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<br />6 <br /> <br />4. Develop functional, quantitative descriptions of the ice <br /> <br />nucleating behavior of the aerosols under varying conditions of <br /> <br />cloud temperature, saturation, and droplet characteristics based <br /> <br />on experimental results. <br /> <br />5. Explore the implications and validity of the new descriptions of <br /> <br /> <br />ice nucleant behavior to specific cloud conditions. This is <br /> <br /> <br />initiated by incorporating them into Young's. Comparisons are <br /> <br /> <br />made to experimental data and some simulations relevant to summer <br /> <br /> <br />and winter cloud seeding are performed. <br /> <br />6. Compare simulations of seeded summertime clouds using the one- <br /> <br />dimensional Young model to special field measurements for cases <br /> <br />where one of the aerosols studied was utilized. <br /> <br />7. Final specific objectives are to define a minimum experimental <br /> <br />effort for describing the action of any ice nucleant in <br /> <br />atmospheric clouds and suggest procedures for evaluating these <br /> <br />results in seeding field experiments and operational programs. <br /> <br />1.3 General Approach <br /> <br />The approach to experiments was mechanistic, as defined by Vali <br /> <br />(1985). In this approach, the total nucleation activity is considered <br /> <br />to be the sum of the contributions from deposition, contact-freezing, <br /> <br />immersion- freezing and condensation-freezing nucleation modes. A <br /> <br />clarification is needed in this regard. The terminology nucleation mode <br /> <br />or nucleation mechanism will be used throughout this dissertation, <br /> <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />