Vertical and Horizontal Polarization Observations of Slowly Varying Solar Emissions from Operational Swiss Weather Radars

Abstract

Abstract:The electromagnetic power that arrives from the Sun in the C-band has been used to check the quality of the polarimetric, Doppler weather radar network that has recently been installed in Switzerland. The operational monitoring of this network is based on the analysis of Sun signals in the polar volume data produced during the MeteoSwiss scan program. It relies on a method that has been developed to: (1) determine electromagnetic antenna pointing; (2) monitor receiver stability; and (3) assess the differential reflectivity offset. Most of the results from such a method had been derived using data acquired in 2008, which was a period of quiet solar flux activity. Here, it has been applied, in simplified form, to the currently active Sun period. This note describes the results that have been obtained recently thanks to an inter-comparison of three polarimetric operational radars and the Sun's reference signal observed in Canada in the S-band by the Dominion Radio Astrophysical Observatory (DRAO). The focus is on relative calibration: horizontal and vertical polarization are evaluated versus the DRAO reference and mutually compared. All six radar receivers (three systems, two polarizations) are able to capture and describe the monthly variability of the microwave signal emitted by the Sun. It can be concluded that even this simplified form of the method has the potential to routinely monitor dual-polarization weather radar networks during periods of intense Sun activity.

Evaluating the Solar Slowly Varying Component at C-Band Using Dual- and Single-Polarization Weather Radars in Europe

“…In Section 4.1 of Gabella et al [5], it has been shown that the three series of precise 10.7 cm measurements acquired by DRAO are in practice undistinguishable in terms of comparison with radar observations. In this paper, similar to Gabella et al [5], the daily radar values presented in Section 3.3 will be evaluated against the 20 UTC dataset, which is used as the reference for quantitatively assessing the degree of agreement.…”

“…In this paper, similar to Gabella et al [5], the daily radar values presented in Section 3.3 will be evaluated against the 20 UTC dataset, which is used as the reference for quantitatively assessing the degree of agreement.…”

“…Holleman et al [8] extended the method towards quantitative electromagnetic power measurements, in order to monitor radar receiving chain stability. In the case of dual-polarization radars, which are able to measure both horizontal (H) and vertical (V) polarization, the same technique can be used to monitor the presence (and stability) of a residual differential reflectivity offset: the stability of differential radar reflectivity was investigated by Holleman et al [9] during a period of quiet Sun emissions (three months in 2008) and by Gabella et al [5] during high solar activity (the first seven months of 2014).…”

An integrated approach to monitoring the calibration stability of operational dual-polarization radars

“…The calibration of radar systems using the Sun as a radio source was first proposed by Whiton et al (1976) and developed in several works by Tapping (2001a), Holleman and Beekhuis (2004), Huuskonen and Holleman (2007), Holleman et al (2010a), Huuskonen et al (2014), Gabella et al (2014) and Altube et al (2015). The Sun is used for monitoring the receiver calibration, the alignment of the radar antenna and checking the antenna gain (Rinehart, 2004).…”

“…Over the years, many calibration techniques based on external sources have been developed, e.g., calibration with the Sun, and ones based on fixed and well-known targets, e.g., calibration with ground clutter echoes. The calibration using the solar interferences was first proposed by Whiton et al (1976) and has been subsequently applied on operational radars for the monitoring of the radar receiver chain and antenna pointing (Holleman and Beekhuis, 2004;Huuskonen and Holleman, 2007;Holleman et al, 2010a, b;Huuskonen et al, 2014;Gabella et al, 2014 andAltube et al, 2015). The ground clutter calibration allows the stability of the radar calibration to be monitored automatically, specifically the transmitting and receiving chain of both polarization channels, through statistical analysis of the echo power return from fixed targets (Silberstein et al, 2008 andWolff et al, 2015).…”