Subtropics

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Subtropical climate according to Troll and Paffen

For information on the American literary journal, see Subtropics (journal)

The subtropics are the zones of the Earth immediately north and south of the tropic zone, which is bounded by the Tropic of Cancer and the Tropic of Capricorn, at latitude 23.5° north and south. The term "subtropical" describes the climatic region found adjacent to the tropics, usually between 20 and 35 degrees latitude in both hemispheres, but occasionally found at slightly higher latitudes.

[edit] Definitions

According to climatologist Glenn G. Trewartha, a subtropical region should have at least eight months with a mean temperature of 10° C (50 °F) or above. His revision of Köppen climate classification assigns to such areas the letter C, while others zones encompassed in the original Köppen group C class would be considered part of group D.

American climatologist John F. Griffiths in his book Applied climatology described the subtropical zone as having a coldest month of between 6 °C (42.8 °F) and 18 °C (64.4 °F) and assigning to this group the letter B, while the original B group of Köppen taxonomy would be spread over the various temperature-based groups.

German climatologists Carl Troll and Karl-Heinz Paffen defined warmgemäßigte Zonen ("Warm temperate zones") plain and hilly lands having an average temperature of the coldest month between 13 °C (55.4 °F) and 2 °C (35.6 °F) in Northern Hemisphere and between 13 °C and 6 °C (42.8 °F) in Southern Hemisphere, excluding oceanic and continental climates and considered them subtropical.

[edit] Characteristics

In subtropical climates the winters are relatively warm, but not as hot as the summer season. These climates rarely—if ever—see frost or snow, and plants such as palm, citrus and many broadleaf evergreens flourish, in contrast to the hardier deciduous and coniferous trees which dominate midlatitude climates. As one moves toward the tropical side the slight winter cool season disappears altogether, while at the polar threshold of the subtropics the winters become much cooler.

Rainfall patterns vary widely throughout the subtropics including hot deserts, savannas, monsoon forests, humid forests and the warmer parts of the Mediterranean climate zone. Subtropical regions include most of California (Mediterranean type), the low deserts of the Southwest USA (hot arid type), the Gulf Coast and most of Florida (humid type), the southern Mediterranean and northern Sahara, northern India (monsoon), southeast China (humid), the middle part of South America (varied), much of Australia (varied) and coastal South Africa. Even the far Southwestern fringes of Cornwall in the United Kingdom meet both requirements—6 °C average in the coldest month and eight months with the average above 10 °C (specifically the Isles of Scilly). Plymouth in Devon just meets the John F. Griffiths' requirement for a subtropical climate—average 9 C max and 4 °C min in the coldest month. And it is not surprising therefore that there are real palm trees growing in Devon and Cornwall.