## 5 Summary and Conclusions  
The electromagnetic power from the Sun can be used to check the quality of the polarimetric receivers of any weather radar network [9]. In recent years, the Dutch (KNMI) and Finnish (FMI)  
\begin{table}
\begin{tabular}{c c c c} \hline  & **Albis Radar** & **Lema Radar** & **Dole Radar** \\ \hline Number of median daily values used & 220 & 204 & 203 \\ Median value in dB & \(-\)0.65 dB & 0.17 dB & \(-\)0.40 dB \\
**Average value in dB** & \(-\)**0.66 dB** & **0.18 dB** & \(-\)**0.40 dB** \\
**Standard deviation in dB** & **0.05 dB** & **0.06 dB** & **0.06 dB** \\ \hline \end{tabular}
\end{table}
Table 4: Daily agreement between the horizontal and vertical channel Sun measurements.  
Meteorological Institutes have developed an \"'online' Sun method, in which the Sun's signals are automatically detected in polar volume data generated during operational scan programs. This method has proved to be successful for the daily monitoring of antenna electromagnetic pointing [1], of single polarization radar receiving chain stability [2], as well as for assessing the accuracy of the differential reflectivity of polarimetric weather radars [3]. Accurate estimates of the solar flux have been presented during a quiet period of the roughly 11-year slowly varying radio emission Sun cycle. This note describes results that have recently been obtained during the current, very active Sun period.  
As far as the relative agreement between the horizontal polarization receiving chain and the DRAO reference is concerned, [PERSON] _et al._[2] presented results for the first 46 days in 2008 for the Dutch De Bilt and Den Helder radars and for 44 days (from 1 July to 13 August 2008) for the Finnish Vimpeli and Luosto radars: the standard deviations of the log-transformed radar-to-DRAO daily ratios resulted in being 0.14, 0.17, 0.16 and 0.20 dB, respectively (quiet Sun period). As far as the MeteoSwiss weather radars are concerned, this note presents results obtained for the first 224 days of 2014. Despite the very active Sun period, satisfactory results have been obtained, as pointed out in Section 4.3 and shown in Figure 3. The Albis radar shows the best performance: the standard deviation of the log-transformed daily ratios is 0.35 dB (0.27 dB in case of the seven-day median filter). The values is 0.48 dB for the Lema and Dole radars (0.40 dB and 0.38 dB, respectively, in the case of the seven-day median filter).  
As far as the stability of differential reflectivity is concerned, [PERSON] _et al._[3] have presented results for a three-month quiet Sun period (March, April and May) in 2008 for the MeteoFrance radar located in Trappes: they obtained a standard deviation of the daily differential reflectivity that is slightly larger than 0.2 dB. Albis shows the best performance of the Swiss radars for the first seven months of 2014 (active Sun period): the standard deviation of the daily differential reflectivity is as small as 0.05 dB. The Lema and Dole radars also show good results (0.06 dB). It is possible to conclude that the method presented in this note, despite its simplified form, has the potential to routinely monitor dual-polarization weather radar networks, even during periods of intense Sun activity.