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

Gabella, Marco; Huuskonen, A.; Sartori, Maurizio; Holleman, Iwan; Boscacci, Marco; Germann, Urs

doi:10.1155/2017/4971765

Cited by 3 publications

(4 citation statements)

References 15 publications

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“…This is partly compensated for by the fact that only one estimate out of many daily hits is retrieved. In Reference [11] ( Table 4), the standard deviation of the daily differential reflectivity during an active solar period in 2014 was 0.06 dB for Monte Lema (220 days) and 0.05 dB for the Albis radar (204 days); the dispersion of the difference between H and V during the same set of 100 days in 2014 was 0.06 dB for Albis and 0.08 dB for the Finish ANJ radar (see Table 3 in Reference [22]). In a recent manuscript that reviews several aspects of the monitoring of dual-polarization receiver using solar hits found in operational scans [12], a dispersion as low as 0.02 dB was found for ANJ.…”

Section: Differential (Horizontal/vertical) Radar Reflectivitymentioning

confidence: 99%

On the Use of Bright Scatterers for Monitoring Doppler, Dual-Polarization Weather Radars

Gabella¹

2018

Remote Sensing

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Bright" scatterers are useful for monitoring modern weather radars. In order to be "bright", a point target with deterministic backscattering properties should be present at a near range and be hit by the antenna beam axis. In this note, a statistical characterization of the echoes from a metallic tower located on Cimetta, at an 18 km range and at the same altitude as the Monte Lema radar, is presented. The analysis is based on five clear sky days (1440 samples with a spatial resolution of 1 • × 1 • × 83.33 m). The spectral and polarimetric signatures are striking: The spectrum width is perfectly stable; the mean radial velocity is very stable; the radar reflectivity is also quite stable, with the vertical (V) polarization being more variable than the horizontal (H) one. As far as the polarimetric information is concerned, the daily average of the differential reflectivity is approximately 1 ± 0.9 dB. The copolar correlation coefficient between H and V is remarkably large (0.9962, on average) and stable. It is believed that these unique and stable ground clutter signals could be used to monitor operational dual-polarization weather radars.

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Section: Differential (Horizontal/vertical) Radar Reflectivitymentioning

confidence: 99%

On the Use of Bright Scatterers for Monitoring Doppler, Dual-Polarization Weather Radars

Gabella¹

2018

Remote Sensing

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“…For Albis (7 values), the standard deviation is as small as˘0.04 dB. It is interesting to compare this very small dispersion of the difference between H and V with the one obtained using the operational method [2][3][4] for daily monitoring: during 220 (204) days in 2014, it was˘0.05 (˘0.06) dB, as can be seen in Table 4 in [4]; during the same set of 100 days in 2014, the dispersion of the difference between H and V was 0.06 dB for Albis and 0.08 dB for ANJ (see Table 3 in [5]). In a recent manuscript that reviews several aspects of the monitoring of dual-polarization receiver using solar hits found in operational scans [15], a dispersion as low as 0.02 dB was found for the Finnish ANJ and LUO radar.…”

Section: Summary Conclusion and Outlookmentioning

confidence: 80%

“…Using such a different technique for more than two hundred days in 2014, the standard deviation of the error of the horizontal channel of Albis (Monte Lema) was, as expected, much larger than with this Sun-tracking method:˘0.35 (˘0.48) dB (see Table 2 in [4]). By restricting the analysis to 100 days (see Table 4 in [5]), the standard deviation of the error results is smaller:˘0.26 (˘0.34) dB for Albis (Monte Lema), which is still considerably larger than with the Sun-tracking method. Similar results are obtained if we consider other C-band radar receivers in Europe: for the same 100-day period, the standard deviation of the error was˘0.26 dB for the Dutch Den Helder radar and˘0.36 dB for the Finnish Anjalankoski (ANJ) radar.…”

Section: Summary Conclusion and Outlookmentioning

confidence: 96%

“…Operational monitoring methods have been developed and implemented for determining the electromagnetic antenna pointing [1], assessing the receiver stability [2], and the differential reflectivity offset [3]; results from such methods were successfully applied, at first during a period of quiet solar flux activity (in 2008), subsequently to the currently active Sun period [4]. The ten C-band radar receivers analyzed in Finland, Switzerland, and the Netherlands were able to capture and describe the monthly variability of the Sun microwave signal [5].…”

Section: Introductionmentioning

confidence: 99%

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Calibration Accuracy of the Dual-Polarization Receivers of the C-Band Swiss Weather Radar Network

et al. 2016

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Abstract:The electromagnetic power that comes from the Sun has been proved to be an effective reference for checking the quality of dual-polarization weather radar receiver. Operational monitoring methods have been developed and implemented for determining the electromagnetic antenna pointing, assessing the receiver stability, and the differential reflectivity offset. So far, the focus has been on relative calibration: horizontal and vertical polarization have been mutually compared and evaluated versus the reference mainly in terms of standard deviation of the error. Radar receivers have been able to capture and describe the monthly variability (slowly varying component) of the microwave signal emitted by the Sun. In this paper, we present results from a novel Sun-based method aiming at the absolute calibration of dual-polarization weather radar receivers. To obtain best results, the radar receiver has to be off-line for a few minutes during the tracking of the Sun in order to have the antenna beam axis pointing at the center of the Sun. Among the five polarimetric weather radar receivers of the Swiss network, radar "WEI" located at an altitude of 2850 m next to Davos shows the best absolute agreement with the Dominion Radio Astrophysical Observatory (DRAO) reference for both horizontal (H) and vertical (V) polarization. Albis radar, which is located at an altitude of 938 m near Zurich, shows the largest difference: the radar receiver is too low compared to the Sun reference by´1.62 (´1.25) dB for the H (V) channel. Interestingly, the standard deviation of the error is smaller than˘0.17 dB for all Swiss radar receivers. With a standard deviation of˘0.04 dB Albis radar shows the best relative agreement between H and V. These results are encouraging and MeteoSwiss is planning to repeat off-line Sun-tracking measurements in the future on a regular basis.

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Measurement of Solar Absolute Brightness Temperature Using a Ground-Based Multichannel Microwave Radiometer

Lei

Wang

et al. 2021

Remote Sensing

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Ground-based multichannel microwave radiometers (GMRs) can observe the atmospheric microwave radiation brightness temperature at K-bands and V-bands and provide atmospheric temperature and humidity profiles with a relatively high temporal resolution. Currently, microwave radiometers are operated in many countries to observe the atmospheric temperature and humidity profiles. However, a theoretical analysis showed that a radiometer can be used to observe solar radiation. In this work, we improved the control algorithm and software of the antenna servo control system of the GMR so that it could track and observe the sun and we use this upgraded GMR to observe solar microwave radiation. During the observation, the GMR accurately tracked the sun and responded to the variation in solar radiation. Furthermore, we studied the feasibility for application of the GMR to measure the absolute brightness temperature (TB) of the sun. The results from the solar observation data at 22.235, 26.235, and 30.000 GHz showed that the GMR could accurately measure the TB of the sun. The derived solar TB measurements were 9950 ± 334, 10,351 ± 370, and 9217 ± 375 K at three frequencies. In a comparison with previous studies, we obtained average percentage deviations of 9.1%, 5.3%, and 4.5% at 22.235, 26.235, and 30.0 GHz, respectively. The results demonstrated that the TB of the sun retrieved from the GMR agreed well with the previous results in the literature. In addition, we also found that the GMR responded to the variation in sunspots and a positive relationship existed between the solar TB and the sunspot number. According to these results, it was demonstrated that the solar observation technique can broaden the field usage of GMR.

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

Cited by 3 publications

References 15 publications

On the Use of Bright Scatterers for Monitoring Doppler, Dual-Polarization Weather Radars

On the Use of Bright Scatterers for Monitoring Doppler, Dual-Polarization Weather Radars

Calibration Accuracy of the Dual-Polarization Receivers of the C-Band Swiss Weather Radar Network

Measurement of Solar Absolute Brightness Temperature Using a Ground-Based Multichannel Microwave Radiometer

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