DGCA Meteorology: Stability & Instability Questions
60 exam-style Stability & Instability questions for the DGCA Meteorologypaper (CPL & ATPL). The first 12 are free below with answers and explanations — sign up free to practise all of them with progress tracking.
- Q1
The difference between Environmental Lapse Rate (ELR) and Saturated Adiabatic Lapse Rate (SALR) in moist air is:
- ALeast
- BGreater
- CEqual
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Correct answer: A. Least
SALR is lower than ELR in moist air because condensation adds heat, slowing the cooling rate.
- Q2
Latent heat released during adiabatic ascent of saturated air makes the air:
- AWarmer than dry ascent
- BCooler than dry ascent
- CUnaffected
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Correct answer: A. Warmer than dry ascent
Condensation releases heat, so saturated air cools slower than dry air when rising.
- Q3
Inversion in the atmosphere indicates
- AStability
- BInstability
- CNeutral
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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.
- Q4
Characteristics of a stable air mass include:
- AStrong convection and turbulence
- BSmooth air, poor visibility, stratiform clouds
- CRapid 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.
- Q5
If SALR = DALR = ELR, then the air is said to be:
- AAbsolutely stable
- BNeutrally / indifferently stable
- CAbsolutely 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.
- Q6
On a warm sunny day in temperate latitudes, weather is generally influenced by:
- AFrontal rain
- BConvective turbulence and fair weather cumulus clouds
- CFog
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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.
- Q7
Dry air is unstable when:
- AELR=DALR
- BELR<DALR
- CELR>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.
- Q8
Which types of clouds are typical evidence of stable air conditions?
- ACB, CC
- BST, AS
- CCU, 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.
- Q9
Dry air is unstable when:
- AELR=DALR
- BELR>DALR
- CELR<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.
- Q10
An air mass is called stable when
- Athe environmental lapse rate is high, with little vertical motion of air currents
- Bthe temperature in a given air mass decreases rapidly with height
- Cthe 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.
- Q11
If the ELR is 0.65°C/100m
- AAtmosphere is conditionally stable
- BAtmosphere is absolutely stable
- CAtmosphere is absolutely unstable
- DAtmosphere 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
- ANeutral when dry
- BAbsolute stability
- CAbsolute instability
- DConditional stability
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Correct answer: A. Neutral when dry
This Explanation is Coming Soon
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