Can the sun melt snow when it is below zero outside?

Answer 1

The snow does not melt, it sublimates. This means it changes from a solid, ice, to a gas, water vapour, without going through a liquid stage. It isthe same thing that happens in your freezer when ice cubes get smaller in their trays. The ice is sublimating to water vapour.

The opposite process is deposition where water vapour freezes directly to ice without condensing to water first. The most commonly seen occurrence of this is frost.

Answer 2

As long as the snow remains clean and white all the sun's radiation will be reflected and not melt. But what will cause the melting will be the sun's radiation being absorbed by surrounding darker areas. As the darker border around the snow warms the snow in contact with this border will melt and progressively shrink as the border continues to heat. Remember that white reflects visible sun light while those things that are dark absorb sun light and re-radiate the heat as infrared radiation.

Answer 3

Yes. If the air temperature is close to freezing, the snow may still melt if it is contact with a warm surface (asphalt for example). And if it's early spring, the sun may be strong enough to directly thaw the top layer of snow through radiation.

But if it's several degrees below freezing, it won't melt.

Answer 4

The sun's light carries energy. When the snow absorbs a certain amount of energy it changes phase. The air temperature is only relevant in the amount of energy absorbed from the snow. You'll also find that in the late afternoons the air above snow is warmed and rising.

Answer 5

Yes if you use a magnifying glass, like killing ants in the summer.