Recommendation ITU-R P.835¶

This Recommendation provides expressions and data for reference standard atmospheres required for the calculation of gaseous attenuation on Earth-space paths.

Title	PDF	Latest approved in
Recommendation ITU-R P.835	[PDF]	2017-12
Reference standard atmospheres
Current recommendation version (In force)		Date
Recommendation ITU-R P.835-6	[PDF]	12/2017
Recommendations implemented in ITU-Rpy		Date
Recommendation ITU-R P.835-6	[PDF]	12/2017
Recommendation ITU-R P.835-5	[PDF]	02/2012
Recommendations not implemented in ITU-Rpy		Date
Recommendation ITU-R P.835-4	[PDF]	03/2005
Recommendation ITU-R P.835-3	[PDF]	10/1999
Recommendation ITU-R P.835-2	[PDF]	08/1997
Recommendation ITU-R P.835-1	[PDF]	08/1994

Introduction¶

This recommendation provides the equations to determine the temperature, pressure and water-vapour pressure as a function of altitude, as described in the U.S. Standard Atmosphere 1976. These values should be used for calculating gaseous attenuation when more reliable local data are not available.

Module description¶

itur.models.itu835.change_version(new_version)[source]¶

Change the version of the ITU-R P.835 recommendation currently being used.

This function changes the model used for the ITU-R P.835 recommendation to a different version.

Parameters:

new_version (int) –

Number of the version to use. Valid values are:

6: Activates recommendation ITU-R P.835-6 (12/17) (Current version)

5: Activates recommendation ITU-R P.835-5 (02/12) (Superseded)

itur.models.itu835.get_version()[source]¶

The version of the model currently in use for the ITU-R P.835 recommendation.

Obtain the version of the ITU-R P.835 recommendation currently being used.

Returns:	version – The version of the ITU-R P.835 recommendation being used.
Return type:	int

itur.models.itu835.temperature(lat, h, season='summer')[source]¶

Determine the temperature at a given latitude and height.

Method to determine the temperature as a function of altitude and latitude, for calculating gaseous attenuation along an Earth-space path. This method is recommended when more reliable local data are not available.

Parameters:	lat (number, sequence, or numpy.ndarray) – Latitudes of the receiver points h (number or Quantity) – Height (km) season (string) – Season of the year (available values, ‘summer’, and ‘winter’). Default ‘summer’
Returns:	T – Temperature (K)
Return type:	Quantity

References

[1] Reference Standard Atmospheres https://www.itu.int/rec/R-REC-P.835/en

itur.models.itu835.pressure(lat, h, season='summer')[source]¶

Determine the atmospheric pressure at a given latitude and height.

Method to determine the pressure as a function of altitude and latitude, for calculating gaseous attenuation along an Earth-space path. This method is recommended when more reliable local data are not available.

Parameters:	lat (number, sequence, or numpy.ndarray) – Latitudes of the receiver points h (number or Quantity) – Height (km) season (string) – Season of the year (available values, ‘summer’, and ‘winter’). Default ‘summer’
Returns:	P – Pressure (hPa)
Return type:	Quantity

References

[1] Reference Standard Atmospheres https://www.itu.int/rec/R-REC-P.835/en

itur.models.itu835.water_vapour_density(lat, h, season='summer')[source]¶

Determine the water vapour density at a given latitude and height.

Method to determine the water-vapour density as a function of altitude and latitude, for calculating gaseous attenuation along an Earth-space path. This method is recommended when more reliable local data are not available.

Parameters:	lat (number, sequence, or numpy.ndarray) – Latitudes of the receiver points h (number or Quantity) – Height (km) season (string) – Season of the year (available values, ‘summer’, and ‘winter’). Default ‘summer’
Returns:	rho – Water vapour density (g/m^3)
Return type:	Quantity

References

[1] Reference Standard Atmospheres https://www.itu.int/rec/R-REC-P.835/en

itur.models.itu835.standard_temperature(h, T_0=288.15)[source]¶

Determine the standard temperature at a given height.

Method to compute the temperature of an standard atmosphere at a given height. The reference standard atmosphere is based on the United States Standard Atmosphere, 1976, in which the atmosphere is divided into seven successive layers showing linear variation with temperature.

Parameters:	h (number or Quantity) – Height (km) T_0 (number or Quantity) – Surface temperature (K)
Returns:	T – Temperature (K)
Return type:	Quantity

References

[1] Reference Standard Atmospheres https://www.itu.int/rec/R-REC-P.835/en

itur.models.itu835.standard_pressure(h, T_0=288.15, P_0=1013.25)[source]¶

Determine the standard pressure at a given height.

Method to compute the total atmopsheric pressure of an standard atmosphere at a given height.

The reference standard atmosphere is based on the United States Standard Atmosphere, 1976, in which the atmosphere is divided into seven successive layers showing linear variation with temperature.

Parameters:	h (number or Quantity) – Height (km) T_0 (number or Quantity) – Surface temperature (K) P_0 (number or Quantity) – Surface pressure (hPa)
Returns:	P – Pressure (hPa)
Return type:	Quantity

References

[1] Reference Standard Atmospheres https://www.itu.int/rec/R-REC-P.835/en

itur.models.itu835.standard_water_vapour_density(h, h_0=2, rho_0=7.5)[source]¶

Determine the standard water vapour density at a given height.

The reference standard atmosphere is based on the United States Standard Atmosphere, 1976, in which the atmosphere is divided into seven successive layers showing linear variation with temperature.

Parameters:	h (number or Quantity) – Height (km) h_0 (number or Quantity) – Scale height (km) rho_0 (number or Quantity) – Surface water vapour density (g/m^3)
Returns:	rho – Water vapour density (g/m^3)
Return type:	Quantity

References

[1] Reference Standard Atmospheres https://www.itu.int/rec/R-REC-P.835/en

itur.models.itu835.standard_water_vapour_pressure(h, h_0=2, rho_0=7.5)[source]¶

Determine the standard water vapour pressure at a given height.

The reference standard atmosphere is based on the United States Standard Atmosphere, 1976, in which the atmosphere is divided into seven successive layers showing linear variation with temperature.

Parameters:	h (number or Quantity) – Height (km) h_0 (number or Quantity) – Scale height (km) rho_0 (number or Quantity) – Surface water vapour density (g/m^3)
Returns:	e – Water vapour pressure (hPa)
Return type:	Quantity

References

[1] Reference Standard Atmospheres https://www.itu.int/rec/R-REC-P.835/en