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The subtropical zones or subtropics are geographical and climate zones to the
north North is one of the four compass points or cardinal directions. It is the opposite of south and is perpendicular to east and west. ''North'' is a noun, adjective, or adverb indicating direction or geography. Etymology The word ''north ...
and south of the
tropics The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in the Southern Hemisphere at S. The tropics are also refer ...
. Geographically part of the
temperate zones In geography, the temperate climates of Earth occur in the middle latitudes (23.5° to 66.5° N/S of Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ranges throughout ...
of both hemispheres, they cover the
middle latitudes The middle latitudes (also called the mid-latitudes, sometimes midlatitudes, or moderate latitudes) are a spatial region on Earth located between the Tropic of Cancer ( latitudes 23°26'22") to the Arctic Circle (66°33'39"), and Tropic of Cap ...
from to approximately 35° north and south. The horse latitudes lie within this range. Subtropical climates are often characterized by hot summers and mild winters with infrequent frost. Most subtropical climates fall into two basic types: humid subtropical ( Koppen climate Cfa), where rainfall is often concentrated in the warmest months, for example Southeast China and the
Southeastern United States The Southeastern United States, also referred to as the American Southeast or simply the Southeast, is a geographical List of regions in the United States, region of the United States. It is located broadly on the eastern portion of the south ...
, and
dry summer ''Dry Summer'' (a.k.a. ''Reflections''; tr, Susuz Yaz) is a 1964 black-and-white Turkish drama film, co-produced, co-written and directed by Metin Erksan based on a novel by Necati Cumalı, featuring Erol Taş as a tobacco farmer, who dams a rive ...
or
Mediterranean climate A Mediterranean climate (also called a dry summer temperate climate ''Cs'') is a temperate climate sub-type, generally characterized by warm, dry summers and mild, fairly wet winters; these weather conditions are typically experienced in the ...
( Koppen climate Csa/Csb), where seasonal rainfall is concentrated in the cooler months, such as the Mediterranean Basin or
Southern California Southern California (commonly shortened to SoCal) is a geographic and cultural region that generally comprises the southern portion of the U.S. state of California. It includes the Los Angeles metropolitan area, the second most populous urban ...
. Subtropical climates can also occur at high elevations within the
tropics The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in the Southern Hemisphere at S. The tropics are also refer ...
, such as in the southern end of the Mexican Plateau and in Da Lat of the Vietnamese Central Highlands. The six climate classifications use the term to help define the various
temperature Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer. Thermometers are calibrated in various temperature scales that historically have relied o ...
and
precipitation In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls under gravitational pull from clouds. The main forms of precipitation include drizzle, rain, sleet, snow, ice pellets, graupel and hail. ...
regimes for planet
Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's sur ...
. A great portion of the world's deserts are within the subtropics, as this is where the semi-permanent subtropical anticyclone resides (typically inland on the southwest sides of continents). Areas bordering warm oceans (typically on the southeast sides of continents) have hot and wet summers with frequent (but brief) convective rainfall (
tropical cyclone A tropical cyclone is a rapidly rotating storm system characterized by a low-pressure center, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and squalls. Dep ...
s can also contribute to annual rainfall). Areas bordering cool oceans (typically on the southwest sides of continents) are prone to fog, aridity, and dry summers. Plants such as palms,
citrus ''Citrus'' is a genus of flowering trees and shrubs in the rue family, Rutaceae. Plants in the genus produce citrus fruits, including important crops such as oranges, lemons, grapefruits, pomelos, and limes. The genus ''Citrus'' is native to ...
, mango, pistachio, lychee, and avocado are grown in the subtropics.


Definition

The tropics have been ''historically'' defined as lying between the Tropic of Cancer and Tropic of Capricorn, at latitudes north and south, respectively. According to the American Meteorological Society, the poleward fringe of the subtropics is at latitudes approximately 35° north and south, respectively. Several methods have been used to define the subtropical climate depending on the climate system used. The most well known is the Trewartha climate classification, which defines a subtropical region as one that has at least eight months with a mean temperature greater than and at least one month with a mean temperature under . In most regions in this climate zone the coldest month has a mean temperature of above and the hottest month has a mean temperature of above . In the Trewartha climate classification, most of these climates are in the southernmost portions of the temperate zone (latitudes between 23.5° and 35° north and south), aka the subtropics. German climatologists Carl Troll and Karlheinz Paffen defined ''warm temperate zones'' as plain and hilly lands having an average temperature of the coldest month between and in the Northern Hemisphere and between and in the Southern Hemisphere, excluding oceanic and continental climates. According to the Troll-Paffen climate classification, there generally exists one large subtropical zone named the warm-temperate subtropical zone, which is subdivided into seven smaller areas. According to the E. Neef climate classification, the subtropical zone is divided into two parts: ''rainy winters of the west sides'' and ''eastern subtropical climate''. According to the Wilhelm Lauer & Peter Frankenberg climate classification, the subtropical zone is divided into three parts: ''high-continental'', ''continental'', and ''maritime''. According to the Siegmund/Frankenberg climate classification, subtropical is one of six climate zones in the world. Leslie Holdridge defined the subtropical climates as having a mean annual
biotemperature The Holdridge life zones system is a global bioclimatic scheme for the classification of land areas. It was first published by Leslie Holdridge in 1947, and updated in 1967. It is a relatively simple system based on few empirical data, giving ob ...
between the frost line or critical temperature line, 16 °C to 18 °C (depending on locations in the world), and 24 °C. The frost line separates the warm temperate region from the subtropical region. It represents the dividing line between two major physiological groups of evolved plants. Most of the plants are sensitive to low temperatures on the warmer side of the line. They can be killed back by frosts as they have not evolved to withstand periods of cold. On the colder temperate side of the line, the total flora is adapted to survive periods of variable lengths of low temperatures, whether as seeds in the case of the annuals or as perennial plants that can withstand the cold. The 16 °C–18 °C segment is often "simplified" as 17 °C \bigl(2^\ ^\circ\! \mathrm \approx16.97\ ^\circ\! \mathrm\bigr). The Holdridge subtropical climates straddle more or less the warmest subtropical climates and the less warm tropical climates as defined by the Köppen-Geiger or Trewartha climate classifications. However Wladimir Köppen has distinguished the hot or subtropical and tropical (semi-)arid climates (''BWh'' or ''BSh'') having an average annual temperature greater than or equal to from the cold or temperate (semi-)arid climates (''BWk'' or ''BSk'') whose annual temperature average is lower. This definition, though restricted to dry regions, is almost similar to Holdridge's.


Rainfall

Heating of the earth by the sun near the equator leads to large amounts of upward motion and convection winds along the monsoon trough or intertropical convergence zone. The upper-level divergence over the near-equatorial trough leads to air rising and moving away from the equator aloft. As the air moves towards the mid-latitudes, it cools, gets denser and sinks, which leads to subsidence near the 30th parallel of both hemispheres. This circulation is known as the Hadley cell and leads to the formation of the
subtropical ridge The horse latitudes are the latitudes about 30 degrees north and south of the Equator. They are characterized by sunny skies, calm winds, and very little precipitation. They are also known as subtropical ridges, or highs. It is a high-press ...
. Many of the world's deserts are caused by these climatological high-pressure areas, within the subtropics. This regime is known as a semiarid/ arid subtropical climate, which is generally in areas adjacent to powerful cold ocean currents. Examples of this climate are the coastal areas of Southern Africa and the west coast of
South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the sou ...
. The humid subtropical climate is often on the western side of the subtropical high. Here, unstable tropical airmasses in summer bring convective overturning and frequent tropical downpours, and summer is normally the season of peak annual rainfall. In the winter (dry season) the monsoon retreats, and the drier
trade winds The trade winds or easterlies are the permanent east-to-west prevailing winds that flow in the Earth's equatorial region. The trade winds blow mainly from the northeast in the Northern Hemisphere and from the southeast in the Southern Hemisp ...
bring more stable airmass and often dry weather, and frequent sunny skies. Areas that have this type of subtropical climate include Australia, Southeast Asia, and parts of South America. In areas bounded by warm ocean like the southeastern United States and East Asia, tropical cyclones can contribute significantly to local rainfall within the subtropics.
Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the n ...
receives over half of its rainfall from typhoons. The
Mediterranean climate A Mediterranean climate (also called a dry summer temperate climate ''Cs'') is a temperate climate sub-type, generally characterized by warm, dry summers and mild, fairly wet winters; these weather conditions are typically experienced in the ...
is a subtropical climate with a wet season in winter and a dry season in the summer. Regions with this type of climate include the rim lands of the
Mediterranean Sea The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western and Southern Europe and Anatolia, on the south by North Africa, and on ...
,
southwestern Australia Southwest Australia is a biogeographic region in Western Australia. It includes the Mediterranean-climate area of southwestern Australia, which is home to a diverse and distinctive flora and fauna. The region is also known as the Southwest A ...
, parts of the west coast of South America around
Santiago Santiago (, ; ), also known as Santiago de Chile, is the capital and largest city of Chile as well as one of the largest cities in the Americas. It is the center of Chile's most densely populated region, the Santiago Metropolitan Region, whos ...
, the coastal areas of the lower west coast of the United States. J. Horel (2006)
Normal Monthly Precipitation, Inches.
University of Utah. Retrieved on 19 March 2008.


Flora

These climates do not routinely see hard freezes or snow due to winter on average being above freezing, which allows plants such as palms and citrus to flourish. As one moves toward the tropical side the slight winter cool season disappears, while at the poleward threshold of the subtropics the winters become cooler. Some crops which have been traditionally farmed in tropical climates, such as mango, litchi, and avocado, are also cultivated in the subtropics. Pest control of the crops is easier than in the tropics, due to the cooler winters. Tree ferns ( pteridophytes) are grown in subtropical areas, as are dracaena and
yucca ''Yucca'' is a genus of perennial shrubs and trees in the family Asparagaceae, subfamily Agavoideae. Its 40–50 species are notable for their rosettes of evergreen, tough, sword-shaped leaves and large terminal panicles of white or whitis ...
, and trees in the Taxaceae.
Apple An apple is an edible fruit produced by an apple tree (''Malus domestica''). Apple trees are cultivated worldwide and are the most widely grown species in the genus '' Malus''. The tree originated in Central Asia, where its wild ancest ...
, pear and pomegranate also grow well in the subtropics.


Varieties


Humid subtropical climate

The humid subtropical climate is a subtropical climate type characterized by hot, humid summers and generally mild winters. This climate can be found in
Northern Vietnam Northern Vietnam ( vi, Bắc Bộ) is one of three geographical regions within Vietnam. It consists of three administrative regions: the Northwest (Vùng Tây Bắc), the Northeast (Vùng Đông Bắc), and the Red River Delta (Đồng Bằng ...
(including
Hanoi Hanoi or Ha Noi ( or ; vi, Hà Nội ) is the capital and second-largest city of Vietnam. It covers an area of . It consists of 12 urban districts, one district-leveled town and 17 rural districts. Located within the Red River Delta, Hanoi i ...
), eastern
Australia Australia, officially the Commonwealth of Australia, is a sovereign country comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands. With an area of , Australia is the largest country by ...
, southern and southeast
China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's List of countries and dependencies by population, most populous country, with a Population of China, population exceeding 1.4 billion, slig ...
, southern
Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the n ...
, the deep
southeastern United States The Southeastern United States, also referred to as the American Southeast or simply the Southeast, is a geographical List of regions in the United States, region of the United States. It is located broadly on the eastern portion of the south ...
, and southeast
South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the sou ...
area. In most humid subtropical climates, summer is the wettest season. In summer, the subtropical high pressure cells provide a sultry southernly flow of tropical air with high dew points, and frequent (but brief) convective showers are common. With decreasing latitude most humid subtropical climates typically have drier winters and wetter summers, however some sectors with this climate see a more even rhythm of seasonal rainfall. Tropical lows and weakening tropical storms often contribute to seasonal rainfall in most humid subtropical climates. In the cool season (winter) the subtropical highs retreat, and the humid subtropics are more influenced by the westerlies and the fronts and storms that move with them.


Mediterranean climate

The Mediterranean climate regime resembles the climate of the lands in the Mediterranean Basin, parts of lower West Coast of the United States, parts of Western and South Australia, in southwestern
South Africa South Africa, officially the Republic of South Africa (RSA), is the southernmost country in Africa. It is bounded to the south by of coastline that stretch along the South Atlantic and Indian Oceans; to the north by the neighbouring coun ...
and in parts of central
Chile Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the eas ...
. The climate is characterized by hot dry summers and cooler winters with rainfall. In Europe, the northernmost mediterranean climates are found along the Italian Riviera, at 44° latitude. Parts of southwestern Australia around Perth have a Mediterranean climate as do areas around coastal South Africa.


Semi-desert/desert climate

According to Köppen, arid subtropical climates are characterized by an annual average temperature above , the absence of regular rainfall, and high humidity.


See also

* Geographical zone * Subtropical cyclone * 35th parallel north * 35th parallel south * Tropic of Cancer * Tropic of Capricorn


References

{{Authority control Physical geography Climate zones