Northern Hemisphere Explained

The Northern Hemisphere is the half of Earth that is north of the Equator. For other planets in the Solar System, north is defined as being in the same celestial hemisphere relative to the invariable plane of the Solar System as Earth's North Pole.[1]

Due to Earth's axial tilt of 23.439281°, there is a seasonal variation in the lengths of the day and night. There is also a seasonal variation in temperatures, which lags the variation in day and night. Conventionally, winter in the Northern Hemisphere is taken as the period from the December solstice (typically December 21 UTC) to the March equinox (typically March 20 UTC), while summer is taken as the period from the June solstice through to the September equinox (typically on 23 September UTC). The dates vary each year due to the difference between the calendar year and the astronomical year. Within the Northern Hemisphere, oceanic currents can change the weather patterns that affect many factors within the north coast. Such events include El Niño–Southern Oscillation.

Trade winds blow from east to west just above the equator. The winds pull surface water with them, creating currents, which flow westward due to the Coriolis effect. The currents then bend to the right, heading north. At about 30 degrees north latitude, a different set of winds, the westerlies, push the currents back to the east, producing a closed clockwise loop.[2]

Its surface is 60.7% water, compared with 80.9% water in the case of the Southern Hemisphere, and it contains 67.3% of Earth's land.[3] The continents of North America and mainland Eurasia are located entirely in the Northern Hemisphere, together with about two-thirds of Africa and a small part of South America.

Geography and climate

During the 2.5 million years of the Pleistocene, numerous cold phases called glacials (Quaternary ice age), or significant advances of continental ice sheets, in Europe and North America, occurred at intervals of approximately 40,000 to 100,000 years. The long glacial periods were separated by more temperate and shorter interglacials which lasted about 10,000–15,000 years. The last cold episode of the last glacial period ended about 10,000 years ago.[4] Earth is currently in an interglacial period of the Quaternary, called the Holocene.[5] The glaciations that occurred during the glacial period covered many areas of the Northern Hemisphere.

The Arctic is a region around the North Pole (90° latitude). Its climate is characterized by cold winters and cool summers. Precipitation mostly comes in the form of snow. Areas inside the Arctic Circle (66°34′ latitude) experience some days in summer when the Sun never sets, and some days during the winter when it never rises. The duration of these phases varies from one day for locations right on the Arctic Circle to several months near the Pole, which is the middle of the Northern Hemisphere. Between the Arctic Circle and the Tropic of Cancer (23°26′ latitude) lies the Northern temperate zone. The changes in these regions between summer and winter are generally mild, rather than extreme hot or cold. However, a temperate climate can have very unpredictable weather.

Tropical regions (between the Tropic of Cancer and the Equator, 0° latitude) are generally hot all year round and tend to experience a rainy season during the summer months, and a dry season during the winter months.

In the Northern Hemisphere, objects moving across or above the surface of the Earth tend to turn to the right because of the Coriolis effect. As a result, large-scale horizontal flows of air or water tend to form clockwise-turning gyres.[6] These are best seen in ocean circulation patterns in the North Atlantic and North Pacific oceans.[6] Within the Northern Hemisphere, oceanic currents can change the weather patterns that affect many factors within the north coast.[7] For the same reason, flows of air down toward the northern surface of the Earth tend to spread across the surface in a clockwise pattern. Thus, clockwise air circulation is characteristic of high pressure weather cells in the Northern Hemisphere. Conversely, air rising from the northern surface of the Earth (creating a region of low pressure) tends to draw air toward it in a counterclockwise pattern. Hurricanes and tropical storms (massive low-pressure systems) spin counterclockwise in the Northern Hemisphere.[8]

The shadow of a sundial moves clockwise on latitudes north of the subsolar point and anticlockwise to the south. During the day at these latitudes, the Sun tends to rise to its maximum at a southerly position. Between the Tropic of Cancer and the Equator, the sun can be seen to the north, directly overhead, or to the south at noon, depending on the time of year. In the Southern Hemisphere, the midday Sun is predominantly in the north.

When viewed from the Northern Hemisphere, the Moon appears inverted compared to a view from the Southern Hemisphere.[9] [10] The North Pole faces away from the Galactic Center of the Milky Way. This results in the Milky Way being sparser and dimmer in the Northern Hemisphere compared to the Southern Hemisphere, making the Northern Hemisphere more suitable for deep-space observation, as it is not "blinded" by the Milky Way.

Demographics

As of 2015, the Northern Hemisphere is home to approximately 6.4 billion people, which is around 87.0% of the Earth's total human population of 7.3 billion people.[11] [12] [13]

List of continents, countries or territories, and oceans in the Northern Hemisphere

Continents
width=25%Africawidth=25%Asiawidth=25%Americaswidth=25%Europe
About two-thirds, from north of Libreville in Gabon in the west to south of Mogadishu in Somalia in the east. The entire continental mainland. Part of Indonesia, and 24 out of 26 atolls of Maldives in the Indian Ocean, are also in the Northern Hemisphere. All of North America, Central America, and the Caribbean islands. About one-fifth of South America, from north of Quito in Ecuador in the west to north of the Amazon River mouth in Brazil in the east. Entirely in the Northern Hemisphere
Countries or Territories
AfricaAsiaAmericasEurope
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Entirely
Mostly
Partly
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Entirely
Mostly
  • Maldives
Partly
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Entirely
Mostly
Partly
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Entirely
Mostly
Oceans
ArcticAtlanticIndianPacific
valign=top
Entirely
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Entirely
Mostly
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Entirely
Mostly
valign=top
Entirely
Mostly
Partly

See also

Notes and References

  1. 10.1007/s10569-010-9320-4. Report of the IAU Working Group on Cartographic Coordinates and Rotational Elements: 2009. Celestial Mechanics and Dynamical Astronomy. 109. 2. 101–135. 2010. Archinal. Brent A.. A'Hearn. Michael F.. Bowell. Edward G.. Conrad. Albert R.. Consolmagno. Guy J.. 5. Courtin. Régis. Fukushima. Toshio. Hestroffer. Daniel. Hilton. James L.. Krasinsky. George A.. Neumann. Gregory A.. Oberst. Jürgen. Seidelmann. P. Kenneth. Stooke. Philip J.. Tholen. David J.. Thomas. Paul C.. Williams. Iwan P.. 2011CeMDA.109..101A. 189842666. 2018-09-26. https://web.archive.org/web/20160304065344/http://astropedia.astrogeology.usgs.gov/alfresco/d/d/workspace/SpacesStore/28fd9e81-1964-44d6-a58b-fbbf61e64e15/WGCCRE2009reprint.pdf. 2016-03-04. dead.
  2. Web site: 2019-07-01. Ocean Currents. 2020-10-16. National Geographic Society. en. 2021-11-20. https://web.archive.org/web/20211120202501/https://www.nationalgeographic.org/encyclopedia/ocean-currents/. live.
  3. Book: Life on Earth: A – G.. 1. 2002. ABC-CLIO. 9781576072868. 528. 8 September 2016. 22 January 2023. https://web.archive.org/web/20230122160606/https://books.google.com/books?id=iVEWPg8vnxgC&q=southern+hemisphere+contains+%25+land&pg=PA528. live.
  4. Quaternary Period. National Geographic. 2017-01-06. 2022-05-06. 2020-11-29. https://web.archive.org/web/20201129042714/https://www.nationalgeographic.com/science/prehistoric-world/quaternary/. dead.
  5. News: How long can we expect the present Interglacial period to last? . U.S. Department of the Interior . 2022-05-06 . 2022-07-26 . https://web.archive.org/web/20220726044340/http://www.usgs.gov/faqs/how-long-can-we-expect-present-interglacial-period-last . live .
  6. Web site: US Department of Commerce. National Oceanic and Atmospheric Administration. Boundary Currents – Currents: NOAA's National Ocean Service Education. 2020-07-31. oceanservice.noaa.gov. EN-US. 2010-05-15. https://web.archive.org/web/20100515015346/https://oceanservice.noaa.gov/education/tutorial_currents/04currents3.html. live.
  7. Web site: How does the ocean affect climate and weather on land? . . NOAA Ocean Exploration . U.S. Department of Commerce . 21 November 2023 .
  8. Web site: Hurricanes: Science and Society: Primary Circulation. 2021-08-11. www.hurricanescience.org. 2010-12-28. https://web.archive.org/web/20101228015456/http://www.hurricanescience.org/science/science/primarycirculation/. live.
  9. Web site: Does the Moon look different in the northern and southern hemispheres? (Beginner) – Curious About Astronomy? Ask an Astronomer. Laura Spitler. cornell.edu. 10 November 2015. 4 November 2015. https://web.archive.org/web/20151104012834/http://curious.astro.cornell.edu/our-solar-system/46-our-solar-system/the-moon/observing-the-moon/135-does-the-moon-look-different-in-the-northern-and-southern-hemispheres-beginner. live.
  10. Web site: Perspective of the Moon from the Northern and Southern Hemispheres. 22 October 2013. https://web.archive.org/web/20170909070809/http://epod.usra.edu/blog/2011/09/perspective-of-the-moon-from-the-northern-and-southern-hemispheres.html. 9 September 2017. dead.
  11. Calculated from World Population Yearbook 2019(in thousands)

    World total population: 7,359,970

    Northern Hemisphere population: 6,405,030 87.0%

    Southern Hemisphere population: 954,940 13.0%

    Note 1) If there is no data for 2019, the latest data was used.

    Note 2) Countries with land that straddles the equator are divided into half populations in each of the Northern and Southern Hemispheres.

  12. Web site: 90% Of People Live In The Northern Hemisphere – Business Insider. 4 May 2012. Business Insider. 10 November 2015. 19 January 2018. https://web.archive.org/web/20180119181108/http://www.businessinsider.com/90-of-people-live-in-the-northern-hemisphere-2012-5. live.
  13. Web site: GIC – Article. galegroup.com. 10 November 2015. 18 April 2016. https://web.archive.org/web/20160418075026/http://find.galegroup.com/gic/infomark.do?&contentSet=EBKS&idigest=fb720fd31d9036c1ed2d1f3a0500fcc2&type=retrieve&tabID=T001&prodId=GIC&docId=CX3403900089&source=gale&userGroupName=itsbtrial&version=1.0. live.

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