Northern Hemisphere

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Coordinates: 90°0′0″N0°0′0″E / 90.00000°N 0.00000°E / 90.00000; 0.00000

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Northern Hemisphere shaded blue. The hemispheres appear unequal here because Antarctica is not shown. Global hemispheres.svg
Northern Hemisphere shaded blue. The hemispheres appear unequal here because Antarctica is not shown.
Northern Hemisphere from above the North Pole Northern Hemisphere LamAz.png
Northern Hemisphere from above the North Pole

The Northern Hemisphere is the top 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]

Owing to the Earth's axial tilt of 23.439281°, winter in the Northern Hemisphere lasts from the December solstice (typically December 21 UTC) to the March equinox (typically March 20 UTC), while summer lasts 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 ENSO (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] Europe and North America are entirely on Earth's Northern Hemisphere.

Geography and climate

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. [4] These are best seen in ocean circulation patterns in the North Atlantic and North Pacific oceans.[ citation needed ] Within the northern hemisphere, oceanic currents can change the weather patterns that affect many factors within the north coast; such as El Niño. [ citation needed ]

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 counter-clockwise pattern. Hurricanes and tropical storms (massive low-pressure systems) spin counter-clockwise in the Northern Hemisphere.[ citation needed ]

The shadow of a sundial moves clockwise on latitudes north of the subsolar point. During the day on 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 dependent on the time of year. In the Southern Hemisphere the midday Sun is predominantly at north.

When viewed from the Northern Hemisphere, the Moon appears inverted compared to a view from the Southern Hemisphere. [5] [6] 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.[ citation needed ]

Demographics

The Northern Hemisphere is home to approximately 6.57 billion people which is around 90% of the earth's total human population of 7.3 billion people. [7] [8]

See also

Related Research Articles

Coriolis force A force on objects moving within a reference frame that rotates with respect to an inertial frame.

In physics, the Coriolis force is an inertial or fictitious force that acts on objects that are in motion within a frame of reference that rotates with respect to an inertial frame. In a reference frame with clockwise rotation, the force acts to the left of the motion of the object. In one with anticlockwise rotation, the force acts to the right. Deflection of an object due to the Coriolis force is called the Coriolis effect. Though recognized previously by others, the mathematical expression for the Coriolis force appeared in an 1835 paper by French scientist Gaspard-Gustave de Coriolis, in connection with the theory of water wheels. Early in the 20th century, the term Coriolis force began to be used in connection with meteorology.

Tropic of Cancer Line of northernmost latitude at which the sun can be directly overhead

The Tropic of Cancer, which is also referred to as the Northern Tropic, is the most northerly circle of latitude on Earth at which the Sun can be directly overhead. This occurs on the June solstice, when the Northern Hemisphere is tilted toward the Sun to its maximum extent. It also reaches 90 degrees below the horizon at solar midnight on the December Solstice. Using a continuously updated formula, the circle is currently 23°26′11.6″ (or 23.43655°) north of the Equator.

Tropic of Capricorn Line of southernmost latitude at which the sun can be directly overhead

The Tropic of Capricorn is the circle of latitude that contains the subsolar point at the December solstice. It is thus the southernmost latitude where the Sun can be seen directly overhead. It also reaches 90 degrees below the horizon at solar midnight on the June Solstice. Its northern equivalent is the Tropic of Cancer.

Circumpolar star Star that never sets

A circumpolar star is a star, as viewed from a given latitude on Earth, that never sets below the horizon due to its apparent proximity to one of the celestial poles. Circumpolar stars are therefore visible from said location toward the nearest pole for the entire night on every night of the year.

Circle of latitude Geographic notion

A circle of latitude on Earth is an abstract east–west circle connecting all locations around Earth at a given latitude.

Anticyclone Weather phenomenon of wind circulating round a high-pressure area

An anticyclone is a weather phenomenon defined as a large-scale circulation of winds around a central region of high atmospheric pressure, clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere. Effects of surface-based anticyclones include clearing skies as well as cooler, drier air. Fog can also form overnight within a region of higher pressure. Mid-tropospheric systems, such as the subtropical ridge, deflect tropical cyclones around their periphery and cause a temperature inversion inhibiting free convection near their center, building up surface-based haze under their base. Anticyclones aloft can form within warm core lows such as tropical cyclones, due to descending cool air from the backside of upper troughs such as polar highs, or from large scale sinking such as the subtropical ridge. The evolution of an anticyclone depends upon variables such as its size, intensity, and extent of moist convection, as well as the Coriolis force.

Southern Hemisphere Half of Earth that is south of the Equator

The Southern Hemisphere is the half of Earth that is south of the Equator. It contains all or parts of five continents, four oceans, New Zealand and most of the Pacific Islands in Oceania. Its surface is 80.9% water, compared with 60.7% water in the case of the Northern Hemisphere, and it contains 32.7% of Earth's land.

Physical oceanography The study of physical conditions and physical processes within the ocean

Physical oceanography is the study of physical conditions and physical processes within the ocean, especially the motions and physical properties of ocean waters.

Atmospheric circulation The large-scale movement of air, a process which distributes thermal energy about the Earths surface

Atmospheric circulation is the large-scale movement of air and together with ocean circulation is the means by which thermal energy is redistributed on the surface of the Earth.

High-pressure area Region where the atmospheric pressure at the surface of the planet is greater than its surrounding environment

A high-pressure area, high, or anticyclone, is a region where the atmospheric pressure at the surface of the planet is greater than its surrounding environment.

Thermal equator

The thermal equator is a belt encircling the Earth, defined by the set of locations having the highest mean annual temperature at each longitude around the globe. Because local temperatures are sensitive to the geography of a region, mountain ranges and ocean currents ensure that smooth temperature gradients are impossible, the location of the thermal equator is not identical to that of the geographic Equator.

Westerlies

The westerlies, anti-trades, or prevailing westerlies, are prevailing winds from the west toward the east in the middle latitudes between 30 and 60 degrees latitude. They originate from the high-pressure areas in the horse latitudes and trend towards the poles and steer extratropical cyclones in this general manner. Tropical cyclones which cross the subtropical ridge axis into the westerlies recurve due to the increased westerly flow. The winds are predominantly from the southwest in the Northern Hemisphere and from the northwest in the Southern Hemisphere.

Polar vortex Persistent cold-core low-pressure area that circles one of the poles

A polar vortex is a persistent, large-scale, upper-level low-pressure area, less than 1,000 kilometers in diameter, that rotates counter-clockwise at the North Pole and clockwise at the South Pole, i.e., both polar vortices rotate eastward around the poles. The vortices weaken and strengthen from year to year. As with other cyclones, their rotation is driven by the Coriolis effect.

Rainfall and the tropical climate dominate the tropical rain belt, which oscillates from the northern to the southern tropics over the course of the year, roughly following the solar equator. The tropical rain belt is an area of active rain that is positioned mostly around the tropics.

Ekman transport Net transport of surface water perpendicular to wind direction

Ekman transport is part of Ekman motion theory, first investigated in 1902 by Vagn Walfrid Ekman. Winds are the main source of energy for ocean circulation, and Ekman Transport is a component of pink- driven ocean current. Ekman transport occurs when ocean surface waters are influenced by the friction force acting on them via the wind. As the wind blows it casts a friction force on the ocean surface that drags the upper 10-100m of the water column with it. However, due to the influence of the Coriolis effect, the ocean water moves at a 90° angle from the direction of the surface wind. The direction of transport is dependent on the hemisphere: in the northern hemisphere, transport occurs at 90° clockwise from wind direction, while in the southern hemisphere it occurs at 90° anticlockwise. This phenomenon was first noted by Fridtjof Nansen, who recorded that ice transport appeared to occur at an angle to the wind direction during his Arctic expedition during the 1890s. Ekman transport has significant impacts on the biogeochemical properties of the world's oceans. This is because they lead to upwelling and downwelling in order to obey mass conservation laws. Mass conservation, in reference to Ekman transfer, requires that any water displaced within an area must be replenished. This can be done by either Ekman suction or Ekman pumping depending on wind patterns.

Geographical zone Major regions of Earths surface demarcated by latitude

The five main latitude regions of Earth's surface comprise geographical zones, divided by the major circles of latitude. The differences between them relate to climate. They are as follows:

  1. The North Frigid Zone, between the North Pole at 90° N and the Arctic Circle at 66° 33' N, covers 4.12% of Earth's surface.
  2. The North Temperate Zone, between the Arctic Circle at 66° 33' N and the Tropic of Cancer at 23° 27' N, covers 25.99% of Earth's surface.
  3. The Torrid Zone, between the Tropic of Cancer at 23° 27' N and the Tropic of Capricorn at 23° 27' S, covers 39.78% of Earth's surface.
  4. The South Temperate Zone, between the Tropic of Capricorn at 23° 27' S and the Antarctic Circle at 66° 33' S, covers 25.99% of Earth's surface.
  5. The South Frigid Zone, from the Antarctic Circle at 66° 33' S and the South Pole at 90° S, covers 4.12% of Earth's surface.
Sun path Arc-like path that the Sun appears to follow across the sky

Sun path, sometimes also called day arc, refers to the daily and seasonal arc-like path that the Sun appears to follow across the sky as the Earth rotates and orbits the Sun. The Sun's path affects the length of daytime experienced and amount of daylight received along a certain latitude during a given season.

Equator Intersection of a spheres surface with the plane perpendicular to the spheres axis of rotation and midway between the poles

Earth's Equator is a specific case of a planetary equator. It is about 40,075 km (24,901 mi) long, of which 78.8% lies across water and 21.3% over land.

Season Subdivision of the year based on orbit and axial tilt

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 Earth's orbit around the Sun and Earth's axial tilt relative to the ecliptic plane. In temperate and polar regions, the seasons are marked by changes in the intensity of sunlight that reaches the Earth's surface, variations of which may cause animals to undergo hibernation or to migrate, and plants to be dormant. Various cultures define the number and nature of seasons based on regional variations, and as such there are a number of both modern and historical cultures whose number of seasons vary.

A Wind generated current is a flow in a body of water that is generated by wind friction on its surface. Wind can generate surface currents on water bodies of any size. The depth and strength of the current depend on the wind strength and duration, and on friction and viscosity losses, but are limited to about 400 m depth by the mechanism, and to lesser depths where the water is shallower. The direction of flow is influenced by the Coriolis effect, and is offset to the right of the wind direction in the Northern Hemisphere, and to the left in the Southern Hemisphere. A wind current can induce secondary water flow in the form of upwelling and downwelling, geostrophic flow, and western boundary currents.

References

  1. Archinal, Brent A.; A'Hearn, Michael F.; Bowell, Edward G.; Conrad, Albert R.; Consolmagno, Guy J.; et al. (2010). "Report of the IAU Working Group on Cartographic Coordinates and Rotational Elements: 2009" (PDF). Celestial Mechanics and Dynamical Astronomy. 109 (2): 101–135. Bibcode:2011CeMDA.109..101A. doi:10.1007/s10569-010-9320-4. S2CID   189842666. Archived from the original (PDF) on 2016-03-04. Retrieved 2018-09-26.
  2. Society, National Geographic (2019-07-01). "Ocean Currents". National Geographic Society. Retrieved 2020-10-16.
  3. Life on Earth: A - G.. 1. ABC-CLIO. 2002. p. 528. ISBN   9781576072868 . Retrieved 8 September 2016.
  4. US Department of Commerce, National Oceanic and Atmospheric Administration. "Boundary Currents - Currents: NOAA's National Ocean Service Education". oceanservice.noaa.gov. Retrieved 2020-07-31.
  5. Laura Spitler. "Does the Moon look different in the northern and southern hemispheres? (Beginner) - Curious About Astronomy? Ask an Astronomer". cornell.edu. Retrieved 10 November 2015.
  6. "Perspective of the Moon from the Northern and Southern Hemispheres". Archived from the original on 9 September 2017. Retrieved 22 October 2013.
  7. "90% Of People Live In The Northern Hemisphere - Business Insider". Business Insider. 4 May 2012. Retrieved 10 November 2015.
  8. "GIC - Article". galegroup.com. Retrieved 10 November 2015.

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