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Show 4. 5 Case Studies This section provides case studies and analysis of results from several individual operations using differing modes of seeding and conducted from various locations. The methodology used is describ ed in 4. 5. 1, while examples of the correlation between calc ulated seeding effect times, precipitation rate signatures, and supporting physical measurements (i ce nucleus count, silver-in-precipitation, replica analysis, and vertical pointing radar) are g iven in Sections 4. 5. 2, 4. 5. 3, and 4. 5. 4. From the several case studies made, there is strong physical evidence that (1) silver was frequently present in precipitation at th e proper time and location to be asso ciated with se eding effect, (2) AgI particles acted as ice nuclei and produced marked changes in crystal habit, (3) the model for plume diffusion and seeded cry stal trajectory computations is reasonably accurate, and (4) in individual cases, positive seeding effects were e vident in precipitation rates. 4. 5. 1 Methodology Used for Making Case Studies In order to glean the optimum amount of information by synthesizing the various types of data collected during each operation , a sizeable number of analysis steps were necessary. These steps incorporated Mt. Harris vertical profiles of wind, temperature, humidity, and pressure with elements of cloud physics and atmospheric diffusion theory into a numerical model to arrive at computed a r eas and tim es of seeding effect. The numerical results were then used as a diagnostic tool in analysis of precipitation, silver-inprecipitation content,, crystal types, and AgI nucleation activity. The methodology is outlined below: 4. 5. L 1 Synoptic Map Pattern A qualitative study of the large scale synoptic weather pattern was made, paying particular attention to surface frontal boundaries and upper l evel trough position, strength, and moveme nt , and the moist air, precipitation, and flow patterns attendant therewith. Of particular importance is knowledge of the presence (or absence) of a general pattern of frontal convergence (post frontal over-running) precipitation over the area of intere~t as compared to the existence of only orograp hic precipitation. ,I 4. 5. 1. 2 Moisture Depth and Stability Mt. Harris radiosonde records taken during operation periods were analyzed 145 |
