Item: Tides--their effects and nature, and a compu~er prediction program in forecasting
Title: Tides--their effects and nature, and a compu~er prediction program in forecasting
Proceedings: Proceedings of the 1980 International Snow Science Workshop, Vancouver, BC, Canada
Authors: Steve W. Hackett, ADK Mountain Consultants, Fairbanks, Alaska
Abstract: Over the centuries, numerous attempts have been made to relate many physical, as well as biological and psychological, phenomena to the positions of the moon and sun (Wylie, 1979). These attempts span a variety of approaches from folklore to Zodiac horoscopes, from Farmers' Almanacs to Solunar tables for feeding times of fish and game, from ocean height and current tables to accurately positioning satellites orbiting around the earth (Gamov, 1962). The relative changing positions of the moon and sun in the universe do in fact cause noticeable changes in the forces that act upon the earth. These forces are termed astronomical or tidal forces by scientists who study them. It is generally believed that the effects of astronomical forces (earth, ocean, and atmospheric tides) are relatively small as compared with other observable naturally-occurring forces on and within the earth's atmosphere and crust. Consequently, little has been previously expected in the way of direct tidal cause of geophysical phenomena (Table 1). Rather, tidal forces can be considered as "the proverbial straw" that, when added to other geological forces, may "break the camel's hack" or, when added to biological processes, may perhaps accentuate change. However, as extensive interdisciplinary scientific studies are conducted (U.S. Department of Commerce; 1978), more periodic phenomena unexplainable by other qeophysical processes seem related to the complex tidal phenomena (Table 2). Peter Lev (1981) proposes that astronomical forces can also be viable triggering mechanisms which, by their periodic action, can potentially release stored-up energy within the snowpack. All tidal forces are cyclic and would have the greatest effect during those times when the snow strength is changing toward a weakened state. Consequently, we would expect snow avalanche releases to tend to occur most frequently at those times and places where the tides act most effectively as triggers to release accumulating energy. However, we both believe, intuitively and nceptually, that it is important to recognize and emphasize that the proposed criterion for the effectiveness of tides as potential snow avalanche triggers is probably in the added stress produced by these tidal effects not the direct gravitational forces themselves.
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Keywords: forecasting, release, triggering, snowpack
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