How ice melts snow

... or how the white splendor is created from water

In parts of Austria the first snow of winter has already fallen, and in some regions the first snowfall is just around the corner. But what exactly is snow? Just frozen water, is that true? Basically yes, but then “just water” is too simple. How so? You can find out in our current web story!

 

 

How is snow made?

Like hail, snow is a solid form of water. It occurs when the finest water droplets accumulate on crystallization nuclei (e.g. dust particles) in the clouds and freeze there. However, this process only starts at temperatures below -12 ° C. If the air temperature is too low, ice can form directly from the water vapor. Once the snow crystals in the clouds have reached a certain size and weight, they begin to fall. If it is too mild or too cold, it cannot snow. Cold air absorbs less moisture and at extremely low temperatures the air in the clouds becomes too dry to produce snow.

Variety of shapes of snow crystals

Every ice crystal has a unique shape, which means an unmanageable variety of crystal shapes: from branched stars to long, thin snow crystals to regularly shaped platelets, everything is included. Their pronounced symmetry is just as amazing as their variety of shapes. The basic hexagonal structure is common to all shapes. The reason for this can be found in the molecular structure of water.

At the beginning of the 20th century, the American researcher Wilson Bentley examined the small ice crystals scientifically under the microscope and described 5000 shapes, of which there are many more.

From powder snow and hailstone

If the air is very cold and low in water vapor, fine-grain powder snow is created. If it is warmer, large flakes will fall. Alternating freezing and thawing turns a snowflake into sleet or hailstone. Typical six-pointed snow stars are formed when temperatures in the clouds range from -12 to -22 degrees Celsius.

What if you compare the density of snow and water?

For example, if you let a liter of freshly fallen snow melt in a container, only a little water remains. When the snow melts, it loses its volume significantly, leaving around 200-250 ml of melt water. This means that snow - if you look at the volume - for the most part does not consist of frozen water, but actually consists of air.

The more air the snow contains, the lower its density. We therefore differentiate between different types of snow: there is powder snow that is very dry and can hardly be formed into snowballs, wet snow that is ideal for snowballs or wet snow that can even be used to squeeze water out with your hands.

Snow and its importance in the ecosystem

Snow is a poor conductor of heat and therefore plays an important role in the ecosystem. Many plants would freeze to death in deep cold if they weren't isolated from frost by a thick blanket of snow. Many plants can therefore survive a cold winter undamaged under the blanket of snow.

10.07.2020

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