Ferrel Circulation variability in the Southern Hemisphere and its linkages with tropical and subtropical sea surface temperature

Abstract

[1] Ferrel Circulation variability in the Southern Hemisphere and its linkages with the tropical and subtropical sea surface temperature (SST) for the period 1979–2009 are investigated. Two dominant spatiotemporal patterns of Ferrel Circulation variability are identified, one showing opposing change between the poleward and equatorward portion of ∼48°S of the Ferrel Circulation (EOF1) and the other showing a rather uniform change of the Ferrel Circulation (EOF2). An increasing trend is found for the EOF1, indicating the strengthening (weakening) of the poleward (equatorward) portion of the Ferrel Circulation for the past three decades, although the Ferrel Circulation strength index suggests an overall weakening of the Ferrel Circulation. Distinctly different forms of tropical and subtropical ocean variability are connected to the two dominant modes of Ferrel Circulation variability. Statistical analysis suggests that the EOF1 has a close association with the warming trend of the tropical and subtropical oceans for the past three decades, whereas the EOF2 is significantly correlated with SST variability in the Pacific that resembles the La Nina Modoki.