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B.. Alberta - June 26, 1983 Two sets of seeded and unseeded hail cases are available from the Alberta Hail Project in 1983 (Divert, 1983). These cases provide an excellent study of feeder cells associated with larger hail-bearing clouds. The cases have excellent potential for open and closed experiments of natural and seeded clouds. During the summer of 1983, controlled seeding experiments of hailstorm feeder clouds were conducted as part of the Alberta Hail Project to test the sub- hypothesis that seeding results in an increased concentration of ice crystals whi ch 1 eads to more and earUerhail embryo (graupe 1) production. Ice-water budgets from one seeded an'a~"6he 'noi1:::'seeded feeder cloud pai r were studi ed for a feeder cloud pair on July 26, 1983 (Krauss, 1984). The clouds were treated with dry ice. Radar data is available to provide a more complete picture of the precipitation formation. On the afternoon of July 26, 1983, a hail storm formed in the northern pro- ject area and tracked over Rimbey on a southeasterly heading. From 63 reports, the maximum hailsizes were 19 shot, 36 pea, and 8 grape. The cloud base temperature was +6.4 oC. Two fee'der clouds were treated and systematically studied. Cloud number one was penetrated nine times between 17:32 and 18:08 MDT and received a placebo treatment. Cloud number two was penetrated seven times between 18:26 and 18:57 and was seeded with eight scoops (approximately 1280 grams) of dry ice' pellets. The clouds were very similar on the first passes, however, the rapid increase in the ice con- centration and dramatic seed signature are clearly evident for the second cloud. The computer controlled homing-pigeon onboard the research aircraft enabled the repeated penetration of the specified test cloud. Although the cloud widths and initial liquid water concentrations were similar, the evolution of the microphysical processes for the two clouds was quite dif- ferent. The average ice concentration was greater for the seeded cloud at all times up to 21 minutes after treatment. An ice plume concentration of 1490jL was observed 2.5 min after seeding with dry ice. The greater ice concentrations in the seeded cloud depleted the cloud liquid water faster than in the non- seeded cloud. The seeded cloud produced a higher concentration of riming size (diameters greater than .6 mm) particles and produced more 2 mm precipitation size particles faster. Data available for these two storms include: 1. radiosonde information on temperature, water vapor, and winds 2. synoptic data 3. surface measurements from regular AES stations 16. /- i