# sun melts snow
**URL:** https://boards.straightdope.com/t/sun-melts-snow/226795
**Category:** Factual Questions
**Created:** [January 30, 2004, 6:56pm UTC](https://boards.straightdope.com/t/sun-melts-snow/226795 "2004-01-30T18:56:55Z")
**Posts on this page:** 19
**Page:** 1
### Author:  [@vanilla](https://boards.straightdope.com/u/vanilla)
#### Post date: [January 30, 2004, 6:56pm UTC](https://boards.straightdope.com/t/sun-melts-snow/226795/1 "2004-01-30T18:56:55Z")
It has been below freezing here a long time.
When the sun makes an appearance, the snow(mainly in streest and sidewalks) melts.
WHy?
I thought it couldn’t melt unless it was above freezing.
Enlighten me, please.
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### Author:  [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)
#### Post date: [January 30, 2004, 7:01pm UTC](https://boards.straightdope.com/t/sun-melts-snow/226795/2 "2004-01-30T19:01:27Z")
The _air_ might be below freezing, but some of the sunlight is absorbed by the snow and converted to heat, and more penetrates through the snow to warm the ground underneath it.
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### Author:  [@Titan2](https://boards.straightdope.com/u/Titan2)
#### Post date: [January 30, 2004, 9:10pm UTC](https://boards.straightdope.com/t/sun-melts-snow/226795/3 "2004-01-30T21:10:38Z")
> [@Q.E.D.](#):
>
> The _air_ might be below freezing, but some of the sunlight is absorbed by the snow and converted to heat, and more penetrates through the snow to warm the ground underneath it.
Do you have a cite for that?Seems to me the ground \* underneath \* the snow would still be freezing or whatever is the ambient temp,but the reflected heat off all the snow and any bare surface areas,would melt some of the snow’s top suface and drain down/or into the pack.
One of the reasons weather stations have their thermometers about 2 feet off the ground and in the shade.They’re not affected by that phenomenon.(reflected heat)
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### Author:  [@Duckster](https://boards.straightdope.com/u/Duckster)
#### Post date: [January 30, 2004, 9:23pm UTC](https://boards.straightdope.com/t/sun-melts-snow/226795/4 "2004-01-30T21:23:49Z")
Sublimation.
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### Author:  [@vanilla](https://boards.straightdope.com/u/vanilla)
#### Post date: [January 30, 2004, 11:43pm UTC](https://boards.straightdope.com/t/sun-melts-snow/226795/5 "2004-01-30T23:43:11Z")
sublimation?
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### Author:  [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)
#### Post date: [January 30, 2004, 11:48pm UTC](https://boards.straightdope.com/t/sun-melts-snow/226795/6 "2004-01-30T23:48:51Z")
> [@vanilla](#):
>
> sublimation?
Sublimation is the process whereby a solid can do directly to the gas state without passing through the liquid state. This can be observed easily with dry ice and iodine. Water ice can also sublime. You can observe this in your own freezer. Put an ice cube in there and observe it over the course of a month or two. Eventually, you will notice it shrinking, until it finally disappears altogether.
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### Author:  [@AtomicBanana](https://boards.straightdope.com/u/AtomicBanana)
#### Post date: [January 30, 2004, 11:50pm UTC](https://boards.straightdope.com/t/sun-melts-snow/226795/7 "2004-01-30T23:50:29Z")
Sublimation is when a solid converts directly into a gas without going through a liquid state first, like dry ice does.
Since the snow _is_ melting, I don’t see how it can be sublimation. Or is there another definition I’m not aware of?
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### Author:  [@jive2keys](https://boards.straightdope.com/u/jive2keys)
#### Post date: [January 31, 2004, 12:02am UTC](https://boards.straightdope.com/t/sun-melts-snow/226795/8 "2004-01-31T00:02:16Z")
ya’ll are some kinda nerds or something
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### Author:  [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)
#### Post date: [January 31, 2004, 12:07am UTC](https://boards.straightdope.com/t/sun-melts-snow/226795/9 "2004-01-31T00:07:09Z")
> [@jive2keys](#):
>
> ya’ll are some kinda nerds or something
Yes. Yes, we are. And your point is…?
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### Author:  [@Qadgop\_the\_Mercotan](https://boards.straightdope.com/u/Qadgop_the_Mercotan)
#### Post date: [January 31, 2004, 12:09am UTC](https://boards.straightdope.com/t/sun-melts-snow/226795/10 "2004-01-31T00:09:40Z")
> [@jive2keys](#):
>
> ya’ll are some kinda nerds or something
Well, most posters here have had the benefit of an edjakashun, enjoy book larnin, can cipher purty gud, and even know their guzintas (an advanced cipherin tekneek).
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### Author:  [@AtomicBanana](https://boards.straightdope.com/u/AtomicBanana)
#### Post date: [January 31, 2004, 12:11am UTC](https://boards.straightdope.com/t/sun-melts-snow/226795/11 "2004-01-31T00:11:50Z")
> [@jive2keys](#):
>
> ya’ll are some kinda nerds or something
Dude, you like [The Darkness](http://boards.straightdope.com/sdmb/showthread.php?p=4502474#post4502474). You’re in no position to judge anybody. For anything. Ever. 😉
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### Author:  [@mmmiiikkkeee](https://boards.straightdope.com/u/mmmiiikkkeee)
#### Post date: [January 31, 2004, 12:26am UTC](https://boards.straightdope.com/t/sun-melts-snow/226795/12 "2004-01-31T00:26:09Z")
Another thing that can cause melting below freezing is the salt thrown onto the roads and sidewalks. Below a certain temperature (I think around -17C) it won’t melt ice. So if it’s been really cold like where I am, even salted roads will remain frozen. When it warms up to say -10C, the ice and snow will start melting a lot faster than it would without the seasonings. Especially if there are a few bare patches on the road, the sun can warm the road up a little more than ambient temperature. Once there’s a little water, it can run onto a colder spot and warm it up too.
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### Author:  [@levdrakon](https://boards.straightdope.com/u/levdrakon)
#### Post date: [January 31, 2004, 1:34am UTC](https://boards.straightdope.com/t/sun-melts-snow/226795/13 "2004-01-31T01:34:05Z")
There was an article about the effects of soot on snow & global warming [here](http://www.newscientist.com/news/news.jsp?id=ns99994508).
> [@](#):
>
> Fresh snow reflects more than 90 percent of incident light - both the organic and black-carbon components of soot increase its absorption. Local soot concentrations in snow vary widely, but Hansen estimates that it reduces light reflection by 1.5 percent in the Arctic and by 3 percent over land in the Northern hemisphere.
>
> The extra absorbed energy helps melt snow and ice. This creates positive feedback - and speeds melting - because wet snow absorbs more light than dry snow, and liquid water absorbs about 90 percent of the incident light.
Maybe the snow in your area is dirty?
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### Author:  [@ftg](https://boards.straightdope.com/u/ftg)
#### Post date: [January 31, 2004, 3:01am UTC](https://boards.straightdope.com/t/sun-melts-snow/226795/14 "2004-01-31T03:01:12Z")
“Positive feedback”? Isn’t that another term for…
“Snowball effect.”
I’d duck and run but I lived in a big time snow place for 7 winters. Somedays the weather service would report 2 inches of snow fall, but there was _less_ snow on the ground in the evening than in the morning. That was sublime.
Note that light penetrates quite deeply into snow and if it’s thin enough can reach the ground and then things heat up much quicker, but from underneath. Pavement is especially good at this heating effect.
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### Author:  [@scr4](https://boards.straightdope.com/u/scr4)
#### Post date: [January 31, 2004, 3:29am UTC](https://boards.straightdope.com/t/sun-melts-snow/226795/15 "2004-01-31T03:29:38Z")
Another effect to think about: if the road is not _completely_ covered by snow, the exposed patches of concrete absorb a lot of sunlight. The absorb heat is spread along the concrete surface by conduction.
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### Author:  [@robby](https://boards.straightdope.com/u/robby)
#### Post date: [February 1, 2004, 3:15am UTC](https://boards.straightdope.com/t/sun-melts-snow/226795/16 "2004-02-01T03:15:08Z")
Snow (or ice) sublimating at below-freezing temperatures is no more odd than liquid water evaporating at temperatures below the boiling point of water.
This is because the individual molecules making up the ice (or liquid water) do not all have the same kinetic energy at a given temperature. Instead, they are distributed as a [Maxwell-Boltzmann distribution](http://www.chem.uidaho.edu/~honors/boltz.html). At any given temperature, some of the molecules have enough kinetic energy to break the molecular bonds that bind it to its neighboring atoms, which allows it to escape as a gas molecule. So long as the partial pressure of water vapor in the air is less than the characteristic vapor pressure of water at that temperature, the process cannot reach equilibrium and will continue.
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### Author:  [@EasyPhil](https://boards.straightdope.com/u/EasyPhil)
#### Post date: [February 1, 2004, 4:53am UTC](https://boards.straightdope.com/t/sun-melts-snow/226795/17 "2004-02-01T04:53:31Z")
Does the energy from the sun have anything to do with causing the snow to melt?
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### Author:  [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)
#### Post date: [February 1, 2004, 4:55am UTC](https://boards.straightdope.com/t/sun-melts-snow/226795/18 "2004-02-01T04:55:52Z")
> [@EasyPhil](#):
>
> Does the energy from the sun have anything to do with causing the snow to melt?
Absolutely. If it weren’t for sunlight no snow would melt anywhere on Earth, except for areas with volcanic activity near the surface or at the sites of metorite impacts.
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### Author:  [@eburacum45](https://boards.straightdope.com/u/eburacum45)
#### Post date: [February 1, 2004, 8:37am UTC](https://boards.straightdope.com/t/sun-melts-snow/226795/19 "2004-02-01T08:37:18Z")
Additionally, the sun is marginally brighter in the northern hemisphere in winter compared to summer.
I shouldn’t have to explain why.