Influence of aridity on vegetation

The aridity index measures the adequacy of the precipita - tion to satisfy vegetation water requirements Large areas of northern and southern Africa are dry with an aridity index of less than 065 In contrast, central Africa is more humid, with an aridity index that exceeds 065 Variations in dry - ness reflect Africa’s geography and topography For example, hyperarid zones, such as the Sahara and Namibia deserts, which receive less than 100 mm of precipitation annually, correspond to prevailing high pressure systems preventing cloud formation over the western edges of subtropical areas Equatorial areas are more humid than other parts of Africa, because low pressure systems and strong air convection con - dense the moisture into clouds, which lead to high precipi - tation Dry northeast monsoon winds blowing in from the Arabian Desert make eastern Africa less humid than other equatorial regions, such as central Africa and the Gulf of Guinea, to the west Mountains, such as Mt Kenya and Mt Kilimanjaro, block the passage of rain-producing weather systems, creating more humid conditions in highland areas and drier conditions on the shielded side of these highlands

---

• View source