Characterizing the zonally asymmetric component of the SH circulation |
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| Authors: | William R Hobbs Marilyn N Raphael |
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| Institution: | (1) Department of Geography, University of California Los Angeles, 1255 Bunche Hall, Los Angeles, CA 90095, USA |
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| Abstract: | Much research concerning the Southern Hemisphere (SH) zonally asymmetric circulation has focused on the Pacific-South American
mode (PSA) or the major zonal waves. However, these large-scale decompositions may mask important local variability. In this
paper the month-to-month variability explained by the zonal waves 1 and 3 is examined, and an alternative representation of
the SH circulation is presented based on two quasi-stationary anticyclones in the sub-Antarctic western hemisphere. These
anticyclones are related to the zonal waves, but features of their variability are masked by the zonal wave decomposition;
in particular, the anticyclones’ strengths are not positively covariant. They are also compared with the leading Principal
Components of the SH atmosphere. We show that they capture variance independent of the Southern Annular Mode. Additionally,
they explain a generally greater fraction of the variability than the PSA, and in a manner that also includes information
regarding spatial variability. These results have implications for analysis of the atmospheric-forcing of western Antarctic
climate. |
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