Tropics

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World map with the intertropical zone highlighted in crimson World map indicating tropics and subtropics.png
World map with the intertropical zone highlighted in crimson
Areas of the world with tropical climates Koppen-Geiger Map A present.svg
Areas of the world with tropical climates

The tropics are the region of Earth surrounding the Equator. They are delimited in latitude by the Tropic of Cancer in the Northern Hemisphere at 23°26′11.6″ (or 23.43655°) N and the Tropic of Capricorn in the Southern Hemisphere at 23°26′11.6″ (or 23.43655°) S; these latitudes correspond to the axial tilt of the Earth. The tropics are also referred to as the tropical zone and the torrid zone (see geographical zone). The tropics include all zones on Earth where the Sun contacts a point directly overhead at least once during the solar year (which is a subsolar point). Thus the maximum latitudes of the tropics have the same value positive and negative. Likewise, they approximate, due to the earth not being a perfect sphere, the "angle" of the Earth's axial tilt. The "angle" itself is not perfectly fixed due chiefly to the influence of the moon, but the limits of tropics are a geographic convention, being an averaged form, not least the variance is very small.

Contents

In terms of climate, the tropics receive sunlight that is more direct than the rest of Earth and are generally hotter and wetter. The word "tropical" sometimes refers to this sort of climate rather than to the geographical zone. The tropical zone includes deserts and snow-capped mountains, which are not tropical in the climatic sense. The tropics are distinguished from the other climatic and biomatic regions of Earth, which are the middle latitudes and the polar regions on either side of the equatorial zone.

The tropics constitute 40% of Earth's surface area [1] and contain 36% of Earth's landmass. [2] As of 2014, the region was home to 40% of the world's population, and this figure was then projected to reach 50% by 2050. [3]

Etymology

The word "tropic" comes from Ancient Greek τροπή (tropē), meaning "to turn" or "change direction"

Seasons and climate

A graph showing the zonally averaged monthly precipitation. The tropics receive more precipitation than higher latitudes. The precipitation maximum, which follows the solar equator through the year, is under the rising branch of the Hadley circulation; the sub-tropical minima are under the descending branch and cause the desert areas. Monthly zonal mean precipitation.png
A graph showing the zonally averaged monthly precipitation. The tropics receive more precipitation than higher latitudes. The precipitation maximum, which follows the solar equator through the year, is under the rising branch of the Hadley circulation; the sub-tropical minima are under the descending branch and cause the desert areas.
Aerial view of Bora Bora, French Polynesia Bora Bora.jpg
Aerial view of Bora Bora, French Polynesia
Tropical sunset over the sea in Kota Kinabalu, Malaysia Kota Kinabalu by Dale Preston.jpg
Tropical sunset over the sea in Kota Kinabalu, Malaysia

"Tropical" is sometimes used in a general sense for a tropical climate to mean warm to hot and moist year-round, often with the sense of lush vegetation.

Many tropical areas have a dry and wet season. The wet season, rainy season or green season is the time of year, ranging from one or more months, when most of the average annual rainfall in a region falls. [4] Areas with wet seasons are disseminated across portions of the tropics and subtropics. [5] Under the Köppen climate classification, for tropical climates, a wet-season month is defined as a month where average precipitation is 60 millimetres (2.4 in) or more. [6] Tropical rainforests technically do not have dry or wet seasons, since their rainfall is equally distributed through the year. [7] Some areas with pronounced rainy seasons see a break in rainfall during mid-season when the intertropical convergence zone or monsoon trough moves poleward of their location during the middle of the warm season; [8] typical vegetation in these areas ranges from moist seasonal tropical forests to savannahs.

When the wet season occurs during the warm season, or summer, precipitation falls mainly during the late afternoon and early evening hours. The wet season is a time when air quality improves, freshwater quality improves and vegetation grows significantly, leading to crop yields late in the season. Floods cause rivers to overflow their banks, and some animals to retreat to higher ground. Soil nutrients diminish and erosion increases. The incidence of malaria increases in areas where the rainy season coincides with high temperatures. Animals have adaptation and survival strategies for the wetter regime. The previous dry season leads to food shortages into the wet season, as the crops have yet to mature.

However, regions within the tropics may well not have a tropical climate. Under the Köppen climate classification, much of the area within the geographical tropics is classed not as "tropical" but as "dry" (arid or semi-arid), including the Sahara Desert, the Atacama Desert and Australian Outback. Also, there are alpine tundra and snow-capped peaks, including Mauna Kea, Mount Kilimanjaro, and the Andes as far south as the northernmost parts of Chile and Perú.

Ecosystems

Coconut palms in the warm, tropical climate of northern Brazil Pajucara.jpg
Coconut palms in the warm, tropical climate of northern Brazil
Tropical forest near Fonds-Saint-Denis, Martinique Tropical forest.JPG
Tropical forest near Fonds-Saint-Denis, Martinique

Tropical plants and animals are those species native to the tropics. Tropical ecosystems may consist of tropical rainforests, seasonal tropical forests, dry (often deciduous) forests, spiny forests, desert and other habitat types. There are often significant areas of biodiversity, and species endemism present, particularly in rainforests and seasonal forests. Some examples of important biodiversity and high endemism ecosystems are El Yunque National Forest in Puerto Rico, Costa Rican and Nicaraguan rainforests, Amazon Rainforest territories of several South American countries, Madagascar dry deciduous forests, the Waterberg Biosphere of South Africa, and eastern Madagascar rainforests. Often the soils of tropical forests are low in nutrient content, making them quite vulnerable to slash-and-burn deforestation techniques, which are sometimes an element of shifting cultivation agricultural systems.

In biogeography, the tropics are divided into Paleotropics (Africa, Asia and Australia) and Neotropics (Caribbean, Central America, and South America). Together, they are sometimes referred to as the Pantropic. The system of biogeographic realms differs somewhat; the Neotropical realm includes both the Neotropics and temperate South America, and the Paleotropics correspond to the Afrotropical, Indomalayan, Oceanian, and tropical Australasian realms.

Tropicality

Tropicality refers to the image that people outside the tropics have of the region, ranging from critical to verging on fetishism. The idea of tropicality gained renewed interest in geographical discourse when French geographer Pierre Gourou published Les Pays Tropicaux (The Tropical World in English), in the late 1940s. [9]

Tropicality encompassed two images. One, is that the tropics represent a 'Garden of Eden', a heaven on Earth, a land of rich biodiversity - aka a tropical paradise. [10] The alternative is that the tropics consist of wild, unconquerable nature. The latter view was often discussed in old Western literature more so than the first. [10] Evidence suggests over time that the view of the tropics as such in popular literature has been supplanted by more well-rounded and sophisticated interpretations. [11]

Western scholars tried to theorise reasons about why tropical areas were relatively more inhospitable to human civilisations then those existing in colder regions of the Northern Hemisphere. A popular explanation focused on the differences in climate. Tropical jungles and rainforests have much more humid and hotter weather than colder and drier temperaments of the Northern Hemisphere. This theme led to some scholars to suggest that humid hot climates correlate to human populations lacking control over nature e.g. ' the wild Amazonian rainforests'. [12]

See also

Related Research Articles

Geography of Nigeria

Nigeria is a country in West Africa. Nigeria shares land borders with the Republic of Benin in the west, Chad and Cameroon in the east, and Niger in the north. It also shares a border with the self-declared, but internationally unrecognized state of Ambazonia in the southeast. Its coast lies on the Gulf of Guinea in the south and it borders Lake Chad to the northeast. In the southeast, it also shares a border with the breakaway state of Ambazonia. Noted geographical features in Nigeria include the Adamawa highlands, Mambilla Plateau, Jos Plateau, Obudu Plateau, the Niger River, River Benue and Niger Delta.

Temperate climate Main climate class

In geography, the temperate climates of Earth occur in the middle latitudes, which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ranges throughout the year and more distinct seasonal changes compared to tropical climates, where such variations are often small.

Tropic of Cancer Line of northernmost latitude at which the sun can be directly overhead

The Tropic of Cancer, which is also referred to as the Northern Tropic, is the most northerly circle of latitude on Earth at which the Sun can be directly overhead. This occurs on the June solstice, when the Northern Hemisphere is tilted toward the Sun to its maximum extent. It also reaches 90 degrees below the horizon at solar midnight on the December Solstice. Using a continuously updated formula, the circle is currently 23°26′11.6″ (or 23.43655°) north of the Equator.

Tropic of Capricorn Line of southernmost latitude at which the sun can be directly overhead

The Tropic of Capricorn is the circle of latitude that contains the subsolar point at the December solstice. It is thus the southernmost latitude where the Sun can be seen directly overhead. It also reaches 90 degrees below the horizon at solar midnight on the June Solstice. Its northern equivalent is the Tropic of Cancer.

Subtropics Geographic and climate zone

The subtropics are geographic and climate zones located roughly bordered the tropics at latitude 23° 27' and the temperate zones, north and south of the Equator.

Tropical climate Climate in the tropical region

Tropical climate is one of the five major climate groups in the Köppen climate classification. Tropical climates are characterized by monthly average temperatures of 18 ℃ (64.4 ℉) or higher year-round and feature hot temperatures. Annual precipitation is often abundant in tropical climates, and shows a seasonal rhythm to varying degrees. There are normally only two seasons in tropical climates, a wet season and a dry season. The annual temperature range in tropical climates is normally very small. Sunlight is intense.

Köppen climate classification Climate classification system

The Köppen climate classification is one of the most widely used climate classification systems. It was first published by the German-Russian climatologist Wladimir Köppen (1846–1940) in 1884, with several later modifications by Köppen, notably in 1918 and 1936. Later, the climatologist Rudolf Geiger (1894-1981) introduced some changes to the classification system, which is thus sometimes called the Köppen–Geiger climate classification system.

Middle latitudes

The middle latitudes are a spatial region on Earth located between the latitudes 23°26'22" and 66°33'39" north, and 23°26'22" and 66°33'39" south. They include Earth's subtropical and temperate zones, which lie between the tropics and the polar circles. Weather fronts and extratropical cyclones are usually found in this area, as well as occasional tropical cyclones, which have traveled from their areas of formation closer to the Equator.

Dry season Yearly period of low rainfall, especially in the tropics

The dry season is a yearly period of low rainfall, especially in the tropics. The weather in the tropics is dominated by the tropical rain belt, which moves from the northern to the southern tropics and back over the course of the year.

Wet season

The wet season is the time of year when most of a region's average annual rainfall occurs. Generally, the season lasts at least a month. The term green season is also sometimes used as a euphemism by tourist authorities. Areas with wet seasons are dispersed across portions of the tropics and subtropics.

Rainfall and the tropical climate dominate the tropical rain belt, which oscillates from the northern to the southern tropics over the course of the year, roughly following the solar equator. The tropical rain belt is an area of active rain that is positioned mostly around the tropics.

A tropical marine climate is a tropical climate that is primarily influenced by the ocean. It is usually experienced by islands and coastal areas 10° to 20° north and south of the equator. There are two main seasons in a tropical marine climate: the wet season and the dry season. The annual rainfall is 1000 to over 1500 mm. The temperature ranges from 20 °C to 35 °C. The trade winds blow all year round and are moist, as they pass over warm seas. These climatic conditions are found, for example, across the Caribbean; the eastern coasts of Brazil, Madagascar and Queensland; and many islands in tropical waters.

Geographical zone Major regions of Earths surface demarcated by latitude

The five main latitude regions of Earth's surface comprise geographical zones, divided by the major circles of latitude. The differences between them relate to climate. They are as follows:

  1. The North Frigid Zone, between the North Pole at 90° N and the Arctic Circle at 66° 33' N, covers 4.12% of Earth's surface.
  2. The North Temperate Zone, between the Arctic Circle at 66° 33' N and the Tropic of Cancer at 23° 27' N, covers 25.99% of Earth's surface.
  3. The Torrid Zone, between the Tropic of Cancer at 23° 27' N and the Tropic of Capricorn at 23° 27' S, covers 39.78% of Earth's surface.
  4. The South Temperate Zone, between the Tropic of Capricorn at 23° 27' S and the Antarctic Circle at 66° 33' S, covers 25.99% of Earth's surface.
  5. The South Frigid Zone, from the Antarctic Circle at 66° 33' S and the South Pole at 90° S, covers 4.12% of Earth's surface.
Paleotropical Kingdom

The Paleotropical Kingdom (Paleotropis) is a floristic kingdom comprising tropical areas of Africa, Asia and Oceania, as proposed by Ronald Good and Armen Takhtajan. Part of its flora, inherited from the ancient supercontinent of Gondwana or exchanged later, is shared with the Neotropical Kingdom, comprising tropical areas of Central and South America. Moreover, the Paleotropical flora influenced the tropical flora of the Australian Kingdom. The Paleotropical Kingdom is subdivided into five floristic subkingdoms according to Takhtajan and about 13 floristic regions. In this article the floristic subkingdoms and regions are given as delineated by Takhtajan.

Tropical savanna climate Climate subtype

Tropical savanna climate or tropical wet and dry climate is a type of climate that corresponds to the Köppen climate classification categories Aw and As. The driest month has less than 60 mm (2.4 in) of precipitation and also less than of precipitation.

Tropical rainforest climate Type of tropical climate in which there is no dry season

A tropical rainforest climate or equatorial climate is a tropical climate usually found within 10 to 15 degrees latitude of the equator, and has at least 60 millimetres (2.4 in) of rainfall every month of the year. Regions with this climate are typically designated Af by the Köppen climate classification. A tropical rainforest climate is typically hot, very humid, and wet.

Climate of Africa Climate of the continent

The climate of Africa is a range of climates such as the equatorial climate, the tropical wet and dry climate, the tropical monsoon climate, the semi-arid climate, the desert climate, and the subtropical highland climate. Temperate climates are rare across the continent except at very high elevations and along the fringes. In fact, the climate of Africa is more variable by rainfall amount than by temperatures, which are consistently high. African deserts are the sunniest and the driest parts of the continent, owing to the prevailing presence of the subtropical ridge with subsiding, hot, dry air masses. Africa holds many heat-related records: the continent has the hottest extended region year-round, the areas with the hottest summer climate, the highest sunshine duration, and more.

Tropical vegetation Vegetation in tropical latitudes

Tropical vegetation is any vegetation in tropical latitudes. Plant life that occurs in climates that are warm year-round is in general more biologically diverse that in other latitudes. Some tropical areas may receive abundant rain the whole year round, but others have long dry seasons which last several months and may vary in length and intensity with geographic location. These seasonal droughts have great impact on the vegetation, such as in the Madagascar spiny forests. Rainforest vegetation is categorized by five layers. The top layer being the upper tree layer. Here you will find the largest and widest trees in all the forest. These trees tend to have very large canopy's so they can be fully exposed to sunlight. A layer below that is the middle tree layer. Here you will find more compact trees and vegetation. These trees tend to be more skinny as they are trying to gain any sunlight they can. The third layer is the lower tree area. These trees tend to be around five to ten meters high and tightly compacted. The trees found in the third layer are young trees trying to grow into the larger canopy trees. The fourth layer is the shrub layer beneath the tree canopy. This layer is mainly populated by sapling trees, shrubs, and seedlings. The fifth and final layer is the herb layer which is the forest floor. The forest floor is mainly bare except for various plants, mosses, and ferns. The forest floor is much more dense than above because of little sunlight and air movement.

Vegetation classification is the process of classifying and mapping the vegetation over an area of the earth's surface. Vegetation classification is often performed by state based agencies as part of land use, resource and environmental management. Many different methods of vegetation classification have been used. In general, there has been a shift from structural classification used by forestry for the mapping of timber resources, to floristic community mapping for biodiversity management. Whereas older forestry-based schemes considered factors such as height, species and density of the woody canopy, floristic community mapping shifts the emphasis onto ecological factors such as climate, soil type and floristic associations. Classification mapping is usually now done using geographic information systems (GIS) software.

Seasonal tropical forest

Seasonal tropical forest, also known as moist deciduous, semi-evergreen seasonal, tropical mixed or monsoon forests, typically contain a range of tree species: only some of which drop some or all of their leaves during the dry season. This tropical forest is classified under the Walter system as (ii) tropical climate with high overall rainfall concentrated in the summer wet season and dry season: representing a range of habitats influenced by monsoon (Am) or tropical wet savannah (Aw) climates. Drier forests in the Aw climate zone are typically deciduous and placed in the Tropical dry forest biome: with further transitional zones (ecotones) of savannah woodland then tropical and subtropical grasslands, savannas, and shrublands.

References

  1. "How much land is in the tropics?". God Plays Dice. 2007-12-04. Retrieved 2017-06-26.
  2. "tropics". National Geographic Encyclopedia. National Geographic Society. Retrieved 2017-06-26.
  3. "Expanding tropics will play greater global role, report predicts". Science Magazine. 29 June 2014.
  4. Glossary of Meteorology (2009). Rainy season. Archived 2009-02-15 at the Wayback Machine American Meteorological Society. Retrieved on 2008-12-27.
  5. Michael Pidwirny (2008). CHAPTER 9: Introduction to the Biosphere. PhysicalGeography.net. Retrieved on 2008-12-27.
  6. "Updated world Koppen-Geiger climate classification map" (PDF).
  7. Elisabeth M. Benders-Hyde (2003). World Climates. Blue Planet Biomes. Retrieved on 2008-12-27.
  8. J . S. 0guntoyinbo and F. 0. Akintola (1983). Rainstorm characteristics affecting water availability for agriculture. Archived 2009-02-05 at the Wayback Machine IAHS Publication Number 140. Retrieved on 2008-12-27
  9. Arnold, David. "Illusory Riches: Representations of the Tropical World, 1840-1950", p. 6. Journal of Tropical Geography
  10. 1 2 Arnold, David. "Illusory Riches: Representations of the Tropical World, 1840-1950", p. 7. Journal of Tropical Geography
  11. Menadue, Christopher B. (2017-05-30). "Trysts Tropiques: The Torrid Jungles of Science Fiction" (PDF). ETropic: Electronic Journal of Studies in the Tropics. 16 (1). doi:10.25120/etropic.16.1.2017.3570. ISSN   1448-2940.
  12. Arnold, David. "Illusory Riches: Representations of the Tropical World, 1840-1950", p. 13. Journal of Tropical Geography