Distribution of climate elements in east Africa.
The climate elements in east Africa are precipitation, Temperature, Humidity, Sunshine, Cloud cover, Winds and Atmospheric pressure. Ideally East Africa lies within the equatorial climate region, extending between 5° North and 6° South of the equator. However, she does not enjoy a true equatorial climate. East Africa’s climate is modified by relief, the effect of Lake Victoria and the continentality of some of her regions. As a result, she enjoys a tropical climate which is hot and humid at the coast, temperate inland and very dry in her north and north-eastern parts.
There is plenty of sunshine all year. However, it is usually cool at night and early in the morning. There are two rainy seasons. The long rains occur between October to December following the passing of ITCZ. Rainfall is often heavy and usually falls in the afternoons and evenings. The hottest period is between February and March and the coldest between July and august. Prevailing winds are the South east and North-East trade winds.
The distribution of climatic elements in east Africa are bets understood on the basis of the demarcation of her climatic regions. Seven climatic regions can be identified within east Africa. These are the modified equatorial climate of the coast and lake basin, modified tropical climate of the highlands, Tropical continental climate, Tropical climate of Narok, Southern Taita and Kwale, Tropical Northern climate, True desert climate, Micro (urban climates and Mountain) climates.
Modified equatorial climate:
This is a type of equatorial climate which is modified by high altitude and the presence of water bodies so that it has lower temperature and lower rainfall totals compared to the true equatorial climate.
It occurs in the highland areas of east Africa where temperatures and rainfall modified by altitude. It also occurs around water bodies which have a modifying effect on both temperature and rainfall. These areas are the east African highlands including Mt. Kenya, Mt Elgon, Mt. Kilimanjaro, the Arber dares, Ruwenzoris, the lake Victoria basin and Coastal east Africa along the Indian Ocean.
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In the highlands, temperatures are much lower than those of the true equatorial climate. Mean daily temperature can be as low as 15°C. Temperature decreases with increase in altitude. Around water bodies temperatures are also lower than those of the true equatorial climate due to the moderating influence of the lakes and sea. For example Kisumu has a mean annual temperature of 23°C and a mean annual temperature range of 2°C v mean annual temperature range of 3°C-5°C
There is high rainfall of 1000mm-1500mm which is evenly distributed throughout the year. There is a double –maxima rainfall regime. Rainfall is both relief and convectional. Relief rainfall occurs around highland regions while convectional rainfall occurs in lowlands around water bodies. The coastal region has high rainfall although it is lower than that of the true equatorial climate and varies according to location. Areas which lie in the paths of trade winds receive higher rainfall than those whose location is away from the path of the winds. The Rainfall is well distributed rainfall all year. Rainfall varies with location, for example Mombasa receives 1100 mm of rainfall annually as she lies in the path of onshore south-east and North-east trade winds Lamu on the other hand receives 930 mm of rainfall because her coast is quite regular.
There is high relative humidity all year due to high evaporation rates from the ocean. Prevailing winds are onshore south-east and North-east trades. Local winds occur in form of land and sea breezes which modify daytime and nighttime temperatures considerably.
Along the Lake Victoria basin, Location the climate covers Nyanza and Western counties in Kenya, the northwestern parts of Tanzania and the south-eastern parts of Uganda. Mean annual temperatures range between 22° C and 32°C.Temperatures are much lower than those of the true equatorial climate due to the moderating influence of the lake and varied relief in the region. For example Kisumu has a mean annual temperature of 25°C and a very small annual temperature of about 2°C.
There is no real dry season. Rainfall ranges between 750 mm and 1500 mm and varies from location to location. For example Kisumu receives 1300 mm of mean annual rainfall Winam gulf to the south has two rainfall seasons separated by a distinct dry seasons separated by a distinct dry season. The rainfall ranges between 570mm and 875 mm annually. Rainfall is mainly convectional but relief rainfall occurs around high grounds. Humidity- High relative humidity due to the constant high temperature and presence of Lake Victoria where high rates of evaporation occurs. Local winds are land and lake breezes
Modified Tropical climate of the highlands:
This climate is also called the subtropical climate of the highlands. Location- It is found in the highlands east and west of the rift valley in the three countries and around the very high mountains including Kilimanjaro, Elgon and Kenya. It is a modified version of the tropical continental climate. It is modified by relief, altitude and aspect. At high altitude, mean annual temperatures are 10°C or lower for example Nairobi has a mean annual temperature of 20°C.
It has a small mean annual temperature range of between 3° c and 5°C. For example the mean annual temperature range for Nairobi is 4°C. Lower slopes have higher temperature due to the effect of altitude on temperature. For example the coolest months are between June and August. High rainfall that is well –distributed all year. Rainfall totals range between 1000 mm and 1500mm annually, although mountain regions receive higher rainfall amounts of over 2000 mm annually. Rainfall varies according to aspect and the effect of rain bearing winds windward slopes receive higher rainfall, for example Meru on the North-eastern slopes of Mount Kenya receives 1258 mm of rainfall annually. Leeward slopes receive low rainfall, for example Nyeri on the South –western slopes of Mount Kenya receives 719 mm of rainfall annually. There is a double maxima rainfall regime in the highlands to the east of the rift valley, which occurs between March and May, and also in October. There is a single maxima rainfall regime in the highlands west of the rift valley which occurs in May- August. Rainfall is mainly orographic. Mountain and valley winds occur around mountain regions. Relative humidity is moderate all year
The Tropical climate of Narok, Southern Taita, Kwale and northern Tanzania.
The climate has high temperatures similar to the tropical continental climate except in areas of high relief where temperature is modified by high altitude. For example Loita hills and Shimba hills. Rainfall is orographic. It varies with altitude for example Narok at 1890 m altitude receives 672 mm of rainfall annually. Rainfall occurs between November and may and falls in one season
Tropical Continental Climate
This climate is also called Semi-desert climate. t is found in Northern-eastern Kenya , most of eastern Kenya and a larger part of northern Kenya, central and southern Tanzania and north western Uganda.. It has High temperatures ranging between 22°C and 27°C all year and small mean annual temperature range of 5°C. Temperatures are slightly lower at high altitude for example Vol which experiences mean annual temperatures of 25°C while Garissa at lower altitude experiences mean annual temperatures of 28.5°C. There is low unreliable rainfall. The mean annual rainfall is 500 mm.
Areas of high relief receive slightly higher rainfall amounts for example Voi has 556 mm annual rainfall. Lowlands receive lower rainfall for example Garissa receives 35omm while Magadi receives 409 mm annually.
The Tropical Northern Climate:
This climate covers a small area of the northern western part of Kenya and north eastern Uganda. This is the region around Karasuk. It has high temperatures all year, although the temperature is slightly modified by altitude. Rainfall is mainly convection. Rainfall occurs between June and September. There is a long dry season that lasts about six months. Mean annual rainfall is 850 mm
Desert Climate of Central Northern Kenya:
. The climate is found in central Northern Kenya around Wajir and Lodwar. There are high temperatures with annual averages of 28°C- 29°C on the low plains, high daytime temperatures of up to 35°C, low night time temperatures of 20°C or lower, low rainfall usually less than 250 mm annually . It usually falls when the south east and Northern east trades converge over the region with the passing of the ITCZ, Cloudless skies which result into intense insolation in the day time an high terrestrial radiation at night, and Low relative humidity due to low rainfall and absence of ground moisture. Prevailing winds are the south east and north east trade winds which converge within the ITCZ as it passes over the region. There are frequent Sandstorms Descending or diverging North –east trade winds originate from the North-eastern Africa and Arabia and do not bring rain.Within this climate there are regions of true desert climate. These are The Chalbi desert and The Karoli desert which lie between Marsabit and Lake Turkana and The Kaisuit desert South of the Chalbi desert.Marsabit and its environs enjoy a micro- climate due to the effect of altitude and aspect on temperature and rainfall respectively. Temperatures are lower and rainfall is higher.
Micro-Climates:
Micro-climate are also called local climate. They are climates experienced within a small, localized area and which are slightly modified in comparison to the general climate of the surrounding region. They occur in urban areas, Industrial regions, around water bodies and In forested regions. They occur when the climate element of temperature and precipitation are modified. They are found in east Africa’s urban cities, forests and around water bodies such as dams and lakes. Industrial smoke contributes to the formation of smog. Smog causes a rise in temperatures by forming a blanket-like layer overhead which traps terrestrial radiation. Increased amounts of carbon dioxide and chlorofluorocarbons emitted into the atmosphere by factories and vehicles deplete the ozone layer. This leads to arise in atmospheric temperatures. Water bodies and forested areas cause increased evapo-transpiration. This leads to increased precipitation in an area. Trees cause a cooling effect by providing shade, thus blocking insolation from reaching the ground. Trees break the velocity of winds so that an area experiences mild winds. Forested areas and areas around man-made lakes have high humidity due to increased evapo-transpiration. Uncontrolled deforestation leads to reduced rainfall and a rise in temperatures and may result in aridity in and area.
Lauri answered the question on March 18, 2018 at 16:43