A Numerical Experiment on the Spatial Distribution of Cloud Seeding Nuclei

George H. Milly The Travelers Research Center, Inc., Hartford, Conn.

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John T. Ball The Travelers Research Center, Inc., Hartford, Conn.

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David B. Spiegler The Travelers Research Center, Inc., Hartford, Conn.

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Abstract

An examination is made of the hypothesis that the inconclusive or marginal effects of many cloud seeding operations are due, at least in part, to an inhomogeneous distribution of freezing nuclei resulting in great ranges of concentration and extensive areas of overseeding and underseeding over the target region. Distributions of silver iodide nucleus concentrations arising from ground based generators were computed using a Gaussian plume diffusion model. Meteorological conditions and the number, locations, and yield of ground based generators were varied in a series of numerical experiments which bracketed conditions typical of many cloud seeding operations. The results indicated that effective seeding concentrations of nuclei can be achieved over a significant portion of the target area only by carefully considering initial atmospheric conditions as they affect nucleus diffusion and activity, and by accordingly designing and deploying the system of silver iodide generators.

Abstract

An examination is made of the hypothesis that the inconclusive or marginal effects of many cloud seeding operations are due, at least in part, to an inhomogeneous distribution of freezing nuclei resulting in great ranges of concentration and extensive areas of overseeding and underseeding over the target region. Distributions of silver iodide nucleus concentrations arising from ground based generators were computed using a Gaussian plume diffusion model. Meteorological conditions and the number, locations, and yield of ground based generators were varied in a series of numerical experiments which bracketed conditions typical of many cloud seeding operations. The results indicated that effective seeding concentrations of nuclei can be achieved over a significant portion of the target area only by carefully considering initial atmospheric conditions as they affect nucleus diffusion and activity, and by accordingly designing and deploying the system of silver iodide generators.

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