# On the Use of Bright Scatterers for Monitoring Doppler, Dual-Polarization Weather Radars
## 3 Results
### On the Very Stable Characteristic of the 1 st Doppler Moment (Mean Radial Velocity)
#### 3.3.2 Small Dispersion of the Reflectivity: Scale Parameters Based on Logarithmic and Linear Scales  
Table 4 shows the two scale parameters that characterize the dispersion of the reflectivity distributions at the horizontal and vertical polarizations.  
It is once again interesting to observe the Log-transformed ratio between the 90 percentile and the average because of the particular features of the Cimetta radar bin, with respect to other ground clutter bins. This Log-transformed ratio is found to be between 3 and 4 dB for a very large number of ground clutter bins; it is considerably smaller for the Cimetta bin: The most likely value is 0.9 dB for the horizontal polarization and 1.2 dB for the vertical polarization.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \(\mathbf{10\cdot Log(ZH_{90}/Z\overline{H})}\) & \(\mathbf{10\cdot Log(ZV_{90}/Z\overline{V})}\) & **CoV[ZH]** & **CoV[ZV]** \\ \hline
5 January 2015 & 1.1 dB & 1.8 dB & 0.24 & 0.33 \\
9 February 2015 & 0.9 dB & 0.7 dB & 0.13 & 0.18 \\
10 February 2015 & 0.5 dB & 1.2 dB & 0.15 & 0.21 \\
13 October 2016 & 1.3 dB & 1.3 dB & 0.20 & 0.25 \\
18 January 2017 & 0.9 dB & 0.5 dB & 0.18 & 0.27 \\ \hline
5 days above & 0.91 dB & 1.07 dB & 0.20 & 0.26 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Dispersion of the radar reflectivity values (\(Z\)) for Horizontal (\(H\)) and vertical (\(V\)) polarization: Log-transformed ratio between the 90 percentile and the average (columns 2 and 3); ratio between the standard deviation and the average linear value of \(Z\) (columns 4 and 5).  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Date** & \(\mathbf{10\ Log(Z)}\) & \(\overline{10\ Log(Z)}\) & \(\mathbf{10\ Log(Z_{50})}\) \\ \hline
5 January 2015 & 81.89 dBZ & 81.77 dBZ & 81.5 dBZ \\
9 February 2015 & 81.65 dBZ & 81.59 dBZ & 81.5 dBZ \\
10 February 2015 & 82.03 dBZ & 81.97 dBZ & 82.0 dBZ \\
13 October 2016 & 81.21 dBZ & 81.12 dBZ & 81.0 dBZ \\
18 January 2017 & 81.08 dBZ & 81.01 dBZ & 81.0 dBZ \\ \hline
5 days above & 81.59 dBZ & 81.49 dBZ & 81.5 dBZ \\ \hline \hline \end{tabular}
\end{table}
Table 2: Values of three central location parameters for the horizontal reflectivity distribution.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline  & \(\mathbf{10\ Log(Z)}\) & \(\overline{10\ Log(Z)}\) & \(\mathbf{10\ Log(Z_{50})}\) \\ \hline
5 January 2015 & 80.20 dBZ & 79.95 dBZ & 80.0 dBZ \\
9 February 2015 & 80.81 dBZ & 80.73 dBZ & 81.0 dBZ \\
10 February 2015 & 80.85 dBZ & 80.75 dBZ & 82.0 dBZ \\
13 October 2016 & 80.24 dBZ & 80.08 dBZ & 80.5 dBZ \\
18 January 2017 & 79.97 dBZ & 79.83 dBZ & 79.5 dBZ \\ \hline
5 days above & 80.43 dBZ & 80.27 dBZ & 80.5 dBZ \\ \hline \hline \end{tabular}
\end{table}
Table 3: Same as Table 2, but for the vertical polarization.  
Another parameter shown in Table 4 is the ratio between the standard deviation and the average linear value of Z; this dimensionless quantity is often called the Coefficient of Variation (CoV) or relative dispersion. It should be noted that this value is exactly 1 for the [PERSON] backscatter model; it is significantly smaller than 1 for the Cimetta bin, which is affected to a great extent by the presence of the tall tower: the minimum (maximum) value was found on 9 February (5 January) 2015 for both polarizations. It is interesting to note that CoV\([ZV]\) is larger than CoV\([ZH]\) for all five days.