Lecture 4

Question 0

State Stefan’s Law

Answer 0

The intensity of radiation emitted by a body increases in proportion to the absolute temperature of the body.

Question 1

What sort of energy does Earth receive from the sun?

Answer 1

Short wave radiation

Question 2

What is the formula explained by Stefan’s law?

Answer 2

Intensity equals Stefan-Boltzman constant times the fourth power of absolute temperature.
I = s*(T^4)

Question 3

What spectrum of energy does the sun emit?

Answer 3

Visible light and UV

Question 4

In what spectrum does Earth emit energy?

Answer 4

Infrared

Question 5

Are you psyched about Stefan’s Law?

Answer 5

Yes!

Question 6

What two factors influence the heat budget of Earth?

Answer 6

Albedo and Greenhouse gas effect

Question 7

If an object’s albedo equals 1, what does it mean?

Answer 7

The object is a perfect reflector.

Question 8

If an object’s albedo equals 0, what does it mean?

Answer 8

The object is a perfect absorber.

Question 9

What is the albedo of Earth?

Answer 9

0.3

So Earth reflects about 30% of incoming radiation.

Question 10

Which one has the highest albedo in the following?
Sea surface
Bare soil
Forrest
Snow

Answer 10

Snow 0.75~0.95

Question 11

Which one has the least albedo in the following?
Sea surface
Bare soil
Forrest
Snow

Answer 11

Sea surface <0.1

Question 12

How does greenhouse effect work?

Answer 12

Radiation reflected or reemitted from the surface of the Earth is absorbed by greenhouse gasses in the atmosphere, keeping the temperature near the surface warm.

Question 13

Which gas contributes the most for the greenhouse effect?

Answer 13

Water vapor!!

Question 14

If it were not for the greenhouse effect, what would be the average temperature of Earth?

Answer 14

-18°C Brrrr!!

Question 15

What is the average temperature of Earth on surface?

Answer 15

15°C

Question 16

State in words the Earth’s overall eat budget.

Answer 16

Incoming solar radiation = outgoing Earth radiation

Question 17

Why are latitudinal differences in heat budget?

Answer 17

Because the earth’s axis is tilted. N hemisphere is gets intense solar radiation in July, whereas S hemisphere gets oblique solar radiation in the same month.

Question 18

During august, which part of Earth receives net surplus of heat?

Answer 18

Northern hemisphere

Question 19

During January, which part of Earth receives net surplus of heat?

Answer 19

Southern hemisphere

Question 20

Which part of Earth receives net surplus of heat year-around?

Answer 20

Equatorial regions