Radar Performance Monitoring Using the Angular Width of the Solar Image

Huuskonen, A.; Kurri, Mikko; Hohti, Harri; Beekhuis, Hans; Leijnse, H.; Holleman, Iwan

doi:10.1175/jtech-d-13-00246.1

Cited by 17 publications

(24 citation statements)

References 5 publications

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“…Note that atmospheric attenuation is corrected in the Finnish and Dutch radars. Unfortunately, Sun hits are practically never detected with the radar beam axis hitting the center of the solar disk: hence, the challenge is to retrieve, by means of the least square method and Gaussian fit applied to the main lobe of the antenna radiation pattern, the peak solar power that the radar would have received if the beam had hit the Sun's center [7,10]. This is a crucial aspect of the retrieval: to derive, out of several tens of measurements per day, the most representative daily value; note that the signal-to-noise ratio of each measurement varies as a function of the angular distance between the Sun and the antenna radiation pattern beam axis.…”

Section: Horizontal and Vertical Polarization Radarmentioning

confidence: 99%

“…As stated in Section 3.3, a key aspect is the daily radar retrieval based on many solar hits, acquired at different angles of elevation and with different angular distances between the beam axis and the center of the Sun. The best approach is certainly the one described in Section 2, page 1705, of Huuskonen et al [10], which is based on a five-parameter linear model to retrieve the power that the antenna would have received if the beam had hit the Sun's center. Performance scores listed in Table 2 are based on such an approach.…”

Section: The Role Of Atmospheric Attenuation and Noise Subtractionmentioning

confidence: 99%

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

Gabella

Huuskonen

Sartori

et al. 2017

Advances in Meteorology

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Six C-band weather radars located in Europe (Finland, Netherlands, and Switzerland) have been used to monitor the slowly varying solar emission, which is an oscillation with an amplitude of several decibels and a period of approximately 27 days. It is caused by the fact that the number of active regions that enhance the solar radio emission with respect to the quiet component, as seen from Earth, varies because of the Sun's rotation about its axis. The analysis is based on solar signals contained in the polar volume data produced during the operational weather scan strategy. This paper presents hundreds of daily comparisons between radar estimates and the Sun's reference signal, during the current active Sun period (year 2014). The Sun's reference values are accurately measured by the Dominion Radio Astrophysical Observatory (DRAO) at S-band and converted to C-band using a standard DRAO formula. Vertical and horizontal polarization receivers are able to capture the monthly oscillation of the solar microwave signal: the standard deviation of the log-transformed ratio between radars and the DRAO reference ranges from 0.26 to 0.4 dB. A larger coefficient (and a different value for the quiet Sun component) in the standard formula improves the agreement.

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Section: Horizontal and Vertical Polarization Radarmentioning

confidence: 99%

Section: The Role Of Atmospheric Attenuation and Noise Subtractionmentioning

confidence: 99%

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

Gabella

Huuskonen

Sartori

et al. 2017

Advances in Meteorology

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“…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).…”

Section: Sun Calibrationmentioning

confidence: 99%

“…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).…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2016

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Abstract. The stability of weather radar calibration is a mandatory aspect for quantitative applications, such as rainfall estimation, short-term weather prediction and initialization of numerical atmospheric and hydrological models. Over the years, calibration monitoring techniques based on external sources have been developed, specifically calibration using the Sun and calibration based on ground clutter returns. In this paper, these two techniques are integrated and complemented with a self-consistency procedure and an intercalibration technique. The aim of the integrated approach is to implement a robust method for online monitoring, able to detect significant changes in the radar calibration. The physical consistency of polarimetric radar observables is exploited using the self-consistency approach, based on the expected correspondence between dual-polarization power and phase measurements in rain. This technique allows a reference absolute value to be provided for the radar calibration, from which eventual deviations may be detected using the other procedures. In particular, the ground clutter calibration is implemented on both polarization channels (horizontal and vertical) for each radar scan, allowing the polarimetric variables to be monitored and hardware failures to promptly be recognized. The Sun calibration allows monitoring the calibration and sensitivity of the radar receiver, in addition to the antenna pointing accuracy. It is applied using observations collected during the standard operational scans but requires long integration times (several days) in order to accumulate a sufficient amount of useful data. Finally, an intercalibration technique is developed and performed to compare colocated measurements collected in rain by two radars in overlapping regions. The integrated approach is performed on the C-band weather radar network in northwestern Italy, during July-October 2014. The set of methods considered appears suitable to establish an online tool to monitor the stability of the radar calibration with an accuracy of about 2 dB. This is considered adequate to automatically detect any unexpected change in the radar system requiring further data analysis or on-site measurements.

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“…Such technique, which allows relative calibration and mutual inter-comparison between vertical and horizontal channels has the great advantage of requiring no interruption of the weather surveillance and has been described in a series of papers [2][3][4][5][6]. The main disadvantage of such on-line technique consists in the necessity of retrieving the maximum signal that would have been observed by pointing the beam axis at the center of the solar disk by means of a five-parameter fitting procedure described in detail in [5]. Once the five parameters are derived, for instance by means of the least squares method, the peak solar power that the radar would have received if the beam had hit the Sun's center can be estimated.…”

Section: Checking Absolute Calibration Of Vertical and Horizontal Polmentioning

confidence: 99%

Checking Absolute Calibration of Vertical and Horizontal Polarization Weather Radar Receivers Using the Solar Flux

Gabella¹

2015

JEE

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A convenient and effective method for the absolute calibration of vertical and horizontal (dual-) polarization weather radar receivers is presented. The method is based on the relationship between the solar flux accurately measured in the S-band by the DRAO (Dominion Radio Astrophysical Observatory) and the retrieved power in the C-band by the vertical and horizontal receivers. One disadvantage of the method is that it requires the weather radar to be off-line for a few minutes during the tracking of the Sun (antenna radiation pattern beam axis hitting the center of the Sun). In order not to interfere with the operational scan, the method has been applied off-line to the 5 th and last weather radar that will be integrated in the Swiss network at the beginning of 2016. Both during the Factory Acceptance Tests (FAT5) in summer 2015 and at the Weissfluhgipfel site in autumn 2015, the antenna-mounted Vertical (V) and Horizontal (H) polarization receivers were used to retrieve the maximum solar irradiance hitting the parabolic antenna. For both H and V polarizations, best results were obtained at the site, as a consequence of a better assessment of receiver path losses. The average retrieved value of the horizontal channel is closer than the vertical one to the DRAO reference: at the site, for instance, the average multiplicative error (Bias) between the H (V) channel and the reference is -0.05 (-0.26) dB; the standard deviation of the error is 0.13 (0.09) dB for the H (V) channel. These preliminary results are so encouraging and promising that MeteoSwiss is planning to repeat such off-line Sun tracking observations using not only this 5 th and last weather radar but also the other 4 operational ones.

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Radar Performance Monitoring Using the Angular Width of the Solar Image

Cited by 17 publications

References 5 publications

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

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

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

Checking Absolute Calibration of Vertical and Horizontal Polarization Weather Radar Receivers Using the Solar Flux

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