The gases like Water Vapour (WV), Carbon Mono Oxide, Sulphur di Oxide, Nitrogen di Oxide, and Methane vary in amount from place to place, being concentrated more in industrial areas, cities and water bodies, than in open areas. Though very small in quantity, these gases are very significant for weather and life.
Particles such as salt from evaporating sea water, dust from arid regions, industrial particles:
Practice Questions & Answers
Q1Lowest layer of atmosphere is ……… (a) Troposphere (b) Tropopause (c) Stratosphere
✅ Correct Answer: (a) Troposphere
The Troposphere is the lowest layer, starting at earth's surface and extending to the tropopause. All weather occurs here.
Distractor Analysis(b) Tropopause is a boundary, not a layer. (c) Stratosphere is above the Troposphere.
📌 Instructor's NoteRemember the order: T-S-M-T-E = Troposphere, Stratosphere, Mesosphere, Thermosphere, Exosphere from bottom to top.
Q2Height of Tropopause at equator is ……… (a) 8–10 km (b) 16–18 km (c) 14 km
✅ Correct Answer: (b) 16–18 km
At the equator, rising hot air due to convection pushes the tropopause higher — up to 16–18 km.
Distractor Analysis(a) 8–10 km is the tropopause height at the poles. (c) 14 km is intermediate but incorrect.
📌 Instructor's NoteEquator = Hot = Higher tropopause. Poles = Cold = Lower tropopause. "Hotter higher, colder lower."
Q3Height of Tropopause at Poles is ……… (a) 12 km (b) 13 km (c) 08 km
✅ Correct Answer: (c) 08 km
At the poles, the atmosphere is colder; therefore convective activity is minimal and the tropopause is lower, around 8–10 km.
Distractor Analysis(a) and (b) are too high for polar regions.
📌 Instructor's NotePolar tropopause ~300 hPa; Tropical tropopause ~100 hPa (lower pressure = higher altitude).
Q4Higher the surface temperature ……… would be the tropopause. (a) Higher (b) Lower (c) Same
✅ Correct Answer: (a) Higher
Warmer surfaces generate more convective activity, pushing the tropopause to a greater height.
Distractor Analysis(b) Lower — incorrect; this is the effect at colder surfaces/poles. (c) Same — temperature definitely affects tropopause height.
📌 Instructor's Note"Warmer surface = Higher tropopause" — think of hot air balloons rising higher when it's warmer.
Q5Height of tropopause ……… (a) Is constant (b) Varies with altitude (c) Varies with Latitude
✅ Correct Answer: (c) Varies with Latitude
Tropopause height depends on latitude (equator ~16–18 km; poles ~8 km) and also on season, surface temperature, synoptic situation.
Distractor Analysis(a) Is constant — definitely not; it varies significantly. (b) Varies with altitude — altitude is not the controlling factor.
📌 Instructor's NoteTropopause height is controlled by: Surface Temp, Latitude, Season, Land-Sea distribution, Synoptic situation.
Q6Above 8 km the lower temperatures are over ……… (a) Equator (b) Mid Latitudes (c) Poles
✅ Correct Answer: (c) Poles
Above 8 km, polar tropopause is at a lower height. Above the tropopause (stratosphere), temperatures invert. Since polar tropopause is lower (~8 km), above 8 km at poles we are already in the lower stratosphere where temperature reversal occurs, making it warmer — but the question refers to lower temperatures in the troposphere above 8 km. Actually, since poles have reversal above 8 km (into stratosphere), this is a nuanced answer. The text states "there is reversal of temperature and density above 8 km" at poles.
Distractor Analysis(a) Equator tropopause is at 16–18 km, so above 8 km equator is still in troposphere getting colder with height. (c) Poles — above 8 km at poles, we are in stratosphere where temp starts rising.
📌 Instructor's NoteKey: Tropopause temp at poles (–40 to –45°C) is warmer than at equator (–70 to –75°C). Equator has colder tropopause despite being hotter at surface.
Q7Atmosphere is heated by ……… (a) Solar Radiation (b) Heat from earth surface (c) From above
✅ Correct Answer: (b) Heat from earth surface
The atmosphere is heated from below by the earth's surface (via conduction, convection, radiation and latent heat). The atmosphere is a poor absorber of direct solar radiation.
Distractor Analysis(a) Solar radiation heats the EARTH, not directly the lower atmosphere. (c) From above is incorrect — atmosphere is heated from below.
📌 Instructor's NoteRemember: Temperature falls with height in troposphere BECAUSE heating is from below.
Q8The temperature at 80 km is ……… (a) 173 K (b) 100 K (c) –137°C
✅ Correct Answer: (a) 173 K (= –100°C)
The text explicitly states: "The temperature at 80 km is about –100°C (173.15 K)." 173 K ≈ –100°C. This is the Mesopause, the coldest point in the atmosphere.
Distractor Analysis(b) 100 K = –173°C, far too cold. (c) –137°C = 136 K, not matching the textbook value.
📌 Instructor's NoteMesopause = –100°C = 173.15 K. Mnemonic: "80 km → 173 K → Meteors burn".
Q9CO₂ and H₂O are also called ……… (a) Green House Gases (b) Rare Earth Gases (c) [other]
✅ Correct Answer: (a) Green House Gases
CO₂ and H₂O (water vapour) along with O₃ and Methane are greenhouse gases — they are transparent to shortwave solar radiation but absorb longwave terrestrial radiation.
Distractor Analysis(b) Rare Earth Gases (Noble gases like Argon, Neon, Helium) are a different category entirely.
📌 Instructor's NoteGreenhouse gases: W-C-O-M = Water vapour, CO₂, O₃, Methane.
Q10Troposphere is generally ……… (a) Stable (b) Unstable (c) Neutral
✅ Correct Answer: (b) Unstable
The Troposphere has a lapse rate of ~6.5°C/km. With turbulent mixing, convective activity and all weather occurring here, it is generally unstable.
Distractor Analysis(a) Stable — that's the Stratosphere. (c) Neutral — not the defining characteristic.
📌 Instructor's NoteTroposphere = Unstable; Stratosphere = Stable. Easy contrast for exams.
Q11Stratosphere is ……… (a) Unstable (b) Neutral (c) Stable
✅ Correct Answer: (c) Stable
The Stratosphere has a temperature inversion (temperature increases with height due to ozone absorbing UV), making it very stable with no convective weather.
Distractor Analysis(a) Unstable — that's the Troposphere. (b) Neutral — not the dominant characteristic.
📌 Instructor's NoteStratosphere = "Stratified" = Layered = Stable. Also: no weather, steady winds.
Q12Tropopause is discontinuous at about ……… (a) 30°lat (b) 40°lat (c) 80°lat
✅ Correct Answer: (b) 40°lat
The breaks/folds in the tropopause occur at ~40° and ~60° latitude, with the break at 40°lat being more prominent. Jet streams occur at these breaks.
Distractor Analysis(a) 30°lat — not a significant break. (c) 80°lat — too poleward, not where the prominent break is.
📌 Instructor's Note"Break at 40, Fold at 60." Jet streams at these breaks — important for upper-level wind planning.
Q13Most of atmospheric mass is contained in ……… (a) Troposphere (b) Stratosphere (c) Heterosphere
✅ Correct Answer: (a) Troposphere
The Troposphere contains 75% of the atmospheric mass and 99% of water vapour and aerosols.
Distractor Analysis(b) Stratosphere is relatively thin in mass. (c) Heterosphere is the outer part with very low density.
📌 Instructor's NoteTroposphere = 75% mass, 99% WV & aerosols. Two key numbers.
Q14Stratosphere extends from Tropopause to ……… (a) 50 km (b) 60 km (c) 40 km
✅ Correct Answer: (a) 50 km
The Stratosphere extends up to ~50 km from the earth's surface (approximately 30–32 km above the tropopause at equator).
Distractor Analysis(b) 60 km is too high — enters Mesosphere region. (c) 40 km is not the correct upper boundary.
📌 Instructor's NoteLayer tops: Tropo ~18, Strato ~50, Meso ~80. Easy: 18–50–80.
Q15The middle atmosphere layer with temperature inversion and stability is ……… (a) Troposphere (b) Tropopause (c) Stratosphere
✅ Correct Answer: (c) Stratosphere
The Stratosphere has a temperature inversion (UV absorption by ozone warms upper layers) making it very stable. It lies between the Tropopause and Stratopause.
Distractor Analysis(a) Troposphere is unstable with a normal lapse rate. (b) Tropopause is a boundary, not a layer.
📌 Instructor's NoteStratosphere = Stable + Inversion = Ozone = UV absorption. All linked.
Q16Mother of Pearl clouds occur in ……… (a) Mesosphere (b) Thermosphere (c) Stratosphere
✅ Correct Answer: (c) Stratosphere
Nacreous Clouds (Mother of Pearl Clouds) are sometimes seen in the Stratosphere in higher latitudes in winters.
Distractor Analysis(a) Mesosphere — Noctilucent clouds occur here. (b) Thermosphere — no clouds form here.
📌 Instructor's NoteNacreous = Stratosphere | Noctilucent = Mesosphere. "Na-Stra, Noc-Meso".
Q17The temperature in ISA at 17 km is ……… (a) –56.5°C (b) –65.5°C (c) –35.5°C
✅ Correct Answer: (a) –56.5°C
In ISA, from 11 km to 20 km (65,617 ft), temperature is assumed constant at –56.5°C. 17 km falls within this isothermal zone.
Distractor Analysis(b) –65.5°C and (c) –35.5°C are both incorrect — no lapse rate change occurs in this zone.
📌 Instructor's NoteISA isothermal zone: 11 km to 20 km = –56.5°C throughout. Any question with height 11–20 km → answer is –56.5°C.
Q18By weight, approximate ratio of O₂ to N₂ in the atmosphere is ……… (a) 1:3 (b) 1:4 (c) 1:5
✅ Correct Answer: (a) 1:3 (i.e., O₂ : N₂ = 1:3 by weight)
N₂ : O₂ by weight = 3:1, so O₂ : N₂ by weight = 1:3.
Distractor Analysis(b) 1:4 — that is the VOLUME ratio (O₂:N₂ = 1:4). Don't confuse weight and volume ratios.
📌 Instructor's NoteVolume: 4:1 | Weight: 3:1 (N₂:O₂). Volume ratio is larger because N₂ is less dense per unit volume.
Q19By volume, the approximate ratio of O₂ to N₂ in the atmosphere is ……… (a) 1:3 (b) 1:4 (c) 1:5
✅ Correct Answer: (b) 1:4 (O₂ : N₂ = 1:4 by volume)
N₂ : O₂ by volume = 4:1, therefore O₂ : N₂ = 1:4. N₂ = 78.09%, O₂ = 20.95% — ratio is almost 4:1.
Distractor Analysis(a) 1:3 is the weight ratio. (c) 1:5 is incorrect.
📌 Instructor's NoteVolume ratio is 4:1 (larger). Weight ratio is 3:1 (smaller). "Volume is Vast (4)."
Q20By volume, the proportion of CO₂ in the atmosphere is ……… (a) 3% (b) 0.3% (c) 0.03%
✅ Correct Answer: (c) 0.03% (0.035%)
CO₂ constitutes approximately 0.035% by volume in the atmosphere.
Distractor Analysis(a) 3% — vastly overstated. (b) 0.3% — 10 times too high.
📌 Instructor's NoteCO₂ = 0.035% ≈ 0.03% — tiny amount but significant for greenhouse effect.
Q21In ISA, the mean sea level temperature is ……… (a) 15°C (b) 10°C (c) 25°C
✅ Correct Answer: (a) 15°C
ISA MSL temperature = 15°C (288.15 K). This is a fundamental ISA value.
Distractor Analysis(b) 10°C — incorrect. (c) 25°C — too warm, not ISA standard.
📌 Instructor's NoteISA MSL: Temp = 15°C, Pressure = 1013.25 hPa, Density = 1225 g/m³. Memorise all three together.
Q22Maximum concentration of ozone is at a height of ……… (a) 10–15 km (b) 20–25 km (c) 30–35 km
✅ Correct Answer: (b) 20–25 km
Ozone is found between 10–50 km with maximum concentration at 20–25 km in the lower Stratosphere.
Distractor Analysis(a) 10–15 km — lower end of ozone range, not maximum. (c) 30–35 km — past the maximum.
📌 Instructor's NoteOzone range: 10–50 km | Max: 20–25 km | Ozone layer: ~25 km. "20-25 is Ozone's favourite zone."
Q23Additional oxygen is needed while flying above ……… (a) 5000 ft (b) 7000 ft (c) 10000 ft
✅ Correct Answer: (c) 10000 ft
Due to rapid reduction of gases with height, supplementary oxygen is needed above 10,000 ft.
Distractor Analysis(a) 5000 ft and (b) 7000 ft — below the threshold requiring supplemental oxygen.
📌 Instructor's Note10,000 ft = critical altitude for supplemental O₂. Also relevant for cabin pressurization regulations.
Q24CO₂ and H₂O keep the atmosphere ……… (a) Warm (b) Cold (c) Have no effect
✅ Correct Answer: (a) Warm
CO₂ and H₂O are greenhouse gases that absorb terrestrial longwave radiation and re-radiate it, keeping the earth warmer than it would otherwise be.
Distractor Analysis(b) Cold — incorrect, they trap heat. (c) Have no effect — incorrect, they are the primary drivers of the greenhouse effect.
📌 Instructor's NoteThink of greenhouse gases as a "blanket" around the earth, trapping warmth.
Q25Noctilucent clouds occur in ……… (a) Thermosphere (b) Mesosphere (c) Stratosphere
✅ Correct Answer: (b) Mesosphere
Noctilucent Clouds are seen on rare occasions in the upper Mesosphere, in Polar regions.
Distractor Analysis(a) Thermosphere — no clouds form there. (c) Stratosphere — Nacreous/Mother of Pearl clouds occur here, not Noctilucent.
📌 Instructor's NoteNoctilucent = Mesosphere (Polar) | Nacreous = Stratosphere (higher latitudes, winters). Know both!
Q26Temperature at 2 km is 05°C. What is ISA deviation? Hint: (Actual – ISA) (a) –05°C (b) –02°C (c) 03°C
✅ Correct Answer: (c) 03°C (i.e. +03°C)
ISA temp at 2 km = 15 – (6.5 × 2) = 15 – 13 = 2°C. ISA Deviation = 5 – 2 = +3°C.
Distractor Analysis(a) –5°C wrong sign and magnitude. (b) –2°C — wrong direction entirely.
📌 Instructor's NoteISA Deviation = Actual – ISA. Positive deviation = warmer than ISA. Always compute ISA temp first using lapse rate.
Q27Pressure at MSL is 1002.25 hPa. Find the ISA deviation. Hint: (Actual – ISA) (a) –11 hPa (b) 10 hPa (c) 12 hPa
✅ Correct Answer: (a) –11 hPa
ISA MSL Pressure = 1013.25 hPa. Deviation = 1002.25 – 1013.25 = –11 hPa. Negative means pressure is lower than ISA standard.
Distractor Analysis(b) 10 hPa and (c) 12 hPa — wrong sign and magnitude.
📌 Instructor's NoteSame formula applies for pressure deviation as temperature deviation. ISA MSL Pressure = 1013.25 hPa.
Q28In actual atmosphere temp. at 19 km is –60°C. Find the ISA deviation. Hint: (Actual – ISA) (a) –4.5°C (b) –05.5°C (c) –03.5°C
✅ Correct Answer: (c) –03.5°C
ISA temp at 19 km = –56.5°C (isothermal zone 11–20 km). Deviation = –60 – (–56.5) = –60 + 56.5 = –3.5°C.
Distractor Analysis(a) –4.5°C and (b) –5.5°C are arithmetic errors — make sure signs are handled correctly.
📌 Instructor's NoteFor any altitude between 11–20 km: ISA temp is always –56.5°C. Don't try to apply lapse rate in this zone.
Q29Nacreous clouds occur in ……… (a) Thermosphere (b) Mesosphere (c) Upper Stratosphere
✅ Correct Answer: (c) Upper Stratosphere (Stratosphere)
Nacreous Clouds (Mother of Pearl Clouds) are sometimes seen in the Stratosphere in higher latitudes in winters.
Distractor Analysis(a) Thermosphere — no clouds. (b) Mesosphere — Noctilucent clouds.
📌 Instructor's NoteNacreous clouds are iridescent and beautiful — found in the stratosphere over polar regions in winter.
Q30The atmosphere up to 80 km has a nearly similar composition and is called the Homosphere. Its uniform composition is due to ……… (a) Pressure (b) Gravitation of earth (c) Mixing due to turbulence
✅ Correct Answer: (c) Mixing due to turbulence
The atmosphere is generally well mixed up to ~80 km due to turbulent mixing, maintaining a nearly uniform composition.
Distractor Analysis(a) Pressure alone doesn't cause uniform mixing. (b) Gravitation causes vertical stratification, not uniform mixing.
📌 Instructor's NoteHomosphere = uniform mixing by turbulence. Heterosphere = no mixing = separation by molecular weight.
Q31Half of the atmospheric air mass is contained ……… below (a) 20,000 ft (b) 15,000 ft (c) 10,000 ft
✅ Correct Answer: (b) 15,000 ft (~6 km ≈ 19,685 ft; closest is ~18,000 ft; textbook states 6 km)
The textbook states half the atmospheric mass is below 6 km. 6 km ≈ 19,685 ft. The closest answer would be approximately 18,000–20,000 ft. Option (a) 20,000 ft is the closest match.
Distractor AnalysisThe question is about 6 km = ~20,000 ft, so (a) 20,000 ft is correct. 10,000 ft = ~3 km (too low); 15,000 ft = ~4.6 km (too low).
📌 Instructor's Note6 km = ~20,000 ft = half the atmosphere below this level. Key for pressurisation and O₂ planning.
Q32In jet standard atmosphere the Lapse Rate is ……… (a) 2°C/1000 ft (b) 2°C/km (c) 5°C/km
✅ Correct Answer: (a) 2°C/1000 ft
The Jet Standard Atmosphere specifies a lapse rate of 2°C/1000 ft (with no tropopause).
Distractor Analysis(b) 2°C/km is the ISA lapse rate in the stratospheric rise zone (20–30 km) — 1°C/km actually. (c) 5°C/km is not a standard rate.
📌 Instructor's NoteJSA: 2°C/1000 ft, no tropopause. ISA: 6.5°C/km (≈2°C/1000 ft below 11 km, then isothermal).
Q33The rate of fall of temperatures with height, called ……… (a) Isothermal rate (b) Inversion Rate (c) Lapse Rate
✅ Correct Answer: (c) Lapse Rate
Lapse rate is the rate at which temperature decreases with increasing altitude, approximately 6.5°C/km in the ISA troposphere.
Distractor Analysis(a) Isothermal rate — temperature does NOT change with height (isothermal). (b) Inversion Rate — temperature INCREASES with height (inverse of normal).
📌 Instructor's NoteLapse Rate = normal fall of temperature with height. Inversion = temperature rise with height. Isothermal = constant temperature.
Q34In actual atmosphere the lapse rate could ……… (a) Assume any value (b) Fall up to 8 km. (c) Rise up to 50 km
✅ Correct Answer: (a) Assume any value
In the actual (real) atmosphere — unlike ISA — the lapse rate can assume any value; it can be positive, zero (isothermal), or negative (inversion) depending on atmospheric conditions.
Distractor Analysis(b) and (c) describe fixed behaviours. The actual atmosphere is highly variable.
📌 Instructor's NoteISA lapse rate = fixed at 6.5°C/km. ACTUAL lapse rate = variable, can be anything. This distinction is key for stability analysis.
Q35Tropical Tropopause extends from the equator to Lat. 35°–40°. Over India it is at ……… (a) 20–21 km (b) 14–15 km (c) 16–16.5 km
✅ Correct Answer: (c) 16–16.5 km (or option b 14–15 km per textbook)
Over India, the Tropical Tropopause is at approximately 11.5 km (temperature –45°C) per the textbook. In winters it may be at 23°N. The Tropical Tropopause extends to Lat. 35°–40° and at 100 hPa level, which is approximately 16–16.5 km at equatorial latitudes.
Distractor AnalysisThe question specifies "over India" — India is in tropical latitudes (8°N–37°N); the tropical tropopause over India varies with season.
📌 Instructor's NoteTropical Tropopause: ~100 hPa level | Over India: ~11.5 km at 23°N in winters. India experiences both tropical and subtropical tropopause influences.
Q36Lapse rate in the troposphere is produced by ……… and in the stratosphere by ……… (a) Evaporation; condensation (b) Condensation; solar radiation (c) Terrestrial radiation; solar radiation (d) Solar radiation; convection
✅ Correct Answer: (c) Terrestrial radiation; solar radiation
In the Troposphere: cooling with height is due to terrestrial radiation heating from below. In Stratosphere: temperature inversion is due to solar radiation (UV) being absorbed by ozone — causing warming with height.
Distractor AnalysisOther combinations mix up the mechanisms. Condensation releases latent heat but is not the primary cause of the lapse rate.
📌 Instructor's NoteTroposphere heated from Earth (below) → cools upward. Stratosphere heated by ozone absorbing UV (from Sun above) → warms upward.
Q37Most of the water vapour in the atmosphere is confined up to ……… (a) stratosphere (b) 30,000 ft (c) Mid troposphere (d) lower troposphere
✅ Correct Answer: (d) lower troposphere
Water vapour concentration rapidly decreases with height. Most WV is concentrated in the lower troposphere where temperatures are highest. Above 30,000 ft, WV is very low.
Distractor Analysis(a) Stratosphere — very little WV. (b) 30,000 ft — WV is minimal at this height. (c) Mid troposphere — less than lower troposphere.
📌 Instructor's Note99% WV and aerosols in troposphere; most concentrated in lower troposphere. This is why most weather and cloud formation occurs there.
Q38Negative lapse rate of temperature is ……… (a) Isothermal rate (b) Temperature rise with lowering height (c) Temperature rise with height (d) Temperature fall with height
✅ Correct Answer: (c) Temperature rise with height
A "negative lapse rate" means temperature increases with altitude — this is called an inversion. This occurs in the Stratosphere and in inversions within the Troposphere.
Distractor Analysis(a) Isothermal = zero lapse rate (no temperature change). (d) Temperature fall with height = positive lapse rate (normal). (b) is phrased incorrectly.
📌 Instructor's NotePositive lapse rate = temp falls with height (normal). Zero lapse rate = isothermal. Negative lapse rate = inversion (temp rises with height).
Q39In ICAO ISA the atmosphere is assumed to be isothermal ……… (a) in stratosphere (b) 11 to 16 km (c) 11 to 20 km (d) 11 to 32 km
✅ Correct Answer: (c) 11 to 20 km
In ICAO ISA, temperature is assumed constant at –56.5°C from 11 km (36,090 ft) to 20 km (65,617 ft). This is the isothermal (stratospheric) zone.
Distractor Analysis(b) 11–16 km — too narrow. (d) 11–32 km — too wide; from 20 km temperature starts rising again. (a) "in stratosphere" is vague and incorrect if taken to mean the whole stratosphere.
📌 Instructor's NoteISA Isothermal: 11–20 km at –56.5°C. After 20 km temp rises. After 32 km another zone begins.
Q40One of the characteristics of our atmosphere is ……… (a) Poor conductor of heat and electricity (b) Equator is warmer than poles above 10 km (c) Lapse rate is positive in stratosphere (d) Density is constant above 8 km
✅ Correct Answer: (a) Poor conductor of heat and electricity
The atmosphere is a poor conductor of heat and electricity — one of its key characteristics listed at the beginning of the chapter.
Distractor Analysis(b) Above 10 km, poles are actually warmer than equator at the tropopause (poles –40 to –45°C vs equator –70 to –75°C). (c) Lapse rate in stratosphere is negative (inversion). (d) Density is NOT constant above 8 km.
📌 Instructor's NoteAtmosphere = poor conductor. Counterintuitively, tropopause at POLES is warmer (–40°C) than EQUATOR (–75°C) — despite surface being opposite!
Q41Heat transfer in the atmosphere is maximum due to ……… (a) convection (b) radiation (c) sensible heat (d) latent heat
✅ Correct Answer: (d) latent heat
Latent Heat (Evaporation, Condensation, Sublimation) accounts for 77% of heat transfer from earth to atmosphere — much more than sensible heat at 23%.
Distractor Analysis(a) Convection is a mechanism within sensible heat, not the maximum overall. (b) Radiation contributes but is part of the 23%. (c) Sensible heat is only 23%.
📌 Instructor's NoteLatent heat = 77% (dominant!). Sensible heat = 23%. "Latent is Larger at 77%."
Q42The knowledge of the height of tropopause is important for a pilot because ……… (a) weather is mainly confined up to this level (b) clouds rarely reach up to this height due to jetstream (c) stratosphere starts at this height where all solar radiation is absorbed
✅ Correct Answer: (a) weather is mainly confined up to this level
The tropopause is the maximum height clouds can reach. All weather, turbulence, cloud formations are below it. Knowing its height helps pilots plan for weather-free cruising altitudes.
Distractor Analysis(b) Clouds do grow to just below tropopause — not because of jet streams. (c) Solar radiation is absorbed by ozone in the stratosphere, not at the tropopause itself.
📌 Instructor's NoteTropopause = weather ceiling. Above it = stable, clear, steady stratospheric winds. CAT and Jet streams just BELOW it.
Q43In ISA atmosphere the tropopause occurs at a height of ……… (a) 8–10 km (b) 11 km (c) 16–18 km
✅ Correct Answer: (b) 11 km
In ICAO ISA, the tropopause is fixed at 11 km (36,090 ft), where the lapse rate stops and isothermal zone begins (–56.5°C).
Distractor Analysis(a) 8–10 km = actual polar tropopause. (c) 16–18 km = actual equatorial tropopause. ISA is a standard — fixed at 11 km.
📌 Instructor's NoteISA tropopause = 11 km = 36,090 ft. This is a fixed constant in ISA, unlike the actual variable tropopause.
Q44Most of the transfer of heat in the atmosphere is due to ……… (a) conduction (b) convection (c) Both A and B (d) latent heat
✅ Correct Answer: (d) latent heat
As stated in the chapter: Latent Heat transfer = 77% (dominant). Sensible heat (including conduction, convection, radiation) = 23%.
Distractor Analysis(a) Conduction — atmosphere is a poor conductor. (b) Convection — important but part of 23%. (c) Both — only 23% combined.
📌 Instructor's NoteThis question is almost identical to Q41. Reinforce: Latent heat dominates atmospheric heat transfer.
Q45There is reversal of temperature at poles and becomes negative at ……… (a) 8 km (b) 12 km (c) 20 km (d) 30 km
✅ Correct Answer: (a) 8 km
Since the polar tropopause is at ~8–10 km, above 8 km at the poles we enter the stratosphere where temperature reverses (starts rising). The text states: "since in troposphere temperatures fall with height up to tropopause, above 8 km the poles start warming up and become warmer than the equator."
Distractor Analysis(b) 12 km and higher — the reversal starts at the polar tropopause (~8 km), not higher.
📌 Instructor's NoteAbove 8 km at poles: temperature reversal → poles become warmer than equator (at that level). This is why jet streams form at tropopause breaks.
Capt. Pankaj Pahil