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CIRA-86 Atmosphere Model

Implement mathematical representation of 1986 CIRA atmosphere




The CIRA-86 Atmosphere Model block implements the mathematical representation of the 1986 Committee on Space Research (COSPAR) International Reference Atmosphere (CIRA). The block provides values for absolute temperature, pressure, density, and speed of sound for the input geopotential altitude.

The CIRA-86 Atmosphere Model block icon displays the input and output units selected from the Units list.



Specifies the input and output units:




Speed of Sound

Air Pressure

Air Density

Metric (MKS)



Meters per second


Kilograms per cubic meter

English (Velocity in ft/s)


Degrees Rankine

Feet per second

Pound-force per square inch

Slug per cubic foot

English (Velocity in kts)


Degrees Rankine


Pound-force per square inch

Slug per cubic foot

Coordinate type

Specify the representation of the coordinate type. The default is GPHeight.

  • Pressure

    Indicates pressure in pascal.

  • GPHeight

    Indicates geopotential height in meters.

Mean value type

Specify mean value types. The default is Monthly.

  • Monthly

    Indicates monthly values. If you select Monthly, you must also set the Month parameter.

  • Annual

    Indicates annual values. Valid when Coordinate type has a value of Pressure.


Indicates the month in which the mean values are taken. From the list, select the desired month. This parameter applies only when Mean value type has a value of Monthly.

Action for out-of-range input

Specify if out-of-range input invokes a warning, error, or no action.

Inputs and Outputs

InputDimension TypeDescription



Contains the latitude in degrees (limited to +/-80 degrees).



Contains an m array of either:

  • Geopotential heights in selected length units (Coordinate type is GPHeight)

  • Pressures in selected pressure units (Coordinate type is Pressure)

OutputDimension TypeDescription



Contains mean temperature in selected units.



Contains an m array of either:

  • Pressures in selected pressure units (Coordinate type is GPHeight)

  • Geopotential heights in selected length units (Coordinate type is Pressure)



Contains mean zonal winds in selected units.

Assumptions and Limitations

This function uses a corrected version of the CIRA data files provided by J. Barnett in July 1990 in ASCII format.

This function has the limitations of the CIRA 1986 model. The values for the CIRA 1986 model are limited to the regions of 80 degrees S to 80 degrees N on the Earth and geopotential heights of 0 to 120 kilometers. In each monthly mean data set, values at 80 degrees S for 101,300 pascal or 0 meters were omitted because these levels are within the Antarctic land mass. For zonal mean pressure in constant altitude coordinates, pressure data is not available below 20 kilometers. Therefore, this is the bottom level of the CIRA climatology.


Fleming, E. L., Chandra, S., Shoeberl, M. R., Barnett, J. J., Monthly Mean Global Climatology of Temperature, Wind, Geopotential Height and Pressure for 0-120 km, NASA TM100697, February 1988

Introduced in R2007b