Empirical Orthogonal Functions and Multiple Flow Regimes in the Southern Hemisphere Winter

John D. Farrara Climate Dynamics Center and Department of Atmospheric Sciences, University of California, Los Angeles, California

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Michael Ghil Climate Dynamics Center and Department of Atmospheric Sciences, University of California, Los Angeles, California

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Carlos R. Mechoso Climate Dynamics Center and Department of Atmospheric Sciences, University of California, Los Angeles, California

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Kingtse C. Mo Climate Analysis Center, National Meteorological Center, NWS/NOAA, Washington, DC

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Abstract

We present a new empirical orthogonal function (EOF) analysis of winter 500 mb geopotential height anomalies in the Southern Hemisphere. An earlier EOF analysis by two of the present authors prefiltered the anomalies to exclude wavenumbers 5 and higher; we do not. The different preprocessing of data affects the results. All three distinct planetary flow regimes identified in the winter circulation of the Southern Hemisphere by a pattern correlation method are captured by the new set of EOFs; only two of those regimes were captured by the earlier set. The new results, therefore, lend further support to the idea that EOFs point to distinct planetary

Abstract

We present a new empirical orthogonal function (EOF) analysis of winter 500 mb geopotential height anomalies in the Southern Hemisphere. An earlier EOF analysis by two of the present authors prefiltered the anomalies to exclude wavenumbers 5 and higher; we do not. The different preprocessing of data affects the results. All three distinct planetary flow regimes identified in the winter circulation of the Southern Hemisphere by a pattern correlation method are captured by the new set of EOFs; only two of those regimes were captured by the earlier set. The new results, therefore, lend further support to the idea that EOFs point to distinct planetary

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