Revision 956ba1fa7f45bd3b699b5e52fc6d96db33d5fe0b authored by Thomas Pfaff on 10 January 2014, 10:14:52 UTC, committed by Thomas Pfaff on 10 January 2014, 10:14:52 UTC
- fully interpret and return the header information - read only the amount of data indicated by the header regardless of file size - remove static truncation to 128 range bins
1 parent 0d5c87d
trafo.py
#-------------------------------------------------------------------------------
# Name: trafo
# Purpose:
#
# Authors: Maik Heistermann, Stephan Jacobi and Thomas Pfaff
#
# Created: 26.10.2011
# Copyright: (c) Maik Heistermann, Stephan Jacobi and Thomas Pfaff 2011
# Licence: The MIT License
#-------------------------------------------------------------------------------
#!/usr/bin/env python
"""
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/
rvp2dBZ
decibel
idecibel
r2depth
kdp2r
"""
import numpy as np
def rvp2dBZ(x):
"""Calculates dBZ-values from DWD RVP6 values as given in DX-product
files.
Parameters
----------
x : a number or an array
"""
return x*0.5-32.5
def decibel(x):
"""Calculates the decibel representation of the input values
dBZ = 10*log10(z)
Parameters
----------
x : a number or an array (must not be <= 0.)
"""
return 10.*np.log10(x)
def idecibel(x):
"""Calculates the inverse of input decibel values
10.**(x/10.)
Parameters
----------
x : a number or an array
"""
return 10.**(x/10.)
def r2depth(x, interval):
"""
Computes rainfall depth (mm) from rainfall intensity (mm/h)
Parameters
----------
x : float or array of float
rainfall intensity in mm/h
interval : number
time interval (s) the values of `x` represent
Returns
-------
output : float or array of float
rainfall depth (mm)
"""
return x * interval / 3600.
def kdp2r(kdp, f, a=129., b=0.85):
"""Estimating rainfall intensity directly from specific differential phase.
The general power law expression has been suggested by [Ryzhkov2005]_.
The default parameters have been set according to [BringiChandrasekar2001]_.
**Please note that this way, rainfall intensities can become negative.** This is
an intended behaviour in order to account for noisy Kdp values.
Parameters
----------
kdp : Kdp as array of floats
f : 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 : linear coefficient of the power law
b : exponent of the power law
Returns
-------
output : array of rainfall intensity
References
----------
.. [BringiChandrasekar2001] Bringi, V. N., and V. Chandrasekar, 2001:
Polarimetric Doppler Weather Radar. Cambridge University Press, 636 pp.
.. [Ryzhkov2005] Ryzhkov, A. V., S. Giangrande, and T. J. Schuur, 2005: Rainfall
estimation with a polarimetric prototype of WSR-88D. J. Appl. Meteor., 44, 502-515.
"""
return np.sign(kdp) * a * (np.abs(kdp) / f)**b
if __name__ == '__main__':
print 'wradlib: Calling module <trafo> as main...'
Computing file changes ...
