The Effects of Three-Body Scattering on Differential Reflectivity Signatures

Effects of three-body scattering on reflectivity signatures at S and C bands can be seen on the back side of large reflectivity storm cores that contain hail. The fingerlike protrusions of elevated reflectivity have been termed flare echoes or ‘‘hail spikes.’’ Three-body scattering occurs when radiation from the radar scattered toward the ground is scattered back to hydrometeors, which then scatter some of the radiation back to the radar. Three-body scatter typically causes differential reflectivity to be very high at high elevations and to be negative at lower elevations at the rear of the storm core. This paper describes a model that can simulate the essential features of the threebody scattering that has been observed in hailstorms. The model also shows that three-body scatter can significantly affect the polarimetric ZDR (differential reflectivity) radar signatures in hailshafts at very low elevation and thus is a possible explanation of the frequently reported negative ZDR signatures in hailshafts near ground.