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An instrumented cloud physics aircraft (Cessna 340) equipped with a variety of cloud physics measurement systems including an SF6 detector will be flown through the seeded convective bands. The aircraft will be flown as low as FAA regulations allow downwind of the seeding site to detect the SF6 entering the base of the convective bands, and subsequently at successively higher altitudes to document the dispersion of the seeding material within the band, potentially to the cloud tops within the convective bands. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The proposed research during the 2002-03 winter season utilizes this concept of documenting some of the links in the chain of events. Specifically, the proposed research will examine the initial links in the chain of events: (1) the ground release of silver iodide seeding material and a tracer gas (SF6) during convective band passages, (2) transport of the seeding material and tracer gas into the convective bands, (3) transport of the seeding material into regions of the convective band where the temperatures are less than -50C (the threshold of activation of silver iodide aerosols as ice nucleants) and, (4) seeding impacts upon the convective clouds' microphysics. The research will be conducted during a one month period (possibly February, 2003) and be focused upon obtaining some physical elucidation of the statistically significant "Black Box" results of seeding observed in Santa Barbara II, randomized "Phase I" research (the fixed-point burning of high output silver iodide flares during convective band passages). The proposed research would therefore fulfill the intent of the Bureau solicitation which is to "piggyback" research on to on-going operational cloud seeding programs. ~ S(y; ?( o~ ~~. · The basic design of the proposed experimentation will consist of the following elements: Concurrent releases of silver iodide and the tracer gas SF6, sulfur hexafluoride from ~ of three ground seeding sites used on the operational program (Mt. Lospe, Sudden PeaK, or Rancho Dos Vistas (see Figure 6). · A project-dedicated upper-air rawinsonde observation site (potentially to be located at Corona del Mar, just a few miles southwest of the Santa Ynez target area). Serial rawinsonde observations will be taken in each convective band as it passes overhead. The experimentation, and indeed the operational program, will both be designed to duplicate the seeding design used in the conduct of the Santa Barbara II research program, Phase I. In order to duplicate this seeding design of SBA II, Phase I, silver iodide flares manufactured by Ice Crystal Engineering, Inc. (ICE) of Davenport, North Dakota, will be fired sequentially from one of the three operational Automated, High-Output Ground Seeding (AHOGS) sites (see Fig. 1 or 6 for locations) during convective band passages. The flares will contain 150g each of seeding material and will be fired sequentially (this is one change from the original design in that flares were originally fired only every 15 minutes with individual bum times less than 15 minutes). It is felt that the flares need to be fired sequentially and SF6 released continuously during the passage of a convective band in order to provide a continuous source of seeding and tracer material that may be detected by the cloud physics aircraft without any gaps in the plumes. Each flare will bum approximately 5 minutes. Figure 10 compares the ICE flares and the earlier 400g flares (LW-83) used in the conduct of SBA II, Phase I. Figure 10 was produced from data obtained from tests of the two flares at the Colorado State University Simulation Laboratory. This figure Weather Damage Modification Program 22