By Vidyaratnam Ganapathy
A hexagonal snowflake - Don Komarechka - The Toronto Star
Snowflakes are some of the most beautiful sights in nature. Each flake different, an individual unto itself, with beautiful, intricate designs that could not even be crafted by a team of celebrated artists. Despite the commonly held belief that these designs are formed by chance, they are actually formed through a highly scientific method.
Snowflakes are formed when millions of tiny water molecules condense onto a “nucleus” (which can be a dust particle in subfreezing temperatures, or an aerosol in contact with a liquid cloud droplet in warmer temperatures) and freeze to form snowflakes. The formation of snowflakes happens in conditions with high moisture levels, similar to the formation of clouds, and occur at temperatures below –35 °C. Each snowflake derives its characteristic design through the difference in position and shape of the ice crystals that make up its structure.
The distinctive hexagonal patterns of snowflakes are formed due to the natural arrangement of the ice crystals around the snowflake nucleus. When water freezes into individual ice crystals, its molecules form a hexagonal lattice shape. These ice crystals are arranged in a pattern which then forms the base of the snowflake. As the snowflake falls towards the Earth, it encounters humid air, which causes more water droplets to come into contact with the snowflake and freeze. As the ice crystal grows, water can freeze onto its six corners multiple times. The snowflakes go through different humidity and temperature variations, which results in each snowflake being of a unique design. Snowflakes can take on an infinite number of shapes and designs, each representing a different combination of humidity and temperature variations that the snowflake experienced.
Snowflakes can also vary by the temperature they are formed in. From 0 C to -4 C, the snowflake takes the shape of thin hexagonal plates and stars. Between -4 C and -6 C, they are needle-like. Between -6 C and -10 C they are formed as hollow column snowflakes. They are found as sector plated snowflakes between -10 C and -12 C. They form dendrite shaped ends between -12 C and – 16 C. Between -23 C and -35 C, they form snowflakes with plated and columned ends.
Some types of snowflakes
Snowflakes generally form in the upper atmosphere, but may not always reach the ground as snowflakes. They only remain snowflakes when the temperature is below freezing at all levels until the ground. When snowflakes encounter warmer layers before they reach the ground, they melt to form water and then refreeze depending on the size of the layer of the air. Snowflakes can be transformed into two different weather patterns, sleet and freezing rain.
Sleet is the phenomenon by virtue of which snowflakes melt and refreeze to form pellets of ice. This occurs when a shallow warm layer of air is present in between two large cold layers of air. The snowflakes are formed in the first large cold layer, and melt in the shallow warm layer, which results in the loss of the snowflake shape and the incidence of partially melted snow. In the next cold layer, the snow freezes to form the sleet, which has the shape of ice pellets.
Conditions for Sleet Formation
Freezing rain is the phenomenon by virtue of which snowflakes melt and get supercooled when in contact with a shallow cold layer before reaching the Earth. This occurs when a large warm layer of air is present in between a large and a shallow cold layer of air. The snowflakes are formed in the first large cold layer, and melt completely in the large warm layer to form drops of rain. In the next cold layer, the water drops undergo supercooling, which involves the cooling of a liquid below its freezing point without crystallization or solidification. This results in freezing rain.
Conditions For the Formation of Freezing Rain
Despite the fact that snowflakes appear to be white when they fall to the ground or seen in a group, they are actually clear when viewed individually under a microscope. The snowflakes appear to be white because of the scattering of light when it impacts on the crystal surface of the snowflake. The crystal surface reflects light into all its spectral colors equally. These colors all combine to form white light, which is why we perceive snowflakes to be white.
Snowflakes can form inside clouds due to the freezing of water droplets at sub zero temperatures. Rime consists of tiny frozen water droplets, which are formed in clouds at extremely low temperatures. These snowflakes sometimes collide with rime that is supercooled inside the cloud, which create a phenomenon called rime snowflakes. These rime snowflakes can fall to the ground in the form of rime snow. Snowflakes can have no rime, a little rime, which indicates the presence of a few supercooled droplets, or can be highly rimed. A large number of rimed snowflakes form a type of snowfall called graupel, which is a denser and more granular form of snow.
Snowflakes also have the ability to dampen noise and other vibratory acoustics when they are freshly fallen. This occurs because the vibrations caused by the noise get trapped in the between individual snowflakes and in the gaps in the structure of the snowflake. This reduces the overall vibration created by the sound, which results in less sound being generated. Snow cover of only 25 mm can considerably dampen the acoustics of the area over a landscape. Snow loses this ability when it ages, because it hardens and compacts. This limits its ability to absorb sound vibrations.
Snowflakes are one of Earth’s most enigmatic creations, artistic and beautiful at first sight, and they also contain a scientific background that piques the interest of all those who study it.
References:
McKnight, Zoe. Barrie Photographer captures snowflakes’ unique beauty. Barrie photographer captures snowflakes' unique beauty | The Star. Retrieved: 16 April 2021.
King, Hobart M. How do snowflakes form? How Do Snowflakes Form? -- Why is Every Snowflake Different? (geology.com). Retrieved: 17 April 2021.
Means, Tiffany. The Science of Snowflakes Explained. Snowflake Formation, Shape, and Design Explained (thoughtco.com). Retrieved: 17 April 2021
Migiro, Geoffrey. What is Graupel? What Is Graupel? - WorldAtlas Retrieved: 17 April 2021