Microphysical Retrievals from Dual-Polarization Radar Measurements at X Band

Abstract

The recent advances in attenuation correction methodology are based on the use of a constraint represented by the total amount of the attenuation encountered along the path shared over each range bin in the path. This technique is improved by using the inner self-consistency of radar measurements. The full self-consistency methodology provides an optimization procedure for obtaining the best estimate of specific and cumulative attenuation and specific and cumulative differential attenuation.The main goal of the study is to examine drop size distribution (DSD) retrieval from X-band radar measurements after attenuation correction. A new technique for estimating the slope of a linear axis ratio model from polarimetric radar measurements at attenuated frequencies is envisioned. A new set of improved algorithms immune to variability in the raindrop shape-size relation are presented for the estimation of the governing parameters characterizing a gamma raindrop size distribution.Simulations based on the use of profiles of gamma drop size distribution parameters obtained from S-band observations are used for quantitative analysis. Radar data collected by the NOAA/Earth System Research Laboratory (ESRL) X-band polarimetric radar are used to provide examples of the DSD parameter retrievals using attenuation-corrected radar measurements. Retrievals agree fairly well with disdrometer data. The radar data are also used to observe the prevailing shape of raindrops directly from the radar measurements. A significant result is that oblateness of drops is bounded between the two shape models of Pruppacher and Beard, and Beard and Chuang, the former representing the upper boundary and the latter the lower boundary.

Comparison of different fittings of drop spectra for rainfall retrievals

“…Similar datasets have been used by many authors (e.g. [7,11,18]; and more recently [27]) to develop algorithms to retrieve rain properties. Substituting Eqs.…”

A cross frequency performance comparison of dual polarization attenuation correction algorithms at X and S band

“…Gorgucci et al [9]. introduced the technique of computing K dp /Z h vs Z dr to accomplish many self consistent evaluations.…”

“…Comparison of the self consistency parameter K dp /Z h before and after both attenuation correction for the X-SAPR radar. Also shown is the simulated results for three different drop size distributions from Gorgucci et al [9]. for the Beard and Chung(BC) and the Pruppacher and Beard Model(PB).…”

Evaluation of the self-consistency principle for calibration of the CASA radar network using properties of the observed medium

“…After evaluating different parameters reported in the literature, the parameters a, b and c were selected as 2.22×10-4, 1 and -4.39, respectively for an equilibrium linear axis ratio and Gamma drop size distribution [10]. Only data sets with the following characteristics were selected: signal-to-noise ratio HV ) greater than 0.95 and less than 0.995, Z H greater than 28 dBZ, and time periods with no rain over the radar in order to eliminate any wet radome effects [11].…”