DualPolarization

Dual-polarization, or dual-pol, is a radar technology that transmits and receives both horizontal and vertical polarizations. By capturing how precipitation particles interact with differently polarized waves, dual-polarimetric radar provides richer information than conventional single-polarization systems.

In polarimetric radar, several observables are derived from the dual-polarization signals. Reflectivity factors ZH and ZV describe the energy returned in the horizontal and vertical channels. Differential reflectivity ZDR indicates the relative size and orientation of hydrometeors, while differential phase ΦDP and the related specific differential phase KDP reveal the phase shift caused by propagation through the target. The cross-correlation coefficient ρHV measures the similarity of the horizontal and vertical returns and aids in identifying particle types. Doppler processing can also provide velocity information to complement the polarimetric data.

Applications of dual-polarization radar include improved precipitation type discrimination (such as rain, hail, or snow), more accurate rainfall rate estimation, and enhanced hydrometeor classification. The richer data improve weather forecasting, severe storm detection, and aviation meteorology, as well as hydrological analyses.

History and deployment: polarimetric radar concepts emerged in the late 20th century, with operational adoption in national radar networks during the 2000s and 2010s. In the United States, the Weather Surveillance Radar-1988 Doppler (WSR-88D) system was upgraded to dual-polarization starting in the 2010s, enabling widespread use of dual-pol data.

Limitations and challenges include the need for careful calibration, more complex data processing, and attenuation and phase-unwrapping issues. Data quality control and specialized interpretation algorithms are essential for reliable use.