INVESTIGADORES
SILVESTRI Gabriel Emilio
artículos
Título:
The relation between sea surface temperature at the subtropical south-central Pacific and precipitation in southeastern South America
Autor/es:
V. BARROS,; G. SILVESTRI
Revista:
JOURNAL OF CLIMATE
Editorial:
American Meteorological Society
Referencias:
Año: 2002 vol. 15 p. 251 - 267
ISSN:
0894-8755
Resumen:
This paper deals with the relationship between the interannual variability of sea surface temperature (SST)
and its associated atmospheric circulation and rainfall variability over southeastern South America (SSA), namely
the subtropical region east of the Andes between 208 and 408S, during the austral spring. Rainfall in SSA and
SST interannual variability is studied using canonical correlation analysis. The first two modes show the wellknown
warm-wet and cold-dry pattern between the equatorial SST and rainfall over most of this part of the
world. However, SST in the equatorial regions does not modulate rainfall variability among El Nino (EN) years
or among La Nina (LN) years. On the other hand, it does modulate this variability between EN and LN cases
as a whole and among neutral cases indicating that the SSA rainfall response to equatorial Pacific SST is not
linear over the observed SST range, having no dependence on the extremes of this range. In contrast, among
EN events, SST in the subtropical south-central Pacific (SSCP) modulates the seasonal rainfall over most of
SSA. Also, when all the years are considered, this SST has a correlation with precipitation of magnitude similar
to those corresponding to the SST in EN regions. Consistent with this, the circulation field has enhanced cyclonic
(anticyclonic) advection over subtropical SSA when SST in the SSCP is cold (warm).
SSTs in EN-3 or EN-3.4 regions and in the SSCP are negatively correlated, but their correlation is practically
zero when only EN cases or only neutral cases are considered, and very small in LN cases. This allows a
stratification analysis composing cases according to different SSTs in EN-3 and EN-3.4 regions with almost
constant SST in the SSCP and similarly according to different SST in the SSCP with approximately constant
SST in EN regions. The composite difference fields with constant equatorial SST and with constant SST in the
SSCP have a wave train in the Pacific similar to the ENSO-like pattern. Besides most of the ENSO circulation
signal at 200 hPa over mid- and high latitudes is associated with SST variability at the SSCP rather than with
SST variability in EN regions.
SST interannual variability is studied using canonical correlation analysis. The first two modes show the wellknown
warm-wet and cold-dry pattern between the equatorial SST and rainfall over most of this part of the
world. However, SST in the equatorial regions does not modulate rainfall variability among El Nino (EN) years
or among La Nina (LN) years. On the other hand, it does modulate this variability between EN and LN cases
as a whole and among neutral cases indicating that the SSA rainfall response to equatorial Pacific SST is not
linear over the observed SST range, having no dependence on the extremes of this range. In contrast, among
EN events, SST in the subtropical south-central Pacific (SSCP) modulates the seasonal rainfall over most of
SSA. Also, when all the years are considered, this SST has a correlation with precipitation of magnitude similar
to those corresponding to the SST in EN regions. Consistent with this, the circulation field has enhanced cyclonic
(anticyclonic) advection over subtropical SSA when SST in the SSCP is cold (warm).
SSTs in EN-3 or EN-3.4 regions and in the SSCP are negatively correlated, but their correlation is practically
zero when only EN cases or only neutral cases are considered, and very small in LN cases. This allows a
stratification analysis composing cases according to different SSTs in EN-3 and EN-3.4 regions with almost
constant SST in the SSCP and similarly according to different SST in the SSCP with approximately constant
SST in EN regions. The composite difference fields with constant equatorial SST and with constant SST in the
SSCP have a wave train in the Pacific similar to the ENSO-like pattern. Besides most of the ENSO circulation
signal at 200 hPa over mid- and high latitudes is associated with SST variability at the SSCP rather than with
SST variability in EN regions.
SST interannual variability is studied using canonical correlation analysis. The first two modes show the wellknown
warm-wet and cold-dry pattern between the equatorial SST and rainfall over most of this part of the
world. However, SST in the equatorial regions does not modulate rainfall variability among El Nino (EN) years
or among La Nina (LN) years. On the other hand, it does modulate this variability between EN and LN cases
as a whole and among neutral cases indicating that the SSA rainfall response to equatorial Pacific SST is not
linear over the observed SST range, having no dependence on the extremes of this range. In contrast, among
EN events, SST in the subtropical south-central Pacific (SSCP) modulates the seasonal rainfall over most of
SSA. Also, when all the years are considered, this SST has a correlation with precipitation of magnitude similar
to those corresponding to the SST in EN regions. Consistent with this, the circulation field has enhanced cyclonic
(anticyclonic) advection over subtropical SSA when SST in the SSCP is cold (warm).
SSTs in EN-3 or EN-3.4 regions and in the SSCP are negatively correlated, but their correlation is practically
zero when only EN cases or only neutral cases are considered, and very small in LN cases. This allows a
stratification analysis composing cases according to different SSTs in EN-3 and EN-3.4 regions with almost
constant SST in the SSCP and similarly according to different SST in the SSCP with approximately constant
SST in EN regions. The composite difference fields with constant equatorial SST and with constant SST in the
SSCP have a wave train in the Pacific similar to the ENSO-like pattern. Besides most of the ENSO circulation
signal at 200 hPa over mid- and high latitudes is associated with SST variability at the SSCP rather than with
SST variability in EN regions.
8 and 408S, during the austral spring. Rainfall in SSA and
SST interannual variability is studied using canonical correlation analysis. The first two modes show the wellknown
warm-wet and cold-dry pattern between the equatorial SST and rainfall over most of this part of the
world. However, SST in the equatorial regions does not modulate rainfall variability among El Nino (EN) years
or among La Nina (LN) years. On the other hand, it does modulate this variability between EN and LN cases
as a whole and among neutral cases indicating that the SSA rainfall response to equatorial Pacific SST is not
linear over the observed SST range, having no dependence on the extremes of this range. In contrast, among
EN events, SST in the subtropical south-central Pacific (SSCP) modulates the seasonal rainfall over most of
SSA. Also, when all the years are considered, this SST has a correlation with precipitation of magnitude similar
to those corresponding to the SST in EN regions. Consistent with this, the circulation field has enhanced cyclonic
(anticyclonic) advection over subtropical SSA when SST in the SSCP is cold (warm).
SSTs in EN-3 or EN-3.4 regions and in the SSCP are negatively correlated, but their correlation is practically
zero when only EN cases or only neutral cases are considered, and very small in LN cases. This allows a
stratification analysis composing cases according to different SSTs in EN-3 and EN-3.4 regions with almost
constant SST in the SSCP and similarly according to different SST in the SSCP with approximately constant
SST in EN regions. The composite difference fields with constant equatorial SST and with constant SST in the
SSCP have a wave train in the Pacific similar to the ENSO-like pattern. Besides most of the ENSO circulation
signal at 200 hPa over mid- and high latitudes is associated with SST variability at the SSCP rather than with
SST variability in EN regions.