The tropics are the regions of Earth surrounding the equator, where the sun may shine directly overhead. This contrasts with the temperate or polar regions of Earth, where the Sun can never be directly overhead. This is because of Earth's axial tilt; the width of the tropics (in latitude) is twice the tilt. The tropics are also referred to as the tropical zone and the torrid zone (see geographical zone).
Due to the overhead sun, the tropics receive the most solar energy over the course of the year, and consequently have the highest temperatures on the planet. Even when not directly overhead, the sun is still close to overhead throughout the year, therefore the tropics also have the lowest seasonal variation on the planet; "winter" and "summer" lose their contrast. Instead, seasons are more commonly divided by precipitation variations than by temperature variations.
The tropics maintain wide diversity of local climates, such as rain forests, monsoons, savannahs, deserts, and high altitude snow-capped mountains. The word "tropical" can specifically refer to certain kinds of weather, rather than to the geographic region; these usages ought not be confused.
The Earth's axial tilt is currently around 23.4°, and therefore so are the latitudes of the tropical circles, marking the boundary of the tropics: specifically, ±23°26′09.6″ (or 23.43601°). The northern one is called the Tropic of Cancer, and the southern is the Tropic of Capricorn. As the Earth's axial tilt changes, so too do the tropical and polar circles.
The tropics constitute 39.8% of Earth's surface area and contain 36% of Earth's landmass. As of 2014[update], the region was home also to 40% of the world's population, and this figure was then projected to reach 50% by 2050. Because of global warming, the weather conditions of the tropics are expanding with areas in the subtropics, having more extreme weather events such as heatwaves and more intense storms. These changes in weather conditions may make certain parts of the tropics uninhabitable.
Etymology
The word "tropic" comes via Latin from Ancient Greek τροπή (tropē), meaning "to turn" or "change direction".
Astronomical definition
The tropics are defined as the region between the Tropic of Cancer in the Northern Hemisphere at 23°26′09.6″ (or 23.43601°) N and the Tropic of Capricorn in the Southern Hemisphere at 23°26′09.6″ (or 23.43601°) S; these latitudes correspond to the axial tilt of the Earth.
The Tropic of Cancer is the Northernmost latitude from which the Sun can ever be seen directly overhead, and the Tropic of Capricorn is the Southernmost. This means that the tropical zone includes everywhere on Earth which is a subsolar point at least once during the solar year. Thus the maximum latitudes of the tropics have equal distances from the equator on either side. Likewise, they approximate the angle of the Earth's axial tilt. This angle is not perfectly fixed, mainly due to the influence of the moon, but the limits of the tropics are a geographic convention, and their variance from the true latitudes is very small.
Seasons and climate
Many tropical areas have both a dry and a 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. Areas with wet seasons are disseminated across portions of the tropics and subtropics, some even in temperate regions. Under the Köppen climate classification, for tropical climates, a wet-season month is defined as one or more months where average precipitation is 60 mm (2.4 in) or more. 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; 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 due to the wet season supplementing flora, leading to crop yields late in the season. Floods and rains cause rivers to overflow their banks, and some animals to retreat to higher ground. Soil nutrients are washed away 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, Puncak Jaya and the Andes as far south as the northernmost parts of Chile and Peru.
Climate change
The climate is changing in the tropics, as it is in the rest of the world. The effects of steadily rising concentrations of greenhouse gases on the climate may be less obvious to tropical residents, however, because they are overlain by considerable natural variability. Much of this variability is driven by the El Niño-Southern Oscillation (ENSO). The Tropics has warmed by 0.7–0.8 °C over the last century—only slightly less than the global average—but a strong El Niño made 1998 the warmest year in most areas, with no significant warming since. Climate models predict a further 1–2 °C warming by 2050 and 1–4 °C by 2100.
Ecosystems
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, deserts, savannahs, grasslands and other habitat types. There are often wide 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.
Flora
Flora are plants found in a specific region at a specific time. Some well-known plants that are exclusively found in, originate from, or are often associated with the tropics include:
- Bamboo
- Banana trees
- Citrus fruits such as oranges, lemons, mandarins, etc.
- Coconut trees
- Coffee
- Dragon fruit
- Ferns
- Jackfruit
- Orchids
- Palm trees
- Papaya trees
- Rubber tree
- Stone fruits such as mangos, avocado, sapote etc.
- Bird of paradise flower
- Cacao
- Giant water lily
Tropicality
Tropicality refers to the image of the tropics that people from outside the tropics have of the region, ranging from critical to verging on fetishism. 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.
Tropicality encompassed two major images. One, is that the tropics represent a 'Garden of Eden', a heaven on Earth, a land of rich biodiversity or a tropical paradise. 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. 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.
Western scholars tried to theorise why tropical areas were relatively more inhospitable to human civilisations than 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, giving to a more diverse biosphere. This theme led some scholars to suggest that humid hot climates correlate to human populations lacking control over nature e.g. 'the wild Amazonian rainforests'.
See also
- Hardiness zone
- Lahaina Noon
- Tropical ecology
- Tropical marine climate
- Tropical year
- Polar circle
Notes
- Currently −0.013° per hundred years.
References
- "How much land is in the tropics?". God Plays Dice. 2007-12-04. Retrieved 2017-06-26.
- "tropics". National Geographic Encyclopedia. National Geographic Society. 21 January 2011. Retrieved 2017-06-26.
- Yang, Hu; Lohmann, Gerrit; Lu, Jian; Gowan, Evan J.; Shi, Xiaoxu; Liu, Jiping; Wang, Qiang (2020-08-27). "Tropical Expansion Driven by Poleward Advancing Midlatitude Meridional Temperature Gradients". Journal of Geophysical Research: Atmospheres. 125 (16). Bibcode:2020JGRD..12533158Y. doi:10.1029/2020JD033158. ISSN 2169-897X. S2CID 225274572.
- Zeng, Xubin; Reeves Eyre, J. E. Jack; Dixon, Ross D.; Arevalo, Jorge (2021-05-28). "Quantifying the Occurrence of Record Hot Years Through Normalized Warming Trends". Geophysical Research Letters. 48 (10). Bibcode:2021GeoRL..4891626Z. doi:10.1029/2020GL091626. ISSN 0094-8276. OSTI 1798413. S2CID 236399809.
- "We Have a Chance to Keep the Tropics Habitable". Gizmodo. 2021-03-08. Retrieved 2022-11-10.
- "tropic". Oxford learner's dictionaries.
- "What is the significance of the Tropic of Cancer, Tropic of Capricorn, Arctic Circle and Antarctic Circle?". Ask an Astronomer. Retrieved 19 November 2022.
- "Tropical zone". meteoblue. Retrieved 19 November 2022.
- Glossary of Meteorology (2009). Rainy season. Archived 2009-02-15 at the Wayback Machine American Meteorological Society. Retrieved on 2008-12-27.
- Michael Pidwirny (2008). CHAPTER 9: Introduction to the Biosphere. PhysicalGeography.net. Retrieved on 2008-12-27.
- "Updated world Koppen-Geiger climate classification map" (PDF). Archived from the original (PDF) on 2007-10-24.
- 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
- Intergovernmental Panel on Climate Change, ed. (2014-03-24). Climate Change 2013 – The Physical Science Basis. doi:10.1017/cbo9781107415324. ISBN 978-1-107-05799-9.
- "TROPICALITY | Meaning & Definition for UK English | Lexico.com". Lexico Dictionaries | English. Archived from the original on March 25, 2022. Retrieved 2022-03-25.
- Arnold, David. "Illusory Riches: Representations of the Tropical World, 1840-1950", p. 6. Journal of Tropical Geography
- Arnold, David. "Illusory Riches: Representations of the Tropical World, 1840-1950", p. 7. Journal of Tropical Geography
- 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.
- Arnold, David. "Illusory Riches: Representations of the Tropical World, 1840-1950", p. 13. Journal of Tropical Geography
External links
Media related to Tropics at Wikimedia Commons
The tropics are the regions of Earth surrounding the equator where the sun may shine directly overhead This contrasts with the temperate or polar regions of Earth where the Sun can never be directly overhead This is because of Earth s axial tilt the width of the tropics in latitude is twice the tilt The tropics are also referred to as the tropical zone and the torrid zone see geographical zone World map with the intertropical zone highlighted in crimsonAreas of the world with tropical climates Af Am Aw As Due to the overhead sun the tropics receive the most solar energy over the course of the year and consequently have the highest temperatures on the planet Even when not directly overhead the sun is still close to overhead throughout the year therefore the tropics also have the lowest seasonal variation on the planet winter and summer lose their contrast Instead seasons are more commonly divided by precipitation variations than by temperature variations The tropics maintain wide diversity of local climates such as rain forests monsoons savannahs deserts and high altitude snow capped mountains The word tropical can specifically refer to certain kinds of weather rather than to the geographic region these usages ought not be confused The Earth s axial tilt is currently around 23 4 and therefore so are the latitudes of the tropical circles marking the boundary of the tropics specifically 23 26 09 6 or 23 43601 The northern one is called the Tropic of Cancer and the southern is the Tropic of Capricorn As the Earth s axial tilt changes so too do the tropical and polar circles The tropics constitute 39 8 of Earth s surface area and contain 36 of Earth s landmass As of 2014 update the region was home also to 40 of the world s population and this figure was then projected to reach 50 by 2050 Because of global warming the weather conditions of the tropics are expanding with areas in the subtropics having more extreme weather events such as heatwaves and more intense storms These changes in weather conditions may make certain parts of the tropics uninhabitable EtymologyThe word tropic comes via Latin from Ancient Greek troph trope meaning to turn or change direction Astronomical definitionRelationship of Earth s axial tilt e to the tropical and polar circles the Tropic of Cancer is a subsolar point only at the June solstice and the Tropic of Capricorn is only at the December solstice The tropics are defined as the region between the Tropic of Cancer in the Northern Hemisphere at 23 26 09 6 or 23 43601 N and the Tropic of Capricorn in the Southern Hemisphere at 23 26 09 6 or 23 43601 S these latitudes correspond to the axial tilt of the Earth The Tropic of Cancer is the Northernmost latitude from which the Sun can ever be seen directly overhead and the Tropic of Capricorn is the Southernmost This means that the tropical zone includes everywhere on Earth which is a subsolar point at least once during the solar year Thus the maximum latitudes of the tropics have equal distances from the equator on either side Likewise they approximate the angle of the Earth s axial tilt This angle is not perfectly fixed mainly due to the influence of the moon but the limits of the tropics are a geographic convention and their variance from the true latitudes is very small Seasons and climateAerial view of Bora Bora in French PolynesiaTropical sunset over the sea in Kota Kinabalu in Malaysia Many tropical areas have both a dry and a 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 Areas with wet seasons are disseminated across portions of the tropics and subtropics some even in temperate regions Under the Koppen climate classification for tropical climates a wet season month is defined as one or more months where average precipitation is 60 mm 2 4 in or more 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 Typical vegetation in these areas ranges from moist seasonal tropical forests to savannahs 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 formation of desert areas 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 due to the wet season supplementing flora leading to crop yields late in the season Floods and rains cause rivers to overflow their banks and some animals to retreat to higher ground Soil nutrients are washed away 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 Koppen 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 Puncak Jaya and the Andes as far south as the northernmost parts of Chile and Peru Climate change The climate is changing in the tropics as it is in the rest of the world The effects of steadily rising concentrations of greenhouse gases on the climate may be less obvious to tropical residents however because they are overlain by considerable natural variability Much of this variability is driven by the El Nino Southern Oscillation ENSO The Tropics has warmed by 0 7 0 8 C over the last century only slightly less than the global average but a strong El Nino made 1998 the warmest year in most areas with no significant warming since Climate models predict a further 1 2 C warming by 2050 and 1 4 C by 2100 EcosystemsDistribution of tropical wet forests 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 deserts savannahs grasslands and other habitat types There are often wide 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 FloraFlora are plants found in a specific region at a specific time Some well known plants that are exclusively found in originate from or are often associated with the tropics include Bamboo Banana trees Citrus fruits such as oranges lemons mandarins etc Coconut trees Coffee Dragon fruit Ferns Jackfruit Orchids Palm trees Papaya trees Rubber tree Stone fruits such as mangos avocado sapote etc Bird of paradise flower Cacao Giant water lilyCoconut palms in the warm tropical climate of Pajucara in northern Brazil Dragon fruit a tropical fruit from several different cacti originally from the Americas A Giant Water Lily one of which can support up to 32 kilograms of weightTropicalityJurua River surrounded by the dense Amazon rainforest which is home to uncontacted tribes to this day Tropicality refers to the image of the tropics that people from outside the tropics have of the region ranging from critical to verging on fetishism 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 Tropicality encompassed two major images One is that the tropics represent a Garden of Eden a heaven on Earth a land of rich biodiversity or a tropical paradise 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 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 Western scholars tried to theorise why tropical areas were relatively more inhospitable to human civilisations than 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 giving to a more diverse biosphere This theme led some scholars to suggest that humid hot climates correlate to human populations lacking control over nature e g the wild Amazonian rainforests See alsoGeography portalHardiness zone Lahaina Noon Tropical ecology Tropical marine climate Tropical year Polar circleNotesCurrently 0 013 per hundred years References How much land is in the tropics God Plays Dice 2007 12 04 Retrieved 2017 06 26 tropics National Geographic Encyclopedia National Geographic Society 21 January 2011 Retrieved 2017 06 26 Yang Hu Lohmann Gerrit Lu Jian Gowan Evan J Shi Xiaoxu Liu Jiping Wang Qiang 2020 08 27 Tropical Expansion Driven by Poleward Advancing Midlatitude Meridional Temperature Gradients Journal of Geophysical Research Atmospheres 125 16 Bibcode 2020JGRD 12533158Y doi 10 1029 2020JD033158 ISSN 2169 897X S2CID 225274572 Zeng Xubin Reeves Eyre J E Jack Dixon Ross D Arevalo Jorge 2021 05 28 Quantifying the Occurrence of Record Hot Years Through Normalized Warming Trends Geophysical Research Letters 48 10 Bibcode 2021GeoRL 4891626Z doi 10 1029 2020GL091626 ISSN 0094 8276 OSTI 1798413 S2CID 236399809 We Have a Chance to Keep the Tropics Habitable Gizmodo 2021 03 08 Retrieved 2022 11 10 tropic Oxford learner s dictionaries What is the significance of the Tropic of Cancer Tropic of Capricorn Arctic Circle and Antarctic Circle Ask an Astronomer Retrieved 19 November 2022 Tropical zone meteoblue Retrieved 19 November 2022 Glossary of Meteorology 2009 Rainy season Archived 2009 02 15 at the Wayback Machine American Meteorological Society Retrieved on 2008 12 27 Michael Pidwirny 2008 CHAPTER 9 Introduction to the Biosphere PhysicalGeography net Retrieved on 2008 12 27 Updated world Koppen Geiger climate classification map PDF Archived from the original PDF on 2007 10 24 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 Intergovernmental Panel on Climate Change ed 2014 03 24 Climate Change 2013 The Physical Science Basis doi 10 1017 cbo9781107415324 ISBN 978 1 107 05799 9 TROPICALITY Meaning amp Definition for UK English Lexico com Lexico Dictionaries English Archived from the original on March 25 2022 Retrieved 2022 03 25 Arnold David Illusory Riches Representations of the Tropical World 1840 1950 p 6 Journal of Tropical Geography Arnold David Illusory Riches Representations of the Tropical World 1840 1950 p 7 Journal of Tropical Geography 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 Arnold David Illusory Riches Representations of the Tropical World 1840 1950 p 13 Journal of Tropical GeographyExternal linksMedia related to Tropics at Wikimedia Commons
