Consider the following characteristics of a cloud type : 1. They are born through convection. 2. Only cloud type that can produce hail, thunder and lightning. 3. They are large cauliflower-shaped towers, often ‘anvil tops’. Identify the type of cloud on the basis of the given characteristics.
- (a)Stratocumulus
- (b)Cumulonimbus
- (c)Cirrocumulus
- (d)Nimbostratus
Correct — B, Cumulonimbus. Each of the three descriptions is a cumulonimbus signature. It is a convective cloud: warm moist air rises in strong buoyant currents, water vapour condenses as it climbs, and the cloud builds upward rather than spreading sideways. That vertical growth gives the cauliflower-like towers, and when the top reaches the stable air near the tropopause it can rise no further and spreads out into the flat anvil the third description names. And it is the only cloud that produces hail, thunder and lightning, because you need the deep updraught, the mixture of supercooled water and ice, and the charge separation that comes with them — a mature cumulonimbus can stand twelve to twenty kilometres tall and deliver hail, squalls, flash flooding and, in the worst cases, tornadoes.
- (a)Stratocumulus — A low, lumpy sheet of cloud with almost no vertical development. It may give drizzle, but it never builds the tower, the anvil or the electrical activity described here.
- (c)Cirrocumulus — A high, thin, rippled ice cloud. It is far too shallow and too cold to hold the deep updraughts that hail and lightning require.
- (d)Nimbostratus — The steady-rain cloud — a thick, featureless grey layer that gives continuous precipitation. It lacks both the cauliflower towers and the thunder; that layered structure is the giveaway against a convective tower.
Clouds are classified by height and by form, and cumulonimbus is the extreme of the vertically developed family. It needs three things at once — moisture, an unstable air mass and something to lift the air. The lower part is water droplets, the upper part ice crystals, and the anvil top forms where wind shear or an inversion at the equilibrium level stops the rise and spreads the cloud sideways.
The item is really a check on whether you can read a cloud description backwards. Statement 2 alone would settle it, because hail, thunder and lightning together belong to one cloud only. Statement 3 confirms it, since the anvil is the visual marker no other cloud in the list can show. The commonest error is picking nimbostratus, because the 'nimb-' in the name signals rain to a candidate scanning quickly — but nimbostratus is a layer cloud that gives steady, quiet rain, while cumulonimbus is a tower that gives violent, short-lived rain with electricity in it. Reading the names as built pieces helps: cumulus for the heap, nimbus for rain, stratus for the layer.
- Cumulonimbus forms by convection and requires moisture, an unstable air mass and a lifting mechanism.
- Mature cumulonimbus can extend from near the surface to between 12,000 and 20,000 metres.
- The flat anvil top forms at the equilibrium level near the tropopause, where wind shear or an inversion halts the rise.
- It is the only cloud that produces hail, thunder and lightning, and it can also spawn tornadoes and flash floods.
- Nimbostratus, by contrast, is a layer cloud associated with continuous, steady precipitation and no lightning.
- Choosing nimbostratus because 'nimbus' suggests rain; it gives steady rain but no thunder or hail.
- Reading 'cauliflower' as describing any cumulus — the anvil is what marks the mature cumulonimbus.
- Assuming height alone identifies a cloud; cumulonimbus spans low to high levels in one body.
As a description-to-cloud identification, as a direct question on which cloud brings thunder and hail, or as a match-the-cloud-to-the-precipitation item.
During a thunderstorm, the thunder in the skies is produced by the 1. Meeting of cumulonimbus clouds in the sky 2. Lightning that separates the nimbus clouds 3. Violent upward movement of air and water particles. Select the correct answer using the codes given below.
- (a) 1 only
- (b) 2 and 3
- (c) 1 and 3
- (d) None of the above produces the thunder
Answer(d) None of the above produces the thunder
The same cloud, one step deeper. CDS asks you to name the cloud that brings thunder; UPSC asks what actually makes the sound — the sudden expansion of air heated by the lightning stroke, not the clouds colliding.
Which one of the following types of cloud is characterized by continuous precipitation?
- (a) Cirrocumulus
- (b) Cumulus
- (c) Nimbostratus
- (d) Cumulonimbus
Answer(c) Nimbostratus
The mirror image of this question, and it separates the pair that trips most candidates. Nimbostratus gives the long steady rain; cumulonimbus gives the short violent storm with hail and lightning.
- practice — not a real PYQ
The flat 'anvil' top of a mature thunderstorm cloud forms because
- (a)the cloud has run out of water vapour
- (b)the rising air reaches a stable layer near the tropopause and spreads sideways
- (c)hail falling from the cloud flattens its top
- (d)sunlight evaporates the upper part of the cloud
Answer(b) the rising air reaches a stable layer near the tropopause and spreads sideways — wind shear or an inversion at the equilibrium level stops the vertical growth.
- practice — not a real PYQ
Continuous, steady precipitation over several hours without thunder is most typically associated with which one of the following clouds?
- (a)Cumulonimbus
- (b)Cirrus
- (c)Nimbostratus
- (d)Altocumulus
Answer(c) Nimbostratus — a thick layer cloud that gives prolonged steady rain, unlike the short violent downpours of a cumulonimbus.