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Unit 4: Earth and Space - Weather Systems (22.5 hours) |
Students will learn about the fundamental factors in nature which produce daily weather both locally and globally as well as seasonal and climate changes. Techniques for information gathering are discussed and where possible performed by the students.
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Text: Science 10, Nelson |
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Lesson One |
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Summary: |
Homework: |
WEATHER
weather
– environmental conditions that are encountered day to day
climate
– set of environmental conditions and patterns over many years
weather dynamics – study of motion of water/air that causes weather patterns
eg. Bernoulli’s
principle –if the speed of fluid is high then the pressure is low
-if the speed of fluid
is low then the pressure is high
-movement generally occurs from high to low pressure
Demonstrations of Bernoulli's Principle
blow over paper – blowing creates low pressure over paper, which rises towards the low
pressure area
blow into open bag – blown air enters the bag, making it low pressure. surrounding high pressure air enters bag.
blow between cans – low pressure area between cans, so cans move together
blow ball in funnel – low pressure in funnel pulls ball towards funnel, not out
Weather
Terms
Longitude – lines running from north to south pole – 0o is
Greenwich, England
Latitude – lines running parallel, from east to west
Some important latitudes:
Tropic of Cancer is 23.5o N of equator
-northern most point to have vertical rays of sunlight (on June 21)
-southern equivalent is the Tropic of Capricorn (23.5o S of
equator)
Arctic Circle is 66.5o N of equator
-southern most point to have a full day of darkness (on December 21)
-southern equivalent is the Antarctic circle (66.5o S of
equator)
Mid-latitudes are regions found between the circles and the tropics (most Canadians live
mid latitude)
Show Bill Nye video on Seasons
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Lesson Two |
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Summary: |
Homework: |
HEAT
TRANSFER
heat –kinetic energy of particles of matter (thermal energy)
HEAT TRANSFER BY CONDUCTION
-heat
moves from through one substance, or from one substance to another, by direct contact
(from hotter substance to cooler substance)
eg.
a spoon becomes hot when placed in hot coffee
-conduction
does not occur if there is no temperature difference.
-substances
that are good at conducting heat by conduction are called “conductors” (eg. metals)
-solids
can conduct heat better than liquids or gases
-“insulators”
are poor conductors of heat (eg. plastic, wood)
KMT
(kinetic molecular theory) to explain heat transfer by conduction:
-remember that molecules move faster when heated.
-if brought in contact with cooler slower moving molecules, they hit them, transferring
kinetic energy
(heat will now increase in the
cooler object as it's molecules speed up)
-solids will conduct quicker as the molecules are close together,
and don’t have to move as far to influence the others
-“thermal
conductivity” is a measure of how well a substance conducts (high in conductors,
low in insulators)
HEAT TRANSFER BY CONVECTION
-heat is
transferred through a fluid from a region of high temperature to a region of
low temperature by the
movement of the fluid itself.
(does not occur in solids since they do not flow)
KMT
(kinetic molecular theory) to explain heat transfer by convection:
-hot molecules in fluid move quickly, and spread out. As these molecules
spread out, they become less dense.
The fluid with less density rises in the denser fluid. This fluid rises
and loses heat to the
denser cool fluid.
As the hot fluid cools, it becomes more dense and drops back down
again.
This is a “Convection Current”. (eg. water, air are able to flow in
convection currents)
Do conduction and convection lab
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Lesson Three |
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Summary: |
Homework: |
HEAT TRANFER BY
RADIATION
-radiation is transfer of energy in waves,
and does not require a medium (material to move through)
-heat transfer by radiation can therefore occur in space
-the electromagnetic spectrum consists of large waves (radio, micro, infrared),
visible light (ROYGBIV),
and small waves with much energy (UV,X rays, gamma rays)
-these waves are converted into heat as molecules absorb the energy and move
faster
ATMOSPHERE
-view atmosphere video
Atmosphere is wider at equator as high temperature results in warmer air expanding (this is narrowest and denser at the poles)
Levels within the atmosphere distinguished by altitude/elevation (height above sea level (km)
TROPOSPHERE (0-12 km over earth)
STRATOSPHERE (12 km –50 km over earth)
MESOSPHERE (50 km-80 km over earth)
THERMOSPHERE (80 km-500 km over earth)
EXOSPHERE (500 km-up) thin outer layer
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Lesson Four |
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Summary: |
Homework: |
ATMOSPHERE
-the atmosphere
is the thin blanket of air/moisture around earth
-atmosphere
is most dense at sea level
-atmosphere
consists of 78% N2, 21% O2, and other gases in small
amounts (argon, CO2, H2O)
(other
spheres... lithosphere –area covered by earth/rock
hydrosphere –area covered by water
biosphere –area covered by living things)
Atmosphere is wider at equator as high temperature results in warmer air expanding (this is narrowest and denser at the poles)
Levels within the atmosphere distinguished by altitude/elevation (height above sea level (km)
TROPOSPHERE
(0-12 km over earth) contains most ,moisture responsible for weather systems
-temperature decreases from 20oC to –50oC with altitude
-highest
(16 km) at equator, smallest (8 km) at poles for an average of 12 km
TROPOPAUSE
–thin boundary over the Troposphere, with no temperature drop with altitude increase
-ozone
increases with altitude, trapping UV light and increasing temperature
STRATOSPHERE
(12 km –50 km over earth) dry layer with high ozone concentration
-as
height increases, ozone traps more UV, so temperature increases to 10oC
MESOSPHERE (50 km-80 km over earth) contains low density gases, cooler (-75oC)
THERMOSPHERE
(80 km-500 km over earth) low density gases, but moving quickly so the temperature
is high (30o)
-X-rays
trapped here, and so heat increases
-ions
are made by the sunlight and produce Northern, Southern lights
EXOSPHERE
(500 km-up) thin outer layer
-space
-few particles spread out, mostly hydrogen
Do activity on prevailing winds
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Lesson Five |
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Summary: |
Homework: |
PREVAILING WINDS
Prevailing
winds are characteristic winds that affect large areas
These winds are generally named after the direction from which they originate
CORIOLIS EFFECT
-coriolis
effect is an apparent change in direction of a moving object due to a rotating
system
eg.
the earth, as viewed from the north pole, is moving counterclockwise
-a
wind moving from one side of the earth towards the north pole will therefore
appear to bend to the right
because of the counterclockwise rotation of the earth
-this
results in northerly winds moving EAST (to the right) and southerly
winds moving WEST (to the left)
-viewed
from the southern hemisphere, the effect is reversed as the earth appears to move in a clockwise
direction.
PREVAILING WINDS IN THE NORTHERN HEMISPHERE
Northeast
Trade Winds (blow south and west from 30o to equator)
-hot
air in equator rises (less dense) pulling cooler, denser air from 30o
N
-a
convection current is created this way, resulting in a Southern wind
-Coriolis
effect produces the easterly direction
Mid Latitude Westerlies (blow north and east from 30o to 60o)
-some
air descending at 30o from convection currents creating Northwest
trade winds moves north towards low pressure region at 60o
-at
60o, warm southern winds meet cooler polar winds and rise as they
are
less dense. This results low pressure (less air).
-a
convection current results with a Northern wind, moving west because of Coriolis effect
Polar Easterlies (blow south and west from pole to 60o)
-pole
has very dense atmosphere, and air moves south to lower pressure
-at
60o this air is less dense, and encounters warm southern air. Some
rises.
-a
convection current results with a Southern wind, moving east because of Coriolis effect
Jet Stream (blow east at 30o and 60o)
-air
in middle of convection currents (in middle of troposphere) has air above it creating
pressure.
-when cold northern air meets warm southern air, the warmer air has
higher pressure
-this pressure difference between the fronts is greater at higher altitudes
-high pressure warm air moves north towards the cooler low pressure air
where these fronts meet
-this northern wind moves easterly at these gaps because of Coriolis effect and creates the "jet stream"
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Lesson Six |
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Summary: |
Homework: |
CAUSES OF OCEAN CURRENTS
-causes of ocean currents include:
Convection:
-sun-warmed water travels from equator to the poles where water is cooler and denser.
-cool water moves in to replace this water at the equator.
Winds and Coriolis Effect:
-water moves as the winds move with Coriolis effect, twisting Northern
waters to the right
-Southern waters are twisted to the left
Earth’s Rotation:
-the Earth moves east, resulting in wide, slow currents on the eastern side of bodies of
water
-western side of bodies of water have thin, fast currents.
Salt in Oceans:
-as water evaporates, the concentration of salt in water near the surface increases
-the dense surface water drops down to be replaced by less salty water
from lower in the ocean.
Heat Capacity:
-warm air holds more water, and cool air stores less.
-the oceans act like “heat
sinks”, and take a long time to heat up and a long time to cool down.
Draw ocean currents in blue and red (naming each)
EFFECTS OF OCEAN CURRENTS
-heat
capacity results in June 21 being followed by the hottest days, as the water (and warm air)
take some time to heat up.
-the coolest days follow Dec. 21 as water and air take some time to cool down.
-warm
wet air in warm currents that hit Brazil on the east coast result in rain.
-cool dry air in cool currents that hit Peru result in desert conditions on
coast.
-warm
gulf stream air warms Sweden but not northern Canada (does not move that way),
-this results in frozen Canadian harbors freeze, while those in Sweden do not
freeze.
Current around Antarctica goes all the way around the world unstopped.
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Lesson Seven |
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Summary: |
Homework: |
CLOUD FORMATION
-clouds form when warm air, carrying vaporized water, rises
as it is less dense.
-this rising results in cooling of the water and it recondenses form
droplets
-when
1000’s of droplets join a raindrop is formed and gravity pulls it down
-cloud formation activity outside
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Lesson Eight |
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Summary: -describe cloud formation and classification |
Homework: |
CLOUD FORMATION
Clouds
form as:
Convective clouds: warm moist air absorbs energy from heated
surfaces
-this less dense air rises and cools as the particles lose energy and the
pressure decreases
(low pressure = low temp.)
-as the rising air cools the water recondenses and forms clouds
Frontal clouds: a warm front hits a cold front, and warm air rises over the top
-as the warm air rises cooling occurs with energy loss and less pressure
-as the rising air cools the water recondenses and forms clouds
Orographic
clouds: warm moist air hits a mountain, and moves up
-as the warm air rises cooling occurs with energy loss and less pressure
-as the rising air cools the water recondenses and forms clouds
Fog
(low lying clouds): on clear nights heat is lost from the earth and the ground level cools
-air on ground level cools and water recondenses to form
clouds/fog
-on shorelines warm ocean air collides with the cool land
-as ocean air cools the water recondenses and forms clouds/fog
CLOUD CLASSIFICATION
Cumulus
clouds: billowing rounded clouds
-grow vertically
-indicate unstable weather (warm air hitting cool air)
Stratus
clouds: flattened layered clouds
-grow horizontally
-indicate stable weather (warm air going over cool air)
prefixes and suffixes: -alto: mid level clouds (prefix)
-cirrus: high level clouds
(prefix)
-nimbus: rain holding clouds
(suffix)
complete lab on classifying clouds
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Lesson Nine |
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Summary: -describe high pressure systems, anticyclones -show storm video |
Homework: |
LOW PRESSURE REGIONS
Low
Pressure Regions are usually stormy, cloudy skies
-a cold front (air mass shown with blue line and triangles) hits a warm front (air
mass shown with red line and circles)
-a stationary front results, as the two fronts stop movement
-near a jet stream (30o, 60o), warm air is
pulled up over the cold air
-these
fronts try to move past each other to the right due to Coriolis effect.
-as
the warm air mass rises it pushes north again, resulting in a counter-clockwise
spin
-the
warm air gets higher and cools. Moisture in these clouds condenses to form
cumulonimbus clouds. Rain often follows.
-as
warm air rises and less air is left behind, resulting in a low pressure region
-this
low pressure pulls in other warm air, which rises, in turn
-if
the cold air front intersects the pull of the jet stream and the low pressure region, an occluded
front occurs
-occluded fronts end the bad weather and low pressure region
-if
the low pressure region continues, a cyclone could result, with a much bigger storm as more
air is pulled up by the jet stream
HIGH PRESSURE
SYSTEMS
High Pressure
Systems usually bring clear skies
-anticyclones
could form as air pushed down bends to the right (forming a clockwise spin in the northern
hemisphere)
-this
spin is due to the Coriolis effect and is more prevalent in the poles, and less
so near equator
-high
pressure can be formed when:
-air from equator due to convection
currents descends at 30o as it becomes cooler and denser.
(this air could be very humid over Gulf of Mexico)
-cool arctic air pushing in from the north is
very dense and dry
A
barometer is used to measure pressure change:
increases
= good weather (high pressure systems)
decreases = bad weather (low pressure systems)
Do lab
on twisters
Storm video
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Lesson Ten |
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Summary: -twister video |
Homework: |
WEATHER MAPS
Map
Terms:
Low
Pressure Regions: shown with L
High
Pressure Regions: shown with H
-symbol for occluded front \
\ \ (indicates cold air has cut off warm air, and storms are
ending)
-rain
is shown with dashed lines
-thunderstorms
are shown with zigzag lines
-symbol
for snow is ***
Our weather moves to the EAST generally due to the coriolis effect