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An air mass climatology of Canada during the early nineteenth century : an analysis of the weather records of certain Hudson's Bay Company forts Minns, Robert


The post journals of certain Hudson's Bay Company forts were examined for evidence that air mass frequencies during the first half of the nineteenth century were markedly different from those of a modern (1955-1959) period. The "partial collective" technique of Bryson was used to determine the modern frequencies and to provide the basis of the conditional probability structure employed to estimate the historic air mass frequencies. There is evidence from each station for which analysis was performed of a greatly increased presence of "Arctic" air, probably as a consequence of a weakened zonal atmospheric circulation and a decrease in the eastward penetration of "Pacific" air.

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