Monsoon (/mɒnˈsuːn/) is traditionally defined as a seasonal reversing wind accompanied by corresponding changes in precipitation,[1] but is now used to describe seasonal changes in atmospheric circulation and precipitation associated with the asymmetric heating of land and sea.[2][3] Usually, the term monsoon is used to refer to the rainy phase of a seasonally changing pattern, although technically there is also a dry phase. The term is sometimes incorrectly used for locally heavy but short-term rains,[4] although these rains meet the dictionary definition of monsoon.[5]

The major monsoon systems of the world consist of the West African and Asia-Australian monsoons. The inclusion of the North and South American monsoons with incomplete wind reversal has been debated.[6]

The term was first used in English in British India and neighbouring countries to refer to the big seasonal winds blowing from the Bay of Bengal and Arabian Sea in the southwest bringing heavy rainfall to the area.[7][8]

Monsoon clouds near Nagercoil
Advancing monsoon clouds and showers in Aralvaimozhy, near Nagercoil, India


Monsoon clouds Lucknow
Monsoon clouds over Lucknow, Uttar Pradesh

The English monsoon came from Portuguese monção, ultimately from Arabic mawsim (موسم "season"), "perhaps partly via early modern Dutch monson."[9]


Strengthening of the Asian monsoon has been linked to the uplift of the Tibetan Plateau after the collision of the Indian sub-continent and Asia around 50 million years ago.[10] Because of studies of records from the Arabian Sea and that of the wind-blown dust in the Loess Plateau of China, many geologists believe the monsoon first became strong around 8 million years ago. More recently, studies of plant fossils in China and new long-duration sediment records from the South China Sea led to a timing of the monsoon beginning 15–20 million years ago and linked to early Tibetan uplift.[11] Testing of this hypothesis awaits deep ocean sampling by the Integrated Ocean Drilling Program.[12] The monsoon has varied significantly in strength since this time, largely linked to global climate change, especially the cycle of the Pleistocene ice ages.[13] A study of marine plankton suggested that the Indian Monsoon strengthened around 5 million years ago. Then, during ice periods, the sea level fell and the Indonesian Seaway closed. When this happened, cold waters in the Pacific were impeded from flowing into the Indian Ocean. It is believed that the resulting increase in sea surface temperatures in the Indian Ocean increased the intensity of monsoons.[14]

Five episodes during the Quaternary at 2.22 Ma (PL-1), 1.83 Ma (PL-2), 0.68 Ma (PL-3), 0.45 Ma (PL-4) and 0.04 Ma (PL-5) were identified which showed a weakening of Leeuwin Current (LC). The weakening of the LC would have an effect on the sea surface temperature (SST) field in the Indian Ocean, as the Indonesian through flow generally warms the Indian Ocean. Thus these five intervals could probably be those of considerable lowering of SST in the Indian Ocean and would have influenced Indian monsoon intensity. During the weak LC, there is the possibility of reduced intensity of the Indian winter monsoon and strong summer monsoon, because of change in the Indian Ocean dipole due to reduction in net heat input to the Indian Ocean through the Indonesian through flow. Thus a better understanding of the possible links between El Niño, Western Pacific Warm Pool, Indonesian Throughflow, wind pattern off western Australia, and ice volume expansion and contraction can be obtained by studying the behaviour of the LC during Quaternary at close stratigraphic intervals.[15]

Strength of impact

On May 28, in the dry season
On August 28, in the rainy season
This visualization shows the Asian monsoon and how it develops using observational and modeled data. It also shows some of the impacts.

The impact of monsoon on the local weather is different from place to place. In some places there is just a likelihood of having a little more or less rain. In other places, quasi semi-deserts are turned into vivid green grasslands where all sorts of plants and crops can flourish.

The Indian Monsoon turns large parts of India from a kind of semi-desert into green lands. See photos only taken 3 months apart in the Western Ghats. In places like this it is crucial for farmers to have the right timing for putting the seeds on the fields, as it is essential to use all the rain that is available for growing crops.


Monsoons are large-scale sea breezes [16] which occur when the temperature on land is significantly warmer or cooler than the temperature of the ocean. 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−1 K−1),[17] and because both conduction and 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−1 K−1),[18] 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 temperature 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 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 breezes 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 cools. This decreases the air's 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.[19]

Similar rainfall is caused when moist ocean air is lifted upwards by mountains,[20] surface heating,[21] convergence at the surface,[22] divergence aloft, or from storm-produced outflows at the surface.[23] However the lifting occurs, the air cools due to expansion in lower pressure, and this produces condensation.

Global monsoon

Summary table

Location Monsoon/sub-system Average date of arrival Average date of withdrawal Notes
Northern Mexico North American/Gulf of California-Southwest USA late May[24] September incomplete wind reversal, waves
Tucson, Arizona North American/Gulf of California-Southwest USA early July[24] September incomplete wind reversal, waves
Central America Central/South American Monsoon April[25] October[25] true monsoon
Amazon Brazil South American monsoon September[25] May[25]
Southeast Brazil South American monsoon November[25] March[25]
West Africa West African June 22[26] Sept[27] /October[26] waves
Southeast Africa Southeast Africa monsoon w/ Harmattan Jan[27] March[27]
Kelantan, Malaysia Indo-Australian/Borneo-Australian October March
Phuket, Thailand Indo-Australian February/March December
Bangkok, Thailand Indo-Australian/Indian-Indochina April–May October/November persistent
Yangon, Myanmar Indo-Australian/Indian-Indochina May 25[28] Nov 1[28]
Colombo, Sri Lanka Indo-Australian May 25[28] Dec 15[28] persistent
Kerala, India Indian monsoon Jun 1[28] Dec 1[28] persistent
Jakarta, Indonesia Indo-Australian/Borneo-Australian November March abrupt
Lahore, Pakistan Indian monsoon late July[28] Sep 1[28]
Dhaka, Bangladesh Indo-Australian/Indian-Indochina mid-June October abrupt
Cebu, Philippines Indo-Australian/Borneo-Australian October March abrupt
Kaohsiung, Taiwan East Asian monsoon May 10[28]
Taipei, Taiwan East Asian monsoon May 20[28]
Kagoshima, Japan East Asian monsoon Jun 10[28]
Seoul, Korea East Asian monsoon July 10[28]
Hanoi, Vietnam East Asian monsoon May 20[28]
Beijing, China East Asian monsoon July 20[28]
Karachi, Pakistan Indian monsoon July 15[28] August[28]
Mumbai, India Indian monsoon July 10[28] Oct 1[28]
Darwin, Australia Australian monsoon Oct[27] April[27]

Africa (West African and Southeast African)

Saison des pluies à Mayotte
Southeast African moonsoon clouds, over Mayotte island.

The monsoon of western Sub-Saharan Africa is the result of the seasonal shifts of the Intertropical Convergence Zone and the great seasonal temperature and humidity differences between the Sahara and the equatorial Atlantic Ocean.[29] It migrates northward from the equatorial Atlantic in February, reaches western Africa on or near June 22, then moves back to the south by October.[26] The dry, northeasterly trade winds, and their more extreme form, the harmattan, are interrupted by the northern shift in the ITCZ and resultant southerly, rain-bearing winds during the summer. The semiarid Sahel and Sudan depend upon this pattern for most of their precipitation.

North America

Incoming monsoon clouds over Arizona
Incoming monsoon clouds over Phoenix, Arizona
Three-second video of a lightning strike within a thunderstorm over Island in the Sky, Canyonlands National Park

The North American monsoon (NAM) occurs from late June or early July into September, originating over Mexico and spreading into the southwest United States by mid-July. It affects Mexico along the Sierra Madre Occidental as well as Arizona, New Mexico, Nevada, Utah, Colorado, West Texas and California. It pushes as far west as the Peninsular Ranges and Transverse Ranges of Southern California, but rarely reaches the coastal strip (a wall of desert thunderstorms only a half-hour's drive away is a common summer sight from the sunny skies along the coast during the monsoon). The North American monsoon is known to many as the Summer, Southwest, Mexican or Arizona monsoon.[30][31] It is also sometimes called the Desert monsoon as a large part of the affected area are the Mojave and Sonoran deserts. However, it is debatable whether the North and South American weather patterns with incomplete wind reversal should be counted as true monsoons.[6]


The Asian monsoons may be classified into a few sub-systems, such as the Indian Subcontinental Monsoon which affects the Indian subcontinent and surrounding regions including Nepal, and the East Asian Monsoon which affects southern China, Taiwan, Korea and parts of Japan.

South Asian monsoon

India southwest summer monsoon onset map en
Onset dates and prevailing wind currents of the southwest summer monsoons in India

The southwestern summer monsoons occur from July through September. The Thar Desert and adjoining areas of the northern and central Indian subcontinent heat up considerably during the hot summers. This causes a low pressure area over the northern and central Indian subcontinent. To fill this void, the moisture-laden winds from the Indian Ocean rush into the subcontinent. These winds, rich in moisture, are drawn towards the Himalayas. The Himalayas act like a high wall, blocking the winds from passing into Central Asia, and forcing them to rise. As the clouds rise, their temperature drops, and precipitation occurs. Some areas of the subcontinent receive up to 10,000 mm (390 in) of rain annually.

The southwest monsoon is generally expected to begin around the beginning of June and fade away by the end of September. The moisture-laden winds on reaching the southernmost point of the Indian Peninsula, due to its topography, become divided into two parts: the Arabian Sea Branch and the Bay of Bengal Branch.

The Arabian Sea Branch of the Southwest Monsoon first hits the Western Ghats of the coastal state of Kerala, India, thus making this area the first state in India to receive rain from the Southwest Monsoon. This branch of the monsoon moves northwards along the Western Ghats (Konkan and Goa) with precipitation on coastal areas, west of the Western Ghats. The eastern areas of the Western Ghats do not receive much rain from this monsoon as the wind does not cross the Western Ghats.

The Bay of Bengal Branch of Southwest Monsoon flows over the Bay of Bengal heading towards North-East India and Bengal, picking up more moisture from the Bay of Bengal. The winds arrive at the Eastern Himalayas with large amounts of rain. Mawsynram, situated on the southern slopes of the Khasi Hills in Meghalaya, India, is one of the wettest places on Earth. After the arrival at the Eastern Himalayas, the winds turns towards the west, travelling over the Indo-Gangetic Plain at a rate of roughly 1–2 weeks per state,[32] pouring rain all along its way. June 1 is regarded as the date of onset of the monsoon in India, as indicated by the arrival of the monsoon in the southernmost state of Kerala.

The monsoon accounts for nearly 80% of the rainfall in India.[33][34] Indian agriculture (which accounts for 25% of the GDP and employs 70% of the population) is heavily dependent on the rains, for growing crops especially like cotton, rice, oilseeds and coarse grains. A delay of a few days in the arrival of the monsoon can badly affect the economy, as evidenced in the numerous droughts in India in the 1990s.

The monsoon is widely welcomed and appreciated by city-dwellers as well, for it provides relief from the climax of summer heat in June.[35] However, the roads take a battering every year. Often houses and streets are waterlogged and slums are flooded despite drainage systems. A lack of city infrastructure coupled with changing climate patterns causes severe economic loss including damage to property and loss of lives, as evidenced in the 2005 flooding in Mumbai that brought the city to a standstill. Bangladesh and certain regions of India like Assam and West Bengal, also frequently experience heavy floods during this season. Recently, areas in India that used to receive scanty rainfall throughout the year, like the Thar Desert, have surprisingly ended up receiving floods due to the prolonged monsoon season.

The influence of the Southwest Monsoon is felt as far north as in China's Xinjiang. It is estimated that about 70% of all precipitation in the central part of the Tian Shan Mountains falls during the three summer months, when the region is under the monsoon influence; about 70% of that is directly of "cyclonic" (i.e., monsoon-driven) origin (as opposed to "local convection").[36]

Heavy clouds over Salt Lake, Calcutta
Monsoon clouds in Kolkata

Around September, with the sun fast retreating south, the northern land mass of the Indian subcontinent begins to cool off rapidly. With this air pressure begins to build over northern India, the Indian Ocean and its surrounding atmosphere still holds its heat. This causes cold wind to sweep down from the Himalayas and Indo-Gangetic Plain towards the vast spans of the Indian Ocean south of the Deccan peninsula. This is known as the Northeast Monsoon or Retreating Monsoon.

While travelling towards the Indian Ocean, the dry cold wind picks up some moisture from the Bay of Bengal and pours it over peninsular India and parts of Sri Lanka. Cities like Chennai, which get less rain from the Southwest Monsoon, receive rain from this Monsoon. About 50% to 60% of the rain received by the state of Tamil Nadu is from the Northeast Monsoon.[37] In Southern Asia, the northeastern monsoons take place from October to December when the surface high-pressure system is strongest.[38] The jet stream in this region splits into the southern subtropical jet and the polar jet. The subtropical flow directs northeasterly winds to blow across southern Asia, creating dry air streams which produce clear skies over India. Meanwhile, a low pressure system known as a monsoon trough develops over South-East Asia and Australasia and winds are directed toward Australia.

East Asian Monsoon

The East Asian monsoon affects large parts of Indo-China, Philippines, China, Taiwan, Korea and Japan. It is characterised by a warm, rainy summer monsoon and a cold, dry winter monsoon. The rain occurs in a concentrated belt that stretches east-west except in East China where it is tilted east-northeast over Korea and Japan. The seasonal rain is known as Meiyu in China, Jangma in Korea, and Bai-u in Japan, with the latter two resembling frontal rain.

The onset of the summer monsoon is marked by a period of premonsoonal rain over South China and Taiwan in early May. From May through August, the summer monsoon shifts through a series of dry and rainy phases as the rain belt moves northward, beginning over Indochina and the South China Sea (May), to the Yangtze River Basin and Japan (June) and finally to North China and Korea (July). When the monsoon ends in August, the rain belt moves back to South China.


Evening monsoonal squall
Monsoonal squall nears Darwin, Northern Territory, Australia

Also known as the Indo-Australian Monsoon. The rainy season occurs from September to February and it is a major source of energy for the Hadley circulation during boreal winter. The Maritime Continent Monsoon and the Australian Monsoon may be considered to be the same system, the Indo-Australian Monsoon.

It is associated with the development of the Siberian High and the movement of the heating maxima from the Northern Hemisphere to the Southern Hemisphere. North-easterly winds flow down Southeast Asia, are turned north-westerly/westerly by Borneo topography towards Australia. This forms a cyclonic circulation vortex over Borneo, which together with descending cold surges of winter air from higher latitudes, cause significant weather phenomena in the region. Examples are the formation of a rare low-latitude tropical storm in 2001, Tropical Storm Vamei, and the devastating flood of Jakarta in 2007.

The onset of the monsoon over the Maritime Continent tends to follow the heating maxima down Vietnam and the Malay Peninsula (September), to Sumatra, Borneo and the Philippines (October), to Java, Sulawesi (November), Irian Jaya and Northern Australia (December, January). However, the monsoon is not a simple response to heating but a more complex interaction of topography, wind and sea, as demonstrated by its abrupt rather than gradual withdrawal from the region. The Australian monsoon (the "Wet") occurs in the southern summer when the monsoon trough develops over Northern Australia. Over three-quarters of annual rainfall in Northern Australia falls during this time.


The European Monsoon (more commonly known as the return of the westerlies) is the result of a resurgence of westerly winds from the Atlantic, where they become loaded with wind and rain.[39] These westerly winds are a common phenomenon during the European winter, but they ease as spring approaches in late March and through April and May. The winds pick up again in June, which is why this phenomenon is also referred to as "the return of the westerlies".[40]

The rain usually arrives in two waves, at the beginning of June and again in mid- to late June. The European monsoon is not a monsoon in the traditional sense in that it doesn't meet all the requirements to be classified as such. Instead the return of the westerlies is more regarded as a conveyor belt that delivers a series of low pressure centres to Western Europe where they create unsettled weather. These storms generally feature significantly lower than average temperatures, fierce rain or hail, thunder and strong winds.[41]

The return of the westerlies affects Europe's Northern Atlantic coastline, more precisely Ireland, Great Britain, the Benelux countries, Western Germany, Northern France and parts of Scandinavia.

See also


  1. ^ Ramage, C. (1971). Monsoon Meteorology. International Geophysics Series. 15. San Diego, CA: Academic Press.
  2. ^ Trenberth, K. E.; Stepaniak, D. P.; Caron, J. M. (2000). "The Global Monsoon as Seen through the Divergent Atmospheric Circulation". Journal of Climate. 13 (22): 3969–3993. doi:10.1175/1520-0442(2000)013<3969:TGMAST>2.0.CO;2.
  3. ^ Zuidema, P.; Fairall, C.; Hartten, L. M.; Hare, J. E.; Wolfe, D. (2007). "On Air–Sea Interaction at the Mouth of the Gulf of California". Journal of Climate. 20 (9): 1649–1661. doi:10.1175/JCLI4089.1.
  4. ^ "Welcome to Monsoon Season – Why You Probably Are Using This Term Wrong". 29 June 2016. Archived from the original on 30 June 2016.
  5. ^ "Definition of Monsoon". 28 July 2016. Archived from the original on 19 July 2016.
  6. ^ a b Rohli, Robert V.; Vega, Anthony J. (2011). Climatology. Jones & Bartlett Learning. p. 187. ISBN 978-0763791018. Archived from the original on 2013-06-19. Retrieved 2011-07-23.
  7. ^ Glossary of Meteorology (June 2000). "Monsoon". American Meteorological Society. Archived from the original on 2008-03-22. Retrieved 2008-03-14.
  8. ^ International Committee of the Third Workshop on Monsoons. The Global Monsoon System: Research and Forecast. Archived 2008-04-08 at the Wayback Machine Retrieved on 2008-03-16.
  9. ^ "monsoon, n." OED Online. June 2018. Oxford University Press. Retrieved 1 August 2018.
  10. ^ ROYDEN, L.H., BURCHFIEL, B.C., VAN DER HILST, Rob, WHIPPLE, K.X., HODGES, K.V., KING, R.W., and CHEN, Zhiliang. UPLIFT AND EVOLUTION OF THE EASTERN TIBETAN PLATEAU. Archived 2008-05-03 at the Wayback Machine Retrieved on 2008-05-11.
  11. ^ P. D. Clift, M. K. Clark, and L. H. Royden. An Erosional Record of the Tibetan Plateau Uplift and Monsoon Strengthening in the Asian Marginal Seas. Archived 2008-05-27 at the Wayback Machine Retrieved on 2008-05-11.
  12. ^ Integrated Ocean Drilling Program. Earth, Oceans, and Life. Archived 2007-10-26 at the Wayback Machine Retrieved on 2008-05-11.
  13. ^ Gupta, A. K.; Thomas, E. (2003). "Initiation of Northern Hemisphere glaciation and strengthening of the northeast Indian monsoon: Ocean Drilling Program Site 758, eastern equatorial Indian Ocean". Geology. 31 (1): 47–50. doi:10.1130/0091-7613(2003)031<0047:IONHGA>2.0.CO;2.
  14. ^ Srinivasan, M. S.; Sinha, D. K. (2000). "Ocean circulation in the tropical Indo-Pacific during early Pliocene (5.6–4.2 Ma): Paleobiogeographic and isotopic evidence". Proceedings of the Indian Academy of Sciences - Earth and Planetary Sciences. 109 (3): 315–328. ISSN 0253-4126.
  15. ^ D. K. Sinha; A. K. Singh & M. Tiwari (2006-05-25). "Palaeoceanographic and palaeoclimatic history of ODP site 763A (Exmouth Plateau), South-east Indian Ocean: 2.2 Ma record of planktic foraminifera". Current Science. 90 (10). JSTOR 24091985.
  16. ^ "Sea breeze – definition of sea breeze by The Free Dictionary".
  17. ^ "Liquids and Fluids – Specific Heats". Archived from the original on 2007-08-09.
  18. ^ "Solids – Specific Heats". Archived from the original on 2012-09-22.
  19. ^ "Monsoon". Britannica. Archived from the original on 2007-10-13. Retrieved 2007-05-15.
  20. ^ Dr. Michael Pidwirny (2008). CHAPTER 8: Introduction to the Hydrosphere (e). Cloud Formation Processes. Archived 2008-12-20 at the Wayback Machine Physical Geography. Retrieved on 2009-01-01.
  21. ^ Bart van den Hurk and Eleanor Blyth (2008). Global maps of Local Land–Atmosphere coupling. Archived 2009-02-25 at the Wayback Machine KNMI. Retrieved on 2009-01-02.
  22. ^ Robert Penrose Pearce (2002). Meteorology at the Millennium. Archived 2016-04-27 at the Wayback Machine Academic Press, p. 66. ISBN 978-0-12-548035-2. Retrieved on 2009-01-02.
  23. ^ Glossary of Meteorology (June 2000). "Gust Front". American Meteorological Society. Archived from the original on 2011-05-05. Retrieved 2008-07-09.
  24. ^ a b "Southwest Monsoon 2017 Forecast: Warmer-Than-Average Conditions Could Lead to More Storms". Archived from the original on 2017-06-06. Retrieved 2017-06-06.
  25. ^ a b c d e f Silva, V. B. S.; Kousky, V. E. (2012). "The South American Monsoon System: Climatology and Variability" (PDF). In Wang, S.-Y; Gillies, R. R. Modern Climatology. Rijeka: Intech. pp. 123–152. doi:10.5772/38565. ISBN 978-953-51-0095-9. Archived from the original (PDF) on December 15, 2017.
  26. ^ a b c Innovations Report. Monsoon in West Africa: Classic continuity hides a dual-cycle rainfall regime. Archived 2011-09-19 at the Wayback Machine Retrieved on 2008-05-25.
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  29. ^ African Monsoon Multidisciplinary Analyses (AMMA). "Characteristics of the West African Monsoon". AMMA. Archived from the original on July 12, 2007. Retrieved 2009-10-15.
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  31. ^ New Mexico Tech. Lecture 17: 1. North American Monsoon System. Retrieved on 2008-02-29. Archived October 30, 2008, at the Wayback Machine
  32. ^ Explore, Team (2005). Weather and Climate: India in Focus. EdPower21 Education Solutions. p. 28.
  33. ^ Ahmad, Latief; Kanth, Raihana Habib; Parvaze, Sabah; Mahdi, Syed Sheraz (2017). Experimental Agrometeorology: A Practical Manual. Springer. p. 121. ISBN 978-3-319-69185-5.
  34. ^ "Why India's Twin Monsoons Are Critical To Its Well-Being | The Weather Channel". The Weather Channel. Retrieved 2018-09-05.
  35. ^ Official Web Site of District Sirsa, India. District Sirsa. Archived 2010-12-28 at the Wayback Machine Retrieved on 2008-12-27.
  36. ^ Blumer, Felix P. (1998). "Investigations of the precipitation conditions in the central part of the Tianshan mountains". In Kovar, Karel. Hydrology, water resources and ecology in headwaters. Volume 248 of IAHS publication (PDF). International Association of Hydrological Sciences. pp. 343–350. ISBN 978-1-901502-45-9.
  37. ^ "NORTHEAST MONSOON". Archived from the original on 2015-12-29.
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  39. ^ Visser, S.W. (1953). Some remarks on the European monsoon. Birkhäuser: Basel.
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Further reading

  • International Committee of the Third Workshop on Monsoons. The Global Monsoon System: Research and Forecast.
  • Chang, C.P., Wang, Z., Hendon, H., 2006, The Asian Winter Monsoon. The Asian Monsoon, Wang, B. (ed.), Praxis, Berlin, pp. 89–127.

External links

Climate of India

The Climate of India comprises a wide range of weather conditions across a vast geographic scale and varied topography, making generalisations difficult. Based on the Köppen system, India hosts six major climatic subtypes, ranging from arid desert in the west, alpine tundra and glaciers in the north, and humid tropical regions supporting rainforests in the southwest and the island territories. Many regions have starkly different microclimates. The country's meteorological department follows the international standard of four climatological seasons with some local adjustments: winter (December, January and February), summer (March, April and May), a monsoon rainy season (June to September), and a post-monsoon period (October to November).

India's geography and geology are climatically pivotal: the Thar Desert in the northwest and the Himalayas in the north work in tandem to effect a culturally and economically important monsoonal regime. As Earth's highest and most massive mountain range, the Himalayas bar the influx of frigid katabatic winds from the icy Tibetan Plateau and northerly Central Asia. Most of North India is thus kept warm or is only mildly chilly or cold during winter; the same thermal dam keeps most regions in India hot in summer.

Though the Tropic of Cancer—the boundary between the tropics and subtropics—passes through the middle of India, the bulk of the country can be regarded as climatically tropical. As in much of the tropics, monsoonal and other weather patterns in India can be wildly unstable: epochal droughts, floods, cyclones, and other natural disasters are sporadic, but have displaced or ended millions of human lives. There is one scientific opinion which states that in South Asia such climatic events are likely to change in unpredictability, frequency, and severity. Ongoing and future vegetative changes and current sea level rises and the attendant inundation of India's low-lying coastal areas are other impacts, current or predicted, that are attributable to global warming.

East Asian Monsoon

The East Asian monsoon is a monsoonal flow that carries moist air from the Indian Ocean and Pacific Ocean to East Asia. It affects approximately one-third of the global population, influencing the climate of Japan (including Okinawa), the Koreas, Taiwan, Hong Kong, Macau, and much of Mainland China. It is driven by temperature differences between the East Asian continent and the Pacific Ocean. The East Asian monsoon is divided into a warm and wet summer monsoon and a cold and dry winter monsoon. This cold and dry winter monsoon is responsible for the aeolian dust deposition and pedogenesis that resulted in the creation of the Loess Plateau. The monsoon influences weather patterns as far north as Siberia, causing wet summers that contrast with the cold and dry winters caused by the Siberian High, which counterbalances the monsoon's effect on northerly latitudes.

In most years, the monsoonal flow shifts in a very predictable pattern, with winds being southeasterly in late June, bringing significant rainfall to the Korean Peninsula and Japan (in Taiwan and Okinawa this flow starts in May). This leads to a reliable precipitation spike in July and August. However, this pattern occasionally fails, leading to drought and crop failure. In the winter, the winds are northeasterly and the monsoonal precipitation bands move back to the south, and intense precipitation occurs over southern China and Taiwan.

The East Asian monsoon is known as jangma (장마) in Korea. In Japan the monsoon boundary is referred to as the tsuyu (梅雨) as it advances northward during the spring, while it is referred to as the shurin when the boundary retreats back southward during the autumn months. Over Japan and Korea, the monsoon boundary typically takes the form of a quasi-stationary front separating the cooler air mass associated with the Okhotsk High to the north from the hot, humid air mass associated with the subtropical ridge to the south. After the monsoon boundary passes north of a given location, it is not uncommon for daytime temperatures to exceed 32 °C (90 °F) with dewpoints of 24 °C (75 °F) or higher.

Gorilla Monsoon

Robert James Marella (June 4, 1937 – October 6, 1999), better known by his ring name of Gorilla Monsoon, was an American professional wrestler, play-by-play commentator, and booker.

Monsoon is famous for his run as a super-heavyweight main eventer, and later as the voice of the World Wrestling Federation, as commentator and backstage manager during the 1980s and 1990s. He also portrayed the on-screen role of WWF President from 1995 to 1997.

In professional wrestling, the staging area just behind the entrance curtain at an event, a position which Marella established and where he could often be found during WWF shows late in his career, is named the "Gorilla Position" in his honor. Although remembered fondly by many viewers, Monsoon was voted Worst Television Announcer a record six times by readers of the Wrestling Observer Newsletter in the publication's annual awards poll.

Helicopter bucket

A helicopter bucket is a specialised bucket suspended on a cable carried by a helicopter to deliver water for aerial firefighting. Each bucket has a release valve on the bottom which is controlled by the helicopter crew. When the helicopter is in position, the crew releases the water to extinguish or suppress the fire below. Each release of the water is referred to as a drop. The design of the buckets allows the helicopter to hover over a water source – such as a lake, river, pond, or tank – and lower the bucket into the water to refill it. This allows the helicopter crew to operate the bucket in remote locations without the need to return to a permanent operating base, reducing the time between successive drops.

Horse latitudes

Horse latitudes, subtropical ridges or subtropical highs are the subtropical latitudes between 30 and 35 degrees both north and south where Earth's atmosphere is dominated by the subtropical high, an area of high pressure, which suppresses precipitation and cloud formation, and has variable winds mixed with calm winds.

It is the product of the global air circulation cell known as the Hadley Cell. The subtropical ridge is characterized by mostly calm winds, which act to reduce air quality under its axis by causing fog overnight, and haze during daylight hours as a result of the stable atmosphere found near its location. The air descending from the upper troposphere flows out from its center at surface level toward the upper and lower latitudes of each hemisphere, creating both the trade winds and the westerlies. The subtropical ridge moves poleward during the summer, reaching its most northern latitude in early fall, before moving equatorward during the cold season. The El Niño southern climate oscillation (ENSO) can displace the northern hemisphere subtropical ridge, with La Niñas allowing for a more northerly axis for the ridge, while El Niños show flatter, more southerly ridges. The change of the ridge position during ENSO cycles changes the tracks of tropical cyclones that form around their equatorward and western peripheries. As the subtropical ridge varies in position and strength, it can enhance or depress monsoon regimes around their low-latitude periphery.

The horse latitudes are associated with the subtropical anticyclone. The belt in the Northern Hemisphere is sometimes called the "calms of Cancer" and that in the Southern Hemisphere the "calms of Capricorn".

The consistently warm, dry, and sunny conditions of the horse latitudes are the main cause for the existence of the world's major non-polar deserts, such as the Sahara Desert in Africa, the Arabian and Syrian deserts in the Middle East, the Mojave and Sonoran deserts in the southwestern United States and northern Mexico, all in the Northern Hemisphere; and the Atacama Desert, the Kalahari Desert, and the Australian Desert in the Southern Hemisphere.

Indian Ocean

The Indian Ocean is the third largest of the world's oceanic divisions, covering 70,560,000 km2 (27,240,000 sq mi) (approximately 20% of the water on the Earth's surface). It is bounded by Asia on the north, on the west by Africa, on the east by Australia, and on the south by the Southern Ocean or, depending on definition, by Antarctica.

Jinkx Monsoon

Jerick Hoffer (born September 18, 1987), better known by the drag persona Jinkx Monsoon, is an American drag performer, actor, comedian and singer best known for winning the fifth season of RuPaul's Drag Race.

Low-pressure area

A low-pressure area, low, depression or cyclone is a region on the topographic map where the atmospheric pressure is lower than that of surrounding locations. Low-pressure systems form under areas of wind divergence that occur in the upper levels of the troposphere. The formation process of a low-pressure area is known as cyclogenesis. Within the field of meteorology, atmospheric divergence aloft occurs in two areas. The first area is on the east side of upper troughs, which form half of a Rossby wave within the Westerlies (a trough with large wavelength that extends through the troposphere). A second area of wind divergence aloft occurs ahead of embedded shortwave troughs, which are of smaller wavelength. Diverging winds aloft ahead of these troughs cause atmospheric lift within the troposphere below, which lowers surface pressures as upward motion partially counteracts the force of gravity.

Thermal lows form due to localized heating caused by greater sunshine over deserts and other land masses. Since localized areas of warm air are less dense than their surroundings, this warmer air rises, which lowers atmospheric pressure near that portion of the Earth's surface. Large-scale thermal lows over continents help drive monsoon circulations. Low-pressure areas can also form due to organized thunderstorm activity over warm water. When this occurs over the tropics in concert with the Intertropical Convergence Zone, it is known as a monsoon trough. Monsoon troughs reach their northerly extent in August and their southerly extent in February. When a convective low acquires a well-hot circulation in the tropics it is termed a tropical cyclone. Tropical cyclones can form during any month of the year globally, but can occur in either the northern or southern hemisphere during December.

Atmospheric lift will also generally produce cloud cover through adiabatic cooling once the air becomes saturated as it rises, although the low-pressure area typically brings cloudy skies, which act to minimize diurnal temperature extremes. Since clouds reflect sunlight, incoming shortwave solar radiation decreases, which causes lower temperatures during the day. At night the absorptive effect of clouds on outgoing longwave radiation, such as heat energy from the surface, allows for warmer diurnal low temperatures in all seasons. The stronger the area of low pressure, the stronger the winds experienced in its vicinity. Globally, low-pressure systems are most frequently located over the Tibetan Plateau and in the lee of the Rocky mountains. In Europe (particularly in the British Isles and Netherlands), recurring low-pressure weather systems are typically known as "depressions".

Monsoon Wedding

Monsoon Wedding is a 2001 drama film directed by Mira Nair and written by Sabrina Dhawan. The film stars Naseeruddin Shah, Lillete Dubey, Shefali Shah and Vasundhara Das. The story depicts romantic entanglements during a traditional Punjabi Hindu wedding in Delhi. Dhawan wrote the first draft of the screenplay in a week while she was at Columbia University's MFA film program. Although it is set entirely in New Delhi, the film was an international co-production between companies in India, the United States, Italy, France, and Germany.

Monsoon Wedding earned above $30 million at the box office. The film won the Golden Lion award and received a Golden Globe Award nomination. A musical based on the film was in development and was premiered on Broadway in April 2014. The film was premiered in the Marché du Film section of the 2001 Cannes Film Festival. In 2017, IndieWire named it the best romance of the 21st century.

Monsoon of South Asia

The monsoon of South Asia is among several geographically distributed global monsoons. It affects the Indian subcontinent, where it is one of the oldest and most anticipated weather phenomena and an economically important pattern every year from June through September, but it is only partly understood and notoriously difficult to predict. Several theories have been proposed to explain the origin, process, strength, variability, distribution, and general vagaries of the monsoon, but understanding and predictability are still evolving.

The unique geographical features of the Indian subcontinent, along with associated atmospheric, oceanic, and geophysical factors, influence the behavior of the monsoon. Because of its effect on agriculture, on flora and fauna, and on the climates of nations such as Bangladesh, Bhutan, India, Nepal, Pakistan, and Sri Lanka — among other economic, social, and environmental effects — the monsoon is one of the most anticipated, tracked, and studied weather phenomena in the region. It has a significant effect on the overall well-being of residents and has even been dubbed the "real finance minister of India".

Monsoon trough

The monsoon trough is a portion of the Intertropical Convergence Zone in the Western Pacific, as depicted by a line on a weather map showing the locations of minimum sea level pressure, and as such, is a convergence zone between the wind patterns of the southern and northern hemispheres.

Westerly monsoon winds lie in its equatorward portion while easterly trade winds exist poleward of the trough. Right along its axis, heavy rains can be found which usher in the peak of a location's respective rainy season. As it passes poleward of a location, hot and dry conditions develop. The monsoon trough plays a role in creating many of the world's rainforests.

The term "monsoon trough" is most commonly used in monsoonal regions of the Western Pacific such as Asia and Australia. The migration of the ITCZ/monsoon trough into a landmass heralds the beginning of the annual rainy season during summer months. Depressions and tropical cyclones often form in the vicinity of the monsoon trough, with each capable of producing a year's worth of rainfall in a matter of days.

North American Monsoon

The North American monsoon, variously known as the Southwest monsoon, the Mexican monsoon, the New Mexican monsoon, or the Arizona monsoon, is a pattern of pronounced increase in thunderstorms and rainfall over large areas of the southwestern United States and northwestern Mexico, typically occurring between July and mid September. During the monsoon, thunderstorms are fueled by daytime heating and build up during the late afternoon-early evening. Typically, these storms dissipate by late night, and the next day starts out fair, with the cycle repeating daily. The monsoon typically loses its energy by mid-September when drier and cooler conditions are reestablished over the region. Geographically, the North American monsoon precipitation region is centered over the Sierra Madre Occidental in the Mexican states of Sinaloa, Durango, Sonora and Chihuahua.

Parliament of India

The Parliament of India is the supreme legislative body of the Republic of India. It is a bicameral legislature composed of the President of India and the two houses: the Rajya Sabha (Council of States) and the Lok Sabha (House of the People). The President in his role as head of legislature has full powers to summon and prorogue either house of Parliament or to dissolve Lok Sabha. The president can exercise these powers only upon the advice of the Prime Minister and his Union Council of Ministers.

Those elected or nominated (by the President) to either house of Parliament are referred to as Members of Parliament (MP). The Members of Parliament, Lok Sabha are directly elected by the Indian public voting in Single-member districts and the Members of Parliament, Rajya Sabha are elected by the members of all State Legislative Assembly by proportional representation. The Parliament has a sanctioned strength of 545 in Lok Sabha including the 2 nominees from the Anglo-Indian Community by the President, and 245 in Rajya Sabha including the 12 nominees from the expertise of different fields of science, culture, art and history. The Parliament meets at Sansad Bhavan in New Delhi.

Ponnaiyar River

The South Pennar River is known as Dakshina Pinakini in Kannada and Thenpennai or Ponnaiyar in Tamil.

The river originates in the Nandi Hills in the Chikkaballapura district of Karnataka and flows through Tamil Nadu before emptying into the Bay of Bengal. It has a catchment area of 1,424 square miles (3,690 km2) located in Karnataka and Tamil Nadu states. Small dams of Kelavarapalli and Krishnagiri dams are built across this river near Hosur and Krishnagiri. The largest dam on this river, Sathanur Dam with 7.3 Tmcft Gross Capacity is built near Tiruvannamalai. Moongilthuraipattu Sugar Factory is also situated on the bank of river.

The river is dry for the most part of the year. Water flows during the monsoon season when it is fed by the south-west monsoon in catchment area and the northeast monsoon in Tamil Nadu. However this water flow raises the water table throughout the river basin and feeds numerous reservoirs/tanks.

The old river Dakshina Pinakini does not exist anymore.

Substantial part of Bangalore's sewage enters this river via Bellandur and Varthur Lakes and other channels.The sand build of the river is quite impressive, suggesting that it may have been a perennial river with much larger water flow in the past. Mention of the river is found in Sangam and medieval (Thevaram - Bhakti cult era) literature, where it is depicted as rich with lush vegetation on its banks. There are various temples on its banks. It irrigates Krishnagiri, Tiruvannamalai, Vizhuppuram and Cuddalore districts and empties into the Bay of Bengal .

This river is now looted for its rich availability of sand. As the water flow will be only in monsoon seasons, the river is dry in remaining parts of the year.

Sand mafia is biggest and most dangerous elements behind killing of large rivers in south India.

Tropical and subtropical dry broadleaf forests

The tropical and subtropical dry broadleaf forest is a habitat type defined by the World Wide Fund for Nature and is located at tropical and subtropical latitudes. Though these forests occur in climates that are warm year-round, and may receive several hundred centimeters of rain per year, they have long dry seasons which last several months and vary with geographic location. These seasonal droughts have great impact on all living things in the forest.

Deciduous trees predominate in most of these forests, and during the drought a leafless period occurs, which varies with species type. Because trees lose moisture through their leaves, the shedding of leaves allows trees such as teak and mountain ebony to conserve water during dry periods. The newly bare trees open up the canopy layer, enabling sunlight to reach ground level and facilitate the growth of thick underbrush. Trees on moister sites and those with access to ground water tend to be evergreen. Infertile sites also tend to support evergreen trees. Three tropical dry broadleaf forest ecoregions, the East Deccan dry evergreen forests, the Sri Lanka dry-zone dry evergreen forests, and the Southeastern Indochina dry evergreen forests, are characterized by evergreen trees.Though less biologically diverse than rainforests, tropical dry forests are home to a wide variety of wildlife including monkeys, deer, large cats, parrots, various rodents, and ground dwelling birds. Mammalian biomass tends to be higher in dry forests than in rain forests, especially in Asian and African dry forests. Many of these species display extraordinary adaptations to the difficult climate.This biome is alternately known as the tropical bane forest biome or the tropical and subtropical deciduous forest biome.

Tropical climate

A tropical climate in the Köppen climate classification is a non-arid climate in which all twelve months have mean temperatures of warmer than 18 °C (64 °F). In tropical climates there are often only two seasons: a wet season and a dry season. Tropical climates are frost-free, and changes in the solar angle are small. In tropical climates temperature remains relatively constant (hot) throughout the year. Sunlight is intense.

Tropical monsoon climate

A area of tropical monsoon climate (occasionally known as a tropical wet climate or a tropical monsoon and trade-wind littoral climate) is a type of climate that corresponds to the Köppen climate classification category "Am". Tropical monsoon climates have monthly mean temperatures above 18 °C (64.4 °F) in every month of the year. Tropical monsoon climates is the intermediate climate between the wet Af (or tropical rainforest climate) and Aw (or tropical savanna climate).

A tropical monsoon climate, however, has its driest month seeing on average less than 60 mm, but more than 100 – [total annual precipitation {mm}/25] of average monthly precipitation. This latter fact is in direct contrast to a tropical savanna climate, whose driest month sees less than 60 mm of precipitation and also less than 100 – [total annual precipitation {mm}/25] of average monthly precipitation. In essence, a tropical monsoon climate tends to either see more rainfall than a tropical savanna climate or have less pronounced dry seasons. Additionally, a tropical monsoon climate tends to see less variance in temperatures during the course of the year than a tropical savanna climate. This climate has a driest month which nearly always occurs at or soon after the "winter" solstice for that side of the equator.

Tropical savanna climate

Tropical savanna climate or tropical wet and dry climate is a type of climate that corresponds to the Köppen climate classification categories "Aw" and "As".

Tropical savanna climates have monthly mean temperatures above 18 °C (64 °F) in every month of the year and typically a pronounced dry season, with the driest month having less than 60 mm (2.36 inches) of precipitation and also less than 100 – [total annual precipitation {mm}/25] of precipitation. This latter fact is in direct contrast to a tropical monsoon climate, whose driest month sees less than 60 mm of precipitation but has more than 100 – [total annual precipitation {mm}/25] of precipitation. In essence, a tropical savanna climate tends to either see less rainfall than a tropical monsoon climate or have more pronounced dry season(s).

In tropical savanna climates, the dry season can become severe, and often drought conditions prevail during the course of the year. Tropical savanna climates often feature tree-studded grasslands, rather than thick jungle. It is this widespread occurrence of tall, coarse grass (called savanna) which has led to Aw and As climates often being referred to as tropical savanna. However, there is some doubt whether tropical grasslands are climatically induced. Additionally, pure savannas, without trees, are the exception rather than the rule.

Wet season

The monsoon season is the time of year when most of a region's average annual rainfall occurs. Generally the season lasts at least a month. The term "green season" is also sometimes used as a euphemism by tourist authorities. Areas with wet seasons are dispersed across portions of the tropics and subtropics.Under the Köppen climate classification, for tropical climates, a wet season month is defined as a month where average precipitation is 60 millimetres (2.4 in) or more. In contrast to areas with savanna climates and monsoon regimes, Mediterranean climates have wet winters and dry summers. Dry and rainy months are characteristic of tropical seasonal forests: in contrast to tropical rainforests, which do not have dry or wet seasons, since their rainfall is equally distributed throughout the year. Some areas with pronounced rainy seasons will see a break in rainfall mid-season, when the intertropical convergence zone or monsoon trough moves to higher latitudes in the middle of the warm season.When the wet season occurs during a warm season, or summer, precipitation falls mainly during the late afternoon and early evening. In the wet season, air quality improves, fresh water quality improves, and vegetation grows substantially, leading to crop yields late in the season. Rivers overflow their banks, and some animals retreat to higher ground. Soil nutrients diminish and erosion increases. The incidence of malaria increases in areas where the rainy season coincides with high temperatures, particularly in tropical areas. Some animals have adaptation and survival strategies for the wet season. Often, the previous dry season leads to food shortages in the wet season, as the crops have yet to mature.

Climate oscillations

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