Supervised Fuzzy-Logic Classification of Hydrometeors Using C-Band Weather Radars

Abstract

A model-based fuzzy-logic method for hydrometeor classification using C-band polarimetric radar data is presented and discussed. Membership functions of the fuzzy-logic algorithm are designed for best fitting simulated radar signatures at C-band. Such signatures are derived for ten supervised hydrometeor classes by means of a fully polarimetric radar scattering model. The Fuzzy-logic Radar Algorithm for Hydrometeor Classification at C-band (FRAHCC) is designed to use a relatively small set of polarimetric observables, i.e., copolar reflectivity and differential reflectivity, but a version of the algorithm based on the use of specific differential phase is also numerically tested and documented. The classification methodology is applied to volume data coming from a C-band two-radar network that is located in north Italy within the Po valley. Numerical and experimental results clearly show the improvements of hydrometeor classification, which were obtained by using FRAHCC with respect to the direct use of fuzzy-logic-based algorithms that are specifically tuned for S-band radar data. Moreover, the availability of two C-band rainfall observations of the same event allowed us to implement a path-integrated attenuation correction procedure, based on either a composite radar field approach or a network-constrained variational algorithm. The impact of these correction procedures on hydrometeor classification is qualitatively discussed within the considered case study.

Hydrometeor classification through statistical clustering of polarimetric radar measurements: a semi-supervised approach

“…Lim et al, 2005), as well as between those using two-, or more, dimensional membership functions (e.g. Marzano et al, 2007), rather than one-dimensional ones (e.g. Liu and Chandrasekar, 2000).…”

Hydrometeor classification from polarimetric radar measurements: a clustering approach

“…Different HC algorithms are used at different frequencies, as in Straka et al (2000); Liu and Chandrasekar (2000) for S-band, Marzano et al (2007); Dolan et al (2013) for Cband, and Dolan and Rutledge (2009) ;Snyder et al (2010); Marzano et al (2010) for X-band. This is necessary because the scattering properties of hydrometeors vary with respect to the incident wavelength.…”

“…In other cases, they are instead adapted and modified in order to adequately reproduce actual observations (e.g. Marzano et al, 2007) or according to empirical constraints (e.g. AlSakka et al, 2013).…”

Case Study of the Hydrometeor Classification with the S-band Dual-Polarization Radar

“…Fig. 1은 이중편파 변수값에 따른 강수·강설입자의 구분과 범위를 나 타낸다 (Straka and Zrnic, 1993 (Vivekanandan et al, 1999;Lui and Chandrasekar, 2000;Ryzhkov et al, 2002;Marzano et al, 2006;Marzano, 2007;Dolan and Rutledge, 2009 (Straka and Zrnic, 1993 …”