When we think of snow, images of snowmen, skiing trips in the mountains and white rooftops come to mind, not to mention Christmas holidays spent with friends and family. It’s long been a key setting in tales of romance, adventure stories and bleak poetry for the literary-minded among us – but what do we actually know about snow?
What is Snow Made Of?
If you wake up in the morning and hear the weather forecast on the radio announce a temperature of anything below O°C (32°F), then you know there’s a good chance of snowfall ahead. In the United Kingdom, meteorologists state that weather conditions for snow need to be below 2°C.
When there is the right amount of moisture in the air, water vapour in the atmosphere freezes to form tiny ice crystals, leading to the formation of snowflakes. These snowflakes generally cluster around tiny particles in the air to become solid, and they begin falling to the ground when enough of them stick together and become too heavy to remain airborne.
Great! Is it Time to Build a Snowman?
Not so fast. Frosty needs to wait until the temperature becomes slightly warmer than 0°C, when heavier and larger flakes are formed as snowflakes start to melt around the edges. This is the ‘wet’ snow which can easily be moulded by our hands into different shapes and figures (otherwise known as ‘packing snow’).
Conversely, ‘dry’ snow is formed when flakes fall through air that is much colder and less moist, creating the powdery substance that is good for snow sports and is perfect for what is known as ‘powder skiing’.
Sleet and Slush
Sleet: This usually occurs during winter when temperatures are warmer than 2°C. Snowflakes fall through this warmer temperature, leading to precipitation that partially or wholly melts. As this melted snow falls, it eventually passes through another layer of cold air to solidify again. Sleet forms as it falls into minute, solid pieces of ice. Many refer to sleet as frozen rain, or a combination of rain and melted snow.
Slush: As opposed to sleet, which melts and partially solidifies as it falls through the air, slush is snow that partly melts as it reaches the ground. Known as a bit of a hazard to drivers on the roads, slush is not strong enough to bind like normal snow and gathers instead by mixing with dirt and other materials in puddles of water which are partly frozen. These ‘slush puddles’ are dreaded by city dwellers and skiers alike – accidentally stepping or falling into one is not anyone’s idea of fun.
Apart from being integral to our world’s climate, snow is essential to many living creatures around the world. It forms a habitat for many animals and plants, and supplies water to human beings and other organisms worldwide. The temperature of the Earth’s surface is regulated by snow cover, which in turn fills rivers and reservoirs across the globe when melted.