From Research Penn State, Probing Question
December 2010

Do you remember seeing your first snowflake? Maybe it was caught on your mitten, suspended atop the wool fibers so you could see every detail—graceful spires radiating from the center, so tiny and yet so intricately formed. Snow—whether a child’s snowman or a dirty snow bank along the roadside—is composed of millions of these miniscule masterpieces, each one different from the next.

Or so we’ve been told. How do we really know that no two snowflakes are alike? Ask a meteorologist, and you may find that the snowflake’s fabled uniqueness is a matter of semantics.

“It depends upon how we define snowflake,” says Hans Verlinde, associate professor of meteorology at Penn State.

Two of Verlinde’s colleagues, Dennis Lamb and Jerry Harrington, conduct research in Penn State’s cloud chamber to explore ice crystal growth processes. “The chamber allows them to grow crystals in conditions similar to cirrus cloud environments hitherto unexplored in a laboratory,” notes Verlinde. “Cirrus clouds are known to play a large role in earth's energy budget, and hence climate. The molecular level processes determine the shape of the ice crystals, which determine the characteristics of the clouds, which control the radiative properties of clouds and the role of cirrus in climate—it’s fascinating!”

Photo credit Julie Falk