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LIAM McHUGH: It's the hard-packed launching pad for
snowboarders, the slick racing track of cross-country athletes,
and the speedy slope for downhill skiers.
TED LIGETY: Snow conditions are huge. You know, some races
you'll have really icy conditions, some races are soft.
McHUGH: Snow is an essential part of the 2014 Olympic Winter
Games. In fact, organizers in Sochi are worried whether or not
they'll have enough of it. The science of snow - how it's
formed and how it reacts - has been studied by scientists for
centuries and continues to this day.
SARAH KONRAD: Snow is the crystalized form, the solid form
of water, but that forms in the atmosphere so that it is able to
take on a unique crystal structure.
McHUGH: Sarah Konrad is a glaciologist at the University
of Wyoming. But unlike many of her colleagues, she's also a
former Winter Olympian.
KONRAD: I competed in the 2006 Olympics in Torino, Italy, and I
competed in biathlon and in cross country skiing.
McHUGH: Snow is a form of precipitation that begins as
tiny liquid water droplets in the clouds. In order to turn
into snowflakes, these water droplets need to be what
scientists refer to as "supercooled."
KONRAD: You're right on that point of going from liquid to
solid. We have a freezing temperature for water, but that
freezing temperature can change based on your altitude.
McHUGH: Supercooled water remains in liquid form,
even though it's below freezing temperature. For it to freeze,
it needs to come in contact with other particles, like dust.
These particles provide the impetus to start
the freezing process.
KONRAD: To make that transition, which takes energy to go from
water to ice, it needs something to start it. It needs a
nucleating particle, so a piece of dust, a piece of random
gasses, a lot of emissions from smokestack, different things
like that. When the water hits that particle, it can begin to
freeze and form a crystal structure.
McHUGH: Konrad demonstrates this process using a bottle of
supercooled water - pure, distilled liquid water that is
below freezing temperature.
KONRAD: It's pure, distilled water, so it doesn't have any
particles in it.
McHUGH: Disturb it - with a few good smacks -
and instant ice crystals.
KONRAD: See the ice slush up at the top?
McHUGH: The ice crystals that form in the
clouds become snowflakes.
KONRAD: As they accrete and freeze, they'll grow outwards
in that pattern.
McHUGH: Snowflakes come in many different shapes and sizes, but
can be grouped into two categories - plates and columns.
CORT ANASTASIO: That kind of stereotypical snowflake that
we're used to, those beautiful six-fold symmetric crystals,
those are called dendrites. And that's a type of plate.
McHUGH: Cort Anastasio is a chemistry professor at the
University of California, Davis and funded by the National
Science Foundation. He says that the size and shape of
snowflakes is determined by two important variables -
humidity and temperature.
ANASTASIO: Dendrites form under conditions where you have a lot
of water vapor. If you have less water vapor, you get much
simpler shapes, small plates, small columns.
McHUGH: Once the snowflakes land on the ground, physical changes
begin to occur almost immediately.
ANASTASIO: It gets blown around by wind, it can be broken up
into smaller pieces. The snow crystal shape changes.
KONRAD: The crystals start becoming rounder and smaller.
And once they're round, they're more like ball bearings. And at
that point, then you can ski across them much more quickly.
LEANNE SMITH: Sometimes there are those courses or those snow
conditions where you're just like [makes noise].
McHUGH: In Sochi, after two mild winters, organizers have made
contingency plans that include storing about 588,000 cubic
yards of snow under insulating blankets in nearby mountains.
But experts worry that stored snow can't quite compete with
freshly fallen powder.
ANASTASIO: It's going to melt and then when it gets
cold again, it's going to refreeze. And so it's going to
be really icy.
McHUGH: Though tiny, soft and delicate, when snowflakes
accumulate to form blankets of several feet, snow becomes the
ultimate playing surface upon which Olympic dreams are made.
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