W4: L2 *check notes

Question 1

What is thermodynamics? what are the three main variables that describe atmospheric therodynamic state?

Answer 1

The study of heat and chnage
Temeprature, pressure, density

Temp: measure of molecular motion
Pressure- force per unit area exerted by air molecules
Density- mass per unit volume of air

Question 2

What is temperature

Answer 2

• A measure of hotness of coldness.
• For a gas, it is porportional to the average kinetic energy of its vibrating molecules

Unit: Kelvin

Measured by a thermometer

Question 3

How does tempertaure increase?

Answer 3

• compressing a gas (under high pressure) , increases molecular collisions (molecules vibrate more vigorously) ,the kintetic energy, which increases temperature

Question 4

What is the ‘earths temperature’- what are we looking at?

Answer 4

• the time and space average near surface temperatures

Question 5

What are the temperature scales?

Answer 5

Kelvin (K) measures absolute temperature.
0 K = “absolute zero” → molecules stop moving completely.
This is the bottom of the temperature scale (you cannot go below it).

Celsius (°C) was designed around water:
0 °C = freezing point of water
100 °C = boiling point of water

The size of 1 °C is the same as 1 K.
→ A change of +10 °C = a change of +10 K.- for chnage or difference in temperature, celcius and kelvin are exactly equal
The only difference is the starting point (the zero).
0 °C = 273.15 K

Formula:
TK=T°C+273.15

Ceclius temp is defined as kelvin temp offset, so that water freezes at 0 degrees celcius which is 273,15K

In physics and climate equations (like the Stefan–Boltzmann law), you must use Kelvin, because you can’t have negative temperatures when you’re talking about radiation and molecular motion.
Celsius is just for human convenience.

Question 6

hat is

What is Kelvin temperature chnage defined as

Answer 6

Step 1. Celsius scale
Defined so that:
Water freezes at 0 °C
Water boils at 100 °C
So there are 100 equal steps between freezing and boiling.
Each step = 1 °C.
Step 2. Kelvin scale
Defined in terms of absolute temperature (starts at absolute zero).
But the size of the step (the unit) was chosen to match Celsius.
So:
273.15 K = 0 °C (freezing point)
373.15 K = 100 °C (boiling point)
Between those two points, there are also 100 equal steps.
Step 3. Why the “1/100” wording appears
The freezing → boiling interval of water is the reference interval.
That interval is divided into 100 parts.
One part = 1 K = 1 °C.
So a 1 Kelvin temperature change = 1% of that interval.

Question 7

Conceptual vs quantitative models

Answer 7

COonceptual models: idea of how earths temperature is determined
Quantitative model: develops equations based on cocneptual model
AIm: describe the earths average temperature chnage over space and time

Question 8

Energy balance of earth

Answer 8

Principle: Incoming energy ≈ Outgoing energy.
○ If imbalance → Earth’s temperature changes.
amount excess energy coming in to relative leaving determines rate temp chnage

Incoming (shortwave radiation): from the Sun.
○ Some reflected (albedo: clouds, surface, aerosols).
○ Remainder absorbed by Earth’s surface → re-radiated.

Outgoing (longwave radiation): Earth radiates heat according to Stefan-Boltzmann law.

Question 10

Troposhere vs statosphere heating

Answer 10

Troposphere (lowest layer):
- Cannot absorb most shortwave sunlight.
- Heated from below, by Earth’s surface re-emitting IR radiation.
- This is why temperature decreases with altitude in the troposphere.

Stratosphere (above troposphere):
- Contains ozone (O₃), which absorbs high-energy UV radiation from the Sun.
- Heated from above, so temperatures increase with altitude her

Question 11

Explain electromagnetic radiation- sun vs earth

Answer 11

Electromagnetic Radiation

EM waves: electric + magnetic fields, travel at speed of light c = 3 × 10⁸ m/s.

Waves defined by different wavelengths

Wavelength (λ): distance between peaks.
Frequency (f): cycles per second.
f=c/λ

Short λ → high f → high energy
Long λ → low f → low energy

• all objects emit radiation over wavelengths
• spread of wavelengths and amount of energy in emitted radiation depends on temp of the objects
• emission from sun invludes visible light (green) and hugher energy (more dangerous) ultraviolet radiation

The wavelength λmax of highest energy emission for a body with
temperature T , is:
λmax = C/T
C = 2.897 × 10−3m· K Wien’s constant

Hotter objects → shorter λ → more energetic radiation.
Sun (~6000 K) → visible/UV (green/ yellow)
Earth (~300 K) → infrared

.

Question 12

Explain the different ways that radiation can take place

Answer 12

Reflected: bounce off or away from a surface (Earth, cloud, gas paricle)

Scattered: deviate away from original straight line parts(a type of refelction)

Absorbed: or taken up by an object

Question 13

Rayleigh vs mie scattering * check this

Answer 13

1. Rayleigh Scattering

Particle Size: Particles are much smaller than the wavelength of light (e.g., air molecules like N₂ and O₂).

Direction: Scatters light almost equally in all directions (isotropic).

Wavelength Dependence: Scatters shorter wavelengths (blue and violet light) much more efficiently than longer wavelengths (red light).

Why the sky is blue: The blue/violet light from the sun is scattered in all directions by air molecules, filling the sky with blue light.

Why sunsets are red: At sunrise/sunset, sunlight passes through more atmosphere. Most of the blue light is scattered away from your line of sight, leaving the longer red and orange wavelengths to dominate the light that reaches you directly.

2. Mie Scattering

Particle Size: Particles are approximately the same size or larger than the wavelength of light (e.g., aerosols, dust, pollen, water droplets in clouds).

Direction: Scatters light primarily in a forward direction.
Wavelength Dependence: Scatters all wavelengths of visible light more equally (less selective than Rayleigh scattering). This is why clouds, which are made of large water droplets, appear white.

Influence: The effect becomes stronger as the particle size increases

Question 14

Radiation, conduction and convection * checkl

Answer 14

• 3 processes through whioch energy is transferred into and within the atmosphere

RadiationL energy radiated out of bodies and atmospheric particles, based on temp and emissivity

Conduction: transfer within a medium and at its boundary through collison of particles

Convection: heated gases expand, become less dense and more buoyant, rsing and trasnferring energy upwards