Savannah Ecology 1/5

Africa sits on the equator, which passes through Kenya. The sun moves from overhead at the tropic of capricorn in late December, to overhead at the tropic of cancer in late June, being over the equator in late March and late September. As the sun moves, it pulls water off the oceans in its wake, with a time lag of about one month, to create the Intertropical Convergence Zone. North of the northern reach, and south of the southern reach of this zone is very dry. But between the southern and northern limits of the zone, and for some distance outside these limits, the ITCZ brings seasonal rains. At the extremes, the year tends to be divided into one rainy season, and one dry one. Around the equator, as the sun passes twice, there are two wet seasons. There is a gradient corresponding to rainfall, of desert to dry (grass and shrub) savannah to woodland savannah. Where west Africa bulges out the zone is squashed, and there is tropical rain forest, which is very wet, while the corresponding east of the continent, where Kenya lies, is relatively dry and the dry savannah reaches further south there. In Kenya, the 'long rains' are from late March to mid-June, and the 'short rains' from late October to mid-December. However, these rains are not guaranteed, and may be absent, weak, or join to make one long rainy season. These plans give a rough outline of the vegetation and rain pattern.