Various segments of Atmosphere & their significance
Earth's atmosphere is a layer of gases surrounding the planet Earth and retained by the Earth's gravity. It contains roughly (by molar content/volume) 78% nitrogen, 20.95% oxygen, 0.93% argon, 0.038% carbon dioxide, trace amounts of other gases, and a variable amount (average around 1%) of water vapor. This mixture of gases is commonly known as air. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation and reducing temperature extremes between day and night.
There is no definite boundary between the atmosphere and outer space. It slowly becomes thinner and fades into space. Three quarters of the atmosphere's mass is within 11 km of the planetary surface. In the United States, people who travel above an altitude of 80.5 km (50 statute miles) are designated astronauts. An altitude of 120 km (~75 miles or 400,000 ft) marks the boundary where atmospheric effects become noticeable during re-entry. The Kármán line, at 100 km (62 miles or 328,000 ft), is also frequently regarded as the boundary between atmosphere and outer space.
The temperature of the Earth's atmosphere varies with altitude; the mathematical relationship between temperature and altitude varies among six different atmospheric layers:
Troposphere: The troposphere is the lowest layer of the atmosphere; it begins at the surface and extends to between 7 km (23,000 ft) at the poles and 17 km (60,000 ft) at the equator, with some variation due to weather factors. The troposphere has a great deal of vertical mixing due to solar heating at the surface. This heating warms air masses, which makes them less dense so they rise. When an air mass raises the pressure upon it decreases so it expands, doing work against the opposing pressure of the surrounding air. To do work is to expend energy, so the temperature of the air mass decreases. As the temperature decreases, water vapor in the air mass may condense or solidify, releasing latent heat that further uplifts the air mass. This process determines the maximum rate of decline of temperature with height, called the adiabatic lapse rate.
Stratosphere: The stratosphere extends from the troposphere's 7 to 17 km (23,000 – 60,000 ft) range to about 50 km (160,000 ft). Temperature increases with height. The stratosphere contains the ozone layer, the part of the Earth's atmosphere which contains relatively high concentrations of ozone. "Relatively high" means a few parts per million—much higher than the concentrations in the lower atmosphere but still small compared to the main components of the atmosphere. It is mainly located in the lower portion of the stratosphere from approximately 15 to 35 km (50,000 – 115,000 ft) above Earth's surface, though the thickness varies seasonally and geographically.
Mesosphere: The mesosphere extends from about 50 km (160,000 ft) to the range of 80 to 85 km (265,000 – 285,000 ft), temperature decreasing with height.
Thermosphere: From 80 – 85 km (265,000 – 285,000 ft) to 640+ km (400+ mi), temperature increasing with height.
Ionosphere: It is the part of the atmosphere that is ionized by solar radiation. It plays an important part in atmospheric electricity and forms the inner edge of the magnetosphere. It has practical importance because, among other functions, it influences radio propagation to distant places on the Earth. It is located in the thermosphere and is responsible for auroras.
Exosphere: From 500 – 1000 km (300 – 600 mi) up to 10,000 km (6,000 mi), free-moving particles that may migrate into and out of the magnetosphere or the solar wind.
The boundaries between these regions are named the tropopause, stratopause, mesopause, thermopause and exobase.
The average temperature of the atmosphere at the surface of Earth is 15 °C (59 °F).
The average atmospheric pressure, at sea level, is about 101.3 kilopascals [1 pascal (Pa) = 1 N/m2 = 1 kg/(m•s2), The newton is the unit of force derived in the SI system; it is equal to the amount of net force required to accelerate a mass of one kilogram at a rate of one meter per second per second.] [about 14.7 psi, the pound per square inch or, more accurately, pound-force per square inch. It is the pressure resulting from a force of one pound-force applied to an area of one square inch:1 psi approximately equals 6,894.757 Pa, where pascal (Pa) is the SI unit of pressure.]; total atmospheric mass is 5.2 x 1018 kg (1.135×1019 lb).
Atmospheric pressure is a direct result of the total weight of the air above the point at which the pressure is measured. This means that air pressure varies with location and time, because the amount (and weight) of air above the earth varies with location and time.
Atmospheric pressure decreases with height, dropping by 50% at an altitude of about 5.6 km (18,000 ft). Equivalently, about 50% of the total atmospheric mass is within the lowest 5.6 km. This pressure drop is approximately exponential, so that each doubling in altitude results in an approximate decrease in pressure by half. However, because of changes in temperature throughout the atmospheric column, as well as the fact that the force of gravity begins to decrease at great altitudes, a single equation does not model atmospheric pressure through all altitudes (it is modeled in 7 exponentially decreasing layers, in the equations given above).
Even in the exosphere, the atmosphere is still present (as can be seen for example by the effects of atmospheric drag on satellites).
The following published data are given for reference:
50% of the atmosphere by mass is below an altitude of 5.6 km.
90% of the atmosphere by mass is below an altitude of 16 km. The common cruising altitude of commercial airliners is about 10 km.
99.99997% of the atmosphere by mass is below 100 km (almost all of it). The highest X-15 plane flight in 1963 reached an altitude of 354,300 ft or 108 km.
Therefore, most of the atmosphere (99.9997%) is below 100 km, although in the rarefied region above this there are auroras and other atmospheric effects.
Composition of dry atmosphere, by volume ppmv: parts per million by volume
Nitrogen (N2) - 780,840 ppmv (78.084%) Oxygen (O2) - 209,460 ppmv (20.946%)
Argon (Ar) - 9,340 ppmv (0.9340%) Carbon dioxide (CO2) - 383 ppmv (0.0383%)
Neon (Ne) - 18.18 ppmv Helium (He) - 5.24 ppmv Methane (CH4) - 1.745 ppmv
Krypton (Kr) - 1.14 ppmv Hydrogen (H2) - 0.55 ppmv
Not included in above dry atmosphere:
Water vapor (H2O) ~0.25% over full atmosphere, typically 1% to 4% near surface
Minor components of air not listed above include
nitrous oxide - 0.5 ppmv xenon - 0.09 ppmv ozone - 0.0 to 0.07 ppmv nitrogen dioxide - 0.02 ppmv iodine - 0.01 ppmv carbon monoxide – trace ammonia
The density of air at sea level is about 1.2 kg/m3(1.2 g/L). Natural variations of the barometric pressure occur at any one altitude as a consequence of weather. This variation is relatively small for inhabited altitudes but much more pronounced in the outer atmosphere and space due to variable solar radiation.
The atmospheric density decreases as the altitude increases. This variation can be approximately modeled using the barometric formula. More sophisticated models are used by meteorologists and space agencies to predict weather and orbital decay of satellites.
The average mass of the atmosphere is about 5,000 trillion metric tons or 1/1,200,000 the mass of Earth. According to the National Center for Atmospheric Research, "The total mean mass of the atmosphere is 5.1480×1018 kg with an annual range due to water vapor of 1.2 or 1.5×1015 kg depending on whether surface pressure or water vapor data are used; somewhat smaller than the previous estimate. The mean mass of water vapor is estimated as 1.27×1016 kg and the dry air mass as 5.1352 ±0.0003×1018 kg."
Earth's atmosphere is a layer of gases surrounding the planet Earth and retained by the Earth's gravity. It contains roughly (by molar content/volume) 78% nitrogen, 20.95% oxygen, 0.93% argon, 0.038% carbon dioxide, trace amounts of other gases, and a variable amount (average around 1%) of water vapor. This mixture of gases is commonly known as air. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation and reducing temperature extremes between day and night.
There is no definite boundary between the atmosphere and outer space. It slowly becomes thinner and fades into space. Three quarters of the atmosphere's mass is within 11 km of the planetary surface. In the United States, people who travel above an altitude of 80.5 km (50 statute miles) are designated astronauts. An altitude of 120 km (~75 miles or 400,000 ft) marks the boundary where atmospheric effects become noticeable during re-entry. The Kármán line, at 100 km (62 miles or 328,000 ft), is also frequently regarded as the boundary between atmosphere and outer space.
The temperature of the Earth's atmosphere varies with altitude; the mathematical relationship between temperature and altitude varies among six different atmospheric layers:
Troposphere: The troposphere is the lowest layer of the atmosphere; it begins at the surface and extends to between 7 km (23,000 ft) at the poles and 17 km (60,000 ft) at the equator, with some variation due to weather factors. The troposphere has a great deal of vertical mixing due to solar heating at the surface. This heating warms air masses, which makes them less dense so they rise. When an air mass raises the pressure upon it decreases so it expands, doing work against the opposing pressure of the surrounding air. To do work is to expend energy, so the temperature of the air mass decreases. As the temperature decreases, water vapor in the air mass may condense or solidify, releasing latent heat that further uplifts the air mass. This process determines the maximum rate of decline of temperature with height, called the adiabatic lapse rate.
Stratosphere: The stratosphere extends from the troposphere's 7 to 17 km (23,000 – 60,000 ft) range to about 50 km (160,000 ft). Temperature increases with height. The stratosphere contains the ozone layer, the part of the Earth's atmosphere which contains relatively high concentrations of ozone. "Relatively high" means a few parts per million—much higher than the concentrations in the lower atmosphere but still small compared to the main components of the atmosphere. It is mainly located in the lower portion of the stratosphere from approximately 15 to 35 km (50,000 – 115,000 ft) above Earth's surface, though the thickness varies seasonally and geographically.
Mesosphere: The mesosphere extends from about 50 km (160,000 ft) to the range of 80 to 85 km (265,000 – 285,000 ft), temperature decreasing with height.
Thermosphere: From 80 – 85 km (265,000 – 285,000 ft) to 640+ km (400+ mi), temperature increasing with height.
Ionosphere: It is the part of the atmosphere that is ionized by solar radiation. It plays an important part in atmospheric electricity and forms the inner edge of the magnetosphere. It has practical importance because, among other functions, it influences radio propagation to distant places on the Earth. It is located in the thermosphere and is responsible for auroras.
Exosphere: From 500 – 1000 km (300 – 600 mi) up to 10,000 km (6,000 mi), free-moving particles that may migrate into and out of the magnetosphere or the solar wind.
The boundaries between these regions are named the tropopause, stratopause, mesopause, thermopause and exobase.
The average temperature of the atmosphere at the surface of Earth is 15 °C (59 °F).
The average atmospheric pressure, at sea level, is about 101.3 kilopascals [1 pascal (Pa) = 1 N/m2 = 1 kg/(m•s2), The newton is the unit of force derived in the SI system; it is equal to the amount of net force required to accelerate a mass of one kilogram at a rate of one meter per second per second.] [about 14.7 psi, the pound per square inch or, more accurately, pound-force per square inch. It is the pressure resulting from a force of one pound-force applied to an area of one square inch:1 psi approximately equals 6,894.757 Pa, where pascal (Pa) is the SI unit of pressure.]; total atmospheric mass is 5.2 x 1018 kg (1.135×1019 lb).
Atmospheric pressure is a direct result of the total weight of the air above the point at which the pressure is measured. This means that air pressure varies with location and time, because the amount (and weight) of air above the earth varies with location and time.
Atmospheric pressure decreases with height, dropping by 50% at an altitude of about 5.6 km (18,000 ft). Equivalently, about 50% of the total atmospheric mass is within the lowest 5.6 km. This pressure drop is approximately exponential, so that each doubling in altitude results in an approximate decrease in pressure by half. However, because of changes in temperature throughout the atmospheric column, as well as the fact that the force of gravity begins to decrease at great altitudes, a single equation does not model atmospheric pressure through all altitudes (it is modeled in 7 exponentially decreasing layers, in the equations given above).
Even in the exosphere, the atmosphere is still present (as can be seen for example by the effects of atmospheric drag on satellites).
The following published data are given for reference:
50% of the atmosphere by mass is below an altitude of 5.6 km.
90% of the atmosphere by mass is below an altitude of 16 km. The common cruising altitude of commercial airliners is about 10 km.
99.99997% of the atmosphere by mass is below 100 km (almost all of it). The highest X-15 plane flight in 1963 reached an altitude of 354,300 ft or 108 km.
Therefore, most of the atmosphere (99.9997%) is below 100 km, although in the rarefied region above this there are auroras and other atmospheric effects.
Composition of dry atmosphere, by volume ppmv: parts per million by volume
Nitrogen (N2) - 780,840 ppmv (78.084%) Oxygen (O2) - 209,460 ppmv (20.946%)
Argon (Ar) - 9,340 ppmv (0.9340%) Carbon dioxide (CO2) - 383 ppmv (0.0383%)
Neon (Ne) - 18.18 ppmv Helium (He) - 5.24 ppmv Methane (CH4) - 1.745 ppmv
Krypton (Kr) - 1.14 ppmv Hydrogen (H2) - 0.55 ppmv
Not included in above dry atmosphere:
Water vapor (H2O) ~0.25% over full atmosphere, typically 1% to 4% near surface
Minor components of air not listed above include
nitrous oxide - 0.5 ppmv xenon - 0.09 ppmv ozone - 0.0 to 0.07 ppmv nitrogen dioxide - 0.02 ppmv iodine - 0.01 ppmv carbon monoxide – trace ammonia
The density of air at sea level is about 1.2 kg/m3(1.2 g/L). Natural variations of the barometric pressure occur at any one altitude as a consequence of weather. This variation is relatively small for inhabited altitudes but much more pronounced in the outer atmosphere and space due to variable solar radiation.
The atmospheric density decreases as the altitude increases. This variation can be approximately modeled using the barometric formula. More sophisticated models are used by meteorologists and space agencies to predict weather and orbital decay of satellites.
The average mass of the atmosphere is about 5,000 trillion metric tons or 1/1,200,000 the mass of Earth. According to the National Center for Atmospheric Research, "The total mean mass of the atmosphere is 5.1480×1018 kg with an annual range due to water vapor of 1.2 or 1.5×1015 kg depending on whether surface pressure or water vapor data are used; somewhat smaller than the previous estimate. The mean mass of water vapor is estimated as 1.27×1016 kg and the dry air mass as 5.1352 ±0.0003×1018 kg."
answer for segments of environment :ES
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