Eigenvector Analysis of the Vertical Velocity Field Over the Eastern Canadian Arctic

Abstract

To identify the predominant physical controls on the synoptic activity in the eastern Canadian Arctic, a limited area model has been applied to NMC grid data to compute the total vertical velocity and the component fields individually attributable to the differential advection of vorticity, the thickness advection, the release of latent heat, the effects of the surface enthalpy flux, and the influence of friction and orography at the surface. For a 234-day sample from the winter and summer of 1973, the major synoptic systems are identified by pattern (eigenvector) classification of the 85 cb total vertical velocity fields. For each synoptic pattern, the average physical processes responsible for the vertical circulation are determined by empirical comparison of the patterns in each component field of vertical velocity with the pattern of total vertical velocity. The physical linkages proposed are verified by subjective analysis of individual cases.