Transcript Unit 4 - SharpSchool

Unit 4
Energy Flow in Global Systems
Systems
• three types depending on their interactions with
its surroundings.
• open system – energy and matter can enter
and leave. Ex a tree
• closed system – energy can enter and leave
but matter can not. Ex the earth
• isolated system – neither energy or matter may
enter or leave. Ex the universe
The Biosphere
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the layer around the earth in which living
organisms are found
three parts
atmosphere – air
lithosphere – land
hydrosphere – water
Radiation
• is the process by which solar energy reaches
Earth
• visible light reaches the Earth’s surface
unchanged
• some of the visible light
• is absorbed – heating the surface
• is reflected
• the warmed objects on the surface emit infrared
radiation
Radiation continued
• infrared radiation may be temporarily
trapped in the atmosphere but eventually
is lost to space
• Earth maintains an energy and
temperature balance by radiating as much
energy into space as it absorbs
• dark surfaces absorb more energy and
light surfaces reflect energy
Radiation continued
• the reflectivity of a surface is called –
albedo
• the greenhouse gases in the atmosphere
absorb infrared radiation keeping the
surface warm during the night
• the greenhouse gases include: water
vapour, carbon dioxide, methane, nitrous
oxide, ozone, CFC’s and HFC’s
Climates and Seasons
• climate is the trend in temperature,
atmospheric pressure, humidity and
precipitation over many years
• weather is these same factors at a certain
time and place
• the tilt of the Earth’s axis and the curvature
of the surface result in differing amounts of
solar radiation absorbed
Climates and Seasons cont
• tilt of the Earth – angle of inclination –
determines the length of day and night at
different latitudes
• the Earth travels around the sun in an
elliptical orbit
• for ½ the year we are tilted away from the
sun and ½ the year we are tilted toward
the sun
Climates and Seasons cont
• the three main factors that affect heating
at the surface are
• 1. surface conditions - albedo
• 2. tilt - seasons
• 3. latitude – angle of incoming solar
radiation
(amount absorbed/reflected)
Specific Heat Capacity
• is the amount of heat required to raise the
temperature of 1 g of a substance by 1 ºC
• Q = mc∆T
Q = amount of heat (J)
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m = mass in g
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c = specific heat capacity (J/gºC)
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ΔT= change in temperature (°C)
Transfer of Energy
• several mechanism of energy transfer
play a role in heating the atmosphere
• 1. conduction – transfer of energy from
one molecule touching another
• energy always moves from the warmer
object or molecule to the cooler one
Transfer of Energy cont
• 2. convection – air circulates and distributes
heat
• warm air is lower density than cooler air and so
will rise and carry heat with it
• 3. radiation – the greenhouse gases absorb
the long wave radiation given off at Earth’s
surface
• all molecules will lose heat by radiation
Phase Changes
• when a phase change occurs energy is
gained or lost with not change in
temperature
• for example water at 0°C loses energy in
order to freeze
• heat of fusion (Hfus)amount of energy
required to melt one mole of a substance
Phase Changes cont
• or the amount of energy lost to freeze 1 m
of a substance
•
• Q = nHfus
Phase Changes cont
• heat of vaporization(H vap) the amount of
energy required to convert one mole of a
substance from a liquid to a gas
• the amount of energy lost convert 1 m of
a substance from a gas to a liquid
• Q = n Hvap
Unique Properties of Water
• water has a high specific heat capacity (
4.19 J/g°C)
• large amounts of heat has to be lost or
gained to change the temperature of large
bodies of water
• as a result bodies of water have a
moderating effect on nearby land
Unique Properties of Water
• water has a high heat of vaporization
(40.68 kJ/mol)
• water has a high heat of fusion (6.01
kJ/mol)
• water expands when heated and contracts
when cooled reaching its greatest density
at 4 °C
Unique Properties of Water
• below 4 °C water begins to expand
resulting in ice that has lower density than
liquid water
• this explains why ponds and lakes freeze
on the surface allowing aquatic organisms
to survive the winter below the ice
Hydrologic Cycle
• look at the diagram on page 386 and
sketch in your notes
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• Work Pg 387
# 1-5
Distributing Heat - Oceans
• oceans are large heat reservoirs
• water has low albedo and absorbs more than
90% of the solar energy striking it
• oceans cover 70% of the Earths surface
• ocean currents carry warm water to different
latitudes affecting coastal areas and influencing
worldwide climate – Gulf Stream which becomes
the North Atlantic Drift
Distributing Heat - Oceans
• Gulf Stream is part of a global ocean
current called the thermohaline
circulation or Great Ocean Conveyor Belt
• El Nino – Southern Oscillation (ENSO) –
is a disruption of the ocean-atmosphere
system
• occurs every 3 to 7 years
Distributing Heat - Oceans
• during El Nino the wind direction over the
south Pacific reverses
• read pg 389-390
• La Nina – causes an increase in strength
of the normal patterns of westward moving
winds
Patterns of Wind Movements
• low pressure occurs as warm air expands
becoming less dense and rises
• high pressure occurs as cold air
contracts, becomes denser, and descends
• a convection current is created when
warm air rises at one location cools and
contracts sinking to the surface at another
location
Patterns of Wind Movements
• there are actually three separate
convection currents in each hemisphere
• warm air rises at the equator and sinks at
30° (N and S)
• warm air rises at 60° (N and S) and sinks
at the poles
Patterns of Wind Movements
• convection currents veer sideways from their
original path due to the rotation of the Earth on
its axis – this is called the Coriolis Effect
• this creates
• 1. Polar Easterlies
• 2. Prevailing Westerlies
• 3. Northeast Trade Winds
• 4. Doldrums – quiet area of little winds
Jet Streams
• are currents of extremely fast-moving air
about 10-15 km above the Earth’s surface
• flow from west to east
• form at boundaries of warm and cold air
• intense winds in the jet stream influence
precipitation and thunderstorms
Oceans and Mountains
• sea breezes are formed when in the
morning the sun warms the land before
the water and the air over the land rises
and over the water the cool air sinks
creating a convection current
Oceans and Mountains
• land breezes are formed in the evening when
the water stays warmer longer so now the warm
air rises over the water and sinks over the
cooling land again creating a convection current
• Prevailing Westerlies bring warm moist air
onshore in BC, as this air is forced to rise higher
to get over the mountains the air cools, the
moisture condenses and falls as precipitation –
orographic precipitation
Oceans and Mountains
• the cool dry air moves down the eastern
side of the mountains warming up due to
the increase pressure
• little rain occurs here in the rain shadow
• in the winter this warm westerly wind is
called a Chinook (snow eater) as it melts
and evaporates or sublimates the snow as
it goes
Climate
• temperature is a critical element in
defining climate
• altitude is also important – temperature
drops 4.5 ºC for every kilometre increase
in altitude
• humidity is the amount of water vapour in
the air
Climate continued
• at higher temperatures more water
molecules have enough kinetic energy to
exist as a vapour
• if the humidity is low organisms dry out
• the temperature at which water condenses
and begins to fall as rain or snow is called
the dew point
Climatograph
• is a graphical representation of climate
data for a specific region and time period
• includes average monthly temperature and
total monthly precipitation
• do investigation 11-A page 405
Biomes
• can be defined as a major geographic
region with similar environmental
conditions and life forms
• freshwater and ocean or aquatic biomes
dominate the biosphere
• 6 distinct terrestrial biomes will be
examined
• look at page 407
Adaptations and Biomes
• an adaptation is any characteristic that
enables an organism to better survive and
reproduce in an environment
• 1. physiological adaptations – occur
inside an organism, eg the changes when
animals hibernate
• 2. structural adaptations – physical
features of an organism, eg fur for warmth
Adaptations and Biomes
• 3. behavioural adaptations – things the
organism does to survive, eg migration
• Using your text book make notes on
the 6 terrestrial biomes
Paleoclimate
• is the study of past climates
• Geological Survey of Canada has
completed reconstructing Canada’s
Paleoclimate from 6000 years ago
• they discovered the vegetation zones
Paleoclimate
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causes of natural climate change
o Earth’s tilt
o Earth’s orbit
o continental drift
o weathering (breaks rocks into smaller pieces)
o catastrophic events – meteors, volcanoes
feedback
Paleoclimate
• rapid climatic changes sometimes
resulted in “mass extinctions”
• slower climatic changes may explain
animal migrations, evolution of physical
characteristics, changes in diet, decreases
in populations and forests moving north
and south