Weather is a term that encompasses phenomena in the atmosphere of a planet. The term usually refers the activity of these phenomena over short periods, such as hours or days. Average atmospheric conditions over significantly longer periods are known as climate. A phenomenon (plural: phenomena) is an observable event, especially something special (literally something that can be seen from the Greek word phainomenon = observable). ... Atmosphere is the general name for a layer of gases that may surround a material body of sufficient mass. ... For the astrological concept, see Planets in astrology. ...

When used without qualification, "weather" is understood to be the weather of Earth. Adjectives: Terrestrial, Terran, Telluric, Tellurian, Earthly Atmosphere Surface pressure: 101. ...

Basic mechanism

Weather most often results from temperature differences from one place to another. On large scales, temperature differences occur mainly because areas closer to Earth's equator receive more energy per unit area from the Sun than do regions closer to Earth's poles. On local scales, temperature differences can occur because different surfaces (such as oceans, forests, or ice sheets) have differing physical characteristics such as reflectivity, roughness, or moisture content. World map showing the equator in red The Equator is an imaginary circle drawn around a planet (or other astronomical object) at a distance halfway between the poles. ... The Sun is the star at the center of the Solar System. ... Oceans (from Okeanos in Greek) are saline waters that cover almost three quarters (71%) of the surface of the Earth. ... Eucalyptus Forest at Swifts Creek in East Gippsland, Victoria, Australia. ... Snowflakes by Wilson Bentley, 1902 Ice is the name given to any one of the 14 known solid phases of water. ... Albedo is a ratio of scattered to incident electromagnetic radiation power. ...

Surface temperature differences in turn cause pressure differences. A hot surface heats the air above it and the air expands, lowering the air pressure. The resulting horizontal pressure gradient accelerates the air from high to low pressure, creating wind, and Earth's rotation then causes curvature of the flow via the Coriolis effect. The simple systems thus formed can then display emergent behaviour to produce more complex systems and thus other weather phenomena. Large scale examples include the Hadley cell while a smaller scale example would be coastal breezes. Fig. ... Image:Tagesgang-luftdruck. ... Pressure Gradient is the change in pressure over a distance. ... Wind is the rough horizontal movement of air (as opposed to an air current) caused by uneven heating of the Earths surface. ... In the inertial frame of reference (upper part of the picture), the black object moves in a straight line. ... A termite cathedral mound produced by a termite colony: a classic example of emergence in nature. ... A pressure system is a region of the Earths atmosphere where air pressure is unusually high or low. ... The Hadley cell is a circulation pattern that dominates the tropical atmosphere, with rising motion near the equator, poleward flow 10-15 kilometers above the surface, descending motion in the subtropics, and equatorward flow near the surface. ... A: Sea breeze, B: Land breeze A sea-breeze (or seabreeze) is a wind from the sea that develops over land near coasts. ...

The strong temperature contrast between polar and tropical air gives rise to the jet stream. Most weather systems in the mid-latitudes are caused by instabilities of the jet stream flow (see baroclinic instability). Weather systems in the tropics are caused by different processes, such as monsoons or organized thunderstorm systems. Jet streams are fast flowing, relatively narrow air currents found in the atmosphere at around 12 km above the surface of the Earth, just under the tropopause. ... Baroclinic Instability is a fluid dynamic instability which helps to understand some important features of the so-called large scale waves in the mid-latitude atmosphere. ... A monsoon is a periodic wind, especially in the Indian Ocean and southern Asia. ...

Because the Earth's axis is tilted relative to its orbital plane, sunlight is incident at different angles at different times of the year. In June the Northern Hemisphere is tilted towards the sun, so at any given Northern Hemisphere latitude sunlight falls more directly on that spot than in December (see Effect of sun angle on climate). This effect causes seasons. Over thousands to hundreds of thousands of years, changes in Earth's orbital parameters affect the amount and distribution of solar energy received by the Earth and influence long-term climate (see Milankovitch cycles). The axis of rotation of a rotating body is a line such that the distance between any point on the line and any point of the body remains constant under the rotation. ... Prism splitting light Sunlight in the broad sense is the total spectrum of the electromagnetic radiation given off by the Sun. ... Figure 1 This is a diagram of the seasons. ... A season is one of the major divisions of the year, generally based on yearly periodic changes in weather. ... It has been suggested that Orbital forcing be merged into this article or section. ...

Terrestrial weather

Fair weather Cumulus clouds

On Earth, common weather phenomena include such things as wind, cloud, rain, snow, fog and dust storms. Less common events include natural disasters such as tornadoes, hurricanes and ice storms. Almost all familiar weather phenomena occur in the troposphere (the lower part of the atmosphere). Weather does occur in the stratosphere and can affect weather lower down in the troposphere, but the exact mechanisms are poorly understood ^[1]. Image File history File linksMetadata Download high resolution version (1225x919, 1016 KB) Super Color Cumulus Medows I, the creator of this work, hereby grant the permission to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1. ... Image File history File linksMetadata Download high resolution version (1225x919, 1016 KB) Super Color Cumulus Medows I, the creator of this work, hereby grant the permission to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1. ... Cumulus humilis, with cumulus congestus on the horizon Cumulus humilis (from L humilis, humble) is what is commonly referred to as fair weather cumulus. These clouds typically occur at 500 to 1000 metres altitude and rarely reach 2000 metres. ... Adjectives: Terrestrial, Terran, Telluric, Tellurian, Earthly Atmosphere Surface pressure: 101. ... A meteorological phenomenon is a weather event which can be explained by the principles of meteorology. ... Wind is the rough horizontal movement of air (as opposed to an air current) caused by uneven heating of the Earths surface. ... Cumulonimbus capillatus incus floating over Swifts Creek, Victoria in Australia A cloud is a visible mass of condensed droplets or frozen crystals suspended in the atmosphere above the surface of the Earth or another planetary body. ... For the singer, see Rain (singer). ... Animation of snowcover changing with the seasons. ... Evening fog obscures Londons Tower Bridge from passers by. ... Satellite photo of a Saharan dust cloud (2000) over the Eastern Atlantic Ocean. ... Natural Disasters is a young rap group made up of five young teens from the Chicago suburbs. ... For other uses of Tornado, see Tornado (disambiguation). ... This article is about weather phenomena. ... A typical view of a winter storm. ... Atmosphere diagram showing the mesosphere and other layers. ... Atmosphere diagram showing stratosphere. ...

The atmosphere is a chaotic system, so small changes to one part of the system can grow to have large effects on the system as a whole. This makes it difficult to accurately predict weather more than a few days in advance, though weather forecasters are continually working to extend this limit through the scientific study of weather, Meteorology. It is theoretically impossible to make useful day-to-day predictions more than about two weeks ahead, imposing an upper limit to potential for improved prediction skill.[1] Chaos theory says that the slightest variation in the motion of the air will grow with time. This idea is sometimes called the butterfly effect, from the idea that the motions caused by the flapping wings of a butterfly eventually could produce marked changes in the state of the atmosphere. Because of this sensitivity to small changes it will never be possible to make perfect forecasts, although there still is much potential for improvement. Layers of Atmosphere (NOAA) Air redirects here. ... A plot of the trajectory Lorenz system for values r = 28, σ = 10, b = 8/3 In mathematics and physics, chaos theory describes the behavior of certain nonlinear dynamical systems that under certain conditions exhibit a phenomenon known as chaos. ... Modern weather predictions aid in timely evacuations and potentially save lives and property damage Weather map of Europe, 10 December 1887 Weather forecasting is the application of current technology and science to predict the state of the atmosphere for a future time and a given location. ... Satellite image of Hurricane Hugo with a polar low visible at the top of the image. ... Point attractors in 2D phase space. ...

Shaping the planet

Weather is one of the fundamental processes that shape the Earth. The process of weathering breaks down rocks and soils into smaller fragments and then into their constituent substances. These are then free to take part in chemical reactions that can affect the surface further (e.g., acid rain) or are reformed into other rocks and soils. Weather also plays a major role in erosion of the surface. Weathering is the process of breaking down of rocks, soils and their minerals through direct, or indirect contact with the atmosphere. ... Acid rain (or more accurately acid precipitation)[1] occurs when sulfur dioxide and nitrogen oxides are emitted into the atmosphere, undergo chemical transformations and are absorbed by water droplets in clouds. ... Severe soil erosion in a wheat field near Washington State University, USA. For erosion as understood by materials science, see Erosion (materials science) For erosion as an English analogy, see Erosion (figurative) Erosion is the displacement of solids (soil, mud, rock and other particles) by the agents of wind, water...

Human history

Badly Flooded New Orleans after Hurricane Katrina.

Weather has played a large and sometimes direct part in human history. Aside from climatic changes that have caused the gradual drift of populations (for example the desertification of the Middle East, and the formation of land bridges during glacial periods), extreme weather events have caused smaller scale population movements and intruded directly in historical events. One such event is the saving of Japan from invasion by the Mongol fleet of Kublai Khan by the Kamikaze winds in 1281. A series of great storms throughout the 13th century caused the powerful English Cinque Ports to be silted up and hence lose their influence. More recently, Hurricane Katrina forced the temporary abandonment of the entire city of New Orleans in 2005. Image File history File linksMetadata Download high resolution version (2878x1850, 4497 KB) Summary From [1], an aerial view from a United States Navy helicopter showing floodwaters around the much of the New Orleans Central Business District in New Orleans. ... Image File history File linksMetadata Download high resolution version (2878x1850, 4497 KB) Summary From [1], an aerial view from a United States Navy helicopter showing floodwaters around the much of the New Orleans Central Business District in New Orleans. ... // The history of the world, by convention, is human history, from the first appearance of Homo sapiens to the present. ... Ship stranded by the retreat of the Aral Sea Desertification is the degradation of land in arid, semi arid and dry sub-humid areas resulting from various factors including climatic variations, but primarily human activities. ... A map showing countries commonly considered to be part of the Middle East The Middle East is a region comprising the lands around the southern and eastern parts of the Mediterranean Sea, a territory that extends from the eastern Mediterranean Sea to the Persian Gulf. ... A land bridge, in biogeography, is an isthmus or other land connection between what at other times are separate land masses which allows animals and plants to cross and colonise new lands. ... NOAA scientists observe severe weather using a mobile doppler radar and a helicopter (in the distance) Severe weather phenomena are weather conditions that are hazardous. ... Honorary guard of Mongolia. ... Qubilai Khan, Qubilai Khan or the last of the Great Khans (September 23, 1215 - February 18, 1294) (Mongolian: Хубилай хаан, Chinese: ; pinyin: ), was a Mongol military leader. ... Kamikaze (神風 kamikaze) is a Japanese word, usually translated as divine wind, beleived to be a gift from the gods. ... For broader historical context, see 1280s and 13th century. ... (12th century - 13th century - 14th century - other centuries) As a means of recording the passage of time, the 13th century was that century which lasted from 1201 to 1300. ... Flag of the Cinque Ports Formally, in Kent and Sussex there are five Head Ports making up the Confederation of the Cinque Ports, often pronounced as the anglicised sink ports, and meaning five ports (cinque in French means five and ports is to be connected to the Italian word porto... Lowest pressure 902 mbar (hPa; 26. ... New Orleans is the largest city in the state of Louisiana, United States of America. ... 2005 (MMV) was a common year starting on Saturday of the Gregorian calendar. ...

The effect of seasons on peoples' lives has long also caused them to observe and celebrate certain events during the calendar, some of which, in altered form, are still observed today. Christmas, for example, is the Yule of the pagans, celebrated around the winter solstice, the shortest day of the year (in the Northern Hemisphere, the summer solstice in the Southern Hemisphere). A page from the Hindu calendar 1871-72. ... Christmas or Christmas Day is an annual holiday that marks the traditional birthdate of Jesus of Nazareth. ... Yule is the winter solstice celebration of the Scandinavian Norse mythology and Germanic pagans. ... Pagans may mean: Paganism, a belief in natural religion. ... A solstice is either of the two events of the year when the sun is at its greatest distance from the equatorial plane. ...

Forecasting

Weather forecasting is the application of science and technology to predict the state of the atmosphere at a future time. Prior to the advent of scientific methods of weather forecasting, a large body of weather folklore developed to explain the weather. An example is the Groundhog Day celebration near the end of winter in parts of the United States and Canada. Today, weather forecasts are made by collecting data that describe the current state of the atmosphere (particularly the temperature, humidity and wind) and using physically-based mathematical models to determine how the atmosphere is expected to change in the future. The chaotic nature of the atmosphere means that perfect forecasts are impossible, and that forecasts become less accurate as the range of the forecast increases. Modern weather predictions aid in timely evacuations and potentially save lives and property damage Weather map of Europe, 10 December 1887 Weather forecasting is the application of current technology and science to predict the state of the atmosphere for a future time and a given location. ... Cumulus humilis indicates a good day ahead. ... Groundhog Day 2005 in Punxsutawney. ... An example of 500 mb geopotential height prediction from a numerical weather prediction model Numerical weather prediction is the science of predicting the weather using mathematical models of the atmosphere. ... A plot of the trajectory Lorenz system for values r = 28, σ = 10, b = 8/3 In mathematics and physics, chaos theory describes the behavior of certain nonlinear dynamical systems that under certain conditions exhibit a phenomenon known as chaos. ... Point attractors in 2D phase space. ...

Weather modification

Attempts to control the weather have been carried out for many years. The most common efforts to modify the weather involve cloud seeding to stimulate rainfall or suppress hail. The results of these efforts are mostly ambiguous. A tornado in central Oklahoma. ... Cessna 210 with cloud seeding equipment Cloud seeding, a form of weather modification, is the attempt to change the amount or type of precipitation that falls from clouds, by dispersing substances into the air that serve as cloud condensation or ice nuclei. ...

On a grander scale, science fiction authors have long posited the idea of terraforming other planets in order to make them habitable by human beings. While this may be possible in the distant future, this is far beyond current technology. Science fiction is a form of speculative fiction principally dealing with the impact of imagined science and technology, or both, upon society and persons as individuals. ... Artists conception of a terraformed Mars in four stages of development. ...

Extremes

The coldest air temperature ever recorded on Earth is -89.2°C (-127.8°F), at Vostok, Antarctica on 21 July 1983. The hottest air temperature ever recorded was 57.7°C (135.9°F), at Al 'Aziziyah, Libya, on 13 September 1922. The highest recorded average annual temperature was 34.4°C (94°F) at Dallol, Ethiopia. The coldest recorded average annual temperature is -50.6°C (-59°F) at Vostok, Antarctica; the coldest average annual temperature in a permanently inhabited location is at Resolute, Nunavut, in Canada. Ice cores drilled at Vostok, with a portion of the station behind Vostok Station (Russian: ) is a Russian (formerly Soviet) research station located near the South Geomagnetic Pole, at the center of the East Antarctic Ice Sheet. ... July 21 is the 202nd day (203rd in leap years) of the year in the Gregorian Calendar, with 163 days remaining. ... Al Aziziyah is one of the municipalities of Libya, located in the north of the country. ... September 13 is the 256th day of the year (257th in leap years). ... Dallol is a settlement in northern Ethiopia. ... Ice cores drilled at Vostok, with a portion of the station behind Vostok Station (Russian: ) is a Russian (formerly Soviet) research station located near the South Geomagnetic Pole, at the center of the East Antarctic Ice Sheet. ... Resolute (Qausuittuq) is a small town on Cornwallis Island in Nunavut, Canada, along the shore of Resolute Bay and the Northwest Passage. ...

Extra-terrestrial weather

Jupiter's Great Red Spot

Studying how the weather works on other planets has been seen as helpful in understanding how it works on Earth. ^[2] Weather on other planets follows many of the same physical principles as weather on Earth, but occurs on different scales and in atmospheres having different chemical composition. The Cassini-Huygens mission to Titan discovered clouds formed from methane or ethane which deposit rain composed of liquid methane and other organic compounds. Earth's atmosphere includes about six latitudinal circulation zones, three in each hemisphere (see Hadley cell). In contrast Jupiter's banded appearance shows over a dozen such zones, while Venus appears to have no zones at all. Download high resolution version (895x848, 52 KB)This dramatic view of Jupiters Great Red Spot and its surroundings was obtained by Voyager 1 on February 25, 1979, when the spacecraft was 5. ... Download high resolution version (895x848, 52 KB)This dramatic view of Jupiters Great Red Spot and its surroundings was obtained by Voyager 1 on February 25, 1979, when the spacecraft was 5. ... Cassini-Huygens is a joint NASA/ESA/ASI unmanned space mission intended to study Saturn and its moons. ... Titan (tye-tən, IPA: , Greek Τιτάν) or Saturn VI is the largest moon of Saturn and the second largest moon in the solar system,[3] after Jupiters moon Ganymede. ... Methane is a significant and plentiful fuel which is the principal component of natural gas. ... Benzene is the simplest of the arenes, a family of organic compounds An organic compound is any member of a large class of chemical compounds whose molecules contain carbon and hydrogen; therefore, carbides, carbonates, carbon oxides and elementary carbon are not organic (see below for more on the definition controversy... The Hadley cell is a circulation pattern that dominates the tropical atmosphere, with rising motion near the equator, poleward flow 10-15 kilometers above the surface, descending motion in the subtropics, and equatorward flow near the surface. ... (*min temperature refers to cloud tops only) Atmospheric characteristics Atmospheric pressure 9. ...

One of the most famous landmarks in the solar system, Jupiter's Great Red Spot, is an anticyclonic storm known to have existed for at least 300 years. On other gas giants the lack of a surface allows the wind to reach enormous speeds: gusts of up to 400 metres per second (about 1440 km/h / 900 mi/h) have been measured on the planet Neptune. This has created a puzzle for planetary scientists. The weather is ultimately created by solar energy and the amount of energy received by Neptune is only about 1/900th of that received by Earth, yet the intensity of weather phenomena on Neptune is far greater than on Earth. ^[3] Major features of the Solar System (not to scale, from left to right): Pluto, Neptune, Uranus, Saturn, a comet, Jupiter, Ceres which lies in the asteroid belt, the Sun, Mercury, Venus, Earth & Moon, and Mars. ... Atmospheric characteristics Atmospheric pressure 70 kPa Hydrogen ~86% Helium ~14% Methane 0. ... The Great Red Spot is a persistent anticyclonic storm on the planet Jupiter, 22° south of the equator, which has lasted at least 340 years. ... In meteorology, an anticyclone (i. ... The solar systems four gas giants against the Suns limb, to scale A gas giant (sometimes also known as a Jovian planet after the planet Jupiter) is a large planet that is not primarily composed of rock or other solid matter. ... Note: This article contains special characters. ... Planetary science, also known as planetology or planetary astronomy, is the science of planets, or planetary systems, and the solar system. ...

Extra-planetary weather

Aurora Borealis

Weather is not limited to planetary bodies. A star's corona is constantly being lost to space, creating what is essentially a very thin atmosphere throughout the solar system. The movement of mass ejected from the Sun is known as the solar wind. Image File history File links Polarlicht. ... Image File history File links Polarlicht. ... In astronomy, a corona is the luminous plasma atmosphere of the Sun or other celestial body, extending millions of kilometres into space, most easily seen during a total solar eclipse, but also observable in a coronagraph. ... Major features of the Solar System (not to scale, from left to right): Pluto, Neptune, Uranus, Saturn, a comet, Jupiter, Ceres which lies in the asteroid belt, the Sun, Mercury, Venus, Earth & Moon, and Mars. ... The plasma in the solar wind meeting the heliopause For the British comic, see Solar Wind (comic). ...

Inconsistencies in this wind and larger events on the surface of the star, such as coronal mass ejections, form a system that has features analogous to conventional weather systems (such as pressure and wind) and is generally known as space weather. The activity of this system can affect planetary atmospheres and occasionally surfaces. The interaction of the solar wind with the terrestrial atmosphere can produce spectacular aurorae, and can play havoc with electrically sensitive systems such as electricity grids and radio signals. A composite image showing two CMEs (at 2 oclock and 8 oclock), with the sun at center. ... Aurora australis observed by Discovery, May 1991. ... View of Jupiters active atmosphere, including the Great Red Spot. ... The plasma in the solar wind meeting the heliopause For the British comic, see Solar Wind (comic). ... Aurora borealis Aurora borealis The aurora is a glow observed in the night sky, usually in the polar zone. ... Power line redirects here. ...

Aurora australis

Image File history File links Download high resolution version (5109x1200, 412 KB) Aurora Australis appearing in the night sky (10:50 pm Australian time (GMT = 8:50 am) at Swifts Creek, 100km north of Lakes Entrance, Victoria, Australia. ... Image File history File links Download high resolution version (5109x1200, 412 KB) Aurora Australis appearing in the night sky (10:50 pm Australian time (GMT = 8:50 am) at Swifts Creek, 100km north of Lakes Entrance, Victoria, Australia. ...

References

Aerial view of Goddard Space Flight Center. ... Space. ...

See also

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