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The man with a feeling for snow

The sun is shining. The snow crystals sparkle. A wonderful winter's day in Davos. Martin Schneebeli runs across the yard of the WSL Institute for snow and avalanche research (SLF) in the direction of the cold chambers in which he explored frequently, the physical properties of snow . Of course, the researcher is often asked about his name: How did it actually to be the subject of research in the name of down in the dumps? Schneebeli laughs. "It's a coincidence. The Name comes from the Region of Zurich, where I was born. But my parents say that I had felt early on, probably in the snow."

The researchers open a cold chamber. In it Mr 20 degrees Celsius minus. Quickly the cold is crawling in all the limbs. Then Schneebeli says something that it thinks in the first Moment, was interrogated: "snow is actually a hot Material." How please, here at minus 20 degrees? "Even in the coldest place of the earth, in the Antarctic, with a temperature of perhaps minus 90 degrees, is the study of snow with a high temperature physics."

Now Schneebeli is not the type of person who would lead a visitor with insane statements behind the light. What so he speaks? "In reference to our body temperature snow is cold. But in materials science, a Material is referred to as hot if its temperature is relatively close to the melting point. For example, when a metal melts at 1000 degrees, then the metal is, by Definition, above 600 degrees hot."

metamorphosis of the molecules

Transferred to the snow, this means: If the temperature is above minus 110 degrees Celsius, it is located in a high-temperature condition. "Here in the cold chamber at minus 20 degrees, snow is even super hot," says Schneebeli. Therefore, snow on the earth is also constantly changing. Often, the metamorphosis begins in the atmosphere, when the snow fall in flakes, but at the latest, if you have landed on the floor. The flakes grow together at the points of contact, sintering. There, where the snow blanket warmer is, evaporate – or in technical language: sublimate water molecules and attach themselves there, where the Snow cover is colder. "Within two or three days, the snow is transformed completely," says Schneebeli.

The investigation of the metamorphism of snow with a micro-computer tomography is one of Schneebelis special. The researchers built a small container that is filled with snow and the one at the top and bottom cooling can heating. Thus, a temperature of the snow sample gradient as in a blanket of Snow. "With the micro-computer tomography, we can examine the metamorphism of Snow, without destroying the structure of the snow," says Martin Schneebeli. With the data of snow cover, for example, models to verify and optimize.

Schneebeli takes a model of a snow layer consisting of a trunk, about 15 inches high and 10 inches wide Cube, reminiscent of a sponge. The top layer shows a much enlarged, the structure of fresh snow, a lot of small snow particles are closely interlinked. In the center of the model, the snow crystals to an almost solid mass fused. At the very bottom is a layer, which is characterized by vertical structures. "These pillar structures are formed, since the Transport of the water molecules in the snowpack primarily extends vertically," says Schneebeli.

When a skier loads the snow on such a layer of columns, these can break in a chain reaction and cause an avalanche. The pillars tilting under pressure, may compress the layer of snow also, re-integrate and stabilize. An avalanche forecast is supposed to know the art to which process dominates: a stabilizing compression or the destabilising build-up of columns.

Martin Schneebeli (60) has left Zurich early on. The Kindergarten he attended in Bern, the youth he spent, first in Winterthur and then in Kriens near Lucerne. "My father managed printers and repeatedly changed the Job." As Schneebeli and his brother were bigger, studied the mother at the University of Zurich botany. He himself has opted for the study of the culture of engineering. The thesis he wrote for the Regeneration of raised bogs. "90 percent of the bogs in Switzerland have been drained. This is a very valuable habitats to recover."

According to the doctoral thesis, he found a job at the SLF in Davos, where he first examined the importance of the forest as protection against avalanches: How close a mountain has to be the forest, so that no avalanches break loose? "In the framework of this project, I realized that the methods of the snow analysis were still rudimentary. So I have focused on snow physics."

As one of the first instruments Schneebeli has been developed at the SLF, together with American colleagues, the so-called snow micropen. This is a portable probe, the tip of which digs into the snow and 250 times per mm, the necessary strength records. Depending on the condition of the snow, the pressure resistance is different. So, with the snow only a few millimeters thick and with the naked eye hardly visible weak layers micropen identify. "The device is now become a Standard for snow cover assessment," says Schneebeli.

Arctic snow in 3-D

Currently, he and his Team deal with the remote sensing of snow with satellite. This measure from the snow-reflected electromagnetic radiation. The aim is to learn from it something about the structure of the snowpack, particularly in the polar regions. With the SnowMicroPen Schneebeli has, therefore, examines the structure of the snowpack, which is incorporated in turn in the with the satellite data fed blanket of snow models. "This is mainly due to the thawing Permafrost and the melting sea ice is a current and relevant topic."

Especially Schneebeli is curious, therefore, to the project the Mosaic (Multidisciplinary Drifting Observatory for the Study of Arctic Climate): In September 2019, the icebreaker will be frozen in the ice of the Arctic ocean to drift to a year with the sea ice in the direction of Spitsbergen. On Board, among other things, Schneebeli, and a micro-computer tomograph, with which the Arctic sea ice can be studied. "This is the first Time," says Schneebeli, "that we can examine the Arctic snow on the ground in three dimensions, and its physical properties accurately."

(editing Tamedia)

Created: 28.12.2018, 23:49 PM

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