Snow Fact #4 – Snow Albedo

Did you know that in the autumn time we get less sunlight every day, but suddenly snow makes it a lot lighter?

Before the first snow falls in the November it is usually quite dark here in the North. Feels like all the little amounts of light we get is sucked to the rainy roads and forests. It is dark, like really dark even during the days, and it is not the polar night yet.
This is a fact about snow and it’s ability to reflect light, and how it makes everything little bit brighter. The phenomenon is called “the albedo-effect”.

Albedo is an important concept in climatology. It is (now stay with me in this one) “the measure of diffusive reflection of solar radiation out of the total solar radiation received by a body”, and by body we mean the Earth’s body here. In plain English we are talking about the amount of light that reflects back to the sky when it hits the ground. And when the snow reflects sun’s light back to the atmosphere it is called the snow albedo.

Snow always increases the overall lightness, even if the snow albedo is actually highly variable. Clean white fresh snow reflects around 80-95% of the light that hits the Earth’s body, almost doubling the amount of light we observe. This means that after the first snow hits the ground days feel a lot less darker. If the snow is more wet than clear and clean it’s ability to reflect light will then decrease, wet snow reflects only about 50% of the light. With the dirties wet snow it’s still about 1.5 times brighter than without.

When you live in Lapland it is easy to notice the difference before and after the snow have arrived. Even at the darkest of times the little light we get feels a lot brighter and during all the clear days the winter scenery looks really beautiful. Thanks to albedo it is a lot of easier to get through the long lasting and dark winter time for Laplanders. And of course then there is more light to enjoy the winter for us all.

This was the 4th fact of our Snow Facts and the next frosty fact is coming out next Monday.




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