// lecture 05

Question 1

factors that influence climate at a given place:

Answer 1

sunshine (and latitude), topography/mountains, proximity to oceans and large lakes, ocean currents, presence of trees/vegetation.

Question 2

energy from the sun is

Answer 2

electromagnetic radiation. goes through space at the speed of light. either absorbed or reflected once it gets to earth.

Question 3

radiation with shorter wavelengths are

Answer 3

more energetic.

Question 4

shortest wavelength to longest wavelength:

Answer 4

gamma rays, x-rays, ultraviolet (UV) radiation, visible light, infrared radiation, microwaves, and radiowaves.

Question 5

the sun emits:

Answer 5

• visible light.
• near infrared radiation (infrared with very short wavelength, but longer than visible).
• small, but dangerous, amount of ultraviolet radiation.

these three bands together are called “shortwave radiation” or “solar radiation.”

Question 6

insolation

Answer 6

the amount of solar radiation energy coming in.

Question 7

by the time it gets to the top of the atmosphere, the sun shines at a strength of

Answer 7

1360 watts per square meter.

Question 8

1360 W/m^2 is roughly what’s experienced in the

Answer 8

tropics when the sun is directly overhead.

Question 9

if the area is perpendicular to the solar beam,

Answer 9

then the solar energy per unit area is maximized.

Question 10

solar x exposure area

Answer 10

sweat x skin area.

Question 11

the average incoming solar radiation is

Answer 11

340 W/m^2, which is exactly 1/4 of 1,360 W/m^2.

Question 12

high latitudes get less

Answer 12

direct radiation, which spreads out more.

Question 13

shadow area of a sphere (a circle) is

Answer 13

1/4 of the surface area of a sphere 4pir^2. shadow area = pir^2.

Question 14

only ___ of solar radiation gets absorbed in the ____

Answer 14

20%, atmosphere; 50%, surface; and 30%, reflected back to space.

Question 15

albedo

Answer 15

fraction of incident light that’s reflected away. ranges from 0 (no reflection) to 1 (all gets reflected).

Question 16

human eye sensitivity is most to

Answer 16

wavelengths around 550 nanometers. when light levels are low, it shifts to around 500 nanometers.

Question 17

solar emission peaks in the

Answer 17

blue region of visible radiation, which is a big part of the solar emission.

Question 18

near infrared also constitues an

Answer 18

important energy flux.

Question 19

albedo values for earth:

Answer 19

• cloud albedo varies from 0.2 to 0.7. thicker clouds have higher albedo.
• snow albedo ranges from 0.4 - 0.9 (depends on age) and ice is about 0.4.
• ocean is < 0.1, forests are 0.15, and deserts are 0.3.

Question 20

30% of incoming solar radiation is reflected away by:

Answer 20

15% from clouds, 8% from the surface, and 7% by the atmosphere (things like dust from deserts and air pollution are key).

Question 21

Earth Radiation Budget Experiment

Answer 21

measured Earth’s albedo from a system of orbiting satellites.

Question 22

total absorbed solar radiation is

Answer 22

70% of the incoming solar radiation because 30% is reflected away. 70% of 340 W/m^2 = 240 W/m^2.

Question 23

earth loses energy through

Answer 23

infrared radiation (longwave radiation)

Question 24

everything emits radiation, which depends

Answer 24

partly on the substance, but mostly on temperature.

Question 25

thermal night vision technology

Answer 25

detects longwave radiation.

Question 26

higher temperature =

Answer 26

more radiation and more energetic radiation (shorter wavelength).

Question 27

the earth is heated by tje

Answer 27

sun (shortwave radiation) and it loses energy by longwave radiation (out to space).

Question 28

if the energy (solar radiation) into a system (Earth) is greater than

Answer 28

the energy out (outgoing longwave radiation), the temperature will increase, which results in an increase of energy out (longwave radiation). this will happen until E in = E out (energy balance).

Question 29

global warming…

Answer 29

upsets the energy balance of the planet.

Question 30

if there was no atmosphere for energy balance to occur,

Answer 30

the mean temperature of the earth would be -18 C.

Question 31

greenhouse effect:

Answer 31

all longwave radiation doesn’t escape directly to space.

Question 32

Stefan-Boltzmann law

Answer 32

• a body emits as the fourth power of its temperature in Kelvins.
• Kelvin is the absolute temperature scale 0 C = 273 K.
• the hotter an object, the more radiation it emits: blackbody emission = sigma T^4 where sigma = 5.67 x 10^-8 W m^-2 K^-4.
• the basic way earth stabilizes its temperature is by getting hotter and emitting more energy to space.

Question 33

the temperature of a black body that emits the same amount of longwave radiation that the earth needs to emit to balance its absorbed solar radiation

Answer 33

absorbed solar radiation = emitted longwave radiation 5/4(1 - albedo) = sigma T^4.

Question 34

greenhouse gases block longwave radiation from

Answer 34

escaping directly back to space. these gases re-radiate both upward and downward. the extra radiation causes additional warming of the surface.

Question 35

greenhouses gases cause the

Answer 35

outgoing radiation to happen at higher levels (no longer at the surface). air gets colder as you go upward, so the radiation space is much less (colder -> less emission).

Question 36

atmosphere and surface are black bodies for

Answer 36

terrestrial. atmosphere is transparent to solar.