2 Energy

Question 1

Energy

Answer 1

an agent capable of setting an object in motion

-• units: joule (J) or calorie (cal) (1 J = 0.239 cal)

Question 2

power

Answer 2

• power: the rate at which energy is released, transferred, or received
• units: Watts (W) (1 W = 1 J s-1)

Question 3

Types of Energy

Answer 3

1. kinetic energy: energy in use
   • could relate to the movement of water through a river, or the
   vibration of atoms in a rock
   • the rate of vibration determines an objects temperature
2. potential energy: energy in storage
   • potential energy is stored in a raindrop, and when it begins to
   fall under the influence of gravity, converts the potential
   energy into kinetic energy

Question 4

the rate of ______ determines an objects temperature

Answer 4

vibration

Question 5

Energy can be transfered by (3)

Answer 5

1.Conduction:
-energy moves through a substance with minimal
movement of molecules (solids)

2.Convection
-energy is transferred by mixing two substances (gases
and liquids)
-hotest molecules rise and release heat at the top of the pot

3.Radiation
-energy propagates through space from one object to
another
-no contact occurring

Question 6

Radiation

Answer 6

• everything in the Universe emits radiation
• this is known as electromagnetic (EM) radiation
• the energy moves as a wave
through space
• electric and magnetic
components oscillate through
space together
• the length of 1 cycle, or
wavelength, determines the
quality and quantity of the
radiation

Question 7

Radiation Laws:3

Answer 7

1• Planck’s Law tells us that hot objects release most of their energy at short
wavelengths and that short wavelengths contain more energy

2.• Wien’s Law tells us that the wavelength of maximum emission is inversely
related to the objects temperature
-If temperature goes up, maximum emission wavelength goes down

3.• the Stefan-Boltzmann Law tells us that the total amount of energy
released by an object is directly proportional to its temperature
-as the temp of an object rises, then the release of energy increases

Question 8

the sun releases ____wave energy while the earth releases ___wave energy

Answer 8

short

long

Question 9

Sun

Answer 9

• the Sun emits energy at a more or less constant rate
• over very long time spans, the output of the Sun changes
• the Sun emitted 30% less energy 4.5 billion years ago
• on shorter time spans, sunspots can enhance solar output
• the number of sunspots cycles on an
11 year cycle, but there have been
long periods of reduced sunspots
• although sunspots are relatively cool
(ie, less energy), the area around them
is much hotter than the normal Sun
surface
• as the energy moves through space from the Sun toward Earth, it is
distributed over a greater and greater volume of the solar system, which
reduces its intensity
• the surface of the sun emits 3.865 x 1026
joules each second (W), but we are
150,000,000 km away from the Sun

.When energy leaves the sun, it starts to radiate out into the solar system

• becomes diluted as it moves through space
• 8 minutes from surface of sun to us
• 1367 W m shortwave radiation hits the upper atmos

Question 10

Anything shorter then visible is

ANYTHING LONGER is

Answer 10

ULTRAVIOLET

INFRARED

Question 11

The solar constant

Answer 11

• 1367 W m-2
: known as the solar constant
• this is the energy received at the top of Earth’s atmosphere, and
therefore available to be used by Earth
•Insolation: a measure of the solar energy received on a surface at a given time
• the Sun emitted less energy in the past
• sunspot cycle results in a 0.11% variation in energy emitted over 11
years
• sometimes Earth is closer to the Sun, reducing the distance between
them and increasing the energy received
• DO THESE AFFECT CLIMATE?

Question 12

insolation

Answer 12

a measure of the solar energy received on a surface at a given time

• often used as an anagram of incoming solar radiation
• Earth’s atmosphere is not transparent to incoming solar radiation
• insolation can be absorbed by the atmosphere, warming it up
• insolation can be reflected by the atmosphere, scattering the
energy in any direction
• insolation can be transmitted by the atmosphere, in which case it
reaches Earth’s surface
• these 3 processes are responsible for the nature and distribution of
temperature throughout the atmosphere, and explain many atmospheric
phenomena

Question 13

____W m-2

: known as the solar constant

Answer 13

1367

Question 14

Earth/Sun Geometry

Answer 14

• Earth is tilted at approximately 23.4° to the orbital plane (the ecliptic)
around the Sun and is rotating on this axis as well as revolving around the
Sun
• this gives us the day and year, as well as the seasons

Question 15

Absorption

Answer 15

• gases, liquid droplets, and solid particles in Earth’s atmosphere reduce
the intensity of insolation by absorbing some of the Sun’s energy
• this is an energy transfer - the energy is transferred to the absorber,
which gains that energy and warms
• most gases, droplets and particles are only able to absorb a specific
wavelength of insolation
•Ex:ozone is very effective at absorbing ultraviolet wavelengths
• eg, visible light is not absorbed by the atmosphere, thereby allowing
us to see things
• standing at Earth’s surface, we normally do not receive the full spectrum
of solar radiation, only the wavelengths that are able to pass through the
atmosphere
• these are known as atmospheric windows or absorption bands

• water vapour is also a good absorber of insolation, absorbing longer
wavelengths in the infrared part of the spectrum
• the more water vapour in the atmosphere, the more infrared
radiation that will be absorbed
• consider deserts – there is little water vapour in the air, so all of the
infrared radiation reaches the surface and warms your skin, making
you feel hot
• if you find shade, you will cool down because you are out of the
direct sun
• on the other hand, if you were in a jungle where atmospheric
moisture is always high, the infrared radiation is absorbed in the
atmosphere, and the air feels hot
• if you find shade, you will still be hot because the air carries the
heat, not the sunlight

Question 16

______ light is not absorbed by the atmosphere, thereby allowing
us to see things

Answer 16

visible

Question 17

• standing at Earth’s surface, we normally do not receive the full spectrum
of solar radiation, only the wavelengths that are able to pass through the
atmosphere
• these are known as _____________ or __________

Answer 17

atmospheric windows

absorption bands

Question 18

visible light is 0._ to 0._

Answer 18

0.4 to 0.7

Question 19

Reflectance 2 types

Answer 19

• sometimes, instead of absorbing energy, gases, particles and droplets
simply reflect the energy away
• reflection occurs in 2 ways:

1. specular reflection:
   is a type of surface reflectance often described as a mirror-like reflection of light from the surface. In specular reflection, the incident light is reflected into a single outgoing direction.
2. diffuse reflection: the radiation strikes a surface but is reflected as
   a large number of weak beams in many different directions
   • this is how most natural objects work

Question 20

albedo

Answer 20

Albedo: the ratio of visible light that is reflected by an object

• generally, we can tell the albedo of an object by its colour
• white objects have a high albedo because they reflect a lot of
visible light
• black objects have a low albedo because they reflect little visible
light

Question 21

Albedo:%

fresh snow=

wet soil=

Answer 21

80-85

10

Question 22

scattering

Answer 22

• insolation passing through the atmosphere will
eventually interact with a gas molecule, liquid
droplet, or solid particle
• if not absorbed, the energy will bounce off the
substance and scatter in many directions
• some insolation may go back into space,
some may reach the surface, some may be
scattered again
• when scattered insolation reaches Earth’s
surface, it is diffuse radiation
• diffuse radiation explains why shadows are
not perfectly black

Question 23

when scattered insolation reaches Earth’s

surface, it is _____ radiation

Answer 23

diffuse

Question 24

Scattering:

Small gas molecules-

Mid-sized solid particles

Large liquid droplets

Answer 24

.prefer scattering short wavelengths

• prefer scattering longer wavelengths

• act more like lenses, and will scatter all
wavelengths

• it often is not difficult to see which type of scattering process is
dominating…

Question 25

Rayleigh Scattering

Answer 25

• atmospheric gas molecules reflect and scatter short wavelengths
• recall that UV wavelengths are absorbed by the ozone layer, so the
next shortest wavelengths are the short end of the visible light
spectrum
• this means that blue light (short wavelength) is more effectively
scattered than red light (long wavelength)
• therefore, Rayleigh scattering leads to blue light being scattered in all
directions while red light is transmitted toward the surface
• this makes the sky look blue, makes Earth look blue from outer space,
and makes sunsets and sunrises look red

Question 26

Why is the sky blue?

Why is the Earth the blue planet?

Answer 26

• air molecules will scatter the short wavelengths, reflecting these out into
the atmosphere as diffuse radiation
• since blue light is most easily scattered, the diffuse radiation will contain
mainly blue light, and lesser amounts of green, yellow, or red light
• so, the eye of a person looking into the sky will pick up mainly blue diffuse
radiation, making the sky look blue

• for the same reason, Earth looks blue when you view it from outer space
• this is because Rayleigh scattering reflects insolation in all directions,
including back to space
• also, the “sky” of the Moon looks black, because there is no atmosphere,
therefore no Rayleigh scattering, and no diffuse radiation

Question 27

Why are sunsets red?

Answer 27

• as the Sun sets, insolation
must pass through more
atmosphere, thus the potential
for Rayleigh scattering
increases
• this allows for the longer
wavelengths to be scattered,
and more red light is
incorporated into the diffuse
radiation

Question 28

Mie Scattering

Answer 28

• solid particles are larger than gas molecules, and are suspended in the
atmosphere by turbulence
• these particles may be pollutants, dust, sea salt, etc, and are known
as aerosols
• these particles also behave differently than gas molecules when
reflecting insolation
•they do not prefer a certain wavelength, but will effectively reflect all wavelengths
• they tend to only work as forward-scattering, as opposed to Rayleigh
scattering which is both forward- and backscattering

-is responsible for the dull, hazy sky seen over large cities
• the air pollution, composed of solid particles, scatters all
wavelengths, giving a greyish tinge to the sky
• forest fires and volcanic eruptions also increase atmospheric aerosols,
and therefore can enhance the red colour of sunrises and sunsets

Question 29

Nonselective scattering

Answer 29

• liquid droplets in the atmosphere, due to the condensation of water
vapour, are larger than solid aerosols
• although technically still scattering, droplets act more like lenses,
scattering different wavelengths in different ways

• the result is that each
wavelength is refracted, with the
shortest wavelengths refracting
the most
• this only works for isolated
droplets though
• when aggregated (as in
clouds), all wavelengths are
reflected equally, making them
appear white or gray
• cloud tops are very
efficient reflectors, and are
able to reflect much of the
insolation back into space

Question 30

optically thick atmosphere:

optically thick atmosphere:

Answer 30

insolation must travel through more atmosphere (ie,
sun angle is low), and therefore there is more opportunity for
absorption and reflection – less insolation is received at the surface

insolation must travel through less atmosphere (ie, sun
angle is high), and therefore there is less opportunity for absorption
and reflection – more insolation is received at the surface

-high, thin clouds are optically
thin, since we can readily see
the Sun through them
-low, thick clouds are optically
thick, since insolation is less
able to penetrate them

Question 31

-only __% of the insolation is absorbed by Earths surface

Reflection by clouds: __%

Absorption by gases and clouds: __%

Scattering by atmos __%

Reflection by ground: __%

Answer 31

• in total, most of the radiation received at the top of the atmosphere is
either absorbed by the atmosphere or is reflected and/or scattered back
into space-only 45% of the insolation is absorbed by Earths surface

Reflection by clouds: 19%

Absorption by gases and clouds: 25%

Scattering by atmos 6%

Reflection by ground: 5%

Question 32

Transmission

Answer 32

• the third way in which the atmosphere interacts with insolation is by
transmission, or simply allowing the radiation to pass through unimpeded
• transmitted energy is simply the leftover energy that is not reflected or
absorbed
• since absorption and reflection rates can change based on albedo,
gas/aerosol/droplet concentration, sun angle, etc., transmission rates
also change

.On a clear sunny day, transmission may be 80% of insolation, since little absorption or reflection is happening

.on cloudy or hazy days, or early/late in the day, absorption and
reflection is enhanced, and transmission is reduced

Question 33

• insolation at any given place is determined by: 2 factors

Answer 33

• extraterrestrial radiation: the amount of radiation received from the
Sun at the top of the atmosphere
• absorption and reflection: the reduction of extraterrestrial radiation
by the atmosphere
• although extraterrestrial radiation does not vary considerably, absorption
and reflectance does, both in time and space

Question 34

surface interactions with insolation

Answer 34

any energy that passes through the atmosphere and reaches Earth’s
surface can either be reflected away or absorbed
• transmission through Earth’s surface does not occur
• there is a balance between reflection (albedo) and absorption
(warming)
• highly reflective places (snow and ice) tend to be cooler because
less energy is absorbed
• poorly reflecting places tend to be warmer since most of the energy
is absorbed by the surface

Surface albedo: is therefore a critical control of earths temperature and larger scale climate
-very important control of temperature

Question 35

on average, Earth’s surface albedo is __%, mainly because Earth’s
surface is mostly water which has a relatively low albedo

Earth’s planetary albedo, which takes the atmosphere into
consideration, is __% (mainly due to the influence of clouds)

Answer 35

15

30

• since more energy is absorbed by the surface than the atmosphere, we
must recognize that it is the surface that warms the planet, not the air
• for the most part, Earth’s surface substances absorb all wavelengths, but
there is 1 important exception…blue, as blue objects do not absorb blue

Question 36

Earth’s surface substances absorb all wavelengths, but

there is 1 important exception…

Answer 36

blue, as blue objects do not absorb blue

Question 37

Plant response to insolation

Answer 37

• a typical leaf absorbs UV radiation and visible light effectively, but
reflects or transmits infrared radiation
• transmitting infrared radiation keeps the leaf cool, preserving the
tissue
• the energy that is absorbed is used in photosythesis

Populus deltoides (Cottonwood tree)
• this also explains why plants need sunlight
to grow – visible light energy is more
effectively reflected and scattered during
cloudy days, meaning less of that
wavelength reaches the surface

• the rate of photosynthesis is dependent also on the total amount of
radiation received
• trees will grow faster under more direct sunlight, but eventually this
relationship stops as the plant becomes light-saturated
• shade-loving plants have low light-saturation levels while sun-loving
plants have high levels

• any excess sunlight beyond
the light-saturation level may
damage the tissues of the
plants, leading to wilting and/or
death

Question 38

Solar Panels

Answer 38

• solar panels work in a similar way to plants
• photovoltaic cells are only capable of
absorbing certain wavelengths and converting
the energy into power
•The wavelengths that the cells cannot absorb are reflected and the energy is lost
• for most solar panels, the range of useful
wavelengths is small – only about 20% of the
sunlight can be absorbed by the panel
• new technology is trying to expand the
range, thus increasing the efficiency of solar
panel technology

Question 39

Effects of clouds

Answer 39

• clouds act to complicate these processes, mainly by “closing the
atmospheric windows”
• clouds are very efficient at absorbing longwave radiation, so increased
cloud cover means more heat will be trapped in the atmosphere
• consider the case of cloudy vs clear nights

ex: clear night
• on a clear night, all atmospheric
windows are open, and the
radiation is able to escape higher
through the atmosphere, and
potentially into space
• these nights tend to be cold,
since the radiation is longwave
(heat) and is being lost

ex: cloudy night
• on a cloudy night, some
atmospheric windows are closed,
so some of the heat is absorbed by
the clouds, which warm the
surrounding air
• these nights tends to be warm,
since the clouds act as an
insulating blanket

Question 40

Greenhouse effect

Answer 40

• since incoming shortwave radiation is absorbed much less by the
atmosphere when compared to outgoing longwave radiation, we often
consider the atmosphere transparent to solar radiation and opaque to
terrestrial radiation
• this is where the analogy of Earth as a greenhouse comes from
• however, it is not entirely true!
• a greenhouse works because it prevents
wind from removing the hot air built up in
the greenhouse
-the atmosphere does not do this
-if we measure the amount of energy exiting the top of the atmosphere , Earth appears to have an average temp of -18 degrees Celsius

Earth’s greenhouse effect is generated by the constant emission,
absorption, emission cycle between Earth’s surface and atmosphere
• although there is a net loss of longwave radiation to space (in order to
balance the receipt of shortwave radiation), the cycling between surface
and air dominates the longwave radiation balance
• if we measure the amount of energy exiting the top of the
atmosphere, Earth appears to have an Earth appears to have an average temp of -18 degrees Celsius
• but our measurements of Earth surface suggest a global average
temperature of 15 °C
• this is caused by the greenhouse effect, which increases Earth’s
surface temperature by 33 °C
• without this warming, life probably could not exist

Question 41

Greenhouse effect is generated by..

Answer 41

the absorption of longwave
energy by “greenhouse gases” - GHGs

Water vapour-36-72%

Carbon dioxide-9-26%

Methane-4-9%: better greenhouse gas then C.D as it can hold and radiate more heat

Ozone-3-7%

• for the most part, these greenhouse gases are perfectly natural, but
humans, particularly through fossil fuel burning, are augmenting their
concentration in the atmosphere
• there are many other, minor greenhouse gases, some of which have no natural sources

Question 42

_____ is the greenhouse gas which has grown in abundance the most

Answer 42

methane

Question 43

enhanced greenhouse effect

Answer 43

• the human induced addition of GHGs to the atmosphere is known as the
enhanced greenhouse effect
• the addition of greenhouse gases to the atmosphere offsets the balance
between incoming and outgoing radiation, such that less radiation is
leaving Earth and heading into space
• this means more energy is staying in the atmosphere, trapped by the
greenhouse effect, and warming the atmosphere
• hence, “global warming”

Question 44

Other Energy Transfers (2)

Answer 44

Conduction: a temperature gradient is generated between 2 objects and a flow of heat occurs

Convection: heat is transferred through a liquid, as hot liquid moves through cooler liquid

Question 45

Conduction

Answer 45

• solar energy received at the surface warms the surface layer (eg, rock)
• since the solar energy is not transmitted through the rock, the layer
immediately below the surface is cooler
•no matter is displaced, only energy is exchanged between two objects
• this sets up a thermal gradient, and heat energy will always flow from
warm to cool objects – in this case, the warm surface rock will warm the
rock beneath, thus transferring energy
• the rock also warms the air molecules sitting above, which warm the air
molecules above them, etc. – slowly the energy conducts up into the
atmosphere

Question 46

Convection

Answer 46

•
•.hot air(or any fluid) rises
• warm air sitting immediately above Earth’s surface rises into the cooler air
lying above it
• this involves a displacement of matter – air molecules actually move from warm to cold areas, transferring energy as they go
• hot air is less dense than cold air (and therefore more buoyant), thereby
forcing the motion
• this process involving density and buoyancy is known as free convection

• air may also rise under turbulent forces, where air is forced to rise due to
obstructions
• mountains, trees, buildings…
• this forced convection is a factor in all fluid dynamics
• ordinarily uniform flow is broken down into smaller, swirling eddies

Question 47

free convection

Answer 47

this process involving density and buoyancy is known as free convection

Question 48

Sensible and Latent Heat

Answer 48

on Earth’s surface, we observed two of these forms, and call both heat
• sensible heat: the heat we feel
• latent heat: the heat we don’t feel

Question 49

Sensible heat

Answer 49

•.all objects contain heat-we measure this as temperature
• in solids and gases, temperature is a measure of the vibrational
frequency of atoms
• if the atoms are vibrating a lot, we observe that the temperature
is high
• the 0
th Law of Thermodynamics: if A and B are in thermal equilibrium with
C, then A is also in thermal equilibrium with B
• when atoms are in thermal equilibrium, there is no exchange of
energy
• but when they are not (say A is warmer than B), then there will be an
exchange of energy, from A to B
• this results in a cooling of A and a warming of B, until they reach
the same temperature, thermal equilibrium

• just like all matter, air molecules are subject to the Laws of
Thermodynamics, and therefore they are constantly exchanging energy
with each other
• we feel this by recognizing that some air is warmer or colder than other
air
• when warm air invades a cold air mass, a thermal disequilibrium exists
between the two, and a sensible heat exchange will occur as they move
towards thermal equilibrium
• the amount that an objects temperature will change during this process
is dependent on the specific heat of the object
• specific heat:the amount of energy required to produce a given temperature change per unit mass of the substance
• note that mass is involved – the more massive the object, the more
energy that is needed to change the temperature

Question 50

specific heat

Answer 50

specific heat:the amount of energy required to produce a given temperature change per unit mass of the substance

Question 51

heat capacity

Answer 51

• heat capacity: the amount of heat necessary to raise a unit volume
of a substance through a temperature change of 1 K

Question 52

if one air molecule is very hot and the other very cold, the sensible heat flux will be very ____(high/low)

Answer 52

high

Question 53

Latent Heat

Answer 53

• unlike sensible heat, we do not measure or feel latent heat
• latent heat: the energy required to change the phase of a substance
• normally, we are only concerned with phase changes of water

Latent Heat of fusion: the energy required to turn liquid water to ice (333.7 kj/kg)

Latent Heat of Vapourization/evaporation:
the energy required to turn
liquid water to water vapour (2501 kj/kg)

Latent heat of sublimation:
the energy required to turn ice to water
vapour (2834 kj/kg)
=(vaporization + fusion)

• in order to change phase, energy has to
be applied
• when we apply energy to a
substance that isn’t undergoing a
phase change, the substance
experiences a temperature change
(ie, sensible heat change)
• however, during a phase change,
temperature does not change even
though energy is being absorbed by
the substance (ie, latent heat
change)

Question 54

Latent heat: released or absorbed during..

Evaporation

condensation

melting & freezing

Answer 54

• note that latent heat is either absorbed or released during a phase
change
• during evaporation, heat is taken out of the air and added to the
water, effectively cooling the air and creating vapour
• during condensation, heat is released by the water and added to
the air, effectively warming the air and adding water
• the same holds for melting (absorbing energy) and freezing
(releasing energy)
• also, the latent heat of vaporization is 7.5
times greater than the latent heat of fusion,
meaning that evaporation/condensation is a
much more substantial energy exchange than
freezing/melting

Question 55

• also, the latent heat of vaporization is 7.5
times greater than the latent heat of fusion,
meaning that ______/______ is a much more substantial energy exchange than _______/______

OPTIONS:

evaporation/melting

freezing/melting

place one of the pairs in each spot

Answer 55

evaporation/condensation

freezing/melting

Question 56

Earths Energy Balance

Answer 56

• Earth’s surface is constantly gaining energy while Earth’s atmosphere is
constantly losing energy – if this were to persist, then the surface would be
unbearable hot while the air would be unbearably cold
• sensible and latent heat transfers remove heat from Earth’s surface
and send it into the atmosphere, thus balancing the energy system

• when we consider all of the energy sources and transfers in the climate
system, we find that everything is balanced
• the receipt of insolation acts to warm Earth, while longwave
radiation lost to space cools Earth
• increased air temperature leads to increased evaporation – sensible
heat increases then is removed as latent heat
• without this balance, Earth would be too hot or too cold
•.this balance has existed for billions of years, despite changes in solar energy-the climate system is dynamic