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If hot air rises, why is it generally hotter down low and cooler up high?
Thanks Bruce
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Hot air does rise indeed as it is less dense than cool air. As the warm air rises, it expands and cools. That cool air will then sink down again.
If you think of a bicycle pump and you put your hand in front of it while you pump out air, the air comes out and it's cool. But when you pump your tire, you can feel that air inside is warm! As the air comes out to the free air (where your hand is, no tire), it expands and cools. When the air is compressed inside the tire, it is warmer.
We also know, that as you climb higher in the atmosphere the pressure drops. Our ears pop sometimes when we hike up a tall mountain or fly on an airplane. As pressure decreases so does temperature. If you remember back to our friend the Ideal Gas Law of PV=NRT where P equals pressure and T equals temperature, that equation needs to stay balanced. So as the left side (Pressure) decreases, the temperature has to decrease also. Or you could say that the pressure is directly proportional to the temperature.
Now that's generally, there are times when at higher elevations, the temperature can be higher than at lower elevations, this is called an inversion. We have these a lot in the winter when temperatures are cooler below and higher above, this is when our pollution gets stuck. The cooler air below cannot rise into that warmer air above. The top of the the troposphere (the layer of the atmosphere where weather happens) and the beginning of the tropopause is also marked by an inversion as well.
Answered by KSL Meteorologist Dina Freedman
