Planetary Engineering 1
Climate Modeling
Class Exercise
Zero-Dimensional GEBM
Global energy balance: Radiative equilibrium (in = out)
Goal: Planets’ Temperatures
Important Fact: Sun heats less the farther it is.
Important Factor: How does S change with orbit?
Recall from Topic 1:
Change in solar flux: sun  earth
At photosphere surface,
solar flux ~ 6.2.107 W-m-2
At Earth’s orbit, solar flux ~ 1360 W-m-2
Two Spheres Surrounding Sun
Total energy flux the same through each sphere
R2 = 2 x R 1
R2
R1
The same area at R2
intercepts only 1/4 of
energy it intercepts at R1
 Flux decreases as R-2
For Earth
Global energy balance: Radiative equilibrium (in = out)
Thus, TRAD = 255 K
What about other planets?
How does Trad change with orbit?
What about other planets?
How does Trad change with orbit?
Planet
Distance
from sun
[A.U.]
Albedo
Mercury
0.39
0.06
Venus
0.72
0.76
Earth
1.00
0.30
Mars
1.52
0.16
Jupiter
5.20
0.51
Saturn
9.54
0.50
Uranus
19.18
0.66
Neptune
30.06
0.62
Outgoing IR
Trad
[W-m2]
[K]
238
255
For Mars
Tsurface ≈ Trad. How warm can we make its surface?
For Mercury
Tsurface ≈ Trad. How cool can we make its surface?
Venus?
Why can’t we adjust Venus the same way?
End
Planetary Engineering 1