Z_DR measurement considerations for a fast scan capability radar

Abstract

This paper discusses the possibility of incorporating differential reflectivity (ZDR) measurement in Doppler radars having fast scan capability, without compromising the accuracy of the spectral moment estimates. The presently established technique of ZDR measurement using alternate sampling of horizontally and vertically polarized signals (H and V) has long acquisition time and reduced maximum unambiguous velocity. It is shown that ZDR acquisition time can be reduced significantly by simultaneously sampling H and V signals and range averaging, which does not compromise spectral moments estimation capability and volume update time. An analysis of variance of ZDR suggests that accurate estimation of ZDR at scan rates of 18° s−1 is possible only if correlation between simultaneously received horizontally and vertically polarized echoes is better than 0.995. A theoretical investigation of all the factors that contribute to the decorrelation established that this indeed is the case for rain media. A scheme for ZDR measurement is suggested which uses +45° and −45° polarized transmissions alternately and simultaneous reception of H and V signals to compensate for bias error due to propagation. Further, a method for nearly eliminating the bias error due to receiver mismatch is suggested.

Quality Control and Calibration of the Dual-Polarization Radar at Kwajalein, RMI

“…Canting and scattering properties are of minimal concern in light rain and drizzle due to the mainly spherical shape of the small drops. Theoretical values of ρ HV larger than 0.99 are indicated by Sachidananda and Zrnic (1985) because of the small shape effects in rain, but theory does not account for possible decreases due to sidelobes and receiver noise.…”

Compressed sensing applied to weather radar

“…This is defined as (Sachidananda and Zrnić 1985). The is therefore useful for identifying non-rain hydrometeors.…”

Detection of potentially hazardous convective clouds with a dual-polarized C-band radar

“…Gourley et al (2006) reported ρ HV (0) peak values in rain better than 0.99 for the Trappes radar with a sample number of 23 and a time resolution of 15 min. More recently, Yamauchi et al (2012) reported ρ HV (0) peak values of 0.998, which implies the use of a surprisingly reliable radar, as this value is very close to the theoretical expectation of 0.999 for drops without oscillation A. Adachi et al: Detection of potentially hazardous convective clouds 2743 (Sachidananda and Zrnić, 1985). Additionally, they recorded this peak value with a sample number of 20, which enabled volumetric scans with a time resolution of 4 minutes for their system.…”

“…Sachidananda and Zrnić (1985) showed that reliable polarimetric data can be obtained from 50 simultaneous samples when ρ HV (0) > 0.995 and the spectrum width > 4 m s −1 . The value of ρ HV (0) measured with polarimetric radars has been increasing with the advent of innovative radar technology.…”