Observations of hail cores of tornadic thunderstorms with three polarimetric radars

Series of severe tornadic thunderstorms that hit Oklahoma in May 2013 were observed with three polarimetric radars: two S-band WSR-88Ds (KOUN and KCRI) and the mobile NSSL's X-band radar. The sizes of hailstones from these thunderstorms reached 7 cm. Such giant hailstones exhibit strong scattering resonances and produce different reflectivities even inside the same frequency band. Two S-band radars (KOUN and KCRI) have different frequencies and exhibit noticeable difference in reflectivities that can be used as an indication of giant hail. Attenuation correction has been carried out at X band and corrected characteristics are compared against those obtained with the S-band radars.

Polarimetric characteristics of hail cores obtained at three radar wavelengths are compared. Differences in differential reflectivities, the differential phases, and correlation coefficients are discussed. It is shown that the differential phase upon scattering can be used for hail indication at X band.

The differential Doppler velocities (DDV) defined as the difference of velocities measured at horizontal and vertical polarizations is also discussed. Images of DDV from these thunderstorms show that this parameter can be used for identifying areas of the main inflows. The inflow areas can be identified even in cases where the main inflow is orthogonal to the radar beam so that the Doppler velocity cannot be used to recognize it.