This satellite image shows Africa in January. The position of the equatorial trough of low pressure, also referred to as the Innertropical Convergence Zone (ITCZ), has been marked on the satellite image. The blue arrows indicate the dominating wind directions.
Vegetation Zones Distinctive vegetation zones have formed in Africa corresponding to the distribution and levels of precipitation. These zones are clearly visible on the satellite image of Africa: the dark green stripe of dense vegetation close to the equator differs from the poleward regions; the lighter colour indicates little or no vegetation. The green stripe in the centre of Africa is interrupted only at the Horn of Africa. Whereas there are isolated areas of green in the north of the continent (in the Atlas Mountains and at the Niger Delta), in the south, there are green patches both on the coast of the Indian Ocean and the southern tip of Africa. The evergreen lowland forests in Central Africa cover an area extending about 1100 km from East to West and 800 km from North to South. They grow to an average height of around 30 m, above which, the rainforest "giants" tower at a height of up to 40 m. The tropical lowland forests are characterised by their remarkable biodiversity. A further characteristic is the evenly spread germination, flowering and leaf fall throughout the year. The forest gives the impression of being "evergreen". The rainforest is bordered to the north and south by an almost 100 km wide belt of semi-evergreen, partially deciduous rainforest, also referred to as evergreen seasonal rainforest. Bordering on these forests are the savannas, which vary according to the number of dry months (three to seven) and the average annual rainfall (4001600 mm): ranging from wet savanna, dry savanna to thorn savanna. The wet savanna consists of forests that grow to a height of 1820 m alternating with 1.52 m high grasslands and light woodlands. Further polewards is the dry savanna, where it rains fewer than six to seven months a year and the average annual rainfall is less than 1000 mm. Here, is the seat of the rain-green Miombo Forests, which grow between 1012 m on the plateaus of southern Central Africa. The thorn savanna follows with an annual rainfall of 250500 mm and only 24.5 wet months a year. It is characterised by sparse grass cover and thorn bush. The semi-deserts further polewards are covered in grass and thorny scrub. During very rare precipitation, seeds lying dormant in the soil will germinate resulting in rain vegetation. Isolated occurrences of grass and lichen can also be found in the neighbouring deserts. At the Mediterranean northern and southern borders of Africa, sclerophyllous vegetation is common and widespread.
Differences in Vegetation in July Due to the southern location of the ITCZ and resulting rainy season in the southern half of Africa, the southern savanna regions are greener than in July. Conversely, in the northern hemisphere, the Sahel is drier than in July and is therefore brown on the satellite image. H. Kiegel, Ü: J. Moar, C. Fleming