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<br />efficiency considerably affected by such an internal charge distribution for aerosol particles <br />0.1 $; r $; 1.0 m. The present results imply that growing ice crystals containing dilute concentrations of <br />ionizable salts may exhibit higher coIlision efficiencies. The present theoretical results reconcile the <br />previously widely diverging results of snow crystal scavenging reported by many researchers. This <br />study suggests that as aggregates fonn and grow, the internal charge distribution effect diminishes, while <br />the net charge effect increases. <br /> <br />Smith, P. L., Z.. Liu, and J. Joss, 1993: A study of sampling-variability effects in raindrop-size observations. <br />Journal of Applied Meteorology, 32 (accepted). <br /> <br />Because of the randomness associated with sampling from a population of raindrops, the data conk'lin <br />some undetennined mixture of sampling variability and real physical variations in the precipitation. <br />This study begins with a Monte-Carlo simulation of the sampling process and then evaluates the <br />resulting estimates of the characteristics of the underlying drop population. The characteristics <br />considered include the liquid water concentration and the reflectivity factor; the maximum particle size <br />in each sample is also detennined. The results show that skewness in the sampling distributions when <br />the samples are small (which is the usual case in practice) produces a propensity to underestimate all of <br />the characteristic quantities. In particular, the distribution of the sample maximum drop sizes suggests <br />that it may be futile to try to infer an upper truncation point for the size distribution on the basis of the <br />maximum observed particle size. <br /> <br />Resulting paired values, e.g., of Z and W, for repeated sampling were plotted on the usual type of <br />log-log scatter plots. This yielded quite plausible-looking "Z_R" and "Z-W" relationships even though <br />the parent drop population (and hence the actual values of the quantities) were unchanging; the <br />"relationships" arose entirely from the sampling variability. Moreover, the sample points are shown to <br />be necessarily displaced from the point corresponding to the actual population values if the sample size <br />is small. Consequently, any assessment of the "accuracy" of a Z-R relationship based on drop-size data <br />should include some consideration of the numbers of drops involved in the samples making up the <br />scatter plot. These findings shed a new perspective on the reasons for some of the variability appearing <br />in the wide range of Z-R relationships reported in the literature. <br /> <br />Smith, P. L., 1992: Hail suppression activity around the world. Preprints, Symposium on Planned and <br />Inadvertent Weather Modification, Atlanta, GA, January 5-10, 1992. American Meteorological Society, <br />Boston, MA, 28-34. <br /> <br />No abstract. <br /> <br />Smith, P. L., A. G. Detwiler, J. H. Helsdon, M. R. Hjelmfelt, L. R. Johnson, F. J. Kopp, H. D. Orville, <br />D. L. Priegnitz, and J. P. Searles, 1992: Continuing analysis of data for the North Dakota Thunderstonn <br />Project. Report SDSMf/lASIR-92/01 to North Dakota Atmospheric Resources Board, subcontract under <br />NOAA Cooperative Agreement NA90AAH0176. Institute of Atmospheric Sciences, South Dakota <br />School of Mines & Technology, Rapid City, SD, 167 pp. <br /> <br />No abstract. <br /> <br />70 <br />