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The average mass of the atmosphere is about 5 quadrillion (5 × 10 15) tonnes or 1/1,200,000 the mass of Earth. According to the American National Center for Atmospheric Research , "The total mean mass of the atmosphere is 5.1480 × 10 18 kg with an annual range due to water vapor of 1.2 or 1.5 × 10 15 kg, depending on whether surface pressure ...
Atmospheric pressure, also known as air pressure or barometric pressure (after the barometer), is the pressure within the atmosphere of Earth.The standard atmosphere (symbol: atm) is a unit of pressure defined as 101,325 Pa (1,013.25 hPa), which is equivalent to 1,013.25 millibars, [1] 760 mm Hg, 29.9212 inches Hg, or 14.696 psi. [2]
On Earth, the limit is around 18–19 km (11–12 mi; 59,000–62,000 ft) above sea level, [1] [2] above which atmospheric air pressure drops below 0.0618 atm (6.3 kPa, 47 mmHg, or about 1 psi). The U.S. Standard Atmospheric model sets the Armstrong limit at an altitude of 63,000 feet (19,202 m).
Where ρ is mass density, M is average molecular weight, P is pressure, T is temperature, and R is the ideal gas constant. The gas is held in place by so-called "hydrostatic" forces. That is to say, for a particular layer of gas at some altitude: the downward (towards the planet) force of its weight, the downward force exerted by pressure in ...
is the molar mass of dry air, approximately 0.028 9652 in kg⋅mol −1. [note 1] is the Boltzmann constant, 1.380 649 × 10 −23 in J⋅K −1 [note 1] is the molecular mass of dry air, approximately 4.81 × 10 −26 in kg. [note 1]
An air mass originating over northern Siberia in winter may be indicated as "cA". [3] The stability of an air mass may be shown using a third letter, either "k" (air mass colder than the surface below it) or "w" (air mass warmer than the surface below it). [3] An example of this might be a polar air mass blowing over the Gulf Stream, denoted as ...
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The application of the Showalter index is especially helpful when there is a cool, shallow air mass below 850 hPa that conceals the potential convective lifting. However, the index will underestimate the potential convective lifting if there are cool layers that extend above 850 hPa and it does not consider diurnal radiative changes or moisture ...