This chapter discusses: The role of solar energy (e.g. short

1
Energy Warming the Earth the Atmosphere

• This chapter discusses
• The role of solar energy (e.g. short wave
  radiation) in generating temperature heat
• Earth's processes for heat transfer in the
  atmosphere, including long wave radiation, to
  maintain an energy balance

2
What is Energy?

• Energy is the ability or capacity to do work on
  some form of matter.
• Work is done by pushing, pulling, or lifting of
  matter.
• Since the size of the atmosphere is undefined,
  the size of the atmosphere is handled on a
  case-to-case basis.
• Two types of energy
• ____________ the amount of energy an object
  possesses
• ____________ energy of motion

3
Temperature

• When solar radiation collides with atmospheric
  gas molecules, the gas molecules move.
• This produces
• _________, defined as the moving molecules
  average speed
• kinetic energy - the faster the speed, the
  higher the energy level
• The total energy ________ with greater molecule
  volumes.
• The figure shows that how the average speed of
  the molecules can be the same but the internal
  energy can be different.

4
Temperature Scales

• Thermometers detect the movement of molecules to
  register temperature.
• Fahrenheit and Celsius scales are calibrated to
  _______ and ______ water at sea-level, but the
  Celsius range is about 1.8 times more compact
  (e.g. 1C 33.8F34F).
• While the Kelvin scale does not go below 0K.
• The image below show how these scales compare
  with one another with respect to specific points
  and events.

5
Latent Heat

• Defines as the heat energy requires to change a
  substance from one state to another.
• This heat source is sometimes referred to as a
  ______ warmth.
• Latent heat is released from or absorbed within
  the water molecules when phase change occurs.

6
How does kinetic energy change the size of a
water droplet?
Average velocity outside the droplet 20 units
Average velocity within the droplet 12 units
7
Surface of a water droplet as molecules evaporate
(___________) droplet average velocity has
decreased due to faster molecules within the
droplet escaping
Velocity of the faster molecules within the
droplet 16 units
Average velocity outside the droplet 18 units
Average velocity within the droplet 8 units
8
Surface of a water droplet as molecules
condensate (____________) average velocity
outside of the droplet has increased due to the
removal of slower molecules from the atmosphere
hence increasing the speed of the overall
atmospheric molecules velocity
Velocity of the slower molecules outside the
droplet 10 units
Average velocity outside the droplet 20 units
Average velocity within the droplet 10 units
9
Latent Sensible Heat

• Heat energy, which is a measure of molecular
  motion, moves between water's vapor, liquid, and
  ice phases.
• As water moves toward vapor it absorbs latent
  heat to keep the molecules in rapid motion and
  vice versa.
• ___________ has a cooling effect.
• ___________ is a warming effect.

10
Heat Energy for Storms

• Latent heat released from the billions of vapor
  droplets during condensation and cloud formation
  fuels storm energy needs, warms the air, and
  encourages taller cloud growth.
• An average thunderstorm contains several thousand
  metric tons of water.
• Condensing 1 kg of water releases 2.5 x 106 J
  (1 watt 1 Joule/sec) of latent heat energy .
• An average thunderstorm containing around 1500
  tons of water will release 3.45 billion Joules of
  energy.

11
Heat is transferred 3 ways

• _________ transfer of heat from molecule to
  molecule with in a substance contact is needed
• _________ transfer of heat by the mass movement
  of a fluid (in the vertical) similar to a pot of
  boiling water
• Advection - transfer of heat or properties from
  one part to another part (in the horizontal)
  usually by the prevailing wind
• _________ transfer of energy from one object to
  another without spaces in between heated no
  contact is necessary

12
Conduction - Heat Transfer

• Conduction of heat energy occurs as warmer
  molecules transmit vibration, and hence heat, to
  the adjacent cooler molecules.
• Warm ground surfaces heat overlying air by
  conduction.
• Air is an _______ ______ conductor of heat.
• Heat transferred by conduction always flows from
  warmer to colder regions.
• Typically, the greater the temperature
  difference, the faster the heat transfer.

13
Heat Conductivity
Poor
Good
14
Convection - Heat Transfer

• Convection is heat energy moving as a fluid from
  hotter to cooler areas.
• Warm air at the ground surface rises as a thermal
  bubble, expends energy to expand, and hence
  cools. This is called convective circulation or
  a thermal cell.
• Any rising air bubble will _____ and cool, and
  any sinking air bubble will _____ and warm.
• As the air parcel rises to a a lower pressure
  region, in order to equalize the pressure on the
  inside, the parcel molecules inside push the
  parcel wall outward and expanding it.

15
How does radiation transfer energy from one
object to another without spaces in between
heated?

• Radiant energy or radiation travels in the form
  of waves.
• Energy is _____when they are absorbed by an
  object.
• These waves are called __________ waves because
  it has magnetic and electrical properties.
• In space, void of air molecules, EM waves travel
  at 3 x 105 km s-1 or 186,000 miles per second.

16
Radiation - Heat Transfer

• Waves can come in different sizes. _____
  wavelengths have _____ energy levels.
• __________ (?) is a measurement of these wave
  sizes.
• All objects above 0 K release radiation, and its
  heat energy value increases to the 4th power of
  its temperature.
• example Temperature4 energy
• 2 2 2 2 16 compare to 4 4 4 4
  256

17
3 important facts about radiation

• All things emit radiation
• _____does not matter.
• The wavelengths of radiation that an object emits
  are mainly dependent on the objects temperature.
• Temperature is __________ proportional to the
  wavelength -- the higher the temperature of an
  object, the shorter the wavelength.
• Objects that have high temperatures emit
  radiation at a _____ rate, stronger intensity,
  and wider range than objects with lower
  temperatures.
• Suns surface temperature is greater than earths
  surface temperature therefore the sun emits more
  radiation and at more wavelengths than the
  earths surface.

18
Longwave Shortwave Radiation

• The hot sun radiates at shorter wavelengths that
  carry more energy.
• The sun maximum radiative wavelength is about 0.5
  µm. (_____ _____)
• The cooler earth only absorbs a small fraction of
  the suns radiation which is then re-radiated at
  longer wavelengths, as predicted by Wein's law.
• The earth maximum radiative wavelength is about
  10 µm. (_____)

19
Electromagnetic Spectrum

• Solar radiation is largely found in the shorter
  wavelengths such as ultraviolet, visible, and
  near infrared portions of the EM spectrum.
• Solar radiation also extends at low intensity
  into longwave regions such as far infrared,
  microwaves, and radio waves.
• 7 UV 44 VIS 37 near IR 11 far IR 1
  others 100

20

• Earths surface and the sun are considered _____
  objects. nearly 100 absorption and emission
• When the rate of absorption equals the rate of
  emission by radiation transfer only, this is
  called the radiative equilibrium state.
• So, the temperature at which this state occurs is
  known as _____ _____ _____ (RET) the earths
  RET is about 255 K

21
What is a Blackbody?Any object that is a perfect
absorber (to all radiation that strikes it) and a
perfect emitter (where the maximum radiation
possible is emitted at its given temperature).

• Does not have to be black to be considered a
  blackbody.
• Scientific equations work well with blackbody
  objects.

72 absorption
72 emission
Therefore, the object is a blackbody because its
absorption/emission efficiency is at 100.
22
So if the earths radiative equilibrium
temperature is about 255 K (0F) then, why is
this value much lower than the earths observed
temperature 288K (59F)? The atmosphere is to
blame!!!

• The earths atmosphere _____ and _____ infrared
  radiation.
• The atmosphere does not _____ like the earths
  surface (blackbody).
• The atmosphere is a _______ absorber and
  emitter of radiation.

23
Atmospheric Greenhouse Effect

• Earth's energy balance requires that absorbed
  solar radiation is emitted to maintain a constant
  temperature.
• Without natural levels of greenhouse gases
  absorbing and emitting, this surface temperature
  would be 33C cooler than the observed
  temperature.

24
Atmospheric Absorption

• Solar radiation passes rather freely through
  earth's atmosphere, but earth's re-emitted
  longwave energy either fits through a narrow
  window or is absorbed by greenhouse gases and
  re-radiated toward earth.
• As these gases absorb infrared radiation from the
  earths surface, they acquire kinetic energy
  (energy of motion).
• The different gas molecules share this energy by
  collision with adjacent air molecules, such as O2
  and N2 (poor absorbers of IR). These collisions
  increase the overall kinetic energy of the air
  which results in increase in air temperature

25
Absorption of Nitrous Oxide
------UV----------VIS--------------------------
-----------IR-------------------------------------

26
Absorption of Methane
------UV----------VIS--------------------------
-----------IR-------------------------------------

27
Absorption of Oxygen and Ozone
------UV----------VIS--------------------------
-----------IR-------------------------------------

28
Absorption of Water Vapor
------UV----------VIS--------------------------
-----------IR-------------------------------------

29
Absorption of Carbon Dioxide
------UV----------VIS--------------------------
-----------IR-------------------------------------

30
Total Absorption of the Atmosphere
31

• Atmospheric greenhouse effect is associated with
  the role of __________, _____, and other
  greenhouse gases in maintaining the earths
  averaged surface temperature higher than the
  predicted value without an atmosphere.
• __________ __________ is the region where IR
  radiation (8 11 µm) is neither
  absorbed or emitted by water vapor and CO2 and is
  freely to pass through the atmosphere.
• Clouds (good absorber of IR but poor absorber of
  visible light) can enhance the atmospheric
  gashouse effect as well by absorbing radiation
  between 8 11 µm, thereby closing the
  atmospheric window.
• Calm, cloudy night warmer temperature
• Calm, clear night cooler temperature
• Cloudy day cooler temperature
• Sunny day warmer temperature

32
Warming Earth's Atmosphere from Below

• Solar radiation passes first through the upper
  atmosphere, but only after absorption by earth's
  surface does it generate sensible heat (heat that
  we can feel and measure) to warm the ground and
  generate longwave energy.
• This heat and energy at the surface then warms
  the atmosphere from below.
• Since water vapor decreases with rapidly above
  the earth, most of the absorption occurs in a
  layer near the surface. Therefore, the lower
  atmosphere is mainly heat from below.

33
Scattered Light

• Sunlight passing through earth's atmosphere is
  deflected by gases, aerosols, and dusts in all
  directions. This distribution of light is called
  __________.
• Air molecules are smaller than visible light
  wavelengths, therefore they are better scatterers
  of shorter (blue) wavelengths than longer (red)
  wavelengths.
• At the horizon sunlight passes through more
  scatterers, leaving _____ wavelengths and redder
  colors revealed.
• The midday sun looks white due to _____
  scattering by the air molecules.

34

• At noon, the sun usually appears a bright white
  due to less scattering of the blue lights.
• At sunrise and sunset, sunlight must pass
  through a thicker portion of the atmosphere.
• As the sunlight passes through more of the
  atmosphere, much of the blue light is scattered
  out of the beam, causing the sun to appear more
  red.
• Cloud droplets scatter all wavelengths of
  visible white light about equally.
• This type of scattering by millions of tiny cloud
  droplets makes clouds appear white.

35

• Sunlight can be reflected from objects.
• _____ is the percent of radiation returning
  from a given surface compared to the amount of
  radiation initially striking the surface.
  (reflectivity of a surface)
• The earth on the average reflects about _____ of
  the suns incoming radiation back into space.
• The colors of the objects do not play a huge role
  in controlling the albedo.

36
Incoming Solar Radiation
Solar Constant 1367 W/m2

• Solar radiation is scattered and reflected by the
  atmosphere, clouds, and earth's surface, creating
  an average albedo of 30 (30 units).
• Atmospheric gases and clouds absorb another 19
  units, leaving 51 units of shortwave absorbed by
  the earth's surface.

37
Earth-Atmosphere Energy Balance
Absorb by greenhouse gases

• Earth's surface absorbs the 51 units of shortwave
  and 96 more of longwave energy units from
  atmospheric gases and clouds.
• These 147 units gained by earth are due to
  shortwave (sun) and longwave (atmosphere)
  greenhouse gas absorption and emittance.
• Earth's surface loses 117 units through emission
  therefore producing 30 units of surplus from the
  earths surface, while the atmosphere generates
  30 units of deficit. The balance is created from
  heat transfer processes such as conduction,
  convection, and latent heat release.

38
Average annual incoming solar radiation absorbed
and outgoing infrared radiation from the earth
and the atmosphere
Surplus heat is transported from the equator to
the pole regions.
39
Four factors that determine how much radiation is
received by the Earth at a given location

• Sphericity of the Earth
• Axial Tilt
• Elliptical Orbit of The Earth
• Daily Earth Rotation

40
Seasons Sun's Distance
Earth's surface is 5 million kilometers further
from the sun in summer than in winter, indicating
that seasonal warmth is controlled by more than
solar proximity.
41
Seasons Solar Intensity

• Solar intensity, defined as the energy per area,
  governs earth's seasonal changes.
• A common unit for solar intensity is Watts per
  meter square (Wm-2). The solar intensity hitting
  directly at the top of the atmosphere is about
  1380 Wm-2.
• A sunlight beam that strikes at an angle is
  spread across a greater surface area, and is a
  less intense heat source than a beam impinging
  directly.

42
Solstice Equinox
Equal Amount
Direct Sunlight at 23.5S
Direct Sunlight at 23.5N
Equal Amount

• Earth's tilt of _____ and revolution around the
  sun creates seasonal solar exposure and heating
  patterns.
• A solstice tilt keeps a polar region with either
  24 hours of light or darkness.
• A equinox tilt perfectly provides _____ hours of
  night and _____ hours of day for all non-polar
  regions.

43
Earth's Tilt

• Earth's __________ and _____ combine to explain
  variation in received solar radiation.
• Notice the difference between the top and bottom
  of the atmosphere at different latitudes.

44

• March 20th
• Vernal Equinox
• June 21st
• Summer Solstice
• Sept 22nd
• Autumnal Equinox
• Dec 21st
• Winter Solstice

45
Longer Northern Spring Summer
Faster
Slower

• Earth reaches its greatest distance from the sun
  during a _____ _____, and this slows its speed of
  revolution.
• The outcome is a spring and summer season 7 days
  longer (Mar 20 to Sept 22) than that experienced
  by the southern hemisphere.

46
Local Solar Changes

• The apparent path of the sun across the sky as
  observed at different latitudes during the
  solstices and equinoxes.
• Summer noon time sun in the northern
  mid-latitudes is also higher above the horizon
  than the winter sun.