suppoUNDERSTANDING THE SOUTHWEST MONSOON AND ITS INFLUENCE ON ANCIENT TRADE BETWEEN INDIA, THE WEST AND SOUTH EAST ASIA
MILIND TAMBE
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A monsoon is a rainy ason which lasts for veral months and has lasting climatic effects. It refers to both the wet monsoon and the dry monsoon experienced periodically in the South East Asian continent. The term was first ud in English with this meaning in India, Bangladesh, Pakistan and neighbouring countries to mean the asonal winds blowing from the Indian Ocean and Arabian Sea in the southwest bringing heavy rainfall to the region.
The English name Monsoon, was derived from the Urdu/Hindi word mausam meaning 'weather' in the time of the British Empire.
In hydrology, monsoonal rainfall is considered to be that which occurs in any region that receives the majority of its rain during a particular ason, and so monsoons are referred to in relation to other regions such as in North America, Sub-Saharan Africa, Brazil and East Asia.
In terms of total precipitation, total area covered and the total number of people affected, monsoons affecting the Indian Subcontinent dwarf the North American monsoon (also called the "Mexican", "southwest", "dert", or "Arizona" monsoon).
The definition includes major wind systems that change direction asonally. Majority of summer monsoons have a dominant westerly component and a strong tendency to ascend and produce copious amounts of rain (becau of the condensation of water vapour 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 cau drought.
History
The Asian monsoon strengthened due to the uplift of the Tibetan Plateau after the collision of India and Asia around 50 million years ago. Evidence for when this first happened, remains controversial. Many geologists believe the monsoon first became strong around
8 million years ago bad on records from the Arabian Sea and the record of wind-blown dust in the 尘土的拼音
Loess Plateau of China. More recently plant fossils in China and new long-duration diment records from the South China Sea suggests, though not confirmed, a much older monsoon starting around 24 million years ago and linked to early Tibetan uplift. The monsoon has varied significantly in strength since this time, largely linked to global climate change, especially the cycle of the Pleistocene
ice ages.
Process of Monsoon
battleshipMonsoons are caud by the larger amplitude of the asonal cycle of land temperature compared to that of nearby oceans. This differential warming happens becau heat in the ocean is mixed vertically through a "mixed layer" that may be fifty metres deep, through
the action of wind and buoyancy-generated turbulence, whereas the land surface conducts heat slowly, with the asonal signal penetrating perhaps a metre or so. Additionally, the specific heat of liquid water is significantly higher than that of most materials that make up land. Together, the factors mean that the heat capacity of the layer participating in the asonal cycle is much larger over the oceans than over land, with the conquence that land warms faster and reaches a higher t
emperature than the ocean.
The hot air over the land tends to ri, creating an area of low pressure. This creates a steady wind blowing toward the land, bringing the moist near-surface air over the oceans with it. Similar rainfall is caud by the moist ocean air being 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 expansion in lower pressure, which in turn produces condensation.
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In winter, the land cools off quickly, but the ocean keeps the heat longer. The hot air over the ocean ris, creating a low pressure area and a breeze from land to ocean while a large area of drying high pressure is formed over the land, incread by wintertime cooling. Monsoons are similar to a breezes, a term usually referring to the localized, diurnal (daily) cycle of circulation near coastlines everywhere, but they are much larger in scale, stronger and asonal. Origin and Process of South-West Monsoon
The south-west monsoon travels thousands of kilometers from its birth off the Madagascar coast to Somalia from where it is deflected to India to its retreat
to Tibet in September and its final dissipation in Madagascar again — a journey transcending contin
ents, cultures, and different climates.
The south-west monsoon is born due to a high-pressure area called "Mascarenas High.” The wind direction at this point of time is southeasterly. The moisture-laden winds from this high-pressure area around Madagascar travel northwards to the African country of Somalia. As soon as they cross the equator, south-easterlies turn right to assume a southwesterly direction.
It is in Somalia that south-west monsoon assumes its true character. Explains Met director S C Bhan, "It is a jet-stream formed in May that brings the south-west monsoon from Somalia to India. Jet streams are relatively strong winds concentrated within a narrow stream in the atmosphere. The Somali jet-stream helps the south-west monsoon gain force and hence it hits the Indian subcontinent with great force."
From Somalia, it covers 2,500 km, 15 km above a level to come to India. The entire monsoon activity over the world takes place between the latitudes of 30 degrees south and north. In fact, monsoon reaches Southeast Asia before India. Whereas it hits Southeast Asia on May 1, it reaches Andaman and Nicobar Islands around May 15.
Elaborating on the reason why India attracts the south-west monsoon from
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Madagascar, B P Yadav, director, India
Meteorological Department (IMD) says:
"With summer tting over the subcontinent in May, the land starts heating up. The a/ocean surrounding
旁蒂克the subcontinent fails to heat up as fast
as the land. As the hot air over the
landmass ris, a low-pressure area is
formed. The low-pressure area draws massive amount of air from the high-pressure area over the a to fill the void.
The Somali jet stream brings moisture-laden winds from high-pressure area to
India. The winds hit India from a
south-west direction, hence the name."
Winds that gather moisture over Arabian Sea lash the Western Ghats (mountain ranges along the West coast of India)
where some areas receive an average rainfall of 2,000 mm. Winds that gather moisture over Bay of Bengal hit northeastern states by June 1. This further brings rain to West Bengal and Bihar. Both the streams merge over central India to power the monsoon towards Delhi and Jammu. However, by this time the winds have lost most of their moisture hence north Indian states receive less rain than coastal areas. The last place to be hit by
the south-west monsoon in India is west
Rajasthan where it does not reach before July 15. This is not the end. With the temperature dropping in September, a high-pressure
area is formed over Tibet known as "Tibetan High.” The anti-cyclone
movement over this area pushes the
winds coming from Bay of Bengal to
assume an easterly direction. Hence,
"Tibetan High" creates an easterly
tropical jet, which takes the winds back to the coast of Madagascar where it finally sinks into "Mascarenas High" — the place of its inception. South-West Summer Monsoon
The southwestern summer monsoons occur from June through September. The Great Indian Dert (Thar Dert) and adjoining areas of the northern and central Indian Subcontinent heats up too
much during the hot asons of summer. This caus a low pressure area over the northern and central Indian subcontinent. To fill up this void, the moisture-laden winds from the Indian Ocean rush in to the subcontinent. The winds, rich in moisture, are drawn towards the Himalayas, creating winds blowing storm clouds towards the subcontinent.
However the Himalayas act like a high wall and do not allow the winds to pass into Central Asia, forcing them to ri. With the gain in altitude of the clouds, the temperature drops and precipitation occurs. Some areas of the subcontinent receive up to 10,000 mm of rain. The southwest monsoon is generally expected to begin around the middle of June and dies down by September. The moisture-laden winds on reaching the southernmost point of the Indian
peninsula, due to its topology, become divided into two parts: • Arabian Sea Branch of the SW Monsoon • Bay of Bengal Branch of the SW Monsoon
The Arabian Sea Branch of the SW
Monsoon first hits the Western Ghats of the coastal state of Kerala, India and hence Kerala is the first state in India to receive rain from the South-West Monsoon. This branch of the monsoon moves northwards along the Western Ghats giving rain to the coastal areas
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west of the Western Ghats. It is to be noted that the eastern parts of the Western Ghats do not receive much rain from this monsoon as the wind does not cross the Western Ghats.
North-East Monsoon (Retreating Monsoon)
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. Thi
s caus the 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 North-East Monsoon or Retreating Monsoon.
While traveling towards the Indian Ocean, the dry cold wind picks up some moisture from the Bay of Bengal and pours it over peninsular India. Cities like Chennai, which get less rain from the South-West Monsoon, receives rain from the Retreating Monsoon. About 50% - 60% of the rain received by the state of Tamil Nadu is from the North-East Monsoon.
It is worth noting that North-East Monsoon (or the Retreating Monsoon) is not able to bring much rain as the South-West Monsoon.
Southwesterly Monsoon And Ancient Trade Patterns
Harappans were the first mariners from India who had maritime trade relations with countries outside India. They sailed up to the coast of Bahrain, Meluhha, Oman Peninsula, and Mesopotamia using
Monsoon winds and currents, but no evidence is available in this regard.
Greek and Roman mariners were able to reach the Indian coast to carry out extensive maritime trad
e with the help of monsoon winds. It is clear that the afarers were not able to e the flow of winds and currents, but felt that there are forces that assist in driving the ship faster than the normal movement. The u of monsoon winds and currents for maritime trade by mariners is less known
to all of us. Probably the knowledge of u of monsoon wind and current for maritime trade was only confined to sailors and mariners.mutually
It would not be an exaggeration to state that without the Southwesterly Monsoons the ancient trade with India would have not not developed and flourished. As described in the foregoing paragraphs the Southwesterly Monsoon winds blow in Southwesterly direction during the monsoon periods and in the Northwesterly direction in the other, this greatly aided the ancient Mariners to traver the Indian Ocean and the Arabian a to India and back making good u of the winds.
沈阳新航道Once the directional pattern of the Monsoon winds was known to Mariners they could effectively reduce the turn over time of their voyages to and fro to India. Prior to the knowledge of the winds, trans Indian Ocean - Arabian a voyages between Greece, Rome, Mesopotemia and India ud to take veral months. It was not practical to carry provisions more than that could be carried for a specified duration. Any delays in completing the voyages
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meant in aborting such trade voyages midway.
Maritime traders from Egypt, Greece and Rome ud to sail through the Red Sea, and along the coast of Oman, prior
to crossing the Arabian Sea to reach the Indian ports along the Western Coast. Once the Moonsoon winds were studied
by Hippalus, a voyage started from Red Sea during the summers (i.e the early monsoons of India) could be completed along a West coast port in India in about
基础护肤步骤40 days. This became possible by using the winds blowing towards the Indian Coast.
Similarly voyages from the Indian Coast
to the Mesopotemia, Egyptian Ports, if started in the post monsoon periods (around November) could be successfully completed in shorter periods using the Retreating Monsoon winds. It would have been surprising if the trade would have not incread and flourished, once the stumbling block of voyage time was greatly reduced !
The Arabs and the Portuge further started to trade with India. The voyages
of Vasco – da – Gama need no elaboration.
There have been evidences of incread trading activities in the period after Hippalus studied and recorded the Southwesterly Monsoons. Several ports developed along the West coast of India during this period. Evidences in form of Roman Coins and artefacts have been unearthed at such locations. Caskets for carrying Wine and Olive oil from Rome have been unearthed at Chaul - Raigad district, Neva – Ahmednagar district and Ter in Osmanabad district in Maharashtra (Western India).
A statue of the Roman Sea godess Podion, has been found in the hinterlands of Maharashtra in the city of Kolhapur. All the artefacts have been dated from a few centuries BC to the first few centuries AD. The findings certainly cannot be considered as coincidences, but in fact are the evidences of incread trading activities between India and the west.
Similar developments of ports took place along the Eastern coast of India. Explorations and excavations at the sites have yielded northern black polished ware (NBP), rouletted ware, knobbed ware, Red and Black ware, Roman and punch mark coins and mi-precious stone beads.
All the archaeological findings are traced to be dated as far as 2500 to 2000 BC, if not earlier.vacant
The afarers of India had knowledge about the a pertaining to weather, winds, currents, waves, and tides. Their obrvations were often correct and they succeeded in prenting a general picture of the physical conditions of the Arabian Sea, Bay of Bengal and Indian Ocean. Information on the early concepts is found in Pali, Sanskrit and Tamil literature and also archaeological excavations, numismatics and paintings. Trade Between India and Far East肖秀荣最后四套题
The Arab and Greek mariners t sail with the help of summer monsoon winds and were able to return during the winter monsoon, whereas mariners of Orissa t sail during the winter monsoon and returned during the summer monsoon.
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