Comments on “A New Look at the Israeli Cloud Seeding Experiments”

Abstract

Rangno and Hobbs (1995) cite a paper by the author (Ben-Zvi 1988) as providing information on the total number of days with rain in the Israeli II experiment. Unfortunately, this citation is not correct because that number is not written in the cited paper. The number of days in the paper by Ben-Zvi (1988) is for rain days over the studied watershed and its control area during the entire six meteorological years of the Israeli II experiment. Gagin and Neumann (1981) clearly and objectively limit the experiment to the season of November–April and to days on which a measurable depth of rain was recorded by three stations located at the buffer area. Consequently, the number of days in the experiment is smaller than that in the entire experimental period. Rangno and Hobbs (1995) cite Ben-Zvi’s (1988) finding that the depth of intense rainfall on seeded days at the analyzed target stations was heavier than that on unseeded days and that this difference was statistically significant. This citation is exaggerated, as no statistical test is mentioned in the original paper (Ben-Zvi 1988). Rangno and Hobbs (1995) present an apparent contradiction between the results of Gagin and Gabriel (1987) and those of Ben-Zvi (1988) regarding the effect of seeding on rainfall intensity. Yet Rangno and Hobbs (1995) do not refer to the difference in definition of the analyzed variables. The variable in the former paper is the distribution of mean daily intensity (i.e., the ratio of daily depth to duration), while that in the latter paper is total rainfall depth during the entire experimental period, sorted with respect to momentary intensities. These variables are quite different from each other, and hence their analyses need not lead to the same conclusions. Rangno and Hobbs (1995) cite Benjamini and Harpaz (1986) as analyzing runoff in the Lake Kinneret