#!/usr/bin/env python
# -*- coding: UTF-8 -*-
# Copyright (c) 2011-2023, wradlib developers.
# Distributed under the MIT License. See LICENSE.txt for more info.
"""
Data Transformation
^^^^^^^^^^^^^^^^^^^
Module <trafo> transforms data e.g. from RVP-units
to dBZ-values to Z-values and vice versa.
.. currentmodule:: wradlib.trafo
.. autosummary::
:nosignatures:
:toctree: generated/
{}
"""
__all__ = [
"rvp_to_dbz",
"decibel",
"idecibel",
"r_to_depth",
"kdp_to_r",
"si_to_kmh",
"si_to_mph",
"si_to_kts",
"kmh_to_si",
"mph_to_si",
"kts_to_si",
"KuBandToS",
"KuBandToX",
"SBandToKu",
"TrafoMethods",
]
__doc__ = __doc__.format("\n ".join(__all__))
from dataclasses import dataclass
import numpy as np
from wradlib import util
# CONSTANTS
meters_per_mile = 1609.344
meters_per_nautical_mile = 1852.0
[docs]@dataclass(init=False, repr=False, eq=False)
class SBandToKu:
"""Class to hold coefficients for Radar Reflectivity Conversion
From S-band (2.8GHz) to Ku-band (13.8GHz)
See :cite:`Liao2009` for reference.
"""
snow = np.array([0.185074, 1.01378, -0.00189212])
rain = np.array([-1.50393, 1.07274, 0.000165393])
[docs]@dataclass(init=False, repr=False, eq=False)
class KuBandToS:
"""Class to hold coefficients for Radar Reflectivity Conversion
From Ku-band (13.8 GHz) to S-band (2.8 GHz)
See :cite:`Cao2013` for reference.
"""
# Rain 90% 80% 70% 60% 50% 40% 30% 20% 10% Snow
snow = np.array(
[
[
4.78e-2,
4.12e-2,
8.12e-2,
1.59e-1,
2.87e-1,
4.93e-1,
8.16e-1,
1.31e0,
2.01e0,
2.82e0,
1.74e-1,
],
[
1.23e-2,
3.66e-3,
2.00e-3,
9.42e-4,
5.29e-4,
5.96e-4,
1.22e-3,
2.11e-3,
3.34e-3,
5.33e-3,
1.35e-2,
],
[
-3.50e-4,
1.17e-3,
1.04e-3,
8.16e-4,
6.59e-4,
5.85e-4,
6.13e-4,
7.01e-4,
8.24e-4,
1.01e-3,
-1.38e-3,
],
[
-3.30e-5,
-8.08e-5,
-6.44e-5,
-4.97e-5,
-4.15e-5,
-3.89e-5,
-4.15e-5,
-4.58e-5,
-5.06e-5,
-5.78e-5,
4.74e-5,
],
[
4.27e-7,
9.25e-7,
7.41e-7,
6.13e-7,
5.80e-7,
6.16e-7,
7.12e-7,
8.22e-7,
9.39e-7,
1.10e-6,
0.00e0,
],
]
)
# Rain 90% 80% 70% 60% 50% 40% 30% 20% 10% Hail
hail = np.array(
[
[
4.78e-2,
1.80e-1,
1.95e-1,
1.88e-1,
2.36e-1,
2.70e-1,
2.98e-1,
2.85e-1,
1.75e-1,
4.30e-2,
8.80e-2,
],
[
1.23e-2,
-3.73e-2,
-3.83e-2,
-3.29e-2,
-3.46e-2,
-2.94e-2,
-2.10e-2,
-9.96e-3,
-8.05e-3,
-8.27e-3,
5.39e-2,
],
[
-3.50e-4,
4.08e-3,
4.14e-3,
3.75e-3,
3.71e-3,
3.22e-3,
2.44e-3,
1.45e-3,
1.21e-3,
1.66e-3,
-2.99e-4,
],
[
-3.30e-5,
-1.59e-4,
-1.54e-4,
-1.39e-4,
-1.30e-4,
-1.12e-4,
-8.56e-5,
-5.33e-5,
-4.66e-5,
-7.19e-5,
1.90e-5,
],
[
4.27e-7,
1.59e-6,
1.51e-6,
1.37e-6,
1.29e-6,
1.15e-6,
9.40e-7,
6.71e-7,
6.33e-7,
9.52e-7,
0.00e0,
],
]
)
[docs]@dataclass(init=False, repr=False, eq=False)
class KuBandToX:
"""Class to hold coefficients for Radar Reflectivity Conversion
From Ku-band (13.8 GHz) to X-band (9.4 GHz)
See :cite:`Pejcic2022` for reference.
"""
# Rain Snow
snow = np.array(
[
[
1.91e-1,
-1.2e-1,
],
[
-7.83e-2,
6.8e-2,
],
[
1.12e-2,
-4.55e-3,
],
[
-6.17e-4,
1.18e-4,
],
[
1.25e-5,
-6.6e-7,
],
[
-8.43e-8,
0.0,
],
]
)
# Rain Hail
hail = np.array(
[
[
1.91e-1,
5.57e-2,
],
[
-7.83e-2,
1.8e-2,
],
[
1.12e-2,
1.91e-3,
],
[
-6.17e-4,
-6.64e-5,
],
[
1.25e-5,
8.18e-7,
],
[
-8.43e-8,
0.0,
],
]
)
[docs]def rvp_to_dbz(x):
"""Calculates dBZ-values from DWD RVP6 values as given in DX-product
files.
Parameters
----------
x : float or :class:`numpy:numpy.ndarray`
a number or an array
Examples
--------
>>> from wradlib.trafo import rvp_to_dbz
>>> print(rvp_to_dbz(65.))
0.0
"""
return x * 0.5 - 32.5
[docs]def decibel(x):
"""Calculates the decibel representation of the input values
:math:`dBZ=10 \\cdot \\log_{10} z`
Parameters
----------
x : float or :class:`numpy:numpy.ndarray`
(must not be <= 0.)
Examples
--------
>>> from wradlib.trafo import decibel
>>> print(decibel(100.))
20.0
"""
return 10.0 * np.log10(x)
[docs]def idecibel(x):
"""Calculates the inverse of input decibel values
:math:`z=10^{x \\over 10}`
Parameters
----------
x : float or :class:`numpy:numpy.ndarray`
Examples
--------
>>> from wradlib.trafo import idecibel
>>> print(idecibel(10.))
10.0
"""
return 10.0 ** (x / 10.0)
[docs]def r_to_depth(x, interval):
"""Computes rainfall depth (mm) from rainfall intensity (mm/h)
Parameters
----------
x : float or :class:`numpy:numpy.ndarray`
rainfall intensity in mm/h
interval : float
time interval (s) the values of `x` represent
Returns
-------
output : float or :class:`numpy:numpy.ndarray`
rainfall depth (mm)
"""
return x * interval / 3600.0
[docs]def kdp_to_r(kdp, f, a=129.0, b=0.85):
"""Estimating rainfall intensity directly from specific differential phase.
The general power law expression has been suggested by :cite:`Ryzhkov2005`.
The default parameters have been set according to :cite:`Bringi2001`.
Note
----
**Please note that this way, rainfall intensities can become negative.**
This is an intended behaviour in order to account for noisy :math:`K_{DP}`
values.
Parameters
----------
kdp : float or :class:`numpy:numpy.ndarray`
:math:`K_{DP}` as array of floats
f : float
radar frequency [GHz]
- Standard frequencies in X-band range between 8.0 and 12.0 GHz,
- Standard frequencies in C-band range between 4.0 and 8.0 GHz,
- Standard frequencies in S-band range between 2.0 and 4.0 GHz.
a : float
linear coefficient of the power law
b : float
exponent of the power law
Returns
-------
output : :class:`numpy:numpy.ndarray`
array of rainfall intensity
"""
return np.sign(kdp) * a * (np.abs(kdp) / f) ** b
[docs]def si_to_kmh(vals):
"""Conversion from SI wind speed units to km/hr.
Note
----
Code was migrated from https://github.com/nguy/PyRadarMet.
Parameters
----------
vals : float or :class:`numpy:numpy.ndarray`
Speed in SI units (m/s)
Returns
-------
output: float or :class:`numpy:numpy.ndarray`
Speed in km/hr
Examples
--------
>>> from wradlib.trafo import si_to_kmh
>>> print(si_to_kmh(1.))
3.6
"""
return vals * 3600.0 / 1000.0
[docs]def si_to_mph(vals):
"""Conversion from SI wind speed units to miles/hr
Note
----
Code was migrated from https://github.com/nguy/PyRadarMet.
Parameters
----------
vals : float or :class:`numpy:numpy.ndarray`
Speed in SI units (m/s)
Returns
-------
output: float or :class:`numpy:numpy.ndarray`
Speed in miles per hour
Examples
--------
>>> from wradlib.trafo import si_to_mph
>>> print(np.round(si_to_mph(1.), 3))
2.237
"""
return vals * 3600.0 / meters_per_mile
[docs]def si_to_kts(vals):
"""Conversion from SI wind speed units to knots
Note
----
Code was migrated from https://github.com/nguy/PyRadarMet.
Parameters
----------
vals : float or :class:`numpy:numpy.ndarray`
Speed in SI units (m/s)
Returns
-------
output: float or :class:`numpy:numpy.ndarray`
Speed in knots
Examples
--------
>>> from wradlib.trafo import si_to_kts
>>> print(np.round(si_to_kts(1.), 3))
1.944
"""
return vals * 3600.0 / meters_per_nautical_mile
[docs]def kmh_to_si(vals):
"""Conversion from km/hr to SI wind speed units
Note
----
Code was migrated from https://github.com/nguy/PyRadarMet.
Parameters
----------
vals: float or :class:`numpy:numpy.ndarray`
Wind speed in km/hr
Returns
-------
output: float or :class:`numpy:numpy.ndarray`
Wind speed in SI units (m/s)
Examples
--------
>>> from wradlib.trafo import kmh_to_si
>>> print(np.round(kmh_to_si(10.), 3))
2.778
"""
return vals * 1000.0 / 3600.0
[docs]def mph_to_si(vals):
"""Conversion from miles/hr to SI wind speed units
Note
----
Code was migrated from https://github.com/nguy/PyRadarMet.
Parameters
----------
vals: float or :class:`numpy:numpy.ndarray`
Wind speed in miles per hour
Returns
-------
output: float or :class:`numpy:numpy.ndarray`
Wind speed in SI units (m/s)
Examples
--------
>>> from wradlib.trafo import mph_to_si
>>> print(np.round(mph_to_si(10.), 2))
4.47
"""
return vals * meters_per_mile / 3600.0
[docs]def kts_to_si(vals):
"""Conversion from knots to SI wind speed units
Note
----
Code was migrated from https://github.com/nguy/PyRadarMet.
Parameters
----------
vals: float or :class:`numpy:numpy.ndarray`
Wind speed in knots
Returns
-------
output: float or :class:`numpy:numpy.ndarray`
Wind speed in SI units (m/s)
Examples
--------
>>> from wradlib.trafo import kts_to_si
>>> print(np.round(kts_to_si(1.), 3))
0.514
"""
return vals * meters_per_nautical_mile / 3600.0
[docs]class TrafoMethods(util.XarrayMethods):
"""wradlib xarray SubAccessor methods for DualPol."""
[docs] @util.docstring(decibel)
def decibel(self):
if not isinstance(self, TrafoMethods):
return self.pipe(decibel)
else:
return self._obj.pipe(decibel)
[docs] @util.docstring(idecibel)
def idecibel(self):
if not isinstance(self, TrafoMethods):
return self.pipe(idecibel)
else:
return self._obj.pipe(idecibel)
[docs] @util.docstring(r_to_depth)
def r_to_depth(self, *args, **kwargs):
if not isinstance(self, TrafoMethods):
return self.pipe(r_to_depth, *args, **kwargs)
else:
return self._obj.pipe(r_to_depth, *args, **kwargs)
if __name__ == "__main__":
print("wradlib: Calling module <trafo> as main...")
