New research shows that precipitation in East Africa will increase significantly as greenhouse gases increase. Pictured is Lake Nakuru, Kenya. Credit: Flickr, Snake3yes.
According to research led by the University of Texas at Austin, seasonal rainfall is expected to increase significantly in the next few decades in East Africa in response to increased greenhouse gases.
The study, published in July in Climate dynamics, uses high-resolution simulations to find that the amount of precipitation during the rainy season known as the “short rain” could double by the end of the century, continuing a trend that has been observed in recent years. The season known as the “long rains” on the other hand, is expected to remain stable according to the new projections. These results are in contrast to previous analyzes that linked global warming to dry conditions that occurred earlier this century.
“There are two East African rainy seasons with varying degrees of sensitivity to greenhouse gases,” said Kerry Cook, a professor in the Department of Geological Sciences at Jackson School of Geosciences. “Our paper shows that short rains will continue to increase – in fact, floods and locusts have already occurred instead – and that there is no dry trend for long rains.”
Both the transport of water vapor by atmospheric circulation and the distribution of rain are sensitive to differences between ocean and land temperature. These differences occur because oceans heat up and cool more slowly than land due to differences in heat capacity.
As the short rains develop, typically with a peak in November, the circulation of the southern hemisphere is in a summer pattern, with high pressure over the ocean and low pressure over land in the subtropics, setting up a circulation pattern that is more humid over East -Africa funnelt. It is this rainy season that is more sensitive to climate change due to greenhouse gases.
The region’s long rains, on the other hand, seem to be less sensitive to greenhouse gas constraints. This season occurs from March to May, and reaches a peak near the spring equilibrium of the northern hemisphere, when continental low pressure lies at the equator.
The newly published simulations have a resolution of 30 kilometers that resolves the complex East African topography, and more accurately represent currently observed precipitation and seasons than coarser resolution global models. Simulations of precipitation until 2050 are consistent with currently observed amounts of precipitation and seasonal area. These results show that the pattern of long rains does not change. But the short rainfall is increasing: the November precipitation over East Africa will increase by about one third by 2050 and double by 2100.
“This study shows people are planning ahead in East Africa,” Cook said. “But future work will have to see how additional rainfall will be delivered, because, if it is as intense as in current observations and continues to affect agriculture, infrastructure development will be important.”
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Kerry H. Cook et al, Seasonal asymmetry of equatorial East African rainfall projections: understanding differences between the response of the long rains and the short rains to elevated greenhouse gases, Climate dynamics (2020). DOI: 10.1007 / s00382-020-05350-y
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Citation: Climate change projected to increase seasonal East African rainfall (2020, August 11) Retrieved August 12, 2020 from https://phys.org/news/2020-08-climate-seasonal-east-african-rainfall.html
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