Validation of attenuation correction at X band performed with collocated S-band polarimetric radar

The Oklahoma University and NSSL have designed mobile X-band dual-polarization radar called XERES, i.e., X-band Experimental Radar for the Examination of Storms. In fall 2008 and spring 2009 XERES was brought next to the dual-polarization S-band WSR-88D KOUN situated in central Oklahoma. Both radars have a 1 deg beamwidth and employ same polarization technique with simultaneous transmission and reception of horizontally and vertically polarized waves. The radars executed similar volume coverage patterns that allowed point-by-point comparisons of radar variables. Data were collected from clouds, stratiform rain, and tornadic thunderstorms.

Procedures to correct XERES' reflectivity and differential reflectivity for attenuation using measured differential phase are applied. The corrected polarimetric variables are compared to the ones measured with the WSR-88D. It is shown that radar reflectivity Z and differential reflectivity ZDR measured at X and S band are generally consistent in areas which do not contain large wet hydrometeors. This confirms validity of the existing polarimetric techniques for attenuation correction at X band. In the regions containing such hydrometeors, the difference between Z, ZDR, and the copolar correlation coefficient measured at the two wavelengths are attributed to resonance scattering effects at X band.