Why does it get colder as we go higher?

Question

Why does it get colder as we go higher? Shouldn't it be the opposite as we are getting closer to the sun?

Answer 1

Pressure Volume Temperature and Altitude

If you put your hand on the ground and started to pile bricks up on it, it would soon become obvious why more bricks create more pressure on your hand. If your hand was higher up the pile, less bricks would be pushing down on you. Air is not weightless, (although of course a brick sized volume of air is much lighter than the brick itself). The pressure of air depends upon how much air is piled up in the column above it. (The column does not go on forever out into space because gravitational force is less further away. In fact you probably know that space is near enough a vacuum). So this explains why higher up the pile of air the pressure is less, (with mountaineers needing oxygen at high altitudes). The fall in pressure is roughly exponential, (assuming we ignore high and low pressure weather zones for the moment).

I know that you did not ask about pressure, but these things are connected, because,
(pressure xvolume)/temperature for a given mass of (dry) air is a constant.
Rising air will expand and lose energy and hence cool down. (This is just the opposite effect of when you feel air getting hot when you do the work of compressing it to pump up bicycle tyres).

The air is not very effective at transfering heat by conduction from warmer lower zones to cooler higher ones so it is (nearly) as if each zone is insulated from another. Physicists call temperature-insulated pressure-volume changes adiabatic.
As a result, at the heights we are usually interested in, the dry air temperature drops about 10 degrees centigrade for every 1 kilometre gain in height.
If the air is full of water vapour, (saturated), some of it condenses when air expands due to the lower pressure at higher altitude, and this releases the latent heat of evaporation, so that now air saturated with water vapour at a given altitude is not as cool as dry air so that it only drops about 5 degrees centigrade for every 1 kilometre gain in height.

Summarising, gravity modifies pressure, lower pressure at altitude causes expansion and adiabatic cooling of dry air, the rate of which is halved if the air is saturated with water vapour.

Footnote: The sun is about 150,000,000 kilometres away so that when rise say 10 km. we are still about 150 million kilometres away, so effectively no percentage change in terms of nearness to the sun. Also the way the sun heats air is not as straightforward as sun shining on a sheet of paper, say. The beams bounce off the Earth and certain (greenhouse) gases have molecular vibrational frequencies which help them to absorb energy from photons with infrared frequency on their way out. Distance from sun does not really come into it.

Answer 2

In simple words, the surface of the Earth acts like a heater. The layers of air that are closer to the surface of Earth get heated more as compared to the upper layers. The layers of air that are at a higher altitude are more distant from the surface and therefore are heated lesser just like an object further away from a heater in our rooms will be heated less.
But it is not as simple as that. Temperature lapse rate happens only upto a certain altitude. After that, this rule does'nt apply. There are many other factors.

Answer 3

. But in reality, the air is not warmed directly by the sun's rays, but
by infrared, or long-wave radiation from the earth. The sun's rays strike
the earth, and are absorbed by the earth, which raises the temperature of
the earth. The earth reradiates the energy at a wavelength dependent on the
temperature of the earth. The air is able to absorb the earth radiation, and
becomes warmer. At high altitudes, as on mountain tops, strong winds keep
the air mixed, and prevent much rise in temperatures near the surface of the
mountain.

As you go up in altitude from the surface of the earth, the air cools at a
fixed rate. This is called the "lapse rate," and for unsaturated air, that
rate is about 5 deg. C. for each thousand feet of altitude. For saturated
air, the rate is about 3.5 deg.C. for each thousand feet of altitude.

Answer 4

If the atmosphere is in motion, a packet of air that expands, cools. 3.5F per 1000 feet is the rate, not 3.5C/1000' as previously stated. This can be observed in the mountains. If it is 100F in Sacramento, then it will be about 86F in Yosemite Valley at 4,000'. And about 70F on top of Half Dome at 8,8000'.

Why? Most gases cool as they expand (that's how AC and fridges work). Consider the reverse - how a bicycle air pump gets hot at its outlet. The compressed air is hotter.

Note that if the atmosphere is not in motion and/or there is radiant cooling of the ground at night, an "inversion layer" can develop which traps pollutants close to the ground. That ugly brown layer that LA gets sometimes.

Answer 5

You may remember the formula from high school: PV=nRT.
For the air in our atmosphere, the V, n, and R can be considered constant, so the equation reduces to P ~= T.
As you go higher in the atmoshpere, the air pressure decreases (because there is less air above you pushing down) and so the temperature also decreases.

Answer 6

My science teacher asked us that question years ago...

Basically, he explained that the earth is like a hot water botter which emit heat. The sun warms the earth and the heat radiate from inside the earth. You should be warmer at the bottom of the mountain and cooler at the top! Hope this helps....

Answer 7

Adiabatic lapse rate is the rate of temperature change that occurs in an atmosphere as a function of elevation, assuming that air behaves adiabatically (thermally insulated). This term is most commonly used to refer to Earth's atmosphere.

The relationship between change in altitude and change in temperature is expressed as a lapse rate. In general, a lapse rate is the rate at which an atmospheric variable (usually temperature) decreases with altitude. It is expressed as the negative ratio of the temperature change and the altitude change, thus:

\gamma = -\frac{T_2 - T_1}{z_2 - z_1}

where γ = lapse rate is given in units of temperature divided by units of altitude, T = temperature, and z = altitude, and points 1 and 2 are measurements at two different altitudes.

Answer 8

The lower density of the air causes the temperature to drop. Think of a box of marbles, stick your hand in it and shake. The more marbels tat hit your hand, the hotter it is. Now take half of them out (lower presure) and repeat. Less marbels hit your hand and its not as hot.

Answer 9

Less molecules = less entropy = less heat.

Answer 10

cuz the human fart can't reach the upper atmosphere!