The thermal equator (also known as "the heat equator") is a belt encircling

Earth Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...

, defined by the set of locations having the highest mean annual

temperature Temperature is a physical quantity that quantitatively expresses the attribute of hotness or coldness. Temperature is measurement, measured with a thermometer. It reflects the average kinetic energy of the vibrating and colliding atoms making ...

at each

longitude Longitude (, ) is a geographic coordinate that specifies the east- west position of a point on the surface of the Earth, or another celestial body. It is an angular measurement, usually expressed in degrees and denoted by the Greek lett ...

around the globe. Because local temperatures are sensitive to the

geography Geography (from Ancient Greek ; combining 'Earth' and 'write', literally 'Earth writing') is the study of the lands, features, inhabitants, and phenomena of Earth. Geography is an all-encompassing discipline that seeks an understanding o ...

of a region, mountain ranges and ocean currents ensure that smooth temperature gradients (such as might be found if Earth were uniform in composition and devoid of surface irregularities) are impossible, the location of the thermal equator is not identical to that of the geographic

Equator The equator is the circle of latitude that divides Earth into the Northern Hemisphere, Northern and Southern Hemisphere, Southern Hemispheres of Earth, hemispheres. It is an imaginary line located at 0 degrees latitude, about in circumferen ...

. The term is less frequently used to describe the belt of maximum temperatures surrounding the globe which migrates roughly between the

Tropic of Cancer The Tropic of Cancer, also known as the Northern Tropic, is the Earth's northernmost circle of latitude where the Sun can be seen directly overhead. This occurs on the June solstice, when the Northern Hemisphere is tilted toward the Sun ...

and the Tropic of Capricorn. This region is known as the

Intertropical Convergence Zone The Intertropical Convergence Zone (ITCZ , or ICZ), known by sailors as the doldrums or the calms because of its monotonous windless weather, is the area where the northeast and the southeast trade winds converge. It encircles Earth near the t ...

. This zone is the result of trade winds from the northern and southern part of the hemisphere eventually joining together. Still another definition states that the thermal equator is the latitude at which insolation is identical throughout the year. This is not the same as the astronomical equator because Earth reaches perihelion (the minimum distance from the Sun in its orbit) in early January and is at aphelion (maximum distance) in early July. Therefore, insolation is somewhat higher at 0° latitude in January than in July even though the height of the Sun (at noon) and the length of day (from sunrise to sunset) is essentially the same. At a few degrees north of the Equator, the perihelion/aphelion factor is balanced by the fact that the angle of the Sun is slightly more direct, and the days are slightly longer, at the time of the summer solstice for the Northern Hemisphere (most commonly on June 21), making the level of insolation virtually the same in both "summer" and "winter."

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Current temperature map
Climate zones Physical geography

See also

References

External links