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Frequency of Major Avalanche Winters

1980; Cambridge University Press; Volume: 26; Issue: 94 Linguagem: Inglês

10.1017/s0022143000010571

1727-5652

B. B. Fitzharris, Peter Schaerer,

Meteorological Phenomena and Simulations

Abstract A 70-Year record has been compiled for avalanches affecting the Canadian Pacific Railway at Rogers Pass, British Columbia. Time series are presented for avalanche frequency, avalanche mass, and length of avalanche debris on the rail line for 26 avalanche paths as well as for winter snow-fall. Winters with the heaviest avalanche activity were 1971-72, 1934-35, 1919-20, 1932-33, and 1953-54. Time-series analysis indicates that the size of avalanches has decreased in recent decades. Spectral analysis shows avalanche activity to the similar to white noise but with a weak periodicity of about 18 years. An examination of the climatology of big avalanche winters reveals two distinct circulation patterns: a strong zonal flow with frequent Pacific storms and heavy snow-fall; or a pronounced meridional flow, Arctic air outbreaks, and catastrophic avalanching released by rapid advection of warm moist Pacific air. Major avalanche winters need not be big snow-fall winters.