Cloud Electrification and Lightning Questions and Answers

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.