noun, Pathology. 1. the accumulation of excessive ketones in the body, as in diabetic acidosis. Origin of ketosis. 1915-1920.
Climate zones of Africa, showing the ecological break between the hot desert climate of the Sahara Desert (red), the hot semi-arid climate of the Sahel (orange) and the tropical climate of Central and Western Africa (blue).
The Sahara is located in a climatic divide. The Intercontinental Convergence Zone moves up from the south, but stops before the center of the Sahara, and consequently hardly carries any rain. Similarly, the winter rainfall of North Africa does not reach far south enough to regularly bring rain to the central Sahara.