ABSTRACT

Weather modification experiments are based on the comparison of treated (seeded) and nontreated (control) values which are sequentially dealt out according to an unknown meteorological scheme. For example, the meteorological scheme associated (a) with wintertime orographic experiments is often a sequence of specifically defined temporal periods (e.g., 3-hour, 6-hour, or 24-hour intervals) and (b) with summertime cumulus experiments is often a sequence of cumulus clouds which are both appropriate and available. As a consequence, weather modification experiments are more closely related to comparative surveys (i.e., sample surveys involving temporally changing populations) rather than to comparative experiments where any number of meaningful replications of a given experiment are easily implemented (perhaps even simultaneously). Because of meteorological variation over time, replications of a weather modification experiment are usually time consuming to implement and then questionable when obtained (regardless of the problems, replications of a weather modification experiment are essential).