Editing Meteorology (section)

===Numerical weather prediction===
{{Main|Numerical weather prediction}}
[[File:IBM 7090 console used by a meteorologist, 1965.jpg|thumb|left|A meteorologist at the console of the IBM 7090 in the Joint Numerical Weather Prediction Unit, {{Circa|1965}}]]

In 1904, Norwegian scientist [[Vilhelm Bjerknes]] first argued in his paper ''Weather Forecasting as a Problem in Mechanics and Physics'' that it should be possible to forecast weather from calculations based upon [[physical law|natural laws]].<ref>Berknes, V. (1904) "Das Problem der Wettervorhersage, betrachtet vom Standpunkte der Mechanik und der Physik" (The problem of weather prediction, considered from the viewpoints of mechanics and physics), ''Meteorologische Zeitschrift'', '''21''' : 1–7.  Available in English on-line at:  [http://www.schweizerbart.de/resources/downloads/paper_free/74383.pdf Schweizerbart science publishers] {{Webarchive|url=https://web.archive.org/web/20180411175033/http://www.schweizerbart.de/resources/downloads/paper_free/74383.pdf |date=11 April 2018 }}.</ref><ref>{{cite web |url=http://docs.lib.noaa.gov/rescue/Bibliographies/Bjerknes/Bjerknes_July_2004.pdf |title=Pioneers in Modern Meteorology and Climatology: Vilhelm and Jacob Bjerknes |access-date=13 October 2008 |archive-date=21 November 2017 |archive-url=https://web.archive.org/web/20171121091141/https://docs.lib.noaa.gov/rescue/Bibliographies/Bjerknes/Bjerknes_July_2004.pdf |url-status=live }}</ref>

It was not until later in the 20th century that advances in the understanding of atmospheric physics led to the foundation of modern [[numerical weather prediction]]. In 1922, [[Lewis Fry Richardson]] published "Weather Prediction By Numerical Process,"<ref>Richardson, Lewis Fry, ''Weather Prediction by Numerical Process'' (Cambridge, England:  Cambridge University Press, 1922).  Available on-line at:  [https://archive.org/stream/weatherpredictio00richrich#page/n7/mode/2up Internet Archive.org].</ref> after finding notes and derivations he worked on as an ambulance driver in World War I. He described how small terms in the prognostic fluid dynamics equations that govern atmospheric flow could be neglected, and a numerical calculation scheme that could be devised to allow predictions. Richardson envisioned a large auditorium of thousands of people performing the calculations. However, the sheer number of calculations required was too large to complete without electronic computers, and the size of the grid and time steps used in the calculations led to unrealistic results. Though numerical analysis later found that this was due to [[numerical instability]].

Starting in the 1950s, [[number|numerical]] forecasts with computers became feasible.<ref>{{cite web|last=Edwards |first=Paul N. |publisher=[[American Institute of Physics]] |website=aip.org |url=http://www.aip.org/history/sloan/gcm/ |title=Atmospheric General Circulation Modeling |archive-url=https://web.archive.org/web/20080325084036/http://www.aip.org/history/sloan/gcm/ |archive-date=25 March 2008 |url-status=dead |access-date=13 January 2008}}</ref> The first [[weather forecast]]s derived this way used [[barotropic]] (single-vertical-level) models, and could successfully predict the large-scale movement of midlatitude [[Rossby wave]]s, that is, the pattern of [[low-pressure area|atmospheric lows]] and [[High-pressure area|highs]].<ref>{{cite book |title=Storm Watchers |page=[https://archive.org/details/stormwatcherstur00cox_df1/page/208 208] |year=2002 |author=Cox, John D. |publisher=John Wiley & Sons, Inc. |isbn=978-0-471-38108-2 |url=https://archive.org/details/stormwatcherstur00cox_df1/page/208 }}</ref> In 1959, the UK Meteorological Office received its first computer, a [[Ferranti Mercury]].<ref>{{Cite web|url=https://www.metoffice.gov.uk/research/modelling-systems/history-of-numerical-weather-prediction|title=The history of Numerical Weather Prediction at the Met Office|website=Met Office|access-date=15 January 2018|archive-date=15 January 2018|archive-url=https://web.archive.org/web/20180115185643/https://www.metoffice.gov.uk/research/modelling-systems/history-of-numerical-weather-prediction|url-status=dead}}</ref>

In the 1960s, the [[Chaos theory|chaotic]] nature of the atmosphere was first observed and mathematically described by [[Edward Lorenz]], founding the field of [[chaos theory]].<ref>Edward N. Lorenz, "Deterministic non-periodic flow", ''Journal of the Atmospheric Sciences'', vol.&nbsp;20, pages 130–141 (1963).</ref> These advances have led to the current use of [[ensemble forecasting]] in most major forecasting centers, to take into account uncertainty arising from the chaotic nature of the atmosphere.<ref name="HPCens">{{cite web |url=http://www.wpc.ncep.noaa.gov/ensembletraining |author=Manousos, Peter |publisher=[[Hydrometeorological Prediction Center]] |date=19 July 2006 |access-date=31 December 2010 |title=Ensemble Prediction Systems |archive-date=8 April 2019 |archive-url=https://web.archive.org/web/20190408081534/https://www.wpc.ncep.noaa.gov/ensembletraining/ |url-status=live }}</ref> Mathematical models used to predict the long term weather of the Earth ([[climate model]]s), have been developed that have a resolution today that are as coarse as the older weather prediction models. These climate models are used to investigate long-term [[climate]] shifts, such as what effects might be caused by human emission of [[greenhouse gas]]es.