Use of Cluster Analysis to Define Periods of Similar Meteorology and Precipitation Chemistry in Eastern North America. Part I: Transport Patterns

Abstract

Cluster analysis has been applied to transport vectors, derived from three years of daily backwards trajectories, in order to define a synoptic climatology of representative three-day periods of air mass movement. The resulting clusters represent groups whose mean air mass transport fields are statistically different from one another and correspond to the types of high and low pressure patterns seen on daily weather maps. Seasonal differences were evident in the frequency of occurrence of each cluster. The clusters were relatively insensitive to changes in number of sites or years used; however, different clustering methods yielded somewhat different clusters. Ward's method yielded clusters with more or less equal numbers while other methods tended to produce one large cluster and a series of ?outlier? clusters. Cluster analysis was useful in the computer-assisted classification of spatial patterns of weather data and should be considered for use along with more widely used synoptic climatological tools such as principal component analysis.