Characterisation of hydrological droughts in central-north Argentina and its atmospheric and oceanic drivers

CARAGUNIS J.I., RIVERA J. A., PENALBA O. C

CLIMATE RESEARCH

INTER-RESEARCH

Lugar: Oldendorf/Luhe; Año: 2020

0936-577X

Low streamflows caused by natural and anthropogenic forcings affect ecosystemsand societies, especially on large timescales. We analysed the main basins of central-northArgentina (CNA) using centennial streamflow data. This study is focussed on describing spatialand temporal variability of hydrological drought events, and evaluating the atmospheric andoceanic drivers under hydrological drought conditions. The Standardized Streamflow Index in theperiod 1919−2014 was applied, sectored by 4 major basins. The western Argentinian rivers (ColoradoBasin, CB) have shown increasing drought events since the 1940 decade, while in the east,a sharp decrease occurred from 1970 onwards. Extreme drought events occurred over CB and LaPlata Basin (LPB) during the periods 1966−1972 and 2010−2014. Atmospheric and oceanic patternsunder hydrological drought conditions show anticyclonic anomalies over the South PacificOcean (SPO), cyclonic sub-polar anomalies and La Niña-like conditions with warm sea surfacetemperature anomalies (SSTAs) in SPO for the western basins. Over LPB, a strong cold SSTA inthe tropical south-western Atlantic Ocean is positioned in phase with the cyclonic anomalies. Atmid-latitudes, a warm SSTA and anticyclonic anomalies are detected. Water vapour transportcomposites show southerly winds and drier conditions for northern and eastern Argentina, andweakening of westerly winds with drier atmosphere for western rivers. These results deepen ourknowledge of natural forcings related to hydrological drought events in CNA and in the predictabilityof such complex natural hazards.