In climatology, the term ''megathermal'' (or less commonly, ''macrothermal'') is sometimes used as a synonym for ''

tropical 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 referred to ...

''. It comes from the two greek words "mega" and "thermal" meaning "big" and "heat". In order for a particular place to qualify as having a megathermal climate, every single month out of the year must have an average

temperature Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measurement, measured with a thermometer. Thermometers are calibrated in various Conversion of units of temperature, temp ...

of 18 °C or above.

Areas

Megathermal climates mainly exist in the tropics. It ranges from southeast

Asia Asia (, ) is one of the world's most notable geographical regions, which is either considered a continent in its own right or a subcontinent of Eurasia, which shares the continental landmass of Afro-Eurasia with Africa. Asia covers an area ...

and most of India to the most northern regions of Australia as well as southern parts of Mexico and Florida, nearly all of

Central America Central America ( es, América Central or ) is a subregion of the Americas. Its boundaries are defined as bordering the United States to the north, Colombia to the south, the Caribbean Sea to the east, and the Pacific Ocean to the west. C ...

and most of Brazil. An arid type prevails to some of northern

Africa Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...

while in the center of the continent and in parts of

Madagascar Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), is an island country in the Indian Ocean, approximately off the coast of East Africa ...

the climate stays humid. Many islands, especially in the

Pacific ocean The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the contin ...

, also have megathermal climates.

Variants

Megathermal climates are sometimes split into two temperature-based subsets — equatorial and tropical (the latter used here in the sense of "outer tropical") — with "equatorial" denoting little or no variation in temperature throughout the year and "tropical" denoting significant seasonal temperature variation, even though no month has an average temperature of below 18 °C. In addition, what temperature fluctuations do exist in an equatorial climate will typically bear no relationship to the astronomical seasons for the applicable side of the

equator The equator is a circle of latitude, about in circumference, that divides Earth into the Northern and Southern hemispheres. It is an imaginary line located at 0 degrees latitude, halfway between the North and South poles. The term can al ...

, while in the (outer) tropical subtype the temperature will move in concert with the seasons, the time of higher sun and longer days being warmest and the time of lower sun and shorter days coolest. These climates can also be subdivided on the basis of

rain Rain is water droplets that have condensed from atmospheric water vapor and then fall under gravity. Rain is a major component of the water cycle and is responsible for depositing most of the fresh water on the Earth. It provides water fo ...

fall, as examples of

humid Humidity is the concentration of water vapor present in the air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation, dew, or fog to be present. Humidity depen ...

seasonal A season is a division of the year based on changes in weather, ecology, and the number of daylight hours in a given region. On Earth, seasons are the result of the axial parallelism of Earth's tilted orbit around the Sun. In temperate and pol ...

semiarid A semi-arid climate, semi-desert climate, or steppe climate is a dry climate sub-type. It is located on regions that receive precipitation below potential evapotranspiration, but not as low as a desert climate. There are different kinds of semi-ar ...

and

arid A region is arid when it severely lacks available water, to the extent of hindering or preventing the growth and development of plant and animal life. Regions with arid climates tend to lack vegetation and are called xeric or desertic. Most a ...

places can all be found within the megathermal category (although the region of arid megathermal climate is small compared with the extent of deserts existing in other climate zones, particularly the neighboring

subtropical The subtropical zones or subtropics are geographical and climate zones to the north and south of the tropics. Geographically part of the temperate zones of both hemispheres, they cover the middle latitudes from to approximately 35° north and ...

zone).

References

Climatic classification in forestry

Areas

Variants

References

See also