Sea Level Pressure Patterns over Eastern North America, 1899–1976

Abstract

Eigenvector analysis was carried out on monthly mean sea level pressure over eastern North America for the period 1899–1976 to determine whether the hemispheric circulation epochs since the turn of the century (as defined by others) also were periods with differing circulation patterns over the North American sector, and what the character of these regional circulation episodes has been. The results show that the episodes were significantly different from each other due to interannual and intraannual persistence of anomalous sea level pressure features. The most important anomalous features were similar to the circulation components characteristic of particular seasons. Consequently, the most important variations in sea level pressure over eastern North America have been variations in the shape of the seasonal cycle. The contribution of unusual circulation patterns to the differentiation between episodes has been small.