A Standard Atmosphere is a hypothetical vertical distribution of atmospheric temperature, pressure, and density that is roughly representative of year-round, midlatitude conditions. Typical uses are to serve as a basis for pressure altimeter calibrations, aircraft performance calculations, aircraft and rocket design, ballistic tables, meteorological diagrams, and various types of atmospheric modeling. The air is assumed to be dry and to obey the perfect gas law and the hydrostatic equation which, taken together, relate temperature, pressure, and density with vertical position. The atmosphere is considered to rotate with the Earth and to be an average over the diurnal cycle, the semiannual variation, and the range from active to quiet geomagnetic and sunspot conditions.
The U.S. Standard Atmosphere (1976) is an idealized, steady-state representation of mean annual conditions of the Earth’s atmosphere from the surface to 1000 km at latitude 45° N, as it is assumed to exist during a period with moderate solar activity. The defining meteorological elements are sea-level temperature and pressure and a temperature-height profile to 1000 km. The 1976 Standard Atmosphere uses the following sea-level values that have been standard for many decades:
The parameters included in this condensed version of the U.S. Standard Atmosphere are given in Table 2. Column definitions for Table 2 are as follows.
Column heading | Definition |
Z | Height (geometric) above mean sea level, in meters |
T | Temperature, in K |
P | Pressure, in Pa (1 Pa = 0.01 millibars) |
ρ | Density, in kg m-3, (1 kg m-3 = 1 g L-1) |
n | Number density, in molecules m-3 |
ν | Mean collision frequency, in collisions s-1 |
l | Mean free path, in m |
η | Absolute viscosity, in Pa s (1 Pa s = 1000 cP) |
k | Thermal conductivity, in W m-1 K-1 |
vs | Speed of sound, m s-1 |
g | Acceleration of gravity, in m s-2 |
The sea-level composition (percent by volume) is taken to be:
The T and P columns for the troposphere and lower stratosphere were generated from the following formulas as given in Table 1.
Height | T/K | P/Pa |
H ≤ 11000 m | 288.15 – 0.0065 H | 101325(288.15/T)–5.25577 |
11000 m < H ≤ 20000 m | 216.65 | 22632 e–0.00015768832(H–11000) |
20000 m < H < 32000 m | 216.65 + 0.0010(H–20000) | 5474.87(216.65/T)34.16319 |
In Table 1, H = rZ/(r + Z) is the geopotential height in meters and r is the mean Earth radius at 45° N latitude, taken as 6356766 m. For altitudes up to 32 km, ρ = 0.003483677(P/T) in the units used here. Formulas for the other quantities may be found in the references.
Z/m | T/K | P/Pa | ρ/kg m–3 | n/m–3 | ν/s–1 | l/m | η/Pa s | k/W m–1 K–1 | vs/m s–1 | g/m s–2 |
Continued on next page... | ||||||||||
–5000 | 320.68 | 1.778E+05 | 1.931 | 4.015E+25 | 1.151E+10 | 4.208E–08 | 1.942E–05 | 0.02788 | 359.0 | 9.822 |
–4500 | 317.42 | 1.685E+05 | 1.849 | 3.845E+25 | 1.096E+10 | 4.395E–08 | 1.927E–05 | 0.02763 | 357.2 | 9.830 |
–4000 | 314.17 | 1.596E+05 | 1.770 | 3.680E+25 | 1.044E+10 | 4.592E–08 | 1.912E–05 | 0.02738 | 355.3 | 9.819 |
–3500 | 310.91 | 1.511E+05 | 1.693 | 3.520E+25 | 9.933E+09 | 4.800E–08 | 1.897E–05 | 0.02713 | 353.5 | 9.818 |
–3000 | 307.66 | 1.430E+05 | 1.619 | 3.366E+25 | 9.448E+09 | 5.019E–08 | 1.882E–05 | 0.02688 | 351.6 | 9.816 |
–2500 | 304.41 | 1.352E+05 | 1.547 | 3.217E+25 | 8.982E+09 | 5.252E–08 | 1.867E–05 | 0.02663 | 349.8 | 9.814 |
–2000 | 301.15 | 1.278E+05 | 1.478 | 3.102E+25 | 8.623E+09 | 5.447E–08 | 1.852E–05 | 0.02638 | 347.9 | 9.813 |
–1500 | 297.90 | 1.207E+05 | 1.411 | 2.935E+25 | 8.106E+09 | 5.757E–08 | 1.836E–05 | 0.02613 | 346.0 | 9.811 |
–1000 | 294.65 | 1.139E+05 | 1.347 | 2.801E+25 | 7.693E+09 | 6.032E–08 | 1.821E–05 | 0.02587 | 344.1 | 9.810 |
–500 | 291.40 | 1.075E+05 | 1.285 | 2.672E+25 | 7.298E+09 | 6.324E–08 | 1.805E–05 | 0.02562 | 342.2 | 9.808 |
0 | 288.15 | 1.013E+05 | 1.225 | 2.547E+25 | 6.919E+09 | 6.633E–08 | 1.789E–05 | 0.02533 | 340.3 | 9.807 |
500 | 284.90 | 9.546E+04 | 1.167 | 2.427E+25 | 6.556E+09 | 6.961E–08 | 1.774E–05 | 0.02511 | 338.4 | 9.805 |
1000 | 281.65 | 8.988E+04 | 1.112 | 2.311E+25 | 6.208E+09 | 7.310E–08 | 1.758E–05 | 0.02485 | 336.4 | 9.804 |
1500 | 278.40 | 8.456E+04 | 1.058 | 2.200E+25 | 5.874E+09 | 7.680E–08 | 1.742E–05 | 0.02459 | 334.5 | 9.802 |
2000 | 275.15 | 7.950E+04 | 1.007 | 2.093E+25 | 5.555E+09 | 8.073E–08 | 1.726E–05 | 0.02433 | 332.5 | 9.801 |
2500 | 271.91 | 7.469E+04 | 0.957 | 1.990E+25 | 5.250E+09 | 8.491E–08 | 1.710E–05 | 0.02407 | 330.6 | 9.799 |
3000 | 268.66 | 7.012E+04 | 0.909 | 1.891E+25 | 4.959E+09 | 8.937E–08 | 1.694E–05 | 0.02381 | 328.6 | 9.797 |
3500 | 265.41 | 6.579E+04 | 0.863 | 1.795E+25 | 4.680E+09 | 9.411E–08 | 1.678E–05 | 0.02355 | 326.6 | 9.796 |
4000 | 262.17 | 6.166E+04 | 0.819 | 1.704E+25 | 4.414E+09 | 9.917E–08 | 1.661E–05 | 0.02329 | 324.6 | 9.794 |