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<br />..., Braham: Field Experimentation in Weather Modification
<br />
<br />similar winter cloud systems. The. World Meteorological
<br />Organization plans an experiment in Spain (WMO 1978)
<br />which might provide the desired replication.
<br />Just because the Israeli experimen~tion is regarded as
<br />confirmed does not mean that all questions related to it
<br />have been answered. In particular, the seeding may have
<br />affected the dynamics as well as the precipitation
<br />efficiency of the clouds since model runs show that the
<br />system was highly susceptible to dynamic effects. An
<br />even more important but not widely recognized question
<br />was raised first by the Israel experimentation: whether
<br />the seeding may have had very large effects on just a few
<br />days and little or no effect on most others (Gabriel 1967).
<br />Although recent analyses have shown1 in Israel a multi-
<br />plicative seeding effect increasing with natural rainfall
<br />(and apparently no negative-effect cases), an important.
<br />consequence of the seeding is nevertheless an increase in
<br />rainfall variance.
<br />When cumululr-type clouds are involved, variable seed-
<br />ing effects are more pronounced, as illustrated in a
<br />twelve-year randomized experiment in Mexico (Siliceo,
<br />Ahumada A., and Mosino 1963). A main result of FACE 1
<br />is that six or seven "blockbuster" seeded days of very
<br />heavy rainfall were mainly responsible for the positive
<br />seed/no-seed difference. Predictor equations developed
<br />by Biondini (1979) suggest that without seeding, the
<br />target would hav~ been quite dry on these days. Work on
<br />FACE predictors is still continuing; this crucial area
<br />illustrates the productive interaction between physical
<br />insight and statistical tools.
<br />To confirm whether seeding results vary so Widely with
<br />conditions that marked successes in fact are often con-
<br />c.entrated on relatively few occasions and then to explain
<br />and utilize these variations if verified pose a challenge
<br />to increase the cooperation between meteorologists and
<br />statisticians in which Braham and his colleagues have
<br />pioneered and pointed the way. The goals of confirmed
<br />
<br />1 Personal communication from Dr. A. Gagin and Dr. J. Neumann,
<br />Directors of the Israel experiments.
<br />
<br />ROSCOE R. BRAHAM, JR.
<br />
<br />97
<br />
<br />experimentation on winter and elUmmer precipitatio~
<br />aUI~mentation, not to mention hail suppression and pos-
<br />sible beneficial hurricane moderation for which seeding
<br />trials have been attempted (but are not discussed here),
<br />ma,y be more di1licult to achieve than landing a man on
<br />the moon. But if any of these are accomplished, the results
<br />can provide as many advances to science and more
<br />prMtical benefits to humanity's terrestrial environment
<br />tmm the lunar feat.
<br />
<br />REFERENCES
<br />
<br />Biondini, RL. (1979), "Exploration of Florida Area Cumulus Ex-
<br />periment (1970-1976) FACE 1 Data Using Predictors," to be
<br />submitted to the Journal of Applied Meteorology.
<br />Bra.ham, RR, Bat.tan, L.J., and Byers, B.R (1957), "Artificial
<br />Nucleation of Cumulus Clouds," Chapter 4, No. 11, Meteorological
<br />McmograpM, 2, 47-85. .
<br />Gabriel, K.R (1967), "The Israeli Artificial Rainfall Stimulation
<br />E:xperiment. Statistical Evaluation for the Period 1961-1965,"
<br />Pr~edings of the Fifth Berkeley Symposium on Mathematical Sta-
<br />Ustic8 and Probability, V (Weather Modification), Berkeley: Uni-
<br />versity of Califonlia Press, 91-113. .
<br />Gagin, A., and Neumann, J. (1974), "Rain Stimulation and Cloud
<br />Physics in Israel," in Weather and CliTTIJ.ue Modification, ed. W.N.
<br />Hess, New York: John Wiley & Sons, 454--494.
<br />Sili,~eo, E. Perez, Ahumada A.A., and Mosmo, P.A. (1963), "Twelve
<br />Years of Cloud Seeding in the Necaxa Watershed, Mexico,"
<br />Journal of Applied Meteorology, 2, 311-323.
<br />Tukey, John W. (1069), "Analyzing Data: Sanctification or Detec-
<br />tiive Work?," American Psychologist, 24, 83-91.
<br />-- (1970), Exploratory Data Analy,~is, Limited Preliminary
<br />E:dition, Volume 1, Reading, Mass.:' Addison-Wesley Publishing
<br />Co" Introduction.
<br />-- (1977), "Some Thoughts on Clinical Trials, Especially
<br />Problems of Multiplicity," Science, 198,679-684.
<br />--, Brillinger, D.R, and Jones, L.V. (1978), The Management of
<br />Weather Resources, Volume I I: The Role of Statistics in Weather
<br />li:esources Management, Department of Commerce, Washington,
<br />D.C.: U.S. Government Printing Office.
<br />Woodley, W.L., Jordan, J.A., Simpson, J., Biondini, R, and Flueck,
<br />J. (1978), "NOAA'S Florida Area Cumulus Experiment Rainfall
<br />H.esults (1970-1976)," submitted to the Journal of Applied
<br />Meteorology.
<br />World Meteorological Organization (1978), "PEP (Precipitation En-
<br />hancement Experiment) Design Document," Report No.9,
<br />Weather Modification Program, World Meteorological Organiza-
<br />tilon, Geneva, Switzerland.
<br />
<br />Reioinder
<br />
<br />In responding to the wide range of topics raised by the
<br />discussants, I will treat first those which surfaced in
<br />several of the discussions a.nd then discuss some of the
<br />topics raised by a single individual. Time and space pre-
<br />clude responding to all issues raised.
<br />At the outset, let me note appreciation to Professor
<br />Cook and Mr. Holschuh for reminding us of the quotation
<br />
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<br />by R.A. Fisher. "I hope that we are moving into a period
<br />of more emphasis on confirmatory experiments with such
<br />pro,jects as FACE II and CRBPP II. However, as of now,
<br />only the glaciogenic seeding of superc90led stratus and
<br />strl:l.tocumulus clouds meets this "Fisher Test" in the eyes
<br />of a.ll concerned. Not only have results from seeding these
<br />clouds been repeated many timeel, but meteorologists
<br />
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