J. Geophys. Res. 116, D20109 (2011)

The El Niño/Southern Oscillation (ENSO) is a coupled atmosphere–ocean circulation occurring over the tropical Pacific Ocean, and is one of the main sources of the Earth's climate variability. Its extremes — the El Niño (warm phase) and La Niña (cold phase) — both affect rainfall in many parts of the world.

To better understand how ENSO influences droughts, Sergio Vicente-Serrano, of the Pyrenean Institute of Ecology (IPE-CSIC) in Zaragoza, Spain, and co-workers looked globally at the role of the ENSO phases on various drought types associated with hydrological, agricultural and environmental impacts.

The results indicate that the number of regions and months affected, and the total surface area with drought is much higher for El Niño phases than for La Niña phases. In large areas of America and Eastern Europe, ENSO contributes to droughts on short timescales of one to three months at the beginning of the events. In South Africa, Australia and Southeast Asia the effects were more obvious some months later, and at longer timescales. The authors suggest that the large temporal lag between the development of ENSO phenomena and the identification of drought conditions detected in the study may help in forecasting dry conditions in some regions up to one year before their occurrence, potentially improving early warning and adaptation to drought conditions.