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Dom Henrique of Portugal, Duke of Viseu, better known as Prince Henry the Navigator, was a central figure in the early days of the Portuguese Empire and in the 15th-century European maritime discoveries and maritime expansion. Through his administrative direction, he is regarded as the main initiator of what would be known as the Age of Discovery. Henry was the fourth child of King John I of Portugal, who founded the House of Aviz.
The Indian Ocean is the third-largest of the world's five oceanic divisions, covering 70,560,000 km2 (27,240,000 sq mi) or approx. 20% of the water on Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia to the east. To the south it is bounded by the Southern Ocean, or Antarctica, depending on the definition in use. Along its core, the Indian Ocean has large marginal, or regional seas, such as the Andaman Sea, the Arabian Sea, the Bay of Bengal, and the Laccadive Sea.
D. Vasco da Gama, 1st Count of Vidigueira, was a Portuguese explorer and nobleman who was the first European to reach India by sea.
The Silk Road was a network of Eurasian trade routes active from the second century BCE until the mid-15th century. Spanning over 6,400 km (4,000 mi), it played a central role in facilitating economic, cultural, political, and religious interactions between the Eastern and Western worlds. The name "Silk Road" was first coined in the late 19th century, but some 20th- and 21st-century historians instead prefer the term Silk Routes, on the grounds that it more accurately describes the intricate web of land and sea routes connecting Central, East, South, Southeast, and West Asia as well as East Africa and Southern Europe.
A monsoon 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 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.
El Niño–Southern Oscillation (ENSO) is a global climate phenomenon that emerges from variations in winds and sea surface temperatures over the tropical Pacific Ocean. Those variations have an irregular pattern but do have some semblance of cycles. The occurrence of ENSO is not predictable. It affects the climate of much of the tropics and subtropics, and has links (teleconnections) to higher-latitude regions of the world. The warming phase of the sea surface temperature is known as "El Niño" and the cooling phase as "La Niña". The Southern Oscillation is the accompanying atmospheric oscillation, which is coupled with the sea temperature change.
Wootz steel is a crucible steel characterized by a pattern of bands and high carbon content. These bands are formed by sheets of microscopic carbides within a tempered martensite or pearlite matrix in higher-carbon steel, or by ferrite and pearlite banding in lower-carbon steels. It was a pioneering steel alloy developed in southern India in the mid-1st millennium BC and exported globally.
Atmospheric circulation is the large-scale movement of air and together with ocean circulation is the means by which thermal energy is redistributed on the surface of the Earth. The Earth's atmospheric circulation varies from year to year, but the large-scale structure of its circulation remains fairly constant. The smaller-scale weather systems – mid-latitude depressions, or tropical convective cells – occur chaotically, and long-range weather predictions of those cannot be made beyond ten days in practice, or a month in theory.
The trade winds or easterlies are permanent east-to-west prevailing winds that flow in the Earth's equatorial region. The trade winds blow mainly from the northeast in the Northern Hemisphere and from the southeast in the Southern Hemisphere, strengthening during the winter and when the Arctic oscillation is in its warm phase. Trade winds have been used by captains of sailing ships to cross the world's oceans for centuries. They enabled European colonization of the Americas, and trade routes to become established across the Atlantic Ocean and the Pacific Ocean.
In meteorology, prevailing wind in a region of the Earth's surface is a surface wind that blows predominantly from a particular direction. The dominant winds are the trends in direction of wind with the highest speed over a particular point on the Earth's surface at any given time. A region's prevailing and dominant winds are the result of global patterns of movement in the Earth's atmosphere. In general, winds are predominantly easterly at low latitudes globally. In the mid-latitudes, westerly winds are dominant, and their strength is largely determined by the polar cyclone. In areas where winds tend to be light, the sea breeze/land breeze cycle is the most important cause of the prevailing wind; in areas which have variable terrain, mountain and valley breezes dominate the wind pattern. Highly elevated surfaces can induce a thermal low, which then augments the environmental wind flow.
The Walker circulation, also known as the Walker cell, is a conceptual model of the air flow in the tropics in the lower atmosphere (troposphere). According to this model, parcels of air follow a closed circulation in the zonal and vertical directions. This circulation, which is roughly consistent with observations, is caused by differences in heat distribution between ocean and land. In addition to motions in the zonal and vertical direction the tropical atmosphere also has considerable motion in the meridional direction as part of, for example, the Hadley Circulation.
Palakkad Gap or Palghat Gap is a low mountain pass in the Western Ghats between Coimbatore in the Indian state of Tamil Nadu and Palakkad in the state of Kerala. It has an average elevation of 140 metres (460 ft) with a width of 24–30 kilometres (15–19 mi). The pass is located between the Nilgiri Hills to the north and Anaimalai Hills to the south.
The Equatorial Counter Current is an eastward flowing, wind-driven current which extends to depths of 100–150 metres (330–490 ft) in the Atlantic, Indian, and Pacific Oceans. More often called the North Equatorial Countercurrent (NECC), this current flows west-to-east at about 3-10°N in the Atlantic, Indian Ocean and Pacific basins, between the North Equatorial Current (NEC) and the South Equatorial Current (SEC). The NECC is not to be confused with the Equatorial Undercurrent (EUC) that flows eastward along the equator at depths around 200 metres (660 ft) in the western Pacific rising to 100 metres (330 ft) in the eastern Pacific.
The Golden Wind is a historical novel by American writer L. Sprague de Camp, first published in 1969, and telling the story of the Egyptian Greek seafarers Eudoxus of Cyzicus and Hippalus, who were the first in the Graeco-Roman world to travel by sea from Egypt to India in around 118 BCE.
A western disturbance is an extratropical storm originating in the Mediterranean region that brings sudden winter rain to the northwestern parts of the Indian subcontinent, which extends as east as up to northern parts of Bangladesh and South eastern Nepal. It is a non-monsoonal precipitation pattern driven by the westerlies. The moisture in these storms usually originates over the Mediterranean Sea, the Caspian Sea and the Black Sea. Extratropical storms are a global phenomena with moisture usually carried in the upper atmosphere, unlike their tropical counterparts where the moisture is carried in the lower atmosphere. In the case of the Indian subcontinent, moisture is sometimes shed as rain when the storm system encounters the Himalayas. Western disturbances are more frequent and stronger in the winter season.
The Indian Monsoon Current refers to the seasonally varying ocean current regime found in the tropical regions of the northern Indian Ocean. During winter, the flow of the upper ocean is directed westward from near the Indonesian Archipelago to the Arabian Sea. During the summer, the direction reverses, with eastward flow extending from Somalia into the Bay of Bengal. These variations are due to changes in the wind stress associated with the Indian monsoon. The seasonally reversing open ocean currents that pass south of India are referred to as the Winter Monsoon Current and the Summer Monsoon Current. The cold Somali Current, which is strongly linked to the Indian monsoon, is also discussed in this article.
The first documented relations between Ancient India and Ancient Rome occurred during the reign of Augustus, the first Roman Emperor.
The Maritime history of Odisha, known as Kalinga in ancient times, started much before 800 BC according to early sources. The people of this region of eastern India along the coast of the Bay of Bengal sailed up and down the Indian coast, and travelled to Indo China and throughout Maritime Southeast Asia, introducing elements of their culture to the people with whom they traded. The 6th century Manjusrimulakalpa mentions the Bay of Bengal as Kalingodra and in ancient Classical India, the Bay of Bengal was known as Kalinga Sagar, indicating the importance of Kalinga in the maritime trade. The old traditions are still celebrated in the annual Boita Bandana festival including its major celebration at Cuttack on the banks of Mahanadi river called Bali Jatra, and are held for seven days in October-November at various coastal districts, most famous at Cuttack though.
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 Tropical Atlantic SST Dipole refers to a cross-equatorial sea surface temperature (SST) pattern that appears dominant on decadal timescales. It has a period of about 12 years, with the SST anomalies manifesting their most pronounced features around 10–15 degrees of latitude off of the Equator. It is also referred to as the interhemispheric SST gradient or the Meridional Atlantic mode.
References
- ↑ W. H. Ingrams, "The Hadhramaut: Present and Future", The Geographical Journal, Vol. 92, No. 4 (Oct., 1938), pp. 289-311
- ↑ Donald Ferguson, "Letters from Raja Sinha II to Dutch", in The Journal of the Ceylon Branch of the Royal Asiatic Society of Great Britain & Ireland, Vol. 21, No. 62 (1909), p 273.
- Obeyesekere, G. (1984) The Cult of the Goddess Pattini. Chicago: University of Chicago Press; p. 530
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