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- Total number of questions : 20
- Time allotted : 30:00 Minutes:Seconds.
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Cloud Physics [ Question No: 1 To 20 ] :
Cloud made solely of liquid water droplets are termed as :
A cloud with abundant natural ice nuclei is a poor seeding candidate because
Microwave radiometers are used in seeding programmes to
State whether the following is true or false.
Releasing silver iodide into cloud warmer than about minus four degrees achieves little.
Silver iodide flares release nuclei in numbers of the order of how many per gram of agent?
Three of the following are genuine obstacles to demonstrating a seeding effect. Which is the odd one out?
Assertion (A): Randomised trials are necessary to evaluate seeding.
Reason (R): The natural variability of rainfall greatly exceeds any plausible seeding effect.
All of the following are recognised lightning safety measures EXCEPT
Assertion (A): Lightning is far more frequent over land than over the ocean.
Reason (R): Land heats rapidly and supports the vigorous updraughts that charging requires.
Lightning contributes to the nitrogen cycle by
State whether the following is true or false.
Thunder is rarely heard more than about 25 kilometres from the flash.
Consider the following statements about ice accretion.
1. Glaze is dense and clear because the water freezes slowly.
2. Rime is opaque because air is trapped as droplets freeze fast.
3. Rime is denser and more damaging than glaze.
Assertion (A): A gamma distribution is often preferred to a pure exponential for raindrop spectra.
Reason (R): The extra shape parameter represents the observed shortage of the very smallest drops.
The drop size distribution of rain is most commonly represented by
The autoconversion threshold in older bulk schemes represents
A two moment scheme is preferred over a one moment scheme when the question concerns
Assertion (A): Collection growth accelerates as a collector drop enlarges, unlike condensation.
Reason (R): Both the swept volume and the difference in fall speed increase with the collector size.
Three of the following appear in the diffusional growth equation for a droplet. Which is the odd one out?
Three of the following are genera of the low étage. Which is the odd one out?
Assertion (A): The saturated adiabatic lapse rate is not a single fixed number.
Reason (R): The amount of latent heat released depends on how much vapour the air holds at that temperature.
Total number of questions : 20
Number of answered questions : 0
Number of unanswered questions : 20
Cloud Physics [ Question No: 1 To 20 ] :
Cloud made solely of liquid water droplets are termed as :
Your Answer : (Not Answered)
Correct Answer : C
Clouds made only of liquid droplets are warm clouds.
In cloud physics a warm cloud lies wholly at temperatures above 0°C, so it contains only liquid water, and its rain forms by collision and coalescence of droplets. Clouds that reach below freezing are cold clouds, where ice crystals grow at the expense of supercooled droplets (the Bergeron-Findeisen process).
An ice cloud, such as cirrus, is made of ice crystals; a mixed phase cloud holds both supercooled water and ice; and 'cold cloud' is the general name for clouds with ice processes. None of these is made solely of liquid water.
A cloud with abundant natural ice nuclei is a poor seeding candidate because
Your Answer : (Not Answered)
Correct Answer : C
Additional nuclei add nothing where the cloud is already converting its water. Seeding is only plausible where the natural nucleus supply is the limiting factor. Where something else limits the cloud, nuclei cannot help.
Microwave radiometers are used in seeding programmes to
Your Answer : (Not Answered)
Correct Answer : D
Correct answer: measure the supercooled liquid water available in the cloud
A radiometer looking upward measures the liquid water in the column overhead, which is the resource seeding is meant to convert. If there is none, there is nothing to seed and the operation should not run - so the instrument answers both the targeting question and the go or no-go decision.
State whether the following is true or false.
Releasing silver iodide into cloud warmer than about minus four degrees achieves little.
Your Answer : (Not Answered)
Correct Answer : D
Correct answer: True
Above about −4 or −5 degrees the agent nucleates almost nothing, so releasing it there accomplishes nothing whatever. Seeding requires the target volume to be colder than the agent’s threshold, which is why the vertical temperature structure of the cloud must be known before an operation.
Silver iodide flares release nuclei in numbers of the order of how many per gram of agent?
Your Answer : (Not Answered)
Correct Answer : B
A single gram yields an enormous number of active nuclei at suitable temperatures. This is why the mass of agent required for a large operation remains comparatively modest. A few kilograms can treat a substantial cloud volume.
Three of the following are genuine obstacles to demonstrating a seeding effect. Which is the odd one out?
Your Answer : (Not Answered)
Correct Answer : D
Precipitation can be measured perfectly adequately by gauge and radar. The other three are the genuine difficulties that make evaluation so hard. Measurement itself is not among the problems. Gauges and radar are entirely adequate for the task.
Assertion (A): Randomised trials are necessary to evaluate seeding.
Reason (R): The natural variability of rainfall greatly exceeds any plausible seeding effect.
Your Answer : (Not Answered)
Correct 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.
All of the following are recognised lightning safety measures EXCEPT
Your Answer : (Not Answered)
Correct Answer : C
A tall isolated tree is among the most likely strike points and side flash is a serious risk. The other three each reduce the chance of being on the discharge path. Substantial buildings and vehicles are the safest places.
Assertion (A): Lightning is far more frequent over land than over the ocean.
Reason (R): Land heats rapidly and supports the vigorous updraughts that charging requires.
Your Answer : (Not Answered)
Correct Answer : B
Correct answer: Both A and R are true, and R is the correct explanation of A
Both are true and the reason gives the mechanism. Land has a low heat capacity and warms quickly in the sun, driving strong surface heating and the vigorous updraughts that carry supercooled water above the freezing level. The sea warms slowly and its surface temperature varies little through the day, so oceanic convection is generally weaker and the lightning rate lower by a factor of ten.
Lightning contributes to the nitrogen cycle by
Your Answer : (Not Answered)
Correct Answer : C
The extreme channel temperature allows nitrogen and oxygen to combine. The resulting oxides are a significant natural source in the upper troposphere, where few other sources operate. It matters directly to ozone chemistry at those levels.
State whether the following is true or false.
Thunder is rarely heard more than about 25 kilometres from the flash.
Your Answer : (Not Answered)
Correct Answer : C
Refraction of sound upward by the temperature profile limits the range. Beyond that distance the flash is seen but not heard, which is the origin of the term heat lightning. No separate physical phenomenon is involved at all.
Consider the following statements about ice accretion.
1. Glaze is dense and clear because the water freezes slowly.
2. Rime is opaque because air is trapped as droplets freeze fast.
3. Rime is denser and more damaging than glaze.
Your Answer : (Not Answered)
Correct Answer : D
Correct answer: 1 and 2 only
Statements 1 and 2 are correct: slow freezing lets air escape and gives glaze its clear, dense structure, while the rapid freezing of individual droplets traps air and makes rime opaque and light. Statement 3 reverses the comparison - glaze is the denser and by far the more damaging of the two, precisely because it is solid ice rather than an aerated deposit.
Assertion (A): A gamma distribution is often preferred to a pure exponential for raindrop spectra.
Reason (R): The extra shape parameter represents the observed shortage of the very smallest drops.
Your Answer : (Not Answered)
Correct Answer : D
Both are true and the reason gives the improvement, and the exponential form overpredicts small drops. The additional parameter must itself be estimated, which is the cost of the better fit. Extra parameters need extra observations to constrain them.
The drop size distribution of rain is most commonly represented by
Your Answer : (Not Answered)
Correct Answer : C
The Marshall Palmer form expresses drop number as decaying exponentially with diameter. Gamma distributions with an extra shape parameter are now often preferred for their greater flexibility. The choice of form affects the derived rainfall appreciably.
The autoconversion threshold in older bulk schemes represents
Your Answer : (Not Answered)
Correct Answer : A
It is a crude representation of the requirement that some droplets reach collector size. Modern formulations replace the sharp threshold with a smooth dependence on droplet number and water content. The smooth forms behave far better in a numerical model.
A two moment scheme is preferred over a one moment scheme when the question concerns
Your Answer : (Not Answered)
Correct Answer : B
Aerosol acts through droplet number, which a one moment scheme does not carry as a variable. Without it the scheme cannot represent the indirect effects at all. Droplet number is the variable through which aerosol acts.
Assertion (A): Collection growth accelerates as a collector drop enlarges, unlike condensation.
Reason (R): Both the swept volume and the difference in fall speed increase with the collector size.
Your Answer : (Not Answered)
Correct Answer : C
Correct answer: Both A and R are true, and R is the correct explanation of A
Both are true and the reason gives the mechanism. A larger collector sweeps a wider path and falls faster relative to the droplets it meets, so its rate of collection accelerates as it grows. Condensation does the opposite: the same vapour flux spread over a larger surface makes the radius grow ever more slowly, which is why condensation alone cannot produce rain.
Three of the following appear in the diffusional growth equation for a droplet. Which is the odd one out?
Your Answer : (Not Answered)
Correct Answer : C
Collision efficiency belongs to the coalescence problem and has no place in the diffusional treatment. The other three each appear directly as terms in the growth expression. Diffusion of vapour and conduction of heat are the two limiting processes.
Three of the following are genera of the low étage. Which is the odd one out?
Your Answer : (Not Answered)
Correct Answer : D
Altocumulus belongs to the middle étage as its prefix indicates. The other three all have bases typically below two kilometres and are conventionally grouped together. The prefix is a reliable guide to the étage in almost every case.
Assertion (A): The saturated adiabatic lapse rate is not a single fixed number.
Reason (R): The amount of latent heat released depends on how much vapour the air holds at that temperature.
Your Answer : (Not Answered)
Correct Answer : A
Correct answer: Both A and R are true, and R is the correct explanation of A
Both are true and the reason gives the cause. The saturated rate is the dry rate offset by the latent heat released as vapour condenses, and warm saturated air holds far more vapour than cold, so it releases far more heat per unit of lifting. The rate is therefore about 4 degrees per kilometre in warm tropical air and approaches the dry 9.8 in very cold air, where there is almost nothing left to condense.
Marks
Total number of questions : 20
Number of answered questions : 0
Number of unanswered questions : 20