Reborrowing is the process where a word travels from one language to another and then back to the originating language in a different form or with a different meaning. A reborrowed word is sometimes called a Rückwanderer (German, a 'returner').
116-471: A tornado is a violently rotating column of air that is in contact with both the surface of the Earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud . It is often referred to as a twister , whirlwind or cyclone , although the word cyclone is used in meteorology to name a weather system with a low-pressure area in the center around which, from an observer looking down toward
232-469: A thunderstorm is blown through a mass of stationary, warm, moist air near the outflow boundary, resulting in a "rolling" effect (often exemplified through a roll cloud ). If low level wind shear is strong enough, the rotation can be turned vertically or diagonally and make contact with the ground. The result is a gustnado. They usually cause small areas of heavier rotational wind damage among areas of straight-line wind damage. A dust devil (also known as
348-521: A "rope tornado". When they rope out, the length of their funnel increases, which forces the winds within the funnel to weaken due to conservation of angular momentum . Multiple-vortex tornadoes can appear as a family of swirls circling a common center, or they may be completely obscured by condensation, dust, and debris, appearing to be a single funnel. In the United States, tornadoes are around 500 feet (150 m) across on average. However, there
464-492: A T0 for extremely weak tornadoes to T11 for the most powerful known tornadoes. Doppler weather radar data, photogrammetry , and ground swirl patterns ( cycloidal marks) may also be analyzed to determine intensity and award a rating. Tornadoes vary in intensity regardless of shape, size, and location, though strong tornadoes are typically larger than weak tornadoes. The association with track length and duration also varies, although longer track tornadoes tend to be stronger. In
580-440: A block of dark clouds, wider than the distance from the cloud base to the ground. Even experienced storm observers may not be able to tell the difference between a low-hanging cloud and a wedge tornado from a distance. Many, but not all major tornadoes are wedges. Tornadoes in the dissipating stage can resemble narrow tubes or ropes, and often curl or twist into complex shapes. These tornadoes are said to be "roping out", or becoming
696-459: A body of water (as a waterspout), tornadoes can turn white or even blue. Slow-moving funnels, which ingest a considerable amount of debris and dirt, are usually darker, taking on the color of debris. Tornadoes in the Great Plains can turn red because of the reddish tint of the soil, and tornadoes in mountainous areas can travel over snow-covered ground, turning white. Lighting conditions are
812-435: A boundary marked in most places by a temperature inversion (i.e. a layer of relatively warm air above a colder one), and in others by a zone that is isothermal with height. Although variations do occur, the temperature usually declines with increasing altitude in the troposphere because the troposphere is mostly heated through energy transfer from the surface. Thus, the lowest part of the troposphere (i.e. Earth's surface)
928-538: A continuous, deep rumbling, or an irregular sound of "noise". Since many tornadoes are audible only when very near, sound is not to be thought of as a reliable warning signal for a tornado. Tornadoes are also not the only source of such sounds in severe thunderstorms; any strong, damaging wind, a severe hail volley, or continuous thunder in a thunderstorm may produce a roaring sound. Tornadoes also produce identifiable inaudible infrasonic signatures. Unlike audible signatures, tornadic signatures have been isolated; due to
1044-505: A factor of 1/ e (0.368) every 7.64 km (25,100 ft), (this is called the scale height ) -- for altitudes out to around 70 km (43 mi; 230,000 ft). However, the atmosphere is more accurately modeled with a customized equation for each layer that takes gradients of temperature, molecular composition, solar radiation and gravity into account. At heights over 100 km, an atmosphere may no longer be well mixed. Then each chemical species has its own scale height. In summary,
1160-461: A few rotations per minute. Steam devils are very rare. They most often form from smoke issuing from a power plant's smokestack. Hot springs and deserts may also be suitable locations for a tighter, faster-rotating steam devil to form. The phenomenon can occur over water, when cold arctic air passes over relatively warm water. The Fujita scale , Enhanced Fujita scale (EF), and International Fujita scale rate tornadoes by damage caused. The EF scale
1276-514: A layer in which temperatures rise with increasing altitude. This rise in temperature is caused by the absorption of ultraviolet radiation (UV) from the Sun by the ozone layer, which restricts turbulence and mixing. Although the temperature may be −60 °C (−76 °F; 210 K) at the tropopause, the top of the stratosphere is much warmer, and may be near 0 °C. The stratospheric temperature profile creates very stable atmospheric conditions, so
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#17327725731601392-433: A major factor in the appearance of a tornado. A tornado which is " back-lit " (viewed with the sun behind it) appears very dark. The same tornado, viewed with the sun at the observer's back, may appear gray or brilliant white. Tornadoes which occur near the time of sunset can be many different colors, appearing in hues of yellow, orange, and pink. Dust kicked up by the winds of the parent thunderstorm, heavy rain and hail, and
1508-574: A mass of about 5.15 × 10 kg, three quarters of which is within about 11 km (6.8 mi; 36,000 ft) of the surface. The atmosphere becomes thinner with increasing altitude, with no definite boundary between the atmosphere and outer space . The Kármán line , at 100 km (62 mi) or 1.57% of Earth's radius, is often 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 (75 mi). Several layers can be distinguished in
1624-485: A million miles away, were found to be reflected light from ice crystals in the atmosphere. When light passes through Earth's atmosphere, photons interact with it through scattering . If the light does not interact with the atmosphere, it is called direct radiation and is what you see if you were to look directly at the Sun. Indirect radiation is light that has been scattered in the atmosphere. For example, on an overcast day when you cannot see your shadow, there
1740-413: A probe measured a 100- millibar (100 hPa ; 3.0 inHg ) pressure decrease. The pressure dropped gradually as the vortex approached then dropped extremely rapidly to 850 mbar (850 hPa ; 25 inHg ) in the core of the violent tornado before rising rapidly as the vortex moved away, resulting in a V-shape pressure trace. Temperature tends to decrease and moisture content to increase in
1856-737: A protective buffer between the Earth's surface and outer space , shields the surface from most meteoroids and ultraviolet solar radiation , keeps it warm and reduces diurnal temperature variation (temperature extremes between day and night ) through heat retention ( greenhouse effect ), redistributes heat and moisture among different regions via air currents , and provides the chemical and climate conditions allowing life to exist and evolve on Earth. By mole fraction (i.e., by quantity of molecules ), dry air contains 78.08% nitrogen , 20.95% oxygen , 0.93% argon , 0.04% carbon dioxide , and small amounts of other trace gases . Air also contains
1972-403: A recognizable life cycle which begins when increasing rainfall drags with it an area of quickly descending air known as the rear flank downdraft (RFD). This downdraft accelerates as it approaches the ground, and drags the supercell's rotating mesocyclone towards the ground with it. As the mesocyclone lowers below the cloud base, it begins to take in cool, moist air from the downdraft region of
2088-435: A small cloud of debris near the ground. Tornadoes may be obscured completely by rain or dust. These tornadoes are especially dangerous, as even experienced meteorologists might not see them. Small, relatively weak landspouts may be visible only as a small swirl of dust on the ground. Although the condensation funnel may not extend all the way to the ground, if associated surface winds are greater than 64 km/h (40 mph),
2204-618: A tornado impacts. A tornado may be much stronger than its damage-based rating indicates if its strongest winds occur away from suitable damage indicators, such as in an open field. Outside Tornado Alley , and North America in general, violent tornadoes are extremely rare. This is apparently mostly due to the lesser number of tornadoes overall, as research shows that tornado intensity distributions are fairly similar worldwide. A few significant tornadoes occur annually in Europe, Asia, southern Africa, and southeastern South America. The United States has
2320-706: A tornado touches the surface and returns to the baseline level when the tornado dissipates. In many cases, intense tornadoes and thunderstorms exhibit an increased and anomalous dominance of positive polarity CG discharges. Luminosity has been reported in the past and is probably due to misidentification of external light sources such as lightning, city lights, and power flashes from broken lines, as internal sources are now uncommonly reported and are not known to ever have been recorded. In addition to winds, tornadoes also exhibit changes in atmospheric variables such as temperature , moisture , and atmospheric pressure . For example, on June 24, 2003, near Manchester, South Dakota ,
2436-590: A tornado. Tornadoes normally rotate cyclonically (when viewed from above, this is counterclockwise in the northern hemisphere and clockwise in the southern ). While large-scale storms always rotate cyclonically due to the Coriolis effect , thunderstorms and tornadoes are so small that the direct influence of the Coriolis effect is negligible, as indicated by their large Rossby numbers . Supercells and tornadoes rotate cyclonically in numerical simulations even when
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#17327725731602552-445: A variable amount of water vapor , on average around 1% at sea level, and 0.4% over the entire atmosphere. Air composition, temperature and atmospheric pressure vary with altitude . Within the atmosphere, air suitable for use in photosynthesis by terrestrial plants and respiration of terrestrial animals is found only within 12 kilometres (7.5 mi) from the ground. Earth's early atmosphere consisted of accreted gases from
2668-760: A whirlwind) resembles a tornado in that it is a vertical swirling column of air. However, they form under clear skies and are no stronger than the weakest tornadoes. They form when a strong convective updraft is formed near the ground on a hot day. If there is enough low-level wind shear, the column of hot, rising air can develop a small cyclonic motion that can be seen near the ground. They are not considered tornadoes because they form during fair weather and are not associated with any clouds. However, they can, on occasion, result in major damage. Small-scale, tornado-like circulations can occur near any intense surface heat source. Those that occur near intense wildfires are called fire whirls . They are not considered tornadoes, except in
2784-467: A widely accepted theory for how most tornadoes form, live, and die, it does not explain the formation of smaller tornadoes, such as landspouts, long-lived tornadoes, or tornadoes with multiple vortices. These each have different mechanisms which influence their development—however, most tornadoes follow a pattern similar to this one. A multiple-vortex tornado is a type of tornado in which two or more columns of spinning air rotate about their own axes and at
2900-557: Is 14 °C (57 °F; 287 K) or 15 °C (59 °F; 288 K), depending on the reference. The average atmospheric pressure at sea level is defined by the International Standard Atmosphere as 101325 pascals (760.00 Torr ; 14.6959 psi ; 760.00 mmHg ). This is sometimes referred to as a unit of standard atmospheres (atm) . Total atmospheric mass is 5.1480×10 kg (1.135×10 lb), about 2.5% less than would be inferred from
3016-407: Is a tornado not associated with a mesocyclone. The name stems from their characterization as a "fair weather waterspout on land". Waterspouts and landspouts share many defining characteristics, including relative weakness, short lifespan, and a small, smooth condensation funnel that often does not reach the surface. Landspouts also create a distinctively laminar cloud of dust when they make contact with
3132-410: Is a wide range of tornado sizes. Weak tornadoes, or strong yet dissipating tornadoes, can be exceedingly narrow, sometimes only a few feet or couple meters across. One tornado was reported to have a damage path only 7 feet (2.1 m) long. On the other end of the spectrum, wedge tornadoes can have a damage path a mile (1.6 km) wide or more. A tornado that affected Hallam, Nebraska on May 22, 2004,
3248-408: Is about 1.2 kg/m (1.2 g/L, 0.0012 g/cm ). Density is not measured directly but is calculated from measurements of temperature, pressure and humidity using the equation of state for air (a form of the ideal gas law ). Atmospheric density decreases as the altitude increases. This variation can be approximately modeled using the barometric formula . More sophisticated models are used to predict
3364-414: Is about 28.946 or 28.96 g/mol. This is decreased when the air is humid. The relative concentration of gases remains constant until about 10,000 m (33,000 ft). 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 (see
3480-415: Is also commonly referred to as a "twister" or the old-fashioned colloquial term cyclone . A tornado is a violently rotating column of air, in contact with the ground, either pendant from a cumuliform cloud or underneath a cumuliform cloud, and often (but not always) visible as a funnel cloud. For a vortex to be classified as a tornado, it must be in contact with both the ground and the cloud base. The term
3596-442: Is because clouds (H 2 O) are strong absorbers and emitters of infrared radiation. This is also why it becomes colder at night at higher elevations. The greenhouse effect is directly related to this absorption and emission effect. Some gases in the atmosphere absorb and emit infrared radiation, but do not interact with sunlight in the visible spectrum. Common examples of these are CO 2 and H 2 O. The refractive index of air
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3712-1429: Is called paleoclimatology . The three major constituents of Earth's atmosphere are nitrogen , oxygen , and argon . Water vapor accounts for roughly 0.25% of the atmosphere by mass. The concentration of water vapor (a greenhouse gas) varies significantly from around 10 ppm by mole fraction in the coldest portions of the atmosphere to as much as 5% by mole fraction in hot, humid air masses, and concentrations of other atmospheric gases are typically quoted in terms of dry air (without water vapor). The remaining gases are often referred to as trace gases, among which are other greenhouse gases , principally carbon dioxide, methane, nitrous oxide, and ozone. Besides argon, other noble gases , neon , helium , krypton , and xenon are also present. Filtered air includes trace amounts of many other chemical compounds . Many substances of natural origin may be present in locally and seasonally variable small amounts as aerosols in an unfiltered air sample, including dust of mineral and organic composition, pollen and spores , sea spray , and volcanic ash . Various industrial pollutants also may be present as gases or aerosols, such as chlorine (elemental or in compounds), fluorine compounds and elemental mercury vapor. Sulfur compounds such as hydrogen sulfide and sulfur dioxide (SO 2 ) may be derived from natural sources or from industrial air pollution. Mole fraction
3828-447: Is close to, but just greater than, 1. Systematic variations in the refractive index can lead to the bending of light rays over long optical paths. One example is that, under some circumstances, observers on board ships can see other vessels just over the horizon because light is refracted in the same direction as the curvature of Earth's surface. The refractive index of air depends on temperature, giving rise to refraction effects when
3944-477: Is mainly composed of extremely low densities of hydrogen, helium and several heavier molecules including nitrogen, oxygen and carbon dioxide closer to the exobase. The atoms and molecules are so far apart that they can travel hundreds of kilometres 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
4060-434: Is no break in activity, this is considered a tornado outbreak (although the term "tornado outbreak" has various definitions). A period of several successive days with tornado outbreaks in the same general area (spawned by multiple weather systems) is a tornado outbreak sequence, occasionally called an extended tornado outbreak. Most tornadoes take on the appearance of a narrow funnel , a few hundred meters (yards) across, with
4176-445: Is no direct radiation reaching you, it has all been scattered. As another example, due to a phenomenon called Rayleigh scattering , shorter (blue) wavelengths scatter more easily than longer (red) wavelengths. This is why the sky looks blue; you are seeing scattered blue light. This is also why sunsets are red. Because the Sun is close to the horizon, the Sun's rays pass through more atmosphere than normal before reaching your eye. Much of
4292-444: Is not precisely defined; for example, there is disagreement as to whether separate touchdowns of the same funnel constitute separate tornadoes. Tornado refers to the vortex of wind, not the condensation cloud. A tornado is not necessarily visible; however, the intense low pressure caused by the high wind speeds (as described by Bernoulli's principle ) and rapid rotation (due to cyclostrophic balance ) usually cause water vapor in
4408-513: Is so tenuous that some scientists consider it to be part of interplanetary space rather than part of the atmosphere). It extends from the thermopause (also known as the "exobase") at the top of the thermosphere to a poorly defined boundary with the solar wind and interplanetary medium . The altitude of the exobase varies from about 500 kilometres (310 mi; 1,600,000 ft) to about 1,000 kilometres (620 mi) in times of higher incoming solar radiation. The upper limit varies depending on
4524-481: Is sometimes referred to as volume fraction ; these are identical for an ideal gas only. ppm: parts per million by molecular count The concentration of CO 2 has been increasing in recent decades , as has that of CH 4 . Water vapor is about 0.25% by mass over full atmosphere Water vapor varies significantly locally The average molecular weight of dry air, which can be used to calculate densities or to convert between mole fraction and mass fraction,
4640-461: Is the lowest layer of Earth's atmosphere. It extends from Earth's surface to an average height of about 12 km (7.5 mi; 39,000 ft), although this altitude varies from about 9 km (5.6 mi; 30,000 ft) at the geographic poles to 17 km (11 mi; 56,000 ft) at the Equator , with some variation due to weather. The troposphere is bounded above by the tropopause ,
4756-412: Is too low to conduct a significant amount of energy to or from the skin. This layer is completely cloudless and free of water vapor. However, non-hydrometeorological phenomena such as the aurora borealis and aurora australis are occasionally seen in the thermosphere. The International Space Station orbits in this layer, between 350 and 420 km (220 and 260 mi). It is this layer where many of
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4872-479: Is typically the warmest section of the troposphere. This promotes vertical mixing (hence, the origin of its name in the Greek word τρόπος, tropos , meaning "turn"). The troposphere contains roughly 80% of the mass of Earth's atmosphere. The troposphere is denser than all its overlying layers because a larger atmospheric weight sits on top of the troposphere and causes it to be most severely compressed. Fifty percent of
4988-582: The F-layer of the ionosphere where they encounter enough atmospheric drag to require reboosts every few months, otherwise, orbital decay will occur resulting in a return to Earth. Depending on solar activity, satellites can experience noticeable atmospheric drag at altitudes as high as 700–800 km. The division of the atmosphere into layers mostly by reference to temperature is discussed above. Temperature decreases with altitude starting at sea level, but variations in this trend begin above 11 km, where
5104-546: The La Plata Basin area, portions of Europe, Australia and New Zealand, and far eastern Asia. Air The atmosphere of Earth is composed of a layer of gas mixture that surrounds the Earth 's planetary surface (both lands and oceans ), known collectively as air , with variable quantities of suspended aerosols and particulates (which create weather features such as clouds and hazes ), all retained by Earth's gravity . The atmosphere serves as
5220-679: The Latin tonāre 'to thunder'). The metathesis of the r and o in the English spelling was influenced by the Spanish tornado (past participle of tornar 'to twist, turn,', from Latin tornō 'to turn'). The English word has been reborrowed into Spanish, referring to the same weather phenomenon. Tornadoes' opposite phenomena are the widespread, straight-line derechos ( / d ə ˈ r eɪ tʃ oʊ / , from Spanish : derecho Spanish pronunciation: [deˈɾetʃo] , 'straight'). A tornado
5336-465: The equator and are less common at high latitudes . Other tornado-like phenomena that exist in nature include the gustnado , dust devil , fire whirl , and steam devil . Tornadoes occur most frequently in North America (particularly in central and southeastern regions of the United States colloquially known as Tornado Alley ; the United States has by far the most tornadoes of any country in
5452-588: The infrared to around 1100 nm. There are also infrared and radio windows that transmit some infrared and radio waves at longer wavelengths. For example, the radio window runs from about one centimetre to about eleven-metre waves. Emission is the opposite of absorption, it is when an object emits radiation. Objects tend to emit amounts and wavelengths of radiation depending on their " black body " emission curves, therefore hotter objects tend to emit more radiation, with shorter wavelengths. Colder objects emit less radiation, with longer wavelengths. For example,
5568-433: The magnetosphere or the solar wind. Every second, the Earth loses about 3 kg of hydrogen, 50 g of helium, and much smaller amounts of other constituents. The exosphere is too far above Earth for meteorological phenomena to be possible. However, Earth's auroras —the aurora borealis (northern lights) and aurora australis (southern lights)—sometimes occur in the lower part of the exosphere, where they overlap into
5684-402: The mesopause that marks the top of this middle layer of the atmosphere. It is the coldest place on Earth and has an average temperature around −85 °C (−120 °F ; 190 K ). Just below the mesopause, the air is so cold that even the very scarce water vapor at this altitude can condense into polar-mesospheric noctilucent clouds of ice particles. These are the highest clouds in
5800-451: The solar nebula , but the atmosphere changed significantly over time, affected by many factors such as volcanism , impact events , weathering and the evolution of life (particularly the photoautotrophs ). Recently, human activity has also contributed to atmospheric changes , such as climate change (mainly through deforestation and fossil fuel -related global warming ), ozone depletion and acid deposition . The atmosphere has
5916-428: The temperature section). Because the general pattern of the temperature/altitude profile, or lapse rate , is constant and measurable by means of instrumented balloon soundings , the temperature behavior provides a useful metric to distinguish atmospheric layers. This atmospheric stratification divides the Earth's atmosphere into five main layers: The exosphere is the outermost layer of Earth's atmosphere (though it
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#17327725731606032-511: The tropopause . This layer extends from the top of the troposphere at roughly 12 km (7.5 mi; 39,000 ft) above Earth's surface to the stratopause at an altitude of about 50 to 55 km (31 to 34 mi; 164,000 to 180,000 ft). The atmospheric pressure at the top of the stratosphere is roughly 1/1000 the pressure at sea level . It contains the ozone layer , which is the part of Earth's atmosphere that contains relatively high concentrations of that gas. The stratosphere defines
6148-405: The "funnel cloud" term is strictly defined as a rotating cloud which is not associated with strong winds at the surface, and condensation funnel is a broad term for any rotating cloud below a cumuliform cloud. Tornadoes often begin as funnel clouds with no associated strong winds at the surface, and not all funnel clouds evolve into tornadoes. Most tornadoes produce strong winds at the surface while
6264-419: The Coriolis effect is neglected. Low-level mesocyclones and tornadoes owe their rotation to complex processes within the supercell and ambient environment. Approximately 1 percent of tornadoes rotate in an anticyclonic direction in the northern hemisphere. Typically, systems as weak as landspouts and gustnadoes can rotate anticyclonically, and usually only those which form on the anticyclonic shear side of
6380-573: The Kármán line, significant atmospheric effects such as auroras still occur. Meteors begin to glow in this region, though the larger ones may not burn up until they penetrate more deeply. The various layers of Earth's ionosphere , important to HF radio propagation, begin below 100 km and extend beyond 500 km. By comparison, the International Space Station and Space Shuttle typically orbit at 350–400 km, within
6496-560: The RFD also reaches the ground, fanning outward and creating a gust front that can cause severe damage a considerable distance from the tornado. Usually, the funnel cloud begins causing damage on the ground (becoming a tornado) within a few minutes of the RFD reaching the ground. Many other aspects of tornado formation (such as why some storms form tornadoes while others do not, or what precise role downdrafts, temperature, and moisture play in tornado formation) are still poorly understood. Initially,
6612-404: The RFD, now an area of cool surface winds, begins to wrap around the tornado, cutting off the inflow of warm air which previously fed the tornado. The flow inside the funnel of the tornado is downward, supplying water vapor from the cloud above. This is contrary to the upward flow inside hurricanes, supplying water vapor from the warm ocean below. Therefore, the energy of the tornado is supplied from
6728-459: The Sun is approximately 6,000 K (5,730 °C ; 10,340 °F ), its radiation peaks near 500 nm, and is visible to the human eye. Earth is approximately 290 K (17 °C; 62 °F), so its radiation peaks near 10,000 nm, and is much too long to be visible to humans. Because of its temperature, the atmosphere emits infrared radiation. For example, on clear nights Earth's surface cools down faster than on cloudy nights. This
6844-531: The UK (around 33, 0.00013/km, 0.00034/sq mi per year), although those are of lower intensity, briefer and cause minor damage. Tornadoes kill an average of 179 people per year in Bangladesh, the most in the world. Reasons for this include the region's high population density, poor construction quality, and lack of tornado safety knowledge. Other areas of the world that have frequent tornadoes include South Africa,
6960-605: The West this primarily occurs with classical compounds , formed on Latin or Ancient Greek roots, which may then be borrowed into a Romance language or Modern Greek. Latin is sufficiently widespread that Latinate terms coined in a non-Romance language (such as English or German) and then borrowed by a Romance language (such as French or Spanish) are not conspicuous, but modern coinages on Ancient Greek roots borrowed into Modern Greek are, and include terms such as τηλεγράφημα tilegráfima ('telegram'). These are very common . This process
7076-504: The air to condense into cloud droplets due to adiabatic cooling . This results in the formation of a visible funnel cloud or condensation funnel. There is some disagreement over the definition of a funnel cloud and a condensation funnel. According to the Glossary of Meteorology , a funnel cloud is any rotating cloud pendant from a cumulus or cumulonimbus, and thus most tornadoes are included under this definition. Among many meteorologists,
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#17327725731607192-420: The aptly-named thermosphere above 90 km. Because in an ideal gas of constant composition the speed of sound depends only on temperature and not on pressure or density, the speed of sound in the atmosphere with altitude takes on the form of the complicated temperature profile (see illustration to the right), and does not mirror altitudinal changes in density or pressure. The density of air at sea level
7308-421: The atmosphere also cools by emitting radiation, as discussed below. The combined absorption spectra of the gases in the atmosphere leave "windows" of low opacity , allowing the transmission of only certain bands of light. The optical window runs from around 300 nm ( ultraviolet -C) up into the range humans can see, the visible spectrum (commonly called light), at roughly 400–700 nm and continues to
7424-399: The atmosphere and may be visible to the naked eye if sunlight reflects off them about an hour or two after sunset or similarly before sunrise. They are most readily visible when the Sun is around 4 to 16 degrees below the horizon. Lightning-induced discharges known as transient luminous events (TLEs) occasionally form in the mesosphere above tropospheric thunderclouds . The mesosphere is also
7540-489: The atmosphere based on characteristics such as temperature and composition, namely the troposphere , stratosphere , mesosphere , thermosphere (formally the ionosphere ) and exosphere . The study of Earth's atmosphere and its processes is called atmospheric science (aerology), and includes multiple subfields, such as climatology and atmospheric physics . Early pioneers in the field include Léon Teisserenc de Bort and Richard Assmann . The study of historic atmosphere
7656-456: The audible sound depends on atmospheric conditions and topography. The winds of the tornado vortex and of constituent turbulent eddies , as well as airflow interaction with the surface and debris, contribute to the sounds. Funnel clouds also produce sounds. Funnel clouds and small tornadoes are reported as whistling, whining, humming, or the buzzing of innumerable bees or electricity, or more or less harmonic, whereas many tornadoes are reported as
7772-637: The average sea level pressure and Earth's area of 51007.2 megahectares, this portion being displaced by Earth's mountainous terrain. Atmospheric pressure is the total weight of the air above unit area at the point where the pressure is measured. Thus air pressure varies with location and weather . If the entire mass of the atmosphere had a uniform density equal to sea level density (about 1.2 kg per m ) from sea level upwards, it would terminate abruptly at an altitude of 8.50 km (27,900 ft). Air pressure actually decreases exponentially with altitude, dropping by half every 5.6 km (18,000 ft) or by
7888-858: The bases of cumulus congestus clouds over tropical and subtropical waters. They have relatively weak winds, smooth laminar walls, and typically travel very slowly. They occur most commonly in the Florida Keys and in the northern Adriatic Sea . In contrast, tornadic waterspouts are stronger tornadoes over water. They form over water similarly to mesocyclonic tornadoes, or are stronger tornadoes which cross over water. Since they form from severe thunderstorms and can be far more intense, faster, and longer-lived than fair weather waterspouts, they are more dangerous. In official tornado statistics, waterspouts are generally not counted unless they affect land, though some European weather agencies count waterspouts and tornadoes together. A landspout , or dust-tube tornado ,
8004-414: The blue light has been scattered out, leaving the red light in a sunset. Different molecules absorb different wavelengths of radiation. For example, O 2 and O 3 absorb almost all radiation with wavelengths shorter than 300 nanometres . Water (H 2 O) absorbs at many wavelengths above 700 nm. When a molecule absorbs a photon, it increases the energy of the molecule. This heats the atmosphere, but
8120-552: The case of the Tri-State Tornado. In fact, modern reanalysis of the path suggests that the tornado may have begun 15 miles (24 km) further west than previously thought. Tornadoes can have a wide range of colors, depending on the environment in which they form. Those that form in dry environments can be nearly invisible, marked only by swirling debris at the base of the funnel. Condensation funnels that pick up little or no debris can be gray to white. While traveling over
8236-542: The case of violent tornadoes, only a small portion of the path is of violent intensity, most of the higher intensity from subvortices . In the United States, 80% of tornadoes are EF0 and EF1 (T0 through T3) tornadoes. The rate of occurrence drops off quickly with increasing strength—less than 1% are violent tornadoes (EF4, T8 or stronger). Current records may significantly underestimate the frequency of strong (EF2-EF3) and violent (EF4-EF5) tornadoes, as damage-based intensity estimates are limited to structures and vegetation that
8352-491: The circulation is considered a tornado. A tornado with a nearly cylindrical profile and relatively low height is sometimes referred to as a "stovepipe" tornado. Large tornadoes which appear at least as wide as their cloud-to-ground height can look like large wedges stuck into the ground, and so are known as "wedge tornadoes" or "wedges". The "stovepipe" classification is also used for this type of tornado if it otherwise fits that profile. A wedge can be so wide that it appears to be
8468-415: The cloud above. As the RFD completely wraps around and chokes off the tornado's air supply, the vortex begins to weaken, becoming thin and rope-like. This is the "dissipating stage", often lasting no more than a few minutes, after which the tornado ends. During this stage, the shape of the tornado becomes highly influenced by the winds of the parent storm, and can be blown into fantastic patterns. Even though
8584-426: The darkness of night are all factors that can reduce the visibility of tornadoes. Tornadoes occurring in these conditions are especially dangerous, since only weather radar observations, or possibly the sound of an approaching tornado, serve as any warning to those in the storm's path. Most significant tornadoes form under the storm's updraft base , which is rain-free, making them visible. Also, most tornadoes occur in
8700-415: The definition. Various authorities consider it to end at about 10,000 kilometres (6,200 mi) or about 190,000 kilometres (120,000 mi)—about halfway to the moon, where the influence of Earth's gravity is about the same as radiation pressure from sunlight. The geocorona visible in the far ultraviolet (caused by neutral hydrogen) extends to at least 100,000 kilometres (62,000 mi). This layer
8816-412: The descending rear flank downdraft (RFD) in a cyclonic supercell. On rare occasions, anticyclonic tornadoes form in association with the mesoanticyclone of an anticyclonic supercell, in the same manner as the typical cyclonic tornado, or as a companion tornado either as a satellite tornado or associated with anticyclonic eddies within a supercell. Tornadoes emit widely on the acoustics spectrum and
8932-522: The efforts of storm spotters . There are several scales for rating the strength of tornadoes. The Fujita scale rates tornadoes by damage caused and has been replaced in some countries by the updated Enhanced Fujita Scale . An F0 or EF0 tornado, the weakest category, damages trees, but not substantial structures. An F5 or EF5 tornado, the strongest category, rips buildings off their foundations and can deform large skyscrapers . The similar TORRO scale ranges from T0 for extremely weak tornadoes to T11 for
9048-400: The first mesocyclone and associated tornado dissipate, the storm's inflow may be concentrated into a new area closer to the center of the storm and possibly feed a new mesocyclone. If a new mesocyclone develops, the cycle may start again, producing one or more new tornadoes. Occasionally, the old (occluded) mesocyclone and the new mesocyclone produce a tornado at the same time. Although this is
9164-434: The gas molecules are so far apart that its temperature in the usual sense is not very meaningful. The air is so rarefied that an individual molecule (of oxygen , for example) travels an average of 1 kilometre (0.62 mi; 3300 ft) between collisions with other molecules. Although the thermosphere has a high proportion of molecules with high energy, it would not feel hot to a human in direct contact, because its density
9280-525: The ground for more than 100 km (62 mi). Various types of tornadoes include the multiple-vortex tornado , landspout , and waterspout . Waterspouts are characterized by a spiraling funnel-shaped wind current, connecting to a large cumulus or cumulonimbus cloud. They are generally classified as non- supercellular tornadoes that develop over bodies of water, but there is disagreement over whether to classify them as true tornadoes. These spiraling columns of air frequently develop in tropical areas close to
9396-477: The ground, due to their differing mechanics from true mesoform tornadoes. Though usually weaker than classic tornadoes, they can produce strong winds which could cause serious damage. A gustnado , or gust front tornado , is a small, vertical swirl associated with a gust front or downburst . Because they are not connected with a cloud base, there is some debate as to whether or not gustnadoes are tornadoes. They are formed when fast-moving cold, dry outflow air from
9512-589: The immediate vicinity of a tornado. Tornadoes often develop from a class of thunderstorms known as supercells. Supercells contain mesocyclones , an area of organized rotation a few kilometers/miles up in the atmosphere, usually 1.6–9.7 km (1–6 miles) across. Most intense tornadoes (EF3 to EF5 on the Enhanced Fujita Scale ) develop from supercells. In addition to tornadoes, very heavy rain, frequent lightning, strong wind gusts, and hail are common in such storms. Most tornadoes from supercells follow
9628-518: The interior of British Columbia , and western New Brunswick are also tornado-prone. Tornadoes also occur across northeastern Mexico. The United States averages about 1,200 tornadoes per year, followed by Canada, averaging 62 reported per year. NOAA's has a higher average 100 per year in Canada. The Netherlands has the highest average number of recorded tornadoes per area of any country (more than 20, or 0.00048/km, 0.0012/sq mi annually), followed by
9744-615: The larger tornado (hence the name), giving the appearance of one, large multi-vortex tornado. However, a satellite tornado is a distinct circulation, and is much smaller than the main funnel. A waterspout is defined by the National Weather Service as a tornado over water. However, researchers typically distinguish "fair weather" waterspouts from tornadic (i.e. associated with a mesocyclone) waterspouts. Fair weather waterspouts are less severe but far more common, and are similar to dust devils and landspouts . They form at
9860-401: The late afternoon, when the bright sun can penetrate even the thickest clouds. There is mounting evidence, including Doppler on Wheels mobile radar images and eyewitness accounts, that most tornadoes have a clear, calm center with extremely low pressure, akin to the eye of tropical cyclones . Lightning is said to be the source of illumination for those who claim to have seen the interior of
9976-403: The layer where most meteors burn up upon atmospheric entrance. It is too high above Earth to be accessible to jet-powered aircraft and balloons, and too low to permit orbital spacecraft. The mesosphere is mainly accessed by sounding rockets and rocket-powered aircraft . The stratosphere is the second-lowest layer of Earth's atmosphere. It lies above the troposphere and is separated from it by
10092-713: The long-distance propagation of low-frequency sound, efforts are ongoing to develop tornado prediction and detection devices with additional value in understanding tornado morphology, dynamics, and creation. Tornadoes also produce a detectable seismic signature, and research continues on isolating it and understanding the process. Tornadoes emit on the electromagnetic spectrum , with sferics and E-field effects detected. There are observed correlations between tornadoes and patterns of lightning. Tornadic storms do not contain more lightning than other storms and some tornadic cells never produce lightning at all. More often than not, overall cloud-to-ground (CG) lightning activity decreases as
10208-482: The mass of Earth's atmosphere is distributed approximately as follows: By comparison, the summit of Mount Everest is at 8,848 m (29,029 ft); commercial airliners typically cruise between 10 and 13 km (33,000 and 43,000 ft) where the lower density and temperature of the air improve fuel economy; weather balloons reach 30.4 km (100,000 ft) and above; and the highest X-15 flight in 1963 reached 108.0 km (354,300 ft). Even above
10324-539: The most powerful known tornadoes. The International Fujita scale is also used to rate the intensity of tornadoes and other wind events based on the severity of the damage they cause. Doppler radar data, photogrammetry , and ground swirl patterns ( trochoidal marks) may also be analyzed to determine intensity and assign a rating. The word tornado comes from the Spanish tronada (meaning 'thunderstorm', past participle of tronar 'to thunder', itself in turn from
10440-404: The most tornadoes of any country, nearly four times more than estimated in all of Europe, excluding waterspouts. This is mostly due to the unique geography of the continent. North America is a large continent that extends from the tropics north into arctic areas, and has no major east–west mountain range to block air flow between these two areas. In the middle latitudes , where most tornadoes of
10556-514: The orbital decay of satellites. The average mass of the atmosphere is about 5 quadrillion (5 × 10 ) tonnes or 1/1,200,000 the mass of Earth. According to the American National Center for Atmospheric Research , "The total mean mass of the atmosphere is 5.1480 × 10 kg with an annual range due to water vapor of 1.2 or 1.5 × 10 kg, depending on whether surface pressure or water vapor data are used; somewhat smaller than
10672-413: The originating language. The single move from one language to the other is called "loan" (see loanword ). Reborrowing is the result of more than one loan, when the final recipient language is the same as the originating one. A similar process occurs when a word is coined in a language based on roots from another language, and then the compound is borrowed into this other language or a modern descendant. In
10788-526: The previous estimate. The mean mass of water vapor is estimated as 1.27 × 10 kg and the dry air mass as 5.1352 ±0.0003 × 10 kg." Solar radiation (or sunlight) is the energy Earth receives from the Sun . Earth also emits radiation back into space, but at longer wavelengths that humans cannot see. Part of the incoming and emitted radiation is absorbed or reflected by the atmosphere. In May 2017, glints of light, seen as twinkling from an orbiting satellite
10904-405: The rare case where they connect to a pyrocumulus or other cumuliform cloud above. Fire whirls usually are not as strong as tornadoes associated with thunderstorms. They can, however, produce significant damage. A steam devil is a rotating updraft between 50-and-200-metre wide (160 and 660 ft) that involves steam or smoke. These formations do not involve high wind speeds, only completing
11020-501: The record-holding tornado for path length—the Tri-State Tornado , which affected parts of Missouri , Illinois , and Indiana on March 18, 1925—was on the ground continuously for 219 miles (352 km). Many tornadoes which appear to have path lengths of 100 miles (160 km) or longer are composed of a family of tornadoes which have formed in quick succession; however, there is no substantial evidence that this occurred in
11136-466: The same time revolve around a common center. A multi-vortex structure can occur in almost any circulation, but is very often observed in intense tornadoes. These vortices often create small areas of heavier damage along the main tornado path. This is a phenomenon that is distinct from a satellite tornado , which is a smaller tornado that forms very near a large, strong tornado contained within the same mesocyclone. The satellite tornado may appear to " orbit "
11252-422: The satellites orbiting the Earth are present. The mesosphere is the third highest layer of Earth's atmosphere, occupying the region above the stratosphere and below the thermosphere. It extends from the stratopause at an altitude of about 50 km (31 mi; 160,000 ft) to the mesopause at 80–85 km (50–53 mi; 260,000–280,000 ft) above sea level. Temperatures drop with increasing altitude to
11368-460: The sense of "digger, foot soldier, pedestrian", then acquired the sense of "early colonist, innovator" in English, which was reborrowed into French. In other cases the term may be calqued (loan translated) at some stage, such as English ready-to-wear → French prêt-à-porter (1951) → English prêt-à-porter (1957). In some cases the borrowing process can be more complicated and the words might move through different languages before coming back to
11484-417: The sounds are caused by multiple mechanisms. Various sounds of tornadoes have been reported, mostly related to familiar sounds for the witness and generally some variation of a whooshing roar. Popularly reported sounds include a freight train, rushing rapids or waterfall, a nearby jet engine, or combinations of these. Many tornadoes are not audible from much distance; the nature of and the propagation distance of
11600-467: The southerly flow to its east. This unique topography allows for frequent collisions of warm and cold air, the conditions that breed strong, long-lived storms throughout the year. A large portion of these tornadoes form in an area of the central United States known as Tornado Alley . This area extends into Canada, particularly Ontario and the Prairie Provinces , although southeast Quebec ,
11716-409: The storm. The convergence of warm air in the updraft and cool air causes a rotating wall cloud to form. The RFD also focuses the mesocyclone's base, causing it to draw air from a smaller and smaller area on the ground. As the updraft intensifies, it creates an area of low pressure at the surface. This pulls the focused mesocyclone down, in the form of a visible condensation funnel. As the funnel descends,
11832-447: The stratosphere lacks the weather-producing air turbulence that is so prevalent in the troposphere. Consequently, the stratosphere is almost completely free of clouds and other forms of weather. However, polar stratospheric or nacreous clouds are occasionally seen in the lower part of this layer of the atmosphere where the air is coldest. The stratosphere is the highest layer that can be accessed by jet-powered aircraft . The troposphere
11948-837: The surface of the Earth, winds blow counterclockwise in the Northern Hemisphere and clockwise in the Southern. Tornadoes come in many shapes and sizes, and they are often (but not always) visible in the form of a condensation funnel originating from the base of a cumulonimbus cloud, with a cloud of rotating debris and dust beneath it. Most tornadoes have wind speeds less than 180 kilometers per hour (110 miles per hour), are about 80 meters (250 feet) across, and travel several kilometers (a few miles) before dissipating. The most extreme tornadoes can attain wind speeds of more than 480 kilometers per hour (300 mph), can be more than 3 kilometers (2 mi) in diameter, and can stay on
12064-417: The temperature gradient is large. An example of such effects is the mirage . Reborrowed The result is generally a doublet , where the reborrowed word exists alongside the original word, though in other cases the original word may have died out. Alternatively, a specific sense of a borrowed word can be reborrowed as a semantic loan ; for example, English pioneer was borrowed from Middle French in
12180-444: The temperature stabilizes over a large vertical distance through the rest of the troposphere. In the stratosphere , starting above about 20 km, the temperature increases with height, due to heating within the ozone layer caused by the capture of significant ultraviolet radiation from the Sun by the dioxygen and ozone gas in this region. Still another region of increasing temperature with altitude occurs at very high altitudes, in
12296-442: The thermopause varies considerably due to changes in solar activity. Because the thermopause lies at the lower boundary of the exosphere, it is also referred to as the exobase . The lower part of the thermosphere, from 80 to 550 kilometres (50 to 342 mi) above Earth's surface, contains the ionosphere . The temperature of the thermosphere gradually increases with height and can rise as high as 1500 °C (2700 °F), though
12412-429: The thermosphere. The exosphere contains many of the artificial satellites that orbit Earth. The thermosphere is the second-highest layer of Earth's atmosphere. It extends from the mesopause (which separates it from the mesosphere) at an altitude of about 80 km (50 mi; 260,000 ft) up to the thermopause at an altitude range of 500–1000 km (310–620 mi; 1,600,000–3,300,000 ft). The height of
12528-420: The tornado has a good source of warm, moist air flowing inward to power it, and it grows until it reaches the "mature stage". This can last from a few minutes to more than an hour, and during that time a tornado often causes the most damage, and in rare cases can be more than 1.6 km (1 mile) across. The low pressured atmosphere at the base of the tornado is essential to the endurance of the system. Meanwhile,
12644-426: The tornado is dissipating, it is still capable of causing damage. The storm is contracting into a rope-like tube and, due to conservation of angular momentum , winds can increase at this point. As the tornado enters the dissipating stage, its associated mesocyclone often weakens as well, as the rear flank downdraft cuts off the inflow powering it. Sometimes, in intense supercells, tornadoes can develop cyclically . As
12760-419: The total mass of the atmosphere is located in the lower 5.6 km (3.5 mi; 18,000 ft) of the troposphere. Nearly all atmospheric water vapor or moisture is found in the troposphere, so it is the layer where most of Earth's weather takes place. It has basically all the weather-associated cloud genus types generated by active wind circulation, although very tall cumulonimbus thunder clouds can penetrate
12876-430: The tropopause from below and rise into the lower part of the stratosphere. Most conventional aviation activity takes place in the troposphere, and it is the only layer accessible by propeller-driven aircraft . Within the five principal layers above, which are largely determined by temperature, several secondary layers may be distinguished by other properties: The average temperature of the atmosphere at Earth's surface
12992-432: The visible funnel is still above the ground, so it is difficult to discern the difference between a funnel cloud and a tornado from a distance. Occasionally, a single storm will produce more than one tornado, either simultaneously or in succession. Multiple tornadoes produced by the same storm cell are referred to as a "tornado family". Several tornadoes are sometimes spawned from the same large-scale storm system. If there
13108-596: The world occur, the Rocky Mountains block moisture and buckle the atmospheric flow , forcing drier air at mid-levels of the troposphere due to downsloped winds, and causing the formation of a low pressure area downwind to the east of the mountains. Increased westerly flow off the Rockies force the formation of a dry line when the flow aloft is strong, while the Gulf of Mexico fuels abundant low-level moisture in
13224-637: The world). Tornadoes also occur in South Africa , much of Europe (except most of the Alps), western and eastern Australia, New Zealand, Bangladesh and adjacent eastern India, Japan, the Philippines, and southeastern South America (Uruguay and Argentina). Tornadoes can be detected before or as they occur through the use of pulse-Doppler radar by recognizing patterns in velocity and reflectivity data, such as hook echoes or debris balls , as well as through
13340-584: Was an update to the older Fujita scale, by expert elicitation , using engineered wind estimates and better damage descriptions. The EF scale was designed so that a tornado rated on the Fujita scale would receive the same numerical rating, and was implemented starting in the United States in 2007. An EF0 tornado will probably damage trees but not substantial structures, whereas an EF5 tornado can rip buildings off their foundations leaving them bare and even deform large skyscrapers . The similar TORRO scale ranges from
13456-491: Was up to 2.5 miles (4.0 km) wide at the ground, and a tornado in El Reno, Oklahoma on May 31, 2013, was approximately 2.6 miles (4.2 km) wide, the widest on record. In the United States, the average tornado travels on the ground for 5 miles (8.0 km). However, tornadoes are capable of both much shorter and much longer damage paths: one tornado was reported to have a damage path only 7 feet (2.1 m) long, while
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