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ATMOSPHERE — DGCA CPL Aviation Meteorology
Chapter J01 of the Aviation Meteorology paper. 45 practice questions in the Avielevate bank, every one with its answer key, filterable into a timed set on this chapter alone.
What this chapter covers
The learning objectives we file ATMOSPHERE questions under, and how many sit behind each. These come straight out of the bank and are regenerated whenever it changes — they are what is there today, not a claim.
| Learning objective | In the bank |
|---|
| __GEN__ General | 45 questions |
Sample ATMOSPHERE questions, answered and explained
Real questions from this chapter, with the answer marked and the reasoning written out — the same explanations you get inside the app.
0310021 · ATMOSPHERE
Where are noctilucent clouds found?
- AThermosphere
- BMesosphere
- CStratosphere
Why that is the answer
**Concept**
Almost all cloud is in the troposphere. **Noctilucent clouds** (night-shining clouds) are the highest clouds of all, far above any weather.
**Explanation**
They form near the top of the **mesosphere**, at about **80 to 85 km**, close to the mesopause. Look at the diagram: this is the coldest part of the whole atmosphere, about −90 to −100°C or even colder in summer over high latitudes. There is almost no water vapour at that height, but the extreme cold is enough for tiny ice crystals to form, probably on specks of meteor dust.
They are so high that they are still lit by the sun long after sunset, when the ground and all lower clouds are in darkness. That is why they are seen glowing silvery-blue against the night sky, usually in summer at latitudes of about 50 to 70°. Look at the photo.
**Applying it to the question**
Noctilucent clouds are found in the **Mesosphere**. They should not be confused with nacreous (mother-of-pearl) clouds, which form lower, in the stratosphere at about 15 to 25 km.
**Remember for DGCA:** noctilucent = mesosphere, about 80 to 85 km; nacreous = stratosphere, about 15 to 25 km.
Image credit: okruz (public domain), via Wikimedia Commons.
0310024 · ATMOSPHERE
The stratosphere extends from the tropopause up to about:
- A50 km
- B60 km
- C40 km
Why that is the answer
**Concept**
The atmosphere is divided into layers by how the temperature changes with height. The **stratosphere** is the second layer, above the troposphere.
**Explanation**
Look at the diagram. The stratosphere begins at the **tropopause** (about 8 km over the poles, 11 km on average, 16 to 18 km over the equator). In its lower part the temperature stays nearly constant; higher up it **rises** with height, because ozone absorbs the sun's ultraviolet radiation and warms the air.
The warming continues up to the **stratopause** at about **50 km**, where the temperature reaches close to 0°C. Above it, in the mesosphere, there is too little ozone to heat the air, so the temperature starts to fall again. The change from rising to falling temperature marks the top of the stratosphere.
**Applying it to the question**
The stratosphere extends from the tropopause up to about **50 km**. The mesosphere then continues to about 80 to 85 km.
**Remember for DGCA:** tropopause about 11 km, stratopause about 50 km, mesopause about 80 to 85 km.
0310029 · ATMOSPHERE
Which middle layer of the atmosphere has a temperature inversion and is stable?
- ATroposphere
- BTropopause
- CStratosphere
Why that is the answer
**Concept**
An **inversion** is a layer in which the temperature **rises** with height instead of falling. Air in an inversion is very **stable**: a parcel pushed upwards cools as it rises, ends up colder and denser than the warmer air around it, and sinks back.
**Explanation**
Look at the diagram. Going up from the surface:
- In the **troposphere** the temperature falls with height, so air can rise and overturn, producing convection, cloud and weather.
- The **tropopause** is only the boundary between the layers, where the fall of temperature stops.
- In the **stratosphere** the temperature first stays steady and then rises with height up to about 50 km, because ozone absorbs the sun's ultraviolet radiation. This makes the stratosphere one large inversion, so it is stable, with very little vertical movement, cloud or turbulence.
In the four-layer picture (troposphere, stratosphere, mesosphere, thermosphere), the stratosphere is one of the two middle layers.
**Applying it to the question**
The layer with a temperature inversion that is stable is the **Stratosphere**. Its stability is why thunderstorm tops stop and spread out into an anvil when they reach it.
**Remember for DGCA:** stratosphere = isothermal then inversion = stable; the ozone layer is the cause of the warming.
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Frequently asked
How many ATMOSPHERE questions are there for the DGCA CPL Aviation Meteorology paper?
Avielevate's bank carries 45 published ATMOSPHERE questions for Aviation Meteorology, mapped across 1 learning objective. Every one has its answer key, and explanations are being written across the whole bank.
How much of the Aviation Meteorology paper is ATMOSPHERE?
The DGCA does not publish a per-chapter breakdown of its papers, so nobody can honestly tell you — and we will not guess. What we can tell you is what students who have just sat a paper reported meeting, which is measured rather than rumoured: that is the exam recall report inside the app.
What is the best way to revise ATMOSPHERE?
Sit a short timed set on this chapter alone, tag how sure you were of each answer, then drill the two that actually leak marks: the ones you got right while guessing, and the ones you got wrong while confident. Avielevate does that tagging for you and puts anything you got wrong back in front of you on a spaced schedule.
The rest of the Aviation Meteorology paper
One account covers every chapter of every paper.
← All Aviation Meteorology chapters · All six DGCA CPL papers