Mp — processing options

In the Mp menu, you can configure the processing options.

Allow continuous sizes for power spectra: YES

The power spectra computed within RVP10 are normally not constrained to be powers of two in length. Answer NO to this question to reapply the constraint to mimic the behavior of older processors.

Spectrum width

R2 Processing Algorithms – 0:Never , 1:User, 2:Always : 1

This question controls whether R0/R1/R2 or R0/R1 estimates are used to compute the spectrum width (see Spectrum width algorithms and Setup operating parameters (SOPRM)):

  • Select 0 to unconditionally disable the R2 algorithms, regardless of what the host computer requests in the SOPRM command.
  • Select 2 to unconditionally enable R2 processing. Bit-7 of SOPRM word #2 is the host computer's interface to this function when the 1:User case is selected.
  • IRIS radar application uploads R0/R1/R2.

Ascope uploads the R2 algorithms button setting in the block Gen Setup. When IRIS Radar is the controlling host, the User setting is defined in the IRIS Ingest Setup menu. For more information, see IRIS and RDA Utilities Guide (M211316EN).

Clutter microsuppression

Clutter MicroSuppression – 0:Never , 1:User, 2:Always : 1

This parameter controls whether cluttery bins are rejected before being averaged in range. Bit-8 of SOPRM word #2 is the host computer's interface to this function when the 1:User case is selected (see Setup operating parameters (SOPRM)). The functionality is dependent on the application settings for CCOR thresholds, in addition (see Range averaging and clutter microsuppression).

IRIS requests clutter microsuppression. Ascope uploads the Clutter Microsuppression button setting in the block Gen Setup.

Autocorrelation

PPP  autocorels from FFTs – 0:Never , 1:User, 2:Always : 1

When autocorrelation terms are computed from power spectra, the results differ from a strict time-domain calculation in that an “end-around” term is introduced as a result of circular rather than linear convolution.

Requesting PPP-style autocorrelations correct this spurious term when the computations are done through FFTs. Bit-11 of SOPRM word #10 is the host computer's interface to this function when the 1:User case is selected (see Setup operating parameters (SOPRM)). IRIS does not request PPP-style autocorrelations, but Ascope requests it.

Velocity and processing algorithms

Unfold Velocity ( Vh – Vl ) – 0:Never , 1:User, 2:Always : 0

The Unfold Velocity parameter allows you to choose whether RVP10 unfolds velocities using a (Vhigh– Vlow) algorithm, instead of the improved algorithm described in Dual PRF velocity unfolding. Bit– 11 of SOPRM word #10 is the host computer's interface to this function when the "1:User" case is selected (see Setup operating parameters (SOPRM)).

Process w/ custom trigs – 0:Never , 1:User, 2:Always : 0

The Process w/ custom trigs parameter allows you to choose whether RVP10 attempts to run its standard processing algorithms even when a custom trigger pattern has been selected through the SETPWF command. Usually, this is not recommended, so the default setting is 0:Never. Bit–12 of SOPRM word #10 is the host computer's interface to this function when the 0:Never option is selected (see Setup operating parameters (SOPRM)).

Dual-polarization attenuation correction

DualPol Atten Correction -  0:Never, 1:User, 2:Always : 1

The question DualPol Atten Correction defines when RVP10 applies attenuation correction based on the integration of differential phase. Answer 0:Never to never apply the correction, 2:Always to always apply the correction, or 1:User for this to be defined by the controlling host. For more information, see Dual-polarimetric attenuation correction.

Additional SNR

Use High–SNR 16–bit packed timeseries format: Yes

This parameter provides an additional 6 dB of SNR. The parameter can be disabled to provide compatibility with legacy systems.

Free-running rays

Minimum freerunning ray holdoff : 100% of dwell

Limits: 0 ... 100%

This parameter controls the rate at which the RVP10 processes free-running rays. This prevents rays from being produced at the full CPU limit or I/O limit of the processor (whichever was slower), which could result in highly overlapping data being output at an unusably fast rate. This behavior only occurs when running without angle syncing, such as during IRIS manual and RHI scans.

To make these free-running modes more useful, you can establish a minimum hold-off between successive rays, expressed as a percentage of the number of pulses contributing to each ray:

  • 100% (default) produces rays whose input data do not overlap at all, that is, whose rate is exactly the PRF divided by the sample size.
  • 0% gives the unregulated behavior in which no minimum overlap is enforced and rays can be quickly produced.

Amplitude correction

Apply amplitude correction based on Burst/COHO: YES
 Time constant of mean amplitude estimator: 70 pulses

Limits: 10 pulses ... 500 pulses

RVP10 can perform pulse-to-pulse amplitude correction of the digital (I,Q) data stream based on the amplitude of the Burst/STALO input. See Amplitude correction for Tx power fluctuations.

Interface filter and unfolding

RVP10 can apply an interference filter to remove impulsive-type noise from the demodulated (I,Q) data stream. See Interference filter.

Interference Filter 0:None , Alg.1, Alg.2, Alg.3: 
Provide WSR88D legacy BATCH major mode: YES
  Maximum range to unfold: 600.0 km 
  Low–PRF bins range averaged on each side: 2 
  Low-PRF increased noise threshold margin: 0.00 dB
  Overlay power – Refl :5.0 dB Vel:8.0 dB Width:12.0 db
  LowSamps  = ( 0.00000 x  HiSamps ) + 6.00 : 
    LowPRF = ( 0.00000 x HiPRF ) + 250.00 :

This is a general implementation of a Lo/Hi Surveillance/Doppler PRF unfolding scheme that provides the legacy features as special cases. The parameters are defined as follows:

  • The parameter maximum range to unfold (in km) allows you to set an upper bound on how many Doppler trips unfold according to the echoes seen in the surveillance data.
  • The surveillance data set uses very few pulses and is somewhat noisy. You can choose the number of bins that are range averaged from both sides of these bins to provide a lower variance power estimate. A value of 0 means No averaging, a value of 1 averages 3 points, and so on.
  • The unfolding algorithm flags obscured range bins according to three different power thresholds for reflectivity, velocity, and width, and outputs these bits in the DB_FLAGS data parameter. Each threshold is specified in decibels.
  • The fundamental RVP10 operating parameters (such as PRF and Sample Size) apply to the high PRF portion of the BATCH trigger waveform. The low PRF rate and sample size are derived from these high values using a slope and offset. In the example, the slopes are both 0, so that the surveillance data is fixed at 6-pulses and 250 Hz. Making the slopes non-zero would cause the low-PRF parameters to vary automatically if desired.

These setup parameters are accessible through the DSP driver using the entry points dspw_batchSetup() and dspw_batchSetup(). These use the custom opcode that is defined separately by each major mode. The customUserOpcode_batch() is a useful model building these entry points.

Standard parameters in multi-polarization systems

T/Z/V/W computed from: H– Xmt :YES  V– Xmt:NO

This parameter controls how the standard parameters (Total Reflectivity T, Corrected Reflectivity Z, Velocity V, and Width W) are computed in a multiple-polarization system. Applying YES with H-Xmt or V-Xmt means that data from those transmit polarizations is used when there is more than one choice available. These selections only apply to the Alternating and Simultaneous transmit modes. 

Polarimetric Power Params –  NoiseCorrected:YES 
 Polarimetric Correlations –  NoiseCorrected:YES

These configurations specify whether noise correction is applied to dual-polarization measurements.

You can configure the sign and offset corrections to correct for intervening weather attenuation. It uses the change of angle in DP. The tuning numbers are taken from the dualpol.conf file.

PhiDP - Negate: NO ,  Offset:90.0 deg

The 2-bit PhiDP datatype has a range of 360 degrees. The question PhiDP - Negate: NO , Offset:90.0 deg allows setting an offset so that the initial PhiDP values being measured by the radar system starts in the lower end of the data range format. Vaisala recommends setting the offset so that the initial PhiDP values are near 10 degrees of value. The negate option may be flipped if PhiDP values are decreasing in range instead of increasing.

KDP computation – 0 :LSQ, 1:Weighted LSQ, 2:Cubic Splines

Select the Kdp computation:

LSQ
Least square fit to a linear function.
Weighted LSQ
Weighted least square fit to a linear function. FIR filter coefficients are used as weights.
Cubic Splines
Smoothing and numerical derivatives calculation using a CSU’s Adaptive estimation of specific differential phase algorithm.

For LSQ Kdp computation, select the length:

KDP – LSQ  Weights(FIR) Width: 4.00 km

For Cubic Splines Kdp computation: Smoothing factor for the first, non– adaptive, stage of cubic splines processing followed by the smoothing factor for the second, adaptive, stage of the cubic splines processing.

A typical installation uses H-Xmt:YES, V-Xmt:No. Including both transmissions decreases the variance of (T/Z/V/W), but most researchers prefer excluding V-Xmt because that is more standard in the literature.

Melting height

Melting height: 3000 meters

The melting height is used in HydroClass calculations and is recorded with the data.

This is the height above the radar, so must include the altitude of the radar when computing. Normally this is set automatically by the controlling application.

Noise correction

Enable noise power based correction of Z0: No

If the noise correction is set to Yes, RVP10 adjusts the calibration reflectivity value Z0 when the current noise level changes from the level measured when the calibration was done.

See Noise correction to reflectivity calibration.