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The first equation is applicable to the standard model of the troposphere in which the temperature is assumed to vary with altitude at a lapse rate of ; the second equation is applicable to the standard model of the stratosphere in which the temperature is assumed not to vary with altitude. Equation 1: = [()] ()
Density and viscosity are recalculated at the resultant temperature and pressure using the ideal gas equation of state. Hot day, Cold day, Tropical, and Polar temperature profiles with altitude have been defined for use as performance references, such as United States Department of Defense MIL-STD-210C, and its successor MIL-HDBK-310. [6]
The variation in temperature that occurs from the highs of the day to the cool of nights is called diurnal temperature variation. Temperature ranges can also be based on periods of a month or a year. The size of ground-level atmospheric temperature ranges depends on several factors, such as: Average air temperature; Average humidity; The regime ...
It varies with the temperature and pressure of the parcel and is often in the range 3.6 to 9.2 °C/km (2 to 5 °F/1000 ft), as obtained from the International Civil Aviation Organization (ICAO). The environmental lapse rate is the decrease in temperature of air with altitude for a specific time and place (see below). It can be highly variable ...
the vertical pressure variation, which relates pressure, density and geopotential altitude (using a standard pressure of 101,325 pascals (14.696 psi) at mean sea level as a boundary condition): =, and. the ideal gas law in molar form, which relates pressure, density, and temperature:
These figures should be compared with the temperature and density of Earth's atmosphere plotted at NRLMSISE-00, which shows the air density dropping from 1200 g/m 3 at sea level to 0.125 g/m 3 at 70 km, a factor of 9600, indicating an average scale height of 70 / ln(9600) = 7.64 km, consistent with the indicated average air temperature over ...
Atmospheric thermodynamics is the study of heat-to-work transformations (and their reverse) that take place in the Earth's atmosphere and manifest as weather or climate. . Atmospheric thermodynamics use the laws of classical thermodynamics, to describe and explain such phenomena as the properties of moist air, the formation of clouds, atmospheric convection, boundary layer meteorology, and ...
The density altitude can also be considered to be the pressure altitude adjusted for a non-standard temperature. Both an increase in the temperature and a decrease in the atmospheric pressure , and, to a much lesser degree, an increase in the humidity , will cause an increase in the density altitude.