Editing Weather (section)

{{Short description|Short-term state of the atmosphere}}
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{{About|the atmospheric process|the geological process|Weathering|other uses|Weather (disambiguation)|and|Weather systems (disambiguation)}}
{{redirect|Fair weather|other uses|Fairweather (disambiguation)}}
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[[File:Port and lighthouse overnight storm with lightning in Port-la-Nouvelle.jpg|thumb|upright=1.35|Thunderstorm near Port-la-Nouvelle, [[France]]]]

{{Weather}}

'''Weather''' is the state of the [[atmosphere]], describing for example the degree to which it is hot or cold, wet or dry, calm or stormy, clear or [[cloud cover|cloudy]].<ref>"[http://www.merriam-webster.com/dictionary/weather Weather.]" ''Merriam-Webster Dictionary''. {{Webarchive|url=https://web.archive.org/web/20170709032002/https://www.merriam-webster.com/dictionary/weather |date=9 July 2017}} Retrieved on 27 June 2008.</ref> On [[Earth]], most weather phenomena occur in the lowest layer of the planet's [[atmosphere of Earth|atmosphere]], the [[troposphere]],<ref>{{cite web |website=Glossary of Meteorology |url=http://amsglossary.allenpress.com/glossary/search?p=1&query=hydrosphere&submit=Search |title=Hydrosphere |archive-url=https://web.archive.org/web/20120315161323/http://amsglossary.allenpress.com/glossary/search?p=1&query=hydrosphere&submit=Search |archive-date=15 March 2012 |access-date=27 June 2008}}</ref><ref name=":0">{{Cite web |title=Troposphere|url=http://amsglossary.allenpress.com/glossary/browse?s=t&p=51|archive-url=https://web.archive.org/web/20120928061111/http://amsglossary.allenpress.com/glossary/browse?s=t&p=51|url-status=dead|archive-date=2012-09-28|access-date=2020-10-11|website=Glossary of Meteorology}}</ref> just below the [[stratosphere]]. Weather refers to day-to-day temperature, [[precipitation]], and other atmospheric conditions, whereas [[climate]] is the term for the averaging of atmospheric conditions over longer periods of time.<ref>{{cite encyclopedia | title = Climate | encyclopedia = Glossary of Meteorology | publisher = [[American Meteorological Society]] | url = http://amsglossary.allenpress.com/glossary/search?id=climate1 | access-date = 14 May 2008 | archive-date = 7 July 2011 | archive-url = https://web.archive.org/web/20110707113544/http://amsglossary.allenpress.com/glossary/search?id=climate1 | url-status = dead }}</ref> When used without qualification, "weather" is generally understood to mean the weather of Earth.

Weather is driven by [[atmospheric pressure|air pressure]], [[temperature]], and [[moisture]] differences between one place and another. These differences can occur due to the [[effect of Sun angle on climate|Sun's angle]] at any particular spot, which varies with [[latitude]]. The strong temperature contrast between polar and tropical air gives rise to the largest scale [[atmospheric circulation]]s: the [[Hadley cell]], the [[Ferrel cell]], the [[polar cells|polar cell]], and the [[jet stream]]. Weather systems in the [[middle latitudes]], such as [[extratropical cyclone]]s, are caused by instabilities of the jet streamflow.  Because Earth's [[axial tilt|axis is tilted]] relative to its [[orbital plane (astronomy)|orbital plane]] (called the [[ecliptic]]), [[sunlight]] is incident at [[Angle of incidence (optics)|different angles]] at different times of the year. On Earth's surface, temperatures usually range ±40&nbsp;°C (−40&nbsp;°F to 104&nbsp;°F) annually. Over thousands of years, changes in Earth's [[orbit]] can affect the amount and distribution of [[solar energy]] received by Earth, thus influencing long-term climate and global [[Climate variability and change|climate change]].

Surface temperature differences in turn cause pressure differences. Higher altitudes are cooler than lower altitudes, as most atmospheric heating is due to contact with the Earth's surface while radiative losses to space are mostly constant. [[Weather forecasting]] is the application of science and technology to predict the state of the [[Earth's atmosphere|atmosphere]] for a future time and a given location. Earth's weather system is a [[chaos theory|chaotic system]]; as a result, small changes to one part of the system can grow to have large effects on the system as a whole. Human attempts to [[weather control|control the weather]] have occurred throughout history, and there is evidence that [[human impact on the environment|human activities]] such as agriculture and industry have modified weather patterns.

Studying how the weather works on other planets has been helpful in understanding how weather works on Earth. A famous landmark in the [[Solar System]], Jupiter's [[Great Red Spot]], is an [[anticyclonic storm]] known to have existed for at least 300 years. However, the weather is not limited to planetary bodies. A [[stellar corona|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]].