In general on earth, the higher the altitude the colder it gets. I’m sure this has to do with the thinning of the atmosphere, or other related issues. But shouldn’t closer proxmity to the sun, even slight, cause some rise in temperature? I guess the atmospheric issues cancel the closeness to the sun out, but in places where that was not an issue (like the moon, I guess), would higher altitudes mean higher temperatures?
Probably…except that the percentage difference in distance to the sun between sea level and the top of Mt. Everst (or any two points on the surface of the moon) is so small that you probably couldn’t measure the temperature difference. Divide 29,000 feet into 93 million miles and see whatcha get. 
Of course it would. In an ideal, vacuum situation, the amount of energy impinging on you from the sun depends on your (a) cross-sectional area exposed to the sunlight, and (b) the percent of the sun’s spherical cross-sectional area you block (not sure for the correct term for this). If you move closer to the sun, (b) gets bigger. Of course, since the distance from the lowest point on earth to the highest point on earth is EXTREMELY small compared to the distance from the sun, the effect is absolutely miniscule. You’ll notice a MUCH bigger change just sticking your hand out (and thus increasing (a), your cross sectional area exposed to the sun).
Arjuna34
When you go up, it gets colder because you’re getting farther and farther from the Earth.
Let’s put things into perspective here: The average distance from the Earth to the Sun is approximately 93,000,000 miles. A tall mountain might reach 3 miles. We’re talking about a difference of one part in 31 million on the distance here. Then, you’ve got to consider that radiant energy from the Sun is proportional to the inverse square of the distance, so we have a difference in radiant energy of about one part in a quadrillion (or one part in a billiard, if you’re British). Even without an atmosphere, there’s bound to be other effects which would greatly overshadow that effect: Slight differences in the color of the rocks, for instance.
I have always heard it explained that the heating of the atmosphere is mostly accomplished by energy reflected or emitted from the Earth, and that direct heating of the air by the sun is relatively very small. So the farther you get from the Earth’s surface, the colder the atmosphere gets.
Is this accurate?
I believe that the temperature of the earth’s “standard” atmostpheric profile in the temperate latitudes drops linearly with altitude up to about 35,000 feet (~3.5 deg F/1000 feet).
From there up to 65,000 feet or so, the temperature is more or less constant (-35 or 40 deg F, I think), and above that it begins to rise again with altitude.
I’ve forgotten the vast majority of what we covered in my atmospheric dynamics class, and the textbook is not here in my lab, so I’m really fuzzy on the details. I believe that, like wevets said, most heating of the atmosphere in the troposphere (below 35,000 feet) is caused by radiation from the planet rather than from the sun.
I’d have to check the book or some other source to give any better info than that.
Actually, it doesn’t just get colder as you go up. Air (with a couple of exceptions; see below) doesn’t absorb the sun’s radiation much at all and thus stays cold. The air at ground level is warm because the ground absorbs solar radiation and heats up the air by conduction. As you go up in altitude, the air gets colder because it is further from the ground. Until you hit the ozone layer–O[sub]3[/sub] absorbs UV radiation and heats up, so the air in the vicinity gets pretty hot. Above that, it gets colder again until you hit the ionosphere, where it gets hot again, and then above that it just gets colder and colder.
That’s what I remember from my intro chem class 2 years ago, anyway.
You’d better crunch those numbers again Chronos. You squared the wrong one. You need to square (1 - 1/31 million) so the difference in radiant energy is about one part in 15 million. That’s still small enough to shoot apart curwin’s conjecture, but it’s good to get these things right. Especially if you’re an anal, former math major like me.
An aside:
Do the British really say billiard? That’s appropriate for me because in the one time I played English billiards, it took me about a quadrillion shots to make a point. (Give or take a couple billion.)
That doesn’t explain why Mt. Everest is so cold. I mean, Mt. Everest is exactly the same distance from the surface of the Earth as is Death Vally.
Yes, Greg Charles, you’re correct… I screwed up the math there (I was only a math minor). It’s still a very small number.
And in Britain, the numbers go up thousand, million, milliard, billion, billiard, trillion, trilliard, etc. In a way, it makes sense: A billion is a million to the two, a trillion is a million to the three, etc.
Chronos: The British don’t use the old million, milliard, billion, billiard system much any more. I can rememember my teachers talking about ‘British million’ and ‘American million’ when I was about 8 years old. I’m 25 now, and I don’t think I’ve ever heard anyone even need to confirm which kind of million or billion they’re referring to. We use ‘million’ to mean 10 to the sixth power, in order to be in step with the global scientific community.
On Mars, there can be a huge difference between temperatures right at ground level vs. just a few feet up into the atmosphere (something like 20 or 30 degrees F difference, IIRC from the Pathfinder mission).
Even though the moon has no atmosphere (beside peaceful ), its ground still retains heat and keeps it warmer than empty space.
But Mt. Everest is surrounded by a heck of a lot more cold high-altitude atmosphere than Death Valley is.
Not to mention that I’ll bet the winds keep air moving over Everest at a pretty good clip. I doubt the air stick around to get heated up by heat from the surface of Mt. Everest itself, which, if I’m not mistaken, is mostly covered with ice and snow anyway.
heat transfer = convection + conduction + radiation
the atmosphere is sitting between a warm Earth and freezing space
the atmosphere acts like an insulator between the Earth and space (retaining heat…a little greenhouse effect has been good to us)
high altitude winds, like atop Mt Everest pull heat away (convection). You would be hard pressed to find a cool breeze in Death Valley.
We seem to agree that the difference in solar radiation is negligible (distance-wise) from the upper atmosphere to ground level. So that leaves us with convection (e.g., winds) and conduction (e.g., warmed earth) forces to affect our local temperature.
Well, that, plus weather systems.
I could be wrong here, but I seem to remember reading that the radiation from the earth’s surface was a major (dominant?) means by which the lower atmosphere gains heat.
Most of the solar energy is at wavelengths that the atmosphere largely transmits, so it penetrates to the ground and is absorbed there. The earth’s temperature is considerably lower than that of the sun (obviously), so its blackbody/graybody/whatever radiation peaks at a much lower wavelength, and this radiation is absorbed by the lower atmosphere.
Sure, there’s some conduction of heat between the ground and the air right there at ground level, but I do believe that radiation from the earth is quite significant, too.
Does this sound right to anyone? I can’t seem to find any handy references to check…
I could be wrong here, but I seem to remember reading that the radiation from the earth’s surface was a major (dominant?) means by which the lower atmosphere gains heat.
Most of the solar energy is at wavelengths that the atmosphere largely transmits, so it penetrates to the ground and is absorbed there. The earth’s temperature is considerably lower than that of the sun (obviously), so its blackbody/graybody/whatever radiation peaks at a much lower wavelength, and this radiation is absorbed by the lower atmosphere.
Sure, there’s some conduction of heat between the ground and the air right there at ground level, but I do believe that radiation from the earth is quite significant, too.
Does this sound right to anyone? I can’t seem to find any handy references to check…
Arrgh! Sorry for the double post.
Just something to note, though I don’t have any hard evidence to back me up as yet.
It is obviously true that in terms of distance, the energy from the sun will be negligibly different at altitudes (indeed, the distance at sunrise and high noon is far greater but just as unimportant (though there is the angular difference there as well)). However, I think the energy you’ll receive (maybe only in the UV range) will in fact be significantly greater due to less atmosphere above you. I don’t know what the actual effect will be, though.
From experience and traditional knowledge, I know there is a very high danger of skin burns at high altitude. Mostly, though, this is a combination of high winds and (even more so) the abundance of highly reflective snow, rocks, etc. Of course, it’s generally cold enough that most people are well-wrapped up. But I have been on a tree-lined ridge and meadow at 10000’ in shorts and T-shirt, about 75 deg weather and it really did feel like my skin was burning much faster. I could feel a big difference when I put more sunscreen on.
So was I only imagining this, or is 10000’ of air over me a significant enough volume to make a difference?
Absolutely, you get more UV radiation at altitude. Not only is there less atmosphere to absorb the UV, it’s significantly less dense than down low. When you climb high, you are getting clear of all the soupy atmosphere and into the thin stuff. There is less above you, and it’s thinner than the stuff below.
You must be very careful about sunscreen at altitude, you burn much quicker. In addition, you have to be more careful about sunglasses, but that is probably more due to the reflections off of snow and rock than due to atmosphere. Glacier glasses help preserve eyesight.