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

Abstract

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.

Insights into wind turbine reflectivity and radar cross-section (RCS) and their variability using X-band weather radar observations

“…With radar ground echo clutter simulations based on GECSX (Ground Echo Clutter Simulator) and a digital elevation model (DEM) with 50 m resolution, the radar visibility towards the wind turbines could be determined. The used approach follows the technique and developed software described in Gabella and Perona (1998) and Gabella et al (2008). Figure 1a shows the minimal-visibility elevation map, which is the minimum radar antenna beam elevation angle to get maximum 50 % beam blockage, starting from the weather radar observation site.…”

On the peculiar polarimetric signatures backscattered by a still or quasi-still wind turbine acquired by an X-band radar in stare mode at high temporal resolution (64 ms): preliminary investigations

“…(see for instance eq. 6 in Gabella (2018) for the MeteoSwiss quantization formula that permits increments as small as 0.0001 when close to 1). The X-band radar manufacturer has opted for a linear stretch from 0 to 1, which means equal increments of 0.0039 over the whole interval.…”

“…The reason is connected to the emerging interest toward "Bright" Scatterers (BS) (Rinehart, 1978) as additional tool for monitoring modern dual-polarization weather radars (Gabella, 2018). Thanks to the increased number of dual-polarization radars and in computational power for modeling and statistical analysis, a novel point of view regarding specific ground clutter has emerged.…”

Continuous Monitoring of Differential Reflectivity Bias for C-Band Polarimetric Radar Using Online Solar Echoes in Volume Scans

“…Three types of calibration methods are available to correct Z DR bias: instrumental calibration, standard reflection/natural scattering calibration [13,14], and standard radiation source calibration.…”

“…This method is relatively accurate, however the radar must be switched from the operational scan mode to the ball-tracking scan mode, which is not practical when many calibrations are required. A similar method was proposed by Gabella [13] in which the reflective object was changed to a fixed metallic tower. Meanwhile, in standard scattering calibration, the Z DR bias is estimated using specific raindrops/snowflakes [16] with a known polarization.…”