# rainreflectivity

Volume reflectivity of rain

## Description

example

volrefl = rainreflectivity(freq,rr) returns the volume reflectivity of rain, computed using the Marshall-Palmer Model.

volrefl = rainreflectivity(freq,rr,pol) specifies the polarization of the transmitted and received waves.

## Examples

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Estimate the rain volume reflectivity of a side-looking airborne SAR operating in the L band at 1.5 GHz for rain rates of 0.25 mm/hr, 1 mm/hr, 4 mm/hr, and 16 mm/Hr.

f = 1.5e9;
rr = [0.25 1 4 16];

Compute the rain volume reflectivity.

volref = rainreflectivity(f,rr);

Plot the rain volume reflectivity as a function of the rain rate.

semilogx(rr,volref,'.-')
xlabel('Rain Rate (mm/hr)')
ylabel('Volume Reflectivity (dB/m)')

## Input Arguments

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Radar frequency in hertz, specified as a positive real scalar or a vector.

Data Types: double

Rain rate in millimeters per hour, specified as a real scalar or a vector.

Data Types: double

Polarization of transmitted and received waves, specified as one of these.

'HH'Horizontal polarizationHorizontal polarization
'HV'Horizontal polarizationVertical polarization
'VV'Vertical polarizationVertical polarization
'VH'Vertical polarizationHorizontal polarization
'RCPRCP'Right-hand circular polarizationRight-hand circular polarization
'RCPLCP'Right-hand circular polarizationLeft-hand circular polarization
'LCPLCP'Left-hand circular polarizationLeft-hand circular polarization
'LR'Left-hand polarizationRight-hand polarization
'HRCP'Horizontal polarizationRight-hand circular polarization
'VLCP'Vertical polarizationLeft-hand circular polarization
'RCPV'Right-hand circular polarizationVertical polarization
'LCPH'Left-hand circular polarizationHorizontal polarization

Data Types: char | string

## Output Arguments

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Volume reflectivity (radar cross-section per unit volume) of rain in square meters per cubic meter, returned as a matrix. The rows of volref correspond to the radar frequency values in freq. The columns of volref correspond to the rain rate values in rr.

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### Marshall-Palmer Model

The rain clutter reflectivity is computed based on the commonly used Marshall-Palmer drop-size distribution model. The model assumes raindrops are generally small with respect to the wavelength and are nearly spherical, indicating Rayleigh scattering.

The Marshall-Palmer model matches experimental results with measured data up to the Ka-band. Additionally, rain is not a static target, and exhibits its own motion spectrum. The motion spectrum is typically centered at some velocity with a recognizable velocity bandwidth. Data suggests a velocity bandwidth sometimes as high as 8 m/s, with a median velocity bandwidth of about 4 m/s.

## Version History

Introduced in R2021a