Abrupt changes in cross polarizations observed during thunder

Abrupt changes in the cross-polarization discrimination (XPD) and cross-polar phase were observed in cross-polarization measurements at 4, 6, and 11 GHz on propagation paths with low-elevation angles. These abrupt changes were always observed during thunder, though exact time-to-time correspondence with lightning strokes was not clear in the measurement. In most cases, these sudden changes occurred in the direction in which the distortion of the polarization ellipse increases, and the rate of change in XPD was much faster than rain-induced depolarizations by an order of magnitude. Based on the simultaneous measurement of circular and linear polarizations at 11 GHz, it was also found that the differential phase-shift component suddenly increased to as large as 20 to 40 deg upon occurrence of these XPD changes, which confirms that this phenomenon is attributed to the effect of ice particles.