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<br />DECEMBER 1978
<br />
<br />LARRY VARDIMAN AND JAMES A. MOORE
<br />
<br />1777
<br />
<br />criteria can be developed into specific criteria for a
<br />given location if one knows the cloud climatology and
<br />basic barrier parameters. Research projects can use pre-
<br />dictors from this technique to formulate hypotheses and
<br />operational programs can improve seeding efficiency.
<br />Since these results came from an a posteriori analysis,
<br />they need further verification with additional data.
<br />There may be sufficient data from other winter oro-
<br />graphic programs to conduct such verification. Data
<br />from new projects should also be explored.
<br />
<br />7. Further comments
<br />
<br />Subsequent to the study reported in this paper, dis-
<br />cussion with Lewis 0, Grant has revealed that re-
<br />analysis of the Climax experiment has shown some
<br />problems with the distribution of meteorological events
<br />in the seed/no-seed categories (personal communica-
<br />tion), Stratification by southwesterly and northwesterly
<br />storms seems to indicate that the seeded sample con-
<br />tained more warm, moist southwesterly storms than
<br />the no-seed sample. At this time, indications are that
<br />some fraction of the positive seeding effect may have
<br />been due to the imbalance in the sample events. How-
<br />ever, final determination of the magnitude and extent
<br />of the effect has not been completed.
<br />Since Climax contributed 420 cases to our total
<br />sample of 1248 cases, such an, effect would impact this
<br />study. Until the problem is resolved it is impossible
<br />to say what the effects will be.
<br />However, possible changes in seeding effect from the
<br />Climax reanalysis may not be critical for several
<br />reasons. The major purpose of this study was to identify
<br />ranges of meteorological variables that have a general
<br />response to seeding. Not only did the pooled samples
<br />allow development of generalized seedability criteria,
<br />but project-by-project analysis also generally supported
<br />these criteria. Unless a similar distribution of seed/no-
<br />seed events occurred in each project, similar results on
<br />a project-by-project basis would not be expected.
<br />Another major purpose of this study was that all major
<br />meteorological variables which are important in the
<br />cloud response to seeding be identified. Even if there
<br />are some poor distributions of storm types which affect
<br />the distributions of meteorological variables, the com-
<br />parison of seed/no-seed events is not compromised, if
<br />all major variables have been properly identified. The
<br />results of this study would seem to indicate that the
<br />most important variables have been determined.
<br />These comments should persuade the reader to re-
<br />serve full judgment about the results of this study until
<br />the uncertainties with Climax are resolved. However,
<br />the findings of this study are so strong that the Climax
<br />results would probably only have a major impact if
<br />they are very severe. In fact, the results of this study
<br />seem to strengthen the physical reasoning of the
<br />original Climax results.
<br />
<br />Acknowledgments. The authors appreciate the data
<br />analysis and suggestions provided by Mr. Robert
<br />Elliott and the staff of North American Weather Con-
<br />sultants, Inc., during the early phases of this study. A
<br />special thanks goes to Dr. Paul Mielke for his insightful
<br />discussions and helpful suggestions on the statistical
<br />aspects of our analysis. Mr. Donald Rottner provided
<br />the basic nonparametric statistical computer program
<br />used in this analysis and assisted in altering it for this
<br />use. Mr. Francis Politte assisted in reducing the data
<br />from the various projects into a standard format.
<br />
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