The tropics (from ancient Greek τρόποι Ἥλιου trópoi Hēliou , German 'solstice areas' ) are according to a common definition the area between the tropics , i.e. between 23.5 ° north and south latitude. There are also other definitions that are based, for example, on air pressure or annual mean temperatures.
In the inner tropics near the equator , there is usually an always humid tropical climate. The average annual precipitation is 2000 mm, whereby the highest amounts of rain coincide with the times of the highest sun positions ( zenith rain ). There are no distinct dry seasons. In the outer tropics , on the other hand, there is a wintry dry season with less rainfall overall, which is most pronounced in the peripheral tropics on the border with the subtropical climatic zone .
According to an earlier, still common, division of the earth into physical climatic zones , the tropics are the hottest climatic zone on earth with average temperatures of 25 to 27 ° C. Depending on how humid the respective tropical area is, it can be divided into five vegetation zones, the from tropical rainforest to desert .
Location and demarcation
The tropics are:
- In terms of radiation climate, the areas that are delimited by the two tropics (23 ° 27 ′ north and south latitude ) and in which the sun is at the zenith at least once a year ( low latitudes in the geomathematical sense - the term is transferred analogously to the Planetology used for other celestial bodies ),
- in the system of atmospheric circulation, the area between the two subtropical-marginal tropical high pressure belts of the northern and southern hemispheres of the earth,
- the area on both sides of the equator , which is characterized by higher daily and lower seasonal temperature fluctuations ( daily climate with an annual average of 25 ° C), since thermal seasons cannot form due to the year-round high irradiation,
- the area in which the annual day lengths fluctuate only slightly between 10.5 and 13.5 hours.
As the polar boundary between the tropics and the subtropics, Köppen used the 18 ° C isotherm , Supan and Philippson the 20 ° C isotherm of the coldest month. However, these delimitations only relate to the warm tropics located at a low altitude above sea level , but the typical climatic properties of the tropics also apply to the higher areas. Because the temperature decreases with altitude , if the temperature falls below the 18 or 20 ° C isotherm, but a higher value would be calculated, it is called cold tropics .
When outside or Ektropen those areas are called, are not in the tropics.
Vegetation zones of the tropics
- 12 to 9½ humid months = tropical rainforest ,
- 9½ to 7 humid months = moist savannah ,
- 7 to 4½ humid months = dry savannah ,
- 4½ to 2 humid months = thorn bush savannah
- 2 to 0 humid months = desert .
Within the tropics, a distinction is made between the always humid tropics close to the equator and the alternately humid or dry tropics towards the tropics , which appear in different eco-zones from the tropical forests to the various types of savanna to the tropical semi-deserts and deserts.
In the always humid tropics, which, with the exception of East Africa and the Andes, are located everywhere on the equator, tropical rainforests are formed. Typical of the humid tropics, in which dry and rainy seasons form the seasons, are savannas , dry forests and monsoon forests that line the tropical rainforests, but the wetland of the Pantanal in South America is also located in this zone. The dry tropics are desert and semi-desert areas that have a constant temperature throughout the year.
The land use in the tropics is very different depending on the prevailing vegetation zone. Since the largest population growth on earth is observed in the tropical regions, it plays an important role.
The tropics as topos
The tropics are more than a climatic category, they are also a cultural destination. Modern artists have been interpreting the tropics for more than 100 years. The coconut palm is a symbol.
Weather and climate
The weather at the equator is mainly characterized by the intertropical convergence zone. Regular phenomena are the summer and winter monsoons . The trade winds are also characteristic . As extreme weather events, intense showers and thunderstorms as well as tropical cyclones can occur.
- Wilhelm Lauer : On the essence of the tropics. Climate-ecological studies on the content and delimitation of an earthly landscape belt (= Academy of Sciences and Literature - Treatises of the Mathematical and Natural Science Class. 1975, No. 3). Academy of Sciences and Literature, Mainz a. a. 1975, ISBN 3-515-02091-8 .
- cf. like dust desert Mars. Astrowetter.com.
- Reinhard Maack: Notas preliminares sôbre Clima, Solos e Vegetação do Estado do Paraná . In: Conselho Nacional de Geografia, Instituto Brasileiro de Geografia (ed.): Boletim geográfico . Ano VII, no. 84 , March 1950, p. 1406 ( gov.br ): "Mas A. Supan [...] e A. Philippson [...] limitam os trópicos pela isoterma mensal dos 20 ° C e W. Koeppen [...] pela isoterma de 18 ° C do mês mais frio. "
- Martin Meggle: Die Tropendämmerung (2008). Essay on the website of the Goethe-Institut .
- “The Tropics” - successful exhibition in Cape Town ( Memento from February 17, 2013 in the web archive archive.today ). Media information March 2009, Goethe-Institut.
- Bernhard Berking, Werner Huth: Handbook Nautics - Navigatorische Schiffsführung. 1st edition. Seehafen Verlag, 2010, pp. 277–280.