Abstract
The relationship between the slow components of the hemispheric barotropic flow and the barotropic effects on the flow due to the presence of extra-tropical cyclones is investigated by establishing multivariate regression models. These regression models are formulated in terms of the modes that are obtained from a canonical correlation analysis between the two variables. 8 winters of hemispheric spectral observations are used for the analysis which is carried out on the basis of unfiltered time series for the barotropic streamfunction and the eddy effects. It turns out that the regression models exhibit some local skill (up to 30%) over the Atlantic sector to predict the eddy effects in terms of the planetary streamfunction. Furthermore, it is found that this skill is mainly associated with the largest planetary scales of the eddy effects. The dynamical flow regimes that contribute to this skill are also evaluated. It is found that they comprise episodes of Atlantic blocking as well as cases when the flow over the Atlantic is governed by an anomalous zonal jet. The characteristic time-scale for those episodes is estimated as about 10 days.
© 1990 Werner Metz, published by Stockholm University Press
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