INVESTIGADORES
PENALBA Olga Clorinda
congresos y reuniones científicas
Título:
Regional aspects of drought in southern South America.
Autor/es:
RIVERA J, PENALBA O.C
Lugar:
Montevideo
Reunión:
Conferencia; WCRP-Conference for Latin America and the Caribbean, developing, linking, and applying climate knowledge.; 2014
Resumen:
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As droughts
are regional in nature and commonly cover large areas and extend for long time
periods, it is important to study such events within a regional context. This
study aims assess the regional aspects of drought temporal variabilities in
southern South America (SSA), at different time scales, for the period
1961-2008. In order to define drought conditions, we used the standardized
precipitation index (SPI), which is a simple, powerful and flexible index that was
widely used in SSA. The SPI was calculated at time scales of 3 (SPI3) and 12
months (SPI12), which represents short- and long-term droughts, respectively.
Rotated principal components analysis was used to identify spatially homogeneous
regions with different precipitation temporal variabilities. We obtained for
both time scales seven homogeneous regions, which are climatically consistent. Based
on the regional SPI, drought mayor events were identified in the decades of
1960 and 1970 in most of the regions, although some record breaking events were
recorded during recent decades. Spectral and wavelet analysis were used to
identify the main modes of variability for each region. The regional SPI3 time
series are characterized with significant seasonal variabilities; while the
SPI12 time series possess significant inter-annual variabilities in the range
of 1 to 5 years. In order to identify the regional influence of El Niño and La
Niña events on the precipitation time series, we calculated the mean SPI values
for the El Niño and La Niña years and assessed its significance through
bootstrap analysis. We found coherent and significant precipitation responses
to ENSO phases in most of the seven regions, mainly for the SPI12 time series.
The precipitation response to La Niña events is characterized with
precipitation deficits, although the signal is not as clear as in the cases of
El Niño events. Lagged correlations between the SPI regional time series and
the Niño 3.4 index were performed in order to identify the potential of the
ENSO signal for seasonal forecasting. The ENSO related indices can be useful
for seasonal and inter-annual drought forecasts, and together with a regional
drought monitoring system will be extremely helpful for drought preparedness
and early warning.
