1. Lab #3: Radiation Balances and Winds

2. Crash Course on Radiation
For temperature, we use units of kelvin.
K = °C + 273
K = 25°C + 273
K = 298k
No degree symbol with kelvin.

3. Crash Course on Radiation
Everything with a temperature emits electromagnetic radiation.
The amount of radiation emitted by an object is dependent on its temperature
There are multiple ways to think about electromagnetic radiation, all of which are correct.
As heat – heat energy is just a form of energy, radiation is just emission of heat energy.
As light – light that we see with our eyes is electromagnetic radiation over a specific range of wavelengths (this definition gets into types of radiation)
As particles/waves – fundamentally, electromagnetic radiation manifests as packets of energy (called photons), the amount of energy per photon is defined by the emitting body’s temperature and is correlated with the wavelength the photon vibrates at as it moves at the speed of light.
Cooler bodies emit photons with less energy vibrating at longer wavelengths. Warmer bodies emit photons with more energy vibrating at shorter wavelengths.

4. Crash Course on Radiation
Amount of Radiation
Sun’s temp = ~6000k, ~5700°C
Earth’s temp = ~290k, ~20°C
Wavelength (cm)

5. Stefan-Boltzmann Law L↑ = εσT4
Relates a body’s temperature to the amount of radiation emitted.
L↑ = εσT4
T, in Kelvin
ε, Emissivity (ranges from 0-1)
σ, 5.67*10-8 W m-2 k-4

6. Stefan-Boltzmann Law L↑ = εσT4 To find radiation emitted.
ε: 0.91
σ: 5.67*10-8 W m-2 k-4
L↑ = (0.91)*(5.67*10-8)*(293)4
L↑ = 380 W m-2

7. Stefan-Boltzmann Law L↑ = εσT4 To find temperature of the emitter.
Question #4
L↑ = εσT4
L↑: 355 W m-2
ε: 0.92
σ: 5.67*10-8 W m-2 k-4
355 = (0.92)*(5.67*10-8)*T4
355 = (5.216*10-8)*T4
= T4
( )0.25 = T
287.22k = T

8. Longwave vs. Shortwave Radiation
Shortwave: radiation emitted at the Sun’s temperatures.
Longwave: radiation emitted at Earth’s temperatures.

9. Earth’s Radiation Budget
Question #3/5
Net Radiation = Net Shortwave + Net Longwave
Q* = K* + L*
Q* = (K↓ - K↑) + (L↓ - L↑)
K* = K↓ - K↑
L* = L↓ - L↑

10. Earth’s Radiation Budget
Albedo: Measure of reflectivity (zero to one)
α = K↑/ K↓
Question #3
K↑ = α*K↓
Albedo used in question 3.

11. Yellow is Shortwave (K*)
Red is Longwave (L*)

12. Earth-Atmosphere (E-A)
Subtract the outgoing (upward arrows) from the incoming (downward arrows) to get net radiation for each column. The final column is net all-wave (Q*), Q* = net longwave (L*) + net shortwave (K*).
Net all wave radiation from the top of the atmosphere should be zero (conservation of energy) – this is the bottom right column.

13. Earth (E)

14. Atmosphere (A)
If the long or shortwave radiation makes a “stop” in the atmosphere, it is included in the “atmosphere column”.
Make sure you show all your work – add and subtract all components (even if it is being reflected).

15. Surface Wind Analysis High pressure: winds blow outwards clockwise
Low pressure: winds blow inward counterclockwise

16. Surface Wind Analysis
Strongest winds, where isobars (lines circumnavigating the map) are closest together
Weak winds where isobars are far apart