At first I thought maybe it would be like having a torch in a freezer but nope there would be a temp difference. So because it’s 5 f degrees outside with a -5 below 0 windchill how is it snow and ice are melting?
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Because….the sunrays are hot?
How do you get a sunburn on a cloudy day? The temperature can be below freezing but in localized areas there can be factors which allow the temperature to increase such as on blacktop roads or other areas where the surface temperature can be penetrated by the sins rays and increase temp while the air is only 32° or below.
This has to do with heat conduction.
Air is notoriously bad at conducting heat. That means for all the sun rays that hit the Earth, the air around us will likely heat up the least amount. The ground, on the other hand, is much better at absorbing and transferring the heat it receives from the sun. For that matter, the snow itself also absorb heat better than the air.
This is the same principle that makes the roads 100 degrees when it’s only 80 out.
For the same reason water in the ocean becomes vapor and then clouds without the oceans boiling away. The sun is warm enough to make small amounts of water on the very surface become lighter than air and rise.
Same thing with ice. The sun is warm enough to heat up tiny layers of snow and ice on the very surface even if the sun is not heating up the whole entire atmosphere in the region where you live.
Instead of thinking of things as colder or warmer, think of it as heat transfer. If you add head to 32 F snow, it’ll melt, if you remove heat from 32 F water, it’ll freeze. And there are three ways of either adding or removing heat, conduction (heat via contact), convection (heat via moving contact), and radiation (heat via non contact, i.e. magic).
Now, let’s say you wanted to make one of those freezing plates in an ice cream parlor (where they put the cream on a plate and scrape it as it freezes). Now, if the room is 70 F, how can you get something to freeze? You ensure that you are removing more heat from the plate, then you are gaining from the air.
The reasaon the snow is melting is because it is gaining more heat from the sun, then it is losing to what is around it.
Because air is transparent and doesn’t absorb sunlight, but snow is opaque, and while it’s mostly white, it can still absorb sunlight and start melting, but air really doesn’t heat up when sunlight shines through, it heats up from the ground, which takes time to warm up
Note that wind chill is only relevant to humans and similar warm-blooded animals; it doesn’t apply to ice and snow. If the air temperature is above freezing then water won’t freeze no matter how low the wind chill temperature.
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