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Pressure as a function of the height above the sea level. There are two equations for computing pressure as a function of height. The first equation is applicable to the atmospheric layers in which the temperature is assumed to vary with altitude at a non null lapse rate of : = [,, ()] ′, The second equation is applicable to the atmospheric layers in which the temperature is assumed not to ...
It indicates altitude obtained when an altimeter is set to an agreed baseline pressure under certain circumstances in which the aircraft’s altimeter would be unable to give a useful altitude readout. Examples would be landing at a high altitude or near sea level under conditions of exceptionally high air pressure.
Using the ideal gas law and the hydrostatic equilibrium equation, gives ¯, which has the solution = (()), where is the gas mass density at the midplane of the disk at a distance r from the center of the star, and is the disk scale height with = ¯ (/ ) (/ ) (/) (¯ / ) , with the solar mass, the astronomical unit, and the atomic mass unit.
at each geopotential altitude, where g is the standard acceleration of gravity, and R specific is the specific gas constant for dry air (287.0528J⋅kg −1 ⋅K −1). The solution is given by the barometric formula. Air density must be calculated in order to solve for the pressure, and is used in calculating dynamic pressure for moving vehicles.
In practice, since temperature usually drops with altitude, the graphs are usually mostly vertical (see examples linked to below). The major use for skew-T log-P diagrams is the plotting of radiosonde soundings , which give a vertical profile of the temperature and dew point temperature throughout the troposphere and lower stratosphere .
For example, the U.S. Standard Atmosphere derives the values for air temperature, pressure, and mass density, as a function of altitude above sea level. Other static atmospheric models may have other outputs, or depend on inputs besides altitude.
The graph on the right above was developed for a temperature of 15 °C and a relative humidity of 0%. At low altitudes above sea level, the pressure decreases by about 1.2 kPa (12 hPa) for every 100 metres. For higher altitudes within the troposphere, the following equation (the barometric formula) relates atmospheric pressure p to altitude h:
Thus the standard consists of a tabulation of values at various altitudes, plus some formulas by which those values were derived. To allow modeling conditions below mean sea level , the troposphere is actually extended to −2,000 feet (−610 m), where the temperature is 66.1 °F (18.9 °C), pressure is 15.79 pounds per square inch (108,900 Pa ...