Avielevate / DGCA CPL papers / Aviation Meteorology
DGCA CPL Aviation Meteorology — question bank and syllabus
The atmosphere you work in: ISA and temperature, pressure and altimetry, humidity and stability, winds, clouds, thunderstorms, fog and visibility, air masses and fronts, and reading the actual reports.
What is in this paper
Every chapter we cover for Aviation Meteorology, with how many questions sit behind each one.
These counts come straight out of the question bank and are regenerated whenever it changes —
they are not a claim, they are what is there today.
Sample questions, answered and explained
A few real questions from this paper, with the answer marked and the reasoning
written out — the same explanations you get inside the app. Everything else is behind a free
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030040 · Humidity and Stability
Which instrument is used to measure the humidity of the air?
- Ahydrometer
- Bhygrometer
- Cwet bulb thermometer
- Dhygroscope
Why that is the answer
A hygrometer is the general term for an instrument designed specifically to measure atmospheric humidity - this includes types such as the hair hygrometer (using the expansion/contraction of human hair with moisture content), electronic capacitance sensors, and the wet-and-dry bulb (psychrometer) arrangement, all of which fall under the broad category of hygrometers used to determine humidity. Option a, a hydrometer, is a completely different instrument used to measure the density or specific gravity of liquids (e.g., battery acid, aircraft fuel) and has nothing to do with air humidity. Option c, a wet bulb thermometer, is only one component of a psychrometer (used alongside a dry bulb thermometer to derive humidity via the difference in readings) - it is a temperature-measuring device on its own, not a complete humidity-measuring instrument by itself. Option d, 'hygroscope', is not the standard recognised instrument name for measuring humidity (hygroscopic refers to a substance's tendency to absorb moisture). The correct, standard term for the humidity-measuring instrument is hygrometer, option b.
- Hygrometer = general instrument category for measuring humidity (hair, capacitance, psychrometer-based).
- Hydrometer measures liquid density, unrelated to air humidity.
- Wet bulb thermometer is only one part of a psychrometer, not a full humidity instrument.
- Correct instrument name is hygrometer - option b.
030048 · Pressure and Altimetry
If air is diverging at upper levels, what would you expect at the surface?
- ARising pressure with clearing skies
- BRising pressure with cloud forming
- CFalling pressure with clearing skies
- DFalling pressure with cloud forming
Why that is the answer
Divergence in the upper atmosphere means air is being carried away faster than it arrives, so mass is removed from the top of the column above that point. Removing mass aloft reduces the weight of the overlying air, so surface pressure FALLS. To replace the departing air, the atmosphere responds with rising motion beneath the divergence, so surface air ascends and converges into the developing low. Ascending air cools adiabatically toward its dew point, so cloud FORMS and weather deteriorates. This upper-divergence-over-surface-convergence coupling is the classic mechanism for surface low deepening. Options a and b are wrong because they predict a pressure rise, which requires upper convergence, not divergence. Option c correctly gives falling pressure but wrongly has cloud dissipating; rising air makes cloud, not clears it. The answer is d, fall in pressure with cloud forming.
- Upper divergence removes mass from the column
- Less mass overhead means surface pressure falls
- Rising air replaces the departing air
- Ascending air cools, forming cloud
- Answer is d, fall in pressure with cloud forming
030089 · Clouds and Precipitation
Which of the following returns a radar echo?
- AFog
- BHail
- CCloud
- DMist
Why that is the answer
Weather radar (and ATC surveillance radar 'weather clutter') detects precipitation primarily by backscatter from relatively large water/ice particles — the radar reflectivity of a target scales strongly with the sixth power of particle diameter (per the Rayleigh scattering approximation), so large particles like hailstones return a very strong radar echo. Hail, being composed of large, dense ice particles, is one of the strongest radar reflectors found in the atmosphere, which is precisely why weather radar is used operationally to detect and avoid severe convective cells containing hail. Fog (a) and mist (d) consist of very small water droplets whose diameters are far too small to reflect appreciable radar energy at typical weather-radar wavelengths, making them essentially radar-transparent. Plain cloud (c) without precipitation-sized droplets similarly returns little to no significant echo, since cloud droplets are also very small compared to raindrops or hailstones. Hail's large particle size therefore gives by far the strongest reflected radar return among the options, making b correct.
- Radar reflectivity depends strongly on particle size (~diameter^6, Rayleigh scattering)
- Hailstones are large, dense ice particles producing very strong echoes
- Fog and mist consist of tiny droplets that barely reflect radar energy
- Plain (non-precipitating) cloud also gives negligible radar return
- Correct answer: b (Hail)
030299 · Winds
For mountain waves to develop, the wind above the ridge height should:
- Aweaken, or even reverse in direction
- Bstrengthen at first, then weaken
- Cstrengthen while direction stays roughly constant
- Dstrengthen and then reverse direction
Why that is the answer
Mountain waves require a specific vertical wind and stability profile. For a well-developed wave to form: the air must be stable (often a layered structure — stable near the surface, sometimes with a less stable layer aloft, capped by a stable layer at height, i.e., 'three-layer' theory), the wind must blow roughly perpendicular to the ridge line, and crucially the wind speed must INCREASE with height above the ridge with little change in direction, reaching or exceeding about 15-25 kt near ridge-top and continuing to strengthen aloft without significant veering/backing. A wind that decreases or reverses with height (option a) would disrupt the wave, and large direction changes would break up the coherent wave pattern needed for the classic lee-wave/rotor structure to develop and persist. Steady, strengthening flow with height allows the wave energy to propagate upward and remain organized, producing the characteristic lenticular clouds and rotor turbulence. The answer is c: increase with little change in direction.
- Mountain wave formation needs: stable air, wind near-perpendicular to ridge, sufficient wind speed at ridge top
- Above ridge level, wind speed must continue to INCREASE with height
- Direction must remain fairly constant (little veer/backing) for the wave to stay organized
- A decreasing or reversing wind (option a) would disrupt/destroy the wave pattern
- Correct requirement: wind increases with height, little change in direction — answer c
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