Why temperature decreases with altitude ?

Question

When we take a blanket at room temperature and wrap it around ourselves, we become warmer than if we were uncovered by the blanket.

When we take a blanket at room temperature and wrap it around an ice cube, would it melt faster or slower than if the ice cube was uncovered by the blanket?

Answer 1

The expansion comes in because the hot air that is heated by the ground rises. However as it rises it's volume increases and therefore it's temperature decreases. So the decrease in temperature with height is indeed due to expansion, but this is only the case because air is heated from below by the ground.