INSTITUTO ARGENTINO DE NIVOLOGIA, GLACIOLOGIA Y CIENCIAS AMBIENTALES
Unidad Ejecutora - UE
congresos y reuniones científicas
Spatial patterns of drought affected area and trends in southern South America
OLGA PENALBA; JUAN ANTONIO RIVERA
Conferencia; WCRP Conference for Latin America and the Caribbean: Developing, linking and applying climate knowledge; 2014
World Climate Research Programme
Under current global climate changes, it is necessary to analyze the spatial and temporal variabilities of drought events, in order to improve the water resources management and mitigate their impacts. From the point of view of vulnerability, it must be considered the situations where a large portion of a region is under drought conditions. In this study we analyzed the evolution of the percentage of locations with drought conditions in southern South America (SSA) during 1961-2008. We used precipitation data from 56 meteorological stations belonging to Argentina, Brazil and Paraguay, whose spatial distribution was homogeneous in order to obtain a representative percentage of drought affected area. Drought conditions were identified by the standardized precipitation index (SPI). The SPI was computed for time scales of 1, 3, 6, 9 and 12 months, which allowed monitoring of different types of drought ?meteorological, agricultural and hydrological-. Given the non-linearity of precipitation variations over the last century, we calculated both linear and non-linear trends for the analysis of the evolution of the percentage of locations with drought conditions. Linear trends were calculated with the Sen?s estimator, while non-linear trends were identified through the residuals of the empirical decomposition modes (EDM). The percentage of stations with drought tends to decrease approximately 3% per decade, considering deficits of 12 months, while this decrease is in order of 1% per decade on a scale of 3 months. This fact indicates that as the time scale increase, the area affected by drought decreases further. On a 12-months time scale, the droughts of 1962 and 1988-1989 affected more than 60% of the stations; while on the time scale of 6 months, this occurred during the droughts of 1962, 1968 and 1971. The largest spatial extents of droughts were recorded during La Niña events. This result was verified considering a composite of the SST anomalies during the months with more than 30% of stations with drought conditions. The time series of the drought affected area exhibit a high degree of non-linearity, with a reversion in their sign after 1990s. The increase in the drought affected area since 2000 in all time scales is remarkable, reaching a 40% of surface during 2008. These trends have a significant impact on agricultural production and hydropower generation in the region, therefore, its continuous monitoring and its interpretation through methodologies such EDM are necessary.