Climate

1
Climate

• Earths Radiation Balance

2
Solar Radiation Budget

• Life on earth is supported by energy from the sun
• Energy from the sun is not simply absorbed by
  earth, but also retransmitted
• Without retransmission, all water would boil away
  all life would fry
• The balance between absorption and retransmission
  of the suns energy is called the radiation budget

3
Basic Processes Governing the Radiation Balance
4
Insolation

• Insolation measures the amount of energy coming
  from the sun via short wave radiation.
• Measured in watts/sec
• Top graphic is winter
• Bottom graphic is summer

5
Annual Insolation
6
Albedo

• Degree of reflectivity of the Earth-Atmosphere
  system (ranges from 0-1)
• Ice and sand are highly reflective (high albedo)
• Oceans and forests dont reflect much (low
  albedo)
• top-winter
• bottom-summer

7
Annual Albedo
8
Short Wave Reflected Radiation

• Measures the amount of the suns energy that is
  reflected due to the albedo
• Measured in watts/m2
• Does not affect processes on earth since it is
  never absorbed
• Top-winter
• Bottom-summer

9
Annual Short Wave Reflection
10
Short Wave Absorption

• The energy absorbed by the earth-atmosphere
  system
• Primary cause of earths surface temperature

11
Annual Short Wave Absorption
12
Surface Temperature

• Provides a measure of the temperature all over
  the Earth
• Temperatures measured in Kelvin
• Heat at the surface is translated into long wave
  radiation

13
Annual Surface Temperature
14
Radiation Spectra for Sun Earth

• The wavelength energy emitted by a body is
  inversely related to the temperature of the body.
• ?(nm) 2.9 x 106/T

15
Outgoing Long Wave Radiation

• Measures the amount of energy leaving the Earth
• Results from the surface temperature
• Also called terrestrial radiation
• Measured in watts/m2

16
Annual Long Wave Terrestrial Emission
17
Net Radiation

• Difference between incoming and outgoing
  radiation
• Over time and space this is zero

18
Annual Net Radiation
19
Greenhouse Amount

• Amount of energy retained by Earths atmosphere
• This storage of energy is called the Greenhouse
  Effect
• Necessary for maintaining life on Earth

20
(No Transcript)
21
Greenhouse Percent

• Amount of energy stored in atmosphere
• Shows Greenhouse Effect as a fraction of the
  total possible energy that could be stored in the
  atmosphere
• Useful for detecting changes over time
• Annual graphic

22
(No Transcript)
23
Partitioning of Incoming SW Radiation

• 19 units absorbed in atmosphere to become heat
  LW radiation
• 2 units by ozone
• 17 units by clouds gases
• 23 units scattered then absorbed as diffused
  insolation
• 28 units directly absorbed at surface
• Total absorbed 70 units

24
Processes of Retransmission

• Three modes
• latent heat (drives hydrological cycle)
• sensible heat (atmosphere heated by updrafts)
• radiation of IR into space
• Total of 70 units emitted

25
Comparison of Radiation Budgets of the
Terrestrial Planets

• Compare Earth, Venus Mars
• Earth Venus have similar mass dimensions
  Mars 10 Earths mass half as large
• Temperatures expected to be in the order
• Venus gt Earth gt Mars
• Observed
• Earth (255 K) gt Venus (234 K) gt Mars (217 K)

26

• The surface temperatures bear little resemblance
  to their effective temperatures
• Venus (427oC) gt Earth (15oC) gt Mars (-53oC)
• Due to greenhouse effect
• Venus
• extensive atmosphere (100x more mass than
  Earths)
• composed mainly of CO2, H2O, SO2
• Mars
• atmosphere contains more CO2 Earths
• has 100x less water than Earths atmosphere