A nor'easter is a macro-scale extratropical cyclone in the western North Atlantic ocean. The name derives from the direction of the strongest winds that will be hitting an eastern seaboard of the northern hemisphere: as a cyclonic air mass rotates counterclockwise, winds tend to blow northeast-to-southwest over the region covered by the northwest quadrant of the cyclone. Use of the term in North America is associated with storms that impact the north Atlantic areas of the United States, in the Atlantic Provinces of Canada; such storms originate as a low-pressure area that forms within 100 miles of the shore between North Carolina and Massachusetts. The precipitation pattern is similar to that of other extratropical storms. Nor'easters are accompanied by heavy rain or snow, can cause severe coastal flooding, coastal erosion, hurricane-force winds, or blizzard conditions. Nor'easters are most intense during winter in New England and Atlantic Canada, they thrive on converging air masses—the cold polar air mass and the warmer air over the water—and are more severe in winter when the difference in temperature between these air masses is greater.
Nor'easters tend to develop most and most powerfully between the months of November and March, although they can develop during other parts of the year as well. The susceptible regions are impacted by nor'easters a few times each winter; the term nor'easter came to American English by way of British English. The earliest recorded uses of the contraction nor in combinations such as nor'-east and nor-nor-west, as reported by the Oxford English Dictionary, date to the late 16th century, as in John Davis's 1594 The Seaman's Secrets: "Noreast by North raiseth a degree in sayling 24 leagues." The spelling appears, for instance, on a compass card published in 1607. Thus, the manner of pronouncing from memory the 32 points of the compass, known in maritime training as "boxing the compass", is described by Ansted with pronunciations "Nor'east," "Nor' Nor'-east," "Nor'east b' east," and so forth. According to the OED, the first recorded use of the term "nor'easter" occurs in 1836 in a translation of Aristophanes.
The term "nor'easter" developed from the historical spellings and pronunciations of the compass points and the direction of wind or sailing. As noted in a January 2006 editorial by William Sisson, editor of Soundings magazine, use of "nor'easter" to describe the storm system is common along the U. S. East Coast, yet it has been asserted by linguist Mark Liberman that "nor'easter" as a contraction for "northeaster" has no basis in regional New England dialect. He describes nor'easter as a "fake" word. However, this view neglects the little-known etymology and the historical maritime usage described above. 19th-century Downeast mariners pronounced the compass point "north northeast" as "no'nuth-east", so on. For decades, Edgar Comee, of Brunswick, waged a determined battle against use of the term "nor'easter" by the press, which usage he considered "a pretentious and altogether lamentable affectation" and "the odious loathsome, practice of landlubbers who would be seen as salty as the sea itself".
His efforts, which included mailing hundreds of postcards, were profiled, just before his death at the age of 88, in The New Yorker. Despite the efforts of Comee and others, use of the term continues by the press. According to Boston Globe writer Jan Freeman, "from 1975 to 1980, journalists used the nor’easter spelling only once in five mentions of such storms. University of Pennsylvania linguistics professor Mark Liberman has pointed out that while the Oxford English Dictionary cites examples dating back to 1837, these examples represent the contributions of a handful of non-New England poets and writers. Liberman posits that "nor'easter" may have been a literary affectation, akin to "e'en" for "even" and "th'only" for "the only", an indication in spelling that two syllables count for only one position in metered verse, with no implications for actual pronunciation. However, despite these assertions, the term can be found in the writings of New Englanders, was used by the press in the 19th century.
The Hartford Times reported on a storm striking New York in December 1839, observed, "We Yankees had a share of this same "noreaster," but it was quite moderate in comparison to the one of the 15h inst." Thomas Bailey Aldrich, in his semi-autobiographical work The Story of a Bad Boy, wrote "We had had several slight flurries of hail and snow before, but this was a regular nor'easter". In her story "In the Gray Goth" Elizabeth Stuart Phelps Ward wrote "...and there was snow in the sky now, setting in for a regular nor'easter". John H. Tice, in A new system of meteorology, designed for schools and private students, wrote "During this battle, the dreaded and destructive Northeaster rages over the New England, the Middle States, southward. No nor'easter occurs except when there is a high barometer headed off and driven down upon Nova Scotia and Lower Canada."Usage existed into the 20th century in the form of: Current event description, as the Publication Committee of the New York Charity Organization Society wrote in Charities and the commons: a weekly journal of philanthropy and social advance, Volume 19: "In spite of a heavy "nor'easter," the worst that has visited the New England coast in years, the hall was crowded."
Historical reference, as used by Mary Rogers Bangs in Old Cape Cod: "In December of 1778, the Federal brig General Arnold, Magee
A tropical cyclone is a rotating storm system characterized by a low-pressure center, a closed low-level atmospheric circulation, strong winds, a spiral arrangement of thunderstorms that produce heavy rain. Depending on its location and strength, a tropical cyclone is referred to by different names, including hurricane, tropical storm, cyclonic storm, tropical depression, cyclone. A hurricane is a tropical cyclone that occurs in the Atlantic Ocean and northeastern Pacific Ocean, a typhoon occurs in the northwestern Pacific Ocean. "Cyclone" refers to their winds moving in a circle, whirling round their central clear eye, with their winds blowing counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. The opposite direction of circulation is due to the Coriolis effect. Tropical cyclones form over large bodies of warm water, they derive their energy through the evaporation of water from the ocean surface, which recondenses into clouds and rain when moist air rises and cools to saturation.
This energy source differs from that of mid-latitude cyclonic storms, such as nor'easters and European windstorms, which are fueled by horizontal temperature contrasts. Tropical cyclones are between 100 and 2,000 km in diameter; the strong rotating winds of a tropical cyclone are a result of the conservation of angular momentum imparted by the Earth's rotation as air flows inwards toward the axis of rotation. As a result, they form within 5° of the equator. Tropical cyclones are unknown in the South Atlantic due to a strong wind shear and a weak Intertropical Convergence Zone; the African easterly jet and areas of atmospheric instability which give rise to cyclones in the Atlantic Ocean and Caribbean Sea, along with the Asian monsoon and Western Pacific Warm Pool, are features of the Northern Hemisphere and Australia. Coastal regions are vulnerable to the impact of a tropical cyclone, compared to inland regions; the primary energy source for these storms is warm ocean waters, therefore these forms are strongest when over or near water, weaken quite over land.
Coastal damage may be caused by strong winds and rain, high waves, storm surges, the potential of spawning tornadoes. Tropical cyclones draw in air from a large area—which can be a vast area for the most severe cyclones—and concentrate the precipitation of the water content in that air into a much smaller area; this continual replacement of moisture-bearing air by new moisture-bearing air after its moisture has fallen as rain, which may cause heavy rain and river flooding up to 40 kilometres from the coastline, far beyond the amount of water that the local atmosphere holds at any one time. Though their effects on human populations are devastating, tropical cyclones can relieve drought conditions, they carry heat energy away from the tropics and transport it toward temperate latitudes, which may play an important role in modulating regional and global climate. Tropical cyclones are areas of low pressure in the troposphere, with the largest pressure perturbations occurring at low altitudes near the surface.
On Earth, the pressures recorded at the centers of tropical cyclones are among the lowest observed at sea level. The environment near the center of tropical cyclones is warmer than the surroundings at all altitudes, thus they are characterized as "warm core" systems; the near-surface wind field of a tropical cyclone is characterized by air rotating around a center of circulation while flowing radially inwards. At the outer edge of the storm, air may be nearly calm; as air flows radially inward, it begins to rotate cyclonically in order to conserve angular momentum. At an inner radius, air begins to ascend to the top of the troposphere; this radius is coincident with the inner radius of the eyewall, has the strongest near-surface winds of the storm. Once aloft, air flows away from the storm's center; the mentioned processes result in a wind field, nearly axisymmetric: Wind speeds are low at the center, increase moving outwards to the radius of maximum winds, decay more with radius to large radii.
However, the wind field exhibits additional spatial and temporal variability due to the effects of localized processes, such as thunderstorm activity and horizontal flow instabilities. In the vertical direction, winds are strongest near the surface and decay with height within the troposphere. At the center of a mature tropical cyclone, air sinks rather than rises. For a sufficiently strong storm, air may sink over a layer deep enough to suppress cloud formation, thereby creating a clear "eye". Weather in the eye is calm and free of clouds, although the sea may be violent; the eye is circular in shape, is 30–65 km in diameter, though eyes as small as 3 km and as large as 370 km have been observed. The cloudy outer edge of the eye is called the "eyewall"; the eyewall expands outward with height, resembling an arena foo
A firestorm is a conflagration which attains such intensity that it creates and sustains its own wind system. It is most a natural phenomenon, created during some of the largest bushfires and wildfires. Although the term has been used to describe certain large fires, the phenomenon's determining characteristic is a fire with its own storm-force winds from every point of the compass; the Black Saturday bushfires and the Great Peshtigo Fire are possible examples of forest fires with some portion of combustion due to a firestorm, as is the Great Hinckley Fire. Firestorms have occurred in cities as a deliberate effect of targeted explosives, such as occurred as a result of the aerial firebombings of Hamburg, firebombing of Tokyo and the atomic bombing of Hiroshima. A firestorm is created as a result of the stack effect as the heat of the original fire draws in more and more of the surrounding air; this draft can be increased if a low-level jet stream exists over or near the fire. As the updraft mushrooms, strong inwardly-directed gusty winds develop around the fire, supplying it with additional air.
This would seem to prevent the firestorm from spreading on the wind, but the tremendous turbulence created may cause the strong surface inflow winds to change direction erratically. Firestorms resulting from the bombardment of urban areas in the Second World War were confined to the areas seeded with incendiary devices, the firestorm did not appreciably spread outward. A firestorm may develop into a mesocyclone and induce true tornadoes/fire whirls; this occurred with the 2002 Durango fire, with the much greater Peshtigo Fire. The greater draft of a firestorm draws in greater quantities of oxygen, which increases combustion, thereby substantially increasing the production of heat; the intense heat of a firestorm manifests as radiated heat, which may ignite flammable material at a distance ahead of the fire itself. This serves to expand the area and the intensity of the firestorm. Violent, erratic wind drafts suck movables into the fire and as is observed with all intense conflagrations, radiated heat from the fire can melt asphalt, some metals, glass, turn street tarmac into flammable hot liquid.
The high temperatures ignite anything that might burn, until the firestorm runs low on fuel. A firestorm does not appreciably ignite material at a distance ahead of itself. During the formation of a firestorm many fires merge to form a single convective column of hot gases rising from the burning area and strong, fire-induced, radial winds are associated with the convective column, thus the fire front is stationary and the outward spread of fire is prevented by the in-rushing wind. A firestorm is characterized by strong to gale-force winds blowing toward the fire, everywhere around the fire perimeter, an effect, caused by the buoyancy of the rising column of hot gases over the intense mass fire, drawing in cool air from the periphery; these winds from the perimeter blow the fire brands into the burning area and tend to cool the unignited fuel outside the fire area so that ignition of material outside the periphery by radiated heat and fire embers is more difficult, thus limiting fire spread.
At Hiroshima, this inrushing to feed the fire is said to have prevented the firestorm perimeter from expanding, thus the firestorm was confined to the area of the city damaged by the blast. Large wildfire conflagrations are distinct from firestorms if they have moving fire fronts which are driven by the ambient wind and do not develop their own wind system like true firestorms. Furthermore, non-firestorm conflagrations can develop from a single ignition, whereas firestorms have only been observed where large numbers of fires are burning over a large area, with the important caveat that the density of burning fires needs to be above a critical threshold for a firestorm to form; the high temperatures within the firestorm zone ignite most everything that might burn, until a tipping point is reached, that is, upon running low on fuel, which occurs after the firestorm has consumed so much of the available fuel within the firestorm zone that the necessary fuel density required to keep the firestorm's wind system active drops below the threshold level, at which time the firestorm breaks up into isolated conflagrations.
In Australia, the prevalence of eucalyptus trees that have oil in their leaves results in forest fires that are noted for their tall and intense flame front. Hence the bush fires appear more as a firestorm than a simple forest fire. Sometimes, emission of combustible gases from swamps has a similar effect. For instance, methane explosions enforced the Peshtigo Fire. Firestorms will produce hot buoyant smoke clouds of water vapor that will form condensation clouds as it enters the cooler upper atmosphere, generating what is known as pyrocumulus clouds or, if large enough, pyrocumulonimbus clouds. For example, the black rain that began to fall 20 minutes after the atomic bombing of Hiroshima produced in total 5–10
In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls under gravity. The main forms of precipitation include drizzle, sleet, snow and hail. Precipitation occurs when a portion of the atmosphere becomes saturated with water vapor, so that the water condenses and "precipitates", thus and mist are not precipitation but suspensions, because the water vapor does not condense sufficiently to precipitate. Two processes acting together, can lead to air becoming saturated: cooling the air or adding water vapor to the air. Precipitation forms as smaller droplets coalesce via collision with other rain drops or ice crystals within a cloud. Short, intense periods of rain in scattered locations are called "showers."Moisture, lifted or otherwise forced to rise over a layer of sub-freezing air at the surface may be condensed into clouds and rain. This process is active when freezing rain occurs. A stationary front is present near the area of freezing rain and serves as the foci for forcing and rising air.
Provided necessary and sufficient atmospheric moisture content, the moisture within the rising air will condense into clouds, namely stratus and cumulonimbus. The cloud droplets will grow large enough to form raindrops and descend toward the Earth where they will freeze on contact with exposed objects. Where warm water bodies are present, for example due to water evaporation from lakes, lake-effect snowfall becomes a concern downwind of the warm lakes within the cold cyclonic flow around the backside of extratropical cyclones. Lake-effect snowfall can be locally heavy. Thundersnow is possible within lake effect precipitation bands. In mountainous areas, heavy precipitation is possible where upslope flow is maximized within windward sides of the terrain at elevation. On the leeward side of mountains, desert climates can exist due to the dry air caused by compressional heating. Most precipitation is caused by convection; the movement of the monsoon trough, or intertropical convergence zone, brings rainy seasons to savannah climes.
Precipitation is a major component of the water cycle, is responsible for depositing the fresh water on the planet. 505,000 cubic kilometres of water falls as precipitation each year. Given the Earth's surface area, that means the globally averaged annual precipitation is 990 millimetres, but over land it is only 715 millimetres. Climate classification systems such as the Köppen climate classification system use average annual rainfall to help differentiate between differing climate regimes. Precipitation may occur on other celestial bodies, e.g. when it gets cold, Mars has precipitation which most takes the form of frost, rather than rain or snow. Precipitation is a major component of the water cycle, is responsible for depositing most of the fresh water on the planet. 505,000 km3 of water falls as precipitation each year, 398,000 km3 of it over the oceans. Given the Earth's surface area, that means the globally averaged annual precipitation is 990 millimetres. Mechanisms of producing precipitation include convective and orographic rainfall.
Convective processes involve strong vertical motions that can cause the overturning of the atmosphere in that location within an hour and cause heavy precipitation, while stratiform processes involve weaker upward motions and less intense precipitation. Precipitation can be divided into three categories, based on whether it falls as liquid water, liquid water that freezes on contact with the surface, or ice. Mixtures of different types of precipitation, including types in different categories, can fall simultaneously. Liquid forms of precipitation include drizzle. Rain or drizzle that freezes on contact within a subfreezing air mass is called "freezing rain" or "freezing drizzle". Frozen forms of precipitation include snow, ice needles, ice pellets and graupel; the dew point is the temperature to which a parcel must be cooled in order to become saturated, condenses to water. Water vapor begins to condense on condensation nuclei such as dust and salt in order to form clouds. An elevated portion of a frontal zone forces broad areas of lift, which form clouds decks such as altostratus or cirrostratus.
Stratus is a stable cloud deck which tends to form when a cool, stable air mass is trapped underneath a warm air mass. It can form due to the lifting of advection fog during breezy conditions. There are four main mechanisms for cooling the air to its dew point: adiabatic cooling, conductive cooling, radiational cooling, evaporative cooling. Adiabatic cooling occurs when air expands; the air can rise due to convection, large-scale atmospheric motions, or a physical barrier such as a mountain. Conductive cooling occurs when the air comes into contact with a colder surface by being blown from one surface to another, for example from a liquid water surface to colder land. Radiational cooling occurs due to the emission of infrared radiation, either by the air or by the surface underneath. Evaporative cooling occurs when moisture is added to the air through evaporation, which forces the air temperature to cool to its wet-bulb temperature, or until it reaches saturation; the main ways water vapor is added to the air are: wind convergence into areas of upward motion, precipitation or virga falling from above, daytime heating evaporating water from the surface of oceans, water bodies or wet lan
Nature, in the broadest sense, is the natural, physical, or material world or universe. "Nature" can refer to the phenomena of the physical world, to life in general. The study of nature is a large, part of science. Although humans are part of nature, human activity is understood as a separate category from other natural phenomena; the word nature is derived from the Latin word natura, or "essential qualities, innate disposition", in ancient times meant "birth". Natura is a Latin translation of the Greek word physis, which related to the intrinsic characteristics that plants and other features of the world develop of their own accord; the concept of nature as a whole, the physical universe, is one of several expansions of the original notion. This usage continued during the advent of modern scientific method in the last several centuries. Within the various uses of the word today, "nature" refers to geology and wildlife. Nature can refer to the general realm of living plants and animals, in some cases to the processes associated with inanimate objects—the way that particular types of things exist and change of their own accord, such as the weather and geology of the Earth.
It is taken to mean the "natural environment" or wilderness—wild animals, forest, in general those things that have not been altered by human intervention, or which persist despite human intervention. For example, manufactured objects and human interaction are not considered part of nature, unless qualified as, for example, "human nature" or "the whole of nature"; this more traditional concept of natural things which can still be found today implies a distinction between the natural and the artificial, with the artificial being understood as that, brought into being by a human consciousness or a human mind. Depending on the particular context, the term "natural" might be distinguished from the unnatural or the supernatural. Earth is the only planet known to support life, its natural features are the subject of many fields of scientific research. Within the solar system, it is third closest to the sun, its most prominent climatic features are its two large polar regions, two narrow temperate zones, a wide equatorial tropical to subtropical region.
Precipitation varies with location, from several metres of water per year to less than a millimetre. 71 percent of the Earth's surface is covered by salt-water oceans. The remainder consists of continents and islands, with most of the inhabited land in the Northern Hemisphere. Earth has evolved through geological and biological processes that have left traces of the original conditions; the outer surface is divided into several migrating tectonic plates. The interior remains active, with a thick layer of plastic mantle and an iron-filled core that generates a magnetic field; this iron core is composed of a solid inner phase, a fluid outer phase. Convective motion in the core generates electric currents through dynamo action, these, in turn, generate the geomagnetic field; the atmospheric conditions have been altered from the original conditions by the presence of life-forms, which create an ecological balance that stabilizes the surface conditions. Despite the wide regional variations in climate by latitude and other geographic factors, the long-term average global climate is quite stable during interglacial periods, variations of a degree or two of average global temperature have had major effects on the ecological balance, on the actual geography of the Earth.
Geology is the study of the solid and liquid matter that constitutes the Earth. The field of geology encompasses the study of the composition, physical properties and history of Earth materials, the processes by which they are formed and changed; the field is a major academic discipline, is important for mineral and hydrocarbon extraction, knowledge about and mitigation of natural hazards, some Geotechnical engineering fields, understanding past climates and environments. The geology of an area evolves through time as rock units are deposited and inserted and deformational processes change their shapes and locations. Rock units are first emplaced either by deposition onto the surface or intrude into the overlying rock. Deposition can occur when sediments settle onto the surface of the Earth and lithify into sedimentary rock, or when as volcanic material such as volcanic ash or lava flows, blanket the surface. Igneous intrusions such as batholiths, laccoliths and sills, push upwards into the overlying rock, crystallize as they intrude.
After the initial sequence of rocks has been deposited, the rock units can be deformed and/or metamorphosed. Deformation occurs as a result of horizontal shortening, horizontal extension, or side-to-side motion; these structural regimes broadly relate to convergent boundaries, divergent boundaries, transform boundaries between tectonic plates. Earth is estimated to have formed 4.54 billion years ago from the solar nebula, along with the Sun and other planets. The moon formed 20 million years later. Molten, the outer layer of the Earth cooled, resulting in the solid crust. Outgassing and volcanic activity produced the primordial atmosphere. Condensing water vapor, most or all of which came from ice delivered by comets, produced the oceans and other water sources; the energetic chemistry is believed to have produced a self-replicat
Summer is the hottest of the four temperate seasons, falling after spring and before autumn. At the summer solstice, the days are longest and the nights are shortest, with day length decreasing as the season progresses after the solstice; the date of the beginning of summer varies according to climate and culture. When it is summer in the Northern Hemisphere, it is winter in the Southern Hemisphere, vice versa. From an astronomical view, the equinoxes and solstices would be the middle of the respective seasons, but sometimes astronomical summer is defined as starting at the solstice, the time of maximal insolation identified with the 21st day of June or December. A variable seasonal lag means that the meteorological center of the season, based on average temperature patterns, occurs several weeks after the time of maximal insolation; the meteorological convention is to define summer as comprising the months of June and August in the northern hemisphere and the months of December and February in the southern hemisphere.
Under meteorological definitions, all seasons are arbitrarily set to start at the beginning of a calendar month and end at the end of a month. This meteorological definition of summer aligns with the viewed notion of summer as the season with the longest days of the year, in which daylight predominates; the meteorological reckoning of seasons is used in Australia, Denmark and Japan. It is used by many in the United Kingdom. In Ireland, the summer months according to the national meteorological service, Met Éireann, are June and August. However, according to the Irish Calendar, summer ends on 1 August. School textbooks in Ireland follow the cultural norm of summer commencing on 1 May rather than the meteorological definition of 1 June. Days continue to lengthen from equinox to solstice and summer days progressively shorten after the solstice, so meteorological summer encompasses the build-up to the longest day and a diminishing thereafter, with summer having many more hours of daylight than spring.
Reckoning by hours of daylight alone, summer solstice marks the midpoint, not the beginning, of the seasons. Midsummer takes place over the shortest night of the year, the summer solstice, or on a nearby date that varies with tradition. Where a seasonal lag of half a season or more is common, reckoning based on astronomical markers is shifted half a season. By this method, in North America, summer is the period from the summer solstice to the autumn equinox. Reckoning by cultural festivals, the summer season in the United States is traditionally regarded as beginning on Memorial Day weekend and ending on Labor Day, more in line with the meteorological definition for the parts of the country that have four-season weather; the similar Canadian tradition starts summer on Victoria Day one week prior and ends, as in the United States, on Labour Day. In Chinese astronomy, summer starts on or around 5 May, with the jiéqì known as lìxià, i.e. "establishment of summer", it ends on or around 6 August.
In southern and southeast Asia, where the monsoon occurs, summer is more defined as lasting from March, April and June, the warmest time of the year, ending with the onset of the monsoon rains. Because the temperature lag is shorter in the oceanic temperate southern hemisphere, most countries in this region use the meteorological definition with summer starting on 1 December and ending on the last day of February. Summer is traditionally associated with warm weather. In the Mediterranean regions, it is associated with dry weather, while in other places it is associated with rainy weather; the wet season is the main period of vegetation growth within the savanna climate regime. Where the wet season is associated with a seasonal shift in the prevailing winds, it is known as a monsoon. In the northern Atlantic Ocean, a distinct tropical cyclone season occurs from 1 June to 30 November; the statistical peak of the Atlantic hurricane season is 10 September. The Northeast Pacific Ocean has a broader period of activity, but in a similar time frame to the Atlantic.
The Northwest Pacific sees tropical cyclones year-round, with a minimum in February and March and a peak in early September. In the North Indian basin, storms are most common from April to December, with peaks in May and November. In the Southern Hemisphere, the tropical cyclone season runs from 1 November until the end of April with peaks in mid-February to early March. Thunderstorm season in the United States and Canada runs in the spring through summer; these storms can produce hail, strong winds and tornadoes during the afternoon and evening. Schools and universities have a summer break to take advantage of the warmer weather and longer days. In all countries, children are out of school during this time of year for summer break, although dates vary. In the United States, public schools end in late May in Memorial Day weekend, while colleges finish in early May, although some schools get out on the last or second last Thursday in May. In England and Wales, school resumes again in early September.
In Canada the summer holiday starts on the last or second-last Friday in June and ends in late August or on the first Monday of September, with the exception of when that date falls before Labour Day, in which case, ends on the second Monday of the month. In Russia the summer
Monsoon is traditionally defined as 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 the asymmetric heating of land and sea. The term monsoon is used to refer to the rainy phase of a seasonally changing pattern, although technically there is a dry phase; the term is sometimes incorrectly used for locally heavy but short-term rains, although these rains meet the dictionary definition of monsoon. The major monsoon systems of the world consist of the West Asia-Australian monsoons; the inclusion of the North and South American monsoons with incomplete wind reversal has been debated. 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; the English monsoon came from Portuguese monção from Arabic mawsim, "perhaps via early modern Dutch monson."
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. 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 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. Testing of this hypothesis awaits deep ocean sampling by the Integrated Ocean Drilling Program; the monsoon has varied in strength since this time linked to global climate change the cycle of the Pleistocene ice ages. A study of marine plankton suggested that the Indian Monsoon strengthened around 5 million years ago. 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. Five episodes during the Quaternary at 2.22 Ma, 1.83 Ma, 0.68 Ma, 0.45 Ma and 0.04 Ma were identified which showed a weakening of Leeuwin Current. The weakening of the LC would have an effect on the sea surface temperature field in the Indian Ocean, as the Indonesian through flow warms the Indian Ocean, thus these five intervals could 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, ice volume expansion and contraction can be obtained by studying the behaviour of the LC during Quaternary at close stratigraphic intervals.
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 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, available for growing crops. Monsoons are large-scale sea breezes which occur when the temperature on land is warmer or cooler than the temperature of the ocean; these temperature imbalances happen. Over oceans, the air temperature remains stable for two reasons: water has a high heat capacity, because both conduction and convection will equilibrate a hot or cold surface with deeper water. In contrast, dirt and rocks have lower heat capacities, they can only transmit heat into the earth by conduction and not by convection.
Therefore, bodies of water stay at a more 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, 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 it flows back toward the ocean. However, when the air rises, while it is still over the land, the air cools; this decreases the air's ability to hold water, this causes precipitation over the land. This is. In the colder months, the cycle is reversed; 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, this causes precipitation over the oceans.
(The cool air flows towards the land to complete the cy