Dual polarization radar observations of ice particles in wintertime thunderclouds related to lightning locations

Dual polarization radar observation of anomalous wintertime thunderclouds were conducted using the DND radar of the Ministry of Construction of Japan. A large number of examples of lightning strokes were obtained on December 22-23, 1990. The thunderclouds form a band-like horizontal structure and move from west to east as the cold front approaches the radar site. At the moment of each lightning stroke, the cloud top reaches ~6 km height, and the graupel echoes with low-Z _DR values are found up to 5 km. They are shown to approach the ice crystals echoes with high-Z_DR values which are seen to be rapidly blown up from 2 to 6 km height around the lightning time. Thus, the present observational evidence strongly suggests riming electrification due contact and mixing between these two kinds of ice particles as described by thunderstorm electrification theory. The polarization radar technique seems to be promising for the prediction of lightning time and location