"sublimated into polar-mesospheric noctilucent clouds. These are the highest clouds in the atmosphere and may be visible to the naked eye if sunlight reflects off them about an hour or two after sunset or a similar length of time 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 the layer where most meteors burn up upon atmospheric entrance. It is too high above Earth to be accessible to jet-powered aircraft"
"for applications such as submillimetre astronomy. High-altitude balloons are often flown by students and by amateur groups to altitudes on the order of , for both scientific and educational purposes. Mesosphere The mesosphere (; from Greek ""mesos"" ""middle"" ) is the layer of the Earth's atmosphere that is directly above the stratosphere and directly below the thermosphere. In the mesosphere, temperature decreases as the altitude increases. This characteristic is used to define its limits: it begins at the top of the stratosphere (sometimes called the stratopause), and ends at the mesopause, which is the coldest part of Earth's atmosphere with"
"Mesosphere The mesosphere (; from Greek ""mesos"" ""middle"" ) is the layer of the Earth's atmosphere that is directly above the stratosphere and directly below the thermosphere. In the mesosphere, temperature decreases as the altitude increases. This characteristic is used to define its limits: it begins at the top of the stratosphere (sometimes called the stratopause), and ends at the mesopause, which is the coldest part of Earth's atmosphere with temperatures below . The exact upper and lower boundaries of the mesosphere vary with latitude and with season (higher in winter and at the tropics, lower in summer and at"
"The lowest layer is the troposphere, which extends from the surface to the bottom of the stratosphere. Three quarters of the atmosphere's mass resides within the troposphere, and is the layer within which the Earth's terrestrial weather develops. The depth of this layer varies between 17 km at the equator to 7 km at the poles. The stratosphere, extending from the top of the troposphere to the bottom of the mesosphere, contains the ozone layer. The ozone layer ranges in altitude between 15 and 35 km, and is where most of the ultraviolet radiation from the Sun is absorbed. The"
"main layers: the troposphere, between altitudes of −300 and 50 km and pressures from 100 to 0.1 bar; the stratosphere, spanning altitudes between 50 and 4000 km and pressures between and the thermosphere/exosphere extending from 4000 km to as high as a few Uranus radii from the surface. There is no mesosphere. The troposphere is the lowest and densest part of the atmosphere and is characterised by a decrease in temperature with altitude. The temperature falls from about 320 K at the base of the troposphere at −300 km to about 53 K at 50 km. The temperature at the"
"geese (""Anser indicus"") reportedly overfly Mount Everest's summit, which is . In 1902 Léon Teisserenc de Bort from France and Richard Assmann from Germany, in separate but coordinated publications and following years of observations, published the discovery of an isothermal layer at around 11–14 km, which is the base of the lower stratosphere. This was based on temperature profiles from mostly unmanned and a few manned instrumented balloons. Stratosphere The stratosphere () is the second major layer of Earth's atmosphere, just above the troposphere, and below the mesosphere. The stratosphere is stratified in temperature, with warmer layers higher and cooler"
"Troposphere The troposphere is the lowest layer of Earth's atmosphere, and is also where nearly all weather conditions take place. It contains approximately 75% of the atmosphere's mass and 99% of the total mass of water vapor and aerosols. The average height of the troposphere are in the tropics, in the middle latitudes, and in the polar regions in winter. The lowest part of the troposphere, where friction with the Earth's surface influences air flow, is the planetary boundary layer. This layer is typically a few hundred meters to deep depending on the landform and time of day. Atop the"
"International Space Station orbits in this layer, between . 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 to the mesopause at above sea level. Temperatures drop with increasing altitude to 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 . Just below the mesopause, the air is so cold that even the very scarce water vapor at this altitude can be"
"Planetary boundary layer In meteorology the planetary boundary layer (PBL), also known as the atmospheric boundary layer (ABL) or ""peplosphere"", is the lowest part of the atmosphere and its behavior is directly influenced by its contact with a planetary surface . On Earth it usually responds to changes in surface radiative forcing in an hour or less. In this layer physical quantities such as flow velocity, temperature, moisture, etc., display rapid fluctuations (turbulence) and vertical mixing is strong. Above the PBL is the ""free atmosphere"" where the wind is approximately geostrophic (parallel to the isobars) , while within the PBL"
"level convergence, cyclone formation, and positive vertical velocity. Therefore, identifying regions of upper air divergence is an important step in forecasting the formation of a surface low pressure area. Troposphere The troposphere is the lowest layer of Earth's atmosphere, and is also where nearly all weather conditions take place. It contains approximately 75% of the atmosphere's mass and 99% of the total mass of water vapor and aerosols. The average height of the troposphere are in the tropics, in the middle latitudes, and in the polar regions in winter. The lowest part of the troposphere, where friction with the Earth's"
"The ""stratosphere"" is the next layer and extends from 18 km to about 50 km. The third layer is the ""mesosphere"" which extends from 50 km to about 80 km. There are other layers above 80 km, but they are insignificant with respect to atmospheric dispersion modeling. The lowest part of the troposphere is called the ""atmospheric boundary layer (ABL)"" or the ""planetary boundary layer (PBL)"" . The air temperature of the atmosphere decreases with increasing altitude until it reaches what is called a ""inversion layer"" (where the temperature increases with increasing altitude) that caps the Convective Boundary Layer, typically"
"the poles), but the lower boundary is usually located at heights from above the Earth's surface and the upper boundary (mesopause) is usually around . The stratosphere and the mesosphere are collectively referred to as the ""middle atmosphere"", which spans heights from approximately to . The mesopause, at an altitude of , separates the mesosphere from the thermosphere—the second-outermost layer of the Earth's atmosphere. This is also around the same altitude as the turbopause, below which different chemical species are well mixed due to turbulent eddies. Above this level the atmosphere becomes non-uniform; the scale heights of different chemical species"
"Antarctica. The ionosphere is a shell of electrons and electrically charged atoms and molecules that surrounds the Earth, stretching from a height of about to more than . It exists primarily due to ultraviolet radiation from the Sun. The lowest part of the Earth's atmosphere, the troposphere extends from the surface to about . Above that is the stratosphere, followed by the mesosphere. In the stratosphere incoming solar radiation creates the ozone layer. At heights of above , in the thermosphere, the atmosphere is so thin that free electrons can exist for short periods of time before they are captured"
"the minimum altitude for orbital spacecraft due to high atmospheric drag. It has only been accessed through the use of sounding rockets, which are only capable of taking mesospheric measurements for a few minutes per mission. As a result, it is the least-understood part of the atmosphere, resulting in the humorous moniker ""ignorosphere"". The presence of red sprites and blue jets (electrical discharges or lightning within the lower mesosphere), noctilucent clouds, and density shears within this poorly understood layer are of current scientific interest. Near space was first explored in the 1930s. The early flights flew to the edge of"
"temperature would be , in contrast to the current , and life on Earth probably would not exist in its current form. In May 2017, glints of light, seen as twinkling from an orbiting satellite a million miles away, were found to be reflected light from ice crystals in the atmosphere. Earth's atmosphere has no definite boundary, slowly becoming thinner and fading into outer space. Three-quarters of the atmosphere's mass is contained within the first of the surface. This lowest layer is called the troposphere. Energy from the Sun heats this layer, and the surface below, causing expansion of the"
"vapor, on average around 1% at sea level, and 0.4% over the entire atmosphere. Air content and atmospheric pressure vary at different layers, and air suitable for use in photosynthesis by terrestrial plants and breathing of terrestrial animals is found only in Earth's troposphere and in artificial atmospheres. The atmosphere has a mass of about 5.15 kg, three quarters of which is within about of the surface. The atmosphere becomes thinner and thinner with increasing altitude, with no definite boundary between the atmosphere and outer space. The Kármán line, at , or 1.57% of Earth's radius, is often used as"
"the terms ""near space"" and ""upper atmosphere,"" so that only the layers closest to the Karman line are called near space. Within the mesosphere, temperature decreases with increasing height, due to decreasing absorption of solar radiation by the rarefied atmosphere and increasing cooling by CO radiative emission. The top of the mesosphere, called the mesopause, is the coldest part of Earth's atmosphere. Temperatures in the upper mesosphere fall as low as , varying according to latitude and season. The main dynamic features in this region are strong zonal (East-West) winds, atmospheric tides, internal atmospheric gravity waves (commonly called ""gravity waves""),"
"exists from about 150 to 220 km above the surface of the Earth and only during daylight hours. It is composed of a mixture of molecular ions O and NO, and atomic ions O. Above the F1 region, atomic oxygen becomes the dominant constituent because lighter particles tend to occupy higher altitudes above the turbopause (at ~100 km). This atomic oxygen provides the O atomic ions that make up the F2 layer. The F1 layer has approximately 5 × 10 e/cm (free electrons per cubic centimeter) at noontime and minimum sunspot activity, and increases to roughly 2 × 10 e/cm"
"itself. The line is approximately at the turbopause, above which atmospheric gasses are not well-mixed. The mesopause atmospheric temperature minimum has been measured to vary from 85 to 100 km, which places the line at or near the bottom of the thermosphere. In the final chapter of his autobiography Kármán addresses the issue of the edge of outer space: An atmosphere does not abruptly end at any given height, but becomes progressively thinner with altitude. Also, depending on how the various layers that make up the space around the Earth are defined (and depending on whether these layers are considered"
"to the interaction of thermal radiation effects on atmospheric aerosols and convection transfer close to the ground. L. A. Ramdas Lakshminarayanapuram Ananthakrishnan Ramdas (3 June 1900–1 January 1979) was an Indian physicist and meteorologist, known for discovering the atmospheric phenomenon of the Ramdas layer or Lifted Temperature Minimum where the lowest temperature in the atmosphere is not on the ground but a few tens of centimeters above the ground resulting. This can be seen in thin layer fogs which are at some height above the ground. He has been called the father of agricultural meteorology in India. Ramdas was born"
"Mesopause The mesopause is the temperature minimum at the boundary between the mesosphere and the thermosphere atmospheric regions. Due to the lack of solar heating and very strong radiative cooling from carbon dioxide, the mesosphere is the coldest region on Earth with temperatures as low as -100 °C (-148 °F or 173 K). The altitude of the mesopause for many years was assumed to be at around 85 km (53 mi.), but observations to higher altitudes and modeling studies in the last 10 years have shown that in fact the mesopause consists of two minima - one at about 85"
"such as the Sun, the lowest level of the atmosphere, just above the photosphere, is the thin chromosphere region, where spicules appear and stellar flares begin. Above this is the transition region, where the temperature rapidly increases within a distance of only . Beyond this is the corona, a volume of super-heated plasma that can extend outward to several million kilometres. The existence of a corona appears to be dependent on a convective zone in the outer layers of the star. Despite its high temperature, and the corona emits very little light, due to its low gas density. The corona"
"Atmosphere An atmosphere (from Modern Greek ἀτμός ""(atmos)"", meaning 'vapour', and σφαῖρα ""(sphaira)"", meaning 'sphere') is a layer or a set of layers of gases surrounding a planet or other material body, that is held in place by the gravity of that body. An atmosphere is more likely to be retained if the gravity it is subject to is high and the temperature of the atmosphere is low. The atmosphere of Earth is composed of nitrogen (about 78%), oxygen (about 21%), argon (about 0.9%) , carbon dioxide (0.03%) and other gases in trace amounts. Oxygen is used by most organisms"
"The base of the lower mantle is at about 2700 km. ""Mesosphere"" (not to be confused with mesosphere, a layer of the atmosphere) is derived from “mesospheric shell”, coined by Reginald Aldworth Daly, a Harvard University geology professor. In the pre-plate tectonics era, Daly (1940) inferred that the outer Earth consisted of three spherical layers: lithosphere (including the crust), asthenosphere, and mesospheric shell. Daly’s hypothetical depths to the lithosphere–asthenosphere boundary ranged from , and the top of the mesospheric shell (base of the asthenosphere) were from . Thus, Daly’s asthenosphere was inferred to be thick. According to Daly, the base"
"out. Mesopause The mesopause is the temperature minimum at the boundary between the mesosphere and the thermosphere atmospheric regions. Due to the lack of solar heating and very strong radiative cooling from carbon dioxide, the mesosphere is the coldest region on Earth with temperatures as low as -100 °C (-148 °F or 173 K). The altitude of the mesopause for many years was assumed to be at around 85 km (53 mi.), but observations to higher altitudes and modeling studies in the last 10 years have shown that in fact the mesopause consists of two minima - one at about"
"Tropospheric ozone Ozone (O) is a trace gas of the troposphere, with an average concentration of 20-30 parts per billion by volume (ppbv), with close to 100 ppbv in polluted areas. . Ozone is also an important constituent of the stratosphere, where the ozone layer exists. The troposphere is the lowest layer of the Earth's atmosphere. It extends from the ground up to a variable height of approximately 14 kilometers above sea level. Ozone is least concentrated in the ground layer (or planetary boundary layer) of the troposphere. It's concentration increases as height above sea level increases, with a maximum"
"the top of the thermosphere at an altitude of about 700 km above sea level, to about 10,000 km (6,200 mi; 33,000,000 ft) where it merges into the solar wind. This layer 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 kilometers without colliding with one another. Thus, the exosphere no longer behaves like a gas, and the particles constantly escape into space. These free-moving particles follow ballistic trajectories and may"
"Stratopause The stratopause (formerly Mesopeak) is the level of the atmosphere which is the boundary between two layers: the stratosphere and the mesosphere. In the stratosphere the temperature increases with altitude, and the stratopause is the region where a maximum in the temperature occurs. This atmospheric feature is not only associated with Earth: it occurs on any other planet or moon that has an atmosphere as well. On Earth, the stratopause is high above the Earth's surface. The atmospheric pressure is around 1/1000 of the pressure at sea level. The temperature in the stratopause is -15 degrees Celsius (5 degrees"
"World Meteorological Organization: The tropopause as defined above renders as a first-order discontinuity surface, that is, ""temperature"" as a function of height varies continuously through the atmosphere but the ""temperature gradient"" does not. The troposphere is the lowest layer of the Earth's atmosphere; it is located right above the planetary boundary layer, and is the layer in which most weather phenomena take place. The troposphere contains the boundary layer, and ranges in height from an average of at the poles, to at the Equator. In the absence of inversions and not considering moisture, the temperature lapse rate for this layer"
"Thermopause The thermopause is the atmospheric boundary of Earth's energy system, located at the top of the thermosphere. The temperature of the thermopause could range from absolute zero to . Below this, the atmosphere is defined to be active on the insolation received, due to the increased presence of heavier gases such as monatomic oxygen. The solar constant is thus expressed at the thermopause. Beyond (above) this, the exosphere describes the thinnest remainder of atmospheric particles with large mean free path, mostly hydrogen and helium. As a limit for the exosphere this boundary is also called ""exobase"". The exact altitude"
"atmosphere, passing Earth's surface only away (about one Earth radius or one-sixtieth of the distance to the Moon). Because it was very small (6 meters/20 feet), FU was detected only hours before its closest approach. If it had collided with Earth, it probably would have disintegrated harmlessly in the atmosphere. On February 4, 2011, an asteroid designated , estimated at in diameter, passed within of the Earth, setting a new record for closest approach without impact, which still stands . On November 8, 2011, asteroid , relatively large at about in diameter, passed within (0.85 lunar distances) of Earth. On"
"by 2050. Tropospheric or ground-level ozone (O3) is the ozone present in the lowest portion of the atmosphere (up to 10–15 km above the ground). It is responsible for a large part of the human enhancement of the global greenhouse effect and has a lifetime of a few days to a few weeks. It is not directly emitted but formed by sunlight-driven oxidation of other agents, called ozone precursors, in particular methane (CH4) but also carbon monoxide (CO), non-methane volatile organic compounds (NMVOCs) and nitrogen oxides (NOX). Tropospheric ozone is a harmful pollutant that has detrimental impacts on human health"
"upper part of the thermosphere, where the mean free path of the molecules exceeds the scale height, is called the exosphere. The lower boundary of the Uranian exosphere, the exobase, is located at a height of about 6,500 km, or 1/4 of the planetary radius, above the surface. The exosphere is unusually extended, reaching as far as several Uranian radii from the planet. It is made mainly of hydrogen atoms and is often called the hydrogen corona of Uranus. The high temperature and relatively high pressure at the base of the thermosphere explain in part why Uranus's exosphere is so"