Size and number concentration of liquid PSCs: Balloon-borne measurements at Ny-Alesund, Norway in winter of 1994/95

Size (radius: 0.15-1.8 mu m) and number concentration of polar stratospheric clouds (PSCs) were observed with a balloon-borne particle counter at Ny-Angstrom lesund, Norway (79 degrees N, 12 degrees E) in winter of 1994/95 (December 18, 1994 and January 17, 1995). The measurements suggested that PSCs actively formed in the cold winter stratosphere. During the balloon-borne measurements, the depolarization ratio of PSCs was monitored with a lidar near the balloon observational site to see the phase (liquid or solid) of PSCs. Both measurements suggested that many sub-layers were contained in the PSCs. Particle size distribution of the early PSCs event (December 18, 1994) was different from that observed on January 17, 1995, after active PSCs events. This difference possibly suggests that particle formation processes were largely disturbed by redistribution of chemical constituents relating with PSCs formation and growth in the polar winter stratosphere. Lidar measurements suggested active formation of liquid phase PSCs in addition to solid phase PSCs. The number-size distribution pattern showed enhancement of the number of particles with their radius larger than 1.8 mu m in the solid state sub-layer of PSCs. On the other hand, not only large particles (r > 1.8 mu m) but also smaller particles (r = 0.25-0.6 mu m) were enhanced in the liquid state PSCs.