Washington: The Winter Olympics conjure up images of snow-capped mountain ranges, frozen ice rinks and athletes in cold-weather clothing. And for good reason. Winter Olympic venues were often in places with an average snowfall of 300 inches per year or more.
However, barring some extremely unusual weather patterns, the mountains surrounding the Beijing Winter Olympics snow events will be brown and green and nearly clear of snow.
The region typically receives only a few inches of snowfall in each winter month. This means that basically all the snow that the athletes will compete on is man-made.
I am an atmospheric scientist specializing in mountain weather and snow. I am also the founder of a snowmaking startup and an avid skier. There are clear differences between natural and artificial snow, and it will be interesting to see if these differences have any effect on the competition.
While artificial snow and natural snow are both frozen water, most skiers and snowboarders can immediately recognize that the two are very different.
Traditional snow guns use high-pressure water, compressed air and specialized nozzles to blow tiny liquid droplets into the air that then freeze as they fall to the ground. But making snow isn’t as simple as making sure the air is cold enough.
Pure water will not freeze until it cools to nearly -40 F (-40 C). It is only the presence of microscopic suspended particles in water that can cause it to freeze at the well-known 32 F (0 C). These particles, known as ice cores, act like a scaffold to help form ice crystals.
Without these particles, water has trouble turning into ice. Different particles can increase or decrease freezing temperatures depending on their specific molecular configuration.
Two of the best ice cores are silver iodide and a protein produced by the bacterium Pseudomonas syringae. Most snow cannons add a commercial form of the bacterial protein to water to ensure most of the tiny droplets freeze before they hit the ground.
Glide on man-made snow
Natural snow begins as a small ice crystal on an ice core in a cloud. As the crystal falls through the air, it slowly grows into the classic hexagonal snowflake.
In comparison, man-made snow freezes quickly from a single drop of water. The resulting snow is made up of billions of tiny spherical ice balls. To the naked eye on a ski slope it may look like natural snow, but the natural and artificial snow feel very different.
Due to the fact that the small ice balls are packed quite closely together and some of them may not be frozen until they hit the ground, artificial snow often feels hard and icy. Fresh natural powder snow, on the other hand, gives skiers and snowboarders an almost weightless feeling as they descend the mountainside.
This is largely because the natural snow crystals stack very loosely on top of each other, a fresh layer of powder consists of as much as 95% or more air.
While fresh powder is what most recreational skiers dream of, Olympic skiers have different tastes. Racers want to be able to slide as fast as possible and use their sharp edges to make powerful, tight turns.
The dense, icy conditions of artificial snow are actually better in these respects. In fact, race organizers often add liquid water to natural snow tracks, which freezes and provides a durable, consistent surface for racers.
Another consideration is the fact that natural snow storms cause dull, flat lighting and poor visibility to race or jump into. Heavy natural snowfall will often cancel ski races, as happened during the snowy 1998 Nagano Games. For racers, clear skies and artificial snow offer the advantage there too.
But hard, man-made snow has its drawbacks. Freestyle skiers and snowboarders flying off jumps or sliding on rails high above the ground seem to prefer the softer surface of natural snow for safety reasons.
This includes cross-country skiers, who have recently highlighted the dangers of artificial snow in crashes, as icy, hard surfaces can lead to more injuries.
While Olympic athletes have mixed needs for their snow, natural snow is much better for the vast majority of recreational skiers. The air-filled crystals make it much softer and more pleasant to ski or snowboard on.
Scientists have been trying for decades to create more natural snow on demand. The first way people tried to make real snow was by seeding natural clouds with silver iodide.
The goal was to turn moisture in clouds into falling snow crystals. If you could make this process, called the Wegener-Bergeron-Findeisen process, happen more easily, it would theoretically increase the snowfall rate.
In practice, it has historically been difficult to prove the efficacy of sowing. However, recent work using large, precisely arranged sets of atmospheric instruments has shown that for a fraction of storms with the right conditions, cloud seeding with silver iodide does indeed produce a modest increase in total snowfall.
Another option that doesn’t require storm clouds to seed in the first place is to make snow cannons that can grow fluffy natural snow crystals. Scientists have been growing snowflakes in labs for decades, but the process is delicate and researchers usually only produce a few flakes at a time. Because ice crystals tend to grow slowly, it has been difficult for researchers to scale up the process by the many orders of magnitude needed to grow enough snow for skiing.
But in a quest to produce fluffy powder for skiers and snowboarders, my colleague Trey Alvey and I developed a process that can produce snowflakes in larger quantities using a technique that mimics the natural crystal formation process. We commercialize it through our company Quantum Snow.
The dry, barren mountains that will host the 2022 Winter Olympics aren’t exactly a ski destination. But thanks to the science of snowmaking, the athletes have reliable, albeit icy, runs to compete on. And sports fans can all be thankful for the technology that allows them to enjoy the high-speed spectacle staged by the brave souls who participate in the ski and snowboard events. (The conversation)
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