A method for operational monitoring of a weather radar receiving chain, including the antenna gain and the receiver, is presented. The ''online'' method is entirely based on the analysis of sun signals in the polar volume data produced during operational scanning of weather radars. The method is an extension of that for determining the weather radar antenna pointing at low elevations using sun signals, and it is suited for routine application.The solar flux from the online method agrees very well with that obtained from ''offline'' sun tracking experiments at two weather radar sites. Furthermore, the retrieved sun flux is compared with data from the Dominion Radio Astrophysical Observatory (DRAO) in Canada. Small biases in the sun flux data from the Dutch and Finnish radars (between 20.93 and 10.47 dB) are found. The low standard deviations of these sun flux data against those from DRAO (0.14-0.20 dB) demonstrate the stability of the weather radar receiving chains and of the sun-based online monitoring.Results from a daily analysis of the sun signals in online radar data can be used for monitoring the alignment of the radar antenna and the stability of the radar receiver system. By comparison with the observations from a sun flux monitoring station, even the calibration of the receiving chain can be checked. The method presented in this paper has great potential for routine monitoring of weather radars in national and international networks.

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The dual Pulse Repetition Frequency (dual-PRF) technique for extension of the unambiguous velocity interval is available on many operational Doppler weather radars. Radial velocity data obtained from a C-band Doppler radar running in dual-PRF mode has been analyzed quantitatively. The standard deviation of the velocity estimates and the fraction of dealiasing errors are extracted and related using a simple model. A post-processing algorithm for dual-PRF velocity data, which removes noise and corrects dealiasing errors, has been developed and tested. It is concluded that the algorithm is very efficient and produces high-quality velocity data.

A method for the operational monitoring of the weather radar antenna mechanics and signal processing is presented. The method is based on the analysis of sun signals in the polar volume data produced during the operational scanning of weather radars. Depending on the hardware of the radar, the volume coverage pattern, the season, and the latitude of the radar, several tens of sun hits are found per day. The method is an extension of that for determining the weather radar antenna pointing and for monitoring the receiver stability and the differential reflectivity offset. In the method the width of the sun image in elevation and in azimuth is analyzed from the data, together with the center point position and the total power, analyzed in the earlier methods. This paper describes how the width values are obtained in the majority of cases without affecting the quality of the position and power values. Results from the daily analysis reveal signal processing features and failures that are difficult to find out otherwise in weather data. Moreover, they provide a tool for monitoring the stability of the antenna system, and hence the method has great potential for routine monitoring of radar signal processing and the antenna mechanics. Hence, it is recommended that the operational solar analysis be extended into the analysis of the width.