Multivariate classification of Calgary weather systems: Exploring trends, variability and synoptic relationships, 1953--2004

Multivariate synoptic exploration of weather system frequency identified changes in Calgary climate and relationships to precipitation and snowfall not previously observed. Fourteen weather systems were objectively defined using a combination of principal components analysis, cluster analysis and discriminant functions analysis. All days from 1953 to 2004 were classified using Environment Canada observations from Calgary International Airport. The multivariate procedure successfully distinguished seasonal weather systems and ranked the importance of precipitation and snow bearing weather systems in terms of amount and frequency. Over the observation period warm, dry high pressure systems have become more frequent at the expense of frontal systems. Snow bearing weather systems have decreased in frequency resulting in less snow annually, but have not significantly influenced annual precipitation amount. Finally, in response to the positive phase of large scale synoptic indices, the winter frequency of warm weather systems increased, while cold frontal systems decreased.