One of the best things about this time of year is that faint possibility that it might snow. The promise of snowmen and snowball fights, of time of work and school, of that cheer that only snow can bring, is almost enough to get us through the long, dark, bleak winter. They say no two snowflakes are alike, and although some pesky scientists have proved that incorrect, the intricate crystalline structure of snowflakes is truly beautiful. Snow is also hugely important for wildlife and people, and plays an important part in keeping our climate stable. To say Merry Christmas from Curious Meerkat this year, here’s a look at the science of snow – from its formation to its recreational uses and its role in the healthy functioning of Planet Earth.
Snow is simply a form of frozen rain, or precipitation, which occurs when cloud temperature is at or below freezing. Snow crystals tend to form in heavy, moisture-rich clouds, containing dust particles. Ice crystals form around these dust particles, called ice nuclei as the water vapour in the cloud slowly condenses. Snowflakes can be formed from multiple crystals that have melted slightly and fused together, or through new water vapour condensing onto existing crystals. As ice crystals grow inside the cloud, they get heavier and heavier until eventually their weight causes them to fall from the cloud. If the air temperature at the ground is low enough (below about 2°C), these crystals will remain frozen all the way and land on the ground as snow. Often, snow flakes that form in the clouds will have melted by the time they reach Earth, and all we see is the rain that results.