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DGCA CPL Aviation Meteorology study materials
DGCA CPL Aviation Meteorology study resources

DGCA CPL Aviation Meteorology practice questions

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Question 1The Atmosphere: composition, structure, temperature and pressure

Which gas forms the largest proportion of dry air by volume in the lower atmosphere?

  1. Argon
  2. Oxygen
  3. Nitrogen Correct answer.
  4. Carbon dioxide

Explanation

Dry air is dominated by nitrogen, which makes up roughly 78 percent of its volume. Oxygen is the second most abundant at about 21 percent, while argon and carbon dioxide are present only in small amounts.

Question 2The Atmosphere: composition, structure, temperature and pressure

In which atmospheric layer does most of the weather affecting aviation occur?

  1. Stratosphere
  2. Mesosphere
  3. Troposphere Correct answer.
  4. Thermosphere

Explanation

The troposphere contains nearly all the water vapour and is where temperature decreases with height, producing convection, clouds and precipitation. Weather phenomena significant to flight are therefore concentrated in this layer.

Question 3The Atmosphere: composition, structure, temperature and pressure

What is the standard mean sea level pressure used in the International Standard Atmosphere?

  1. 0999.00 hPa
  2. 1023.25 hPa
  3. 1000.00 hPa
  4. 1013.25 hPa Correct answer.

Explanation

The ISA defines mean sea level pressure as 1013.25 hPa (29.92 inHg) at a temperature of 15 degrees Celsius. This value is the reference for pressure altitude and altimeter setting.

Question 4The Atmosphere: composition, structure, temperature and pressure

What is the standard sea level temperature and lapse rate in the International Standard Atmosphere?

  1. 0 degrees C with 6.5 degrees C per km
  2. 10 degrees C with 6.5 degrees C per km
  3. 15 degrees C with 1.98 degrees C per 1000 ft Correct answer.
  4. 15 degrees C with 2 degrees C per 1000 ft

Explanation

The ISA sets sea level temperature at 15 degrees C and a tropospheric lapse rate of about 1.98 degrees C per 1000 ft, equivalent to 6.5 degrees C per km. This rate applies up to the tropopause.

Question 5The Atmosphere: composition, structure, temperature and pressure

The tropopause is generally highest in which region?

  1. Over the subtropics in summer
  2. Over the equator Correct answer.
  3. Over the mid-latitudes in winter
  4. Over the poles in winter

Explanation

Warm equatorial air expands to greater heights, pushing the tropopause to around 16 to 18 km. Over the poles the colder, denser air column gives a tropopause as low as 8 to 10 km.

Question 6The Atmosphere: composition, structure, temperature and pressure

Which statement correctly describes the temperature change in the stratosphere with increasing height?

  1. It decreases then increases sharply
  2. It decreases steadily throughout
  3. It increases with height Correct answer.
  4. It remains constant throughout

Explanation

Ozone absorption of ultraviolet radiation warms the stratosphere, so temperature rises with height up to the stratopause. This inversion makes the layer stable and suppresses vertical motion.

Question 7The Atmosphere: composition, structure, temperature and pressure

Approximately what fraction of the atmosphere's mass lies within the lowest 5.5 km?

  1. About one tenth
  2. About one half Correct answer.
  3. About one quarter
  4. About three quarters

Explanation

Because air density falls rapidly with height, roughly half of the atmospheric mass is contained in the lowest 5.5 km. This is why most weather and most aviation activity occur in the lower troposphere.

Question 8The Atmosphere: composition, structure, temperature and pressure

What is the primary source of atmospheric water vapour?

  1. Evaporation from oceans and water bodies Correct answer.
  2. Combustion of fossil fuels
  3. Transpiration from deserts
  4. Volcanic outgassing

Explanation

Evaporation from the oceans supplies the great majority of atmospheric water vapour. Other sources contribute only small fractions of the total.

Question 9The Atmosphere: composition, structure, temperature and pressure

A parcel of air at sea level with a temperature of 20 degrees C is lifted dry adiabatically to 3000 ft. Using a dry adiabatic lapse rate of 3 degrees C per 1000 ft, what is its approximate temperature?

  1. 11 degrees C Correct answer.
  2. 20 degrees C
  3. 14 degrees C
  4. 17 degrees C

Explanation

The dry adiabatic lapse rate is about 3 degrees C per 1000 ft, so lifting 3000 ft cools the parcel by roughly 9 degrees C. Subtracting 9 from 20 gives about 11 degrees C.

Question 10The Atmosphere: composition, structure, temperature and pressure

In the ISA, what is the approximate pressure at 5000 ft above mean sea level?

  1. 700 hPa
  2. 843 hPa Correct answer.
  3. 1013 hPa
  4. 925 hPa

Explanation

Standard atmosphere tables give roughly 843 hPa at 5000 ft, reflecting a decrease of about 1 hPa per 30 ft near sea level. This pressure altitude relationship is fundamental to altimetry.

Question 11The Atmosphere: composition, structure, temperature and pressure

What is the approximate height of the 500 hPa pressure level in the standard atmosphere?

  1. 12000 m
  2. 8000 m
  3. 5500 m Correct answer.
  4. 3000 m

Explanation

In the ISA the 500 hPa surface lies near 5500 m (about 18000 ft). This level is widely used in upper-air charts because it represents the mid-troposphere.

Question 12The Atmosphere: composition, structure, temperature and pressure

What happens to the tropopause height when a deep low-pressure system with a cold core passes overhead?

  1. It falls because the cold air column is denser Correct answer.
  2. It rises sharply then stays constant
  3. It rises because of the low surface pressure
  4. It remains fixed regardless of temperature

Explanation

The tropopause height depends on the mean temperature of the air column below. A cold-core low has a contracted, denser column, so the tropopause is lower over such systems.

Question 13The Atmosphere: composition, structure, temperature and pressure

Which statement best explains why temperature increases with height in the stratosphere?

  1. Water vapour condenses and releases latent heat
  2. Ozone absorbs ultraviolet radiation from the sun Correct answer.
  3. Convection transfers heat upward from the troposphere
  4. The air is compressed by the layers above

Explanation

Ozone in the stratosphere absorbs solar ultraviolet radiation, converting it to heat. This warming increases with height and produces the temperature inversion characteristic of the layer.

Question 14The Atmosphere: composition, structure, temperature and pressure

A station reports a QNH of 1005 hPa. Approximately what is the pressure altitude of the aerodrome if its elevation is 2000 ft?

  1. About 2000 ft
  2. About 2240 ft Correct answer.
  3. About 1760 ft
  4. About 2400 ft

Explanation

Pressure altitude equals elevation plus 30 ft for every hPa that QNH is below 1013. The difference is 8 hPa, giving 240 ft to add to the 2000 ft elevation, so about 2240 ft.

Question 15The Atmosphere: composition, structure, temperature and pressure

What is the main reason air density decreases with increasing altitude?

  1. The proportion of oxygen increases with height
  2. Water vapour content increases with height
  3. Gravity becomes stronger at higher levels
  4. Pressure falls and temperature generally falls in the troposphere Correct answer.

Explanation

Density falls with height because pressure decreases and, in the troposphere, temperature also decreases. These two effects combine to reduce density under the gas laws.

Question 16The Atmosphere: composition, structure, temperature and pressure

Why does the pressure lapse rate decrease with height?

  1. Air density decreases with height, so less mass lies above Correct answer.
  2. Temperature increases with height throughout the atmosphere
  3. The proportion of heavy gases increases with height
  4. Gravity increases with height

Explanation

Pressure change with height is proportional to air density. As density falls with height, each successive metre of ascent removes less pressure, so the lapse rate becomes smaller.

Question 17The Atmosphere: composition, structure, temperature and pressure

In which atmospheric layer do most meteors burn up?

  1. Mesosphere Correct answer.
  2. Troposphere
  3. Thermosphere
  4. Stratosphere

Explanation

The mesosphere, roughly 50 to 85 km, is where most meteors burn up because of friction with the sparse air. It lies well above the layers used by conventional aircraft.

Question 18The Atmosphere: composition, structure, temperature and pressure

What is the principal effect of water vapour on atmospheric behaviour?

  1. It decreases the density of air at a given pressure and temperature Correct answer.
  2. It has no effect on weather
  3. It prevents all convection
  4. It absorbs visible light strongly

Explanation

Water vapour is less dense than dry air, so moist air has a lower density at the same pressure and temperature. It also provides latent heat on condensation, driving weather systems.

Question 19The Atmosphere: composition, structure, temperature and pressure

A surface temperature of 25 degrees C and a dew point of 15 degrees C are reported. Using the approximate saturated adiabatic lapse rate of 1.5 degrees C per 1000 ft above the condensation level, what is the approximate temperature of the air after lifting 6000 ft, with condensation occurring at about 4000 ft?

  1. About 7 degrees C Correct answer.
  2. About 19 degrees C
  3. About 13 degrees C
  4. About 22 degrees C

Explanation

The dry adiabatic rate applies up to the condensation level, cooling the parcel by about 12 degrees C over 4000 ft to near 13 degrees C. The remaining 2000 ft uses the saturated rate of 1.5 degrees C per 1000 ft, cooling about 3 degrees C to near 10 degrees C, so about 7 degrees C is the closest option.

Question 20The Atmosphere: composition, structure, temperature and pressure

What is the principal reason the tropopause acts as a lid on tropospheric weather?

  1. The temperature inversion suppresses vertical motion Correct answer.
  2. The air there contains too much water vapour
  3. Wind speeds are always zero at that level
  4. Pressure is too low for any cloud to exist

Explanation

The tropopause marks a change from decreasing to increasing temperature with height, creating a stable inversion. This stability inhibits the upward penetration of convection and cloud tops.

Question 21The Atmosphere: composition, structure, temperature and pressure

An aircraft flies from a warm air mass into a cold air mass at constant indicated altitude and constant QNH setting. What happens to the true altitude?

  1. It increases
  2. It decreases Correct answer.
  3. It first increases then returns
  4. It stays the same

Explanation

In cold air the pressure surfaces are compressed, so a given pressure level lies closer to the ground. Flying at constant indicated altitude in colder air therefore means a lower true altitude.

Question 22The Atmosphere: composition, structure, temperature and pressure

Why does the saturated adiabatic lapse rate vary with temperature and pressure?

  1. The dry adiabatic rate itself changes with height
  2. Gravity varies significantly within the troposphere
  3. Air density changes the gas constant at high altitude
  4. Latent heat release offsets some of the cooling, and the amount released depends on moisture capacity Correct answer.

Explanation

As a saturated parcel rises and cools, water vapour condenses and releases latent heat, slowing the cooling. Warm air holds more moisture, so more latent heat is released and the saturated rate is smaller at high temperatures.

Question 23The Atmosphere: composition, structure, temperature and pressure

A pressure reading of 900 hPa is recorded at a mountain station. Using the standard atmosphere, what is the approximate station elevation?

  1. About 1000 m Correct answer.
  2. About 5000 m
  3. About 3000 m
  4. About 7000 m

Explanation

In the ISA, 900 hPa occurs at roughly 1000 m, since pressure falls about 1 hPa per 8 m near the surface. The station is therefore at approximately 1000 m.

Question 24The Atmosphere: composition, structure, temperature and pressure

Which combination correctly describes the temperature and pressure changes occurring as air rises in the troposphere?

  1. Temperature falls and pressure rises
  2. Temperature rises and pressure rises
  3. Temperature falls and pressure falls Correct answer.
  4. Temperature rises and pressure falls

Explanation

As air rises, the decreasing weight of overlying air reduces pressure, and expansion causes cooling. Both temperature and pressure therefore decrease with height in the troposphere.

Question 25The Atmosphere: composition, structure, temperature and pressure

Which gas makes up the largest proportion of the Earth's atmosphere by volume?

  1. Argon
  2. Oxygen
  3. Nitrogen Correct answer.
  4. Carbon dioxide

Explanation

Nitrogen accounts for about 78% of the atmosphere by volume, while oxygen is about 21%. Argon and carbon dioxide are present in much smaller amounts.

Question 26The Atmosphere: composition, structure, temperature and pressure

What is the approximate environmental lapse rate in the troposphere according to the International Standard Atmosphere?

  1. 4.5°C per 1000 ft
  2. 3.0°C per 1000 ft
  3. 2.0°C per 1000 ft Correct answer.
  4. 1.5°C per 1000 ft

Explanation

The ISA assumes a uniform temperature decrease of 6.5°C per km, which is approximately 2°C per 1000 ft. This is the standard environmental lapse rate used in aviation calculations.

Question 27The Atmosphere: composition, structure, temperature and pressure

Which atmospheric layer is characterised by a temperature inversion and contains the ozone layer?

  1. Stratosphere Correct answer.
  2. Mesosphere
  3. Thermosphere
  4. Troposphere

Explanation

The stratosphere contains the ozone layer, which absorbs ultraviolet radiation and causes temperature to increase with height, creating an inversion. The troposphere has decreasing temperature, while the mesosphere and thermosphere have different temperature profiles.

Question 28The Atmosphere: composition, structure, temperature and pressure

What is the primary cause of the decrease in atmospheric pressure with increasing altitude?

  1. Change in gravitational acceleration
  2. Decrease in air density Correct answer.
  3. Increase in humidity
  4. Decrease in air temperature

Explanation

Atmospheric pressure is the weight of the air above a given level. As altitude increases, there is less air above, so both density and pressure decrease. The primary cause is the reduction in air density, which is directly related to pressure through the ideal gas law.

Question 29The Atmosphere: composition, structure, temperature and pressure

Which of the following is a variable gas in the atmosphere that significantly influences weather?

  1. Argon
  2. Oxygen
  3. Nitrogen
  4. Water vapour Correct answer.

Explanation

Water vapour is highly variable in space and time, ranging from nearly 0% to about 4% by volume. It is the source of clouds and precipitation and plays a key role in energy transfer through latent heat.

Question 30The Atmosphere: composition, structure, temperature and pressure

In which atmospheric layer does the temperature increase with height due to absorption of solar ultraviolet radiation?

  1. Stratosphere Correct answer.
  2. Mesosphere
  3. Troposphere
  4. Thermosphere

Explanation

The stratosphere contains ozone that absorbs ultraviolet radiation, causing temperature to rise with height. This creates a stable layer that inhibits vertical motion.

Question 31The Atmosphere: composition, structure, temperature and pressure

What is the approximate height of the tropopause in the International Standard Atmosphere?

  1. 26,000 ft
  2. 36,000 ft Correct answer.
  3. 18,000 ft
  4. 50,000 ft

Explanation

The ISA defines the tropopause at 11 km (approximately 36,000 ft), where the temperature is -56.5°C. Above this, the stratosphere begins with an isothermal layer.

Question 32The Atmosphere: composition, structure, temperature and pressure

What is the primary reason for the formation of the tropopause?

  1. The decrease in pressure with height
  2. The convective overturning of air
  3. The absorption of solar radiation by ozone Correct answer.
  4. The increase in humidity with height

Explanation

The tropopause exists because ozone in the stratosphere absorbs ultraviolet radiation, warming the air and creating a stable layer that suppresses vertical motion. This marks the boundary between the troposphere and stratosphere.

Question 33The Atmosphere: composition, structure, temperature and pressure

What is the approximate temperature at the tropopause in the International Standard Atmosphere?

  1. -70°C
  2. -20°C
  3. -40°C
  4. -56.5°C Correct answer.

Explanation

In the ISA, the temperature decreases at 6.5°C per km from 15°C at sea level to -56.5°C at 11 km (the tropopause). Above that, it remains constant up to 20 km.

Question 34The Atmosphere: composition, structure, temperature and pressure

Which of the following is the correct order of atmospheric layers from the surface upward?

  1. Troposphere, stratosphere, thermosphere, mesosphere
  2. Stratosphere, troposphere, mesosphere, thermosphere
  3. Troposphere, mesosphere, stratosphere, thermosphere
  4. Troposphere, stratosphere, mesosphere, thermosphere Correct answer.

Explanation

The atmosphere is divided into layers based on temperature profile: troposphere (0-11 km), stratosphere (11-50 km), mesosphere (50-85 km), and thermosphere (above 85 km).

Question 35The Atmosphere: composition, structure, temperature and pressure

What is the approximate pressure at sea level in the International Standard Atmosphere?

  1. 1020 hPa
  2. 1013.25 hPa Correct answer.
  3. 1050 hPa
  4. 1000 hPa

Explanation

The ISA sea level pressure is 1013.25 hPa (29.92 inHg). This value is used as a reference for pressure altitude and altimeter settings.

Question 36The Atmosphere: composition, structure, temperature and pressure

What is the primary reason for the decrease in air temperature with height in the troposphere?

  1. The expansion of rising air parcels
  2. The increase in ozone concentration
  3. The decrease in atmospheric pressure
  4. The absorption of solar radiation by the ground Correct answer.

Explanation

The troposphere is heated primarily from below by the Earth's surface, which absorbs solar radiation and warms the air above it. As altitude increases, the distance from the heat source increases, leading to lower temperatures.

Question 37The Atmosphere: composition, structure, temperature and pressure

What is the approximate height of the 300 hPa pressure level in the International Standard Atmosphere?

  1. 30,000 ft Correct answer.
  2. 18,000 ft
  3. 40,000 ft
  4. 10,000 ft

Explanation

In the ISA, the 300 hPa level is at approximately 30,000 ft (9.1 km). This is a common level used for upper-air charts and jet stream analysis.

Question 38The Atmosphere: composition, structure, temperature and pressure

Which statement correctly describes the variation of atmospheric pressure with altitude?

  1. Pressure increases with height in the troposphere
  2. Pressure decreases at a constant rate with height
  3. Pressure decreases more rapidly at higher altitudes
  4. Pressure decreases more rapidly at lower altitudes Correct answer.

Explanation

Because air is compressible, the pressure decrease is not linear. Near the surface, the air is denser, so pressure falls more quickly with height; at higher altitudes, the air is less dense, and the pressure decrease is more gradual.

Question 39The Atmosphere: composition, structure, temperature and pressure

What is the primary reason the environmental lapse rate is generally less than the dry adiabatic lapse rate in the troposphere?

  1. The presence of water vapour
  2. The release of latent heat during condensation Correct answer.
  3. The mixing of air masses
  4. The absorption of solar radiation by the ground

Explanation

When air rises and cools to its dew point, water vapour condenses, releasing latent heat. This warms the air and reduces the rate of cooling, making the environmental lapse rate less than the dry adiabatic rate in moist conditions.

Question 40The Atmosphere: composition, structure, temperature and pressure

What is the approximate density of air at sea level in the International Standard Atmosphere?

  1. 0.500 kg/m³
  2. 2.000 kg/m³
  3. 1.225 kg/m³ Correct answer.
  4. 1.000 kg/m³

Explanation

The ISA sea level density is 1.225 kg/m³. This value is used in aircraft performance calculations and is derived from the ideal gas law using standard sea level temperature and pressure.

Question 41Pressure, altimetry and standard atmosphere

In the ICAO Standard Atmosphere at mean sea level, the pressure and temperature are taken as:

  1. 1013.25 hPa and 0 degrees Celsius
  2. 1000 hPa and 15 degrees Celsius
  3. 1013.25 hPa and 15 degrees Celsius Correct answer.
  4. 1000 hPa and 0 degrees Celsius

Explanation

The ICAO Standard Atmosphere fixes mean sea level pressure at 1013.25 hPa and mean sea level temperature at 15 degrees Celsius, with a standard lapse rate of about 1.98 degrees Celsius per 1000 ft.

Question 42Pressure, altimetry and standard atmosphere

The pressure lapse rate in the lower atmosphere near mean sea level is approximately:

  1. 1 hPa per 30 ft Correct answer.
  2. 1 hPa per 1000 ft
  3. 1 hPa per 300 ft
  4. 1 hPa per 100 ft

Explanation

Near sea level pressure decreases by roughly 1 hPa for every 30 ft of ascent, which is why an altimeter subscale change of about 1 hPa corresponds to roughly 30 ft of altitude change.

Question 43Pressure, altimetry and standard atmosphere

QNH is defined as the altimeter subscale setting which, when set on an altimeter at aerodrome elevation, causes the altimeter to indicate:

  1. height above the aerodrome
  2. zero
  3. pressure altitude
  4. aerodrome elevation Correct answer.

Explanation

QNH is the sea level pressure derived from station pressure, so with QNH set the altimeter reads aerodrome elevation when the aircraft is on the ground at that aerodrome.

Question 44Pressure, altimetry and standard atmosphere

With QFE set on the altimeter, an aircraft standing on the aerodrome will indicate:

  1. aerodrome elevation
  2. pressure altitude
  3. zero Correct answer.
  4. standard altitude

Explanation

QFE is the station pressure at aerodrome level, so setting it makes the altimeter read zero on the ground and thereafter indicate height above the aerodrome.

Question 45Pressure, altimetry and standard atmosphere

Which pressure setting is set in the altimeter subscale to indicate pressure altitude?

  1. The regional QNH
  2. QFE
  3. QNH
  4. 1013.25 hPa Correct answer.

Explanation

Pressure altitude is the altitude indicated when the altimeter is set to the standard pressure 1013.25 hPa, also called QNE.

Question 46Pressure, altimetry and standard atmosphere

An aircraft flying at a constant indicated altitude from a region of high pressure into a region of low pressure, without changing the subscale, will:

  1. be progressively lower than indicated Correct answer.
  2. maintain true altitude
  3. be progressively higher than indicated
  4. show a decreasing indicated altitude

Explanation

When flying from high into low pressure at constant indicated altitude, the true altitude decreases, so the aircraft is lower than the altimeter suggests. This is the basis of the rule 'high to low, watch out below'.

Question 47Pressure, altimetry and standard atmosphere

An aircraft flying at a constant indicated altitude from cold air into warm air, with no subscale change, will have a true altitude that is:

  1. unchanged throughout
  2. equal to pressure altitude
  3. lower than indicated in the warm air
  4. higher than indicated in the warm air Correct answer.

Explanation

In warm air the pressure levels are farther apart, so for a given indicated altitude the aircraft is higher above the ground than in cold air. Flying from cold to warm therefore increases true altitude above the indicated value.

Question 48Pressure, altimetry and standard atmosphere

When the temperature is colder than standard, the altimeter error causes the aircraft to be:

  1. lower than the indicated altitude Correct answer.
  2. exactly at the indicated altitude
  3. higher than the indicated altitude
  4. at pressure altitude

Explanation

In air colder than standard the pressure levels are compressed, so the aircraft is closer to the ground than the altimeter indicates. This is why terrain clearance must be increased in very cold conditions.

Question 49Pressure, altimetry and standard atmosphere

An aerodrome has elevation 1000 ft and QNH 1013 hPa. Using 1 hPa per 30 ft, the approximate QFE is:

  1. 1013 hPa
  2. 1046 hPa
  3. 980 hPa Correct answer.
  4. 1000 hPa

Explanation

Pressure decreases by about 1 hPa per 30 ft, so over 1000 ft the fall is roughly 33 hPa. Subtracting this from QNH gives a QFE of about 980 hPa.

Question 50Pressure, altimetry and standard atmosphere

A change of 1 hPa in the altimeter subscale setting corresponds to an approximate altitude change of:

  1. 10 ft
  2. 30 ft Correct answer.
  3. 100 ft
  4. 300 ft

Explanation

Because pressure falls about 1 hPa per 30 ft near sea level, a 1 hPa subscale change shifts the indicated altitude by roughly 30 ft.