Cloud Seeding and Weather Modification Questions and Answers

Answer: A

Correct answer: adding embryos divides the water among more and smaller stones

This is the beneficial competition hypothesis, and it is the only one of the four that is physically coherent. Seeding cannot melt stones, cannot remove an updraught, and certainly cannot prevent ice forming in a storm that is already producing hail.

Answer: B

The first two are correct and reflect the assessments of national bodies. The third is not supported, and several major trials found no statistically significant reduction. National assessments have remained cautious throughout.

Answer: C

Supercooled fog can be seeded to glaciate and clear, whereas warm fog offers no such lever. Dispersing warm fog requires heating or mechanical mixing and is correspondingly expensive. Only a few major airports have ever operated such systems.

Answer: D

Seeding converts the droplets to ice crystals which grow and settle out, opening a hole. The technique is well established and is among the few uncontested successes of weather modification. The result is visible within minutes at the site.

Answer: A

Both are true and the reason gives why it convinces, and no statistical inference over many events is required. Rain enhancement offers no comparable directness of evidence. Fog dispersal needs no statistical inference at all.

Answer: B

Nothing in the technology acts on the large scale circulation, which carries energy far beyond any seeding intervention. The other three are the standard operational objectives. All three act locally on cloud rather than on circulation.

Answer: C

There is no way to know what a seeded cloud would have done had it been left alone. Only randomised comparison over many events can address the question, and natural variability is large. The effect sought is small against that background.

Answer: D

Both are true and the reason gives the statistical problem, and single case comparisons are worthless in consequence. Even randomised trials often require many seasons to reach a useful conclusion. Sample size is the binding constraint on such work.

Answer: A

The first two are correct and are standard trial design. The third is precisely the fallacy that has sustained unfounded claims, since a single cloud provides no counterfactual whatever. One case can never establish a causal effect.

Answer: B

Correlating the two areas before the trial allows natural variation to be partly removed. The design still requires randomisation, since the correlation alone does not establish causation. Design and randomisation must work together.