DGCA Meteorology: Stability & Instability Questions
60 exam-style Stability & Instability questions for the DGCA Meteorology paper (CPL · ATPL · PPL). The first 12 are free below with answers and explanations — sign up free to practise all of them with progress tracking.
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Q1
The difference between Environmental Lapse Rate (ELR) and Saturated Adiabatic Lapse Rate (SALR) in moist air is:
- A Least
- B Greater
- C Equal
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Correct answer: A. Least
SALR is lower than ELR in moist air because condensation adds heat, slowing the cooling rate.
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Q2
Latent heat released during adiabatic ascent of saturated air makes the air:
- A Warmer than dry ascent
- B Cooler than dry ascent
- C Unaffected
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Correct answer: A. Warmer than dry ascent
Condensation releases heat, so saturated air cools slower than dry air when rising.
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Q3
Inversion in the atmosphere indicates
- A Stability
- B Instability
- C Neutral
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Correct answer: A. Stability
An inversion, where temperature rises with height, indicates strong stability: any parcel displaced upward becomes colder and denser than its surroundings and sinks back, suppressing vertical motion.
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Q4
Characteristics of a stable air mass include:
- A Strong convection and turbulence
- B Smooth air, poor visibility, stratiform clouds
- C Rapid uplift and showers
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Correct answer: B. Smooth air, poor visibility, stratiform clouds
Stable air stays calm, forms flat clouds, and often brings fog or low visibility.
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Q5
If SALR = DALR = ELR, then the air is said to be:
- A Absolutely stable
- B Neutrally / indifferently stable
- C Absolutely unstable
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Correct answer: B. Neutrally / indifferently stable
When lapse rates match, air parcels don’t rise or sink—they’re neutral.
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Q6
On a warm sunny day in temperate latitudes, weather is generally influenced by:
- A Frontal rain
- B Convective turbulence and fair weather cumulus clouds
- C Fog
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Correct answer: B. Convective turbulence and fair weather cumulus clouds
Warm days heat the ground, creating thermals and puffy cumulus clouds.
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Q7
Dry air is unstable when:
- A ELR=DALR
- B ELR<DALR
- C ELR>DALR
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Correct answer: C. ELR>DALR
Dry (unsaturated) air is unstable when the environmental lapse rate exceeds the dry adiabatic lapse rate: a lifted parcel cooling at the DALR then remains warmer than its surroundings and continues to rise.
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Q8
Which types of clouds are typical evidence of stable air conditions?
- A CB, CC
- B ST, AS
- C CU, CB
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Correct answer: B. ST, AS
Stratus and altostratus are layer clouds formed by gentle, widespread lifting in stable air; cumulus and cumulonimbus, by contrast, indicate convective instability.
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Q9
Dry air is unstable when:
- A ELR=DALR
- B ELR>DALR
- C ELR<DALR
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Correct answer: B. ELR>DALR
Unsaturated air is unstable when the environmental lapse rate is greater than the dry adiabatic lapse rate, since a rising parcel cooling at the DALR then stays warmer and more buoyant than its environment.
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Q10
An air mass is called stable when
- A the environmental lapse rate is high, with little vertical motion of air currents
- B the temperature in a given air mass decreases rapidly with height
- C the vertical motion of rising air tends to become weaker and disappears
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Correct answer: C. the vertical motion of rising air tends to become weaker and disappears
An air mass is stable when vertical displacements are damped: rising air quickly becomes cooler and denser than its surroundings, so its upward motion weakens and disappears. A rapid decrease of temperature with height would instead indicate instability.
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Q11
If the ELR is 0.65°C/100m
- A Atmosphere is conditionally stable
- B Atmosphere is absolutely stable
- C Atmosphere is absolutely unstable
- D Atmosphere is stable when dry
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Correct answer: D. Atmosphere is stable when dry
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Q12
ELR is 1°C/100m
- A Neutral when dry
- B Absolute stability
- C Absolute instability
- D Conditional stability
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Correct answer: A. Neutral when dry
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