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76-546: The Somali current is characterized by seasonal changes influenced by the Southwest monsoon and the Northeast Monsoon. During the months of June to September, the warm Southwest monsoon moves the coastal waters northeastward, creating coastal upwelling . The upwelled water is carried offshore by Ekman transport and merges with water that was brought to the surface by open-ocean upwelling. The Somali Jet , aka.

152-614: 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,

228-410: 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. Similar rainfall is caused when moist ocean air

304-622: 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. The southwestern summer monsoons occur from June through September. The Thar Desert and adjoining areas of the northern and central Indian subcontinent heat up considerably during

380-547: A low pressure system known as a monsoon trough develops over South-East Asia and Australasia and winds are directed toward Australia. In the Philippines, northeast monsoon is called Amihan . The East Asian monsoon affects large parts of Indochina , the Philippines , China, Taiwan , Korea, Japan, and Siberia . It is characterised by a warm, rainy summer monsoon and a cold, dry winter monsoon. The rain occurs in

456-464: 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 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

532-675: A seasonally changing pattern, although technically there is also a dry phase. The term is also sometimes used to describe locally heavy but short-term rains. The major monsoon systems of the world consist of the West African , Asian– Australian , the North American , and South American monsoons. The term was first used in English in British India and neighboring countries to refer to the big seasonal winds blowing from

608-432: A southward undercurrent develops underneath the northward surface current between 8 and 12°N. Winter; A northward cross-equatorial undercurrent (depth 150-400m) flows underneath the southward surface Somali Current, with their flows balancing. Because of this undercurrent, near the equator, the surface (southward) Somali Current is extremely shallow (less than 150m). The Great Whirl is a huge anti-cyclonic eddy generated by

684-590: A timing of the monsoon beginning 15–20 million years ago and linked to early Tibetan uplift. Testing of this hypothesis awaits deep ocean sampling by the Integrated Ocean Drilling Program . The monsoon has varied significantly in strength since this time, largely linked to global climate change , especially the cycle of the Pleistocene ice ages. A study of Asian monsoonal climate cycles from 123,200 to 121,210 years BP, during

760-646: A weakening of the 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 Throughflow 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

836-477: Is 400–600 km in horizontal diameter, and typical surface current velocity is 1.5-2.0 m/s. How the Great Whirl forms exactly isn't yet fully understood, but the analytical approach of applying Rossby wave theory can explain its basic formation mechanism. By observation and analysis of [Schott and Quadfasel (1982)], the summer monsoon develops suddenly during June–July, and drives westward water flow in

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912-666: Is directly of "cyclonic" (i.e., monsoon-driven) origin (as opposed to " local convection "). The effects also extend westwards to the Mediterranean, where however the impact of the monsoon is to induce drought via the Rodwell-Hoskins mechanism . Around September, with the sun retreating south, the northern landmass of the Indian subcontinent begins to cool off rapidly, and air pressure begins to build over northern India. The Indian Ocean and its surrounding atmosphere still hold their heat, causing cold wind to sweep down from

988-460: Is further boosted by the activities of the offshore eddy, the Great Whirl. Total zooplankton biomass consists of about 25% Euphausids, the rest being Copepods (dominant zooplankton species in the region ~ Calanoides carinatus and Eucalanus elongates). However, the fast-moving Somali Current reduces the residence time of the upwelled nutrient-rich water, thus limiting biological productivity in this region somewhat. A major part of this unutilized nutrient

1064-459: Is less water movement toward the center than is leaving, creating a divergence in the upper layer and resulting in an upwelling event (Ekman suction). In contrast, to the right of the center of the jet, more water is coming from the center than is leaving, creating a downwelling event (Ekman pumping). This open-ocean upwelling in combination with the coastal upwelling causes a massive upwelling. The history of physical oceanographic approaches to

1140-533: Is lifted upwards by mountains, surface heating, convergence at the surface, divergence aloft, or from storm-produced outflows at the surface. However the lifting occurs, the air cools due to expansion in lower pressure, and this produces condensation . 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

1216-582: Is the dominant mode of the Somali current 1972,1973 Leetma  : local winds are crucial to the onset of the Somali Current. 1975 Colborn  : climatological analysis of the entire Indian Ocean from bathythermograph and hydrocast observations 1976 Hurlburt & Thompson  : Characterize the Somali current as a time-dependent, baroclinic, inertial boundary current. 1976 Bruce  : time-series analyses, XBT cross-section measurement by

1292-593: 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 Throughflow. 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

1368-410: Is traditionally a seasonal reversing wind accompanied by corresponding changes in precipitation but is now used to describe seasonal changes in atmospheric circulation and precipitation associated with annual latitudinal oscillation of the Intertropical Convergence Zone (ITCZ) between its limits to the north and south of the equator. Usually, the term monsoon is used to refer to the rainy phase of

1444-696: Is transported to the southern Arabian Sea, supporting biological production there. Furthermore, the high wind speeds (approximately 15 m/s) of the Southwest monsoon affecting the Somali Current induce intense vertical mixing, increasing the thickness of the mixed layer as well as overall surface nutrient enrichment leading to high productivity. After this season, with the onset of the Northeast (Winter) Monsoon, primary productivity decreases, though zooplankton density does so only slightly. Southwest monsoon A monsoon ( / m ɒ n ˈ s uː n / )

1520-581: The Bay of Bengal and Arabian Sea in the southwest bringing heavy rainfall to the area. The etymology of the word monsoon is not wholly certain. The English monsoon came from Portuguese monção ultimately from Arabic موسم ( mawsim , "season"), "perhaps partly via early modern Dutch monson ". Strengthening of the Asian monsoon has been linked to the uplift of the Tibetan Plateau after

1596-622: The Eemian interglacial, suggests that they had an average duration of around 64 years, with the minimum duration being around 50 years and the maximum approximately 80 years, similar to today. A study of marine plankton suggested that the South Asian Monsoon (SAM) 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

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1672-756: The Hadley circulation during boreal winter. 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

1748-507: 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 cold dry 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

1824-785: The Sahara and the equatorial Atlantic Ocean. The ITCZ migrates northward from the equatorial Atlantic in February, reaches western Africa on or near June 22, then moves back to the south by October. 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. The North American monsoon ( NAM ) occurs from late June or early July into September, originating over Mexico and spreading into

1900-618: 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. 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". The rain usually arrives in two waves, at

1976-704: The EASM grew in strength, but it has been suggested to have decreased in strength during Heinrich events . The EASM expanded its influence deeper into the interior of Asia as sea levels rose following the LGM; it also underwent a period of intensification during the Middle Holocene, around 6,000 years ago, due to orbital forcing made more intense by the fact that the Sahara at the time was much more vegetated and emitted less dust. This Middle Holocene interval of maximum EASM

2052-574: The EXXON tankers 1979 USNS WILKES  : the Great Whirl (Prime Eddy) and the Socotra Eddy together with the strong shear zone along the eastern edge of the Great Whirl were observed during late August and early September 1979. The Somali Current is rapid response, shallow and shifts its direction seasonally. Especially from 5°N and southward, the Somali current is extremely shallow (under 150m depth southward flow all year through). Further north,

2128-686: The East African coast, and finally enters the Gulf of Aden between the Socotra Archipelago and the Horn of Africa. The mean flow velocity of this outgoing current is about 5 Sv. The period between August and September is the late phase of the summer monsoon. During this period, the Great Whirl almost forms a closed circulation, and strong upwelling streams (colder than 17 °C, typical upwelling water temperature ~ 19-23 °C) develop near

2204-601: The East Asian Winter Monsoon (EAWM) became stronger as the subarctic front shifted southwards. An abrupt intensification of the EAWM occurred 5.5 million years ago. The EAWM was still significantly weaker relative to today between 4.3 and 3.8 million years ago but abruptly became more intense around 3.8 million years ago as crustal stretching widened the Tsushima Strait and enabled greater inflow of

2280-474: The Findlater Jet, a narrow low-level, atmospheric jet, also develops during the Southwest monsoon, and blows diagonally across the Indian Ocean, parallel to the coasts of Somalia and Oman. As a result, an Ekman transport is created to the right of the wind. At the center of the jet, the transport is maximum and decreases to the right and left with increasing distance. To the left of the jet center, there

2356-506: 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

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2432-526: The Great Whirl itself) also play a large part in regulating the heat flux budget of the North Indian Ocean. The offshore Somali coastal area is one of the most productive marine ecosystems in the world. Especially during the southwest Indian monsoon, strong upwelling pumps cold (17-22 °C) and highly nutrient rich (about 5 to 20 μm of nitrate ) subsurface water to the coastal region. During this season, mean phytoplankton density and productivity

2508-612: The Gulf Stream, the Kuroshio current). However, volume transport maxima as high as 60-70 Sv (comparable to the Gulf Stream) have been measured around the south of Socotra Island . The Somali Current reaches speeds of up to 7 knots during the summer months weakening and eventually reversing direction during the winter. The Somali Current is driven principally by the seasonal monsoon winds. In (Northern) summer (May – September)

2584-845: The Late Holocene, significant glacial accumulation in the Himalayas still occurred due to cold temperatures brought by westerlies from the west. During the Middle Miocene , the July ITCZ, the zone of rainfall maximum, migrated northwards, increasing precipitation over southern China during the East Asian Summer Monsoon (EASM) while making Indochina drier. During the Late Miocene Global Cooling (LMCG), from 7.9 to 5.8 million years ago,

2660-522: The Northeastward Somali current has the following two sub-season periods. During June–July, the Great Whirl grows at 4-10°N, and a cold wedge shape water mass develops to the offshore at latitude 10-12°N. The size and strength of the Great Whirl during the summer monsoon is measured as 10 cm/s velocity at about 1000 m depth, while some visible gyre structure is observed at further depth. The upper layer Somali Current flows northwards along

2736-595: The Northern Somali coast. After the summer monsoon recedes (Oct-Nov) : During this period, the southwest monsoon winds continually weaken, so the Northward Somali Current (extension flow of the EACC) no longer crosses the equator, turning instead to the east at around 3°N. However, the Great Whirl still remains. Southwestward current (Dec-Feb, Winter Monsoon) : During the fall (Sep-Nov), with

2812-506: 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. In 2018, a study of the SAM's variability over the past million years found that precipitation resulting from the monsoon was significantly reduced during glacial periods compared to interglacial periods like

2888-559: The Somali Current did not develop in June at all, so that during that time the eddy was severely weakened and of very small size - a prolonged onset phase. As the Somali Current developed through the summer, it was only in September that the Great Whirl finally maximized and began to disperse, entering the winter season (the wane). Conversely, the Great Whirl may also continue to exist until mid-October, still exhibiting large size and its curl structure may remain evident even longer, underneath

2964-451: The Somali coastline, the upwelling direction is to the offshore during the summer: The warm and salty Somali Current flows northward across the equator to turn to the East near Cape Guardafui. This flow deflection causes strong upwelling along the Somali coast, lowering coastal temperatures by 5 °C or more from May through September. During the winter season, the northeast monsoon reverses

3040-640: The Somali current flowing in (northern) summer, and one of the two gigantic Indian Ocean Gyres (the other is the Socotra Gyre). The Great Whirl can be observed between 5-10°N and 52-57°E off the Somali coast in the summer season, a location typically around 200 km southwest of the Socotra Gyre (between June and September). However, in the past both the Great Whirl and the Socotra Gyre have been known to occasionally collapse, and their exact locations differ from year to year. The Great Whirl's typical size

3116-418: The Somali current has begun from the mid-1960s with serious interests. From the mid-1960s until the late 1970s several magnificent theoretical studies had been proposed and gave physical answers of the current behaviors and formations. After the late 1970s, the physics of the Somali current enhanced by ocean data analyses with outstanding field measurements of the current properties. The research footprints during

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3192-615: 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

3268-535: 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. In Southern Asia, the northeastern monsoons take place from October to December when the surface high-pressure system is strongest. 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,

3344-458: The air temperature remains relatively stable for two reasons: water has a relatively high heat capacity (3.9 to 4.2 J g K ), 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 K ), and they can only transmit heat into the earth by conduction and not by convection. Therefore, bodies of water stay at

3420-583: 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, 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. Indian agriculture (which accounts for 25% of

3496-507: 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. The return of

3572-414: The behaviour of the LC during Quaternary at close stratigraphic intervals. The South American summer monsoon (SASM) is known to have become weakened during Dansgaard–Oeschger events. The SASM has been suggested to have been enhanced during Heinrich events. Monsoons were once considered as a large-scale sea breeze caused by higher temperature over land than in the ocean. This is no longer considered as

3648-670: 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. These temperature imbalances happen because oceans and land absorb heat in different ways. Over oceans,

3724-662: The climax of summer heat in June. 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

3800-558: The coast. Near the equator, the East African Coast Current (EACC) flows northward across the equator. The southern Somali Current flows northward as an extension of the EACC from south to the 3-4°N. Northeastward current (Jun-Sep, Summer Monsoon) : The Somali Current begins developing its strength from mid-May with the summer monsoon onset, and current velocities rapidly grow to the maximum until June and September with

3876-399: 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

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3952-654: The collision of the Indian subcontinent and Asia around 50 million years ago. 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

4028-430: The early 1960s to the late 1970s are presented as below. (early research histories before 1981) 1966 Warren et al.  : Oceanographers and Meteorologists agreed the existence of the Somali current and its behaviors, but its exact processes and involved nature sources had not been clearly understood. 1969 Lighthill  : the source of the Somali current is mass flux deposited by baroclinic and barotropic waves in

4104-459: 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

4180-492: The jet deepens somewhat, reaching the permanent thermocline. The structure of the current around the equator is extremely complex and similarly layered to the equatorial flows, though the Somali Current is oriented north-southward instead of east-westward. The typical water volume transported by the Somali Current amounts to 37 ± 5 Sv (0.037 ± 5 km/s) during mid-September, making the current circulation generally weaker than other mid-latitude western boundary currents (such as

4256-414: The location. Schott and Quadfasel applied first-mode Rossby waves to the water flows, and concluded that "the formation of the Great Whirl is a response to the very strong anti-cyclonic wind-stress curl". Since the Somali current changes seasonally, the Great Whirl also displays seasonal behaviour in keeping with the monsoon cycle. The eddy is usually evident between June and September, however e.g. in 1995,

4332-444: 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

4408-454: The north between approximately 8,000 and 4,000 BP, and most recently retreated southward once more between 4,000 and 0 BP. The January ITCZ migrated further south to its present location during the Middle Miocene, strengthening the summer monsoon of Australia that had previously been weaker. 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

4484-435: The northward Somali Coastal Current, shutting down coastal upwelling. Somali Undercurrent: April – early June ; A southward undercurrent develops underneath the northward surface current (depth 100-300m, monthly average velocity 20 cm/s, maximum 60 cm/s), stretching to the near 4°N and turning offshore. It is eventually terminated by the establishment of the deep–reaching Great Whirl. Fall – Winter; Similarly,

4560-413: 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

4636-423: The present day. The Indian Summer Monsoon (ISM) underwent several intensifications during the warming following the Last Glacial Maximum, specifically during the time intervals corresponding to 16,100–14,600 BP, 13,600–13,000 BP, and 12,400–10,400 BP as indicated by vegetation changes in the Tibetan Plateau displaying increases in humidity brought by an intensifying ISM. Though the ISM was relatively weak for much of

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4712-446: 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 Australia 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,

4788-417: 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

4864-440: The southwest monsoon blowing. During this season, the current direction is northeastward, and the velocity in mid-May is about 2.0 m/s and in June, 3.5 m/s and more. Typically the Somali Current will move about 1500 km to the northeast and, near Cape Guardafui (at 6~10°N), change its direction to the east to merge with the Indian Monsoon current. According to the works of Friedrich A. Schott and Julian P. McCreary Jr.,

4940-409: The southwest monsoon blows along the east coast of Africa and Oman. During the fall it reverses its direction to become a northeasterly wind during (Northern) winter. Before the onset of the monsoon (March–May) : During this season, shallow northward coastal current flows with 50–100 km width near the Somali coast, overlying a southward undercurrent. By alongshore winds, upwelling current flows to

5016-501: The strengthening northeast monsoon influencing it, the Somali Current gradually becomes weaker and slower. Finally, in early December, beginning south of 5°N and expanding rapidly to 10°N by January, the current reverses its direction, now flowing southwardly (velocities of 0.7 – 1.0 m/s). The Somali Current flows to the south throughout (Northern) Winter (Dec-Feb), constrained to the region south of 10°N, until in March, southward flow recedes again to 4°N to be reversed in April. During

5092-428: 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

5168-423: 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 northern China and Korea (July). When the monsoon ends in August, the rain belt moves back to southern China. The rainy season occurs from September to February and it is a major source of energy for

5244-483: 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. 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 controversial whether the North and South American weather patterns with incomplete wind reversal should be counted as true monsoons. The Asian monsoons may be classified into

5320-593: The warm Tsushima Current into the Sea of Japan. Circa 3.0 million years ago, the EAWM became more stable, having previously been more variable and inconsistent, in addition to being enhanced further amidst a period of global cooling and sea level fall. The EASM was weaker during cold intervals of glacial periods such as the Last Glacial Maximum (LGM) and stronger during interglacials and warm intervals of glacial periods. Another EAWM intensification event occurred 2.6 million years ago, followed by yet another one around 1.0 million years ago. During Dansgaard–Oeschger events ,

5396-415: The western boundary region. 1970 Düing  : presented the presence of alternative cyclonic and anti-cyclonic gyre, the Indian Ocean Gyres. Found eddy size of the Indian Ocean Gyres are much larger than the gyres of the other mid-latitude western boundary currents (the Indian Ocean Gyres ~ 300-500 nmi > the Gulf Stream / Kuroshio ~ 50 – 100 nmi) 1971 Düing & Szekelda  : the baroclinic mode

5472-656: 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

5548-474: The winter Somali Current. This seasonal behaviour of the Great Whirl affects the local coastal ocean flows and thus the Arabian Sea ecosystem: During the summer season, coastal upwelling currents strongly dependent on the shape and behaviour of the eddy are observed to the northwest of the Great Whirl. Not only does the biological productivity of the region depend on these upwelling currents, they (and thus,

5624-430: The winter monsoon, after crossing the equator, the southward Somali Current comes into confluence with the northward EACC and thereafter flows to the East. Upwelling behavior: One of the unique characteristics of the Somali Current is the presence of strong coastal upwelling - the only major instance of this happening at a western ocean boundary. Following Ekman transport and with the southwest monsoon blowing parallel to

5700-536: 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

5776-586: Was associated with an expansion of temperate deciduous forest steppe and temperate mixed forest steppe in northern China. By around 5,000 to 4,500 BP, the East Asian monsoon's strength began to wane, weakening from that point until the present day. A particularly notable weakening took place ~3,000 BP. The location of the EASM shifted multiple times over the course of the Holocene: first, it moved southward between 12,000 and 8,000 BP, followed by an expansion to

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