our Weather
 The air in the earth’s atmosphere (layer of gases
surrounding the earth) is constantly on the move.
 An air mass is a large body of air with similar moisture
and temperature content.
 Whether an air mass is warm or cold depends on where it
originates.
 Generally, air masses originate in the south in the summer
and the north in the winter.
 The leading edge of an air mass is called a front.
 When the fronts of two air masses meet a battleground is created in the
sky.
 Air masses do not mix.
 A mass of warmer (and lighter) air is always forced to rise above a mass of
colder (and heavier) air.
 The Jet Stream is a river of air
which moves from west to east.
 Air above the Jet Stream
is colder and that below is much
warmer.
 Direction is used to describe
wind.
 Most of the winds in Canada are
called westerlies because they
flow from the west.
 As warm air rises it cools. Cold air does not hold
moisture as well as warm air.
 As a result water vapour in the cooling air
condenses into droplets. These droplets form
clouds.
 Eventually, they become too heavy for the air to
hold and they fall to the ground in the form of
snow or rain depending on the air temperature.
 This is called cyclonic or frontal precipitation.
Cross-section of a mid-latitude cyclonic storm
Because the air is being forced to rise,
mid-latitude storms are also called low
pressure cells or systems.
Precipitation
Condensation
Air cools
Cold Air
Warm Air
Air rises
Cold Air
Clouds and Humidity
 Precipitation is not the only form of water
to be considered part of weather and
climate.
 Clouds and humidity are also mentioned
in weather forecasts.
 Clouds are made of water droplets that are
not heavy enough to fall.
 There are two basic types of clouds:
1. Stratus Clouds – a flat low lying cloud
layer.
2. Cumulus Clouds – dense, usually
white cloud with a dome-shaped top.

 The term humidity is the amount of water vapour in
the air, this is sometimes described as “dampness” in
the air.
 This is described in weather forecasts as “relative
humidity” – the amount of water vapour in the air
relative to the temperature.
 This is described as a percentage.
 The higher the relative humidity the “damper” or
“stickier” the air.
Please do the following questions...
 Page 557 #’s 1,2,3,4
Blizzards, Tornados, Hurricanes, Thunderstorms . . .
Thunderstorms…
 A thunderstorm is a storm
with lightning, thunder,
heavy rain, and sometimes
hail.
 Two conditions must be
met for a thunderstorm to
form…
 1. Moisture is needed to form
clouds and precipitation.
 2. the lifting of the air, or
uplift, must be very strong in
order to produce clouds that
reach high in the atmosphere
Three stages of a thunderstorm…
Cumulus stage----------Mature stage----------------Final stage
Stage 1…Cumulus stage
 Updrafts of warm air
carry moisture upward.
As the warm air rises it
condenses. Updrafts are
caused by convection
currents caused by the
heating of the Earth’s
surface by solar
radiation.
Stage two…Mature stage.
 Cumulonimbus cloud forms
and spreads out at the top.
Cold air containing ice, rain,
and sometimes hail falls
downward in large
downdrafts.
Stage 3…
 In the final stage the
downdrafts reduce the
upward flow of air, and
the storm weakens.
 Lego Animation
Tornados…
 Tornados form in the
most severe
thunderstorms. Fastrising air begins
spinning, forming a
rising funnel of air and
moisture
Tornado formation graphic…
Tornado Formation and Intensity Scale…
 More rising air is
replaced by cooler air on
the surface; the rotation
then becomes faster and
faster. At the center of a
tornado the wind speed
can be as much as 500
km/h.
 Tornado formation...
 Tornado Intensity Scale
Tornado numbers…
 Funnel clouds can be from a few meters to 500 meters
across and can last from a few seconds to several
hours. They travel at speeds up to 100 km/h and move
usually southwest to northeast. Canada experiences,
on average, over 100 per year.
 Did you know…in May of 1986, thirteen school
children in China were hoisted into the air by a
tornado and carried 19 km before falling gently
to the ground!!!
Black Friday in Edmonton…
 The tornado remained on
the ground for an hour,
cutting a swath of
destruction 40 kilometres
long and up to a kilometre
wide in places, and
peaking at F4 on the Fujita
scale, but may have briefly
become an F5. The
tornado killed 27 people,
injured more than 300
people, destroyed more
than 300 homes, and
caused more than 330
million dollars worth of
damage.
Storm tracking…
 Doppler radar is an
important technology used
to track t’storms and
tornados. Radio waves sent
out by the instrument
bounce off water drops and
ice particles in the storm.
Reflected waves reveal the
location of the drops and
particles. A map can then
be drawn of the storm.
 Tornado footage
 Storm Chasers...
Section 15.6
Hurricanes…severe cyclones.
 A cyclone is a low
pressure swirling air
mass. Develops in the
mid-latitudes when cold
and warm air fronts
interact.
 Cyclogenesis is the
process of creating a
cyclone.
Hurricanes and typhoons
 Hurricanes…a severe
cyclone that occurs in
the western Atlantic, the
Caribbean Sea, the Gulf
of Mexico, or eastern
Pacific ocean.
 Typhoons…a severe
cyclone that develops in
the northwestern Pacific
Ocean or the China Sea.
Atlantic Ocean Hurricanes.
 Hurricanes that affect us are Atlantic Ocean
hurricanes. These begin their life in the eastern
Atlantic as low pressure systems which then build
with the presence of warm ocean waters. They
continue to move westward and grow as they move.
Water temp and hurricane formation…
The Engine of the Hurricane…
 If the water temperature is at least 27degrees Celcius,
evaporation occurs rapidly and the warm, rising air
carries a lot of moisture with it. As this air reaches
colder altitudes it condenses, releasing heat that
increases the rate at which the air rises.
 Warm ocean water acts as fuel for a hurricane.
 The hurricane is fed by convection currents.
Evolution of a Hurricane…
 It begins with hot
ocean water and
evaporation setting up
convection currents.
The ensuing lowpressure system turns
to the left, or
counterclockwise.
Animation
Hurricane structure…
 Terms to know…
 Eye,
 Eye wall,
 Rain bands
PEI Hurricanes…
 Hurricane Juan.
 At its strongest was a
Category 2 storm.
Caused extensive
damage in Nova Scotia
and PEI. One last
animation!
 Please do
questions…#2,3,5,7 on
page 597