Atmosphere of Earth
It lies above the troposphere and is separated from it by the tropopause. Augustine Coordinator or to register by phone call 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. The division of the atmosphere into layers mostly by reference to temperature is discussed above. Most conventional aviation activity takes place in the troposphere, and it is the only layer that can be accessed by propeller-driven aircraft. This is sometimes referred to as a unit of standard atmospheres atm.
Retrieved 20 May Please help improve this section by adding citations to reliable sources. Consequently, the stratosphere is almost completely free of clouds and other forms of weather. If you need to cancel you may be eligible for a refund or event rain check, based on our cancellation policy , provided you contact us before the event day. This is sometimes referred to as a unit of standard atmospheres atm.
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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 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 the tropopause. It contains the ozone layer, which is the part of Earth's atmosphere that contains relatively high concentrations of that gas.
The stratosphere defines a layer in which temperatures rise with increasing altitude. This rise in temperature is caused by the absorption of ultraviolet radiation UV radiation from the Sun by the ozone layer , which restricts turbulence and mixing. 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.
The troposphere is the lowest layer of Earth's atmosphere. The troposphere is bounded above by the tropopause , a boundary marked in most places by a temperature inversion i. 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. Earth's surface is typically the warmest section of the troposphere.
Fifty percent of the total mass of the atmosphere is located in the lower 5. 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 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. Within the five principal layers that are largely determined by temperature, several secondary layers may be distinguished by other properties:.
The average atmospheric pressure at sea level is defined by the International Standard Atmosphere as pascals This is sometimes referred to as a unit of standard atmospheres atm.
Total atmospheric mass is 5. 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 from sea level, it would terminate abruptly at an altitude of 8. It actually decreases exponentially with altitude, dropping by half every 5.
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. In summary, the mass of Earth's atmosphere is distributed approximately as follows: By comparison, the summit of Mt. Meteors begin to glow in this region, though the larger ones may not burn up until they penetrate more deeply.
The division of the atmosphere into layers mostly by reference to temperature is discussed above. Because in an ideal gas of constant composition the speed of sound depends only on temperature and not on the gas 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 is about 1. 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 orbital decay of satellites. The mean mass of water vapor is estimated as 1. Solar radiation or sunlight is the energy Earth receives from the Sun. Earth also emits radiation back into space, but at longer wavelengths that we cannot see. Part of the incoming and emitted radiation is absorbed or reflected by the atmosphere.
In May , 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. 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 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 to reach your eye. Much of 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 wavelengths shorter than nanometers. When a molecule absorbs a photon, it increases the energy of the molecule.
This heats the atmosphere, but 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.
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 centimeter to about eleven-meter 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. 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 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 is close to, but just greater than 1. Systematic variations in refractive index can lead to the bending of light rays over long optical paths. One example is that, under some circumstances, observers onboard 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 the temperature gradient is large. An example of such effects is the mirage. Atmospheric circulation is the large-scale movement of air through the troposphere, and the means with ocean circulation by which heat is distributed around Earth.
The large-scale structure of the atmospheric circulation varies from year to year, but the basic structure remains fairly constant because it is determined by Earth's rotation rate and the difference in solar radiation between the equator and poles. The first atmosphere consisted of gases in the solar nebula , primarily hydrogen.
There were probably simple hydrides such as those now found in the gas giants Jupiter and Saturn , notably water vapor, methane and ammonia.
Outgassing from volcanism , supplemented by gases produced during the late heavy bombardment of Earth by huge asteroids , produced the next atmosphere, consisting largely of nitrogen plus carbon dioxide and inert gases. Water-related sediments have been found that date from as early as 3. The influence of life has to be taken into account rather soon in the history of the atmosphere, because hints of early life-forms appear as early as 3.
The geological record however shows a continuous relatively warm surface during the complete early temperature record of Earth — with the exception of one cold glacial phase about 2. In the late Archean Eon an oxygen-containing atmosphere began to develop, apparently produced by photosynthesizing cyanobacteria see Great Oxygenation Event , which have been found as stromatolite fossils from 2.
The early basic carbon isotopy isotope ratio proportions strongly suggests conditions similar to the current, and that the fundamental features of the carbon cycle became established as early as 4 billion years ago. Ancient sediments in the Gabon dating from between about 2, and 2, million years ago provide a record of Earth's dynamic oxygenation evolution.
These fluctuations in oxygenation were likely driven by the Lomagundi carbon isotope excursion. The constant re-arrangement of continents by plate tectonics influences the long-term evolution of the atmosphere by transferring carbon dioxide to and from large continental carbonate stores. Free oxygen did not exist in the atmosphere until about 2. Before this time, any oxygen produced by photosynthesis was consumed by oxidation of reduced materials, notably iron.
Molecules of free oxygen did not start to accumulate in the atmosphere until the rate of production of oxygen began to exceed the availability of reducing materials that removed oxygen. This point signifies a shift from a reducing atmosphere to an oxidizing atmosphere. Two main processes govern changes in the atmosphere: Plants use carbon dioxide from the atmosphere , releasing oxygen.
Breakdown of pyrite and volcanic eruptions release sulfur into the atmosphere, which oxidizes and hence reduces the amount of oxygen in the atmosphere. However, volcanic eruptions also release carbon dioxide, which plants can convert to oxygen. The exact cause of the variation of the amount of oxygen in the atmosphere is not known. Periods with much oxygen in the atmosphere are associated with rapid development of animals.
Air pollution is the introduction into the atmosphere of chemicals , particulate matter or biological materials that cause harm or discomfort to organisms. The scientific consensus is that the anthropogenic greenhouse gases currently accumulating in the atmosphere are the main cause of global warming.
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It actually decreases exponentially with altitude, dropping by half every 5. Click here to register.
This is sometimes referred to as seped unit of standard atmospheres atm. Speed dating vancouver reviews of Earth and Paleoclimatology. Oxford, Oxford University Press. Datiny atmosphere of Earth is the layer of gases, commonly known as airthat surrounds the planet Earth and is retained by Earth's gravity. The first atmosphere consisted of gases in the solar nebulaprimarily hydrogen. Much speed dating vancouver reviews the blue light has been scattered out, leaving the red light in a sunset. By comparison, the summit of Mt.
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