Height distribution of ice particles in wintertime thunderclouds observed by a dual polarization radar

A C-band dual polarization radar observed ice particles in the wintertime thunderclouds along the coast of the Sea of Japan. The polarimetric information (ZH, ZDR) is then discussed in view of prediction of lightning time and location. The observations were conducted in Arai, Niigata (37°00\´49"N, 138° 14\´32"E) in December 1992 and January 1993, succeeding those in Sakata, Yamagata in 1990 and 1991. Graupel particles and ice crystals are discriminated by their extremely low- and high-ZDR values, respectively. The height distribution of these ice particles is also confirmed by in-situ measurements using radiosonde. Before a lightning stroke occurs, graupel is shown to be lifted up to 3-4 km near the cloud top and then tends to descend to the cloud base, whereas ice crystals still ascend to the cloud top, suggesting the thunderstorm electrification between them. The electric charge distribution of each ice particle obtained from the radiosonde also indicates evidence of charge separation between graupel and ice crystals