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January temperature

from 978-3-14-100790-9 from page 156 fig. 1
Diercke Karte January temperature
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January temperature
The African continent stretches over two climate zones: the tropics close to the Equator and the subtropics on either side of the tropical zone. Due to the relatively high position of the sun throughout the year, and resulting high input of energy, there is no actual thermal winter here. Even in the mountains, at high altitudes, the average monthly temperature does not fall below zero degrees in winter. On the lowlands, the temperature remains 10° either side of the tropics and over 25° at the Equator.

Reasons for temperature distribution
The temperature distribution in Africa is influenced by three main factors – solar radiation, cloud cover and evaporation, which in turn are influenced by precipitation levels. Theoretically the equatorial latitudes experience the greatest input of energy due to the sun's high position throughout the year, its inclination at the Equator never being less than 66.5° during the midday hours. However, due to heavy cloud cover in the Innertropical Convergence Zone (ITCZ), which is the confluence zone of the trade winds, part of the incoming solar radiation is reflected. Consequently, the earth's surface temperature does not increase significantly. High equatorial precipitation also leads to increased evaporation. As a result of this energy expenditure, further radiation energy is converted into latent heat and not sensible heat.
For this reason, the highest temperatures in Africa do not occur near the Equator, but around the Tropics of Cancer and Capricorn. Downward air movement in the subtropical belt of high pressure causes cloud dissipation, resulting in extreme arid regions. Solar insolation remains largely unobstructed due to the zenith of the sun in summer, which has a correspondingly strong, warming effect.
Both the low level of ground moisture and near absence of vegetation, often responsible for evaporation in the equatorial latitudes (due to transpiration), results in low levels of evaporation. Therefore, a large amount of incoming solar energy can be converted into sensible heat. The daytime temperature in the Sahara can reach over 50 °C. At night and during winter, high radiation and related cooling can occur.

Daily and annual variations
Throughout the year, the relatively consistent energy input results in an average tropical daytime climate near the equator. The seasonal differences in temperature are markedly lower than between day and night. For this reason, the temperature in tropical Africa between January and July varies only slightly, by one temperature level at most. The greater the distance from the equator, the greater is the difference in seasonal radiation and temperature. This becomes particularly apparent in the subtropics where the average monthly temperature in this region can be as high as 20 °C.
In the northern summer (July), significant warming in the tropical and subtropical arid regions is apparent due to the zenith of the sun, the resulting high input of energy and the near absence of cloud cover. The temperature rises above 35 °C in the middle of the month.
A. Siegmund, P. Frankenberg, D. Volz; Ü: J. Moar, C. Fleming


Keywords: Africa climate innertropical convergence zone (ITCZ) isotherms temperature

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