Nonstationary impacts of the southern annular mode on Southern Hemisphere climate

• Main Authors: Silvestri, Gabriel Emilio, Vera, Carolina Susana
• Language: unknown
• Published: 2009
• Subjects: Antarctic Peninsula; Anticyclonic anomalies; Anticyclonic circulation; Austral spring; Australia; Circulation patterns; Moisture advection; Moisture convergence; Multi-decadal time scale; New zealand; Nonstationary; Positive correlations; Precipitation anomalies; South America; Southeastern South America; Southern annular mode; Southern Hemisphere; Temperature anomaly; Temporal stability; Moisture; Advection; Antarctic; Argentina; Austral; New Zealand; The Antarctic; Antarc*
• Online Access: https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_08948755_v22_n22_p6142_Silvestri; https://hdl.handle.net/20.500.12110/paper_08948755_v22_n22_p6142_Silvestri

The temporal stability of the southern annular mode (SAM) impacts on Southern Hemisphere climate during austral spring is analyzed. Results show changes in the typical hemispheric circulation pattern associated with SAM, particularly over South America and Australia, between the 1960s-70s and 1980s-90s. In the first decades, the SAM positive phase is associated with an anomalous anticyclonic circulation developed in the southwestern subtropical Atlantic that enhances moisture advection and promotes precipitation increase over southeastern South America (SESA). On the other hand, during the last decades the anticyclonic anomaly induced by the SAM's positive phase covers most of southern South America and the adjacent Atlantic, producing weakened moisture convergence and decreased precipitation over SESA as well as positive temperature anomaly advection over southern South America. Some stations in the Australia-New Zealand sector and Africa exhibit significant correlations between the SAM and precipitation anomalies in both or one of the subperiods, but they do not characterize a consistent area in which the SAM signal can be certainly determined. Significant changes of SAM influence on temperature anomalies on multidecadal time scales are observed elsewhere. Particularly over the Australia-New Zealand sector, significant positive correlations during the first decades become insignificant or even negative in the later period, whereas changes of opposite sign occur in the Antarctic Peninsula between both subperiods. © 2009 American Meteorological Society. Fil:Silvestri, G. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Fil:Vera, C. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.