Northern Hemisphere

Northern Hemisphere: most populous, land-rich half of Earth.

via Wikipedia: Northern Hemisphere · see source

The Northern Hemisphere is the portion of Earth located north of the equator. On other planets in our solar system, "north" is defined as the hemisphere that points toward the same part of the sky as Earth's North Pole, relative to the solar system's invariable plane.

Because Earth's axis is tilted by 23.439281°, the length of day and night changes with the seasons, and temperature shifts follow those daylight changes with a delay. By convention, winter in the Northern Hemisphere runs from the December solstice (around December 21 UTC) to the March equinox (around March 20 UTC), while summer spans from the June solstice to the September equinox (around September 23 UTC). These dates shift slightly each year because the calendar year and the astronomical year don't align perfectly. Ocean currents can alter weather patterns along northern coasts, including events like El Niño–Southern Oscillation.

Just above the equator, trade winds blow from east to west. These winds pull surface water along, creating currents that flow westward due to the Coriolis effect. The currents then curve to the right, heading north. Near 30° north latitude, westerly winds push the currents back east, forming a closed clockwise loop.

The Northern Hemisphere is 60.7% water (compared to 80.9% in the Southern Hemisphere) and holds 67.3% of Earth's land. It contains all of North America and mainland Eurasia, plus about two-thirds of Africa and a small part of South America.

During the Pleistocene, which lasted about 2.5 million years, the Northern Hemisphere experienced many cold phases called glacials, when continental ice sheets advanced across Europe and North America. These glacial periods occurred roughly every 40,000 to 100,000 years and were separated by shorter, warmer interglacials lasting about 10,000–15,000 years. The last cold episode of the most recent glacial period ended around 10,000 years ago. Earth is now in an interglacial period of the Quaternary, known as the Holocene.

The Arctic, centered on the North Pole (90° latitude), has cold winters and cool summers, with precipitation mostly falling as snow. Locations within the Arctic Circle (66°34′ latitude) experience days in summer when the Sun never sets and days in winter when it never rises—lasting from one day at the circle to several months at the Pole. Between the Arctic Circle and the Tropic of Cancer (23°26′ latitude) lies the Northern temperate zone, where seasonal changes are generally mild but weather can be unpredictable. Tropical regions, from the Tropic of Cancer to the equator, are hot year-round, with a rainy season in summer and a dry season in winter.

Because of the Coriolis effect, objects moving across or above the Northern Hemisphere's surface turn to the right. This causes large-scale air and water flows to form clockwise gyres, seen in the North Atlantic and North Pacific. High-pressure weather cells spin clockwise, while low-pressure systems like hurricanes and tropical storms spin counterclockwise. Ocean currents in the Northern Hemisphere can also affect coastal weather patterns.

A sundial's shadow moves clockwise north of the subsolar point and anticlockwise south of it. During the day, the Sun rises to its maximum at a southerly position. Between the Tropic of Cancer and the equator, the Sun may appear north, directly overhead, or south at noon depending on the season. The Moon appears inverted when viewed from the Northern Hemisphere compared to the Southern Hemisphere. The North Pole points away from the Milky Way's galactic center, making the Milky Way sparser and dimmer in the Northern Hemisphere, which is better for deep-space observation since it isn't "blinded" by the galaxy.

As of 2015, about 6.4 billion people—87.0% of Earth's total population of 7.3 billion—live in the Northern Hemisphere.

Quick Facts

Surface water percentage

60.7%

Land percentage

67.3%

Population percentage

87.0%

Major continents

North America
mainland Eurasia
about two-thirds of Africa
small part of South

Facts from the source article.

Lore & Background

Due to Earth's axial tilt of 23.439281°, there is a seasonal variation in the lengths of the day and night, and a seasonal variation in temperatures that 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. 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, best seen in ocean circulation patterns in the North Atlantic and North Pacific oceans. Clockwise air circulation is characteristic of high pressure weather cells, while hurricanes and tropical storms spin counterclockwise in the Northern Hemisphere. During the 2.5 million years of the Pleistocene, numerous cold phases, called glacials, 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. Earth is currently in an interglacial period of the Quaternary, called the Holocene. The Arctic is a region around the North Pole (90° latitude) with cold winters and cool summers. 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.

Reader's Guide

The Northern Hemisphere is defined as 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. The shadow of a sundial moves clockwise on latitudes north of the subsolar point. 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. When viewed from the Northern Hemisphere, the Moon appears inverted compared to a view from the Southern Hemisphere. The North Pole faces away from the Galactic Center of the Milky Way, resulting 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. Tropical regions (between the Tropic of Cancer and the Equator) 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. Between the Arctic Circle and the Tropic of Cancer lies the Northern temperate zone, where changes between summer and winter are generally mild, rather than extreme hot or cold, though a temperate climate can have very unpredictable weather. The Northern Hemisphere contains the continents of North America and mainland Eurasia, about two-thirds of Africa, and a small part of South America. Its oceans include the Arctic Ocean, Atlantic Ocean, Indian Ocean, and Pacific Ocean.