refractiveidx

Calculates the refractive index

Since R2021a

Syntax

ridx = refractiveidx(h)

ridx = refractiveidx(___,Name,Value)

[ridx,N] = refractiveidx(___)

refractiveidx(___)

Description

ridx = refractiveidx(h) calculates the refractive index ridx at height h above mean sea level (MSL) using the International Telecommunication Union (ITU) standard atmospheric model.

ridx = refractiveidx(___,Name,Value) calculates the refractive index with additional options specified by one or more name-value pairs.

[ridx,N] = refractiveidx(___) additionally outputs the refractivity N as a row vector.

refractiveidx(___) with no output arguments plots the refractive index n as a function of altitude in kilometers.

Examples

Compute Refractive Index and Refractivity

Compute the refractive index and refractivity at a height of 20 km using the mid-latitude model during winter.

h = 20e3;

[ridx,N] = refractiveidx(h,'LatitudeModel','Mid','Season','Winter')

ridx = 
1.0000

N = 
21.1961

Input Arguments

h — Geometric heights

row vector

Geometric heights corresponding to the altitude above MSL in meters, specified as a row vector.

Data Types: double

Name-Value Arguments

Specify optional pairs of arguments as Name1=Value1,...,NameN=ValueN, where Name is the argument name and Value is the corresponding value. Name-value arguments must appear after other arguments, but the order of the pairs does not matter.

Before R2021a, use commas to separate each name and value, and enclose Name in quotes.

Example: refractiveidx(h,'LatitudeModel','Mid','Season','Winter') specifies the mid-latitude model during winter.

VaporDensity — Standard ground-level water-vapor density

7.5 (default) | scalar

Standard ground-level water-vapor density in g/m³, specified as a scalar. VaporDensity applies only when LatitudeModel is set to the default 'Standard' model.

Data Types: double

ScaleHeight — Scale height

2000 (default) | scalar

Scale height in meters, specified as a scalar. ScaleHeight applies only when LatitudeModel is set to the default 'Standard' model. For a dry atmosphere, set ScaleHeight to 6000.

Data Types: double

LatitudeModel — Reference latitude model

'Standard' (default) | string

Reference latitude model, specified as a string vector. Specify LatitudeModel as:

• 'Standard'

  This model is the Mean Annual Global Reference Atmosphere (MAGRA) that reflects the mean annual temperature and pressure averaged across the world.

• 'Low'

  Use this option for low latitudes less than 22°, where there exists little seasonal variation.

• 'Mid'

  Use this option for mid-latitudes between 22° and 45° that have seasonal profiles for summer and winter, which can be specified using the Season name-value pair.

• 'High'

  Use this option for high latitudes greater than 45° that have seasonal profiles for summer and winter, which can be specified using the Season name-value pair.

Season — Seasonal profile

'Summer' (default) | 'Winter'

Seasonal profile, specified as 'Summer' or 'Winter'. This argument is valid only when LatitudeModel is set to 'Mid' or 'High'.

AtmosphereMeasurements — Custom atmospheric measurements

N-by-4 matrix

Custom atmospheric measurements for the calculation of ridx, specified as an N-by-4 matrix where N corresponds to the number of altitude measurements. The first column in N is the atmospheric temperature in Kelvin, the second column is the atmospheric pressure in hectopascals, the third column is the atmospheric water-vapor density in g/m³, and the fourth column is the altitude above MSL of the measurements in increasing order and specified in meters. When AtmosphereMeasurements is specified, all other name-value pair options are ignored and ridx is applicable for the input height h.

Output Arguments

ridx — Refractive index

row vector

Refractive index, returned as a row vector.

N — Refractivity

row vector

Refractivity, returned as a row vector.

References

[1] International Telecommunication Union (ITU). "The Radio Refractive Index: Its Formula and Refractivity Data". Recommendation ITU-R P.453-11, P Series, Radiowave Propagation, July 2015.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.

Version History

Introduced in R2021a