Saturday, March 17, 2012

Study links African drought to Pacific sea temperature

Gilbert Nakweya in Environmental Expert: Researchers in the United States have found a link between low rainfall in East Africa during the March-May rainy season, and changes in sea surface temperature in the tropical Pacific Ocean. The region endured a catastrophic drought last year. The lack of rain in 2010 during the October-December rain season — known as the 'short rains' — was widely anticipated due to an established link between these rains and El Niño and La Niña events.

But researchers say last year's failure of the region's other key rains — the so-called 'long rains', which tend to fall between March and May – was much harder to anticipate. 'Historically, the long rains have not shown a strong relationship to El Niño and La Niña the way the short rains do,' Bradfield Lyon, a co-author of the study and climate scientist at Columbia University's Earth Institute, told SciDev.Net.

Lyon and colleague David DeWitt have now identified a link between the 'long rains' and ocean temperatures in the Pacific.

They noted that in 1999, there was an abrupt change in Pacific ocean surface temperatures. The western Pacific surface became warmer, while surface temperatures in the eastern Pacific became cooler. Historical climate observations were combined with climate model experiments, and the authors concluded that these changes were strongly linked to 'a similarly abrupt decline in East African long rains that occurred around that time'...

A NOAA diagram of a generic La Nina state

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