Critical Issues in Weather Modification Research (2003) / Chapter Skim
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3 Evaluation Requirements for Weather Modification
3 Evaluation Requirements for Weather Modification
Pages 39-44
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From page 39... ...
The challenge for the scientific community is to develop acceptable evaluation criteria to ensure float future research and operational programs build a solid scientific foundation for fi~rthe~ advances. This chapter examines issues related to designing and evaluating weather modification experiments and commercial seeding operations.
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From page 40... ...
STATISTICAL EVALUATION To have reasonable confidence in the results of seeding experiments they must be carefully designed, conducted, and analyzed with the best techniques available. The goal is to minimize uncertainties resulting from the large variability in natural weather systems, from our incomplete knowledge of the physical processes involved, frown our limited ability to measure the relevant meteorological variables and to target seeding agents, and from our inability to replicate experiments (in the strictest sense of the word)
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From page 41... ...
These experiments have provided a large fraction of our scientific data on clouds and storms, but most did not provide evidence sufficient to reject the null hypothesis of no seeding effect. A conclusion commonly reached in these experiments was that "there were indications of seeding effects based ore physical measurements' but the data were not sufficient to reach statistical conclusions." Generally the suggested physical evidence tor seeding effects was deduced frown after-the-fact examination of the data.
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From page 42... ...
For instance, experiments aimed at increasing rainfall typically have used networks of surface-~ain gauges as their measurement system Rain gauges give a fairly accurate measurement of rain at the point of the gauge, but rain is highly variable in space and time, especially in convective weather situations. The frequency distribution of storm rainfall amounts is highly skewed, with a large number of small events interspersed with a small number of large events that account for most of the total lain.
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From page 43... ...
However, recent advances in this area integrating several observational tools could help to address these issues (Mueller et al., 2003~. A variety of tracking methods and software packages are used to evaluate the results of seeding activities For example, the South African and Mexican hyg~oscopic seeding experiments (WMO, 2000)
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From page 44... ...
For example, in recent large particle hydroscopic seeding trials involving war-base convective clouds in Thailand and Texas, increases in rain were reported 3 to 12 hours after seeding was conducted' well beyond the time at which direct effects of seeding were expected and possibly outside the target area. In Project Whitetop the seeding appears to have decreased rain in the area immediately downwind of the seeding release line.
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