Evaluation of multifrequency range imaging technique implemented on the Chung–Li VHF atmospheric radar

Abstract

Abstract. The multifrequency range imaging technique (RIM) has been implemented on the Chung-Li VHF array radar since 2008 after its renovation. This study made a more complete examination and evaluation of the RIM technique to facilitate the performance of the radar for atmospheric studies. RIM experiments with various radar parameters such as pulse length, pulse shape, receiver bandwidth, transmitter frequency set, and so on were conducted. The radar data employed for the study were collected from 2008 to 2013. It has been shown that two factors, the range/time delay of the signal traveling in the media and the standard deviation of Gaussian-shaped range-weighting function, play crucial roles in ameliorating the RIM-produced brightness (or power distribution); the two factors are associated with some radar parameters and system characteristics. The range/time delay of the signal was found to increase with time; moreover, it was slightly different for the echoes from the atmosphere with and without the presence of significant precipitation. A procedure of point-by-point correction of range/time delay was thus executed for the presence of precipitation to minimize the bogus brightness discontinuity at range gate boundaries. With the RIM technique, the Chung-Li VHF radar demonstrates its first successful observation of double-layer structures as well as their temporal and spatial variations with time.

High-range resolution spectral analysis of precipitation through range imaging of the Chung-Li VHF radar

“…The point-by-point correcting procedure with an adjustable-range delay proposed by Chen et al (2016a) may be useful to mitigate the discontinuity of precipitation power spectra at gate boundaries, as shown in Fig. 3d.…”

“…Each array consists of 64 Yagi antennas that are laid out in an 8 × 8 square, and can launch and receive signals both obliquely and vertically. After exhibited the first RIM observation using this radar, a large amount of RIM data have been collected by the same radar (Chen et al, 2016a). The present study employed the data collected between 21 and 23 August 2013, when the typhoon Trami passed through the Taiwan area and both stratiform and convective precipitation occurred.…”

“…1 and 2, the disadvantage of using RIM to process the precipitation echoes is the presence of artificial discontinuities in the power spectra at range gate boundaries; regardless, the range delay and range-weighting function effect have been corrected using the procedure used by . In order to mitigate the artificial discontinuity in power spectra at range gate boundaries, the point-by-point correcting procedure for the range delay and range-weighting function was employed (Chen et al, 2016a); the results are shown in Fig. 3.…”

“…Based on the aforementioned progress in the radar remote sensing of atmosphere using multi-frequency techniques, we made a study of precipitation, using the time-signal inversion process of RIM data as well as the calibration procedures developed by and Chen et al (2016a). The observed data were collected during 21-23 August 2013, from the Chung-Li VHF radar located in northwestern Taiwan.…”

“…In a later study, Chilson (2004) applied time-signal inversion process to the RIM data to obtain temporal signals in sub-gates and executed the spectral analysis for each sub-gate, giving high-resolution spectra of the atmospheric echoes in the range direction. To improve the continuity of the brightness distribution through the range gate boundaries, developed a calibration process for the RIM, and in a later study Chen et al (2016a) proposed further a procedure of point-by-point calibration for the RIM analysis of precipitation echoes in the time domain. Such a calibration procedure was applied in this study.…”