East Africa is much drier than other tropical land regions, including the Amazon and Congo rainforests.
East Africa is much drier than other tropical land regions, including the Amazon and Congo rainforests. The geography of East Africa was always thought to make the region dry and susceptible to drought, but the precise mechanism has been elusive until now. This research demonstrates the east to west river valleys are a crucial factor in the low annual rainfall.
Dr Callum Munday, from the REACH programme at Oxford’s Smith School, who led the study, explains, ‘Normally, when we think of valleys and water, we think of the rivers that flow along the ground. In East Africa, deep valleys, such as the Turkana Valley, channel strong winds and create invisible rivers in the sky. These invisible rivers carry millions of tonnes of water vapour, the key ingredient for rainfall.’
The team, which had previously travelled to Kenya to measure the ‘invisible rivers’ with weather balloons, wanted to see how the valleys affect climate across the whole of Africa. To do this, they devised a series of model experiments which changed the geography of the rift system by progressively filling in the river channels.
Read More: University of Oxford