Cloud Microphysics Retrieval Using S-Band Dual-Polarization Radar Measurements

The recent deployment of multiparameter, polarimetric radars provides the impetus for development of microphysical retrievals. The primary objective of this paper is to describe a particle classification technique that makes use of polarimetric radar observations. The particle classification technique is computationally simple enough to be implemented for real-time research and operational field programs. Also, when the NEXRAD (Next Generation Weather Radar) is upgraded to dual-polarization capability, operational radar meteorologists might be able to merge kinematic (Doppler data) and microphysical characteristics (polarization radar data) to improve forecasts. One of the merits of the technique described in this paper is that a radar meteorologist may not be required to know the complicated details and the intricacies of interpreting the data associated with polarimetric radar data processing. Several studies have shown that polarimetric observables (both linear and circular) can be used to identify hydrometeor types (Aydin et al. 1986; Doviak and Zrnic 1993; Hall et al 1984; Hendry and Antar 1984; Lopez and Aubagnac 1997; Straka and Zrnic 1993). Hendry and Antar (1984) used circular polarization measurements for delineating the major precipitation types such as drizzle, rain, melting layer, snowflakes, ice crystals, and ice pellets. However, rain or anisotropic precipitation in the propagation path between the antenna and the radar resolution volume introduces more bias in circular polarization radar measurements than in the case of linear polarization (Doviak and Zrnic 1993). Linear polarimetric radars, like the one used in this study, transmit and receive both horizontally and vertically polarized radiation, providing more information about the scattering media than conventional radar. Polarimetric radar observables depend on the microphysical characteristics of hydrometeors; namely, (a) particle size, (b) particle shape, (c) particle orientation relative to the local vertical direction, (d) phase (liquid or ice), and (e) bulk density (wet, dry, aggregate, or rimed). In addition to traditional reflectivity (Z HH ) and Doppler measurements, linear polarimetric observables include differential reflectivity (Z DR ), linear depolarization ratio (LDR), specific differential propagation phase (K DP ), and correlation coefficient (ρ HV ). Reflectivity is related to the power of a horizontally polarized backscattered electric field from a radar resolution Cloud Microphysics Retrieval Using S-Band Dual-Polarization Radar Measurements