pyrad.proc.process_phidp_kdp_lp#

pyrad.proc.process_phidp_kdp_lp(procstatus, dscfg, radar_list=None)[source]#

Estimates PhiDP and KDP using a linear programming algorithm.

This method only retrieves data in rain (i.e. below the melting layer).

The method has 3 steps: PhiDP unfolding (including clutter suppression), Processing PhiDP using the LP algorithm, Obtaining KDP by convoluting PhiDP with a Sobel window.

Required inputs for the LP algorithm are PsiDP and reflectivity.

RhoHV and SNR are used for the clutter suppression in the PhiDP unfolding step (note that SNR is used instead of Normalized Coherent Power used by the original algorithm). If they are not provided a gate_filter based on the values of reflectivity is used instead.

Freezing level height can be retrieved from iso-0 or temperature fields, from radio sounding or set by the user.

Parameters:

procstatus (int) – Processing status: 0 initializing, 1 processing volume, 2 post-processing

dscfg (dictionary of dictionaries) –

data set configuration. Accepted Configuration Keywords:

datatype : list of string. Dataset keyword
    The input data types
fzl : float. Dataset keyword
    The freezing level height [m]. Default 2000.
sounding : str. Dataset keyword
    The nearest radiosounding WMO code (5 int digits). It will be used
    to compute the freezing level, if no temperature field name is
    specified, if the temperature field is not in the radar object or
    if no freezing_level is explicitely defined.
ml_thickness : float. Dataset keyword
    The melting layer thickness in meters. Default 700.
beamwidth : float. Dataset keyword
    the antenna beamwidth [deg]. If None that of the keys
    radar_beam_width_h or radar_beam_width_v in attribute
    instrument_parameters of the radar object will be used. If the key
    or the attribute are not present the beamwidth will be set to None
LP_solver : str.
    The LP solver to use. Can be pyglpk, cvxopt, cylp, cylp_mp.
    Default cvxopt
proc : int
    Number of worker processes. Only used when LP_solver is cylp_mp.
    Default 1
min_snr, min_rhv : float
    Minimum SNR and RhoHV. Used to filter out non-meteorological
    echoes when performing the unfolding of the differential phase.
    Default 10 and 0.6
sys_phase : float
    Default system differential phase offset in deg. Default 0.
overide_sys_phase : bool
    If True the dynamic sys_phase not computed and the default
    sys_phase is used. If false a dynamic sys_phase is computed. If
    no dynamic value is found the default sys_phase is used.
    Default False
first_gate_sysp : int
    First gate to use when determining the system differential phase
    offset. Default 0
nowrap : int or None
    Gate number where to begin the phase unwrapping. None will unwrap
    from gate 0. Default None
ncpts : int
    Minimum number of continuous valid PhiDP points. Segments below
    this number or starting at a gate below this number are going to
    be excluded from the unfolding. Default 2.
z_bias : float
    reflectivity bias. Default 0 dBZ
low_z, high_z : float
    mininum and maximum reflectivity values. Values beyond this range
    are going to be set to this range limits. The modified
    reflectivity is used in the LP algorithm. Default 10 and 53 dBZ
min_phidp : float
    minimum differential phase. PhiDP values below this threshold are
    going to be set to the threshold values. The modified PhiDP is
    used in the LP algorithm. Default 0.1 deg
doc : int
    Number of gates to doc at the end of the ray. Used in the LP
    algorithm. Default 0
self_const : float
    selfconsistency factor. Used in the LP algorithm. Default 60000
coef : float
    Exponent linking Z to KDP in selfconsistency. Used in the LP
    algorithm. kdp = (10**(0.1z))**coef. Default 0.914
window_len : int
    Length of Sobel Window applied to PhiDP field before computing
    KDP. Default 35

radar_list (list of Radar objects) – Optional. list of radar objects

Returns:

new_dataset (dict) – dictionary containing the output
ind_rad (int) – radar index