Geophys. Res. Lett. http://doi.org/s62 (2014)

Credit: © ZHIEN HUANG / ALAMY

Southern China has experienced more frequent autumn droughts during the past two decades. Observations show that precipitation has been greatly reduced since 1990, during this season of transition from the wet summer monsoon to the dry winter months.

Wenjun Zhang, of Nanjing University of Information Science and Technology, China, and co-workers studied the causes behind this precipitation shift using observations of rainfall, sea surface temperature and atmospheric circulation. They found that there has been an increase in central Pacific El Niño events — where the sea surface temperature anomaly is found in the central Pacific, compared with the more traditional, or eastern Pacific, location.

This shift in the El Niño location influences precipitation over Southern China, with very low precipitation during central Pacific events and excess precipitation during eastern Pacific events. As global warming may cause an increase in central Pacific El Niño events, this could have serious water resource implications for the region.