Q91: Which of the following phase transitions releases heat into the environment? ^t50q91

• A) Solid to gaseous state
• B) Liquid to gaseous state
• C) Solid to liquid state
• D) Gaseous to liquid state

Correct: D)

Explanation: Condensation (gas to liquid) is exothermic — it releases latent heat that was absorbed during evaporation. This released heat is a key energy source for thunderstorm development and cloud growth. Sublimation (A, solid to gas), evaporation (B, liquid to gas), and melting (C, solid to liquid) all absorb heat from the environment. Only condensation and deposition release energy.

Q92: Where in the diagram are the strongest downdraughts located? ^t50q92

] - A) 1 - B) 2 - C) 4 - D) 3

Correct: D)

Explanation: Position 3 on the leeward side of the ridge experiences the strongest downdraughts as airflow descends and accelerates in the lee-side subsidence and rotor zone. Positions 1 and 4 on the windward slope have updrafts. Position 2 near the crest is transitional. Lee-side downdraughts are a significant hazard for gliders crossing ridges.

Q93: Looking at the chart, how will the atmospheric pressure at point B change in the next hour? ^t50q93

] - A) Rapid and regular variations. - B) A fall. - C) A rise. - D) No change.

Correct: C)

Explanation: The chart shows an anticyclone approaching point B. As a high-pressure system moves closer, local barometric pressure rises. Option A (rapid variations) is associated with convective activity. Option B (fall) would apply if a depression were approaching. Option D (no change) is unlikely with a moving pressure system.

Q94: An aircraft flies at FL 90 from Zurich (QNH 1020 hPa) to Munich (QNH 1005 hPa). While maintaining FL 90, does the true altitude above sea level change? ^t50q94

• A) No, it stays the same.
• B) It cannot be determined from the given data.
• C) Yes, the aircraft descends.
• D) Yes, the aircraft climbs.

Correct: C)

Explanation: Flight levels use standard pressure (1013.25 hPa). Flying from higher QNH (1020) to lower QNH (1005), the aircraft enters progressively lower-pressure air where pressure surfaces sit at lower true altitudes. The rule "high to low, look out below" applies — true altitude decreases while the flight level remains constant. Option D reverses the relationship.

Q95: An air mass at 18°C has a relative humidity of 29%. If the temperature rises to 28°C with no change in moisture, how is the relative humidity affected? ^t50q95

• A) It increases by 29%.
• B) It remains unchanged.
• C) It decreases.
• D) It increases by 10%.

Correct: C)

Explanation: When temperature rises from 18°C to 28°C, the saturation vapour pressure increases substantially while actual moisture stays constant. The ratio (relative humidity) therefore decreases. Options A and D wrongly claim an increase. Option B ignores the fundamental temperature dependence of relative humidity.

Q96: A warm air mass moves over a colder land surface and cools from below. How does this affect the air mass? ^t50q96

• A) It becomes more stable.
• B) Its relative humidity decreases.
• C) Atmospheric pressure falls.
• D) If clouds form, mainly convective clouds will develop.

Correct: A)

Explanation: Cooling from below weakens the temperature gradient — the bottom cools while the top stays warm, reducing the lapse rate and increasing stability. This favours stratiform cloud and fog, not convection. Option B is wrong because cooling increases relative humidity. Option D contradicts the stable conditions. Option C has no direct relationship.

Q97: On 1 August (summer time) you receive the Swiss GAFOR valid from 06:00 to 12:00 UTC. Your planned route shows "DDO". What does this mean? ^t50q97

• A) At 14:00 LT the flight route will be difficult.
• B) At 08:00 LT the flight route will be critical.
• C) At 11:00 LT the flight route will be critical.
• D) At 13:00 LT the flight route will be open.

Correct: D)

Explanation: GAFOR validity (06:00-12:00 UTC) in CEST (UTC+2): block 1 = 08-10 LT, block 2 = 10-12 LT, block 3 = 12-14 LT. "DDO": D (difficult), D (difficult), O (open). At 13:00 LT (= 11:00 UTC), block 3 applies = O (open). Options A, B, C misidentify the time block or condition.

Q98: How do the volume and temperature of a rising air mass change? ^t50q98

• A) Both decrease.
• B) Volume decreases, temperature increases.
• C) Both increase.
• D) Volume increases, temperature decreases.

Correct: D)

Explanation: Rising air enters lower-pressure layers, expanding adiabatically — volume increases. This expansion converts internal energy into work, cooling the air at approximately 1°C/100 m (DALR). Options A and B incorrectly say volume decreases. Option C incorrectly says temperature increases.

Q99: Under otherwise equal conditions, which type of precipitation is least hazardous for aviation? ^t50q99

• A) Heavy snowfall
• B) Rain showers
• C) Hail
• D) Drizzle

Correct: D)

Explanation: Drizzle consists of tiny droplets falling at light intensity from low stratus, causing only minor visibility reduction and no structural damage. Hail (C) causes severe structural damage. Heavy snowfall (A) drastically reduces visibility and causes icing. Rain showers (B) involve turbulence and reduced visibility. Drizzle is the least threatening.

Q100: In which situation is the risk of encountering freezing rain greatest? ^t50q100

• A) In summer during warm front passage.
• B) In winter during cold front passage.
• C) In winter during warm front passage.
• D) In summer during cold front passage.

Correct: C)

Explanation: Freezing rain requires warm air aloft (above 0°C) overriding a shallow sub-zero surface layer — the hallmark of a winter warm front. Rain from the warm layer passes through the freezing layer and supercools. Summer (A, D) rarely has sub-zero surfaces. Cold fronts (B, D) undercut warm air rather than overriding it, preventing the necessary warm-over-cold layering.

Q101: What does the wind barb symbol below represent? ^t50q101

] - A) Wind from NNE, 120 kt - B) Wind from NNE, 70 kt - C) Wind from SSW, 70 kt - D) Wind from SSW, 120 kt

Correct: C)

Explanation: The symbol shows wind from SSW with one pennant (50 kt) and two long barbs (20 kt) = 70 kt total. Wind barbs point FROM the wind source. Options A and B incorrectly identify the direction as NNE. Option D overstates the speed.

Q102: What is the name of the fog that develops when a moist air mass moves horizontally over a colder surface? ^t50q102

• A) Radiation fog
• B) Orographic fog
• C) Advection fog
• D) Sea spray

Correct: C)

Explanation: Advection fog forms when warm, moist air is transported horizontally over a colder surface, cooling from below to the dew point. Radiation fog (A) forms on calm clear nights from radiative cooling. Orographic fog (B) forms from terrain-forced lifting. Sea spray (D) is not a fog type.

Q103: Which typical Swiss weather pattern does the sketch below show? ^t50q103

] - A) Westerly wind situation - B) Bise situation - C) South Foehn situation - D) North Foehn situation

Correct: C)

Explanation: The sketch shows South Foehn (Sudföhn): air driven from the south over the Alps, losing moisture on the Italian side, then descending warm and dry on the northern slopes. Option A (westerly) involves Atlantic air. Option B (Bise) is a cold northeast wind. Option D (North Foehn) has the flow reversed, descending on the southern side.

Q104: Which altimeter setting must you select so that the instrument shows your height above a specific aerodrome (AAL)? ^t50q104

• A) The QNH of the aerodrome.
• B) The QFF of the aerodrome.
• C) The QFE of the aerodrome.
• D) The QNE of the aerodrome.

Correct: C)

Explanation: QFE is the atmospheric pressure at the aerodrome reference point. Setting QFE causes the altimeter to read zero on the ground and height above the aerodrome (AAL) in flight. QNH (A) shows altitude above MSL. QFF (B) is a meteorological reduction not used for altimetry. QNE (D) is the standard pressure for flight levels.

Q105: What are the wind speed and direction in this METAR? LFSB 171100Z 29004KT 220V340 9999 FEW043 28/17 Q1013 NOSIG= ^t50q105

• A) Wind from WNW, 4 knots, direction varying between SW and NNW.
• B) Wind from ESE, 4 knots, direction varying between NE and SSE.
• C) Wind from ESE, 4 knots, direction varying between SW and NNW.
• D) Wind from WNW, 4 knots, direction varying between NE and SSE.

Correct: A)

Explanation: "29004KT 220V340": 290° = WNW direction, 04 = 4 knots speed, varying between 220° (SW) and 340° (NNW). Options B and C misread 290° as ESE (which would be ~110°). Option D has the correct mean direction but wrong variability range.

Q106: During summer in central Europe, what phenomenon is typical of an advancing cold front when the warm air ahead has an unstable thermodynamic structure? ^t50q106

• A) Stratiform cloud cover.
• B) A rapid temperature rise after the front passes.
• C) Thunderstorm clouds.
• D) A rapid drop in atmospheric pressure after frontal passage.

Correct: C)

Explanation: When a cold front encounters warm unstable air in European summer, forced lifting triggers vigorous convection and cumulonimbus (thunderstorm) cloud development. Stratiform clouds (A) require stable air. Temperature falls, not rises (B), after cold front passage. Pressure rises, not drops (D), as dense cold air replaces the warm sector.

Q107: Along the route from LOWK to EDDP (dotted arrow), what weather phenomena should be anticipated? ^t50q107

] - A) Gradual temperature increase, tailwind, isolated thunderstorms. - B) Gradual temperature decrease, headwind, isolated thunderstorms. - C) Gradual temperature increase, headwind, no thunderstorms. - D) Gradual temperature decrease, tailwind, isolated thunderstorms.

Correct: B)

Explanation: Flying from LOWK (Klagenfurt) northward to EDDP (Leipzig), temperatures decrease with latitude, the synoptic pattern indicates headwind conditions, and summer convective activity produces isolated thunderstorms. Option A wrongly predicts warming and tailwind. Option C denies thunderstorm risk. Option D identifies a tailwind, which contradicts the chart.

Q108: Which type of cloud is most likely to cause heavy showers? ^t50q108

• A) Nimbostratus
• B) Altostratus
• C) Cirrocumulus
• D) Cumulonimbus

Correct: D)

Explanation: Cumulonimbus (Cb) clouds produce the heaviest showers, hail, and thunderstorms. They extend from near the surface to the tropopause with enormous water and ice content. Nimbostratus (A) produces steady rain, not heavy showers. Altostratus (B) produces light precipitation. Cirrocumulus (C) does not produce significant precipitation.

Q109: A radiosonde at high altitude in the Northern Hemisphere has a low pressure area to its north and a high pressure area to its south. In which direction will the wind carry the balloon? ^t50q109

• A) North
• B) West
• C) East
• D) South

Correct: B)

Explanation: Geostrophic wind blows parallel to isobars with low pressure to the left in the Northern Hemisphere. With low pressure north and high south, the pressure gradient points north, Coriolis deflects right, producing westward flow. The balloon is carried west. Options A, C, D misapply the Buys-Ballot law.

Q110: When air is forced upward by terrain and encounters unstable, moist layers, what are the resulting thunderstorms called? ^t50q110

• A) Cold front thunderstorms
• B) Orographic thunderstorms
• C) Thermal thunderstorms
• D) Warm front thunderstorms

Correct: B)

Explanation: When terrain mechanically forces air upward into moist, unstable layers, the resulting convective storms are orographic thunderstorms — driven by topographic lifting rather than frontal forcing (A, D) or purely thermal heating (C). They are common over mountain ranges in summer and can be persistent because the terrain continuously feeds the lift.

Q111: Which set of conditions favours the development of advection fog? ^t50q111

• A) Cold, humid air flowing over a warm ocean
• B) Moisture evaporating from warm, humid ground into cold air
• C) Warm, humid air flowing over a cold surface
• D) Warm, humid air cooling on a cloudy night

Correct: C)

Explanation: Advection fog forms when warm, moist air moves horizontally over a colder surface and cools from below to the dew point. Cold air over warm water (A) produces steam fog. Evaporation from warm ground into cold air (B) describes mixing fog. Cooling on a cloudy night (D) prevents the radiative cooling needed for fog because clouds block radiation.

Q112: Which process leads to the formation of advection fog? ^t50q112

• A) Warm, moist air transported across cold ground areas
• B) Cold, moist air mixed with warm, moist air
• C) Lengthy radiation on cloud-free nights
• D) Cold, moist air transported across warm ground areas

Correct: A)

Explanation: Advection fog results from horizontal transport of warm, moist air across a cold surface, which cools the air from below to its dew point. Option B describes mixing fog. Option C describes radiation fog. Option D (cold air over warm ground) would warm the air, decreasing humidity and preventing fog.

Q113: During the passage of a cold front, what pressure pattern is typically observed? ^t50q113

• A) A steady decrease in pressure
• B) A brief decrease followed by an increase in pressure
• C) A constant pressure pattern
• D) A steady increase in pressure

Correct: B)

Explanation: During cold front passage, pressure briefly falls (pre-frontal trough) then rises sharply as cold dense air moves in — the classic V-shaped barograph trace. Options A and D describe monotonic trends. Option C suggests no weather activity. Only option B captures the characteristic fall-then-rise signature.

Q114: Which frontal boundary separates subtropical air from polar cold air, particularly across Central Europe? ^t50q114

• A) Polar front
• B) Cold front
• C) Occlusion
• D) Warm front

Correct: A)

Explanation: The polar front is the semi-permanent boundary separating warm subtropical air from cold polar air across mid-latitudes, where extratropical cyclones form. A cold front (B) is the advancing edge of cold air within a cyclone. A warm front (D) is the advancing warm air boundary. An occlusion (C) forms when a cold front overtakes a warm front. None of these are the large-scale climatological boundary.

Q115: In Central Europe during summer, what weather conditions are typically associated with high pressure areas? ^t50q115

• A) Closely spaced isobars with calm winds, development of local wind systems
• B) Widely spaced isobars with strong prevailing westerly winds
• C) Widely spaced isobars with calm winds, development of local wind systems
• D) Closely spaced isobars with strong prevailing northerly winds

Correct: C)

Explanation: Summer highs produce widely spaced isobars (weak gradients, light synoptic winds), allowing locally driven thermal circulations (valley breezes, sea breezes, slope winds) to develop. Option A contradicts itself (close isobars do not produce calm winds). Options B and D describe strong wind patterns associated with lows.

Q116: What weather can be expected in high pressure areas during the winter season? ^t50q116

• A) Changing weather with frontal line passages
• B) Light winds and extensive areas of high fog
• C) Squall lines and thunderstorm activity
• D) Calm weather with cloud dissipation, a few high Cu

Correct: B)

Explanation: Winter highs produce subsidence inversions trapping cold moist air near the surface, creating widespread high fog (Hochnebel) and stratus with light winds. Option A (frontal weather) belongs to lows. Option C (thunderstorms) requires instability absent in winter highs. Option D describes summer high-pressure conditions.

Q117: At which temperature range is airframe icing most hazardous? ^t50q117

• A) +5° to -10° C
• B) 0° to -12° C
• C) +20° to -5° C
• D) -20° to -40° C

Correct: B)

Explanation: The most dangerous icing occurs between 0°C and -12°C where supercooled liquid water droplets are most abundant and largest. Below -20°C (D), most water has frozen to ice crystals that bounce off. Range A extends above freezing where icing cannot occur. Range C is mostly above freezing.

Q118: When large, supercooled droplets strike the leading surfaces of an aircraft, which type of ice is produced? ^t50q118

• A) Clear ice
• B) Mixed ice
• C) Hoar frost
• D) Rime ice

Correct: A)

Explanation: Clear ice (glaze) forms from large supercooled droplets that flow back along the surface before freezing, creating a smooth, dense, transparent, very heavy layer that is extremely difficult to remove. Rime ice (D) forms from small droplets freezing instantly on contact. Mixed ice (B) combines both. Hoar frost (C) forms by vapour deposition, not droplet impact.

Q119: What conditions must be present for thermal thunderstorms to develop? ^t50q119

• A) Conditionally unstable atmosphere, elevated temperature and high humidity
• B) Absolutely stable atmosphere, elevated temperature and low humidity
• C) Absolutely stable atmosphere, elevated temperature and high humidity
• D) Conditionally unstable atmosphere, low temperature and low humidity

Correct: A)

Explanation: Thermal thunderstorms need conditional instability (becomes unstable once air reaches saturation), high surface temperature (strong trigger), and high humidity (latent heat fuel). Absolutely stable atmospheres (B, C) suppress convection. Low temperature and humidity (D) deny the storm its trigger and energy source.

Q120: During which stage of a thunderstorm do updrafts dominate? ^t50q120

• A) Mature stage
• B) Upwind stage
• C) Dissipating stage
• D) Cumulus stage

Correct: D)

Explanation: The cumulus (developing) stage features exclusively updrafts building the cloud vertically — no downdrafts or precipitation have developed yet. The mature stage (A) has both updrafts and downdrafts. The dissipating stage (C) is downdraft-dominated. "Upwind stage" (B) is not a recognised meteorological term.