Hail Sizing at Three-Body Scattering

Three-body scattering (TBS) typically manifests itself as radial protuberances beyond main radar echoes. Such patterns are caused by scattering of radar radiation from reflectivity cores to the ground, reflected from the ground to reflectivity cores, and then scattered back to radar. At S frequency band, TBS frequently occurs in hail thunderstorms.

Current methods of hail detection are based on hydrometeors’ backscattering properties. Reflectivity (Z), differential reflectivity (ZDR), the correlation coefficient (CC), and specific differential phase (Kdp) are used in the methods. These methods cannot be applied for TBS because more scattering processes are involved. We analyzed polarization properties of radar echoes caused by TBS along with their Doppler characteristic to estimate the size and number concentration of hail. Our analysis shows that the differential phase (Pdp) is an important variable in hail detection along with other radar variables used in various hail detection methods. Links between the hail size and ZDR, CC, and Pdp at TBS are discussed. We show results from several thunderstorms produced large and giant hail and observed with Nexrad radars.