Jet streams are fast flowing, narrow, meandering air currents in the atmospheres of some planets, including Earth. On Earth, the main jet streams are located near the altitude of the tropopause and are westerly winds (flowing west to east). Their paths typically have a meandering shape. Jet streams may start, stop, split into two or more parts, combine into one stream, or flow in various directions including opposite to the direction of the remainder of the jet. The strongest jet streams are the polar jets, at above sea level, and the higher altitude and somewhat weaker subtropical jets at .
Introduction
Jet stream
Jet stream | Introduction
On Earth, the main jet streams are located near the altitude of the tropopause and are westerly winds Located near the altitude of the tropopause and are westerly winds They are located near the altitude of the tropopause and are westerly winds (flowing west to east). Near the altitude of the tropopause and are westerly winds
where do jet streams occur in the atmosphere
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Jet streams are fast flowing, narrow, meandering air currents in the atmospheres of some planets, including Earth. On Earth, the main jet streams are located near the altitude of the tropopause and are westerly winds (flowing west to east). Their paths typically have a meandering shape. Jet streams may start, stop, split into two or more parts, combine into one stream, or flow in various directions including opposite to the direction of the remainder of the jet. The strongest jet streams are the polar jets, at above sea level, and the higher altitude and somewhat weaker subtropical jets at .
Jet stream | Introduction
Polar jet streams are typically located near the 250 hPa (about 1/4 atmosphere) pressure level, or above sea level, while the weaker subtropical jet streams are much higher, between . Jet streams wander laterally dramatically, and have large changes in their altitude. The jet streams form near breaks in the tropopause, at the transitions between the Polar, Ferrel and Hadley circulation cells, and whose circulation, with the Coriolis force acting on those masses, drives the jet streams. The Polar jets, at lower altitude, and often intruding into mid-latitudes, strongly affect weather and aviation. The polar jet stream is most commonly found between latitudes 30° and 60° (closer to 60°), while the subtropical jet streams are located close to latitude 30°.
Jet stream | Description
There are wind maxima at lower levels of the atmosphere that are also referred to as jets.
Jet stream | Low-level jets
The Northern Hemisphere and the Southern Hemisphere each have a polar jet and a subtropical jet. The northern hemisphere polar jet flows over the middle to northern latitudes of North America, Europe, and Asia and their intervening oceans, while the southern hemisphere polar jet mostly circles Antarctica all year round. The southern hemisphere mid-latitude jet is a relatively narrow band of strong winds stretching from the Earth's surface to the top of the troposphere at about 12 km increasing steadily in strength with height. Jet streams are the product of two factors: the atmospheric heating by solar radiation that produces the large-scale Polar, Ferrel, and Hadley circulation cells, and the action of the Coriolis force acting on those moving masses.
Jet stream | Introduction
Jupiter's atmosphere has multiple jet streams, caused by the convection cells that form the familiar banded color structure; on Jupiter, these convection cells are driven by internal heating. The factors that control the number of jet streams in a planetary atmosphere is an active area of research in dynamical meteorology. In models, as one increases the planetary radius, holding all other parameters fixed, the number of jet streams decreases.
Jet stream | Other planets
Associated with jet streams is a phenomenon known as clear-air turbulence (CAT), caused by vertical and horizontal wind shear caused by jet streams. The CAT is strongest on the cold air side of the jet, next to and just under the axis of the jet. Clear-air turbulence can cause aircraft to plunge and so present a passenger safety hazard that has caused fatal accidents, such as the death of one passenger on United Airlines Flight 826.
Jet stream | Aviation
These two jets merge at some locations and times, while at other times they are well separated. The northern Polar jet stream is said to "follow the sun" as it slowly migrates northward as that hemisphere warms, and southward again as it cools. The width of a jet stream is typically a few hundred kilometres or miles and its vertical thickness often less than . Jet streams are typically continuous over long distances, but discontinuities are common. The path of the jet typically has a meandering shape, and these meanders themselves propagate eastward, at lower speeds than that of the actual wind within the flow.
Jet stream | Description
Therefore, the strong eastward moving jet streams are in part a simple consequence of the fact that the Equator is warmer than the North and South poles.
Jet stream | Cause
Since 2007, and particularly in 2012 and early 2013, the jet stream has been at an abnormally low latitude across the UK, lying closer to the English Channel, around 50°N rather than its more usual north of Scotland latitude of around 60°N. However, between 1979 and 2001, the average position of the jet stream moved northward at a rate of per year across the Northern Hemisphere. Across North America, this type of change could lead to drier conditions across the southern tier of the United States and more frequent and more intense tropical cyclones in the tropics. A similar slow poleward drift was found when studying the Southern Hemisphere jet stream over the same time frame.
Jet stream | Longer-term climatic changes
After the 1883 eruption of the Krakatoa volcano, weather watchers tracked and mapped the effects on the sky over several years. They labelled the phenomenon the "equatorial smoke stream". In the 1920s, a Japanese meteorologist, Wasaburo Oishi, detected the jet stream from a site near Mount Fuji. He tracked pilot balloons, also known as pibals (balloons used to determine upper level winds), as they rose into the atmosphere. Oishi's work largely went unnoticed outside Japan because it was published in Esperanto. American pilot Wiley Post, the first man to fly around the world solo in 1933, is often given some credit for discovery of jet streams.
Jet stream | Discovery
A second factor which contributes to a concentrated jet is more applicable to the subtropical jet which forms at the poleward limit of the tropical Hadley cell, and to first order this circulation is symmetric with respect to longitude. Tropical air rises to the tropopause, and moves poleward before sinking; this is the Hadley cell circulation. As it does so it tends to conserve angular momentum, since friction with the ground is slight. Air masses that begin moving poleward are deflected eastward by the Coriolis force (true for either hemisphere), which for poleward moving air implies an increased westerly component of the winds (note that deflection is leftward in the southern hemisphere).
Jet stream | Subtropical jet
Post invented a pressurized suit that let him fly above . In the year before his death, Post made several attempts at a high-altitude transcontinental flight, and noticed that at times his ground speed greatly exceeded his air speed. German meteorologist Heinrich Seilkopf is credited with coining a special term, "Strahlströmung" (literally "jet current"), for the phenomenon in 1939. Many sources credit real understanding of the nature of jet streams to regular and repeated flight-path traversals during World War II. Flyers consistently noticed westerly tailwinds in excess of in flights, for example, from the US to the UK. Similarly in 1944 a team of American meteorologists in Guam, including Reid Bryson, had enough observations to forecast very high west winds that would slow bombers going to Japan.
Jet stream | Discovery
The jet stream is a fast-moving high-altitude wind phenomenon. A jetstream is a machine that creates a waterstream in a swimming pool, which can be used for exercise, entertainment or massage Jet stream or Jetstream may refer to:
Jet stream (disambiguation) | Introduction
The mid-level African easterly jet occurs during the Northern Hemisphere summer between 10°N and 20°N above West Africa, and the nocturnal poleward low-level jet occurs in the Great Plains of east and South Africa. The low-level easterly African jet stream is considered to play a crucial role in the southwest monsoon of Africa, and helps form the tropical waves which move across the tropical Atlantic and eastern Pacific oceans during the warm season. The formation of the thermal low over northern Africa leads to a low-level westerly jet stream from June into October.
Jet stream | Africa
The subtropical jet stream across the deep tropics of the Northern Hemisphere is enhanced due to increased convection in the equatorial Pacific, which decreases tropical cyclogenesis within the Atlantic tropics below what is normal, and increases tropical cyclone activity across the eastern Pacific. In the Southern Hemisphere, the subtropical jet stream is displaced equatorward, or north, of its normal position, which diverts frontal systems and thunderstorm complexes from reaching central portions of the continent.
Jet stream | El Niño
If two air masses, one cold and dense to the North and the other hot and less dense to the South, are separated by a vertical boundary and that boundary should be removed, the difference in densities will result in the cold air mass slipping under the hotter and less dense air mass. The Coriolis effect will then cause poleward-moving mass to deviate to the East, while equatorward-moving mass will deviate toward the west. The general trend in the atmosphere is for temperatures to decrease in the poleward direction. As a result, winds develop an eastward component and that component grows with altitude.
Jet stream | Cause
The Coriolis force is caused by the planet's rotation on its axis. On other planets, internal heat rather than solar heating drives their jet streams. The Polar jet stream forms near the interface of the Polar and Ferrel circulation cells; the subtropical jet forms near the boundary of the Ferrel and Hadley circulation cells.
Jet stream | Introduction
A valley exit jet is a strong, down-valley, elevated air current that emerges above the intersection of the valley and its adjacent plain. These winds frequently reach a maximum of at a height of above the ground. Surface winds below the jet may sway vegetation, but are significantly weaker. They are likely to be found in valley regions that exhibit diurnal mountain wind systems, such as those of the dry mountain ranges of the US. Deep valleys that terminate abruptly at a plain are more impacted by these factors than are those that gradually become shallower as downvalley distance increases.
Jet stream | Valley exit jet
The warmer air can only move along the edge of the polar vortex, but not enter it. Within the vortex, the cold polar air becomes increasingly cold with neither warmer air from lower latitudes nor energy from the Sun entering during the polar night.
Jet stream | Polar night jet
Inflow can originate from mid-levels of the atmosphere too. When thunderstorms are able to organize into squall lines, a feature known as a rear inflow jet develops to the south of the mid-level circulation associated with its northern bookend vortex. This leads to an erosion of rain within the broad rain shield behind the squall line, and may lead to acceleration of the squall line itself.
Inflow (meteorology) | Thunderstorms
Evidence suggests the jet stream was at least partly responsible for the widespread drought conditions during the 1930s Dust Bowl in the Midwest United States. Normally, the jet stream flows east over the Gulf of Mexico and turns northward pulling up moisture and dumping rain onto the Great Plains. During the Dust Bowl, the jet stream weakened and changed course traveling farther south than normal. This starved the Great Plains and other areas of the Midwest of rainfall, causing extraordinary drought conditions.
Jet stream | Dust Bowl
A horizontal temperature gradient exists while moving North-South along a meridian because curvature of the Earth allows for more solar heating at the equator than at the poles. This creates a westerly geostrophic wind pattern to form in the mid-latitudes. Because thermal wind causes an increase in wind velocity with height, the westerly pattern increases in intensity up until the tropopause, creating a strong wind current known as the jet stream. The Northern and Southern Hemispheres exhibit similar jet stream patterns in the mid-latitudes. The strongest part of jet streams should be in proximity where temperature gradients are the largest.
Thermal wind | Jet stream
On Earth, the northern polar jet stream is the most important one for aviation and weather forecasting, as it is much stronger and at a much lower altitude than the subtropical jet streams and also covers many countries in the Northern Hemisphere, while the southern polar jet stream mostly circles Antarctica and sometimes the southern tip of South America. The term "jet stream" in these contexts thus usually implies the northern polar jet stream.
Jet stream | Uses
According to a report in New Scientist many researchers are in consensus that Rossby waves are acting against the jet stream's usual pattern and holding it in place. Upper atmospheric studies using National Oceanic and Atmospheric Administration (NOAA) data indicates that during July 2010 these upper air stream patterns were most frequently observed in the Northern Hemisphere. Examination of the climatology data over the same period of time indicates that these wild planetary wave meanderings are not a normal aspect of our regional climate patterns. Meanwhile, ongoing research studies at the University of Reading show that unusual patterns in the polar jet stream are more common during a period of low activity in the solar cycle when the observed sun spot activity and their associated solar flares are at their minimum.
Upper-atmospheric models | Planetary waves
The discovery of "Easterly Jet Stream" is one of the principal contributions of Koteswaram to metereology. He explained the phenomenon in the mid-fifties, defining it as an air current which reaches the speed of about 40m/sec during June–September periods and located near 14N with axis lying between 200-100mb (12-13 km). The discovery earned him an invitation from Herbert Riehl, the German-born US meteorologist, for joint research at the University of Chicago from 1955 to 1956 which returned new findings on the phenomenon. The duo found out that the jet stream was caused by the high levels of heat over Tibetan region and their findings assisted another German meteorologist, Hermann Flohn, in his work, besides providing a tool for predicting the Indian summer monsoon.
Pancheti Koteswaram | Scientific achievements
A jet stream perturbation model is employed by Weather Logistics UK, which simulates the diversion of the air streams in the upper atmosphere. North Atlantic air flow modelling is simulated by combining a monthly jet stream climatology input calculated at 20 to 30°W, with different blocking high patterns. The jet stream input is generated by thermal wind balance calculations at 316mbars (6 to 9 km aloft) in the mid-latitude range from 40 to 60°N. Long term blocking patterns are determined by the weather forecaster, who identifies the likely position and strength of North Atlantic Highs from synoptic charts, the North Atlantic Oscillation (NAO) and El Niño-Southern Oscillation (ENSO) patterns.
Upper-atmospheric models | Jet stream perturbation model
A barrier jet in the low levels forms just upstream of mountain chains, with the mountains forcing the jet to be oriented parallel to the mountains. The mountain barrier increases the strength of the low level wind by 45 percent. In the North American Great Plains a southerly low-level jet helps fuel overnight thunderstorm activity during the warm season, normally in the form of mesoscale convective systems which form during the overnight hours. A similar phenomenon develops across Australia, which pulls moisture poleward from the Coral Sea towards cut-off lows which form mainly across southwestern portions of the continent.
Jet stream | Barrier jet
The Equatorial jet stream is unusual in that it sometimes flows from east to west at about 10° N, approximately the same latitude as Kerala (8° N) and Mayon Volcano (13° N). This hypothesis was also ruled out as the particles were neither acidic nor of volcanic origin, but were spores.
Red rain in Kerala | Alternative hypotheses
In general, winds are strongest immediately under the tropopause (except locally, during tornadoes, tropical cyclones or other anomalous situations). If two air masses of different temperatures or densities meet, the resulting pressure difference caused by the density difference (which ultimately causes wind) is highest within the transition zone. The wind does not flow directly from the hot to the cold area, but is deflected by the Coriolis effect and flows along the boundary of the two air masses. All these facts are consequences of the thermal wind relation. The balance of forces acting on an atmospheric air parcel in the vertical direction is primarily between the gravitational force acting on the mass of the parcel and the buoyancy force, or the difference in pressure between the top and bottom surfaces of the parcel.
Jet stream | Cause
The sinking of the jet first starts when the mid level inflow goes under the trailing stratiform cloud before descending to the melting layer.
Rear-inflow jet | Introduction
The thermal wind relation does not explain why the winds are organized into tight jets, rather than distributed more broadly over the hemisphere. One factor that contributes to the creation of a concentrated polar jet is the undercutting of sub-tropical air masses by the more dense polar air masses at the polar front. This causes surface low pressure and higher pressure at altitude. At high altitudes, lack of friction allows air to respond freely to the steep pressure gradient with low pressure at high altitude over the pole. This results in the formation of planetary wind circulations that experience a strong Coriolis deflection and thus can be considered 'quasi-geostrophic'.
Jet stream | Polar jet stream
On September 14, 2001, scientists at the Arecibo Observatory photographed a gigantic jet—double the height of those previously observed—reaching around into the atmosphere. The jet was located above a thunderstorm over an ocean, and lasted under a second. The jet was initially observed to be traveling up at around at a speed similar to typical lightning, increased to , but then split in two and sped upward with speeds of at least to the ionosphere where it then spread out in a bright burst of light. On July 22, 2002, five gigantic jets between in length were observed over the South China Sea from Taiwan, reported in "Nature".
Upper-atmospheric lightning | Observations
The polar front jet stream is closely linked to the frontogenesis process in midlatitudes, as the acceleration/deceleration of the air flow induces areas of low/high pressure respectively, which link to the formation of cyclones and anticyclones along the polar front in a relatively narrow region.
Jet stream | Polar jet stream
When the jet stream lies north of the British Isles then continental high pressure is able to move in; when it lies across or south of the British Isles, Arctic air and Atlantic weather systems predominate.
Weather lore | July
Each large meander, or wave, within the jet stream is known as a Rossby wave (planetary wave). Rossby waves are caused by changes in the Coriolis effect with latitude. Shortwave troughs, are smaller scale waves superimposed on the Rossby waves, with a scale of long, that move along through the flow pattern around large scale, or longwave, "ridges" and "troughs" within Rossby waves. Jet streams can split into two when they encounter an upper-level low, that diverts a portion of the jet stream under its base, while the remainder of the jet moves by to its north.
Jet stream | Description
Where blue jets are believed to initiate between the upper positive charge region and a negative screening layer directly above this region, gigantic jets appear to initiate between the upper positive and lower negative charge regions in the thundercloud. In a similar process to how blue jets form, the higher charge region is discharged by the leader network before the same occurs in the lower charge region, and one end of the leader network propagates upward from the cloud toward the ionosphere. Gigantic jets reach higher altitudes than blue jets, and the upper portion of the jet changes color from blue to red.
Upper-atmospheric lightning | Gigantic jets
In June 1931 he was a.o. Professor at the Technical University of Hannover, since 1940 also lecturer at the University of Hamburg for "Seeflugmeteorologie". In 1939 he had discovered the jet stream. In 1941 he was Director at the German Weather Service Seewetteramt in Hamburg-Nienstetten.
Heinrich Seilkopf | Introduction
But with continuous dropping pressure, sufficient force is created for the movement of the westerly jet across the Himalayas after a significant period. As such, the shift of the jet is sudden and abrupt, causing the bursting of southwest monsoon rains onto the Indian plains. The reverse shift happens for the northeast monsoon.
Monsoon of South Asia | Jet stream theory
The Jet Standard Atmosphere is a reference atmospheric model often used by jet manufacturers. It is a derivation and extension of the International Standard Atmosphere (ISA). It assumes a mean sea-level temperature of +. The temperature then lapses 2 °C per to infinity. There is no tropopause in the jet standard atmosphere. In the ISA, the tropopause is the height at which the temperature stops decreasing, and is also the end of the troposphere and the start of the stratosphere.
Jet standard atmosphere | Introduction
Across North America during La Niña, increased precipitation is diverted into the Pacific Northwest due to a more northerly storm track and jet stream. The storm track shifts far enough northward to bring wetter than normal conditions (in the form of increased snowfall) to the Midwestern states, as well as hot and dry summers. Snowfall is above normal across the Pacific Northwest and western Great Lakes. Across the North Atlantic, the jet stream is stronger than normal, which directs stronger systems with increased precipitation towards Europe.
Jet stream | La Niña
On the right image, the effect occurs along the curved wall as a "wall jet". The image here on the right represents a "two dimensional wall jet" between two parallel plane walls, where the "obstacle" is a quarter cylindrical portion following the flat horizontal rectangular orifice, so that no fluid at all is entrained from the surroundings along the wall, but only on the opposite side in turbulent mixing with ambient air.
Coandă effect | Conditions of existence
On 28 April 2017, a fragment of is suspected of having impacted Earth creating a fireball over Kyoto, Japan. The fragment would have broken off the parent body within the last ten thousand years.
(164121) 2003 YT1 | Meteor stream
The rear-inflow jet is a component of bow echoes in a mesoscale convective system that aids in creating a stronger cold pool and downdraft. The jet forms as a response to a convective circulation having upshear tilt and horizontal pressure gradients. The cold pool that comes from the outflow of a storm forms an area of high pressure at the surface. In response to the surface high and warmer temperatures aloft due to convection, a mid-level mesolow forms behind the leading edge of the storm. With a mid-level area of low pressure, air is drawn in under the trailing stratiform region of precipitation.
Rear-inflow jet | Introduction
Despite the fact that the three genera of high clouds, "Cirrus", "Cirrocumulus" and "Cirrostratus", form at the top of the troposphere, far from the earth surface, they may have an anthropogenic origin. In this case, the process that causes their formation is almost always the same: commercial and military aircraft flight. Exhaust products from the combustion of the kerosene expelled by engines provide water vapor to this region of the troposphere. In addition, the strong contrast between the cold air of the high troposphere layers and the warm and moist air ejected by aircraft engines causes rapid sublimation of water vapor forming small ice crystals.
Anthropogenic cloud | High homogenitus
a more zonally symmetric jet).
Thermal wind | Jet stream
Due to land masses in the northern hemisphere, largest temperature contrasts are observed on the east coast of North America (boundary between Canadian cold air mass and the Gulf Stream/warmer Atlantic) and Eurasia (boundary between the boreal winter monsoon/Siberian cold air mass and the warm Pacific). Therefore, the strongest boreal winter jet streams are observed over east coast of North America and Eurasia. Since stronger vertical shear promotes baroclinic instability, the most rapid development of extratropical cyclones (so called bombs) is also observed along the east coast of North America and Eurasia. The lack of land masses in the Southern Hemisphere leads to a more constant jet with longitude (i.e.
Thermal wind | Jet stream
The location of the jet stream is extremely important for aviation. Commercial use of the jet stream began on 18 November 1952, when Pan Am flew from Tokyo to Honolulu at an altitude of . It cut the trip time by over one-third, from 18 to 11.5 hours. Not only does it cut time off the flight, it also nets fuel savings for the airline industry. Within North America, the time needed to fly east across the continent can be decreased by about 30 minutes if an airplane can fly with the jet stream, or increased by more than that amount if it must fly west against it.
Jet stream | Aviation
Climate scientists have hypothesized that the jet stream will gradually weaken as a result of global warming. Trends such as Arctic sea ice decline, reduced snow cover, evapotranspiration patterns, and other weather anomalies have caused the Arctic to heat up faster than other parts of the globe (polar amplification). This in turn reduces the temperature gradient that drives jet stream winds, which may eventually cause the jet stream to become weaker and more variable in its course. As a consequence, extreme winter weather is expected to become more frequent. With a weaker jet stream, the Polar vortex has a higher probability to leak out of the polar area and bring extremely cold weather to the middle latitude regions.
Jet stream | Longer-term climatic changes
It has basically all the weather-associated cloud genus types generated by active wind circulation, although very tall cumulonimbus thunder clouds can penetrate 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 that can be accessed by propeller-driven aircraft.
Atmosphere of Earth | Troposphere
Although the temperature may be 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 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.
Atmosphere of Earth | Stratosphere
Because the temperature in the tropopause and lower stratosphere is largely constant with increasing altitude, very little convection and its resultant turbulence occurs there. Most turbulence at this altitude is caused by variations in the jet stream and other local wind shears, although areas of significant convective activity (thunderstorms) in the troposphere below may produce turbulence as a result of convective overshoot.
Stratosphere | Aircraft flight
A trough is the result of the movements of the air in the atmosphere. In regions where there is upward movement near the ground and divergence at altitude, there is a loss of mass. The pressure becomes lower at this point. At upper levels of the atmosphere, this occurs when there is a meeting of a mass of cold air and another hot one along a thin ribbon called a frontal baroclinic zone. We then have the creation of a jet stream that plunges the cold air towards the equator and hot air towards the poles, creating a ripple in the circulation that is called a Rossby wave.
Trough (meteorology) | Formation
This process is also enhanced by the presence of abundant nuclei of condensation produced as a result of combustion. These clouds are commonly known as condensation trails (contrails) and are initially lineal "cirrus clouds" that could be called "Cirrus homogenitus" (Cia). Due to the large temperature difference between the air exhausted and the ambiance air generates small-scale convection processes. These processes favor the evolution of the condensation trails to "Cirrocumulus homogenitus" ("Cca"). Depending on the atmospheric conditions at the upper part of the troposphere, where the plane is flying, these high clouds rapidly disappear or persist. When the air is dry and stable, the water rapidly evaporates inside the contrails and can only observed up to several hundreds of meters from the plane.
Anthropogenic cloud | High homogenitus
Mountain jets are a type of jet stream created by surface winds channeled through mountain passes, sometimes causing high wind speeds and drastic temperature changes.
Mountain jet | Introduction
With very-long-baseline interferometry, the fine detail of radio waves can be seen down to milliarcsecond (mas) resolution. A central very bright single point called the "core" is observed. From the core an extremely high-speed blast of plasma emerges in a narrow cone shape as a one-sided jet. After 30 milliarcseconds, the jet, which is 300 pc long, does a 90° turn and fans out. The inner jet before the kink shows bright edges or a limb-brightened structure less than 10 mas wide. This is probably due to a fast-moving central part to the jet, combined with slower edges. Normally, there would be jets of gas shooting out in opposite directions.
Markarian 501 | Jet
On Earth, the clouds are detected as emission lines in the blazar spectrum. Perpendicular to the accretion disk, a pair of relativistic jets carries highly energetic plasma away from the AGN. The jet is collimated by a combination of intense magnetic fields and powerful winds from the accretion disk and toroid. Inside the jet, high energy photons and particles interact with each other and the strong magnetic field. These relativistic jets can extend as far as many tens of kiloparsecs from the central black hole.
Blazar | Structure
TEJ flows from east to west over peninsular India at 6 – 9 km and over the Northern African region.
Tropical Easterly Jet | Introduction
Notes Citations Bibliography
Jet Storm | References
Streamers can emerge when a strong electric field is applied to an insulating material, typically a gas. Streamers can only form in areas where the electric field exceeds the dielectric strength (breakdown field, disruptive field) of the medium. For air at atmospheric pressure, this is roughly 30 kV per centimeter. The electric field accelerates the few electrons and ions that are always present in air, due to natural processes such as cosmic rays, radioactive decay, or photoionization. Ions are much heavier, so they move very slowly compared to electrons. As the electrons move through the medium, they collide with the neutral molecules or atoms.
Streamer discharge | Streamer physics
The Tropical Easterly Jet is the meteorological term referring to an upper level easterly wind that starts in late June and continues until early September. This strong flow of air that develops in the upper atmosphere during the Asian monsoon is centred on 15°N, 50-80°E and extends from South-East Asia to Africa. The strongest development of the jet is at about 15 km above the Earth's surface with wind speeds of up to 40 m/s over the Indian Ocean. Tropical Easterly Jet (TEJ) comes into existence quickly after the Sub Tropical Jet (STJ) has shifted to the north of the Himalayas (Early June).
Tropical Easterly Jet | Introduction
The jets lasted under a second, with shapes likened by the researchers to giant trees and carrots. On November 10, 2012, the Chinese Science Bulletin reported a gigantic jet event observed over a thunderstorm in mainland China on August 12, 2010. "GJ event that was clearly recorded in eastern China (storm center located at 35.6°N,119.8°E, near the Huanghai Sea)".
Upper-atmospheric lightning | Observations
The strong temperature contrast between polar and tropical air gives rise to the jet stream. Weather systems in the mid-latitudes, such as extratropical cyclones, are caused by instabilities of the jet stream flow. Because the Earth's axis is tilted relative to its orbital plane, sunlight is incident at different angles at different times of the year. On the Earth's surface, temperatures usually range ±40 °C (100 °F to −40 °F) annually. Over thousands of years, changes in the Earth's orbit have affected the amount and distribution of solar energy received by the Earth and influence long-term climate Surface temperature differences in turn cause pressure differences.
Natural environment | Weather
This outrunning occurs within the westerlies in a pattern where the upper level jet splits into two streams. The resultant mesoscale convective system (MCS) forms at the point of the upper level split in the wind pattern in the area of best low level inflow. The convection then moves east and toward the equator into the warm sector, parallel to low-level thickness lines. When the convection is strong and linear or curved, the MCS is called a squall line, with the feature placed at the leading edge of the significant wind shift and pressure rise which is normally just ahead of its radar signature.
Outflow boundary | Origin
The polar-night jet stream forms mainly during the winter months when the nights are much longer, hence polar nights, in their respective hemispheres at around 60° latitude. The polar night jet moves at a greater height (about ) than it does during the summer. During these dark months the air high over the poles becomes much colder than the air over the Equator. This difference in temperature gives rise to extreme air pressure differences in the stratosphere, which, when combined with the Coriolis effect, create the polar night jets, that race eastward at an altitude of about . The polar vortex is circled by the polar night jet.
Jet stream | Polar night jet
The equatorial electrojet (EEJ) is a narrow ribbon of current flowing eastward in the day time equatorial region of the Earth's ionosphere. The abnormally large amplitude of variations in the horizontal components measured at equatorial geomagnetic observatories, as a result of EEJ, was noticed as early as 1920 from Huancayo geomagnetic observatory. Observations by radar, rockets, satellites, and geomagnetic observatories are used to study EEJ.
Equatorial electrojet | Introduction
The model is based on the knowledge that low pressure systems at the surface are steered by the fast ribbons (jet streams) of air in the upper atmosphere. The jet stream - blocking interaction model simulation examines the sea surface temperature field using data from NOAA tracked along the ocean on a path to the British Isles. The principal theory suggests that long term weather patterns act on longer time scales, so large blocking patterns are thought to appear in a similar locations repeatedly over several months. With a good knowledge of blocking high patterns, the model performs with an impressive accuracy that is useful to the end user.
Upper-atmospheric models | Jet stream perturbation model
Rear inflow jets behind squall lines act to erode the broad rain shield behind the squall line, and accelerate its forward motion.
Inflow (meteorology) | Introduction
Circulation in Jupiter's atmosphere is markedly different from that in the atmosphere of Earth. The interior of Jupiter is fluid and lacks any solid surface. Therefore, convection may occur throughout the planet's outer molecular envelope. As of 2008, a comprehensive theory of the dynamics of the Jovian atmosphere has not been developed. Any such theory needs to explain the following facts: the existence of narrow stable bands and jets that are symmetric relative to Jupiter's equator, the strong prograde jet observed at the equator, the difference between zones and belts, and the origin and persistence of large vortices such as the Great Red Spot.
Atmosphere of Jupiter | Dynamics
A jet stream alone will rarely be the cause of CAT, although there is horizontal wind shear at its edges and within it, caused by the different relative air speeds of the stream and the surrounding air. Rossby waves caused by this jet stream shear and the Coriolis force cause it to meander.
Clear-air turbulence | Jet stream
Convective processes of the troposphere affect the transport of water vapour-a green house gas, and its circulation in both the stratosphere and mesosphere. By analysing the processes that occur in these layers, can improve atmospheric models, and provide a better understanding of Earth's climate and weather. The experiment also studies how much water the cloud turrets can carry into the stratosphere, and how lightning influences their formation. Thor analyses red sprites, blue and gigantic jets from the Space Station over Earth at night. Sprites appear as luminous reddish-orange flashes and last 20 milliseconds at most. They often occur in clusters within atmosphere above the troposphere at an altitude range of 50–90 km (31–56 mi).
Thor experiment | Details
That is to say, the winds occur when cold high-pressure systems from the North American continent meet warm moist air over the Caribbean and Gulf of Mexico, generating winds that are then funneled through a mountain pass in the Cordillera. The Papagayo jet is also not unique to this region. There are two other breaks in the Cordillera where this same phenomenon occurs, one at the Chivela Pass in México and another at the Panama Canal, producing the Tehuano (Tehuantepecer) and the Panama jets respectively. The Papagayo jet also induces mesoscale meteorology phenomena that influence the pacific waters hundreds of kilometers off the Nicaraguan and Costa Rican shores.
Papagayo Jet | Introduction
Jet streak dynamics through the imbalance of Coriolis and pressure gradient forces, causing subgeostrophic and supergeostrophic flows, can also create upward vertical velocities. There are numerous other atmospheric setups in which upward vertical velocities can be created.
Atmospheric convection | Boundaries and forcing
In North and Central America, during the Northern Hemisphere winter, high-pressure systems are created between the equator and 35th parallels north via atmospheric circulation. Air near the equator is warmed by the sun. This heated air is more buoyant than colder air so it rises and is then pushed poleward by more air rising from below. Once the air reaches northern latitudes it begins to cool and as a result it falls back towards to the Earth's surface. As the air is falling it exerts more pressure downward on the surface, creating a high-pressure systems. This cold, high-pressure air mass then travels equatorward.
Papagayo Jet | Formation
The ultimate result of the process described above is production of large scale elongated structures, which are parallel to the equator. The meridional extent of them appears to match the actual width of jets. Therefore, in shallow models vortices actually feed the jets and should disappear by merging into them. While these weather–layer models can successfully explain the existence of a dozen narrow jets, they have serious problems. A glaring failure of the model is the prograde (super-rotating) equatorial jet: with some rare exceptions shallow models produce a strong retrograde (subrotating) jet, contrary to observations. In addition, the jets tend to be unstable and can disappear over time.
Atmosphere of Jupiter | Shallow models
The dust is believed to come from micrometeors, although particulates from volcanoes and dust from the troposphere are also possibilities. The moisture could be lifted through gaps in the tropopause, as well as forming from the reaction of methane with hydroxyl radicals in the stratosphere. The exhaust from Space Shuttles, in use between 1981 and 2011, which was almost entirely water vapour after the detachment of the Solid Rocket Booster at a height of about 46 km, was found to generate minuscule individual clouds. About half of the vapour was released into the thermosphere, usually at altitudes of . In August 2014, a SpaceX Falcon 9 also caused noctilucent clouds over Orlando, FL after a launch.
Noctilucent cloud | Formation
The jets from the primary are emitted perpendicular to its accretion disk. The jets and disk precess around an axis inclined about 79° to a line between Earth and SS 433. The angle between the jets and the axis is around 20°, and the precessional period is around 162.5 days. Precession means that the jets sometimes point more towards the Earth, and sometimes more away, producing both blue and red Doppler shifts in the observed visible spectrum. Also, the precession means that the jets corkscrew through space in an expanding helical spray. As they impact the surrounding W50 supernova remnant clouds, they distort it into an elongated shape.
SS 433 | Observational data
Streams typically derive most of their water from precipitation in the form of rain and snow. Most of this water re-enters the atmosphere by evaporation from soil and water bodies, or by the evapotranspiration of plants. Some of the water proceeds to sink into the earth by infiltration and becomes groundwater, much of which eventually enters streams. Some precipitated water is temporarily locked up in snow fields and glaciers, to be released later by evaporation or melting. The rest of the water flows off the land as runoff, the proportion of which varies according to many factors, such as wind, humidity, vegetation, rock types, and relief.
Stream | Sources
The storms moved with a speed as high as 170 m/s, slightly faster than the jet itself, hinting at the existence of strong winds deep in the atmosphere.
Atmosphere of Jupiter | Storms and lightning
The air flow is due to surges of cold dense air originating from the North American continent. The meteorological mechanism that causes Tehuano and Papagayo winds is relatively simple. In the winter, cold high-pressure weather systems move southward from North America over the Gulf of Mexico. These high pressure systems create strong pressure gradients between the atmosphere over the Gulf of Mexico and the warmer, moister atmosphere over the Pacific Ocean. Just as a river flows from high elevations to lower elevations, the air in the high pressure system will flow "downhill" toward lower pressure, but the Cordillera mountains block the flow of air, channeling it through Chivela Pass in Mexico, the lake district of Nicaragua, and also Gaillard (Culebra) Cut in Panama.
Mountain jet | Cause
The reason for this phenomenon is that fluid streamlines cannot abruptly change direction. In the case of both the free jet and the sudden pipe diameter change, the streamlines are unable to closely follow the sharp angle in the pipe/tank wall. The converging streamlines follow a smooth path, which results in the narrowing of the jet (or primary pipe flow).
Vena contracta | Explanation
El Niño-Southern Oscillation (ENSO) influences the average location of upper-level jet streams, and leads to cyclical variations in precipitation and temperature across North America, as well as affecting tropical cyclone development across the eastern Pacific and Atlantic basins. Combined with the Pacific Decadal Oscillation, ENSO can also impact cold season rainfall in Europe. Changes in ENSO also change the location of the jet stream over South America, which partially affects precipitation distribution over the continent.
Jet stream | Effects of ENSO
The jet speeds are high on Jupiter, reaching more than 100 m/s. These speeds correspond to ammonia clouds located in the pressure range 0.7–1 bar. The prograde jets are generally more powerful than the retrograde jets. The vertical extent of jets is not known. They decay over two to three scale heights above the clouds, while below the cloud level, winds increase slightly and then remain constant down to at least 22 bar—the maximum operational depth reached by the Galileo Probe.
Atmosphere of Jupiter | Zones, belts and jets
This pressure gradient can appear in a zone before and after the origin of the jet where it gradually arises, and disappear at the point where the jet boundary layer separates from the wall, where the wall pressure reaches atmospheric pressure (and the transverse gradient becomes zero). Experiments made in 1956 with turbulent air jets at a Reynolds number of 10 at various jet widths () show the pressures measured along a circularly curved wall (radius ) at a series of horizontal distance from the origin of the jet (see the diagram on the right).
Coandă effect | Wall jet
Such an interpretation is supported by the denser and higher clouds in the collars. The clouds lie at 70–72 km altitude in the collars—about 5 km higher than at the poles and low latitudes. A connection may exist between the cold collars and high-speed midlatitude jets in which winds blow as fast as 140 m/s. Such jets are a natural consequence of the Hadley-type circulation and should exist on Venus between 55–60° latitude. Odd structures known as polar vortices lie within the cold polar collars. They are giant hurricane-like storms four times larger than their terrestrial analogs. Each vortex has two "eyes"—the centres of rotation, which are connected by distinct S-shaped cloud structures.
Atmosphere of Venus | Circulation
A jet is a stream of fluid that is projected into a surrounding medium, usually from some kind of a nozzle, aperture or orifice. Jets can travel long distances without dissipating. Jet fluid has higher momentum compared to the surrounding fluid medium. In the case that the surrounding medium is assumed to be made up of the same fluid as the jet, and this fluid has a viscosity, the surrounding fluid is carried along with the jet in a process called entrainment. Some animals, notably cephalopods, move by jet propulsion, as do rocket engines and jet engines.
Jet (fluid) | Introduction
Clear-air turbulence is usually impossible to detect with the naked eye and very difficult to detect with a conventional radar, with the result that it is difficult for aircraft pilots to detect and avoid it. However, it can be remotely detected with instruments that can measure turbulence with optical techniques, such as scintillometers, Doppler LIDARs, or N-slit interferometers. Although the altitudes near the tropopause are usually cloudless, thin cirrus cloud can form where there are abrupt changes of air velocity, for example associated with jet streams. Lines of cirrus perpendicular to the jet stream indicate possible CAT, especially if the ends of the cirrus are dispersed, in which case the direction of dispersal can indicate if the CAT is stronger at the left or at the right of the jet stream.
Clear-air turbulence | Detection
At the urging of British scientific military strategist R. V. Jones, Bomber Command reorganized their attacks into streams carefully positioned to fly right down the middle of a cell. The introduction of the GEE navigation system allowed the RAF bombers to fly a long, tight, formation in the dark—a 'stream of bombers' flying a common route at the same speed to and from the target, each aircraft being allotted a height band and a time slot in a bomber stream to minimize the risk of formation collision.
Bomber stream | Introduction
That is, they appear "dark". The estimated angle of the jets to the line of sight is 30° and they may be precessing. One of the jets is colliding with a relatively dense part of the interstellar medium (ISM), forming an energized ring that can be detected by its radio emission. This collision appears to be forming a nebula that has been observed in the optical wavelengths. To produce this nebula, the jet must have an estimated average power of 4–, or . This is more than 1,000 times the power emitted by the Sun. There is no corresponding ring in the opposite direction because that jet is facing a lower density region of the ISM.
Cygnus X-1 | Jets
The Magellanic Stream is a stream of high-velocity clouds of gas extending from the Large and Small Magellanic Clouds over 100° through the Galactic south pole of the Milky Way. The stream contains a gaseous feature dubbed the "leading arm". The stream was sighted in 1965 and its relation to the Magellanic Clouds was established in 1974.
Magellanic Stream | Introduction
The jet blows up the dusty envelope of the star, giving rise to 0.3 parsec long molecular outflow.
HH 34 | Introduction
The stream is part of a large karst topography that covers a geologic watershed around Mammoth Cave and its underground rivers. The same limestone seep created the extensive streams and cave system of Mammoth Caves. The vegetation includes mature sycamore trees, ferns, and moss. The constant temperate climate causes a humid mist to cover the area in summer. The roots can be observed floating near the water's surface in large outgrowths. Thousands of gallons of fresh water gush from the system's source daily. The water stays year-round.
Johnson Springs | Introduction
The atmosphere responds by generating vertical wind shear to maintain thermal wind balance. The jet reaches its zenith in August, lying between the 16th and 17th parallels. In September, winds maximize near between the 12th and 13th parallels. The easterly jet weakens and drops southward during October and November.
African easterly jet | Formation and characteristics
These can occur when winds tear the cloud and incorporate the environmental air or when strong downdrafts evaporate the water.
Cumulus cloud | Description
The observed jet is the one that faces the earth and projects plasma towards Earth. There is also a jet heading away from Earth called a "counter jet". Close into the core, this counter jet is so much dimmer than the main jet that it is invisible in radio waves. The brightness of the counter jet is less than the main jet by a factor of 1250. This implies that the jet is relativistic with Γ about 15 (that is, the plasma is moving at 99.8% of the speed of light) and at an angle between 15° and 25° from the line of sight from the Earth.
Markarian 501 | Jet
Airstream may refer to: It may also relate to:
Airstream (disambiguation) | Introduction
This jet continues until the fuel depletes.
Trench effect | Introduction
The first vortex on Venus was discovered at the north pole by the Pioneer Venus mission in 1978. A discovery of the second large 'double-eyed' vortex at the south pole of Venus was made in the summer of 2006 by Venus Express, which came with no surprise. Images from the "Akatsuki" orbiter revealed something similar to jet stream winds in the low and middle cloud region, which extends from 45 to 60 kilometers in altitude. The wind speed maximized near the equator. In September 2017 JAXA scientists named this phenomenon 'Venusian equatorial jet'.
Atmosphere of Venus | Circulation
The storms on Jupiter are similar to thunderstorms on Earth. They reveal themselves via bright clumpy clouds about 1000 km in size, which appear from time to time in the belts' cyclonic regions, especially within the strong westward (retrograde) jets. In contrast to vortices, storms are short-lived phenomena; the strongest of them may exist for several months, while the average lifetime is only 3–4 days. They are believed to be due mainly to moist convection within Jupiter's troposphere. Storms are actually tall convective columns (plumes), which bring the wet air from the depths to the upper part of the troposphere, where it condenses in clouds.
Atmosphere of Jupiter | Storms and lightning
During El Niño events, increased precipitation is expected in California due to a more southerly, zonal, storm track. During the Niño portion of ENSO, increased precipitation falls along the Gulf coast and Southeast due to a stronger than normal, and more southerly, polar jet stream. Snowfall is greater than average across the southern Rockies and Sierra Nevada mountain range, and is well below normal across the Upper Midwest and Great Lakes states. The northern tier of the lower 48 exhibits above normal temperatures during the fall and winter, while the Gulf coast experiences below normal temperatures during the winter season.
Jet stream | El Niño
Any imbalance between these forces results in the acceleration of the parcel in the imbalance direction: upward if the buoyant force exceeds the weight, and downward if the weight exceeds the buoyancy force. The balance in the vertical direction is referred to as hydrostatic. Beyond the tropics, the dominant forces act in the horizontal direction, and the primary struggle is between the Coriolis force and the pressure gradient force. Balance between these two forces is referred to as geostrophic. Given both hydrostatic and geostrophic balance, one can derive the thermal wind relation: the vertical gradient of the horizontal wind is proportional to the horizontal temperature gradient.
Jet stream | Cause