Chapter 2 part B

Question 1

What is the main reason greenhouses hot?

Answer 1

Greenhouses are hot mainly because heat is trapped by the lid at the top (no convection to atmosphere above)

Question 2

How does solar radiation affect the temperature in greenhouses?

Answer 2

Solar radiation absorbed but heat is unable to “vent” upward (no convection to atmosphere above)

Question 3

Greenhouse VS Atmospheric greenhouse effect

Question 4

Why are “greenhouse” gasses considered selective absorber?

Answer 4

“Greenhouse” gases are generally poor shortwave absorbers but good longwave (infrared light) absorbers

Question 5

Where does O3 absorb best?

Answer 5

O3 absorbs best in UV
(Ozone “layer” in stratosphere)

Question 6

How is IR radiation able to escape to space?

Answer 6

Two “atmospheric windows” between 8 –13 μm

Question 7

Why are certain substances greenhouse gases and others are not (ex: molecular oxygen (O2) and nitrogen (N2))?

Answer 7

Molecular properties of tri-and multi-atomic gases allows for stretching and bending vibrations in the “right” wavelength range for infrared (longwave) absorption
(ex: H20)

Question 8

Why is the albedo of thick clouds higher?

Question 9

How do thick clouds look compared to thin clouds?

Question 10

What would happen if equator to pole heat transfer was not steadying climate?

Answer 10

equator would forever heat up and the polar regions would cool.

Question 11

Is IR radiation reflected?

Answer 11

IR radiation is not reflected but is absorbed and re-emitted by the atmosphere

Question 12

Are all greenhouse gases equally efficient at absorbing LW radiation (on per-molecule basis)? → Global warming potential?

Question 13

What reflection / transmission / absorption properties depend are related to a cirrus type of cloud?

Answer 13

thin, high-altitude (cold) clouds, effectively transmit shortwave but absorb some infrared radiation (enhances greenhouse effect)

Question 14

What reflection / transmission / absorption properties depend are related to low-altitude clouds ?

Answer 14

e.g.stratocumulus): more scattering/reflection of shortwave and longwave radiation. Re-emission temperature (of clouds) closer to that of surface temperature

Question 15

What is electromagnetic radiation (EM) and what causes it?

Answer 15

EM radiation is emitted by all objects warmer than absolute zero (T > 0 K). It is caused by the random vibrations of electrons and other charged particles and propagates as electromagnetic waves or photons.

Question 16

What is the relationship between wavelength (λ), frequency (f), and phase speed (v)?

Answer 16

They are related by the equation: v = f × λ. For electromagnetic waves, phase speed is the speed of light (c ≈ 3.0×10^8 m/s). Therefore, λ = c/f and f = c/λ.

Question 17

What is radiant energy per photon and how is it calculated?

Answer 17

Radiant energy per photon is calculated using the equation RE = h × c/λ, where h is Planck’s constant (6.626 × 10⁻³⁴ J·s), c is the speed of light, and λ is the wavelength

Question 18

How does wavelength relate to frequency and energy?

Answer 18

Higher frequency corresponds to a shorter wavelength and higher energy, while lower frequency corresponds to a longer wavelength and lower energy.

Question 19

What is a black body, and how does it differ from a white body?

Answer 19

A black body is an idealized object that absorbs all incident electromagnetic radiation and emits the maximum energy possible at its temperature. A white body, on the other hand, reflects all incident radiation uniformly in all directions.

Question 20

What is the Stefan-Boltzmann law and how does it relate to temperature?

Answer 20

The Stefan-Boltzmann law states that the total radiant energy emitted by a black body per unit time per unit area is proportional to the fourth power of its absolute temperature (T): E = σT⁴, where σ is the Stefan-Boltzmann constant (5.67×10^−8 W m^−2 K^−4).

Question 21

What does Wien’s Displacement Law describe?

Answer 21

Wien’s Law describes the relationship between the peak wavelength (λmax) of radiation emitted by a black body and its absolute temperature (T): λmax = const./T, where the constant is 2897 μm·K.

Question 22

How do the Sun and Earth differ in terms of radiation?

Answer 22

The Sun emits shortwave (SW) radiation with a peak wavelength around 0.5 μm (green light), while the Earth emits longwave (LW) radiation with a peak wavelength around 10 μm (infrared).

Question 23

What is Rayleigh scattering and why is the sky blue?

Answer 23

Rayleigh scattering occurs when light is scattered by particles much smaller than its wavelength. Shorter wavelengths (blue light) are scattered more effectively than longer wavelengths, making the sky appear blue.

Question 24

What is albedo, and how does it vary with surface types?

Answer 24

Albedo is the fraction of incident shortwave radiation reflected by a surface. Snow has a high albedo (reflects up to 95%), while water bodies absorb up to 98% of radiation, depending on the angle of incoming light.

Question 25

What are selective absorbers and how do greenhouse gases affect Earth’s temperature?

Answer 25

Selective absorbers, like greenhouse gases (CO₂, H₂O), absorb longwave (infrared) radiation but allow shortwave radiation to pass through. This absorption and re-radiation of infrared radiation cause the greenhouse effect, warming Earth’s surface.

Question 26

What is the greenhouse effect and how does it affect Earth’s temperature?

Answer 26

The greenhouse effect occurs when greenhouse gases absorb longwave radiation emitted by Earth and re-radiate it back to the surface. This traps heat and increases Earth’s surface temperature.

Question 27

What is the difference between a clear and cloudy night in terms of temperature?

Answer 27

Cloudy nights are warmer because clouds absorb and re-emit infrared radiation back to the surface, trapping heat, whereas clear nights allow more heat to escape into space.

Question 28

What are feedback mechanisms in the context of global warming?

Answer 28

Positive feedbacks, like increased water vapor or methane release, amplify warming. Negative feedbacks, such as blackbody radiation (increased infrared emission with temperature), act to cool the surface.