A great portion of the world's deserts are located within the subtropics, due to the development of the
subtropical ridge. Within
savanna regimes in the subtropics, a
wet season is seen annually during the summer, which is when most of the yearly rainfall falls. Within
Mediterranean climate regimes, the wet season occurs during the winter. Areas bordering warm oceans are prone to locally heavy rainfall from
tropical cyclones, which can contribute a significant percentage of the annual rainfall. Plants such as
avocado are grown within the subtropics.
The tropics have been historically defined as lying between the
Tropic of Cancer and
Tropic of Capricorn, located at latitudes 23.45° north and south, respectively. According to the American Meteorological Society, the poleward fringe of the subtropics is located at latitudes approximately
35° north and
Several methods have been used to define the subtropical climate. In the
Trewartha climate classification, a subtropical region should have at least eight months with a mean temperature greater than 10 °C (50.0 °F) and at least one month with a mean temperature under 18 °C (64.4 °F). 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 2 °C (35.6 °F) and 13 °C (55.4 °F) in the
Northern Hemisphere and between 6 °C (42.8 °F) and 13 °C (55.4 °F) in the
Southern Hemisphere, excluding
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.
Hadley cells located on the Earth's atmospheric circulation.
Heating of the earth near the equator leads to large amounts of upward motion and convection 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 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. Many of the world's deserts are caused by these climatological
high-pressure areas, located within the subtropics. This regime is known as an arid subtropical climate, which is generally located in areas adjacent to powerful cold ocean currents. Examples of this climate are the coastal areas of southern Africa (Namibia, South Africa), the south of the Canary Islands and the coasts of Peru and Chile.
humid subtropical climate is often located 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 bring more stable airmass and often dry weather, and frequent sunny skies. Areas that have this type of subtropical climate include Australia, Southeast Asia, parts of South America, and the deep south of the United States. 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 receives over half of its rainfall from typhoons.
Mediterranean climate is a subtropical climate with a wet season in winter and a dry season in the summer. Regions with this type of climate include western
Mexico. the Desert Southwest of the United States, Within the
Mediterranean climate regime, the west coast of the United States and the
Mediterranean coastline of Italy, Greece, and Turkey experience a wet season in the winter months. Similarly, the wet season in the
Negev desert of
Israel extends from October through May. At the boundary between the Mediterranean and monsoon climates in
North America lies the
Sonoran desert, which receives the two rainy seasons associated with each climate regime.
These climates do not routinely see hard frosts or snow, 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 cultivated in the subtropics. Pest control of the crops is less difficult than within the tropics, due to the cooler winters.
Tree ferns (
pteridophytes) are grown within subtropical areas, primarily within the subtropics and within topography within the
yucca can grow within the subtropics. Trees within the
Taxaceae family grow within subtropical climate regimes. Apple, pear and pomegranates grow well within the subtropics.
The humid subtropical climate is a subtropical climate type characterized by hot, humid summers with frequent tropical downpours of short duration and warm, and frequently dry winters. In summer, the subtropical high pressure cells bring a sultry flow of tropical air with high dew points, and daily thundershowers are typical, though brief. Normally, rainfall is concentrated in the warmest months of the year. At times, the average annual precipitation may be more evenly distributed throughout the year, or a spring maximum is present. With decreasing latitude most humid subtropical climates typically have drier winters and wetter summers.
Humid subtropical climates lie on the lower east side of continents, roughly between
latitudes 25° and 35° degrees away from the equator. In the United States, the humid subtropical zone is normally considered the region from central
Florida north to northeastern
The Mediterranean climate regime resembles the climate of the lands in the
Mediterranean Basin, parts of coastal southwestern North America, parts of
South Australia, in southwestern
South Africa and in parts of central
Chile. The climate is characterized by hot dry summers and cooler winters with rainfall. In Europe, the northernmost mediterranean climates are found along the
French Riviera, located at 43° latitude. On the immediate Atlantic coastline, the mediterranean boundary goes between
Vigo at around 41° latitude. Parts of southwestern Australia around Perth have a Mediterranean climate as does areas around coastal South Africa.