Cloud Electrification and Lightning Questions and Answers

Q: The main negative charge centre in a mid-latitude summer thunderstorm typically lies at a height of about

Correct answer: 6 kilometresThe main negative centre sits near the minus 10 to minus 20 degree level, which in a mid-latitude summer storm is around 6 km. Because it is fixed by temperature rather than by height, it lies lower in winter storms and at higher latitudes and higher in the deep tropics - a shift with real consequences, since a low charge centre is what makes winter positive flashes so powerful.

Q: Consider the following statements about lightning and storm evolution.1. A lightning jump can precede severe weather at the surface.2. A sudden cessation may indicate updraught collapse.3. Flash rate bears no relation to updraught strength.

Correct answer: 1 and 2 onlyStatements 1 and 2 are correct and are used operationally: a lightning jump precedes severe weather, and a cessation warns of updraught collapse. Statement 3 contradicts both - the flash rate is closely tied to updraught strength, since it is the updraught that lifts the supercooled water and graupel on which charging depends. That relation is exactly what makes total lightning useful for nowcasting.

Q: State whether the following is true or false.A cloud that never reaches the freezing level does not produce lightning.

Correct answer: TrueThe dominant charging mechanism requires collisions between graupel and ice crystals in the presence of supercooled water, so a cloud that stays entirely above freezing has no ice and no way of separating charge on the scale required. Warm rain clouds produce rain in quantity and no lightning, which is why the freezing level is the first thing looked for in assessing a cloud’s electrical potential.

Q: Arrange these stages of thunderstorm electrification in order.1. gravity and the updraught separate the charge vertically2. the updraught carries liquid water above the freezing level3. the field grows until breakdown initiates a flash4. graupel and ice crystals collide and exchange charge

Correct answer: 2 - 4 - 1 - 3The updraught first carries liquid water above the freezing level, so that supercooled droplets and growing graupel are present together. Collisions between graupel and ice crystals then exchange charge. Gravity and the updraught separate the two populations vertically, the heavy graupel falling and the light crystals rising, which builds the charge centres. And the field grows until breakdown initiates a flash.

81.

Assertion (A): Free ions alone cannot account for thunderstorm charge separation.
Reason (R): Their mobility is far too low to transport charge over kilometres in the time available.

A.Both A and R are true, and R is the correct explanation of A
B.Both A and R are true, but R is not the correct explanation of A
C.A is true but R is false
D.A is false but R is true

Answer: A

Both are true and the reason gives the objection, and hydrometeors moving bodily do the work instead. This is why the microphysics of the mixed phase region matters so much to electrification. Microphysics and electricity are inseparable here.

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82.

The main negative charge centre in a mid-latitude summer thunderstorm typically lies at a height of about

A.30 kilometres
B.6 kilometres
C.1 kilometre
D.15 kilometres

Answer: B

Correct answer: 6 kilometres

The main negative centre sits near the minus 10 to minus 20 degree level, which in a mid-latitude summer storm is around 6 km. Because it is fixed by temperature rather than by height, it lies lower in winter storms and at higher latitudes and higher in the deep tropics - a shift with real consequences, since a low charge centre is what makes winter positive flashes so powerful.

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83.

A lightning flash rate that suddenly falls to zero in a severe storm may indicate

A.an instrument failure at the sensor and nothing more
B.that the storm has just begun to produce hail
C.that the updraught has collapsed and a downburst may follow
D.that the storm is about to intensify very sharply

Answer: C

Correct answer: that the updraught has collapsed and a downburst may follow

Electrification requires an updraught vigorous enough to keep supercooled water and graupel aloft, so when the flash rate stops abruptly the updraught has failed. What was being supported then falls, and the resulting downdraught can reach the surface as a damaging downburst within minutes. Both the sudden rise and the sudden cessation of the flash rate are therefore operationally significant, in opposite ways.

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84.

Consider the following statements about lightning and storm evolution.
1. A lightning jump can precede severe weather at the surface.
2. A sudden cessation may indicate updraught collapse.
3. Flash rate bears no relation to updraught strength.

A.3 only
B.1 only
C.All of them
D.1 and 2 only

Answer: D

Correct answer: 1 and 2 only

Statements 1 and 2 are correct and are used operationally: a lightning jump precedes severe weather, and a cessation warns of updraught collapse. Statement 3 contradicts both - the flash rate is closely tied to updraught strength, since it is the updraught that lifts the supercooled water and graupel on which charging depends. That relation is exactly what makes total lightning useful for nowcasting.

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85.

Lightning is more frequent in continental than in maritime convection chiefly because

A.continental updraughts are stronger and support more graupel
B.maritime clouds contain no ice crystals whatsoever
C.the sea water beneath conducts the charge away
D.salt particles in the air prevent charge separation

Answer: A

Higher droplet concentrations and stronger updraughts carry more liquid water above the freezing level. The resulting graupel production is what drives the non-inductive charging. Aerosol and dynamics both contribute to the contrast.

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86.

Assertion (A): Aerosol loading can influence the lightning activity of a storm.
Reason (R): More numerous droplets carry more liquid water above the freezing level for riming.

A.A is false but R is true
B.Both A and R are true, and R is the correct explanation of A
C.Both A and R are true, but R is not the correct explanation of A
D.A is true but R is false

Answer: B

Both are true and the reason gives the microphysical link, and increases downwind of cities have been reported. Disentangling the aerosol effect from the meteorology remains difficult. Urban lightning anomalies have been reported repeatedly.

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87.

All of the following are required for a thunderstorm to electrify EXCEPT

A.graupel and ice crystals colliding
B.an updraught to separate the charged particles
C.a cloud top warmer than the freezing level
D.supercooled liquid water in the mixed phase region

Answer: C

A cloud whose top is warmer than freezing contains no ice and cannot charge by this mechanism. The other three are the accepted requirements. Warm clouds do not produce lightning of any consequence. Ice is indispensable to the charging mechanism.

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88.

State whether the following is true or false.
A cloud that never reaches the freezing level does not produce lightning.

A.False
B.True only at large scales
C.False only at small scales
D.True

Answer: D

Correct answer: True

The dominant charging mechanism requires collisions between graupel and ice crystals in the presence of supercooled water, so a cloud that stays entirely above freezing has no ice and no way of separating charge on the scale required. Warm rain clouds produce rain in quantity and no lightning, which is why the freezing level is the first thing looked for in assessing a cloud’s electrical potential.

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89.

Arrange these stages of thunderstorm electrification in order.
1. gravity and the updraught separate the charge vertically
2. the updraught carries liquid water above the freezing level
3. the field grows until breakdown initiates a flash
4. graupel and ice crystals collide and exchange charge

A.2 - 4 - 1 - 3
B.3 - 1 - 4 - 2
C.4 - 2 - 1 - 3
D.2 - 1 - 4 - 3

Answer: A

Correct answer: 2 - 4 - 1 - 3

The updraught first carries liquid water above the freezing level, so that supercooled droplets and growing graupel are present together. Collisions between graupel and ice crystals then exchange charge. Gravity and the updraught separate the two populations vertically, the heavy graupel falling and the light crystals rising, which builds the charge centres. And the field grows until breakdown initiates a flash.

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90.

The polarity of charge acquired by graupel in a collision depends on

A.the time of day at which the collision occurs
B.the temperature and how much liquid water surrounds it
C.the size of the graupel particle and nothing else
D.the strength of the electric field already present

Answer: B

Correct answer: the temperature and how much liquid water surrounds it

Laboratory work shows the sign of the transfer depending on both temperature and liquid water content, with a reversal boundary in that two-dimensional space rather than a single reversal temperature. Higher liquid water content shifts the reversal to colder temperatures. Particle size and the ambient field affect the magnitude but not the sign, which is what makes the mechanism non-inductive.

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