If hot air rises, why is it colder at higher altitudes? ?

Question

If hot air rises, why is it colder at higher altitudes? ?

Answer 1

Firstly, the concept of hot air rising is not entirely correct.  Hot air expands, cools back down as it gets higher, and sinks, continuing in a cycle to form convection currents.

Getting to your question, it is colder simply because there is less air in a certain amount of space at higher altitudes (lower pressure).  What you perceive as heat is the actually the vibration of these air molecules.  Thus, if there are less air molecules in a certain space, it translates to less vibration, and less heat!

Answer 2

Because pressure is lower, and wet bulb and dry bulb temperatures are different.

Answer 3

the higher you go the less mass of molecules to absorb and hold in the heat. air is more than just gases it is also water vapor which holds or retains the heat from sunlight and other sources. thats also why in deserts and other very dry areas you get a large swing in tempertures from midday to mignight. and in very moist areas like jungles or large bodies of water it tends to have smaller swings. all the answers previous had good points also which explained the lack of mass.

Answer 4

Air is heated by ____________, air is cooled by ________________.

Radiative

Convection

Conduction

Compression

Decompression

Mixing

Pressure

Density

Expansion

Answer 5

Excellent question!  As a previous answer said, it's not that hot air rises by itself.  Hot air expands (becomes less dense).  A neighboring body of cold air, being more dense, will move in and push the warm air skyward.  In the absence of cold air, the hot air will stay right where it is.

Now then, why is it colder at higher altitudes?  Well, it has a lot to do with how the air is heated.  Sunlight traveling through the low-altitude air does little to warm it.  Instead, it warms the ground and the ground warms the air above it; hence, most warm air masses form at low altitudes.  As cold air pushes the warm air upward, the warm air expands (gases expand as the pressure decreases...Boyle's Law).  When a gas expands, it cools in most cases, due to its thermal energy being spread out over a larger volume.  (Incidentally, the cooling air becomes less able to hold moisture, which is why rainclouds often form when cold air masses lift warm, moist air upward.)  Hence, you experience a lower temperature at higher altitudes.

In Earth's atmosphere, the air gets about 10ºC cooler for every 1 kilometer increase in atmosphere.  That's known as the adiabatic lapse rate.

I hope that helps.  Good luck!