SUMMARY / RELATED TOPICS

Jet stream

Jet streams are fast flowing, meandering air currents in the atmospheres of some planets, including Earth. On Earth, the main jet streams are located near the altitude of the tropopause and are westerly winds, their paths have a meandering shape. Jet streams may start, split into two or more parts, combine into one stream, or flow in various directions including opposite to the direction of the remainder of the jet; the strongest jet streams are the polar jets, at 9–12 km above sea level, the higher altitude and somewhat weaker subtropical jets at 10–16 km. The Northern Hemisphere and the Southern Hemisphere each have a subtropical jet; the northern hemisphere polar jet flows over the middle to northern latitudes of North America and Asia and their intervening oceans, while the southern hemisphere polar jet circles Antarctica all year round. The southern hemisphere mid-latitude jet is a narrow band of strong winds stretching from the Earth's surface to the top of the troposphere at about 12 km increasing in strength with height.

Jet streams are the product of two factors: the atmospheric heating by solar radiation that produces the large-scale Polar and Hadley circulation cells, the action of the Coriolis force acting on those moving masses. The Coriolis force is caused by the planet's rotation on its axis. On other planets, internal heat rather than solar heating drives their jet streams; the Polar jet stream forms near the interface of the Ferrel circulation cells. Other jet streams exist. During the Northern Hemisphere summer, easterly jets can form in tropical regions where dry air encounters more humid air at high altitudes. Low-level jets are typical of various regions such as the central United States. There are jet streams in the thermosphere. Meteorologists use; the main commercial relevance of the jet streams is in air travel, as flight time can be affected by either flying with the flow or against, which results in significant fuel and time cost savings for airlines. The airlines work to fly'with' the jet stream for this reason.

Dynamic North Atlantic Tracks are one example of how airlines and air traffic control work together to accommodate the jet stream and winds aloft that results in the maximum benefit for airlines and other users. Clear-air turbulence, a potential hazard to aircraft passenger safety, is found in a jet stream's vicinity, but it does not create a substantial alteration on flight times. After the 1883 eruption of the Krakatoa volcano, weather watchers tracked and mapped the effects on the sky over several years, they labelled the phenomenon the "equatorial smoke stream". In the 1920s, a Japanese meteorologist, Wasaburo Oishi, detected the jet stream from a site near Mount Fuji, he tracked pilot balloons known as pibals, as they rose into the atmosphere. Oishi's work went unnoticed outside Japan because it was published in Esperanto. American pilot Wiley Post, the first man to fly around the world solo in 1933, is given some credit for discovery of jet streams. Post invented a pressurized suit. In the year before his death, Post made several attempts at a high-altitude transcontinental flight, noticed that at times his ground speed exceeded his air speed.

German meteorologist Heinrich Seilkopf is credited with coining a special term, Strahlströmung, for the phenomenon in 1939. Many sources credit real understanding of the nature of jet streams to regular and repeated flight-path traversals during World War II. Flyers noticed westerly tailwinds in excess of 160 km/h in flights, for example, from the US to the UK. In 1944 a team of American meteorologists in Guam, including Reid Bryson, had enough observations to forecast high west winds that would slow bombers going to Japan. Polar jet streams are located near the 250 hPa pressure level, or seven to twelve kilometres above sea level, while the weaker subtropical jet streams are much higher, between 10 and 16 kilometres. Jet streams wander laterally and have large changes in their altitude; the jet streams form near breaks in the tropopause, at the transitions between the Polar and Hadley circulation cells, whose circulation, with the Coriolis force acting on those masses, drives the jet streams.

The Polar jets, at lower altitude, intruding into mid-latitudes affect weather and aviation. The polar jet stream is most found between latitudes 30° and 60°, while the subtropical jet streams are located close to latitude 30°; these two jets merge at some times, while at other times they are well separated. The northern Polar jet stream is said to "follow the sun" as it migrates northward as that hemisphere warms, southward again as it cools; the width of a jet stream is a few hundred kilometres or miles and its vertical thickness less than five kilometres. Jet streams are continuous over long distances, but discontinuities are common; the path of the jet has a meandering shape, these meanders themselves propagate eastward, at lower speeds than that of the actual wind within the flow. Each large meander, or wave, within the jet stream is known as a Rossby wave. Rossby waves are caused by changes in the Coriolis effect

Madurai Nayak dynasty

The Madurai Nayaks were Telugu rulers from around 1529 until 1736, of a region comprising most of modern-day Tamil Nadu, with Madurai as their capital. The Nayak reign was an era noted for its achievement in arts and administrative reforms, revitalization of temples ransacked by the Delhi Sultans, inauguration of a unique architectural style; the dynasty, belonging to the Balija social group, consisted of 13 rulers, of whom 9 were kings, 2 were queens, 2 were joint-kings. The most notable of these were the king, Tirumala Nayaka, the queen, Rani Mangammal. Foreign trade was conducted with the Dutch and the Portuguese, as the British and the French had not yet made inroads in the region. Early in the 14th century, a dispute arose over the succession to the Pandya throne. One claimant appealed for help to emperor Ala-ud-din of Delhi, who dispatched his general, Malik Kafur, in 1310. Malik Kafur marched south, ransacking kingdoms on the way and causing enormous changes to the political configuration of central and Southern India.

He marched into Madurai, sacking the town, paralysing trade, suppressing public worship, making civilian life miserable. The great Meenakshi temple with its fourteen towers was pulled down, destroying the nearby streets and buildings, leaving only the two shrines of Sundaresvara and Meenakshi intact; the events are controversial: as another account describes them...the Deccan was soon to feel the force of Islam, the master of Northern India. In the reign of the able sultan of Delhi, Ala-ud-din Khalji, a series of brilliant raids, led by the eunuch general Malik Kafur, a converted Hindu, crushed the Deccan kingdoms, for a time a sultanate was set up in Madurai, in the extreme south. Malik Kafur returned to Delhi following these events; the Pandyas protested the invasion. The weakness of the Pandya regime caused the neighboring Chera ruler to invade and defeat the Pandya ruler, he crowned himself in 1313; this was followed by a Chera occupation. However, the Chera occupation was transitory. A Sultan dynasty was soon re-established at Madurai, ruling Madurai and South Arcot, for the next 48 years, first as feudatories of the Delhi Sultanate and as independent monarchies.

In 1333, during the rule of Muhammad bin Tughlaq, Jalal-ud-Din Ahsan Khan declared independence from the Delhi sultanate and ruled the area until he was killed by one of his officers in 1339. Alaud din Udauji Shah soon met with the same fate. Qutb ud din Firoz was killed in about forty days. Giyaz uddin Muhammad Damghan ascended the throne in 1340 and married a daughter of Ahasan Shah. Ibn Batuta visited Madura during his reign and he testifies to his atrocious behaviour, he was defeated by the Hoysala Veera Ballala, but captured and killed Ballala. He died in 1344. Nazir ud din Mahmud Damghan, Adl Shah, Faqr ud din Mubarak and Ala ud din Sikandar followed him in succession; when Sikandar was defeated by Bukka in 1377, the region became part of the Vijayanagara Empire. Sultan rule of the region was overthrown in 1377 by the new Hindu kingdom of Vijayanagara, founded at Hampi. For the next two centuries, this empire withstood repeated Sultan invasions from the north. Kampana Udaiyar, a Vijayanagara prince and an agent of Bukka Raya who served as a General in the Vijayanagara army, marched into Madurai in 1372.

He expelled the sultan out of Madurai and started a dynasty, subordinate to the court of Vijayanagara that lasted until 1404. The immediate effect of this victory was the reopening of the Vishnu temples; the rule was continued by Vijayanagar-appointed governors. King Krishna Devaraya, the greatest ruler of the Vijayanagara dynasty, exercised close control over this part of his empire. After ruling for sometime, Kampana Udaiyar left his son Embana Udaiyar in charge of Madurai, succeeded by his brother-in-law Porkasa Udeiyar. Around 1404, Porkasa Udaiyar was succeeded by a man named Lakkana Nayakkan, thus bringing the dynastic rule of Kampana Udaiyar to an end. Lekkina Nayakkan appointed Vira Parakkrama Pandyan to rule Madurai, but soon after Vira Parakkrama Pandyan revolted to become independent, he was dismissed and chased away to Chera country, Lantana Nayaka jointly ruled Madurai with another Nayaka named Mathanan until 1451. Between 1451 and 1499, the Madurai regions were ruled by four persons brought by Lakkana Nayakkan whom he declared to be of true Pandya stock.

The four persons were Sundara Tol Maha Vilivanathi Rayar, Kaleiyar Somanar, Anjatha Perumal and Muttarasa Thirumalai Maha Vilivanathi Rayar. A commentator, James Nelson, mentions that all the four persons belonged to the same family, were illegitimate sons of a petty Pandyan chieftain. However, all four of them enjoyed kingly powers for 48 years from 1451 to around 1499 and are said to have built four gopurams of the Madurai temple, destroyed by the Mohemmadans. After the ouster by the Sultans, the Vilivanathis are said to have retired; the existing four gopurams were built by the following: East Gopuram was built by Pandiya King Maravarman Sundara Pandiyan in 1216. This is the oldest of all Gopurams. West Gopuram was built by Parakirama Pandiyan between 1315–1347; this is the second gopuram built without steps to bring goods inside. South Gopuram was built by Sevvandhi Moorthy Chettiar of Srimalai in 1559. North gopuram was built by Krishna Veerappa Nayakkar between 1564–1572, left without completion hence it is still called Mottai gopuram meaning Flat tower.

Prior to the formation of the Na

Rush Lake (Tooele County, Utah)

Rush Lake is a shallow saline lake in Tooele County in the U. S. state of Utah. It is a remnant of Lake Bonneville, an ancient postglacial inland sea that covered much of the western United States during the Ice Ages; the lake is a natural impoundment of a stream. Rush Lake varies in size, evaporating at about 2 feet per year, although occasional floods refill the lake; the average surface elevation is 4,951 feet. The lake is located in a broad valley named Rush Valley near the town of Stockton and several miles south of Tooele, is fed by snowmelt from six mountain ranges; these are the Sheeprock Mountains in the south, the East Tintic Mountains to the southeast, the Oquirrh Mountains to the east, South Mountain to the north, the Stansbury Mountains to the northwest and west, the Onaqui Mountains to the southwest. The runoff from these mountain regions create only intermittent surface flow to the lake, but does reach it via groundwater seepage; the highest point in the watershed is Lowe Peak, at 10,590 feet.

The outflow consists of evaporation, a small amount seeps through the sandspit that impounds it from the main Great Salt Lake valley. The lake was isolated from Lake Bonneville 15,000-17,000 years ago after evaporation lowered the lake level to below the natural Stockton Bar barrier between Rush Valley and Tooele Valley. During the ice ages, Rush Valley was one of many arms of Lake Bonneville. After Bonneville dried up, Rush Valley contained several pluvial lakes – Shambip and Rush – of which only Rush Lake remains today. Two major vegetation communities inhabit the Rush Lake watershed; these are pinyon-juniper. The former is found in lower elevations and the valley floor, the latter is found at higher elevations on the mountains along with other forms of alpine vegetation; the average annual precipitation is 10 to 40 inches, the annual frost-free season surrounding the lake ranges from 100 to 140 days. Cattle and sheep rangelands take up most of the catchment area; the lake is inhabited by several different species of fish.

These include, in order of abundance, Utah chub, green sunfish, largemouth bass, channel catfish, yellow perch, black crappie, black bullhead. The lake has not been stocked with fish since 1988, when 71,000 largemouth bass fry were released in the lake. Cabrero, Alex. "Kiteboarder dies on Rush Lake". KSL.com. The Rush Lake Legend Kiteboarding on Rush Lake in 2011