Combined Doppler and Polarimetric Radar Measurements: Correction for Spectrum Aliasing and Nonsimultaneous Polarimetric Measurements

Abstract

Combining Doppler and polarimetric information is advantageous for atmospheric studies. On the one hand, Doppler information gives insight into the microphysical and dynamic properties of radar targets, that is, radial velocity and its variability. The polarization diversity, on the other hand, has a strong link to the microphysical properties of targets such as shape and orientation. Polarimetric measurements, however, have an adverse effect on Doppler processing. Measurements of the complete scattering matrix require at least two pulses and result in the reduction of the maximum unambiguous Doppler velocity that can lead to Doppler spectrum aliasing. Moreover, dynamic properties of targets, because of the nonsimultaneity of the measurements performed with different polarizations, affect the accuracy of polarimetric radar measurements. A solution to these two problems is given in this paper. It is shown that by applying a relatively simple processing technique the effect of nonsimultaneous polarimetric measurements can be reduced even in the case of strong Doppler spectrum aliasing. This leads to better estimates of the copolar cross-correlation coefficient. Furthermore, this processing results in the maximum unambiguous Doppler velocity as if no polarimetric measurements were performed, with the added advantage of obtaining the actual Doppler velocities. To illustrate the proposed processing technique, precipitation measurements taken with the Delft Atmospheric Research Radar (DARR) are used.