Projects

1. The moon with no heat transport. The layer model assumes that the temperature of the body in space is all the same. This isn't really very accurate, as you know that it's colder at the poles than it is at the equator. For a bare rock with no atmosphere or ocean, like the Moon, the situation is even worse, because fluids like air and water are how heat is carried around on the planet. So let's make the other extreme assumption, that there is no heat transport on a bare rock like the Moon. What is the equilibrium temperature of the surface of the Moon, on the equator, at local noon, when the Sun is directly overhead? What is the equilibrium temperature on the dark side of the Moon?

2. A two-layer model. Insert another atmospheric layer into the model, just like the first one. The layer is transparent to visible light but a blackbody for IR

a. Write the energy budgets for both atmospheric layers, for the ground, and for the Earth as a whole, just like we did for the one-layer model.

b. Manipulate the budget for the Earth as a whole to obtain the temperature T2 of the top atmospheric layer, labeled atmospheric layer 2 in Fig. 3.5. Does this part of the exercise seem familiar in any way? Does the term skin temperature ring any bells?

c. Insert the value you found for T2 into the energy budget for layer 2, and solve for the temperature of layer 1 in terms of layer 2. How much bigger is T1 than T2?

d. Now insert the value you found for T1 into the budget for atmospheric layer 1, to obtain the temperature of the ground, Tground. Is the greenhouse effect stronger or weaker because of the second layer?

Visible IR

Visible IR

Fig. 3.5 An energy diagram for a planet with two panes of glass for an atmosphere.
Fig. 3.6 An energy diagram for a planet with an opaque pane of glass for an atmosphere.

3. Nuclear Winter. Let's go back to the one-layer model, but let's change it so that the atmospheric layer absorbs visible light rather than allowing to pass through (Fig. 3.6). This could happen if the upper atmosphere were filled with dust. For simplicity, let's assume that the albedo of the Earth remains the same, even though in the real world it might change with a dusty atmosphere. What is the temperature of the ground in this case?

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Responses

• Elena
What is the equilibrium temperature of the moon at local noon?
8 years ago
• Dennis
What is the equilibrium temperature on the dark side of the moon?
8 years ago