Engee documentation

Lapse Rate Model

Computation of atmospheric parameters through the temperature gradient.

lapse rate model

Description

The Lapse Rate Model block implements formulas to calculate the parameters of a standard atmosphere: temperature, sound speed, pressure and air density.

Formulas for calculating troposphere parameters:

β

Formulas for calculating the tropopause parameters (beginning of the stratosphere):

β

Where:

  • - temperature at mean sea level, K;

  • - air density at mean sea level, kg/m³;

  • - pressure at mean sea level, Pa;

  • - geopotential height, m;

  • - troposphere height, m

  • - temperature at altitude , K

  • - air density at altitude , kg/m3;

  • - pressure at altitude , Pa

  • - sound speed at height , m/s;

  • - temperature gradient over geopotential height, K/m;

  • - specific gas constant, J/kg⋅K;

  • - adiabatic index;

  • - free fall acceleration, m/s2.

The Lapse Rate Model block works in SI units.

Limitations

  • Below a height of 0 m and above the tropopause height, temperature and pressure values remain unchanged.

  • The density and speed of sound are calculated using the ideal gas equation.

Ports

Inlet

h (m) - geopotential height
scalar | vector

Geopotential height, m.

Data types: Float64.

Output

T (K) - temperature
scalar | vector

Temperature, K.

Data types: Float64.

a (m/s) - speed of sound
scalar | vector

Speed of sound, m/s.

Data types: Float64.

P (Pa) - pressure
scalar | vector

Pressure, Pa.

Data types: Float64.

ρ (kg/m3) - air density
scalar | vector

Density of air, kg/m³.

Data types: Float64.

Parameters

Acceleration due to gravity (m/s^2) - free fall acceleration
9.80665 (by default) | scalar

Free-fall acceleration, m/s2. By default, the value of free fall acceleration at mean sea level is used.

Ratio of specific heats - adiabatic index
1.4 (By default) | scalar.

Adiabatic index.

Characteristic gas constant (J/Kg/K) - specific gas constant
287.0531 (By default) | scalar

Specific gas constant, J/kg⋅K.

Lapse rate (K/m) - temperature gradient
0.0065 (By default) | scalar

Temperature gradient along geopotential height, K/m.

Height of troposphere (m) - height of troposphere
11000.0 (By default) | scalar

Height of troposphere, m.

Height of tropopause (m) - height of tropopause
20000.0 (By default) | scalar

Height of tropopause, m.

Air density at mean sea level (Kg/m^3) - air density at mean sea level
1.225 (By default) | scalar

Air density at mean sea level, kg/m3.

Ambient pressure at mean sea level (N/m^2) - pressure at mean sea level
101325.0 (By default) | scalar

Pressure at mean sea level, N/m2 (Pa).

Ambient temperature at mean sea level (K) - temperature at mean sea level
288.15 (By default) | scalar.

Ambient temperature at mean sea level, K.

Lowest altitude (m) - lowest layer height
0.0 (By default) | scalar

The height corresponding to the beginning of the layer, m. The value must be less than the height of the tropopause.