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Atmospheric response to South Atlantic SST dipole
Author(s) -
Haarsma Reindert J.,
Campos Edmo J. D.,
Molteni Franco
Publication year - 2003
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2003gl017829
Subject(s) - baroclinity , intertropical convergence zone , climatology , geology , latent heat , tropical atlantic , barotropic fluid , gulf stream , hadley cell , atmospheric sciences , sea surface temperature , general circulation model , climate change , oceanography , meteorology , physics , precipitation
Recent analyses of historical data and output of numerical models have suggested a dipolar mode of decadal variability in the South Atlantic. In this work, the the atmospheric response to such anomalous SST dipole in the South Atlantic is investigated with a numerical model. The results show a deep baroclinic response over the equatorward pole and a shallow equivalent barotropic response over the poleward pole. The baroclinic response is strongest during the austral summer. It affects the meridional circulation over the tropical Atlantic with anomalous downward motion north of the ITCZ and anomalous ascending motion southward of it, resulting in a southward shift of the ITCZ. The ITCZ response is enhanced due to a positive feedback induced by anomalous low level convergence of moisture. Changes in cloud cover counteract the variations in latent heat flux north of the ITCZ, thereby prohibiting the generation of an SSTA of opposite sign as suggested by the wind‐evaporation‐SST (WES) feedback.