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<br />1.0 INTRODUCTION <br /> <br />Recent debates in the literature regarding the effects of seeding <br />in the Florida Area Cumulus Experiment (FACE) show the importance of <br />thorough observation, analysis and modeling of mesoscale triggering <br />effects on convective rainfall. Nickerson (1980) found that the FACE <br />seeded cases had high seed/no seed ratios of observed rainfall in both <br />the target area and in the wide area around the target. Recent criti- <br />cisms of national weather modification programs show the need for a <br />thorough physical understanding of microphysical hypotheses and the <br />larger mesoscale features that control convective precipitation (Kerr, <br />1982a, b). These results suggest the need to observe, stratify and <br />predict the natural contribution of mesoscale forcing to the observed <br />rainfall in weather modification experiments. <br /> <br />Numerical model simulations of convective cloud development also <br />show the importance of correct initialization of mesoscale vertical <br />motion fields in two-dimensional (Chow and Orville, 1981) and three- <br />dimensional models (Pielke, 1974; Tripoli and Cotton, 1980; and Fritsch <br />and Chappell, 1981). A sensitivity study that shows the effect of <br />lifting on convective instability and cloud growth using a large (232) <br />sample of High Plains soundings indicates that lifting is an essential <br />triggering mechanism in this region (Matthews and Silverman, 1980). <br /> <br />In 1981, a major national research experiment - Cooperative Con- <br />vective Precipitation Experiment (CCOPE) - was sponsored by the Bureau <br /> <br />1 <br />