Breaking through the "bottleneck" technology and achieving "free use of snow" in the Winter Olympics

The snow used in the Winter Olympics does not rely on nature, but on artificial snowmaking technology. How is artificial snow "mass-produced"? What is the "ice-like snow" technology that my country has overcome?

Interview experts

Su Zhengjun (Senior Engineer, Weather Modification Center, China Meteorological Administration)

When people think of the Winter Olympics, they always think of the snow-covered scenes. Snow is not only a beautiful background and foil for winter outdoor sports, but also the most basic component of every track.

So, does the Winter Olympics depend on good weather to obtain qualified snow for the competition? Especially for Beijing, which will host the 2022 Winter Olympics, although it is still chilly in February, will the Winter Paralympics held later face snow shortages due to the warming temperature?

Such concerns are obviously unnecessary. The development of snowmaking technology is enough to make this Winter Olympics a high-quality "free use of snow".

This snow is not that snow: Artificial snow is safer and more controllable

Reporters learned that in order to ensure the smooth progress of snow events during the event, this Beijing Winter Olympics adopted a high-efficiency, high-quality, fully automatic and controllable artificial snowmaking solution, and took "snowmaking, snow conservation and snow storage" as the three major aspects to ensure that the use of snow during the event is not affected.

△On November 15, the Zhangjiakou National Cross-Country Skiing Center took advantage of the natural snowfall and turned on the snowmaking machine to make snow (Source: Xinhua News Agency)

Taking into account the uncertainty of natural weather processes, especially snowfall, international snow sports events, especially the Winter Olympics, generally use artificial snow to pave the snow tracks. The reason is that, on the one hand, artificial snowmaking technology is controllable and does not need to rely on the weather; on the other hand, the threshold of this technology is relatively low - as long as the temperature is below 0℃, the snow machine can work.

"Usually, artificial snowmaking uses 'snow cannon' type snowmaking machines. There are two principles for this type of machine. One is to use an ice-making device to produce very small 'ice flakes', which are then used as raw materials to make snow. The other is the traditional method of mixing high-pressure water and air to make snow." Su Zhengjun, senior engineer at the China Meteorological Administration's Weather Modification Center, told reporters.

Traditional artificial snow is made by injecting water into a special nozzle or spray gun, which uses high-pressure air to divide the water flow into tiny particles. When these water droplets encounter the cold outside air, they will quickly solidify into ice crystals before hitting the ground, becoming the snowflakes we are familiar with.

"Artificial snow takes a short time to form, grows quickly, and the shapes of the snowflakes are basically the same. Natural snowfall will have a more obvious change in hardness on the second day," explained Su Zhengjun.

In the early morning, when the outdoor temperature is low, the natural snow is usually more solidified and hard, similar to "ice chips". Although this state of snow allows skiers to reach a faster sliding speed, it also makes the snowboard's grip less effective. Especially for novices, if the soft natural snow is not compacted, the snowboard is very easy to sink into the snow, causing accidents such as rollover and sudden stop.

△The smooth machine-groomed snow track is also called "noodle snow" by enthusiasts, and skiing on the machine-groomed snow track is likened to "eating noodles." The picture shows the machine-groomed snow track in Changbai Mountain International Resort, Jilin (Source: Xinhua News Agency)

In comparison, the quality of artificial snow is more controllable, especially high-quality "ice-like snow", which will gradually change from granular to powdery after the sun comes out. At this time, the snow quality is the best, soft and moderate, and is most suitable for various outdoor competitions using snowboards.

Creating a "rubber track" on snow

It is easy to understand that artificial snow can help us get rid of our dependence on natural snowfall. So why do some winter sports tracks still use artificial snow in areas where there is snow all year round and the snowfall is extremely abundant?

This brings us to another advantage of artificial snowmaking: it is customizable. According to the needs of different events and venues, artificial snow can freely adjust the particle size, water content and hardness of the snowflakes.

For example, alpine skiing, a traditional event of the Winter Olympics, has always been hailed as the "crown jewel of the Winter Olympics" because of its high viewing value. However, the participants in this event move at very high speeds (up to 248 kilometers per hour) and are very dangerous, so the requirements for the track are more stringent. In order to build a snow track that meets the international standards for alpine skiing, the snow used is not ordinary natural snow, but artificial "ice-like snow".

The so-called ice-like snow is used to describe the state of snow quality on the ski resort. In this state, the density of snowflakes is about 0.65 grams per cubic centimeter, and the surface of the ski slope remains crystalline, as if there is a thin layer of "ice shell", similar to the ice surface. Such a ski slope is hard and not easy to be damaged. When athletes turn at high speed, the surface of the ski slope can be guaranteed not to deform. No matter which athlete comes out, the state of the ski slope is relatively perfect.

△Competition-level snow trails are denser and more solid, so you can slide faster, but it also hurts more when you fall (Source: WeChat official account of "Chai Zhidao")

If ice-like snow is used to pave the track for alpine skiing, it is like building a "plastic track" on the snow. It can not only reduce the friction of the track surface on the skis and significantly improve the athletes' performance, but also improve the athletes' comfort when skiing, protect their body joints, and extend the athletes' professional sports careers as much as possible.

Snow conservation and storage technologies ensure track quality

For a long time, creating high-quality ice-like snow tracks has been a "bottleneck" technical difficulty in my country's ice and snow industry. In order to welcome the Beijing Winter Olympics and Paralympics, scientific researchers have established the territorial parameters for making ice-like snow in the Beijing Yanqing and Zhangjiakou competition areas through unremitting efforts. At the same time, with the help of a set of snow-making processes such as water injection and compaction, they have successfully made qualified ice-like snow that meets the climatic conditions of the continental monsoon area. The natural snowfall in the local mountainous areas in winter has become the "landscape snow" that decorates the Winter Olympics competition area.

In fact, for the high-standard Winter Olympic track, natural snowfall is a "burden". If it snows, the soft natural snow will make the "smooth as a mirror" ice-like snow track fall short. In addition, since the Beijing Winter Olympics and Paralympics are in the transition period between winter and spring, they may encounter other extreme weather, such as sudden rainfall, which will cause thin ice to form on the surface of the track, increasing the risks faced by athletes during the competition.

△On February 23 this year, staff at the National Alpine Skiing Center ("Xue Feiyan") in Yanqing were inspecting and repairing the track (Source: Xinhua News Agency)

According to the planning of scientific researchers, if the weather is really bad, the staff will immediately use the snow groomer to re-compact the snow track and perform emergency finishing on the track. At the same time, in order to ensure the quality of the track, they will also use automatic measuring instruments such as ice and snow hardness testers and ice and snow particle size testers for quick testing, so as to ensure that the snow quality is qualified and resume the normal progress of the competition in the shortest time.

It is reported that in order to ensure sufficient snow during the event, this Beijing Winter Olympics also made bold attempts in snow storage: taking advantage of the lower temperatures in winter, qualified snow was made in advance, and then the snow was stored in a flat area until it was used the following year.

This seemingly fantastic plan had already passed the feasibility test as early as 2017. The Beijing Winter Olympics Organizing Committee successfully carried out a snow storage test at the Yanqing Shijinglong Ski Resort. After the test in the spring and summer of the following year, more than 60% of the artificial snow was successfully stored.

Further reading: How many steps are involved in creating an ice-like snow track?

Snowmaking machines are not the only reason to build an international, high-level ice-like snow track that can be used in Olympic events. At present, ice-like snow tracks can be divided into two categories: racing tracks and competitive tracks. Take the ice-like snow racing track as an example:

The snow groomer first needs to turn over the snow track, break up the snow and make the snow surface loose;

According to the location of the track and the temperature at the time, water is injected into the snow - only in this way can the track be guaranteed to have both a certain strength and sufficient elasticity;

By continuously turning and pressing the wet snow, the prototype of an ice-like snow track is basically formed;

△Different from the watering method of the racing track, the competitive track adopts the "Z-shaped water injector" watering method (Source: Beijing Daily)

After that, the staff must ensure that the thickness of the icy snow layer is uniform and there are no large holes on the snow track. After confirming that everything is correct, they will flatten the track so that the snow layer forms a shiny "ice shell" from bottom to top;

After completing all the steps, the staff also need to clear the floating snow on the track.

At this point, a qualified "mirror-like" ice and snow track can be put into use.

Written by reporter Wang Xueying

Editor/Ding Lin New Media Editor/Lv Bingxin

Produced by: Science Central Kitchen

Produced by: Beijing Science and Technology News | Science Plus Client

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