Vaisala RVP900

USER’S MANUAL__________________________________________________________________
204 _________________________________________________________________ M211322EN-D
meteorological signal S, the clutter power C and the noise power N. R
0
is
equal to the sum of the meteorological signal S and noise power N which
is measured directly on the RVP900 by periodic noise sampling. T
o
and R
0
are used for calculating the dBZ values- the equivalent radar reflectivity
factor which is a calibrated measurement. The physical models for R
0
, R
1
and R
2
correspond to a Gaussian weather signal and white noise as shown
in Figure 38 on page 197. W is thespectrum width and V' the mean
velocity, both for the normalized Nyquist interval on [-1 to 1].
The autocorrelation lags above and the corresponding physical models
have five unknowns: N, S, C, V', W. Because the R1 and R2 lags are
complex, this yields, effectively, five equations in five unknowns using the
constraint provided by the argument of R1. This closed system of
equations can be solved for the unknowns which is the basis for calculating
the moments from the autocorrelations.
6.2.4 Ray Synchronization on Angle
Boundaries
The exact value of M that is used for each time average will generally be
the “Sample Size” that is selected by the SOPRM command (see Section
7.3 Setup Operating Parameters (SOPRM) on page 259). However, when
the RVP900 is aligning its processed rays to AZ/EL angle boundaries (see
Section 7.15 Load Antenna Synchronization Table (LSYNC) on page 312)
the actual number of pulses used may be limited by the number that fit
within each ray’s angular limits at the current antenna scan rate. The value
of M will never be greater than the SOPRM Sample Size, but it may
sometimes be less. For example, suppose the RVP900 is operating at
1 KHz PRF, 20-deg/sec scan rate, 1-degree ray synchronization, and a
Sample Size of 80. Then, if the LSYNC Dyn bit is set, rays will consist of
a full 80-pulses ending at each angle and extending back 30-pulses into the
previous angle sector. However, when Dyn is clear, there will be 50 pulses
used for each ray (not 80) and those pulses will exactly fill the scanning
angle sector.