APL Colloquium

December 6, 2002

Colloquium Topic: The Physics of Snow and Skiing: What is Snow Anyway?

The The main motivating factors in snow research have been snow hydrology and snow avalanches. The winter snow cover is the water reservoir in many parts of the world and measuring the quantity of snow on the ground is critical for spring and summer-time forecasting, but is a very challenging physical problem. The basic nature of snow as a material will be explained to show why snow science is not more advanced. In the US and each of the European-alpine countries there are about 30 deaths per year from snow avalanches and often a lot of property damage too. The problem with forecasting avalanches is that snow on the ground is a highly complicated, ever changing, layered medium. Furthermore, there is usually little data available about existing layers, how they are deforming, and how they are recrystalizing with time. The layered nature of snow and the interaction of the layers will be explained. While skiing is a common wintertime recreational activity, the physics of ski glide is misrepresented in many physics texts. The basic phenomenon comprising the tribology of ski glide is frictional heating. The energy balance at the sliding interface controls the friction so that even basal ski color is important. The production of electrical charges, the roles of hydrophobisity and surface roughness will be discussed.

Colloquium Speaker: Samuel C. Colbeck

Dr. Samuel Colbeck graduated from the University of Pittsburg in Petroleum Engineering with a B.S. in 1962 and an M.S. in 1964, followed by a Ph.D. in Geophysics from the University of Washington in 1970. He was employed at the US Army Cold Regions Research and Engineering Laboratory in Hanover, New Hampshire from 1970 to 2000 where he became Senior Research Scientist, 1991-2000 and Chief, Office of Science and Technology, 1998-1999. Concurrently, Dr. Colbeck was an Adjunct Professor of Engineering at Dartmouth College, 1981-2001. He is a Fellow of the American Geophysical Union, receiving the 1980 Horton Award; he served as President of the International Glaciological Society and edited the Journal of Glaciology and the Annals of Glaciology; he is an Honorary Member of the Electromagnetic Academy; and he is a Founding and an Honorary Member of the American Association of Avalanche Professionals. Dr. Colbeck is a consultant on ice safety systems for nuclear power plants and various other snow and ice problems ranging from skier accidents to large-scale hydrology.