Snowflakes Swirl According to Surprisingly Simple Math

Snowflakes Swirl According to Surprisingly Simple Math

By Ellyn Lapointe

For all snowflakes’ infinite structural variation, their journeys to Earth are remarkably similar—even predictable. Researchers tracking more than half a million falling flakes have uncovered a broad mathematical pattern that describes precisely how they swirl through the air.

University of Utah atmospheric scientist Tim Garrett, senior author of a new study in Physics of Fluids, has studied snowflakes for nearly a decade. Although the behavior of such tiny, ephemeral objects may seem inconsequential, their fall speed is a key variable in forecasts of weather and climate, even in the tropics; most precipitation, regardless of where it eventually ends up, begins as snow.

Snowflake movement is typically studied in laboratories under controlled conditions that don’t reflect the complexity of nature. Scrutinizing falling snowflakes in the field has challenged atmospheric scientists for decades.

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For a new approach, Garrett teamed up with University of Utah engineers Dhiraj Kumar Singh and Eric Pardyjak to build a machine that measures the mass, density, area and shape of individual snowflakes that land on a hotplate. By placing this instrument underneath video cameras and a plane of laser light, the researchers could track how each snowflake moved in response to outdoor air turbulence.

“We were able to let the atmosphere express itself, to behave in a way that was completely uncontrolled by a scientist,” Garrett says. “I think that’s why we ended up uncovering an extraordinary simplicity, an…