AtmosphereAviation Meteorology — DGCA CPL practice questions
Question 1 of 56
The lowest layer of the atmosphere is the:
All 56 questions — Atmosphere
Aviation Meteorology · DGCA CPL. The correct option is marked on each.
Q1. The lowest layer of the atmosphere is the:
- A.Troposphere✓
- B.Tropopause
- C.Stratosphere
Why: Troposphere is the lowest layer.
Q2. The height of the tropopause at the Equator is approximately:
- A.10–12 km
- B.16–18 km✓
- C.12–14 km
Why: Equatorial tropopause ≈16 km. Options de-garbled.
Q3. The height of the tropopause at the Poles is approximately:
- A.12–14 km
- B.12–13 km
- C.8–10 km✓
Why: Polar tropopause ≈8 km. Options de-garbled.
Q4. The higher the surface temperature, the ____ the tropopause:
- A.Higher✓
- B.Lower
- C.Same
Why: Warm surface → deeper troposphere → higher tropopause. Fixed 'tropopau se'.
Q5. The height of the tropopause:
- A.Is constant
- B.Varies with altitude
- C.Varies with latitude✓
Why: Tropopause height decreases from Equator to Poles.
Q6. Above 8 km, the lower temperatures are found over the:
- A.Equator✓
- B.Mid-latitudes
- C.Poles
Why: Equatorial tropopause is higher & colder than polar.
Q7. The atmosphere is heated mainly by:
- A.Solar radiation directly
- B.Heat from the earth's surface✓
- C.Radiation from space
Why: Atmosphere heated from below by terrestrial radiation.
Q8. The stratosphere is:
- A.Unstable
- B.Neutral
- C.Stable✓
Why: Stratosphere is STABLE.
Q9. The tropopause is discontinuous (has breaks) at about:
- A.30° latitude✓
- B.40° latitude
- C.60° latitude
Why: Main tropopause breaks near 30°; also 60°.
Q10. Most of the atmospheric mass is contained in the:
- A.Troposphere✓
- B.Stratosphere
- C.Heterosphere
Why: ≈¾ of atmospheric mass is in the troposphere.
Q11. The stratosphere extends from the tropopause up to about:
- A.50 km✓
- B.60 km
- C.40 km
Why: Stratosphere ≈11–50 km.
Q12. The atmospheric layer characterised by a temperature inversion and great stability is the:
- A.Troposphere
- B.Tropopause
- C.Stratosphere✓
Why: Stratosphere.
Q13. Mother-of-pearl (nacreous) clouds occur in the:
- A.Mesosphere
- B.Thermosphere
- C.Stratosphere✓
Why: Nacreous/mother-of-pearl clouds ≈20–30 km, stratosphere.
Q14. In the ISA, the temperature at 17 km is:
- A.−56.5°C✓
- B.−65.5°C
- C.−35.5°C
Why: ISA isothermal −56.5°C from 11–20 km. Fixed missing minus signs.
Q15. By weight, the approximate ratio of O₂ to N₂ in the atmosphere is:
- A.1:3✓
- B.1:4
- C.1:5
Why: By mass O₂≈23%, N₂≈76% → ≈1:3.
Q16. By volume, the approximate ratio of O₂ to N₂ in the atmosphere is:
- A.1:3
- B.1:4✓
- C.1:5
Why: By volume O₂≈21%, N₂≈78% → ≈1:4.
Q17. By volume, the proportion of CO₂ in the atmosphere is about:
- A.3%
- B.0.3%
- C.0.03%✓
Why: CO₂ ≈0.03–0.04% by volume.
Q18. In the ISA, the mean sea level temperature is:
- A.15°C✓
- B.10°C
- C.25°C
Why: ISA MSL temperature = +15°C.
Q19. The maximum concentration of ozone is at a height of about:
- A.10–15 km
- B.20–25 km✓
- C.30–35 km
Why: Ozone maximum ≈20–25 km. Options de-garbled.
Q20. Supplemental oxygen is required when flying above about:
- A.5000 ft
- B.7000 ft
- C.10 000 ft✓
Why: Supplemental O₂ above ≈10 000 ft.
Q21. CO₂ and water vapour keep the atmosphere:
- A.Warm✓
- B.Cold
- C.No effect
Why: Greenhouse gases warm the atmosphere.
Q22. Noctilucent clouds occur in the:
- A.Thermosphere
- B.Mesosphere✓
- C.Stratosphere
Why: Noctilucent clouds near the mesopause ≈80 km.
Q23. If the temperature at 2 km is +5°C, the ISA deviation (Actual − ISA) is:
- A.−5°C
- B.+2°C
- C.+3°C✓
Why: ISA@2km≈+2°C; +5−=+3°C. Fixed answer-option sign.
Q24. If the MSL pressure is 1002.25 hPa, the deviation from the ISA MSL pressure is:
- A.−11 hPa✓
- B.+10 hPa
- C.+12 hPa
Why: 1002.25 − 1013.25 = −11 hPa.
Q25. If the temperature at 19 km is −60°C, the ISA deviation is:
- A.−4.5°C
- B.−5.5°C
- C.−3.5°C✓
Why: ISA@19km=−56.5°C; −60−=−3.5°C.
Q26. The homosphere (up to ≈80 km) has a uniform composition because of:
- A.Pressure
- B.Gravitation
- C.Turbulent mixing✓
Why: Uniform because turbulent/eddy mixing dominates.
Q27. Approximately half of the atmosphere's mass (by weight) lies below:
- A.20 000 ft✓
- B.15 000 ft
- C.10 000 ft
Why: 50% of mass below ≈5500 m ≈18 000 ft → 20 000 ft closest.
Q28. In the Jet Standard Atmosphere, the assumed lapse rate is:
- A.2°C/1000 ft✓
- B.2°C/km
- C.5°C/km
Why: JSA uses 2°C per 1000 ft.
Q29. The rate of fall of temperature with height is called the:
- A.Isothermal rate
- B.Inversion rate
- C.Lapse rate✓
Why: Definition of lapse rate.
Q30. In the actual atmosphere, the lapse rate can:
- A.Assume any value✓
- B.Only fall up to 8 km
- C.Only rise up to 50 km
Why: Real environmental lapse rate varies.
Q31. The tropical tropopause over India is at about:
- A.20–21 km
- B.14–15 km
- C.16–16.5 km✓
Why: Tropical tropopause ≈16–17 km. Options de-garbled.
Q32. The lapse rate in the troposphere is caused by ____ , and the stratospheric inversion by ____:
- A.Evaporation; condensation
- B.Rising air; solar radiation
- C.Terrestrial radiation; solar radiation (ozone)✓
- D.Solar radiation; convection
Why: Troposphere heated from below; stratosphere warmed by ozone absorbing solar UV.
Q33. A negative lapse rate (temperature rising with height) is known as an:
- A.Isothermal layer
- B.Temperature fall with height
- C.Inversion✓
- D.Adiabatic layer
Why: Inversion = temperature increasing with height. Options tidied.
Q34. In the ICAO ISA, the atmosphere is assumed to be isothermal from:
- A.11 to 16 km
- B.11 to 20 km✓
- C.11 to 32 km
- D.0 to 11 km
Why: ISA is isothermal 11→20 km, then rises.
Q35. Which is a characteristic of the atmosphere?
- A.It is a poor conductor of heat and electricity✓
- B.The Equator is warmer than the poles above 10 km
- C.The stratospheric lapse rate is positive
- D.Density is constant above 8 km
Why: Air is a poor conductor; the other options are false.
Q36. The knowledge of the tropopause height is important to a pilot because:
- A.Weather is mainly confined up to this level✓
- B.Clouds never reach this height
- C.All solar radiation is absorbed here
Why: Weather is confined to the troposphere.
Q37. In the ISA, the tropopause is at a height of:
- A.8–10 km
- B.11 km✓
- C.16–18 km
Why: ISA tropopause = 11 km. Options de-garbled.
Q38. Most of the atmospheric water vapour is found:
- A.In the stratosphere
- B.Up to 30 000 ft
- C.In the mid-troposphere
- D.In the lower troposphere✓
Why: Most water vapour is held in the lower troposphere.
Q39. The greatest transfer of heat from the earth's surface to the atmosphere is by:
- A.Convection
- B.Radiation
- C.Sensible heat
- D.Latent heat✓
Why: Latent heat is the largest single component of heat transfer from the surface to the atmosphere.
Q40. In the ISA, the temperature decrease with height below 11 km is:
- A.0.5°C/100 m
- B.0.6°C/100 m
- C.0.65°C/100 m✓
- D.1°C/100 m
Why: ISA lapse 6.5°C/km = 0.65°C/100 m.
Q41. The 200 hPa pressure level, in temperate regions, is at an average height of about:
- A.FL390✓
- B.FL300
- C.FL100
- D.FL50
Why: 200 hPa ≈ 38 700 ft ≈ FL390.
Q42. The temperature at FL110 is −12°C. Applying the ICAO standard lapse rate, the temperature at FL140 is:
- A.−6°C
- B.−18°C✓
- C.−9°C
- D.−15°C
Why: 3000 ft × 2°C/1000 ft = 6°C colder → −18°C.
Q43. At a position the 300 hPa temperature is −54°C and the tropopause is at FL330. The most likely temperature at FL350 is:
- A.−48°C
- B.−60°C✓
- C.−56.5°C
- D.−64°C
Why: FL300→FL330: −54−6=−60°C; above tropopause isothermal → FL350=−60°C.
Q44. The boundary between the troposphere and the stratosphere is called the:
- A.Ionosphere
- B.Stratopause
- C.Atmosphere
- D.Tropopause✓
Why: Tropopause.
Q45. Which constant-pressure chart is standard for the FL50 (≈4781 ft) level?
- A.500 hPa
- B.300 hPa
- C.850 hPa✓
- D.700 hPa
Why: 850 hPa ≈ 5000 ft.
Q46. An OAT of −30°C is measured at FL200. The temperature deviation from ISA is:
- A.5°C colder than ISA✓
- B.5°C warmer than ISA
- C.10°C colder than ISA
- D.10°C warmer than ISA
Why: ISA@FL200=−25°C; −30 is 5°C colder.
Q47. The most likely temperature at the tropical tropopause is:
- A.−56.5°C
- B.−75°C✓
- C.−40°C
- D.−25°C
Why: Tropical tropopause ≈−75°C.
Q48. In the lower part of the stratosphere the temperature:
- A.Is almost constant✓
- B.Decreases with altitude
- C.Increases with altitude
- D.Increases then decreases
Why: Lower stratosphere is isothermal.
Q49. An air temperature of −15°C at the 700 hPa level over western Europe would be characterised as:
- A.Within ±5°C of ISA
- B.20°C below standard
- C.Low✓
- D.High
Why: 700 hPa≈FL100, ISA≈−5°C; −15°C is colder than standard = Low.
Q50. Flying at FL300 in an air mass 15°C warmer than ISA, the outside temperature is likely:
- A.−15°C
- B.−30°C✓
- C.−45°C
- D.−60°C
Why: ISA@FL300=−45°C; +15 → −30°C.
Q51. At FL140 the OAT is −8°C. The freezing level is at approximately:
- A.FL75
- B.FL100✓
- C.FL130
- D.FL180
Why: −8°C→0°C needs +4000 ft descent; FL140−40=FL100.
Q52. The most important constituent in the atmosphere from a weather standpoint is:
- A.Carbon dioxide
- B.Oxygen
- C.Water vapour✓
- D.Methane
Why: Water vapour drives weather.
Q53. The average height of the tropopause at latitude 50° is about:
- A.8 km
- B.11 km✓
- C.14 km
- D.16 km
Why: Mid-latitude tropopause ≈11 km.
Q54. Between MSL and 20 km, the lowest temperature in the ISA is:
- A.−273°C
- B.−44.7°C
- C.−56.5°C✓
- D.−100°C
Why: ISA minimum −56.5°C in the 11–20 km isothermal layer.
Q55. The ISA assumes the temperature reduces at:
- A.1.98°C/1000 ft up to 36 090 ft, then constant to 65 617 ft✓
- B.1.98°C/1000 ft up to 36 090 ft, then +0.3°C/1000 ft
- C.2°C/1000 ft up to 65 617 ft
- D.2°C/1000 ft up to 36 090 ft, then +0.3°C/1000 ft
Why: ISA: 1.98°C/1000 ft to 36 090 ft then isothermal to 65 617 ft.
Q56. A temperature of +15°C is recorded at 500 m AMSL. Using the standard lapse rate, the temperature at a 2500 m summit is:
- A.0°C
- B.+2°C✓
- C.+4°C
- D.−2°C
Why: 2000 m × 6.5°C/km = 13°C; 15−13=+2°C.