Avielevate / DGCA CPL papers / Aviation Meteorology / ATMOSPHERIC PRESSURE
ATMOSPHERIC PRESSURE — DGCA CPL Aviation Meteorology
Chapter J02 of the Aviation Meteorology paper. 41 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 ATMOSPHERIC PRESSURE 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 | 41 questions |
Sample ATMOSPHERIC PRESSURE 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.
0311008 · ATMOSPHERIC PRESSURE
Which type of inversion forms when a stable layer lies over a high-pressure area?
- ANegative
- BRadiation
- CSubsidence
- DAir mass
Why that is the answer
**Concept**
Normally the air gets colder as you go up. An **inversion** is a layer in which the temperature **rises** with height. Warm air sitting on top of cooler air is very stable, so an inversion acts like a lid on vertical movement.
**Explanation**
In a high-pressure area (anticyclone), air converges at high levels and slowly **sinks** over a wide area. This sinking is called **subsidence**. As the air descends, it moves into higher pressure and is **compressed**, so it warms at the dry adiabatic rate (about 3°C per 1,000 ft). It also becomes drier, which is why highs have little cloud.
The sinking air cannot reach the ground: near the surface it spreads out sideways. So the warmed, subsided air ends up lying on top of a cooler, unaffected surface layer. Where the two meet, the temperature increases with height: a **subsidence inversion**, typically a few thousand feet up. Look at the diagram (right half).
Below this lid, smoke, dust and moisture are trapped, which is why highs often bring **haze and poor visibility**, and sometimes a sheet of stratocumulus under the inversion.
**Applying it to the question**
A stable inversion layer formed over a high-pressure area by sinking, compressed air is a **Subsidence** inversion. A radiation inversion, by contrast, forms at ground level on clear nights as the ground cools, and it disappears after sunrise.
**Remember for DGCA:** high pressure = subsidence = warming by compression = subsidence inversion aloft, with haze trapped below.
0311019 · ATMOSPHERIC PRESSURE
Which subscale setting makes the altimeter of an aircraft on the ground read the aerodrome elevation?
- AQNH
- BQNE
- CQFF
- DQFE
Why that is the answer
**Concept**
The pressure you set on the altimeter's **subscale** decides what height it shows: the altimeter always measures height above the level where that pressure is found.
**Explanation**
The common settings are:
- **QFE:** the actual pressure at aerodrome level. The altimeter reads **zero** on the runway and shows height above the aerodrome.
- **QNH:** the aerodrome pressure reduced to mean sea level using the ISA. The altimeter reads the **aerodrome elevation** on the runway and shows altitude above mean sea level.
- **QNE (1013.2 hPa):** the standard setting. The altimeter shows pressure altitude, used for flight levels.
- **QFF:** the aerodrome pressure reduced to mean sea level using the **actual** temperature. It is used to draw isobars on weather charts, not for setting altimeters.
Look at the diagram: the QNH arrow starts at mean sea level, so on the ground it covers exactly the aerodrome elevation.
**Applying it to the question**
The setting that makes the altimeter of an aircraft on the ground read the aerodrome elevation is **QNH**. That is the whole purpose of QNH: it is worked out backwards from the elevation so that this is true, which is why it is used below the transition altitude to keep clear of terrain shown in altitudes on charts.
**Remember for DGCA:** on the runway, QFE reads zero, QNH reads elevation, 1013.2 reads pressure altitude.
0311032 · ATMOSPHERIC PRESSURE
Which instrument measures atmospheric pressure?
- AAnemograph
- BBarometer
- CHygrograph
Why that is the answer
**Concept**
**Atmospheric pressure** is the force per unit area caused by the **weight of the air** above a place. At mean sea level it averages about **1013 hPa**.
**Explanation**
The instrument that measures air pressure is a **barometer** (from the Greek "baros", weight). There are two main kinds:
- **Mercury barometer:** the air pressure holds up a column of mercury in a glass tube, about 760 mm high at sea level. It is very accurate and used as a standard.
- **Aneroid barometer:** a sealed, partly evacuated metal capsule that is squeezed or expands as the pressure changes. It is small and robust, and an aircraft altimeter is an aneroid barometer marked in feet.
A **barograph** is a recording barometer that draws a continuous trace of pressure, which shows the pressure tendency.
**Applying it to the question**
The instrument that measures atmospheric pressure is the **Barometer**. The other names follow the same pattern but measure different things: an anemograph records wind, and a hygrograph records humidity.
**Remember for DGCA:** barometer = pressure, thermometer = temperature, hygrometer = humidity, anemometer = wind speed; a "-graph" instrument records the value continuously.
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Frequently asked
How many ATMOSPHERIC PRESSURE questions are there for the DGCA CPL Aviation Meteorology paper?
Avielevate's bank carries 41 published ATMOSPHERIC PRESSURE 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 ATMOSPHERIC PRESSURE?
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 ATMOSPHERIC PRESSURE?
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