Dual-polarization radar uses differential reflectivity, differential phase, and cross-correlation ratio to provide information about what?

• A. Precipitation ambient temperature.
• B. Shape and orientation of hydrometeors.
• C. Wind direction at ground level.
• D. Humidity distribution.

Answer: (B)

Dual-polarization radar uses those three measurements to reveal the microphysical properties of the precipitation, especially the shape and orientation of the hydrometeors. Differential reflectivity compares the horizontal and vertical backscatter, so when droplets are elongated and tend to align horizontally—like flat, oblate raindrops—the horizontal return is stronger and ZDR is positive; spherical droplets give ZDR near zero; and different ice crystals produce characteristic ZDR values. Differential phase tracks how the phase of the horizontal and vertical waves diverges as they travel through the targets, which grows with particle size and non-sphericity and helps distinguish types of precipitation and features like the melting layer. The cross-correlation ratio measures how similar the horizontal and vertical returns are; values near one suggest uniform, homogeneous scatterers, while lower values indicate mixtures or non-meteorological targets. Taken together, these measurements provide a detailed picture of the shape and orientation of the hydrometeors, rather than directly giving ambient temperature, humidity distribution, or surface wind direction.