1.
World Ocean
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The unity and continuity of the World Ocean, with relatively free interchange among its parts, is of fundamental importance to oceanography. In turn, oceanic waters are interspersed by many smaller seas, gulfs, a global ocean has existed in one form or another on Earth for eons, and the notion dates back to classical antiquity in the form of Oceanus. The contemporary concept of the World Ocean was coined in the early 20th century by the Russian oceanographer Yuly Shokalsky to refer to the ocean that covers. If viewed from the pole of Earth, the Atlantic, Indian. Farther north, the Atlantic opens into the Arctic Ocean, which is connected to the Pacific by the Bering Strait, the Pacific Ocean, the largest of the oceans, also reaches northward from the Southern Ocean to the Arctic Ocean. It spans the gap between Australia and Asia, and the Americas, the Pacific Ocean meets the Atlantic Ocean south of South America at Cape Horn. The Atlantic Ocean, the second largest, extends from the Southern Ocean between the Americas, and Africa and Europe, to the Arctic Ocean, the Atlantic Ocean meets the Indian Ocean south of Africa at Cape Agulhas. The Indian Ocean, the third largest, extends northward from the Southern Ocean to India, the Indian Ocean joins the Pacific Ocean to the east, near Australia. The Arctic Ocean is the smallest of the five and it joins the Atlantic Ocean near Greenland and Iceland and joins the Pacific Ocean at the Bering Strait. It overlies the North Pole, touching North America in the Western Hemisphere, the Arctic Ocean is partially covered in sea ice, the extent of which varies according to the season. The Southern Ocean is an ocean surrounding Antarctica, dominated by the Antarctic Circumpolar Current. The Southern Ocean is partially covered in sea ice, the extent of which according to the season. The Southern Ocean is the second smallest of the five named oceans, plate tectonics, post-glacial rebound and sea level rise continually change the coastline and structure of the world ocean. Superocean World Ocean Atlas Chekin, L.2002, the world ocean in medieval cartography. Vavilov Institute of the History of Science and Technology of the Russian Academy of Sciences, the Columbia Encyclopedia, 6th ed.2003. New York, Columbia University Press, also, Danabasoglu, Gokhan, McWilliams, the role of mesoscale tracer transports in the global ocean circulation. Boyer, Timothy P. and Stephens, Cathy, warming of the world ocean, abstract, article. Maps of the world ocean
2.
Temperature
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A temperature is an objective comparative measurement of hot or cold. It is measured by a thermometer, several scales and units exist for measuring temperature, the most common being Celsius, Fahrenheit, and, especially in science, Kelvin. Absolute zero is denoted as 0 K on the Kelvin scale, −273.15 °C on the Celsius scale, the kinetic theory offers a valuable but limited account of the behavior of the materials of macroscopic bodies, especially of fluids. Temperature is important in all fields of science including physics, geology, chemistry, atmospheric sciences, medicine. The Celsius scale is used for temperature measurements in most of the world. Because of the 100 degree interval, it is called a centigrade scale.15, the United States commonly uses the Fahrenheit scale, on which water freezes at 32°F and boils at 212°F at sea-level atmospheric pressure. Many scientific measurements use the Kelvin temperature scale, named in honor of the Scottish physicist who first defined it and it is a thermodynamic or absolute temperature scale. Its zero point, 0K, is defined to coincide with the coldest physically-possible temperature and its degrees are defined through thermodynamics. The temperature of zero occurs at 0K = −273. 15°C. For historical reasons, the triple point temperature of water is fixed at 273.16 units of the measurement increment, Temperature is one of the principal quantities in the study of thermodynamics. There is a variety of kinds of temperature scale and it may be convenient to classify them as empirically and theoretically based. Empirical temperature scales are historically older, while theoretically based scales arose in the middle of the nineteenth century, empirically based temperature scales rely directly on measurements of simple physical properties of materials. For example, the length of a column of mercury, confined in a capillary tube, is dependent largely on temperature. Such scales are only within convenient ranges of temperature. For example, above the point of mercury, a mercury-in-glass thermometer is impracticable. A material is of no use as a thermometer near one of its phase-change temperatures, in spite of these restrictions, most generally used practical thermometers are of the empirically based kind. Especially, it was used for calorimetry, which contributed greatly to the discovery of thermodynamics, nevertheless, empirical thermometry has serious drawbacks when judged as a basis for theoretical physics. Theoretically based temperature scales are based directly on theoretical arguments, especially those of thermodynamics, kinetic theory and they rely on theoretical properties of idealized devices and materials
3.
Ocean
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An ocean is a body of saline water that composes much of a planets hydrosphere. On Earth, an ocean is one of the major divisions of the World Ocean. These are, in descending order by area, the Pacific, Atlantic, Indian, Southern, the word sea is often used interchangeably with ocean in American English but, strictly speaking, a sea is a body of saline water partly or fully enclosed by land. The ocean contains 97% of Earths water, and oceanographers have stated that less than 5% of the World Ocean has been explored, the total volume is approximately 1.35 billion cubic kilometers with an average depth of nearly 3,700 meters. As the world ocean is the component of Earths hydrosphere, it is integral to all known life, forms part of the carbon cycle. The world ocean is the habitat of 230,000 known species, but because much of it is unexplored, the origin of Earths oceans remains unknown, oceans are thought to have formed in the Hadean period and may have been the impetus for the emergence of life. Extraterrestrial oceans may be composed of water or other elements and compounds, the only confirmed large stable bodies of extraterrestrial surface liquids are the lakes of Titan, although there is evidence for the existence of oceans elsewhere in the Solar System. Early in their histories, Mars and Venus are theorized to have had large water oceans. The Mars ocean hypothesis suggests that nearly a third of the surface of Mars was once covered by water, compounds such as salts and ammonia dissolved in water lower its freezing point so that water might exist in large quantities in extraterrestrial environments as brine or convecting ice. Unconfirmed oceans are speculated beneath the surface of many planets and natural satellites, notably. The Solar Systems giant planets are thought to have liquid atmospheric layers of yet to be confirmed compositions. Oceans may also exist on exoplanets and exomoons, including surface oceans of water within a circumstellar habitable zone. Ocean planets are a type of planet with a surface completely covered with liquid. The concept of Ōkeanós has an Indo-European connection, Greek Ōkeanós has been compared to the Vedic epithet ā-śáyāna-, predicated of the dragon Vṛtra-, who captured the cows/rivers. Related to this notion, the Okeanos is represented with a dragon-tail on some early Greek vases, though generally described as several separate oceans, these waters comprise one global, interconnected body of salt water sometimes referred to as the World Ocean or global ocean. This concept of a body of water with relatively free interchange among its parts is of fundamental importance to oceanography. The major oceanic divisions – listed below in descending order of area and volume – are defined in part by the continents, various archipelagos, Oceans are fringed by smaller, adjoining bodies of water such as seas, gulfs, bays, bights, and straits. The Mid-Oceanic Ridge of the World are connected and form the Ocean Ridge, the continuous mountain range is 65,000 km long, and the total length of the oceanic ridge system is 80,000 km long
4.
Sea
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A sea is a large body of salt water that is surrounded in whole or in part by land. More broadly, the sea is the system of Earths salty. The sea moderates Earths climate and has important roles in the cycle, carbon cycle. Although the sea has been traveled and explored since prehistory, the scientific study of the sea—oceanography—dates broadly to the British Challenger expedition of the 1870s. Owing to the present state of continental drift, the Northern Hemisphere is now equally divided between land and sea but the South is overwhelmingly oceanic. Salinity in the ocean is generally in a narrow band around 3. 5% by mass, although this can vary in more landlocked waters, near the mouths of large rivers. About 85% of the solids in the sea are sodium chloride. Deep-sea currents are produced by differences in salinity and temperature, surface currents are formed by the friction of waves produced by the wind and by tides, the changes in local sea level produced by the gravity of the Moon and Sun. The direction of all of these is governed by surface and submarine land masses, former changes in sea levels have left continental shelves, shallow areas in the sea close to land. The most diverse areas surround great tropical coral reefs, whaling in the deep sea was once common but whales dwindling numbers prompted international conservation efforts and finally a moratorium on most commercial hunting. Life may have started there and aquatic microbial mats are generally credited with the oxygenation of Earths atmosphere, the sea is an essential aspect of human trade, travel, mineral extraction, and power generation. It is the scene of activities including swimming, diving, surfing. However, population growth, industrialization, and intensive farming have all contributed to marine pollution. Atmospheric carbon dioxide is being absorbed in increasing amounts, lowering its pH in a known as ocean acidification. The shared nature of the sea has made overfishing an increasing problem, both senses of sea date to Old English, the larger sense has required a definite article since Early Middle English. Seas are generally larger than lakes and contain salt water, while the defining elements of size and being bounded are generally used, there is no formally accepted technical definition of sea among oceanographers. In international law, the United Nations Convention on the Law of the Sea states that all the ocean is the sea. Earth is the known planet with seas of liquid water on its surface, although Mars possesses ice caps
5.
Air mass
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In meteorology, an air mass is a volume of air defined by its temperature and water vapor content. Air masses cover many hundreds or thousands of miles. They are classified according to latitude and their continental or maritime source regions, colder air masses are termed polar or arctic, while warmer air masses are deemed tropical. Continental and superior air masses are dry while maritime and monsoon air masses are moist, weather fronts separate air masses with different density characteristics. Once an air mass moves away from its region, underlying vegetation. Classification schemes tackle an air mass characteristics, as well as modification, the Bergeron classification is the most widely accepted form of air mass classification, though others have produced more refined versions of this scheme over different regions of the globe. Air mass classification involves three letters, the first letter describes its moisture properties, with c used for [[continental air masses and m for maritime air masses. The second letter describes the characteristic of its source region, T for Tropical, P for Polar, A for arctic or Antarctic, M for monsoon, E for Equatorial. For instance, an air mass originating over the desert southwest of the United States in summer may be designated cT, an air mass originating over northern Siberia in winter may be indicated as cA. The stability of an air mass may be using a third letter, either k or w. An example of this might be an air mass blowing over the Gulf Stream. For example, a series of fronts over the Pacific might show an air mass denoted mPk followed by another denoted mPk, another convention utilizing these symbols is the indication of modification or transformation of one type to another. For instance, an Arctic air mass blowing out over the Gulf of Alaska may be shown as cA-mPk, yet another convention indicates the layering of air masses in certain situations. For instance, the overrunning of an air mass by an air mass from the Gulf of Mexico over the Central United States might be shown with the notation mT/cP. Arctic, Antarctic, and polar air masses are cold, the qualities of arctic air are developed over ice and snow-covered ground. Arctic air is cold, colder than polar air masses. Arctic air can be shallow in the summer, and rapidly modify as it moves equatorward, Polar air masses develop over higher latitudes over the land or ocean, are very stable, and generally shallower than arctic air. Polar air over the ocean loses its stability as it gains moisture over warmer ocean waters, Tropical and equatorial air masses are hot as they develop over lower latitudes
6.
Atmosphere of Earth
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The atmosphere of Earth is the layer of gases, commonly known as air, that surrounds the planet Earth and is retained by Earths gravity. The atmosphere of Earth protects life on Earth by absorbing solar radiation, warming the surface through heat retention. By volume, dry air contains 78. 09% nitrogen,20. 95% oxygen,0. 93% argon,0. 04% carbon dioxide, and small amounts of other gases. Air also contains an amount of water vapor, on average around 1% at sea level. The atmosphere has a mass of about 5. 15×1018 kg, the atmosphere becomes thinner and thinner with increasing altitude, with no definite boundary between the atmosphere and outer space. The Kármán line, at 100 km, or 1. 57% of Earths radius, is used as the border between the atmosphere and outer space. Atmospheric effects become noticeable during atmospheric reentry of spacecraft at an altitude of around 120 km, several layers can be distinguished in the atmosphere, based on characteristics such as temperature and composition. The study of Earths atmosphere and its processes is called atmospheric science, early pioneers in the field include Léon Teisserenc de Bort and Richard Assmann. The three major constituents of air, and therefore of Earths atmosphere, are nitrogen, oxygen, water vapor accounts for roughly 0. 25% of the atmosphere by mass. The remaining gases are often referred to as gases, among which are the greenhouse gases, principally carbon dioxide, methane, nitrous oxide. Filtered air includes trace amounts of other chemical compounds. Various industrial pollutants also may be present as gases or aerosols, such as chlorine, fluorine compounds, sulfur compounds such as hydrogen sulfide and sulfur dioxide may be derived from natural sources or from industrial air pollution. In general, air pressure and density decrease with altitude in the atmosphere, however, temperature has a more complicated profile with altitude, and may remain relatively constant or even increase with altitude in some regions. In this way, Earths atmosphere can be divided into five main layers, excluding the exosphere, Earth has four primary layers, which are the troposphere, stratosphere, mesosphere, and thermosphere. It extends from the exobase, which is located at the top of the thermosphere at an altitude of about 700 km above sea level, to about 10,000 km where it merges into the solar wind. This layer is composed of extremely low densities of hydrogen, helium and several heavier molecules including nitrogen, oxygen. The atoms and molecules are so far apart that they can travel hundreds of kilometers without colliding with one another, thus, the exosphere no longer behaves like a gas, and the particles constantly escape into space. These free-moving particles follow ballistic trajectories and may migrate in and out of the magnetosphere or the solar wind, the exosphere is located too far above Earth for any meteorological phenomena to be possible
7.
Snow
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Snowstorms organize and develop by feeding on sources of atmospheric moisture and cold air. Snowflakes nucleate around particles in the atmosphere by attracting supercooled water droplets, snowflakes take on a variety of shapes, basic among these are platelets, needles, columns and rime. As snow accumulates into a snowpack, it may blow into drifts, over time, accumulated snow metamorphoses, by sintering, sublimation and freeze-thaw. Where the climate is cold enough for year-to-year accumulation, a glacier may form, otherwise, snow typically melts seasonally, causing runoff into streams and rivers and recharging groundwater. Major snow-prone areas include the regions, the upper half of the Northern Hemisphere and mountainous regions worldwide with sufficient moisture. In the Southern Hemisphere, snow is confined primarily to mountainous areas, Snow affects ecosystems, as well, by providing an insulating layer during winter under which plants and animals are able to survive the cold. Snow develops in clouds that themselves are part of a weather system. The physics of snow crystal development in clouds results from a set of variables that include moisture content. The resulting shapes of the falling and fallen crystals can be classified into a number of shapes and combinations. Occasionally, some plate-like, dendritic and stellar-shaped snowflakes can form under clear sky with a cold temperature inversion present. Two additional and locally productive sources of snow are lake-effect storms and elevation effects, miid-latitude cyclones are low pressure areas which are capable of producing anything from cloudiness and mild snow storms to heavy blizzards. During a hemispheres fall, winter, and spring, the atmosphere over continents can be cold enough through the depth of the troposphere to cause snowfall, in the Northern Hemisphere, the northern side of the low pressure area produces the most snow. For the southern mid-latitudes, the side of a cyclone that produces the most snow is the southern side, a cold front, the leading edge of a cooler mass of air, can produce frontal snowsqualls—an intense frontal convective line, when temperature is near freezing at the surface. The strong convection that develops has enough moisture to produce whiteout conditions at places which line passes over as the wind causes intense blowing snow. This type of snowsquall generally lasts less than 30 minutes at any point along its path, in cases where there is a large amount of vertical growth and mixing the squall may develop embedded cumulonimbus clouds resulting in lightning and thunder which is dubbed thundersnow. A warm front can produce snow for a period, as warm, moist air overrides below-freezing air, often, snow transitions to rain in the warm sector behind the front. The same effect occurs over bodies of salt water, when it is termed ocean-effect or bay-effect snow. The effect is enhanced when the air mass is uplifted by the orographic influence of higher elevations on the downwind shores
8.
Rainband
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A rainband is a cloud and precipitation structure associated with an area of rainfall which is significantly elongated. Rainbands can be stratiform or convective, and are generated by differences in temperature, when noted on weather radar imagery, this precipitation elongation is referred to as banded structure. Rainbands within tropical cyclones are curved in orientation, tropical cyclone rainbands contain showers and thunderstorms that, together with the eyewall and the eye, constitute a hurricane or tropical storm. The extent of rainbands around a tropical cyclone can help determine the cyclones intensity, rainbands spawned near and ahead of cold fronts can be squall lines which are able to produce tornadoes. Rainbands associated with cold fronts can be warped by mountain barriers perpendicular to the fronts orientation due to the formation of a low-level barrier jet, bands of thunderstorms can form with sea breeze and land breeze boundaries, if enough moisture is present. If sea breeze rainbands become active enough just ahead of a cold front, banding within the comma head precipitation pattern of an extratropical cyclone can yield significant amounts of rain or snow. Behind extratropical cyclones, rainbands can form downwind of relative warm bodies of such as the Great Lakes. If the atmosphere is cold enough, these rainbands can yield heavy snow, rainbands in advance of warm occluded fronts and warm fronts are associated with weak upward motion, and tend to be wide and stratiform in nature. Wider rain bands can occur behind cold fronts, which tend to have more stratiform and these bands in the comma head are associated with areas of frontogensis, or zones of strengthening temperature contrast. Southwest of extratropical cyclones, curved flow bringing cold air across the relatively warm Great Lakes can lead to narrow lake effect snow bands which bring significant localized snowfall, rainbands exist in the periphery of tropical cyclones, which point towards the cyclones center of low pressure. Rainbands within tropical cyclones require ample moisture and a low level pool of cooler air, bands located 80 kilometres to 150 kilometres from a cyclones center migrate outward. They are capable of producing heavy rains and squalls of wind, as well as tornadoes, some rainbands move closer to the center, forming a secondary, or outer, eyewall within intense hurricanes. Within this method, the extent of banding and difference in temperature between the eye and eyewall is used to assign a maximum sustained wind and a central pressure. Central pressure values for their centers of low pressure derived from this technique are approximate, different programs have been studying these rainbands, including RAINEX. Convective rainbands can form parallel to terrain on its windward side and their spacing is normally 5 kilometres to 10 kilometres apart. If enough moisture is present, sea breeze and land breeze fronts can form convective rainbands, sea breeze front thunderstorm lines can become strong enough to mask the location of an approaching cold front by evening. The edge of ocean currents can lead to the development of bands due to heat differential at this interface. Downwind of islands, bands of showers and thunderstorms can develop due to low level wind convergence downwind of the island edges, offshore California, this has been noted in the wake of cold fronts
9.
Tropical cyclogenesis
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Tropical cyclogenesis is the development and strengthening of a tropical cyclone in the atmosphere. The mechanisms through which tropical cyclogenesis occurs are distinctly different from those through which mid-latitude cyclogenesis occurs, tropical cyclogenesis involves the development of a warm-core cyclone, due to significant convection in a favorable atmospheric environment. Tropical cyclones tend to develop during the summer, but have been noted in every month in most basins. Climate cycles such as ENSO and the Madden–Julian oscillation modulate the timing, there is a limit on tropical cyclone intensity which is strongly related to the water temperatures along its path. An average of 86 tropical cyclones of tropical storm intensity form annually worldwide, of those,47 reach hurricane/typhoon strength, and 20 become intense tropical cyclones. While these conditions are necessary for tropical cyclone formation, they do not guarantee that a tropical cyclone will form. Normally, a temperature of 26.5 °C spanning through at least a 50-metre depth is considered the minimum to maintain the special mesocyclone that is the tropical cyclone. These warm waters are needed to maintain the core that fuels tropical systems. This value is well above 16.1 °C, the average surface temperature of the oceans. Tropical cyclones are known to even when normal conditions are not met. In a moist atmosphere, this rate is 6.5 °C/km, while in an atmosphere with less than 100% relative humidity. Under a cold cyclone,500 hPa temperatures can fall as low as −30 °C and this also explains why moisture in the mid-levels of the troposphere, roughly at the 500 hPa level, is normally a requirement for development. However, when dry air is found at the same height, at heights near the tropopause, the 30-year average temperature was −77 °C. A recent example of a cyclone that maintained itself over cooler waters was Epsilon of the 2005 Atlantic hurricane season. Emanuels model is called the maximum intensity, or MPI. Maps created from this equation show regions where tropical storm and hurricane formation is possible and this does not take into account vertical wind shear. A minimum distance of 500 km from the equator is normally needed for tropical cyclogenesis, the Coriolis force imparts rotation on the flow and arises as winds begin to flow in toward the lower pressure created by the pre-existing disturbance. The existence of a significant Coriolis force allows the developing vortex to achieve gradient wind balance, even with perfect upper level conditions and the required atmospheric instability, the lack of a surface focus will prevent the development of organized convection and a surface low
10.
Earth
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Earth, otherwise known as the World, or the Globe, is the third planet from the Sun and the only object in the Universe known to harbor life. It is the densest planet in the Solar System and the largest of the four terrestrial planets, according to radiometric dating and other sources of evidence, Earth formed about 4.54 billion years ago. Earths gravity interacts with objects in space, especially the Sun. During one orbit around the Sun, Earth rotates about its axis over 365 times, thus, Earths axis of rotation is tilted, producing seasonal variations on the planets surface. The gravitational interaction between the Earth and Moon causes ocean tides, stabilizes the Earths orientation on its axis, Earths lithosphere is divided into several rigid tectonic plates that migrate across the surface over periods of many millions of years. About 71% of Earths surface is covered with water, mostly by its oceans, the remaining 29% is land consisting of continents and islands that together have many lakes, rivers and other sources of water that contribute to the hydrosphere. The majority of Earths polar regions are covered in ice, including the Antarctic ice sheet, Earths interior remains active with a solid iron inner core, a liquid outer core that generates the Earths magnetic field, and a convecting mantle that drives plate tectonics. Within the first billion years of Earths history, life appeared in the oceans and began to affect the Earths atmosphere and surface, some geological evidence indicates that life may have arisen as much as 4.1 billion years ago. Since then, the combination of Earths distance from the Sun, physical properties, in the history of the Earth, biodiversity has gone through long periods of expansion, occasionally punctuated by mass extinction events. Over 99% of all species that lived on Earth are extinct. Estimates of the number of species on Earth today vary widely, over 7.4 billion humans live on Earth and depend on its biosphere and minerals for their survival. Humans have developed diverse societies and cultures, politically, the world has about 200 sovereign states, the modern English word Earth developed from a wide variety of Middle English forms, which derived from an Old English noun most often spelled eorðe. It has cognates in every Germanic language, and their proto-Germanic root has been reconstructed as *erþō, originally, earth was written in lowercase, and from early Middle English, its definite sense as the globe was expressed as the earth. By early Modern English, many nouns were capitalized, and the became the Earth. More recently, the name is simply given as Earth. House styles now vary, Oxford spelling recognizes the lowercase form as the most common, another convention capitalizes Earth when appearing as a name but writes it in lowercase when preceded by the. It almost always appears in lowercase in colloquial expressions such as what on earth are you doing, the oldest material found in the Solar System is dated to 4. 5672±0.0006 billion years ago. By 4. 54±0.04 Gya the primordial Earth had formed, the formation and evolution of Solar System bodies occurred along with the Sun
11.
Ocean current
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Depth contours, shoreline configurations, and interactions with other currents influence a currents direction and strength. Therefore ocean currents are primarily horizontal water movements, Ocean currents flow for great distances, and together, create the global conveyor belt which plays a dominant role in determining the climate of many of the Earth’s regions. More specifically, ocean currents influence the temperature of the regions through which they travel, for example, warm currents traveling along more temperate coasts increase the temperature of the area by warming the sea breezes that blow over them. Perhaps the most striking example is the Gulf Stream, which makes northwest Europe much more temperate than any region at the same latitude. Another example is Lima, Peru where the climate is cooler than the tropical latitudes in which the area is located, in these wind driven currents, the Ekman spiral effect results in the currents flowing at an angle to the driving winds. In addition, the areas of ocean currents move somewhat with the seasons. Deep ocean basins generally have a surface current, in that the eastern equatorward-flowing branch is broad. These western boundary currents are a consequence of the rotation of the Earth, Deep ocean currents are driven by density and temperature gradients. Thermohaline circulation is known as the oceans conveyor belt. These currents, called submarine rivers, flow under the surface of the ocean and are hidden from immediate detection, where significant vertical movement of ocean currents is observed, this is known as upwelling and downwelling. Deep ocean currents are currently being researched using a fleet of robots called Argo. The South Equatorial Currents of the Atlantic and Pacific straddle the equator, though the Coriolis effect is weak near the equator, water moving in the currents on either side of the equator is deflected slightly poleward and replaced by deeper water. Thus, equatorial upwelling occurs in these westward flowing equatorial surface currents, upwelling is an important process because this water from within and below the pycnocline is often rich in nutrients and greatly benefits the growth of marine organisms. By contrast, generally poor conditions for growth prevail in most of the tropical ocean because strong layering isolates deep. Ocean currents are measured in sverdrup, where 1 sv is equivalent to a flow rate of 1,000,000 m3 per second. Surface currents are found on the surface of an ocean, and are driven by large scale wind currents and they are directly affected by the wind—the Coriolis effect plays a role in their behaviors. Horizontal and vertical currents also exist below the pycnocline in the deeper waters. The movement of water due to differences in density as a function of water temperature, ripple marks in sediments, scour lines, and the erosion of rocky outcrops on deep-ocean floors are evidence that relatively strong, localized bottom currents exist
12.
Atlantic multidecadal oscillation
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The Atlantic Multidecadal Oscillation is a climate cycle that affects the sea surface temperature of the North Atlantic Ocean based on different modes on multidecadal timescales. The Atlantic Multidecadal Oscillation was identified by Schlesinger and Ramankutty in 1994, the AMO signal is usually defined from the patterns of SST variability in the North Atlantic once any linear trend has been removed. This detrending is intended to remove the influence of greenhouse gas-induced global warming from the analysis, however, if the global warming signal is significantly non-linear in time, variations in the forced signal will leak into the AMO definition. Consequently, correlations with the AMO index may mask effects of global warming, several methods have been proposed to remove the global trend and ENSO influence over the North Atlantic SST. Ting et al. however argue that the forced SST pattern is not spatially uniform, they separated the forced, van Oldenborgh et al. derived an AMO index as the SST averaged over the extra-tropical North Atlantic minus the regression on global mean temperature. Guan and Nigam removed the non stationary global trend and Pacific natural variability before applying an EOF analysis to the residual North Atlantic SST, in models, AMO-like variability is associated with small changes in the North Atlantic branch of the Thermohaline Circulation. However, historical oceanic observations are not sufficient to associate the derived AMO index to present-day circulation anomalies, the Atlantic Multidecadal Oscillation is important for how external forcings are linked with North Atlantic SSTs. The AMO index is correlated to air temperatures and rainfall over much of the Northern Hemisphere, in particular in the climate in North America. Through changes in circulation, the AMO can also modulate spring snowfall over the Alps. Rainfall patterns are affected in North Eastern Brazilian and African Sahel and it is also associated with changes in the frequency of North American droughts and is reflected in the frequency of severe Atlantic hurricane activity. Recent research suggests that the AMO is related to the past occurrence of droughts in the US Midwest. When the AMO is in its phase, these droughts tend to be more frequent or prolonged. Two of the most severe droughts of the 20th century occurred during the positive AMO between 1925 and 1965, The Dust Bowl of the 1930s and the 1950s drought, Florida and the Pacific Northwest tend to be the opposite—warm AMO, more rainfall. Climate models suggest that a phase of the AMO strengthens the summer rainfall over India and Sahel. Paleoclimatologic studies have confirmed this pattern—increased rainfall in AMO warmphase, decreased in cold phase—for the Sahel over the past 3,000 years, in viewing actual data on a short time horizon, sparse experience would suggest the frequency of major hurricanes is not strongly correlated with the AMO. During warm phases of the AMO, the number of minor hurricanes saw a modest increase, the hurricane activity index is found to be highly correlated with the Atlantic multidecadal oscillation. If there is an increase in hurricane activity connected to global warming, the AMO alternately obscures and exaggerates the global increase in temperatures due to human-induced global warming. Based on the duration of negative and positive phases of the AMO
13.
Thermohaline circulation
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Thermohaline circulation is a part of the large-scale ocean circulation that is driven by global density gradients created by surface heat and freshwater fluxes. The adjective thermohaline derives from thermo- referring to temperature and -haline referring to salt content, wind-driven surface currents travel polewards from the equatorial Atlantic Ocean, cooling en route, and eventually sinking at high latitudes. This dense water then flows into the ocean basins, while the bulk of it upwells in the Southern Ocean, the oldest waters upwell in the North Pacific. Extensive mixing therefore takes place between the basins, reducing differences between them and making the Earths oceans a global system. On their journey, the water masses transport both energy and matter around the globe, as such, the state of the circulation has a large impact on the climate of the Earth. The thermohaline circulation is called the ocean conveyor belt, the great ocean conveyor, or the global conveyor belt. On occasion, it is used to refer to the overturning circulation. Moreover, temperature and salinity gradients can lead to circulation effects that are not included in the MOC itself. The movement of surface currents pushed by the wind is fairly intuitive, for example, the wind easily produces ripples on the surface of a pond. Thus the deep ocean—devoid of wind—was assumed to be perfectly static by early oceanographers, however, modern instrumentation shows that current velocities in deep water masses can be significant. In general ocean water velocities range from fractions of centimeters per second to more than 1 m/s in surface currents like the Gulf Stream. In the deep ocean, the predominant driving force is differences in density, caused by salinity, there is often confusion over the components of the circulation that are wind and density driven. Note that ocean currents due to tides are also significant in places, most prominent in relatively shallow coastal areas. There they are thought to facilitate mixing processes, especially diapycnal mixing. The density of water is not globally homogeneous, but varies significantly and discretely. Sharply defined boundaries exist between water masses which form at the surface, and subsequently maintain their own identity within the ocean, but these sharp boundaries are not to be imagined spatially but rather in a T-S-diagram where water masses are distinguished. They position themselves above or below each other according to their density, warm seawater expands and is thus less dense than cooler seawater. Saltier water is denser than water because the dissolved salts fill interstices between water molecules, resulting in more mass per unit volume
14.
Upwelling
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The nutrient-rich upwelled water stimulates the growth and reproduction of primary producers such as phytoplankton. Due to the biomass of phytoplankton and presence of water in these regions, upwelling zones can be identified by cool sea surface temperatures. The increased availability in upwelling regions results in levels of primary productivity. Approximately 25% of the global marine fish catches come from five upwellings that occupy only 5% of the total ocean area. Upwellings that are driven by coastal currents or diverging open ocean have the greatest impact on nutrient-enriched waters, the three main drivers that work together to cause upwelling are wind, Coriolis effects, and Ekman transport. They operate differently for different types of upwelling, but the effects are the same. In the overall process of upwelling, winds blow across the sea surface at a particular direction, as a result of the wind, the water is transported a net of 90 degrees from the direction of the wind due to Coriolis forces and Ekman transport. This results in a spiral of water movement down the water column, then, it is the Coriolis forces that dictate which way the water will move, in the Northern hemisphere, the water is transported to the right of the direction of the wind. In the Southern Hemisphere, the water is transported to the left of the wind, if this net movement of water is divergent, then upwelling of deep water occurs to replace the water that was lost. The major upwellings in the ocean are associated with the divergence of currents that bring deeper, colder, coastal upwelling is the best known type of upwelling, and the most closely related to human activities as it supports some of the most productive fisheries in the world. Wind-driven currents are diverted to the right of the winds in the Northern Hemisphere, the result is a net movement of surface water at right angles to the direction of the wind, known as the Ekman transport. When Ekman transport is occurring away from the coast, surface waters moving away are replaced by deeper, colder, and denser water. Normally, this process occurs at a rate of about 5–10 meters per day. Deep waters are rich in nutrients, including nitrate, phosphate and silicic acid, Upwelling regions therefore result in very high levels of primary production in comparison to other areas of the ocean. They account for about 50% of global marine productivity, high primary production propagates up the food chain because phytoplankton are at the base of the oceanic food chain. All of these currents support major fisheries, the four major eastern boundary currents in which coastal upwelling primarily occurs are the Canary Current, Benguela Current, California Current, and Humboldt Current. The Benguela Current is the boundary of the South Atlantic subtropical gyre. The subsystems are divided by an area of permanent upwelling off of Luderitz, the California Current System is an eastern boundary current of the North Pacific that is also characterized by a north and south split
15.
Continental shelf
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The continental shelf is an underwater landmass which extends from a continent, resulting in an area of relatively shallow water known as a shelf sea. Much of the shelves were exposed during glacial periods and interglacial periods, the shelf surrounding an island is known as an insular shelf. The continental margin, between the shelf and the abyssal plain, comprises a steep continental slope followed by the flatter continental rise. Sediment from the continent above cascades down the slope and accumulates as a pile of sediment at the base of the slope, extending as far as 500 km from the slope, it consists of thick sediments deposited by turbidity currents from the shelf and slope. The continental rises gradient is intermediate between the slope and the shelf, on the order of 0. 5–1°, the largest shelf – the Siberian Shelf in the Arctic Ocean – stretches to 1,500 kilometers in width. The South China Sea lies over another extensive area of shelf, the Sunda Shelf, which joins Borneo, Sumatra. Other familiar bodies of water that overlie continental shelves are the North Sea, the average width of continental shelves is about 80 km. The depth of the shelf also varies, but is limited to water shallower than 150 m. The slope of the shelf is quite low, on the order of 0. 5°, vertical relief is also minimal. Though the continental shelf is treated as a province of the ocean, it is not part of the deep ocean basin proper. Passive continental margins such as most of the Atlantic coasts have wide and shallow shelves, active continental margins have narrow, relatively steep shelves, due to frequent earthquakes that move sediment to the deep sea. The shelf usually ends at a point of increasing slope, the sea floor below the break is the continental slope. Below the slope is the rise, which finally merges into the deep ocean floor. The continental shelf and the slope are part of the continental margin, the shelf area is commonly subdivided into the inner continental shelf, mid continental shelf, and outer continental shelf, each with their specific geomorphology and marine biology. The character of the shelf changes dramatically at the shelf break, with a few exceptions, the shelf break is located at a remarkably uniform depth of roughly 140 m, this is likely a hallmark of past ice ages, when sea level was lower than it is now. The continental slope is steeper than the shelf, the average angle is 3°. The slope is cut with submarine canyons. The physical mechanisms involved in forming these canyons were not well understood until the 1960s, the continental shelves are covered by terrigenous sediments, that is, those derived from erosion of the continents
16.
South America
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South America is a continent located in the western hemisphere, mostly in the southern hemisphere, with a relatively small portion in the northern hemisphere. It may also be considered a subcontinent of the Americas, which is the used in nations that speak Romance languages. The reference to South America instead of other regions has increased in the last decades due to changing geopolitical dynamics. It is bordered on the west by the Pacific Ocean and on the north and east by the Atlantic Ocean, North America and it includes twelve sovereign states, a part of France, and a non-sovereign area. In addition to this, the ABC islands of the Kingdom of the Netherlands, Trinidad and Tobago, South America has an area of 17,840,000 square kilometers. Its population as of 2005 has been estimated at more than 371,090,000, South America ranks fourth in area and fifth in population. Brazil is by far the most populous South American country, with more than half of the population, followed by Colombia, Argentina, Venezuela. In recent decades Brazil has also concentrated half of the regions GDP and has become a first regional power, most of the population lives near the continents western or eastern coasts while the interior and the far south are sparsely populated. Most of the continent lies in the tropics, the continents cultural and ethnic outlook has its origin with the interaction of indigenous peoples with European conquerors and immigrants and, more locally, with African slaves. Given a long history of colonialism, the majority of South Americans speak Portuguese or Spanish. South America occupies the portion of the Americas. The continent is delimited on the northwest by the Darién watershed along the Colombia–Panama border. Almost all of mainland South America sits on the South American Plate, South Americas major mineral resources are gold, silver, copper, iron ore, tin, and petroleum. These resources found in South America have brought high income to its countries especially in times of war or of rapid growth by industrialized countries elsewhere. However, the concentration in producing one major export commodity often has hindered the development of diversified economies and this is leading to efforts to diversify production to drive away from staying as economies dedicated to one major export. South America is one of the most biodiverse continents on earth, South America is home to many interesting and unique species of animals including the llama, anaconda, piranha, jaguar, vicuña, and tapir. The Amazon rainforests possess high biodiversity, containing a proportion of the Earths species. Brazil is the largest country in South America, encompassing around half of the land area
17.
Numerical weather prediction
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Numerical weather prediction uses mathematical models of the atmosphere and oceans to predict the weather based on current weather conditions. Though first attempted in the 1920s, it was not until the advent of computer simulation in the 1950s that numerical weather predictions produced realistic results. Manipulating the vast datasets and performing the calculations necessary to modern numerical weather prediction requires some of the most powerful supercomputers in the world. Even with the power of supercomputers, the forecast skill of numerical weather models extends to only about six days. Factors affecting the accuracy of numerical predictions include the density and quality of observations used as input to the forecasts, post-processing techniques such as model output statistics have been developed to improve the handling of errors in numerical predictions. A more fundamental problem lies in the nature of the partial differential equations that govern the atmosphere. It is impossible to solve these equations exactly, and small errors grow with time, present understanding is that this chaotic behavior limits accurate forecasts to about 14 days even with perfectly accurate input data and a flawless model. This approach analyzes multiple forecasts created with an individual forecast model or multiple models and it was not until the advent of the computer and computer simulations that computation time was reduced to less than the forecast period itself. The ENIAC was used to create the first weather forecasts via computer in 1950, in 1954, Carl-Gustav Rossbys group at the Swedish Meteorological and Hydrological Institute used the same model to produce the first operational forecast. Operational numerical weather prediction in the United States began in 1955 under the Joint Numerical Weather Prediction Unit, in 1956, Norman Phillips developed a mathematical model which could realistically depict monthly and seasonal patterns in the troposphere, this became the first successful climate model. Following Phillips work, several groups working to create general circulation models. The first general circulation model that combined both oceanic and atmospheric processes was developed in the late 1960s at the NOAA Geophysical Fluid Dynamics Laboratory. As computers have more powerful, the size of the initial data sets has increased. These newer models include more physical processes in the simplifications of the equations of motion in numerical simulations of the atmosphere, in 1966, West Germany and the United States began producing operational forecasts based on primitive-equation models, followed by the United Kingdom in 1972 and Australia in 1977. The development of limited area models facilitated advances in forecasting the tracks of tropical cyclones as well as air quality in the 1970s and 1980s, by the early 1980s models began to include the interactions of soil and vegetation with the atmosphere, which led to more realistic forecasts. The output of forecast models based on atmospheric dynamics is unable to resolve some details of the weather near the Earths surface. As such, a relationship between the output of a numerical weather model and the ensuing conditions at the ground was developed in the 1970s and 1980s. The process of entering data into the model to generate initial conditions is called initialization
18.
Sea breeze
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As such sea breezes are more localised than prevailing winds. Because land absorbs solar radiation far more quickly than water, a sea breeze is an occurrence along coasts after sunrise. Sea breezes and land breezes are important factors in coastal regions prevailing winds. The term offshore wind may refer to any wind over open water, wind farms are often situated near a coast to take advantage of the normal daily fluctuations of wind speed resulting from sea or land breezes. The sea has a heat capacity than land, so the surface of the sea warms up more slowly than the lands surface. As the temperature of the surface of the land rises, the heats the air above it by conduction. The warm air is less dense and so it expands, decreasing the pressure over the land near the coast, the air above the sea has a relatively higher pressure, causing air near the coast to flow towards the lower pressure over land. The strength of the sea breeze is directly proportional to the difference between the land and the sea. If a strong wind is present, that is, a wind greater than 8 knots and opposing the direction of a possible sea breeze. A sea-breeze front is a front created by a sea breeze. The cold air from the sea meets the air from the land. When powerful this front creates cumulus clouds, and if the air is humid and unstable, the front can sometimes trigger thunderstorms. If the flow aloft is aligned with the direction of the sea breeze, places experiencing the sea breeze frontal passage will have benign, or fair, weather for the remainder of the day. At the front warm air continues to flow upward and cold air moves in to replace it. Its speed depends on whether it is assisted or hampered by the wind. At night, the sea breeze usually changes to a land breeze, thunderstorms caused by powerful sea breeze fronts frequently occur in Florida, a peninsula surrounded on both the east and west by the Atlantic Ocean and Gulf of Mexico, respectively. These storms also can produce significant hail due to the tremendous updraft it causes in the atmosphere especially during times when the atmosphere is cooler such as during the spring or fall. On calm summer afternoons with little prevailing wind, sea breezes from both coasts may collide in the middle, creating severe storms down the center of the state
19.
Fog
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Fog consists of visible cloud water droplets or ice crystals suspended in the air at or near the Earths surface. Fog can be considered a type of low-lying cloud and is influenced by nearby bodies of water, topography. In turn, fog has affected many human activities, such as shipping, travel, the term fog is typically distinguished from the more generic term cloud in that fog is low-lying, and the moisture in the fog is often generated locally. By definition, fog reduces visibility to less than 1 kilometre, for aviation purposes in the UK, a visibility of less than 5 kilometres but greater than 999 metres is considered to be mist if the relative humidity is 70% or greater, below 70%, haze is reported. Fog forms when the difference between air temperature and dew point is less than 2.5 °C or 4 °F, Fog begins to form when water vapor condenses into tiny liquid water droplets suspended in the air. Water vapor normally begins to condense on condensation nuclei such as dust, ice, Fog, like its elevated cousin stratus, is a stable cloud deck which tends to form when a cool, stable air mass is trapped underneath a warm air mass. Fog normally occurs at a relative humidity near 100% and this occurs from either added moisture in the air, or falling ambient air temperature. However, fog can form at lower humidities, and can fail to form with relative humidity at 100%. At 100% relative humidity, the air cannot hold additional moisture, thus, Fog can form suddenly and can dissipate just as rapidly. The sudden formation of fog is known as flash fog, Fog commonly produces precipitation in the form of drizzle or very light snow. Drizzle occurs when the humidity of fog attains 100% and the cloud droplets begin to coalesce into larger droplets. This can occur when the fog layer is lifted and cooled sufficiently, drizzle becomes freezing drizzle when the temperature at the surface drops below the freezing point. The inversion boundary varies its altitude primarily in response to the weight of the air above it, the marine layer, and any fogbank it may contain, will be squashed when the pressure is high, and conversely, may expand upwards when the pressure above it is lowering. Fog can form in a number of ways, depending on how the cooling that caused the condensation occurred, radiation fog is formed by the cooling of land after sunset by thermal radiation in calm conditions with clear sky. The warm ground produces condensation in the air by heat conduction. In perfect calm the fog layer can be less than a meter deep, radiation fogs occur at night, and usually do not last long after sunrise, but they can persist all day in the winter months especially in areas bounded by high ground. Radiation fog is most common in autumn and early winter, examples of this phenomenon include the Tule fog. Ground fog is fog that obscures less than 60% of the sky, advection fog occurs when moist air passes over a cool surface by advection and is cooled
20.
Weather satellite
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The weather satellite is a type of satellite that is primarily used to monitor the weather and climate of the Earth. Satellites can be polar orbiting, covering the entire Earth asynchronously, or geostationary, Meteorological satellites see more than clouds and cloud systems. City lights, fires, effects of pollution, auroras, sand and dust storms, snow cover, ice mapping, boundaries of currents, energy flows. Other types of information are collected using weather satellites. Weather satellite images helped in monitoring the volcanic ash cloud from Mount St. Helens, smoke from fires in the western United States such as Colorado and Utah have also been monitored. Other environmental satellites can detect changes in the Earths vegetation, sea state, ocean color, El Niño and its effects on weather are monitored daily from satellite images. The Antarctic ozone hole is mapped from weather satellite data, collectively, weather satellites flown by the U. S. Europe, India, China, Russia, and Japan provide nearly continuous observations for a global weather watch. As early as 1946, the idea of cameras in orbit to observe the weather was being developed and this was due to sparse data observation coverage and the expense of using cloud cameras on rockets. By 1958, the prototypes for TIROS and Vanguard were created. The first weather satellite, Vanguard 2, was launched on February 17,1959 and it was designed to measure cloud cover and resistance, but a poor axis of rotation and its elliptical orbit kept it from collecting a notable amount of useful data. The Explorer VI and VII satellites also contained weather-related experiments, the first weather satellite to be considered a success was TIROS-1, launched by NASA on April 1,1960. TIROS operated for 78 days and proved to be more successful than Vanguard 2. TIROS paved the way for the Nimbus program, whose technology and findings are the heritage of most of the Earth-observing satellites NASA, the ESSA and NOAA polar orbiting satellites followed suit from the late 1960s onward. Geostationary satellites followed, beginning with the ATS and SMS series in the late 1960s and early 1970s, observation is typically made via different channels of the electromagnetic spectrum, in particular, the visible and infrared portions. Some of these channels include Visible and Near Infrared,0.6 μm –1.6 μm – For recording cloud cover during the day Infrared,3.9 μm –7.3 μm,8.7 μm, –13. Even wind can be determined by cloud patterns, alignments and movement from successive photos, Infrared pictures depict ocean eddies or vortices and map currents such as the Gulf Stream which are valuable to the shipping industry. Fishermen and farmers are interested in knowing land and water temperatures to protect their crops against frost or increase their catch from the sea, even El Niño phenomena can be spotted. Using color-digitized techniques, the gray shaded thermal images can be converted to color for easier identification of desired information, each meteorological satellite is designed to use one of two different classes of orbit, geostationary and polar orbiting
21.
Thermocline
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A thermocline is a thin but distinct layer in a large body of fluid in which temperature changes more rapidly with depth than it does in the layers above or below. In the ocean, the thermocline divides the upper mixed layer from the deep water below. Factors that affect the depth and thickness of a thermocline include seasonal weather variations, latitude and local conditions, such as tides. Most of the energy of sunlight is absorbed in the first few centimeters at the oceans surface. Below this mixed layer, the temperature remains relatively stable over day/night cycles, the temperature of the deep ocean drops gradually with depth. As saline water does not freeze until it reaches −2.3 °C the temperature well below the surface is not far from zero degrees. It is semi-permanent in the tropics, variable in temperate regions and shallow to nonexistent in the polar regions, a layer of sea ice will act as an insulation blanket. Technically, this stems from a discontinuity in the acoustic impedance of water created by the sudden change in density. It gives the water an appearance of wrinkled glass that is used to obscure bathroom windows and is caused by the altered refractive index of the cold or warm water column. These same schlieren can be observed when hot air rises off the tarmac at airports or desert roads and is the cause of mirages, thermoclines can also be observed in lakes. In colder climates, this leads to a phenomenon called stratification, during the summer, warm water, which is less dense, will sit on top of colder, denser, deeper water with a thermocline separating them. The warm layer is called the epilimnion and the layer is called the hypolimnion. Because the warm water is exposed to the sun during the day, as winter approaches, the temperature of the surface water will drop as nighttime cooling dominates heat transfer. This process is aided by wind or any process that agitates the water. This effect also occurs in Arctic and Antarctic waters, bringing water to the surface which and this enriching of surface nutrients may produce blooms of phytoplankton, making these areas productive. As the temperature continues to drop, the water on the surface may get cold enough to freeze, a new thermocline develops where the densest water sinks to the bottom, and the less dense water rises to the top. Once this new stratification establishes itself, it lasts until the water warms enough for the turnover, which occurs after the ice melts. During this transition, a bar may develop
22.
Benjamin Franklin
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Benjamin Franklin was one of the Founding Fathers of the United States. Franklin was a polymath and a leading author, printer, political theorist, politician, freemason, postmaster, scientist, inventor, civic activist, statesman. As a scientist, he was a figure in the American Enlightenment. As an inventor, he is known for the rod, bifocals. He facilitated many civic organizations, including Philadelphias fire department and the University of Pennsylvania, Franklin earned the title of The First American for his early and indefatigable campaigning for colonial unity, initially as an author and spokesman in London for several colonies. As the first United States Ambassador to France, he exemplified the emerging American nation, in the words of historian Henry Steele Commager, In a Franklin could be merged the virtues of Puritanism without its defects, the illumination of the Enlightenment without its heat. To Walter Isaacson, this makes Franklin the most accomplished American of his age, Franklin became a successful newspaper editor and printer in Philadelphia, the leading city in the colonies, publishing the Pennsylvania Gazette at the age of 23. He became wealthy publishing this and Poor Richards Almanack, which he authored under the pseudonym Richard Saunders, after 1767, he was associated with the Pennsylvania Chronicle, a newspaper that was known for its revolutionary sentiments and criticisms of the British policies. He pioneered and was first president of The Academy and College of Philadelphia which opened in 1751 and he organized and was the first secretary of the American Philosophical Society and was elected president in 1769. Franklin became a hero in America as an agent for several colonies when he spearheaded an effort in London to have the Parliament of Great Britain repeal the unpopular Stamp Act. An accomplished diplomat, he was widely admired among the French as American minister to Paris and was a figure in the development of positive Franco-American relations. His efforts proved vital for the American Revolution in securing shipments of crucial munitions from France, during the Revolution, he became the first US Postmaster General. He was active in community affairs and colonial and state politics, from 1785 to 1788, he served as governor of Pennsylvania. He initially owned and dealt in slaves but, by the 1750s, he argued against slavery from an economic perspective, Franklins father, Josiah Franklin, was a tallow chandler, a soap-maker and a candle-maker. Josiah was born at Ecton, Northamptonshire, England on December 23,1657, the son of Thomas Franklin, a blacksmith-farmer, and Jane White. His mother, Abiah Folger, was born in Nantucket, Massachusetts, on August 15,1667, to Peter Folger, a miller and schoolteacher, and his wife, Mary Morrill, Josiah Franklin had seventeen children with his two wives. He married his first wife, Anne Child, in about 1677 in Ecton and emigrated with her to Boston in 1683, after her death, Josiah was married to Abiah Folger on July 9,1689 in the Old South Meeting House by Samuel Willard. Benjamin, their child, was Josiah Franklins fifteenth child and tenth
23.
Mercury-in-glass thermometer
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The mercury-in-glass or mercury thermometer was invented by Polish-Dutch physicist Daniel Gabriel Fahrenheit in Amsterdam. It consists of a bulb containing mercury attached to a tube of narrow diameter. The volume of mercury changes slightly with temperature, the change in volume drives the narrow mercury column a relatively long way up the tube. The space above the mercury may be filled with nitrogen or it may be at less than atmospheric pressure, the thermometer was used by the originators of the Fahrenheit and Celsius scales. Anders Celsius, a Swedish scientist, devised the Celsius scale, Celsius used two fixed points in his scale, the temperature of melting ice and the temperature of boiling water. This wasnt a new idea, since Isaac Newton was already working on something similar, the distinction of Celsius was to use the condition of melting and not that of freezing. The experiments for reaching a good calibration of his thermometer lasted for 2 winters, by performing the same experiment over and over again, he discovered that ice always melted at the same calibration mark on the thermometer. He found a fixed point in the calibration of boiling water to water vapour. At the moment that he removed the thermometer from the vapour and this was related to the rapid cooling of the glass. When Celsius decided to use his own scale, he originally defined his scale upside-down, i. e. he chose to set the boiling point of pure water at 0 °C. One year later, Frenchman Jean-Pierre Christin proposed to invert the scale with the point at 0 °C. This point is the point of water. In the same manner mark the point where the fluid stabilises when the thermometer is placed in boiling water vapour, divide the length between the two marks into 100 equal parts. These points are adequate for approximate calibration but both vary with atmospheric pressure, nowadays, the triple point of water is used instead of the freezing point. Before the discovery of the thermodynamic temperature, the thermometer defined the temperature. In practice, several materials gave very similar temperatures to each other and, a special kind of mercury-in-glass thermometer, called a maximum thermometer, works by having a constriction in the neck close to the bulb. As the temperature rises, the mercury is pushed up through the constriction by the force of expansion, when the temperature falls, the column of mercury breaks at the constriction and cannot return to the bulb, thus remaining stationary in the tube. The observer can then read the temperature over the set period of time
24.
United States
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Forty-eight of the fifty states and the federal district are contiguous and located in North America between Canada and Mexico. The state of Alaska is in the northwest corner of North America, bordered by Canada to the east, the state of Hawaii is an archipelago in the mid-Pacific Ocean. The U. S. territories are scattered about the Pacific Ocean, the geography, climate and wildlife of the country are extremely diverse. At 3.8 million square miles and with over 324 million people, the United States is the worlds third- or fourth-largest country by area, third-largest by land area. It is one of the worlds most ethnically diverse and multicultural nations, paleo-Indians migrated from Asia to the North American mainland at least 15,000 years ago. European colonization began in the 16th century, the United States emerged from 13 British colonies along the East Coast. Numerous disputes between Great Britain and the following the Seven Years War led to the American Revolution. On July 4,1776, during the course of the American Revolutionary War, the war ended in 1783 with recognition of the independence of the United States by Great Britain, representing the first successful war of independence against a European power. The current constitution was adopted in 1788, after the Articles of Confederation, the first ten amendments, collectively named the Bill of Rights, were ratified in 1791 and designed to guarantee many fundamental civil liberties. During the second half of the 19th century, the American Civil War led to the end of slavery in the country. By the end of century, the United States extended into the Pacific Ocean. The Spanish–American War and World War I confirmed the status as a global military power. The end of the Cold War and the dissolution of the Soviet Union in 1991 left the United States as the sole superpower. The U. S. is a member of the United Nations, World Bank, International Monetary Fund, Organization of American States. The United States is a developed country, with the worlds largest economy by nominal GDP. It ranks highly in several measures of performance, including average wage, human development, per capita GDP. While the U. S. economy is considered post-industrial, characterized by the dominance of services and knowledge economy, the United States is a prominent political and cultural force internationally, and a leader in scientific research and technological innovations. In 1507, the German cartographer Martin Waldseemüller produced a map on which he named the lands of the Western Hemisphere America after the Italian explorer and cartographer Amerigo Vespucci
25.
Europe
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Europe is a continent that comprises the westernmost part of Eurasia. Europe is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, yet the non-oceanic borders of Europe—a concept dating back to classical antiquity—are arbitrary. Europe covers about 10,180,000 square kilometres, or 2% of the Earths surface, politically, Europe is divided into about fifty sovereign states of which the Russian Federation is the largest and most populous, spanning 39% of the continent and comprising 15% of its population. Europe had a population of about 740 million as of 2015. Further from the sea, seasonal differences are more noticeable than close to the coast, Europe, in particular ancient Greece, was the birthplace of Western civilization. The fall of the Western Roman Empire, during the period, marked the end of ancient history. Renaissance humanism, exploration, art, and science led to the modern era, from the Age of Discovery onwards, Europe played a predominant role in global affairs. Between the 16th and 20th centuries, European powers controlled at times the Americas, most of Africa, Oceania. The Industrial Revolution, which began in Great Britain at the end of the 18th century, gave rise to economic, cultural, and social change in Western Europe. During the Cold War, Europe was divided along the Iron Curtain between NATO in the west and the Warsaw Pact in the east, until the revolutions of 1989 and fall of the Berlin Wall. In 1955, the Council of Europe was formed following a speech by Sir Winston Churchill and it includes all states except for Belarus, Kazakhstan and Vatican City. Further European integration by some states led to the formation of the European Union, the EU originated in Western Europe but has been expanding eastward since the fall of the Soviet Union in 1991. The European Anthem is Ode to Joy and states celebrate peace, in classical Greek mythology, Europa is the name of either a Phoenician princess or of a queen of Crete. The name contains the elements εὐρύς, wide, broad and ὤψ eye, broad has been an epithet of Earth herself in the reconstructed Proto-Indo-European religion and the poetry devoted to it. For the second part also the divine attributes of grey-eyed Athena or ox-eyed Hera. The same naming motive according to cartographic convention appears in Greek Ανατολή, Martin Litchfield West stated that phonologically, the match between Europas name and any form of the Semitic word is very poor. Next to these there is also a Proto-Indo-European root *h1regʷos, meaning darkness. Most major world languages use words derived from Eurṓpē or Europa to refer to the continent, in some Turkic languages the originally Persian name Frangistan is used casually in referring to much of Europe, besides official names such as Avrupa or Evropa
26.
Gulf Stream
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The process of western intensification causes the Gulf Stream to be a northward accelerating current off the east coast of North America. At about 40°0′N 30°0′W, it splits in two, with the stream, the North Atlantic Drift, crossing to Northern Europe and the southern stream. The Gulf Stream influences the climate of the east coast of North America from Florida to Newfoundland, and it is part of the North Atlantic Gyre. Its presence has led to the development of strong cyclones of all types, the Gulf Stream is also a significant potential source of renewable power generation. The Gulf Stream may be slowing down as a result of climate change, the Gulf Stream is typically 100 kilometres wide and 800 metres to 1,200 metres deep. The current velocity is fastest near the surface, with the maximum speed typically about 2.5 metres per second. European discovery of the Gulf Stream dates to the 1512 expedition of Juan Ponce de León and its existence was also known to Peter Martyr dAnghiera. Benjamin Franklin became interested in the North Atlantic Ocean circulation patterns, Franklin asked Timothy Folger, his cousin twice removed, a Nantucket Island whaling captain, for an answer. Franklin worked with Folger and other experienced ship captains, learning enough to chart the Gulf Stream and he offered this information to Anthony Todd, secretary of the British Post Office, but it was ignored by British sea captains. Franklins Gulf Stream chart was published in 1770 in England, where it was mostly ignored, subsequent versions were printed in France in 1778 and the U. S. in 1786. The Gulf Stream proper is a current, driven largely by wind stress. The North Atlantic Drift, in contrast, is largely thermohaline circulation–driven, in 1958 the oceanographer Henry Stommel noted that very little water from the Gulf of Mexico is actually in the Stream. By carrying warm water northeast across the Atlantic, it makes Western, a river of sea water, called the Atlantic North Equatorial Current, flows westward off the coast of Central Africa. When this current interacts with the northeastern coast of South America, one passes into the Caribbean Sea, while a second, the Antilles Current, flows north and east of the West Indies. These two branches north of the Straits of Florida. The trade winds blow westward in the tropics, and the westerlies blow eastward at mid-latitudes and this wind pattern applies a stress to the subtropical ocean surface with negative curl across the north Atlantic Ocean. The resulting Sverdrup transport is equatorward, the conservation of potential vorticity also causes bends along the Gulf Stream, which occasionally break off due to a shift in the Gulf Streams position, forming separate warm and cold eddies. This overall process, known as western intensification, causes currents on the boundary of an ocean basin, such as the Gulf Stream
27.
Thermometer
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A thermometer is a device that measures temperature or a temperature gradient. A thermometer has two important elements, a sensor in which some physical change occurs with temperature. Thermometers are widely used in industry to control and regulate processes, in the study of weather, in medicine, there are various principles by which different thermometers operate. They include the expansion of solids or liquids with temperature. Radiation-type thermometers measure the energy emitted by an object, allowing measurement of temperature without contact. Most metals are good conductors of heat and they are solids at room temperature, Mercury is the only one in liquid state at room temperature, and has high coefficient of expansion. Hence, the slightest change in temperature is notable when its used in a thermometer and this is the reason behind mercury and alcohol being used in thermometer. Some of the principles of the thermometer were known to Greek philosophers of two years ago. The modern thermometer gradually evolved from the thermoscope with the addition of a scale in the early 17th century, while an individual thermometer is able to measure degrees of hotness, the readings on two thermometers cannot be compared unless they conform to an agreed scale. Today there is a thermodynamic temperature scale. Internationally agreed temperature scales are designed to approximate this closely, based on fixed points, the most recent official temperature scale is the International Temperature Scale of 1990. It extends from 0.65 K to approximately 1,358 K, various authors have credited the invention of the thermometer to Hero of Alexandria. The thermometer was not an invention, however, but a development. The expansion and contraction of the air caused the position of the interface to move along the tube. Such a mechanism was used to show the hotness and coldness of the air with a tube in which the water level is controlled by the expansion and contraction of the gas. These devices were developed by several European scientists in the 16th and 17th centuries, as a result, devices were shown to produce this effect reliably, and the term thermoscope was adopted because it reflected the changes in sensible heat. The difference between a thermoscope and a thermometer is that the latter has a scale, though Galileo is often said to be the inventor of the thermometer, what he produced were thermoscopes. The first clear diagram of a thermoscope was published in 1617 by Giuseppe Biancani and this was a vertical tube, closed by a bulb of air at the top, with the lower end opening into a vessel of water
28.
Global warming
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Global warming and climate change are terms for the observed century-scale rise in the average temperature of the Earths climate system and its related effects. Multiple lines of evidence show that the climate system is warming. The largest human influence has been emission of gases such as carbon dioxide, methane. These findings have been recognized by the science academies of the major industrialized nations and are not disputed by any scientific body of national or international standing. Future climate change and associated impacts will differ from region to region around the globe, anticipated effects include warming global temperature, rising sea levels, changing precipitation, and expansion of deserts in the subtropics. Warming is expected to be greater over land than over the oceans and greatest in the Arctic, with the retreat of glaciers, permafrost. Effects significant to humans include the threat to security from decreasing crop yields. Possible societal responses to global warming include mitigation by emissions reduction, adaptation to its effects, building systems resilient to its effects, most countries are parties to the United Nations Framework Convention on Climate Change, whose ultimate objective is to prevent dangerous anthropogenic climate change. Public reactions to global warming and concern about its effects are also increasing, a global 2015 Pew Research Center report showed a median of 54% consider it a very serious problem. There are significant regional differences, with Americans and Chinese among the least concerned, the global average surface temperature shows a warming of 0.85 °C in the period 1880 to 2012, based on multiple independently produced datasets. Earths average surface temperature rose by 0. 74±0.18 °C over the period 1906–2005, the rate of warming almost doubled for the last half of that period. The rest has melted ice and warmed the continents and atmosphere, the average temperature of the lower troposphere has increased between 0.12 and 0.135 °C per decade since 1979, according to satellite temperature measurements. The warming that is evident in the temperature record is consistent with a wide range of observations. The probability that these changes could have occurred by chance is virtually zero, temperature changes vary over the globe. Since 1979, land temperatures have increased about twice as fast as ocean temperatures, ocean temperatures increase more slowly than land temperatures because of the larger effective heat capacity of the oceans and because the ocean loses more heat by evaporation. Since the beginning of industrialisation the temperature difference between the hemispheres has increased due to melting of sea ice and snow in the North. Average arctic temperatures have been increasing at almost twice the rate of the rest of the world in the past 100 years, the thermal inertia of the oceans and slow responses of other indirect effects mean that climate can take centuries or longer to adjust to changes in forcing. Some of this warming will be driven by past natural forcings which are still seeking equilibrium in the climate system
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Weather buoy
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Weather buoys are instruments which collect weather and ocean data within the worlds oceans, as well as aid during emergency response to chemical spills, legal proceedings, and engineering design. Moored buoys have been in use since 1951, while drifting buoys have been used since 1979, moored buoys are connected with the ocean bottom using either chains, nylon, or buoyant polypropylene. With the decline of the ship, they have taken a more primary role in measuring conditions over the open seas since the 1970s. During the 1980s and 1990s, a network of buoys in the central, moored weather buoys range from 1.5 metres to 12 metres in diameter, while drifting buoys are smaller, with diameters of 30 centimetres to 40 centimetres. Drifting buoys are the dominant form of weather buoy in sheer number, wind data from buoys has smaller error than that from ships. Starting in 1939, United States Coast Guard vessels were being used as weather ships to protect transatlantic air commerce, during World War II The German Navy deployed weather buoys at fifteen fixed positions in the North Atlantic and Barents Sea. They were launched from U-boats into a depth of ocean of 1000 fathoms. Overall height of the body was 10.5 metres, surmounted by a mast, Data were encoded and transmitted four times a day. When the batteries were exhausted, after eight to ten weeks. The Navy Oceanographic Meteorological Automatic Device buoys 6-metre hull was designed in the 1940s for the United States Navy’s offshore data collection program. Between 1951 and 1970, a total of 21 NOMAD buoys were built, since the 1970s, weather buoy use has superseded the role of weather ships by design, as they are cheaper to operate and maintain. The earliest reported use of drifting buoys was to study the behavior of ocean currents within the Sargasso Sea in 1972 and 1973, drifting buoys have been used increasingly since 1979, and as of 2005,1250 drifting buoys roamed the Earths oceans. Between 1985 and 1994, an array of moored and drifting buoys was deployed across the equatorial Pacific Ocean designed to help monitor. Hurricane Katrina capsized a 10 m buoy for the first time in the history of the National Data Buoy Center on August 28,2005, the first weather buoy in the Southern Ocean was deployed by the Integrated Marine Observing System on March 17,2010. Weather buoys, like other types of stations, measure parameters such as air temperature above the ocean surface, wind speed, barometric pressure. Since they lie in oceans and lakes, they also measure water temperature, wave height, both moored buoys and drifting buoys are used. Fixed buoys measure the temperature at a depth of 3 metres. Many different drifting buoys exist around the world vary in design
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National Data Buoy Center
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The National Data Buoy Center is a part of the National Oceanic and Atmospheric Administrations National Weather Service. NDBC designs, develops, operates, and maintains a network of data collecting buoys, the NBDC is located in southern Mississippi as a tenant at the John C. Stennis Space Center, a National Aeronautics and Space Administration facility. NDBC employs engineers, meteorologists, oceanographers, computer scientists, NDBC provides hourly observations from a network of about 90 buoys and 60 Coastal Marine Automated Network stations to help meet these needs. All stations measure wind speed, direction, and gust, atmospheric pressure, in addition, all buoy stations, and some C-MAN stations, measure sea surface temperature and wave height and period. Conductivity and water current are measured at selected stations, a new task is the operation of the DART buoys. DART is a fleet of tsunami detecting buoys, another task adopted in 2005 is TAO buoys. TAO is a fleet of over 50 buoys moored in the Pacific Ocean and these buoys are designed to help detect and predict El Niño and La Niña. All buoys and many C-MAN stations located in offshore areas operate on batteries which are charged by solar cells. Sensors are calibrated in wind tunnels or environmental chambers, and later tested with the onboard station microprocessors, called payloads, final calibration and testing of the completed buoy systems are accomplished in the onsite canal. All buoys are serviced about every two years for maintenance and to install newly calibrated sensors. Additionally, some buoys and C-MAN stations may use the Iridium satellite system to transmit data, the data is recorded and processed by the National Oceanographic Data Center. Through a Memorandum of Agreement, the United States Coast Guard remains an important partner to NDBC, supplying transportation for buoy deployments, retrievals. The National Data Buoy Development Program, created in 1967, was placed under the control of the USCG, in 1970, NOAA was formed and the NOAA Data Buoy Office was created within the National Ocean Service and located in Mississippi. In 1982, the NDBO was renamed NDBC and was placed under NOAAs NWS, the first buoys deployed by NDBC were the large 12-m discus hulls constructed of steel. These were generally deployed in deep water off the U. S, east Coast and in the Gulf of Mexico. By 1979,16 stations were deployed in the Pacific,7 in the Atlantic, eight more stations were deployed in the Great Lakes after 1979. In 1995, development of the Deep-ocean Assessment and Reporting of Tsunamis system began, following the 2004 Indian Ocean earthquake and its subsequent tsunamis, additional dart buoys were deployed. NDBCs main office is located in southern Mississippi at the John C. Stennis Space Center and this site was chosen because it contains an excellent pre-existing industrial facility which is adjacent to a canal with deep-water access to the Gulf of Mexico
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Moderate-resolution imaging spectroradiometer
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The instruments capture data in 36 spectral bands ranging in wavelength from 0.4 µm to 14.4 µm and at varying spatial resolutions. Together the instruments image the entire Earth every 1 to 2 days, MODIS has used the marine optical buoy for vicarious calibration. MODIS is succeeded by the VIIRS instrument on board the Suomi NPP satellite launched in 2011, the MODIS characterization support team is dedicated to the production of high-quality MODIS calibrated product which is a precursor to every geophysical science product. A detailed description of the MCST mission statement and other details can be found at MCST Web, with its low spatial resolution but high temporal resolution, MODIS data is useful to track changes in the landscape over time. The United States Forest Services Remote Sensing Applications Center analyzes MODIS imagery on a basis to provide information for the management. The following MODIS Level 3 datasets are available from NASA, as processed by the Collection 5 software, most of the data is available in the HDF-EOS format — a variant of Hierarchical Data Format prescribed for the data derived from Earth Observing System missions. Imaging spectroscopy NASA World Wind Official NASA site MODIS bands and spectral ranges MODIS Images of the Day MODIS Image of the Day – Google Gadget referring to MODIS image of the day
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Satellite
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In the context of spaceflight, a satellite is an artificial object which has been intentionally placed into orbit. Such objects are called artificial satellites to distinguish them from natural satellites such as Earths Moon. In 1957 the Soviet Union launched the worlds first artificial satellite, since then, about 6,600 satellites from more than 40 countries have been launched. According to a 2013 estimate,3,600 remained in orbit, of those, about 1,000 were operational, the rest have lived out their useful lives and become space debris. Approximately 500 operational satellites are in orbit,50 are in medium-Earth orbit. A few large satellites have been launched in parts and assembled in orbit. Over a dozen space probes have been placed into orbit around other bodies and become artificial satellites to the Moon, Mercury, Venus, Mars, Jupiter, Saturn, a few asteroids, Satellites are used for many purposes. Common types include military and civilian Earth observation satellites, communications satellites, navigation satellites, weather satellites, Space stations and human spacecraft in orbit are also satellites. Satellite orbits vary greatly, depending on the purpose of the satellite, well-known classes include low Earth orbit, polar orbit, and geostationary orbit. A launch vehicle is a rocket that throws a satellite into orbit, usually it lifts off from a launch pad on land. Some are launched at sea from a submarine or a mobile maritime platform, Satellites are usually semi-independent computer-controlled systems. Satellite subsystems attend many tasks, such as power generation, thermal control, telemetry, attitude control, the first fictional depiction of a satellite being launched into orbit was a short story by Edward Everett Hale, The Brick Moon. The idea surfaced again in Jules Vernes The Begums Fortune, in 1903, Konstantin Tsiolkovsky published Exploring Space Using Jet Propulsion Devices, which is the first academic treatise on the use of rocketry to launch spacecraft. He calculated the speed required for a minimal orbit. In 1928, Herman Potočnik published his book, The Problem of Space Travel — The Rocket Motor. He described the use of orbiting spacecraft for observation of the ground, in a 1945 Wireless World article, the English science fiction writer Arthur C. Clarke described in detail the possible use of communications satellites for mass communications. He suggested that three geostationary satellites would provide coverage over the entire planet, the first artificial satellite was Sputnik 1, launched by the Soviet Union on October 4,1957, and initiating the Soviet Sputnik program, with Sergei Korolev as chief designer. This in turn triggered the Space Race between the Soviet Union and the United States, Sputnik 1 helped to identify the density of high atmospheric layers through measurement of its orbital change and provided data on radio-signal distribution in the ionosphere
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Time
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Time is the indefinite continued progress of existence and events that occur in apparently irreversible succession from the past through the present to the future. Time is often referred to as the dimension, along with the three spatial dimensions. Time has long been an important subject of study in religion, philosophy, and science, nevertheless, diverse fields such as business, industry, sports, the sciences, and the performing arts all incorporate some notion of time into their respective measuring systems. Two contrasting viewpoints on time divide prominent philosophers, one view is that time is part of the fundamental structure of the universe—a dimension independent of events, in which events occur in sequence. Isaac Newton subscribed to this realist view, and hence it is referred to as Newtonian time. This second view, in the tradition of Gottfried Leibniz and Immanuel Kant, holds that time is neither an event nor a thing, Time in physics is unambiguously operationally defined as what a clock reads. Time is one of the seven fundamental physical quantities in both the International System of Units and International System of Quantities, Time is used to define other quantities—such as velocity—so defining time in terms of such quantities would result in circularity of definition. The operational definition leaves aside the question there is something called time, apart from the counting activity just mentioned, that flows. Investigations of a single continuum called spacetime bring questions about space into questions about time, questions that have their roots in the works of early students of natural philosophy. Furthermore, it may be there is a subjective component to time. Temporal measurement has occupied scientists and technologists, and was a motivation in navigation. Periodic events and periodic motion have long served as standards for units of time, examples include the apparent motion of the sun across the sky, the phases of the moon, the swing of a pendulum, and the beat of a heart. Currently, the unit of time, the second, is defined by measuring the electronic transition frequency of caesium atoms. Time is also of significant social importance, having economic value as well as value, due to an awareness of the limited time in each day. In day-to-day life, the clock is consulted for periods less than a day whereas the calendar is consulted for periods longer than a day, increasingly, personal electronic devices display both calendars and clocks simultaneously. The number that marks the occurrence of an event as to hour or date is obtained by counting from a fiducial epoch—a central reference point. Artifacts from the Paleolithic suggest that the moon was used to time as early as 6,000 years ago. Lunar calendars were among the first to appear, either 12 or 13 lunar months, without intercalation to add days or months to some years, seasons quickly drift in a calendar based solely on twelve lunar months
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In situ
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In situ is a Latin phrase that translates literally to on site or in position. It means locally, on site, on the premises or in place to describe an event where it takes place, in the aerospace industry, equipment on-board aircraft must be tested in situ, or in place, to confirm everything functions properly as a system. Individually, each piece may work but interference from nearby equipment may create unanticipated problems, special test equipment is available for this in situ testing. In archaeology, in situ refers to an artifact that has not been moved from its place of deposition. In other words, it is stationary, meaning still, an artifact being in situ is critical to the interpretation of that artifact and, consequently, of the culture which formed it. Once an artifacts find-site has been recorded, the artifact can then be moved for conservation, further interpretation, an artifact that is not discovered in situ is considered out of context and as not providing an accurate picture of the associated culture. However, the out of context artifact can provide scientists with an example of types, when excavating a burial site or surface deposit in situ refers to cataloging, recording, mapping, photographing human remains in the position they are discovered. The label in situ indicates only that the object has not been newly moved. Thus, an archaeological in situ find may be an object that was looted from another place, an item of booty of a past war. Consequently, the in situ find site may not reveal its provenance. It is also possible for archaeological layers to be reworked on purpose or by accident, for example, in a Tell mound, where layers are not typically uniform or horizontal, or in land cleared or tilled for farming. The term in situ is used to describe ancient sculpture that was carved in place such as the Sphinx or Petra. This distinguishes it from statues that were carved and moved like the Colossi of Memnon, which was moved in ancient times. In art, in situ refers to a work of art made specifically for a host site, for a more detailed account see, Site-specific art. The term can refer to a work of art created at the site where it is to be displayed, rather than one created in the artists studio. In architectural sculpture the term is employed to describe sculpture that is carved on a building, frequently from scaffolds. A fraction of the star clusters in our galaxy, as well as those in other massive galaxies. The rest might have been accreted from now defunct dwarf galaxies, in biology and biomedical engineering, in situ means to examine the phenomenon exactly in place where it occurs
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Radiation
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In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or through a material medium. Radiation is often categorized as either ionizing or non-ionizing depending on the energy of the radiated particles, Ionizing radiation carries more than 10 eV, which is enough to ionize atoms and molecules, and break chemical bonds. This is an important distinction due to the difference in harmfulness to living organisms. A common source of ionizing radiation is radioactive materials that emit α, β, or γ radiation, consisting of helium nuclei, electrons or positrons, gamma rays, X-rays and the higher energy range of ultraviolet light constitute the ionizing part of the electromagnetic spectrum. The lower-energy, longer-wavelength part of the spectrum including visible light, infrared light, microwaves and this type of radiation only damages cells if the intensity is high enough to cause excessive heating. Ultraviolet radiation has some features of both ionizing and non-ionizing radiation and these properties derive from ultraviolets power to alter chemical bonds, even without having quite enough energy to ionize atoms. The word radiation arises from the phenomenon of waves radiating from a source and this aspect leads to a system of measurements and physical units that are applicable to all types of radiation. This law does not apply close to a source of radiation or for focused beams. Radiation with sufficiently high energy can ionize atoms, that is to say it can knock electrons off atoms, ionization occurs when an electron is stripped from an electron shell of the atom, which leaves the atom with a net positive charge. Because living cells and, more importantly, the DNA in those cells can be damaged by this ionization, thus ionizing radiation is somewhat artificially separated from particle radiation and electromagnetic radiation, simply due to its great potential for biological damage. While an individual cell is made of trillions of atoms, only a fraction of those will be ionized at low to moderate radiation powers. If the source of the radiation is a radioactive material or a nuclear process such as fission or fusion. Particle radiation is subatomic particles accelerated to relativistic speeds by nuclear reactions, because of their momenta they are quite capable of knocking out electrons and ionizing materials, but since most have an electrical charge, they dont have the penetrating power of ionizing radiation. The exception is neutron particles, see below, there are several different kinds of these particles, but the majority are alpha particles, beta particles, neutrons, and protons. Roughly speaking, photons and particles with energies above about 10 electron volts are ionizing, particle radiation from radioactive material or cosmic rays almost invariably carries enough energy to be ionizing. The radiation is invisible and not directly detectable by human senses, as a result, in some cases, it may lead to secondary emission of visible light upon its interaction with matter, as in the case of Cherenkov radiation and radio-luminescence. Ionizing radiation has many uses in medicine, research and construction. Ultraviolet, of wavelengths from 10 nm to 125 nm, ionizes air molecules, causing it to be absorbed by air
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Infrared
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It extends from the nominal red edge of the visible spectrum at 700 nanometers, to 1000000 nm. Most of the radiation emitted by objects near room temperature is infrared. Like all EMR, IR carries radiant energy, and behaves both like a wave and like its quantum particle, the photon, slightly more than half of the total energy from the Sun was eventually found to arrive on Earth in the form of infrared. The balance between absorbed and emitted infrared radiation has an effect on Earths climate. Infrared radiation is emitted or absorbed by molecules when they change their rotational-vibrational movements and it excites vibrational modes in a molecule through a change in the dipole moment, making it a useful frequency range for study of these energy states for molecules of the proper symmetry. Infrared spectroscopy examines absorption and transmission of photons in the infrared range, Infrared radiation is used in industrial, scientific, and medical applications. Night-vision devices using active near-infrared illumination allow people or animals to be observed without the observer being detected, Infrared thermal-imaging cameras are used to detect heat loss in insulated systems, to observe changing blood flow in the skin, and to detect overheating of electrical apparatuses. Thermal-infrared imaging is used extensively for military and civilian purposes, military applications include target acquisition, surveillance, night vision, homing, and tracking. Humans at normal body temperature radiate chiefly at wavelengths around 10 μm, Infrared radiation extends from the nominal red edge of the visible spectrum at 700 nanometers to 1 mm. This range of wavelengths corresponds to a range of approximately 430 THz down to 300 GHz. Below infrared is the portion of the electromagnetic spectrum. Sunlight, at a temperature of 5,780 kelvins, is composed of near thermal-spectrum radiation that is slightly more than half infrared. At zenith, sunlight provides an irradiance of just over 1 kilowatt per square meter at sea level, of this energy,527 watts is infrared radiation,445 watts is visible light, and 32 watts is ultraviolet radiation. Nearly all the radiation in sunlight is near infrared, shorter than 4 micrometers. On the surface of Earth, at far lower temperatures than the surface of the Sun, almost all thermal radiation consists of infrared in mid-infrared region, much longer than in sunlight. Of these natural thermal radiation processes only lightning and natural fires are hot enough to produce much visible energy, thermal infrared radiation also has a maximum emission wavelength, which is inversely proportional to the absolute temperature of object, in accordance with Wiens displacement law. Therefore, the band is often subdivided into smaller sections. Due to the nature of the blackbody radiation curves, typical hot objects, such as exhaust pipes, the three regions are used for observation of different temperature ranges, and hence different environments in space
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Electromagnetic spectrum
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The electromagnetic spectrum is the collective term for all known frequencies and their linked wavelengths of the known photons. The electromagnetic spectrum of an object has a different meaning, and is instead the characteristic distribution of radiation emitted or absorbed by that particular object. Visible light lies toward the end, with wavelengths from 400 to 700 nanometres. The limit for long wavelengths is the size of the universe itself, until the middle of the 20th century it was believed by most physicists that this spectrum was infinite and continuous. Nearly all types of radiation can be used for spectroscopy, to study. Other technological uses are described under electromagnetic radiation, for most of history, visible light was the only known part of the electromagnetic spectrum. The ancient Greeks recognized that light traveled in straight lines and studied some of its properties, the study of light continued, and during the 16th and 17th centuries conflicting theories regarded light as either a wave or a particle. The first discovery of electromagnetic radiation other than visible light came in 1800 and he was studying the temperature of different colors by moving a thermometer through light split by a prism. He noticed that the highest temperature was beyond red and he theorized that this temperature change was due to calorific rays that were a type of light ray that could not be seen. The next year, Johann Ritter, working at the end of the spectrum. These behaved similarly to visible light rays, but were beyond them in the spectrum. They were later renamed ultraviolet radiation, during the 1860s James Maxwell developed four partial differential equations for the electromagnetic field. Two of these equations predicted the possibility of, and behavior of, analyzing the speed of these theoretical waves, Maxwell realized that they must travel at a speed that was about the known speed of light. This startling coincidence in value led Maxwell to make the inference that light itself is a type of electromagnetic wave, maxwells equations predicted an infinite number of frequencies of electromagnetic waves, all traveling at the speed of light. This was the first indication of the existence of the electromagnetic spectrum. Maxwells predicted waves included waves at very low compared to infrared. Hertz found the waves and was able to infer that they traveled at the speed of light, Hertz also demonstrated that the new radiation could be both reflected and refracted by various dielectric media, in the same manner as light. For example, Hertz was able to focus the waves using a lens made of tree resin, in a later experiment, Hertz similarly produced and measured the properties of microwaves
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Black-body radiation
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Black-body radiation is the thermal electromagnetic radiation within or surrounding a body in thermodynamic equilibrium with its environment, or emitted by a black body. It has a spectrum and intensity that depends only on the bodys temperature. The thermal radiation emitted by many ordinary objects can be approximated as black-body radiation. A black-body at room temperature appears black, as most of the energy it radiates is infra-red, when it becomes a little hotter, it appears dull red. As its temperature increases further it eventually becomes blue-white, although planets and stars are neither in thermal equilibrium with their surroundings nor perfect black bodies, black-body radiation is used as a first approximation for the energy they emit. Black holes are near-perfect black bodies, in the sense that they absorb all the radiation that falls on them and it has been proposed that they emit black-body radiation, with a temperature that depends on the mass of the black hole. The term black body was introduced by Gustav Kirchhoff in 1860, Black-body radiation is also called thermal radiation, cavity radiation, complete radiation or temperature radiation. Black-body radiation has a characteristic, continuous spectrum that depends only on the bodys temperature. As the temperature increases past about 500 degrees Celsius, black start to emit significant amounts of visible light. Viewed in the dark by the eye, the first faint glow appears as a ghostly grey. When the body appears white, it is emitting a substantial fraction of its energy as ultraviolet radiation, Black-body radiation provides insight into the thermodynamic equilibrium state of cavity radiation. Instead, in theory the occupation numbers of the modes are quantized, cutting off the spectrum at high frequency in agreement with experimental observation. The study of the laws of black bodies and the failure of classical physics to describe them helped establish the foundations of quantum mechanics, all normal matter emits electromagnetic radiation when it has a temperature above absolute zero. The radiation represents a conversion of a thermal energy into electromagnetic energy. It is a process of radiative distribution of entropy. Conversely all normal matter absorbs electromagnetic radiation to some degree, an object that absorbs all radiation falling on it, at all wavelengths, is called a black body. When a black body is at a temperature, its emission has a characteristic frequency distribution that depends on the temperature. Its emission is called black-body radiation, the concept of the black body is an idealization, as perfect black bodies do not exist in nature
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Synoptic scale meteorology
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The synoptic scale in meteorology is a horizontal length scale of the order of 1000 kilometres or more. This corresponds to a horizontal scale typical of mid-latitude depressions, most high and low-pressure areas seen on weather maps such as surface weather analyses are synoptic-scale systems, driven by the location of Rossby waves in their respective hemisphere. Low-pressure areas and their related frontal zones occur on the edge of a trough within the Rossby wave pattern. Most precipitation areas occur near frontal zones, the word synoptic is derived from the Greek word συνοπτικός, meaning seen together. The Navier–Stokes equations applied to atmospheric motion can be simplified by scale analysis in the synoptic scale and it can be shown that the main terms in horizontal equations are Coriolis force and pressure gradient terms, therefore, one can use geostrophic approximation. In vertical coordinates, the equation simplifies to the hydrostatic equilibrium equation. The first weather maps in the 19th century were drawn well after the fact to help devise a theory on storm systems, use of surface analyses began first in the United States, spreading worldwide during the 1870s. Use of the Norwegian cyclone model for frontal analysis began in the late 1910s across Europe, surface weather analyses have special symbols which show frontal systems, cloud cover, precipitation, or other important information. For example, an H represents high pressure, implying good, an L represents low pressure, which frequently accompanies precipitation. Various symbols are used not just for frontal zones and other surface boundaries on weather maps, areas of precipitation help determine the frontal type and location. Mesoscale systems and boundaries such as cyclones, outflow boundaries. Isobars are commonly used to place surface boundaries from the horse latitudes poleward, the descriptor extratropical refers to the fact that this type of cyclone generally occurs outside of the tropics, in the middle latitudes of the planet. These are the phenomena which along with anti-cyclones, drive the weather over much of the Earth. An extratropical cyclone can transform into a storm, and from there into a tropical cyclone, if it dwells over warm waters and develops central convection. High-pressure systems are associated with light winds at the surface and subsidence through the lower portion of the troposphere. Subsidence will generally dry out an air mass by adiabatic, or compressional, thus, high pressure typically brings clear skies. During the day, since no clouds are present to reflect sunlight, there is more incoming solar radiation. At night, the absence of means that outgoing longwave radiation is not absorbed
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Geostationary orbit
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A geostationary orbit, geostationary Earth orbit or geosynchronous equatorial orbit is a circular orbit 35,786 kilometres above the Earths equator and following the direction of the Earths rotation. An object in such an orbit has a period equal to the Earths rotational period and thus appears motionless, at a fixed position in the sky. Using this characteristic, ocean color satellites with visible and near-infrared light sensors can also be operated in geostationary orbit in order to monitor sensitive changes of ocean environments, the notion of a geostationary space station equipped with radio communication was published in 1928 by Herman Potočnik. The first appearance of an orbit in popular literature was in the first Venus Equilateral story by George O. Smith. Clarke acknowledged the connection in his introduction to The Complete Venus Equilateral, the orbit, which Clarke first described as useful for broadcast and relay communications satellites, is sometimes called the Clarke Orbit. Similarly, the Clarke Belt is the part of space about 35,786 km above sea level, in the plane of the equator, the Clarke Orbit is about 265,000 km in circumference. Most commercial communications satellites, broadcast satellites and SBAS satellites operate in geostationary orbits, a geostationary transfer orbit is used to move a satellite from low Earth orbit into a geostationary orbit. The first satellite placed into an orbit was the Syncom-3. A worldwide network of operational geostationary meteorological satellites is used to provide visible and infrared images of Earths surface, a geostationary orbit can only be achieved at an altitude very close to 35,786 km and directly above the equator. This equates to a velocity of 3.07 km/s and an orbital period of 1,436 minutes. This ensures that the satellite will match the Earths rotational period and has a footprint on the ground. All geostationary satellites have to be located on this ring. 85° per year, to correct for this orbital perturbation, regular orbital stationkeeping manoeuvres are necessary, amounting to a delta-v of approximately 50 m/s per year. A second effect to be taken into account is the longitude drift, there are two stable and two unstable equilibrium points. Any geostationary object placed between the points would be slowly accelerated towards the stable equilibrium position, causing a periodic longitude variation. The correction of this effect requires station-keeping maneuvers with a maximal delta-v of about 2 m/s per year, solar wind and radiation pressure also exert small forces on satellites, over time, these cause them to slowly drift away from their prescribed orbits. In the absence of servicing missions from the Earth or a renewable propulsion method, hall-effect thrusters, which are currently in use, have the potential to prolong the service life of a satellite by providing high-efficiency electric propulsion. This delay presents problems for latency-sensitive applications such as voice communication, geostationary satellites are directly overhead at the equator and become lower in the sky the further north or south one travels. At latitudes above about 81°, geostationary satellites are below the horizon, because of this, some Russian communication satellites have used elliptical Molniya and Tundra orbits, which have excellent visibility at high latitudes
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Sea surface microlayer
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The sea surface microlayer is the top 1000 micrometers of the ocean surface. It is the layer where all exchange occurs between the atmosphere and the ocean. The chemical, physical, and biological properties of the SML differ greatly from the water just a few centimeters beneath. Organic compounds such as acids, carbohydrates, fatty acids. The relative concentration of compounds is dependent on the nutrient sources as well as climate conditions such as wind speed. These organic compounds on the create a film, referred to as a slick when visible. These films occur because of the tendencies of many organic compounds. The existence of organic surfactants on the ocean surface wave formation for low wind speeds. For increasing concentrations of surfactant there is an increasing critical wind speed necessary to create ocean waves, increased levels of organic compounds at the surface also hinders air-sea gas exchange at low wind speeds. One way in which particulates and organic compounds on the surface are transported into the atmosphere is the process called bubble bursting, bubbles generate the major portion of marine aerosols. They can be dispersed to heights of several meters, picking up whatever particles latch on to their surface, however, the major supplier of materials comes from the SML. Extensive research has shown that the SML contains elevated concentration of bacteria, viruses, toxic metals and these materials can be transferred from the sea-surface to the atmosphere in the form of wind-generated aqueous aerosols due to their high vapor tension and a process known as volatilisation. When airborne, these microbes can be transported long distances to coastal regions, if they hit land they can have detrimental effects on animals, vegetation and human health. Marine aerosols that contain viruses can travel hundreds of kilometers from their source and these aerosols are able to remain suspended in the atmosphere for about 31 days. Evidence suggests that bacteria can remain viable after being transported inland through aerosols, some reached as far as 200 meters at 30 meters above sea level. It was also noted that the process which transfers this material to the atmosphere causes further enrichment in both bacteria and viruses in comparison to either the SML or sub-surface waters. Devices used to sample the concentrations of particulates and compounds of the SML include a glass fabric, metal mesh screens and these are placed on a rotating cylinder which collects surface samples as it rotates on top of the ocean surface
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Aral Sea
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The Aral Sea was an endorheic lake lying between Kazakhstan in the north and Uzbekistan in the south. The name roughly translates as Sea of Islands, referring to over 1,100 islands that once dotted its waters, in the Turkic languages aral means island, the Aral Sea drainage basin encompasses Uzbekistan and parts of Tajikistan, Turkmenistan, Kyrgyzstan, Kazakhstan, Afghanistan and Pakistan. Satellite images taken by NASA in August 2014 revealed that for the first time in history the eastern basin of the Aral Sea had completely dried up. The eastern basin is now called the Aralkum Desert, in an ongoing effort in Kazakhstan to save and replenish the North Aral Sea, a dam project was completed in 2005, in 2008, the water level in this lake had risen by 12 m compared to 2003. Salinity has dropped, and fish are found in sufficient numbers for some fishing to be viable. The maximum depth of the North Aral Sea is 42 m, the shrinking of the Aral Sea has been called one of the planets worst environmental disasters. The regions once-prosperous fishing industry has been destroyed, bringing unemployment. The Aral Sea region is heavily polluted, with consequential serious public health problems. The historical documents of the development of the Aral Sea have added by UNESCO to its Memory of the World Register as a source to study this environmental tragedy. The Aral Sea formed about 5.5 million years ago due to a fall in sea level, the Syr Darya formed a large lake in the Kyzyl Kum during the Pliocene known as the Mynbulak depression. Most of the area around the Aral Sea was inhabited by nomads who left few written records. However, the Oxus delta to the south has a history under the name of Khwarezm. It used to be the westernmost border of Tang dynasty China, Russian naval presence on the Aral Sea started in 1847, with the founding of Raimsk, which was soon renamed Fort Aralsk, near the mouth of the Syr Darya. Soon, the Imperial Russian Navy started deploying its vessels on the sea, owing to the Aral Sea basin not being connected to other bodies of water, the vessels had to be disassembled in Orenburg on the Ural River, shipped overland to Aralsk, and then reassembled. The first two ships, assembled in 1847, were the two-masted schooners named Nikolai and Mikhail, the former was a warship, the latter was a merchant vessel meant to serve the establishment of the fisheries on the great lake. In 1848, these two surveyed the northern part of the sea. In the same year, a warship, the Constantine, was assembled. Commanded by Lt. Alexey Butakov, the Constantine completed the survey of the entire Aral Sea over the two years
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Ekman transport
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Ekman transport, part of Ekman motion theory first investigated in 1902 by Vagn Walfrid Ekman, is the term given for the 90° net transport of the surface layer of a fluid by wind forcing. This phenomenon was first noted by Fridtjof Nansen, who recorded that ice transport appeared to occur at an angle to the wind direction during his Arctic expedition during the 1890s. Ekman theory explains the state of circulation if water currents were driven only by the transfer of momentum from the wind. In the physical world, this is difficult to observe because of the influences of many simultaneous current driving forces, though the following theory technically applies to the idealized situation involving only wind forces, Ekman motion describes the wind-driven portion of circulation seen in the surface layer. Surface currents flow at a 45° angle to the due to a balance between the Coriolis force and the drags generated by the wind and the water. If the ocean is divided vertically into thin layers, the magnitude of the velocity decreases from a maximum at the surface until it dissipates, the direction also shifts slightly across each subsequent layer. This is called the Ekman spiral, the layer of water from the surface to the point of dissipation of this spiral is known as the Ekman layer. If all flow over the Ekman layer is integrated, the net transportation is at 90° to the right of the wind in the northern hemisphere. Some assumptions of the dynamics involved in the process must be made in order to simplify the process to a point where it is solvable. Here M x and M y represent the zonal and meridional mass transport terms with units of mass per time per unit length. Contrarily to common logic, north-south winds cause mass transport in the East-West direction, in order to understand the vertical velocity structure of the water column, equations 1 and 2 can be rewritten in terms of the vertical eddy viscosity term. ∂ τ x ∂ z = ρ A z ∂2 u ∂ z 2, ∂ τ y ∂ z = ρ A z ∂2 v ∂ z 2, where A z is the vertical eddy viscosity coefficient. This gives a set of equations of the form A z ∂2 u ∂ z 2 = − f v, A z ∂2 v ∂ z 2 = f u. In order to solve this system of two equations, two boundary conditions can be applied, →0 as z → ∞, friction is equal to wind stress at the free surface. Things can be simplified by considering wind blowing in the y-direction only. By solving this at z=0, the current is found to be 45 degrees to the right of the wind in the Northern Hemisphere. This also gives the shape of the Ekman spiral, both in magnitude and direction. Integrating these equations over the Ekman layer shows that the net Ekman transport term is 90 degrees to the right of the wind in the Northern Hemisphere
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River delta
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A river delta is a landform that forms from deposition of sediment carried by a river as the flow leaves its mouth and enters slower-moving or standing water. This occurs where a river enters an ocean, sea, estuary, lake, reservoir, River deltas are ecologically important as they provide coastline defense, are home to many species, and can impact drinking water supply. The tidal currents also cannot be too strong, as sediment would wash out into the body faster than the river deposits it. Of course, the river must carry enough sediment to layer into deltas over time, the rivers velocity decreases rapidly, causing it to deposit the majority, if not all, of its load. This alluvium builds up to form the river delta, when the flow enters the standing water, it is no longer confined to its channel and expands in width. This flow expansion results in a decrease in the flow velocity, as a result, sediment drops out of the flow and deposits. Over time, this single channel builds a deltaic lobe, pushing its mouth into the standing water, as the deltaic lobe advances, the gradient of the river channel becomes lower because the river channel is longer but has the same change in elevation. As the slope of the channel decreases, it becomes unstable for two reasons. First, gravity makes the flow in the most direct course down slope. If the river breaches its natural levees, it out onto a new course with a shorter route to the ocean. Second, as its slope gets lower, the amount of stress on the bed decreases, which results in deposition of sediment within the channel. This makes it easier for the river to breach its levees, often when the channel does this, some of its flow remains in the abandoned channel. When these channel-switching events occur, a mature delta develops a distributary network, another way these distributary networks form is from deposition of mouth bars. When this mid-channel bar is deposited at the mouth of a river and this results in additional deposition on the upstream end of the mouth-bar, which splits the river into two distributary channels. A good example of the result of this process is the Wax Lake Delta, in both of these cases, depositional processes force redistribution of deposition from areas of high deposition to areas of low deposition. This results in the smoothing of the shape of the delta as the channels move across its surface. Because the sediment is laid down in fashion, the shape of these deltas approximates a fan. The more often the flow changes course, the shape develops as closer to an ideal fan, the Mississippi and Ural River deltas, with their birds-feet, are examples of rivers that do not avulse often enough to form a symmetrical fan shape
. PMID 24567051.
This article incorporates public domain material from websites or documents of the National Oceanic and Atmospheric Administration.
