Editing Monsoon (section)

== Process ==
Monsoons were once considered as a large-scale [[sea breeze]]<ref>{{cite web|url=http://www.thefreedictionary.com/sea+breeze|title=Sea breeze – definition of sea breeze by The Free Dictionary|work=TheFreeDictionary.com}}</ref> caused by higher temperature over land than in the ocean. This is no longer considered as the cause and the monsoon is now considered a planetary-scale phenomenon involving the annual migration of the Intertropical Convergence Zone between its northern and southern limits. The limits of the ITCZ vary according to the land–sea heating contrast and it is thought that the northern extent of the monsoon in South Asia is influenced by the high Tibetan Plateau.<ref>{{Cite journal|last=Gadgil|first=Sulochana|date=2018|title=The monsoon system: Land–sea breeze or the ITCZ?|journal=Journal of Earth System Science|language=en|volume=127|issue=1|pages=1|doi=10.1007/s12040-017-0916-x|issn=0253-4126|doi-access=free}}</ref><ref>{{Cite journal|last=Chou|first=C.|date=2003|title=Land-sea heating contrast in an idealized Asian summer monsoon|url=|journal=Climate Dynamics|volume=21|issue=1|pages=11–25|doi=10.1007/s00382-003-0315-7|bibcode=2003ClDy...21...11C|s2cid=53701462|issn=0930-7575}}</ref> These temperature imbalances happen because oceans and land absorb heat in different ways. Over oceans, the air temperature remains relatively stable for two reasons: water has a relatively high [[heat capacity]] (3.9 to 4.2 J g<sup>−1</sup> K<sup>−1</sup>),<ref>{{cite web|url=http://www.engineeringtoolbox.com/specific-heat-fluids-d_151.html|title=Liquids and Fluids – Specific Heats|url-status=dead|archive-url=https://web.archive.org/web/20070809075541/http://www.engineeringtoolbox.com/specific-heat-fluids-d_151.html|archive-date=2007-08-09|access-date=2012-10-01}}</ref> and because both [[conduction (heat)|conduction]] and [[Convection (heat transfer)|convection]] will equilibrate a hot or cold surface with deeper water (up to 50 metres). In contrast, dirt, sand, and rocks have lower heat capacities (0.19 to 0.35 J g<sup>−1</sup> K<sup>−1</sup>),<ref>{{cite web|url=http://www.engineeringtoolbox.com/specific-heat-solids-d_154.html|title=Solids – Specific Heats|url-status=dead|archive-url=https://web.archive.org/web/20120922143033/http://www.engineeringtoolbox.com/specific-heat-solids-d_154.html|archive-date=2012-09-22|access-date=2012-10-01}}</ref> and they can only transmit heat into the earth by conduction and not by convection. Therefore, bodies of water stay at a more even temperature, while land temperatures are more variable.

During warmer months sunlight heats the surfaces of both land and oceans, but land temperatures rise more quickly. As the land's surface becomes warmer, the air above it expands and an area of [[thermal low|low pressure]] develops. Meanwhile, the ocean remains at a lower temperature than the land, and the air above it retains a higher pressure. This difference in pressure causes [[sea breeze]]s to blow from the ocean to the land, bringing moist air inland. This moist air rises to a higher altitude over land and then it flows back toward the ocean (thus completing the cycle). However, when the air rises, and while it is still over the land, the air [[Joule–Thomson effect|cools]]. This decreases the air's [[relative humidity|ability to hold water]], and this causes [[precipitation]] over the land. This is why summer monsoons cause so much rain over land.

In the colder months, the cycle is reversed. Then the land cools faster than the oceans and the air over the land has higher pressure than air over the ocean. This causes the air over the land to flow to the ocean. When humid air rises over the ocean, it cools, and this causes precipitation over the oceans. (The cool air then flows towards the land to complete the cycle.)

Most summer monsoons have a dominant westerly component and a strong tendency to ascend and produce copious amounts of rain (because of the condensation of water vapor in the rising air). The intensity and duration, however, are not uniform from year to year. Winter monsoons, by contrast, have a dominant easterly component and a strong tendency to diverge, subside and cause drought.<ref>{{cite encyclopedia|title= Monsoon|encyclopedia= Britannica|url= https://www.britannica.com/eb/article-9053445/monsoon|access-date= 2007-05-15|url-status= live|archive-url= https://web.archive.org/web/20071013114728/https://www.britannica.com/eb/article-9053445/monsoon|archive-date= 2007-10-13}}</ref>

Similar rainfall is caused when moist ocean air is lifted upwards by mountains,<ref name="MT">Dr. Michael Pidwirny (2008). [http://www.physicalgeography.net/fundamentals/8e.html CHAPTER 8: Introduction to the Hydrosphere (e). Cloud Formation Processes.] {{webarchive|url=https://web.archive.org/web/20081220230524/http://www.physicalgeography.net/fundamentals/8e.html |date=2008-12-20 }} Physical Geography. Retrieved on 2009-01-01.</ref> surface heating,<ref>Bart van den Hurk and Eleanor Blyth (2008). [http://www.knmi.nl/~hurkvd/Loco_workshop/Workshop_report.pdf Global maps of Local Land–Atmosphere coupling.] {{webarchive|url=https://web.archive.org/web/20090225074154/http://www.knmi.nl/~hurkvd/Loco_workshop/Workshop_report.pdf |date=2009-02-25 }} KNMI. Retrieved on 2009-01-02.</ref> convergence at the surface,<ref>Robert Penrose Pearce (2002). [https://books.google.com/books?id=QECy_UBdyrcC&dq=ways+to+moisten+the+atmosphere&pg=PA66 Meteorology at the Millennium.] {{webarchive|url=https://web.archive.org/web/20160427120249/https://books.google.com/books?id=QECy_UBdyrcC&pg=PA66&lpg=PA66&dq=ways+to+moisten+the+atmosphere&source=web&ots=-0MYq5qyS6&sig=gz5lOAPIc54v5qfO7nZ098KmVGE&hl=en&sa=X&oi=book_result&resnum=6&ct=result |date=2016-04-27 }} Academic Press, p. 66. {{ISBN|978-0-12-548035-2}}. Retrieved on 2009-01-02.</ref> divergence aloft, or from storm-produced outflows at the surface.<ref>{{cite web|author=Glossary of Meteorology|date=June 2000|publisher=[[American Meteorological Society]]|url=http://amsglossary.allenpress.com/glossary/search?p=1&query=gust+front&submit=Search|title=Gust Front|access-date=2008-07-09|url-status=dead|archive-url=https://web.archive.org/web/20110505002722/http://amsglossary.allenpress.com/glossary/search?p=1&query=gust+front&submit=Search|archive-date=2011-05-05}}</ref> However the lifting occurs, the air cools due to expansion in lower pressure, and this produces [[condensation]].