Source code for radarx.fundamentals.variables
"""
Radar-Derived Variables
=======================
Functions related to reflectivity, differential reflectivity, and radial velocity.
.. autosummary::
:nosignatures:
:toctree: generated/
reflectivity_factor
differential_reflectivity
linear_depolarization_ratio
circular_depolarization_ratio
radial_velocity
References
----------
- Rinehart, R. E. (1997). Radar for Meteorologists.
- Doviak and Zrnic (1993). Doppler Radar and Weather Observations.
"""
import numpy as np
[docs]
def reflectivity_factor(p_return, radar_const, dielectric=0.93, range_m=1000.0):
"""
Compute reflectivity factor Z [mm^6/m^3].
Parameters
----------
p_return : float or array-like
Received power from target [W]
radar_const : float
Radar constant (unitless)
dielectric : float
Dielectric factor (default is 0.93 for water)
range_m : float or array-like
Range to target [m]
Returns
-------
float or array-like
Reflectivity factor Z [mm^6/m^3]
"""
return (
np.asarray(p_return) * np.asarray(range_m) ** 2 / (radar_const * dielectric**2)
)
[docs]
def differential_reflectivity(z_h, z_v):
"""
Compute differential reflectivity ZDR [dB].
Parameters
----------
z_h : float or array-like
Horizontal reflectivity [mm^6/m^3]
z_v : float or array-like
Vertical reflectivity [mm^6/m^3]
Returns
-------
float or array-like
ZDR in dB
"""
return 10.0 * np.log10(np.asarray(z_h) / np.asarray(z_v))
[docs]
def linear_depolarization_ratio(z_h, z_v):
"""
Compute linear depolarization ratio LDR [dB].
Parameters
----------
z_h : float or array-like
Horizontal reflectivity [mm^6/m^3]
z_v : float or array-like
Vertical reflectivity [mm^6/m^3]
Returns
-------
float or array-like
LDR in dB
"""
return 10.0 * np.log10(np.asarray(z_v) / np.asarray(z_h))
[docs]
def circular_depolarization_ratio(z_parallel, z_orthogonal):
"""
Compute circular depolarization ratio CDR [dB].
Parameters
----------
z_parallel : float or array-like
Power or reflectivity in the parallel channel [mm^6/m^3]
z_orthogonal : float or array-like
Power or reflectivity in the orthogonal channel [mm^6/m^3]
Returns
-------
float or array-like
CDR in dB
"""
return 10.0 * np.log10(np.asarray(z_parallel) / np.asarray(z_orthogonal))
[docs]
def radial_velocity(f_shift, wavelength):
"""
Compute radial velocity from Doppler frequency shift.
Parameters
----------
f_shift : float or array-like
Doppler frequency shift [Hz]
wavelength : float
Radar wavelength [m]
Returns
-------
float or array-like
Radial velocity [m/s]
"""
return np.asarray(f_shift) * np.asarray(wavelength) / 2.0
__all__ = [
"reflectivity_factor",
"differential_reflectivity",
"linear_depolarization_ratio",
"circular_depolarization_ratio",
"radial_velocity",
]
