Definitions of drought vary between countries; in the British Isles definitions can be very precise – 15 consecutive days each with less that 0.25mm of rainfall. In Africa drought is defined as a period where evapotranspiration exceeds precipitation and soil moisture is depleted.
Distinctions can be made between short term dry seasons (to which human and natural systems can adapt) and long-term droughts that can affect areas for several years with disastrous consequences.
Seasonal Drought The Hadley cell dominates precipitation patterns within the tropics leading to seasonal drought (wet and dry seasons) in the savannah regions as the Inter-Tropical Convergence Zone (ITCZ) migrates north and south.
Nomads of the Savanna Turkana, an indigenous people who migrate with the seasonal rains. They are nomadic pastoralists.
Vegetation of the Savanna Boabab tree. Thick truck store water for use during the long dry season. The fire proof bark also provides protection during this time.