INVESTIGADORES
VERA Carolina Susana
artículos
Título:
Differences in El Niño response over the Southern Hemisphere.
Autor/es:
VERA, CAROLINA; SILVESTRI, GABRIEL; BARROS, VICENTE; CARRIL, ANDREA
Revista:
JOURNAL OF CLIMATE
Editorial:
American Meteorological Society
Referencias:
Lugar: Boston; Año: 2004 vol. 17 p. 1741 - 1753
ISSN:
0894-8755
Resumen:
Southern Hemisphere (SH) circulation conditions during austral springs of ENSO events are examined. Based
on previous knowledge that SST variations over the subtropical south-central Pacific (SSCP) region are linked
to differences among El Nino (EN) events, a stratification of the springs associated with EN events was performed
according to SST conditions over the El Nino-3.4 sector and over the SSCP region. The EN events associated
with cold conditions in the SSCP (WC) exhibit enhanced convection not only in the intertropical convergence
zone over the central equatorial Pacific but also in the South Pacific convergence zone (SPCZ) extended southeastward
into the subtropical regions. The resulting heating forcing intensifies a localized overturning cell, which
is associated with an anomalous Rossby wave source in the central South Pacific extratropical region. Neither
the Rossby wave source nor the associated wave pattern is evident during EN events associated with warm
conditions in the SSCP and inactive SPCZ (WW).
The basic features that characterize the differences in the EN response over the South Pacific can also be
identified through the analysis of the SPCZ activity over the central South Pacific. The fact that variations in
SPCZ activity lead SST anomaly changes in the SSCP would indicate that the differences in the EN response
over the SH might be mainly driven by atmospheric changes, which induces extratropical SST anomalies.
The differences in the circulation anomalies that characterize both types of EN response over the SH were
further explored through the analysis of the activity of the three leading modes of circulation variability. The
combined effect of the three leading patterns describes in some extent the intensification (weakening) of the
cyclonic circulation anomaly observed over the southeastern Pacific in WC (WW), associated with an active
(inactive) SPCZ. In particular, the interdecadal variability observed in the Pacific by many previous studies
influences the circulation response to ENSO over the SH, mainly through changes in the activity of the SH
annular mode.