Vaisala RVP900 User Manual

Chapter 6 ______________________________________________________ Processing Algorithms
VAISALA______________________________________________________________________ 227
Further, each qualifier test can be AND'd and OR'd with any other. This
allows very complex thresholds criteria to be constructed as required. The
four threshold qualifiers are:
The following are the default threshold combinations for each of the
parameters that can be selected for output from the RVP900:
LOG This is a measure of signal strength that is usually used for
the thresholding of reflectivity data. The default LOG
threshold value is 0.75 dB.
SQI The SQI threshold is typically used for velocity and width
thresholding since it is a measure of the coherency. It is a
number between 0 and 1 (dimensionless), where 0 is
perfect white noise and 1 is a pure tone (perfect Doppler
signal). The default SQI threshold value is 0.4.
CCOR The clutter correction threshold is typically used to reject
measurements when the clutter in a range bin is very strong
(i.e., when the calculated CCOR is a large negative number
in dB). The appropriate value depends on the coherency of
the radar system. The default threshold is set to -18 dB.
Threshold values less than this (more negative) reject
fewer clutter bins. Threshold values closer to zero reject
more clutter bins.
SIG This is typically used only for thresholding the spectrum
width to assure that the signal power is strong enough for
an accurate width measurement. The default threshold
value is 5 dB. If R
2
processing is used, this can usually be
reduced to 5 dB for width thresholding.
PMI The PMI is typically used to reject echoes that are
identified as inconsistent with the preferred hypothesis of
precipitation. Identification is based on combined
interpretation of polarimetric measurements of reflectivity,
differential reflectivity, differential phase and co-polar
correlation coefficient by the HydroClass pre-classifier.
The default threshold value is 0.45.
Parameter Description Threshold
dBZ Reflectivity with clutter correction LOG and CCOR
dBT Reflectivity without clutter correction LOG
V Mean velocity SQI and CCOR
W Spectrum width SQI and CCOR and SIG
Dual Pol Differential reflectivity LOG

Vaisala RVP900 Specifications

General

Brand	Vaisala
Model	RVP900
Category	Receiver
Language	English