Kinetic energy of a hailstone scales approximately with which power of its diameter?
Answer: A
Mass scales as the cube and impact speed roughly as the square root of diameter, so energy goes roughly as the fourth to fifth power. This steep dependence is why size matters so much for damage. Doubling the diameter multiplies the energy many times over.
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Rocket and artillery delivery of seeding agent is used chiefly for
Answer: B
A developing hail cell requires agent delivered within minutes, faster than aircraft can respond. The practice is common in parts of Europe and Asia and rare elsewhere. Regulation of ground launched rockets varies widely.
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State whether the following is true or false.
Aircraft delivery is often too slow for hail suppression in a rapidly developing cell.
Answer: C
Correct answer: True
A hail-producing cell may develop from first echo to damaging stones in twenty or thirty minutes, and an aircraft must be tasked, must reach the cell and must seed the right part of it within that window. Ground generators and rockets are used instead where the response time matters, at the cost of poorer targeting.
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All of the following are used to deliver seeding agent EXCEPT
Answer: D
Agent placed in surface water cannot reach the cloud at all. The other three are the standard delivery methods in operational use. The agent must reach the cloud to do anything at all. Surface water is not connected to the cloud in any way.
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The overall scientific consensus on operational rain enhancement is best described as
Answer: A
Assessments consistently find the physical basis sound but the operational demonstration weak. Orographic winter seeding is the application with the strongest supporting evidence. Physical plausibility and demonstration are not the same.
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Assertion (A): The physical basis of seeding is better established than its operational effectiveness.
Reason (R): Laboratory and plume studies confirm the microphysics that field trials struggle to demonstrate.
Answer: B
Both are true and the reason gives the gap between the two, and delivery and evaluation account for much of it. A sound mechanism does not guarantee a measurable operational result. Delivery and evaluation account for much of the gap.
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Among the following substances, which is commonly used for cloud seeding :
MH SET - 2018, SET Exam - 2018,
Answer: A
The substance commonly used is Silver Iodide.
Cloud seeding supplies nuclei on which supercooled droplets can freeze. Silver iodide has a crystal structure very close to that of ice, so it acts as an efficient ice nucleus at temperatures of only a few degrees below freezing. Dry ice and hygroscopic salts such as sodium chloride are also used.
Sand is not an effective nucleus. Black carbon is a pollutant from incomplete combustion, and copper sulphate is not used for seeding clouds.
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The idea in cloud seeding experiment is to find clouds that have too low a ratio of ice crystals to droplets and then to add enough artificial ice nuclei to reach the ratio of crystals to droplets of about ................ for producing precipitation.
MH SET - 2021, SET Exam - 2021,
Answer: B
The target ratio is about 1 : 1,00,000, one ice crystal to 100,000 droplets.
Cold-cloud seeding relies on the Wegener-Bergeron-Findeisen process: ice crystals grow at the expense of supercooled droplets because the saturation vapour pressure over ice is lower than over water. If there are too few ice crystals the cloud stays supercooled; if there are too many they share the vapour and stay small. Seeding aims at about one crystal per hundred thousand droplets, enough crystals to grow large enough to fall.
Ratios of 1 : 10, 1 : 500 or 1 : 1000 would overseed the cloud, producing many small crystals that do not grow to precipitation size.
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