True, the radius will increase because of The Law of Charles and Gay Lussac (not Boyle's law as in another reply). And the moment of inertia would increase, if you assume that the entire atmosphere moves along with the solid Earth. If the atmosphere stays still relative to the rotation of the Earth, than an increase in its radius won't affect the moment of inertia, because it isn't rotating.
So of key importance is how still the atmosphere stays. Does it move primarily with the rotating Earth beneath it, or does the Earth rotate in a relatively still atmosphere? I know it experiences the Coriolis effect, and so moves differently than the ground beneath it, but which behavior prevails: the drag due to the Coriolis effect, or the drag due to the ground beneath it?
Slashdot Mirror
True, the radius will increase because of The Law of Charles and Gay Lussac (not Boyle's law as in another reply). And the moment of inertia would increase, if you assume that the entire atmosphere moves along with the solid Earth. If the atmosphere stays still relative to the rotation of the Earth, than an increase in its radius won't affect the moment of inertia, because it isn't rotating.
So of key importance is how still the atmosphere stays. Does it move primarily with the rotating Earth beneath it, or does the Earth rotate in a relatively still atmosphere? I know it experiences the Coriolis effect, and so moves differently than the ground beneath it, but which behavior prevails: the drag due to the Coriolis effect, or the drag due to the ground beneath it?