East Africa is about as far from the Central Pacific Ocean as a person can get without leaving the planet. And yet, as the Pacific chills, drought grips East Africa in classic La Niña style. Because of global teleconnections, La Niña has to power to affect the weather half a world away.
This image, from France’s SPOT satellite, shows severe drought in Somalia, Kenya, and southern Ethiopia. The image is a vegetation anomaly, a measure of how well plants were growing compared to average. This image compares plant growth between January 1 and 10, 2011, compared to the average growth for January between 1999 and 2009. Widespread brown is an indication that plant growth slowed, with fewer photosynthesizing leaves than average.
A typical December in much of East Africa is rainy, the end of a 3-month rainy period before a dry stretch that usually lasts from January to March. In 2010, however, the rains were erratic and ended in early November. December was hot and dry. Two thirds of Somalia received less than 75 percent of normal rainfall, reported the UN-funded Somalia Water and Land Information Management program. Without rain, the pastureland and cropland in the region produced poor crops and little grass for livestock, leading to food shortages and livestock deaths, said the United Nations.
Poor or failed rainfall during the short rain growing season (October to December) is a classic La Niña signal. In late 2010, a strong La Niña cooled surface waters in the central and eastern Pacific Ocean, while allowing warmer water to build in the eastern Pacific. The pool of warm water in the east intensifies rains in Australia, the Philippines, and Indonesia. Domino-style, this pattern also increases the intensity of westerly winds over the Indian Ocean, pulling moisture away from East Africa toward Indonesia and Australia. The result? Drought over most of East Africa andfloods and lush vegetation in Australia and other parts of Southeast Asia.
1. References
2. Anyamba, A., Tucker, C.J., Mahoney, R. (2002). El Niño to La Niña vegetation response patterns over East and Southern Africa during 1997-2000 period. Journal of Climate, 15, 3096-3103.
3. Ropelewski, C.F., Halpert, M.S. (1987) .Global and regional scale precipitation patterns associated with the El Niño/Southern Oscillation. Monthly Weather Review, 115, 1606-1626.
4. Somalia Water and Land Information Management. (2011, January 17). Somalia drought watch. Published on ReliefWeb. Accessed January 19, 2011.
5. United Nations Office for the Coordination of Humanitarian Affairs. (2011, January 13). La Niña drought response by sectors. Published on ReliefWeb. Accessed January 19, 2011.
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