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PPL Meteorology practice questions

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Question 1Meteorology

In the ICAO standard atmosphere, what is the assumed mean sea-level pressure and temperature?

  1. 1000 hPa and 15 °C
  2. 1013.25 hPa and 15 °C Correct answer.
  3. 1013.25 hPa and 0 °C
  4. 1000 hPa and 0 °C

Explanation

The ICAO International Standard Atmosphere fixes sea-level pressure at 1013.25 hPa and sea-level temperature at 15 °C, with a lapse rate of 1.98 °C per 1000 ft in the lower layer. These reference values underpin pressure altimeter calibration and aircraft performance calculations.

Question 2Meteorology

An aircraft flies from a region of high pressure toward a region of low pressure without resetting the subscale. If the altimeter subscale remains unchanged, the aircraft's true altitude will:

  1. be lower than the indicated altitude Correct answer.
  2. oscillate around the indicated altitude
  3. equal the indicated altitude
  4. be higher than the indicated altitude

Explanation

Flying from high to low pressure with a fixed subscale makes the altimeter over-read, so the true altitude is lower than indicated. This is the basis of the mnemonic 'high to low, look out below'. The pilot should update the subscale to the local QNH to keep the indication accurate.

Question 3Meteorology

What does the term QFE represent at an aerodrome?

  1. The pressure at aerodrome level Correct answer.
  2. The pressure at the standard datum of 1013.25 hPa
  3. The pressure at the tropopause
  4. The pressure reduced to mean sea level

Explanation

QFE is the atmospheric pressure at the aerodrome reference point, so an altimeter set to QFE reads zero on the ground. QNH, by contrast, is the pressure reduced to mean sea level. Using QFE simplifies height above aerodrome during approach and landing.

Question 4Meteorology

Which cloud type is most characteristic of strong vertical instability and is associated with thunderstorms?

  1. Cumulonimbus Correct answer.
  2. Altostratus
  3. Stratus
  4. Cirrostratus

Explanation

Cumulonimbus clouds develop in conditionally unstable air with strong updrafts and reach the tropopause, producing thunderstorms, hail and heavy showers. The other options are stratiform or high-level clouds typical of stable or weakly unstable conditions.

Question 5Meteorology

In the Northern Hemisphere, the wind flows around a low-pressure system at the surface in which direction?

  1. Clockwise and inward
  2. Counterclockwise and inward Correct answer.
  3. Counterclockwise and outward
  4. Clockwise and outward

Explanation

In the Northern Hemisphere, Coriolis deflection to the right produces counterclockwise circulation around a low, with surface friction causing inflow toward the centre. Around a high, the flow is clockwise and outward. This determines the typical weather pattern associated with each system.

Question 6Meteorology

A pilot observes that the wind reported at 2000 ft is 250/40 while the surface wind is 180/10. What does this difference illustrate?

  1. Wind direction is constant with height in the friction layer
  2. Wind backs and weakens with height due to reduced friction
  3. Wind veers and strengthens with height due to reduced friction Correct answer.
  4. Wind veers with height only in the Southern Hemisphere

Explanation

Within the friction layer, surface drag slows the wind and reduces Coriolis deflection; with height, friction decreases and the wind turns toward the geostrophic direction and increases in speed. In the Northern Hemisphere this is a veer (clockwise shift). This explains why the surface wind differs markedly from the gradient wind.

Question 7Meteorology

What is the standard dry adiabatic lapse rate used in aviation meteorology?

  1. 6 °C per 1000 ft
  2. 0.65 °C per 100 m
  3. 1.98 °C per 1000 ft
  4. 3 °C per 1000 ft Correct answer.

Explanation

The dry adiabatic lapse rate is approximately 3 °C per 1000 ft (about 9.8 °C per km). It applies to unsaturated air parcels rising or descending without exchanging heat. The saturated adiabatic rate is lower because of latent heat release.

Question 8Meteorology

An aircraft climbing through a temperature inversion in a stable layer will typically experience:

  1. smooth air with little turbulence Correct answer.
  2. severe clear-air turbulence
  3. icing only if the air is unsaturated
  4. rapid convective updraughts

Explanation

Temperature inversions are strongly stable layers that suppress vertical motion, so the air is usually smooth. Turbulence may occur at the inversion boundary where wind shear exists, but the inversion itself is stable. Convective activity belongs to unstable layers, not inversions.

Question 9Meteorology

What is the primary cause of orographic lifting?

  1. Air cooling by nocturnal radiation
  2. Air converging at the intertropical convergence zone
  3. Air descending in a high-pressure system
  4. Air being forced upward over rising terrain Correct answer.

Explanation

Orographic lifting occurs when prevailing wind is forced to rise over hills or mountains, causing adiabatic cooling, condensation and often heavy precipitation on the windward side. The lee side commonly experiences descending, warming air and a rain shadow. This is distinct from thermal or frontal lifting.

Question 10Meteorology

Which condition is required for the formation of radiation fog?

  1. Strong wind and unstable air
  2. Rapid surface heating after sunrise
  3. Clear skies, light wind and high relative humidity Correct answer.
  4. Warm air moving over a cold surface with strong wind

Explanation

Radiation fog forms when the ground cools by nocturnal radiation under clear skies and light wind, cooling the air above to its dew point. Strong wind mixes the air and prevents cooling, while instability favours mixing rather than a shallow fog layer. The result is a shallow, dense fog that usually dissipates after sunrise.

Question 11Meteorology

In a METAR, what does the group 'RVR 1200' indicate?

  1. Visibility of 1200 metres along the runway only
  2. Cloud base at 1200 feet
  3. Runway visual range of 1200 metres Correct answer.
  4. Wind speed of 12 knots

Explanation

RVR denotes runway visual range, the distance a pilot can see along the runway, expressed in metres. It differs from prevailing visibility, which is reported for the aerodrome as a whole. RVR is important for low-visibility operations and approach minima.

Question 12Meteorology

What does a TAF of 'BECMG 1214 4000 RA' mean?

  1. At 1200 UTC conditions will suddenly change to 4000 m with rain
  2. Between 1200 and 1400 UTC conditions will temporarily be 4000 m with rain
  3. From 1200 to 1400 UTC rain will cease and visibility will improve to 4000 m
  4. Between 1200 and 1400 UTC conditions will gradually become visibility 4000 m with rain Correct answer.

Explanation

BECMG indicates a gradual, permanent change, and the time group 1214 means the change is expected between 1200 and 1400 UTC. The following group gives the new conditions: 4000 m visibility with rain. TEMPO, by contrast, denotes temporary fluctuations.

Question 13Meteorology

What is the significance of a SIGMET?

  1. It warns of significant en-route weather hazardous to aircraft Correct answer.
  2. It reports routine aerodrome conditions
  3. It gives a long-term seasonal climate outlook
  4. It lists runway friction coefficients

Explanation

A SIGMET is issued to warn of significant meteorological phenomena en route, such as severe turbulence, icing, thunderstorms or volcanic ash, that may affect flight safety. It is not a routine aerodrome report; that is the METAR. SIGMETs are distributed to aircraft in flight and to briefing offices.

Question 14Meteorology

A pilot encounters airframe icing in stratiform cloud at -5 °C. Which type of icing is most likely?

  1. Mixed ice
  2. Rime ice Correct answer.
  3. Clear ice
  4. Frost

Explanation

Stratiform clouds contain many small supercooled droplets, which freeze rapidly on impact and trap air, producing opaque, brittle rime ice. Clear ice forms from large droplets in convective clouds, where the water spreads before freezing. Frost forms by deposition on cold surfaces rather than by droplet impact.

Question 15Meteorology

What is the primary hazard to an aircraft approaching a microburst?

  1. A gradual decrease in wind speed over several minutes
  2. A uniform increase in pressure along the approach path
  3. A sudden headwind followed by a strong downdraught and tailwind Correct answer.
  4. A steady crosswind with no vertical component

Explanation

A microburst produces a strong downdraught that spreads out at the surface, giving an initial headwind and performance increase, followed by a sudden downdraught and tailwind with a large performance loss close to the ground. This can cause an unrecoverable sink rate. Pilots should avoid thunderstorm downdraught areas entirely.

Question 16Meteorology

What does a QNH of 1020 hPa indicate to a pilot setting the altimeter?

  1. The altimeter will read aerodrome elevation on the ground Correct answer.
  2. The altimeter will read pressure altitude on the ground
  3. The altimeter will read zero on the ground
  4. The altimeter will read flight level on the ground

Explanation

QNH is the pressure reduced to mean sea level, so an altimeter set to QNH reads elevation above mean sea level when the aircraft is on the ground. This is why QNH is used for terrain clearance during approach. QFE, by contrast, is set to read zero at the aerodrome.

Question 17Meteorology

Which factor most strongly determines the height of the tropopause?

  1. Surface pressure alone
  2. Longitude and local time
  3. Wind direction at the surface
  4. Latitude and surface temperature Correct answer.

Explanation

The tropopause is highest over the tropics, where the troposphere is warmed and expanded, and lowest over the poles. It also varies with season and synoptic conditions. Longitude, local time and surface wind do not directly determine its height.

Question 18Meteorology

In the Southern Hemisphere, the geostrophic wind blows with:

  1. low pressure to the right
  2. low pressure to the left Correct answer.
  3. no consistent relationship to pressure
  4. high pressure to the left

Explanation

Geostrophic balance aligns the wind parallel to the isobars with low pressure on the left in the Southern Hemisphere, because Coriolis deflects to the left there. In the Northern Hemisphere the low is on the right. This follows from the sign of the Coriolis parameter.

Question 19Meteorology

A cold front passing an aerodrome typically brings which sequence of weather?

  1. A band of showers and a wind veer with a temperature fall Correct answer.
  2. Clear skies and a gradual wind backing
  3. Steady drizzle and a gradual temperature rise
  4. Persistent fog and no wind change

Explanation

A cold front brings a relatively narrow band of showers or thunderstorms, a sharp wind veer, a temperature drop and a pressure rise after passage. The air behind the front is cooler and often more unstable. Warm fronts, by contrast, bring steady precipitation and gradual changes.

Question 20Meteorology

What is the main reason for the diurnal variation in surface wind speed over land?

  1. The Coriolis force reverses direction at night
  2. Nighttime heating increases surface friction
  3. Pressure systems move only during the day
  4. Daytime heating causes mixing that brings stronger upper winds to the surface Correct answer.

Explanation

During the day, surface heating produces convective mixing that transfers momentum from the stronger winds aloft down to the surface, increasing surface wind speed. At night, stable air and reduced mixing decouple the surface from the stronger upper winds, so the surface wind weakens. This diurnal pattern is typical over land.

Question 21Meteorology

What does the term 'freezing rain' mean in aviation meteorology?

  1. Rain that falls as ice pellets
  2. Snow that melts before reaching the ground
  3. Rain that freezes on impact with a surface Correct answer.
  4. Rain falling at a temperature below -20 °C

Explanation

Freezing rain occurs when supercooled water droplets fall and freeze on impact with surfaces or an aircraft, producing severe clear icing. It often signals a warm layer aloft above a sub-freezing surface layer. Ice pellets indicate that droplets froze before reaching the ground.

Question 22Meteorology

An aircraft flying at flight level 200 uses the standard pressure setting. What does the altimeter indicate?

  1. Height above aerodrome
  2. Pressure altitude Correct answer.
  3. True altitude
  4. Density altitude

Explanation

With the subscale set to 1013.25 hPa, the altimeter indicates pressure altitude, the altitude corresponding to a standard pressure datum. True altitude requires local pressure and temperature corrections. Density altitude accounts for temperature and is a performance concept, not an altimeter reading.

Question 23Meteorology

Which statement best describes the formation of advection fog?

  1. Air cools by nocturnal radiation under clear skies
  2. Air is lifted over a mountain barrier
  3. Cold air moves over a warm surface and is heated
  4. Warm moist air moves over a colder surface and cools to its dew point Correct answer.

Explanation

Advection fog forms when warm, moist air is transported over a colder surface, cooling the air below its dew point and producing fog. It can occur with moderate wind and is common over cold sea surfaces. Radiation fog, by contrast, forms by nocturnal cooling of the ground.

Question 24Meteorology

A pilot planning a flight over mountainous terrain notes a strong temperature inversion aloft with a jet stream nearby. Which hazard is most relevant?

  1. Clear-air turbulence at the inversion boundary and jet stream Correct answer.
  2. Severe icing in clear air
  3. Radiation fog at cruise level
  4. Microbursts at high altitude

Explanation

Strong wind shear at the top of an inversion and near the jet stream produces clear-air turbulence, which can be severe and is not visible on weather radar. Radiation fog forms near the surface, and microbursts are low-level convective phenomena. Clear-air icing is unlikely without visible moisture.

Question 25Meteorology

What is the relationship between relative humidity and temperature for a fixed amount of water vapour?

  1. Relative humidity equals the dew point at all temperatures
  2. Relative humidity increases as temperature increases
  3. Relative humidity decreases as temperature increases Correct answer.
  4. Relative humidity is independent of temperature

Explanation

For a fixed water-vapour content, warming the air increases its saturation capacity, so relative humidity falls. Cooling the air reduces the capacity and raises relative humidity, eventually reaching saturation at the dew point. This relationship explains why fog and dew form on cooling.

Question 26Meteorology

In a METAR, the altimeter setting group 'Q1013' reports which quantity?

  1. The sea-surface pressure in inches of mercury
  2. The QFE in hectopascals
  3. The QNH in hectopascals Correct answer.
  4. The pressure altitude in feet

Explanation

The Q group in a METAR always reports QNH, the pressure reduced to mean sea level, expressed in whole hectopascals. A pilot who sets this value on the altimeter subscale reads aerodrome elevation when on the ground.

Question 27Meteorology

A METAR reports 'BKN008 OVC015'. What cloud conditions does this describe?

  1. A broken layer at 800 ft with overcast above at 1500 ft Correct answer.
  2. A broken layer at 800 m with overcast at 1500 m
  3. Scattered cloud at 800 ft and broken cloud at 1500 ft
  4. Broken cloud at 800 ft only, with no higher layers reported

Explanation

In METAR cloud groups the three digits give height above the aerodrome in hundreds of feet, so 008 means 800 ft and 015 means 1500 ft. BKN denotes a broken layer (5-7 oktas) and OVC an overcast layer (8 oktas).

Question 28Meteorology

What does a reported wind of 'VRB03KT' indicate at an aerodrome?

  1. Wind speed is variable between 0 and 3 knots
  2. Wind is gusting to 3 knots from a variable direction
  3. Wind is from 030 degrees at 3 knots
  4. Wind direction is variable with a speed of 3 knots Correct answer.

Explanation

VRB replaces the direction digits when the direction is variable or too light to determine reliably, and 03KT is the mean speed in knots. The two-letter KT suffix confirms the units are knots.

Question 29Meteorology

What is the standard sea-level pressure setting used for the lower altimeter subscale in the standard atmosphere?

  1. 0999 hPa
  2. 1000 hPa
  3. 1023 hPa
  4. 1013.25 hPa Correct answer.

Explanation

The International Standard Atmosphere defines mean sea-level pressure as 1013.25 hPa, equivalent to 29.92 inHg, at a temperature of 15 °C. Setting this value gives pressure altitude and defines the transition level environment used for flight levels.

Question 30Meteorology

Which cloud genus is composed predominantly of ice crystals and appears as a thin, white, fibrous veil high in the troposphere?

  1. Altocumulus
  2. Stratocumulus
  3. Cirrus Correct answer.
  4. Cumulus congestus

Explanation

Cirrus forms at high levels where temperatures are well below freezing, so it consists of ice crystals and has a wispy, fibrous appearance. Its thinness means it casts little or no shadow and often heralds an approaching warm front.

Question 31Meteorology

What does the term 'CB' denote in a routine aerodrome report or forecast?

  1. Cumulus breaking layer
  2. Cumulonimbus cloud Correct answer.
  3. Cumulus base
  4. Cirrus band

Explanation

CB is the standard abbreviation for cumulonimbus, the deep convective cloud associated with thunderstorms, severe turbulence and icing. Its presence in a TAF or METAR is a strong warning of hazardous conditions.

Question 32Meteorology

How does air density change as an aircraft climbs in the standard atmosphere?

  1. Density decreases because pressure falls faster than temperature falls Correct answer.
  2. Density remains constant up to the tropopause
  3. Density decreases only because of falling temperature
  4. Density increases because temperature decreases

Explanation

In the troposphere both pressure and temperature fall with height, but the pressure decrease dominates, so density falls steadily. This is why true airspeed is higher than indicated airspeed at altitude for the same power setting.

Question 33Meteorology

Which instrument setting must a pilot use to read aerodrome elevation on the ground before take-off?

  1. QNH Correct answer.
  2. QFE
  3. Standard 1013.25 hPa
  4. QNE

Explanation

With QNH set, the altimeter reads elevation above mean sea level at the aerodrome, which is the value published on charts. QFE would read zero at the reference point instead.

Question 34Meteorology

An aerodrome reports a temperature of +28 °C and a dewpoint of +12 °C. What does this indicate about the likelihood of low cloud or fog?

  1. Cumulonimbus is guaranteed because of the high temperature
  2. Low cloud and fog are unlikely because the spread is large Correct answer.
  3. Relative humidity is close to 100 percent
  4. Fog is imminent because the dewpoint is above 10 °C

Explanation

The spread between temperature and dewpoint is 16 °C, so the air must cool substantially before saturation occurs. A large spread therefore makes fog and low stratus unlikely in the near term.

Question 35Meteorology

A parcel of unsaturated air at 20 °C is lifted 1000 ft dry-adiabatically. Using a dry adiabatic lapse rate of 3 °C per 1000 ft, what is its new temperature?

  1. 20 °C
  2. 14 °C
  3. 17 °C Correct answer.
  4. 23 °C

Explanation

An unsaturated parcel cools at the dry adiabatic rate of about 3 °C per 1000 ft of ascent. Lifting 1000 ft therefore reduces the temperature from 20 °C to 17 °C, provided no condensation occurs.

Question 36Meteorology

Air flowing from the sea onto a warm land surface in winter is most likely to produce which phenomenon?

  1. Orographic cloud on the coast
  2. Advection fog over the land Correct answer.
  3. Radiation fog over the sea
  4. Freezing drizzle inland

Explanation

When relatively warm, moist maritime air moves over a colder land surface, it is cooled from below to its dewpoint and advection fog forms. This differs from radiation fog, which depends on nocturnal cooling of the ground under clear skies.

Question 37Meteorology

An aircraft flies from a region of high pressure toward a region of lower pressure without resetting the altimeter. If the pilot maintains a constant indicated altitude, what happens to the true altitude?

  1. True altitude stays equal to indicated altitude
  2. True altitude decreases below the indicated value Correct answer.
  3. True altitude becomes equal to pressure altitude
  4. True altitude increases above the indicated value

Explanation

The rule is 'high to low, look out below': flying toward lower pressure with an unchanged subscale makes the aircraft descend relative to the pressure surfaces. Indicated altitude stays constant while true height above the ground falls, creating a terrain-clearance risk.

Question 38Meteorology

What is the defining characteristic of a warm front as it passes an observing station?

  1. Persistent clear skies with no change in air mass
  2. Rapid clearing with a veer of wind and a fall in temperature
  3. A gradual approach of layered cloud followed by steady precipitation and a slow temperature rise Correct answer.
  4. A sudden line of cumulonimbus with violent gusts and a sharp temperature fall

Explanation

Warm fronts slope gently, so cirrus appears well ahead of the surface front, followed by altostratus and stratus with continuous precipitation. Because the advancing air is warmer, temperature rises slowly after passage and the wind veers.

Question 39Meteorology

What is the primary reason that thunderstorms are more frequent over land in tropical regions during the afternoon?

  1. Sea breezes always suppress convection over land
  2. Coriolis force is strongest in the afternoon
  3. Strong surface heating destabilises the boundary layer and triggers convection Correct answer.
  4. The tropopause is lower over land, concentrating rising air

Explanation

Intense daytime insolation heats the land surface, steepening the lapse rate in the boundary layer until parcels become buoyant and rise freely. This diurnal destabilisation produces a peak in convective activity in the late afternoon.

Question 40Meteorology

What distinguishes a severe squall line as a hazard to aviation compared with ordinary isolated thunderstorms?

  1. It contains no lightning because it is entirely stratiform
  2. It produces a long, organised band of strong gusts, heavy rain and possible embedded tornadoes Correct answer.
  3. It is restricted to the stratosphere
  4. It only occurs over the ocean

Explanation

Squall lines are organised convective bands that can extend hundreds of kilometres and generate damaging straight-line gusts, intense rain and embedded tornadoes. The organised, fast-moving nature makes avoidance planning more difficult than for isolated cells.

Question 41Meteorology

How does a strong low-level temperature inversion affect the dispersion of pollutants and the visibility near an aerodrome?

  1. It causes the air to become drier and clearer
  2. It has no effect on visibility because it is above the surface
  3. It promotes rapid vertical mixing and improves visibility
  4. It traps moisture and pollutants beneath the inversion, reducing visibility Correct answer.

Explanation

An inversion is a stable layer in which temperature rises with height, suppressing vertical motion. Moisture and pollutants accumulate below it, producing haze, mist or stratus and poor visibility.

Question 42Meteorology

What does a TAF group of 'TEMPO 1012/1014 2500 SHRA' indicate?

  1. Permanent deterioration after 1400 UTC with 2500 ft cloud base
  2. A forecast of 2500 ft cloud base during the whole period
  3. Temporary wind from 250 degrees at 12 knots
  4. Temporary fluctuations between 1200 and 1400 UTC with 2500 m visibility and rain showers Correct answer.

Explanation

TEMPO introduces temporary fluctuations expected to last less than an hour at a time within the stated period. The numbers 2500 give visibility in metres and SHRA denotes rain showers.

Question 43Meteorology

An aircraft on approach experiences a sudden increase in headwind followed by a sharp decrease. What is the operational significance of this sequence?

  1. The wind change has no effect on indicated airspeed
  2. The aircraft will gain performance on both changes
  3. The aircraft may first rise above the glidepath and then sink below it Correct answer.
  4. The aircraft will maintain a constant sink rate throughout

Explanation

A headwind increase raises indicated airspeed and lift, causing the aircraft to balloon above the path; the subsequent decrease produces the opposite effect and a sink below the path. This windshear sequence is a recognised low-level hazard requiring prompt correction.

Question 44Meteorology

What is the primary mechanism by which a sea breeze circulation develops on a sunny day?

  1. Falling pressure over the sea draws air offshore
  2. Coriolis force turns the wind onshore at the coast
  3. Cold air subsides over the land and flows seaward
  4. Greater heating of land than sea creates a pressure gradient that drives cooler air onshore Correct answer.

Explanation

Land heats more rapidly than water, so air over land expands and pressure falls relative to the sea. Cooler, denser air then flows onshore near the surface, completing a closed circulation with a return flow aloft.

Question 45Meteorology

What is the significance of a tropical cyclone being reported as 'super typhoon' intensity near a planned route?

  1. The storm has weakened below gale force
  2. It means the system has become extratropical and harmless
  3. It indicates only heavy rain with no wind hazard
  4. Sustained winds are extremely high and the storm should be given a wide berth Correct answer.

Explanation

'Super typhoon' denotes a mature tropical cyclone with very high sustained winds, typically well above 100 knots, accompanied by severe turbulence and a dangerous eye wall. Safe practice is to route well clear of the forecast track and its uncertainty cone.

Question 46Meteorology

A pilot flying at 25 000 ft in the tropics encounters an anvil cloud spreading downwind from a cumulonimbus. Which hazard is most significant at this level?

  1. Dense radiation fog at flight level
  2. Severe turbulence and hail encountered in clear air near the anvil Correct answer.
  3. High relative humidity with no structural risk
  4. Strong orographic lift from the anvil

Explanation

Anvils can extend far downwind of the parent cell and contain severe turbulence and hail, sometimes in air that appears clear to radar. Pilots should avoid the anvil by a wide margin rather than treating it as harmless cloud debris.

Question 47Meteorology

A station at 2000 ft elevation reports QNH 1008 hPa. Using 1 hPa per 30 ft, what approximate QFE would the pilot expect at the aerodrome?

  1. About 941 hPa Correct answer.
  2. About 1008 hPa
  3. About 1075 hPa
  4. About 1020 hPa

Explanation

QFE is lower than QNH by roughly 1 hPa for every 30 ft of elevation. For 2000 ft the reduction is about 67 hPa, giving approximately 941 hPa.

Question 48Meteorology

Why does the tropopause generally reach its greatest height over the equator and its lowest over the poles?

  1. Ozone concentration is greatest over the equator
  2. Stronger tropical convection and a warmer troposphere allow deep ascent before the stable stratosphere is reached Correct answer.
  3. The equator has higher surface pressure than the poles
  4. Coriolis force is zero at the equator, raising the tropopause

Explanation

Vigorous tropical convection carries the troposphere to greater heights, and the warmer column requires a greater depth before the temperature profile becomes isothermal in the stratosphere. Polar air is colder and less convective, so the tropopause sits much lower.

Question 49Meteorology

An aircraft descends through a layer where the temperature increases with height while flying in cloud. What is the most likely consequence for airframe icing?

  1. Icing cannot occur because temperature is rising with height
  2. Supercooled droplets may exist in the stable layer, with the risk depending on the droplet temperature Correct answer.
  3. Icing will always be severe in an inversion
  4. The aircraft will encounter only ice crystals, not supercooled water

Explanation

A temperature inversion is a stable layer that can trap supercooled water droplets, so icing remains possible even though the temperature rises with height. The severity depends on the actual temperature and liquid water content, not on the inversion alone.

Question 50Meteorology

A pilot plans a flight along a valley with stable air and a strong cross-valley wind aloft. Which local effect should be anticipated?

  1. Mountain waves and possible severe turbulence downwind of the ridge Correct answer.
  2. Automatic formation of radiation fog in the afternoon
  3. A guaranteed sea breeze along the valley floor
  4. Uniform winds throughout the valley with no turbulence

Explanation

A strong wind crossing a ridge in a stable airstream can generate mountain waves, with rotor turbulence and downdrafts on the lee side. The hazard is greatest when the wind is roughly perpendicular to the ridge and increases with height.