Zdrcal Configuration File

Version Information

Do not modify the version information at the start of the Zdrcal configuration file.

The default technical settings for Zdrcal logging at $IRIS_LOG/zdrcal.log are recommended, particularly in the introductory phase.

Note that the Zdrcal utility appends consecutive run logs in zdrcal.log. In longer runs, it is recommended to rename the log file from time to time.

# ZDRCAL version. Log settings
zdrcal.sVersion = "8.12"
zdrcal.sLogToFile = "YES"
zdrcal.sLogToTerm = "NO"

Threshold for ZDR Offset Warning

The primary configurable parameter of Zdrcal is the threshold for user warning about a significant deviation of the observed ZDR offset from the current radar setting. The max time span prevents Zdrcal accumulating data unreasonably long.

In field tests, the utility analysis has been found robust up to several days of integration (hourly sampling).

# Threshold for ZDR offset warning (dB).
zdrcal.fThresholdForAlarm_dB = 0.3

# ZDRCAL run duration will be adjusted, accordingly,
# in order to keep false alarm rates below 5% (ZDRCAL_FAR_CL).
# ZDRCAL run will be limited to a max time span (hours), however.

zdrcal.fMaxTimeSpan_hours = 96

Task Parameters

The relevant Zdrcal task parameters are configurable.

With all the radar task settings, keep within the site specific hardware limitations, listed in the Setup menu, RVP section.

The maximum number of sweeps is limited to 40 in IRIS/RDA, in addition.

During the first try, adjust the quality thresholds LOG, CCR, SQI, SIG to be adjusted similar to the typical operational task settings, while they can be tuned tighter for optimal quality, or relaxed modestly for optimal result availability.

The data fields in zdrcal RAW products are thresholded with the configure settings.

# Pulse width index, referring to the PWs specified in
setup_dsp.conf.
zdrcal.Task.iPW = 0

# Pulse repetition frequency (Hz).
zdrcal.Task.fPrfHz = 1200

# Range of the first gate, range spacing, and max gate range in
signal processing (km).
zdrcal.Task.fRangeStartKM = 0.1
zdrcal.Task.fRangeStepKM = 0.1
zdrcal.Task.fMaxRangeKM = 10

# Number of complete antenna rotations.
zdrcal.Task.iNrRotations = 1

# Number of rays (inverse of Az resolution) in a rotation.
zdrcal.Task.iNrRays = 360

# Number of pulses in a ray.
zdrcal.Task.iSampleSize = 64

# Data resolution in bytes. Recommend:2 in long term use
zdrcal.Task.uiBytes = 2

# Standard RDA quality criteria (all measurands LOG, CCR, SQI;
width SIG in addition)
zdrcal.Task.fLOG_thr = 1
zdrcal.Task.fCCR_thr = 18
zdrcal.Task.fSQI_thr = 0.29
zdrcal.Task.fSIG_thr = 5

# Index of the Doppler filter, specified in setup_dsp.conf.
zdrcal.Task.iDopplerFilter = 1

Data Analysis

Zdrcal applies additional quality checks in data analysis, for qualified ZDR data points to be included in offset estimation.

Note that even the lowest reflectivity data have significant signal to noise ratios as they originate at short distances (<20 km / <12.4 mi). Avoid the highest practical reflectivities due to receiver saturation at very close distances.

Note also that the default settings presume Doppler velocity is negative for incoming (falling) echoes. The minimum co-polar correlation coefficient is set, because for low correlation echoes ZDR distribution is excessively broad. Non-atmospheric echoes (RF interference, and similar) are diminished by requiring several qualified bins in each ray. It is imperative for unbiased measurement that data of full antenna rotations are included only. The fraction of incomplete (or missing) rays must be kept low.

# Minimum reflectivity (dBZ)
zdrcal.Analysis.fMinimumDBZ = -15

# Maximum reflectivity (dBZ)
zdrcal.Analysis.fMaximumDBZ = 35

# Minimum fall speed (m/s, v_rain > 0)
zdrcal.Analysis.fMinimumV = -6

# Maximum fall speed
zdrcal.Analysis.fMaximumV = 0.5

# Minimum co-polar correlation coefficient (RhoHV)
zdrcal.Analysis.fMinimumRhoHV = 0.6

# Minimum number of qualified bins required in a ray
zdrcal.Analysis.iMinBinsRay = 2

# The closest range considered (km)
zdrcal.Analysis.fMinRangeKM = 0.850

# The fraction of missing rays allowed in the sample.
zdrcal.Analysis.fMaxMissingRays = 0.001

Result Files

The Zdrcal utility result files summarize the ZDR offset obtained in analysis of a given data set.

Result reporting is not bound to each radar task (that is each RAW product) performed, but the utility integrates over consecutive samples (proximate in time) until the anticipated precision passes the alarm threshold with a safety margin, or reaches the max time span. The offset estimate, it's intrinsic consistency, and actual uncertainty are then evaluated, and the sample is reset.

In this scope, the results can be generated at configurable pace and quality using the following options:

0

Implies that a result file is generated for each complete integration. Result file quality flags may indicate if the result is inconsistent (bResultValid = 0) or if the actual uncertainty was lower than anticipated (bResultPrecise = 0).

1

Omits reporting inconsistent results.

2

Reports only the highest quality results.

The 5 % false alarm rate can be expected for levels >0. The tight settings tend to require smooth precipitation on the radar, and result availability is limited in dry periods.

# Level of result reporting:

# -1: result file from each task (RAW). Not recommended in normal use.

# 0: all available results reported in result files.

# 1: all consistent results reported in result files.

# 2: results at target accuracy (or max sample) reported, only.
zdrcal.Analysis.iReport = 1

Quality Settings

The Zdrcal utility expects homogeneously selected data input, and changes in quality settings are to be avoided.

During commissioning phase, such changes may be necessary and the utility has the default policy "YES" to switch to new quality settings and to restart a fresh analysis.

During stable operation, it is recommended to switch the policy to "NO" which allows the processing exceptional RAW files (or run special tasks) of different quality as individual runs, while keeping the current main data archive separated, that is the data and settings unchanged.

# Policy in case these quality criteria conflict with the history settings.

# YES: Reset the history statistics, and assume the new criteria in future runs.

# NO: Omit the history data, the new settings used in the current sample, only. The history unchanged.
zdrcal.Analysis.sUpdate = "YES"

Miscellaneous

Zdrcal miscellaneous parameters are technical. Typical users do not need to modify them.

# 1=RVP Tags, 3=Antlib.
zdrcal.Misc.iAngleSource = 1

RAW Product Files

The Zdrcal utility reports RAW product files as intermediate results, allowing for detailed quality checks and distributed analysis.

The default setting is a typical IRIS path for polling incoming data.

When activated in the setup menu, input section, RAW products appear in IRIS product menu for network distribution and for visual inspection after automatic reingest.

In this operation mode, the RAW files are wiped automatically.

If no input pipe is configured, RAW files accumulate indefinitely and regular clean up is necessary.

# ZDRCAL RAW product directory:
zdrcal.sRawPath = "/usr/iris_data/input/"

Result Files

The Zdrcal utility reports result files in directory created during standard IRIS/RDA installation.

It is recommended that Zdrcal result files are redirected to a dedicated data directory, such as /usr/iris_data/zdrcal, which you must create.

# ZDRCAL results directory:
zdrcal.sResultDirectory = "/usr/iris_data/log/"

Data History

The default setting of Zdrcal utility is to use data history for obtaining high data availability at specified precision.

# ZDRCAL accumulates data over subsequent runs (recommended: YES)
zdrcal.sRunArchive = "YES"

For testing purposes, you can set the utility to process each RAW product as an independent sample (setting "NO")