Climate

The climate graphs for a station in Africa shows that there is not very much change in temperature between the seasons, there is merely around 12*C difference from highest to lowest. There is a temperature of around 25*C in the dry season, around 37*C in the beginning of the wet season and around 28*C in the middle of the wet season.

There is no rain fall in between January and April, making winter the dry season, but in March the rainfall gradually increases and reaches its peak in July making summer the wet season. After July the rainfall gradually decreases again.
From this we can determine that the station in Africa has a Savannah climate.

The pattern of temperature on the graph has two curves, meaning the temperature raises and decreases in two waves. The Savannah climate is sometimes described as the transition climate between tropical and desert climate, therefore there are both very wet seasons with a cooler temperature and very dry seasons with a hotter temperature. This change in temperature is caused by the movement of the overhead sun. The temperature increases as the sun takes a more vertical position in the early wet season. This can be seen as the first curve on the graph.
The second curve is caused by the fact the hot temperature causes the very moist air to rise in convectional currents. This means that when the hot air reaches its dew point the water condenses into water droplets causing cumulus clouds. The second curve shows this cloud cover, which naturally blocks out some of the sun decreasing the temperatures.

The annual distribution of rainfall is very uneven. There is what is known as a wet season and a dry season. The wet season occurs the sun takes a vertical position causing the hot moist air to rise in convectional currents. When the hot air reaches its dew point it causes heavy rainfall. This sort of rainfall resembles that of a tropical environment.
The dry season occurs when the sun moves southwards and when the equatorial low pressure affects the area through prevailing trade winds. This winds are blowing in from the east are very dry, as the moisture has been lost throughout blowing across the land (most savannah climates are located far inland). This sort of lack of rainfall resembles that of a desert environment.

The vegetation across a Savannah varies due to its variation in temperature and rainfall. Vegetation such as dense woodland can be found where the savannah turns into tropical rainforest. The closer one gets to the desert from here the more spare the vegetation becomes, as such the vegetation changes into typical savannah grasslands with scattered trees and then drought resistant bushes where the desert begins.
Vegetation adapts differently depending on where on the savannah climate it is located. Where rainfall is kept to minimum, trees may for example shed their leaves and produce a waxy leafs to keep transpiration and loss of water to a minimum. Plants in this region also have long roots to tap the underground water supplies.
Vegetation which is located on the verge of the tropical rainforest receives more water. Here the vegetation grows fairly freely with much sunlight and rainfall, but it has been altered rather than adopted by e.g. electrical storms and pressure on land due to population growth.

Figure 6 shows how the plants and vegetation in tropical rain (evergreen) forest has adapted to the climate in which they are found. The tropical climate has continuous high temperature, continuous rainfall and an ever growing season to which its vegetation has to adapt. Despite the fact that there is much sunlight coming in to the tropical rainforest the majority of the light only reaches the top layers, due to the very high density of vegetation.
The vegetation in these sorts of areas grows in distinct layers due to this. All trees adapt to reach the as much sunlight as possible. Some of these adaptations include no braches on the lower levels, straight trunks and large buttress roots to for support. This enables the trees efforts to grow as tall as possible. To handle the heavy rainfall leaves also have drip-tips to shed the water fast. Lianas grow around large trees for support to reach as high as possible to the sunlight.
The lower layers of sparse undergrowth have to adapt to extreme rainfall and little sunlight and therefore have the tendency to grow near rivers and in forest clearings due to this.

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