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We got over 3 feet of snow this week. Today is very sunny and it looks like it's melting.
How can this be if it is much lower than 32 F outside? I understand it may be "the streghth of the sun." But if this was true, how does this not make the base temperature rise from the teens?
Solid objects such as snow heat up more than a gas like air in sunlight; combined with ultraviolet light that comes in, snow can indeed melt when it's 15F. This is observed all the time in lower-latitude parts of the U.
S.
The sun heating up the ice to above freezing point even though the air is still below freezing.
Here in England we hardly ever get sun in winter so our snow still hangs around for ages even when it goes above freezing.
Not down here - we had a blizzard between 6 and 8 in thismorn, snow was gone by 11am! Mind you it was sunny and above freezing by 10 - but that's typical south coast of England for you - it never snows, and if it does, in never stays!.. There's a saying, "If it snows in Pompey, then you know it's extreme elsewhere in the UK!"
A lot of snow disappears due to sublimation. Dry arctic weather at 15F causes some molecules of snow to drift into the atmosphere, they don't even have to melt, they just go from solid to gaseous state.
A lot of snow disappears due to sublimation. Dry arctic weather at 15F causes some molecules of snow to drift into the atmosphere, they don't even have to melt, they just go from solid to gaseous state.
Indeed. Back in 1947 when it was below -80F in the Yukon, they were losing 1/2 an inch per day due to sublimation.
But why is the sun heating the ice specifically and not the air? Or why is it heating it more than the air?
Air is transparent to sunlight (most of it, anyway). This means that we can see things (which is good) but it also means that air absorbs almost no energy from the sun. The air itself is heated through contact with the surface (land, water, snow, etc.) and this is a somewhat slow, stochastic process. The air can and is colder and hotter than the surface.
Surfaces absorb varying amounts of the sun's energy themselves. If you notice blacktop melting snow and white concrete staying snow-covered, that's because black surfaces absorb everything and white surfaces mostly scatter the light away (although they absorb more than air, generally). Sublimation also plays a part in snow removal but the melting you describe is more indicative of solar heating.
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