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Hard race-courses and fast skis: The high-performance sport benefits from simulations of snow cover

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In ski races, it is often just hundredths of a second that separate the winners from the losers. Ensuring the piste is in the same condition for all the athletes is, therefore, an important prerequisite for a fair competition. This means the ski-runs for the races must meet high quality requirements. They should be as robust as possible so that the athletes are not too badly affected on their rapid descents.

The race organizers often use water in various ways on the pistes to make them extremely stable and prepare the courses. The water freezes in the snow pores, increasing its density and thus the strength of the race-course. Using too much water, however, unnecessarily raises the costs and the consumption of resources, and can even in some cases impair the quality of the pistes. How much water is then really necessary? And how long does it take for it to freeze completely?

Cold pistes need more water

This is why SLF was commissioned by the World Cup organizers to test how to optimize the irrigation at the Ski World Championships in St. Moritz in February 2017, at World Cup events and at SLF’s experimental sites. The SLF researchers used the snow-cover model “SNOWPACK”, developed at SLF, to simulate the water transport in snow-cover under different snow and weather con­ditions. They found out that, contrary to earlier assumptions, it is not mainly the hardness of the piste and the amount of pressure used that determines how much water the piste absorbed. Rather it is the temperature of the snow that is decisive. The density and the grain size also play a role: the colder and finer the snow, the more water must be used.

With the “SNOWPACK” computer simulations, the researchers were able to predict, with a precision of up to 5 cm, how far the water would penetrate into the snow cover under different weather and snow conditions, as well as how quickly it would freeze. The first to benefit from these findings was the Ski World Championships in St. Moritz. The model has now been adapted so that it can also help the piste-preparation specialists in other ski resorts to plan the best form of irrigation.


A small advantage for the Swiss team

SLF’s snow researchers will also be working on snow-cover simulations at the XXIIIth Winter Olympics in South Korea in February 2018. They have been commissioned by Swiss Olympic to estimate roughly 24 hours in advance what snow con­ditions can be expected and to exclusively inform the Swiss team about the snow consistency and the temperatures of the snow surface for the whole race-course. With this information, the service technicians will be able to choose and prepare the fastest skis possible under the snow conditions prevailing at the time of the competition.

In addition to the snow-cover model “SNOWPACK”, the researchers use the expanded model “Alpine 3D”, which can depict the local terrain in three dimensions and which was also developed at SLF. To ensure the forecasts are as precise as possible, they already accurately surveyed the runs in Pyeongchang last year. In their calculations, they also refer to models of the terrain, satellite images, weather forecasts and the weather stations installed locally. In Sotchi (2014) and in Vancouver (2010), the researchers were able to successfully use their simulations to support the Swiss team, giving the athletes a small, but perhaps in cases where it is really close, decisive advantage to keep the athletes one step ahead.

The two numerical models developed at SLF are “Open Source”, which means that everyone can access and use them. (Julia Wessels, Diagonal 2/17)