# Meteorology > 182 questions --- ## Atmosphere ### Q1: What is the approximate composition of dry air by volume? ^q1 - A) 78% oxygen, 21% water vapour, 1% nitrogen - B) 21% oxygen, 78% water vapour, 1% noble gases and carbon dioxide - C) 21% nitrogen, 78% oxygen, 1% noble gases and carbon dioxide - D) 78% nitrogen, 21% oxygen, 1% noble gases and carbon dioxide **Correct: D)** > **Explanation:** Dry air by volume is approximately 78% nitrogen (N2), 21% oxygen (O2), and the remaining 1% consists of argon, carbon dioxide, and other trace gases. Water vapour is variable (0–4%) and is not counted in the standard dry-air composition. Knowing air composition is fundamental to understanding atmospheric physics, density calculations, and the behaviour of aircraft engines and instruments. ### Q2: In which layer of the atmosphere do most weather phenomena occur? ^q2 - A) Stratosphere - B) Tropopause - C) Troposphere - D) Thermosphere **Correct: C)** > **Explanation:** The troposphere extends from the surface to approximately 8–16 km depending on latitude and season. It contains approximately 75–80% of the atmosphere's total mass and almost all its water vapour. Convection, cloud formation, precipitation, fronts, and wind phenomena all occur here because temperature decreases with height, driving convective instability. Above the tropopause, the stratosphere is stable and largely cloud-free. ### Q3: According to ISA conditions, what is the mass of one cubic metre of air at mean sea level? ^q3 - A) 0.01225 kg - B) 12.25 kg - C) 1.225 kg - D) 0.1225 kg **Correct: C)** > **Explanation:** According to the International Standard Atmosphere (ISA), air density at mean sea level is 1.225 kg/m³. Therefore a 1 m³ cube of air has a mass of 1.225 kg. This density value is fundamental to aviation: it affects lift, drag, engine power, and altimeter calibration. Density decreases with altitude and increases temperature/humidity changes also affect it, which is why density altitude matters for aircraft performance. ### Q4: How does the boundary between the troposphere and the stratosphere is defined? ^q4 - A) The layer above the troposphere where temperature begins to rise - B) The altitude above which temperature starts to fall - C) The transition zone between the mesosphere and the stratosphere - D) The boundary zone between the troposphere and the stratosphere **Correct: D)** > **Explanation:** The tropopause is the transition boundary between the troposphere (where temperature decreases with height) and the stratosphere (where temperature initially remains constant then increases due to ozone absorption of UV radiation). It acts as a "lid" on convection — cumulonimbus clouds that reach it spread out laterally to form the characteristic anvil shape. Jet streams are located near the tropopause. ### Q5: According to ISA, what is the mean altitude of the tropopause in metres? ^q5 - A) 36,000 m - B) 18,000 ft - C) 11,000 ft - D) 11,000 m **Correct: D)** > **Explanation:** The ISA tropopause is defined at 11,000 m (approximately 36,089 ft), where the temperature reaches -56.5°C and then remains constant with height into the lower stratosphere. In reality the tropopause height varies: it is lower over the poles (~8 km) and higher over the tropics (~16 km), and fluctuates with season and synoptic weather patterns. Cumulonimbus tops that penetrate the tropopause are especially violent. ### Q6: What is the height of the tropopause in feet according to the International Standard Atmosphere? ^q6 - A) 11,000 ft - B) 48,000 ft - C) 5,500 ft - D) 36,000 ft **Correct: D)** > **Explanation:** The ISA tropopause is located at 11,000 m, which equals approximately 36,089 ft (effectively 36,000 ft). Above this level, the standard atmosphere defines a constant temperature of -56.5°C up to 20,000 m (the isothermal stratospheric layer). This is distinct from Q5 which asks in metres — both questions test knowledge of the same value expressed in different units. ### Q7: In which unit are temperatures reported by European aviation meteorological services? ^q7 - A) Degrees Fahrenheit - B) Kelvin - C) Degrees Celsius (°C) - D) Gpdam **Correct: C)** > **Explanation:** European aviation meteorology (ICAO Annex 3, EU regulations) specifies temperatures in degrees Celsius (°C) for all operational products including METARs, TAFs, SIGMETs, and forecast charts. Kelvin is used in scientific and upper-air calculations. Fahrenheit is used in the US and a few other countries but not in European aviation. This standardisation is critical for correct interpretation of icing levels, freezing level heights, and density altitude. ### Q8: In all three states — liquid, solid, and gaseous — water can be found in which part of the Earth's environment? ^q8 - A) Only in liquid and solid form - B) In liquid, solid, and gaseous form - C) Only in liquid form - D) Only in gaseous and liquid form **Correct: B)** > **Explanation:** Water exists in all three states within the Earth's atmosphere. Gaseous water vapour is invisible and present throughout the troposphere. Liquid water forms cloud droplets, rain, and drizzle. Solid water forms ice crystals (cirrus clouds), snow, hail, and graupel. Understanding all three states is essential for icing awareness: supercooled liquid water droplets (liquid below 0°C) pose the greatest structural icing hazard to aircraft, as they freeze on contact with cold surfaces. ### Q9: Which phase transition requires an input of heat energy? ^q9 - A) Gaseous to liquid state - B) Gaseous to solid state - C) Liquid to solid state - D) Liquid to gaseous state **Correct: D)** > **Explanation:** The transition from liquid to gaseous state (evaporation) requires heat input (latent heat of evaporation). Conversely, condensation and solidification release heat. ### Q10: Which phase transition releases heat energy into the surrounding air? ^q10 - A) Solid to gaseous state - B) Liquid to gaseous state - C) Gaseous to liquid state - D) Solid to liquid state **Correct: C)** > **Explanation:** Transition from gaseous to liquid state (condensation) releases heat. Condensation releases the latent heat previously absorbed during evaporation. ### Q11: What process releases latent heat into the upper troposphere? ^q11 - A) Stabilisation of inflowing air masses - B) Cloud formation through condensation - C) Evaporation over large bodies of water - D) Widespread subsiding air motion **Correct: B)** > **Explanation:** When water vapour condenses into cloud droplets, the latent heat stored during evaporation is released into the surrounding air. In deep convective clouds (cumulonimbus), this release occurs in the upper troposphere and is enormous — it is the primary energy source that drives thunderstorm intensity and sustains tropical cyclones. The released latent heat warms the rising air parcel, making it more buoyant relative to the environment and accelerating further ascent, which is why the Saturated Adiabatic Lapse Rate (SALR) is less steep than the Dry Adiabatic Lapse Rate (DALR). ### Q12: What defines the character of an air mass? ^q12 - A) Temperatures at both the origin and current location - B) Wind speed and tropopause height - C) The environmental lapse rate at its source - D) Its region of origin and the path it has travelled **Correct: D)** > **Explanation:** An air mass is defined by the temperature and humidity properties it acquires in its source region, and how those properties are modified as it moves. Both the region of origin (polar, tropical, equatorial) and the path it travels (maritime or continental) determine whether the air is warm or cold, moist or dry. Wind speed is not a defining characteristic. Environmental lapse rate at origin is a consequence, not the defining property. Temperatures at origin and present region alone do not capture the moisture dimension. ### Q13: Which air masses primarily influence the weather in Central Europe? ^q13 - A) Equatorial and tropical warm air - B) Arctic and polar cold air - C) Tropical and arctic cold air - D) Polar cold air and tropical warm air **Correct: D)** > **Explanation:** Central Europe sits in the mid-latitude westerly belt between the polar front (cold polar air from the north) and subtropical high pressure (warm tropical air from the south). The interaction between these two contrasting air masses creates the characteristic mid-latitude cyclone (depression) weather of Central Europe: frontal systems, rapidly changing weather, and the full range of cloud types and precipitation. This dynamic contrast also drives the polar jet stream overhead. ### Q14: In the global circulation, where does polar cold air meet subtropical warm air? ^q14 - A) At the geographic poles - B) At the equator - C) At the polar front - D) At the subtropical high-pressure belt **Correct: C)** > **Explanation:** The polar front is the boundary between the polar cell (cold, dense air flowing equatorward) and the Ferrel cell (relatively warmer mid-latitude air). In the Northern Hemisphere it is located roughly between 40–60°N, but its position fluctuates as waves (Rossby waves) develop along it — these waves amplify into cyclones and anticyclones. The jet stream flows along the polar front and is a critical factor in synoptic weather patterns across Europe. ### Q15: How would you describe an air mass that reaches Central Europe from the Russian continent in winter? ^q15 - A) Continental tropical air - B) Maritime tropical air - C) Maritime polar air - D) Continental polar air **Correct: D)** > **Explanation:** An air mass originating over the cold Russian or Siberian continent during winter acquires characteristics of its source region: cold temperatures and low humidity, classifying it as Continental Polar (cP) air. Maritime air masses originate over ocean areas and carry higher moisture content. Continental Tropical air originates over warm, dry continental areas such as the Sahara, not over polar continental regions. ### Q16: Where are extensive high-pressure systems found throughout the year? ^q16 - A) In the tropics, near the equator - B) Over oceanic areas at latitudes around 30°N/S - C) In mid-latitudes along the polar front - D) In areas with large-scale lifting processes **Correct: B)** > **Explanation:** The subtropical high-pressure belt forms near 30°N and 30°S latitudes as a result of the Hadley cell circulation: warm air rising at the equator moves poleward, cools, and descends in these subtropical zones, creating semi-permanent anticyclones over oceanic areas (e.g., Azores High, Pacific High). The equatorial belt is dominated by the ITCZ with low pressure. Areas of lifting generate low pressure. Mid-latitudes are where the polar front and cyclonic activity are found. ## Temperature ### Q17: At what rate does temperature change with altitude in the troposphere according to ISA? ^q17 - A) Increases by 2°C per 1,000 ft - B) Decreases by 2°C per 100 m - C) Increases by 2°C per 100 m - D) Decreases by 2°C per 1,000 ft **Correct: D)** > **Explanation:** The ISA standard lapse rate is 1.98°C per 1000 ft (approximately 2°C/1000 ft), or 6.5°C per 1000 m. This is the Environmental Lapse Rate (ELR) used as a reference for altimeter calibration and pressure calculations. The actual ELR varies with weather conditions — steeper than ISA indicates instability and favours thermals, shallower or negative (inversion) indicates stability and suppresses convection. ### Q18: What is the ISA temperature lapse rate per 100 metres within the troposphere? ^q18 - A) 3°C / 100 m - B) 0.65°C / 100 m - C) 1°C / 100 m - D) 0.6°C / 100 m **Correct: B)** > **Explanation:** The ISA Environmental Lapse Rate (ELR) is 6.5°C per 1000 m, or 0.65°C per 100 m (approximately 2°C per 1000 ft). This is distinct from the Dry Adiabatic Lapse Rate (DALR) of 1°C/100 m and the Saturated Adiabatic Lapse Rate (SALR) of approximately 0.6°C/100 m. When the actual ELR is steeper than the DALR, the atmosphere is absolutely unstable; when it lies between the DALR and SALR, the atmosphere is conditionally unstable — the typical situation for thermal soaring. ### Q19: How does temperature vary from mean sea level to approximately 10,000 m under ISA conditions? ^q19 - A) From +20°C to -40°C - B) From -15°C to +50°C - C) From +15°C to -50°C - D) From +30°C to -40°C **Correct: C)** > **Explanation:** In the International Standard Atmosphere (ISA), the temperature at MSL is +15°C, and the temperature decreases at 6.5°C per 1000 m (2°C per 1000 ft) through the troposphere. At approximately 11,000 m (the tropopause), the temperature reaches -56.5°C, rounding to approximately -50°C at 10,000 m. Options A and D give incorrect MSL starting values. Option B reverses the sign convention, implying temperature increases with altitude. ### Q20: The recorded temperature at Samedan airport (LSZS, elevation 5,600 ft) is +5°C. Using the ISA lapse rate, what is the approximate temperature directly above the airport at 8,600 ft? ^q20 - A) +11°C - B) +5°C - C) -1°C - D) -6°C **Correct: C)** > **Explanation:** ISA lapse rate = -2°C/1000 ft. Difference: 8600 - 5600 = 3000 ft. Temperature: 5°C - (3 × 2) = -1°C. ### Q21: What characterises an inversion layer? ^q21 - A) A boundary zone separating two other atmospheric layers - B) An atmospheric layer in which temperature rises with altitude - C) An atmospheric layer in which temperature falls with altitude - D) An atmospheric layer where temperature remains constant with altitude **Correct: B)** > **Explanation:** An inversion "inverts" the normal lapse rate — instead of temperature falling with height, it rises. This creates a very stable layer that acts as a lid on convection, trapping thermals below it, concentrating pollutants, and promoting fog and low cloud formation beneath it. For glider pilots, a low-level inversion caps thermal height; a subsidence inversion in a high-pressure system limits soaring altitude and is often associated with haze. ### Q22: What defines an isothermal layer? ^q22 - A) An atmospheric layer in which temperature falls with altitude - B) An atmospheric layer in which temperature rises with altitude - C) An atmospheric layer where temperature remains constant with altitude - D) A boundary zone between two atmospheric layers **Correct: C)** > **Explanation:** An isothermal layer maintains constant temperature with increasing altitude. Like an inversion, it is more stable than the standard atmosphere and inhibits convection. The lower stratosphere exhibits an isothermal region immediately above the tropopause. Isothermal layers can also occur in the troposphere and, like inversions, act as a cap on thermal development and cloud growth. ### Q23: What process can produce an inversion layer at roughly 5,000 ft (1,500 m)? ^q23 - A) Intense solar heating on a warm summer day - B) Advection of cool air in the upper troposphere - C) Widespread subsidence within a high-pressure system - D) Ground cooling by radiation during the night **Correct: C)** > **Explanation:** Subsidence inversion forms when air in the centre of a high-pressure area sinks over a wide area. As the air descends, it warms adiabatically, but because the lower air has not warmed at the same rate, the descending layer becomes warmer than the air below it — creating an inversion, typically around 1500–3000 m. This is characteristic of anticyclonic conditions: stable weather, limited convection, and haze or smog trapped below the inversion. ### Q24: What can cause a surface-level inversion? ^q24 - A) Intensifying and gusty winds - B) Large-scale lifting of air - C) Thickening of clouds at medium levels - D) Ground cooling during the night **Correct: D)** > **Explanation:** Radiation inversion forms on calm, clear nights when the ground radiates heat into space and cools rapidly. The air in contact with the ground also cools, while air a few hundred metres above remains warmer — creating a temperature inversion near the surface. This type of inversion is common in anticyclonic conditions and often produces radiation fog or low stratus in the morning, which burns off as the sun heats the ground. ### Q25: What value does the dry adiabatic lapse rate have? ^q25 - A) 0.6°C / 100 m - B) 2°C / 1,000 ft - C) 0.65°C / 100 m - D) 1.0°C / 100 m **Correct: D)** > **Explanation:** The dry adiabatic lapse rate (DALR) is 1.0°C per 100 m (or approximately 3°F per 1000 ft). An unsaturated air parcel rising adiabatically cools at exactly this rate. Option C (0.65°C/100 m) is the standard atmosphere environmental lapse rate, option B (2°/1000 ft) is incorrect, and option A (0.6°C/100 m) approximates the saturated adiabatic lapse rate. ### Q26: How does the saturated adiabatic lapse rate compare to the dry adiabatic lapse rate? ^q26 - A) It is proportional to the dry adiabatic lapse rate - B) It is lower than the dry adiabatic lapse rate - C) It is equal to the dry adiabatic lapse rate - D) It is higher than the dry adiabatic lapse rate **Correct: B)** > **Explanation:** The saturated (moist) adiabatic lapse rate (SALR, ~0.6°C/100 m on average) is lower than the dry adiabatic lapse rate (DALR, 1.0°C/100 m) because the condensation of water vapour releases latent heat, partially offsetting the cooling of the rising air parcel. The two rates are not equal, not proportional in the way implied, and the SALR is definitely not higher than the DALR. ### Q27: What is the mean value of the saturated adiabatic lapse rate? ^q27 - A) 1.0°C / 100 m - B) 0°C / 100 m - C) 2°C / 1,000 ft - D) 0.6°C / 100 m **Correct: D)** > **Explanation:** The saturated (moist) adiabatic lapse rate (SALR) averages approximately 0.6°C per 100 m (6°C per 1000 m), because latent heat released by condensation partially offsets the dry adiabatic cooling rate. The dry adiabatic lapse rate (DALR) is 1.0°C/100 m, not the saturated rate. Option C (2°C/1000 ft) converts to approximately 0.66°C/100 m and is a rough approximation but not the standard stated value. Option B (0°C/100 m) would imply no temperature change with altitude. ### Q28: How do the volume and temperature of a descending air mass change? ^q28 - A) Both increase - B) Both decrease - C) Volume decreases, temperature increases - D) Volume increases, temperature decreases **Correct: C)** > **Explanation:** A descending air mass (subsidence) is adiabatically compressed: volume decreases and temperature increases. The air descends and warms. ### Q29: How do the volume and temperature of a rising air mass change? ^q29 - A) Both decrease - B) Volume decreases, temperature increases - C) Volume increases, temperature decreases - D) Both increase **Correct: C)** > **Explanation:** A rising air mass expands adiabatically: volume increases and temperature decreases. This is adiabatic cooling. ### Q30: What weather may be expected during conditionally unstable conditions? ^q30 - A) Clear sky with sunshine and light winds - B) Layered clouds up to high altitudes with prolonged rain or snow - C) Towering cumulus with isolated showers or thunderstorms - D) Shallow cumulus clouds with bases at mid-level **Correct: C)** > **Explanation:** In a conditionally unstable atmosphere, air is stable when unsaturated but becomes unstable once lifted to saturation (the level of free convection). This triggers vigorous convection producing towering cumulus, cumulonimbus, isolated showers and thunderstorms. Layered clouds and prolonged rain characterise stable (stratiform) conditions, clear skies indicate absolutely stable or dry conditions, and shallow mid-level cumulus does not match the vertical extent of conditional instability. ### Q31: When a cold air mass moves over warmer land and heats from below, how does it change? ^q31 - A) Atmospheric pressure increases - B) It becomes more unstable - C) Its relative humidity increases - D) Mainly stratiform clouds can be expected if clouds form **Correct: B)** > **Explanation:** When a cold air mass moves over a warmer surface and heats from below, it becomes more unstable (stronger temperature gradient). This promotes convection and cumuliform clouds. ### Q32: When a warm air mass moves over colder land and cools from below, how is it affected? ^q32 - A) Convective clouds can be expected if clouds form - B) Atmospheric pressure falls - C) It becomes more stable - D) Its relative humidity decreases **Correct: C)** > **Explanation:** A warm air mass that cools from below becomes more stable (reduced temperature gradient). This promotes stratiform clouds, not convective clouds. ## Pressure ### Q33: What is the ISA standard pressure at mean sea level? ^q33 - A) 113.25 hPa - B) 1013.25 hPa - C) 15 hPa - D) 1123 hPa **Correct: B)** > **Explanation:** The ISA (ICAO Standard Atmosphere) defines sea-level pressure as 1013.25 hPa (also expressed as 29.92 inHg in US aviation). This is the standard QNE setting — with 1013.25 hPa set on the altimeter subscale, the instrument reads Flight Level. All pressure altitudes and flight level definitions are based on this datum. Actual sea-level pressure varies with weather systems and must be corrected via QNH for accurate altitude indication. ### Q34: What is the ISA standard pressure at FL 180 (approximately 5,500 m)? ^q34 - A) 1013.25 hPa - B) 250 hPa - C) 500 hPa - D) 300 hPa **Correct: C)** > **Explanation:** In the International Standard Atmosphere, pressure at approximately 5500 m (FL180) is 500 hPa — exactly half the sea-level pressure of 1013.25 hPa. The 500 hPa level is a key reference level in synoptic meteorology and is used extensively in upper-air charts. Pressure decreases approximately logarithmically with altitude, halving roughly every 5500 m in the lower troposphere. ### Q35: Which combination of factors leads to a decrease in air density? ^q35 - A) Decreasing temperature combined with decreasing pressure - B) Increasing temperature combined with increasing pressure - C) Decreasing temperature combined with increasing pressure - D) Increasing temperature combined with decreasing pressure **Correct: D)** > **Explanation:** Air density is governed by the ideal gas law: density = pressure / (specific gas constant × temperature). Density decreases when pressure decreases (fewer molecules per unit volume) or when temperature increases (molecules move faster and spread apart). Both increasing temperature AND decreasing pressure simultaneously reduce density most effectively. This is why density altitude (the altitude equivalent of the actual air density) matters for aircraft performance on hot, high-altitude airfields. ### Q36: A barometric altimeter indicates height above what reference? ^q36 - A) Mean sea level - B) The ground directly below - C) A selected reference pressure level - D) The standard pressure of 1013.25 hPa **Correct: C)** > **Explanation:** The barometric altimeter measures atmospheric pressure and converts it to altitude based on the ISA pressure-altitude relationship. Crucially, it indicates height above whatever pressure level is set on the subscale (Kollsman window). Set QNH and it reads altitude above mean sea level; set QFE and it reads height above the reference airfield; set 1013.25 hPa (QNE) and it reads flight level. The altimeter always references a pressure level, not a physical surface. ### Q37: How can you verify altimeter accuracy while on the ground? ^q37 - A) Set QFE and check that it reads the airfield elevation - B) Set QNH and compare the reading with the known airfield elevation - C) Set QFF and compare the reading with the airfield elevation - D) Set QNE and confirm the reading shows zero **Correct: B)** > **Explanation:** QNH is the local altimeter setting that makes the instrument read the airfield's elevation above mean sea level when on the ground. Setting QNH and checking that the altimeter reads the known airfield elevation (published in AIP/chart) verifies the altimeter is functioning correctly and calibrated. QFE would show zero (height above airfield), QNE (1013.25) would show a value unrelated to actual elevation, and QFF is a meteorological value reduced to MSL for surface analysis charts. ### Q38: With the QFE setting applied, what does a barometric altimeter display? ^q38 - A) True altitude above mean sea level - B) Height above the standard pressure of 1013.25 hPa - C) Altitude above mean sea level - D) Height above the airfield reference pressure level **Correct: D)** > **Explanation:** QFE is the actual atmospheric pressure at airfield elevation. When set on the altimeter subscale, the instrument reads zero on the ground at the reference airfield and subsequently indicates height above that reference pressure level — effectively height above the airfield. This setting is commonly used in circuit flying and gliding operations so the altimeter directly reads AGL height at the home airfield. It does not account for terrain elevation differences elsewhere. ### Q39: What does a barometric altimeter indicate when QNH is set? ^q39 - A) Height above the airfield reference pressure level - B) Height above standard pressure 1013.25 hPa - C) Altitude above mean sea level - D) True altitude above MSL **Correct: C)** > **Explanation:** QNH is the altimeter setting adjusted to make the instrument read the elevation above mean sea level at the station. It is calculated by reducing the airfield QFE to sea level using the ISA temperature gradient. With QNH set, the altimeter reads the airfield elevation on the ground and true altitude above MSL in the air (assuming ISA conditions). Note that "true altitude" accounts for actual temperature deviations from ISA — QNH gives indicated altitude, which may differ from true altitude in non-ISA conditions. ### Q40: The QFE of an aerodrome at 3,500 ft elevation corresponds to which of the following? ^q40 - A) The station-level pressure reduced to sea level using the actual temperature profile - B) The station-level pressure reduced to sea level using the ISA lapse rate - C) The instantaneous pressure at sea level - D) The instantaneous atmospheric pressure at station level **Correct: D)** > **Explanation:** QFE = atmospheric pressure measured at aerodrome level (station). The altimeter reads 0 on the ground. ### Q41: Which altimeter setting allows the instrument to display the airfield elevation on the ground? ^q41 - A) QFF - B) QNE - C) QFE - D) QNH **Correct: D)** > **Explanation:** With QNH setting, the altimeter indicates altitude above mean sea level (MSL). To read the airport elevation on the ground, set QNH. QFE would show zero at the airport, QFF is a pressure reduced to sea level. ### Q42: What must be set on the altimeter to display height above the aerodrome (AAL)? ^q42 - 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:** To display AAL height (Above Aerodrome Level), set the QFE of the aerodrome. The altimeter then shows 0 on the ground and height in flight. ### Q43: An aircraft maintains FL 70 from Bern (QNH 1012 hPa) to Marseille (QNH 1027 hPa). Does the true altitude change en route? ^q43 - A) It cannot be determined - B) Yes, the aircraft climbs - C) No, it stays the same - D) Yes, the aircraft descends **Correct: D)** > **Explanation:** At FL70, with higher QNH at destination (1027 hPa vs 1012 hPa at departure), the aircraft actually descends relative to true altitude. True altitude at FL70 is lower where QNH is higher, so the aircraft is actually flying lower. ### Q44: An aircraft flies at FL 90 from Zurich (QNH 1020 hPa) to Munich (QNH 1005 hPa). Will the true altitude above sea level change? ^q44 - A) No - B) Yes, the aircraft climbs - C) It cannot be determined - D) Yes, the aircraft descends **Correct: D)** > **Explanation:** At FL90, flying from Zürich (QNH 1020) to Munich (QNH 1005): QNH decreases → true altitude decreases → aircraft descends relative to sea level while maintaining the same FL. ## Wind ### Q45: What is the fundamental force that initiates wind? ^q45 - A) Centrifugal force - B) Coriolis force - C) Pressure gradient force - D) Thermal force **Correct: C)** > **Explanation:** Wind is initiated by the pressure gradient force (PGF) — air accelerates from high pressure toward low pressure due to differences in atmospheric pressure. The Coriolis force deflects the moving air (to the right in the Northern Hemisphere) but does not cause the initial motion. Centrifugal force acts in curved flow around pressure systems. Thermal effects create pressure differences which then drive the PGF. Without a pressure gradient there would be no wind. ### Q46: How can wind speed and direction be inferred from surface weather charts? ^q46 - A) From the orientation and spacing of hypsometric lines - B) By alignment and spacing of isobars - C) From annotations in the text section of the chart - D) By the alignment of warm and cold fronts **Correct: B)** > **Explanation:** Isobars (lines of equal pressure) on surface charts indicate both wind direction and speed. Above the friction layer, wind flows parallel to isobars (geostrophic wind); close to the surface it crosses them at an angle toward lower pressure. Closely spaced isobars indicate a strong pressure gradient force and therefore strong winds; widely spaced isobars indicate light winds. Wind direction in the Northern Hemisphere is anticlockwise around lows and clockwise around highs (Buys-Ballot's Law). ### Q47: Above the friction layer, in which direction does the wind blow relative to the isobars? ^q47 - A) At a 30° angle toward low pressure - B) Parallel to the isobars - C) Perpendicular to the isobars - D) Perpendicular to the isohypses **Correct: B)** > **Explanation:** Above the friction layer (roughly 600–1000 m AGL), the Coriolis force and pressure gradient force balance each other, producing geostrophic flow parallel to the isobars. In the friction layer below, surface drag slows the wind, reduces the Coriolis deflection, and allows the wind to cross isobars at an angle toward lower pressure (typically 10–30°). Understanding this is essential for predicting wind direction at altitude versus near the surface. ### Q48: Which type of surface generates the most friction-induced wind speed reduction? ^q48 - A) Oceanic areas - B) Flat deserted land without vegetation - C) Mountainous terrain with vegetation cover - D) Flat land with extensive vegetation **Correct: C)** > **Explanation:** Surface roughness (aerodynamic roughness length) determines how much friction the surface exerts on moving air. Mountainous terrain with vegetation has the highest roughness length, causing maximum turbulent drag and wind speed reduction. Oceans have very low roughness and exert minimal friction. Flat vegetated land is intermediate. Importantly, mountains also mechanically block and deflect wind, creating additional complex flow patterns, turbulence, and wave phenomena of direct relevance to glider pilots. ### Q49: What is the term for air flowing together from different directions into one region? ^q49 - A) Divergence - B) Subsidence - C) Convergence - D) Concordance **Correct: C)** > **Explanation:** Convergence describes air flowing into a region from different directions, compressing horizontally. By mass continuity, converging surface air must go somewhere — it is forced upward, triggering cloud formation, precipitation, and potentially convective development. Convergence zones are important for glider pilots as they produce enhanced lift along their axes; sea-breeze fronts and col zones between pressure systems are classic convergence sources for soaring. ### Q50: What is the term for air flowing outward from a region in different directions? ^q50 - A) Convergence - B) Divergence - C) Concordance - D) Subsidence **Correct: B)** > **Explanation:** Divergence describes air spreading outward from a region. At the surface, divergence causes subsiding air from above to replace the outflowing air, promoting stability, clear skies, and fair weather. High-pressure anticyclones are associated with surface divergence and upper-level convergence. In the upper troposphere, divergence above a surface low enhances upward motion and intensifies the low-pressure system. ### Q51: What weather development results from surface-level convergence? ^q51 - A) Descending air with cloud dissipation - B) Ascending air with cloud dissipation - C) Ascending air with cloud formation - D) Descending air with cloud formation **Correct: C)** > **Explanation:** Surface convergence forces air upward (ascending motion) by mass continuity — air cannot accumulate indefinitely at the surface. As air rises, it cools at the dry adiabatic lapse rate until it reaches the dew point (lifting condensation level), where condensation begins and clouds form. Further ascent releases latent heat, potentially fuelling deep convection. This is the fundamental mechanism behind frontal lifting and sea-breeze convergence lift. ### Q52: When two opposing air masses collide head-on, what is this called and what motion follows? ^q52 - A) Divergence, causing the air to sink - B) Convergence, causing the air to be lifted - C) Divergence, causing the air to be lifted - D) Convergence, causing the air to sink **Correct: B)** > **Explanation:** When two opposing air flows collide head-on, the meeting zone is a convergence line. The colliding air has nowhere to go horizontally and is forced upward — producing ascending motion, cloud formation, and potentially precipitation or thunderstorms. This occurs at fronts, sea-breeze convergence zones, and col zones. Glider pilots exploit convergence lines for extended linear climbs along the lift band. ### Q53: What wind conditions should be expected in areas where isobars are widely spaced? ^q53 - A) Strong prevailing easterly winds with rapid backing - B) Strong prevailing westerly winds with rapid veering - C) Variable winds with local wind systems developing - D) Formation of local wind systems with strong westerlies **Correct: C)** > **Explanation:** Large spacing between isobars indicates a weak pressure gradient and therefore weak synoptic-scale winds. In the absence of strong pressure-gradient forcing, local thermally driven wind systems (valley-mountain winds, sea-land breezes) dominate the local circulation. Strong prevailing westerly or easterly winds require close isobar spacing. ### Q54: When isobars on a surface chart are widely spaced, what can be expected for the prevailing wind? ^q54 - A) Strong gradients producing strong wind - B) Low gradients producing weak wind - C) Strong gradients producing weak wind - D) Low gradients producing strong wind **Correct: B)** > **Explanation:** Widely spaced isobars on a surface weather chart indicate a small pressure gradient (small pressure difference over a large distance), resulting in a weak pressure gradient force and therefore light winds. The wind speed is directly proportional to the pressure gradient. ### Q55: What is meant by a mountain wind? ^q55 - A) Wind blowing uphill from the valley at night - B) Wind blowing down the mountainside during the day - C) Wind blowing down the mountainside at night - D) Wind blowing uphill from the valley during the day **Correct: C)** > **Explanation:** Mountain wind (Bergwind or katabatic wind) is the nocturnal downslope flow: at night, air in contact with the mountain slopes radiates heat, cools, becomes denser than the surrounding free air, and drains downhill under gravity. Valley wind (Talwind) is the daytime upslope flow caused by solar heating. ### Q56: You are flying at high altitude in the Northern Hemisphere with a persistent crosswind from the left. What can you conclude? ^q56 - A) There is a low-pressure area ahead and a high-pressure area behind you - B) A high-pressure area is to the left and a low-pressure area to the right of your track - C) A high-pressure area is to the right and a low-pressure area to the left of your track - D) There is a high-pressure area ahead and a low-pressure area behind you **Correct: C)** > **Explanation:** Buys-Ballot's law: standing with your back to the wind in the northern hemisphere, the low-pressure area is to your left. Wind from the left = low pressure to the left, high pressure to the right. ### Q57: A radiosonde at high altitude has a high-pressure area to its north and a low-pressure area to its south (Northern Hemisphere). In which direction will the wind carry the balloon? ^q57 - A) South - B) North - C) East - D) West **Correct: C)** > **Explanation:** In the Northern Hemisphere, with high pressure to the north and low to the south, winds circulate clockwise around the high. The balloon between both systems will be carried eastward (geostrophic wind). ### Q58: A radiosonde at high altitude has low pressure to its north and high pressure to its south (Northern Hemisphere). The balloon will drift toward which direction? ^q58 - A) South - B) East - C) North - D) West **Correct: D)** > **Explanation:** In the Northern Hemisphere, with low pressure to the north and high to the south, geostrophic winds blow westward (along isobars, with low pressure to the left in the NH). ### Q59: A wind reported as 225/15 indicates what? ^q59 - A) North-east wind at 15 km/h - B) North-east wind at 15 kt - C) South-west wind at 15 km/h - D) South-west wind at 15 kt **Correct: D)** > **Explanation:** Wind is reported in aviation as direction FROM and speed; '225' is the bearing 225° true (southwest), and '15' is the speed in knots. Wind direction is always the direction from which the wind is blowing, so 225° means the wind blows from the southwest. Speed in METARs and standard reports is in knots unless explicitly stated otherwise. ### Q60: Where are you most likely to encounter strong low-level winds and turbulence? ^q60 - A) At the centre of a depression - B) At the centre of an anticyclone - C) In a region with a slack pressure gradient in winter - D) In the transition zone between two air masses **Correct: D)** > **Explanation:** Frontal zones (transitions between air masses) produce the strongest wind gradients and turbulence. ### Q61: On a sunny summer afternoon you are on final approach to a coastal runway, with the coast to your left. What is the likely direction of the thermal sea breeze? ^q61 - A) Tailwind - B) Headwind - C) Crosswind from the left - D) Crosswind from the right **Correct: C)** > **Explanation:** In the afternoon, the sea breeze blows from sea to land. With the coast to the left, the wind comes from the left. ### Q62: Which updraft sources on terrain are most effective for generating lift? ^q62 - A) Slopes 3 and 2 - B) Slopes 4 and 2 - C) Slopes 3 and 1 - D) Slopes 4 (windward) and 1 (sun-facing) **Correct: D)** > **Explanation:** On terrain, updrafts form on the windward slopes and sunny slopes (thermals). Slopes 4 (facing the main flow) and 1 (sunny slope) have the strongest updrafts. ### Q63: In the terrain diagram, where are the strongest downdrafts found? ^q63 - A) Position 1 - B) Position 4 - C) Position 3 (leeward slope) - D) Position 2 **Correct: C)** > **Explanation:** In the diagram showing terrain with airflow, strongest downdraughts are found at position 3, generally on the leeward slope in the rotor or subsidence zone. ### Q64: How can mountain-side updrafts be intensified? ^q64 - A) By solar heating of the lee-side slope - B) By solar heating of the windward slope - C) By nighttime thermal radiation from the windward slope - D) By warming of the upper atmospheric layers **Correct: B)** > **Explanation:** Solar irradiation (insolation) heating the windward slope warms the surface air, reducing its density and creating anabatic (upslope) flow that adds to the orographic lifting already occurring; this intensifies updrafts on the windward side. The lee side experiences descending air, night-time cooling suppresses thermals, and warming of upper layers would increase stability and suppress convection. ## Clouds ### Q65: What are the two fundamental cloud types? ^q65 - A) Stratiform and ice clouds - B) Layered and lifted clouds - C) Cumuliform and stratiform clouds - D) Thunderstorm and shower clouds **Correct: C)** > **Explanation:** Clouds are fundamentally divided into two basic types: cumulus (convective, vertically developed) and stratiform (layered, horizontally extended). Cumulus clouds result from convective uplift, while stratus clouds form from large-scale lifting or cooling of air layers. ### Q66: What prefix designates clouds in the high-altitude family? ^q66 - A) Strato- - B) Alto- - C) Nimbo- - D) Cirro- **Correct: D)** > **Explanation:** The prefix 'Cirro-' denotes clouds in the high cloud family (above approximately 6,000 m / FL200), including cirrus, cirrocumulus, and cirrostratus. 'Strato-' refers to layer-type clouds at low to mid levels, 'Nimbo-' refers to rain-producing clouds (e.g., nimbostratus), and 'Alto-' denotes mid-level clouds (approximately 2,000–6,000 m). ### Q67: Which cloud type is composed exclusively of ice crystals? ^q67 - A) Stratus - B) Altocumulus - C) Cumulonimbus - D) Cirrus **Correct: D)** > **Explanation:** Cirrus clouds are exclusively composed of ice crystals. They form at very high altitude (above 6000 m) where temperatures are very low. Cumulonimbus can contain both phases (water and ice). ### Q68: Which cloud type is the visual indicator of thermal updrafts? ^q68 - A) Lenticularis - B) Stratus - C) Cumulus - D) Cirrus **Correct: C)** > **Explanation:** Cumulus clouds form as a result of thermal convection: rising air parcels cool to the dew point and condensation begins, marking the cloud base. Stratus is a layered cloud formed by broad lifting or fog, not thermals. Cirrus is high-altitude ice crystal cloud unrelated to surface thermals. Lenticularis (lenticular clouds) form in wave lift over mountains, not thermals. ### Q69: Which cloud poses the greatest hazard to aviation? ^q69 - A) Cirrostratus - B) Altocumulus - C) Cumulonimbus - D) Cirrocumulus **Correct: C)** > **Explanation:** The CB (cumulonimbus) is the most dangerous cloud: severe turbulence, lightning, hail, wind shear, icing. ### Q70: Which cloud type produces prolonged, steady rain? ^q70 - A) Cumulonimbus - B) Altocumulus - C) Cirrostratus - D) Nimbostratus **Correct: D)** > **Explanation:** Nimbostratus (Ns) is a thick, dark grey layer cloud specifically associated with prolonged, steady rain or snow falling uniformly over a wide area, typically along warm fronts. Cumulonimbus produces heavy showers and thunderstorms, not continuous prolonged rain. Altocumulus is a mid-level cloud that does not produce significant precipitation. Cirrostratus is a high-level ice cloud that does not produce precipitation reaching the ground. ### Q71: Which cloud type is most likely to produce heavy showers? ^q71 - A) Altostratus - B) Cumulonimbus - C) Nimbostratus - D) Cirrocumulus **Correct: B)** > **Explanation:** Cumulonimbus (Cb) are the clouds that produce the heaviest showers, hail, and thunderstorms. They contain enormous quantities of water and ice. ### Q72: With which cloud type is drizzle most commonly associated? ^q72 - A) Altocumulus - B) Cumulonimbus - C) Stratus - D) Cirrocumulus **Correct: C)** > **Explanation:** Drizzle is associated with stratus clouds (low stratiform clouds). Stratus produce fine, continuous drizzle. Cumulonimbus produce intense showers. ### Q73: What limits the top of cumulus cloud development? ^q73 - A) The spread - B) The absolute humidity - C) An inversion layer - D) Relative humidity **Correct: C)** > **Explanation:** An inversion layer acts as a lid that limits the vertical extent of cumulus cloud growth; thermals and updrafts lose buoyancy at the inversion, causing clouds to spread out and flatten at that level rather than growing into towering cumulus. The spread controls cloud base height, relative and absolute humidity affect cloud formation likelihood, but none of these cap the cloud top as directly as an inversion. ### Q74: Which indicator signals a high risk of thunderstorm development? ^q74 - A) Lenticular clouds (altocumulus lenticularis) - B) A bright ring around the sun (halo) - C) Stratiform clouds (stratus) - D) Tower-shaped clouds (altocumulus castellanus) **Correct: D)** > **Explanation:** Altocumulus castellanus (tower-shaped clouds) indicate significant atmospheric instability at medium altitude and are precursors of thunderstorms. Lenticular clouds indicate mountain waves. ### Q75: Which typical cloud type can be observed in widespread high-pressure areas during summer? ^q75 - A) Scattered cumulus clouds - B) Overcast low stratus - C) Squall lines and thunderstorms - D) Overcast nimbostratus **Correct: A)** > **Explanation:** In summer anticyclones, surface heating generates thermal convection that produces scattered fair-weather Cumulus clouds (Cu humilis or Cu mediocris) during the day, dissipating in the evening. Overcast low stratus is associated with stable, moist air at low levels. Nimbostratus is associated with frontal systems. Squall lines and thunderstorms require convective instability not typical of settled high-pressure conditions. ### Q76: Based on cloud type of origin, precipitation is classified as which of the following? ^q76 - A) Light and heavy precipitation - B) Rain and showers of rain - C) Prolonged rain and continuous rain - D) Showers of snow and rain **Correct: B)** > **Explanation:** Meteorologically, precipitation is classified by its cloud type of origin: rain (continuous precipitation from stratiform clouds such as Nimbostratus) and showers of rain (convective precipitation from cumuliform clouds such as Cumulonimbus or Cumulus congestus). The other options describe precipitation by intensity or type, which are separate classification systems not based on cloud type. ### Q77: What is required for medium to large precipitation particles to form? ^q77 - A) Strong wind - B) A high cloud base - C) An inversion layer - D) Strong updrafts **Correct: D)** > **Explanation:** Formation of medium to large precipitation particles requires strong updrafts to keep droplets or ice particles suspended long enough to grow by collision-coalescence or the Bergeron process. Weak updrafts allow small particles to fall before they grow significantly. An inversion layer suppresses growth, a high cloud base reduces available cloud depth, and strong wind alone does not sustain particles in the cloud. ### Q78: What cloud sequence is typically observed during the approach of a warm front? ^q78 - A) Squall line with showers of rain and thunderstorms, gusty winds, then cumulus with isolated showers - B) Calm winds, cloud dissipation and warming in summer; extended high-fog layers in winter - C) Cirrus, thickening altostratus and altocumulus, lowering cloud base with rain, nimbostratus - D) Coastal daytime sea breeze with cumulus forming, clouds dissipating in the evening **Correct: C)** > **Explanation:** As a warm front approaches, the first sign is high-level Cirrus, which gradually thickens into Cirrostratus, then Altostratus and Altocumulus at mid-levels, finally transitioning to Nimbostratus with prolonged rain and a lowering cloud base. Option A describes the passage of a cold front. Option B describes a high-pressure or thermal anticyclone scenario. Option D describes a coastal sea-breeze pattern. ## Fog ### Q79: Which conditions favour the formation of advection fog? ^q79 - A) Cold, humid air moving over a warm ocean - B) Warm, humid air cooling during a cloudy night - C) Moisture evaporating from warm ground into cold air - D) Warm, humid air moving over a cold surface **Correct: D)** > **Explanation:** Advection fog forms when warm, humid air moves horizontally over a cold surface (land or sea), cooling the air to its dew point. Option B describes radiation fog (not advection), option A is incorrect because cold air over a warm ocean would create evaporation/steam fog, and option C describes steam or evaporation fog. ### Q80: What process leads to the formation of advection fog? ^q80 - A) Prolonged radiative cooling on clear nights - B) Warm, moist air transported across cold ground - C) Cold, moist air mixing with warm, moist air - D) Cold, moist air being moved across warm ground **Correct: B)** > **Explanation:** Advection fog results from the horizontal movement of warm, moist air over a cold surface, which cools the air from below until it reaches its dew point. Option D reverses the temperature relationship, option C describes mixing fog, and option A describes radiation fog caused by nocturnal cooling. ### Q81: What is the phenomenon called when moist air moves horizontally over a colder surface and forms fog? ^q81 - A) Radiation fog - B) Sea spray - C) Advection fog - D) Orographic fog **Correct: C)** > **Explanation:** Advection fog forms by horizontal movement of a moist air mass over a colder surface. The air cools to its dew point. ### Q82: What leads to the formation of orographic fog (hill fog)? ^q82 - A) Evaporation from warm ground into very cold air - B) Cold, moist air mixing with warm, moist air - C) Prolonged radiative cooling on clear nights - D) Warm, moist air being forced to rise over elevated terrain **Correct: D)** > **Explanation:** Orographic (hill) fog forms when warm, moist air is forced to rise over elevated terrain, cools adiabatically to the dew point, and saturates; the resulting cloud envelops the hill or mountain as fog. Prolonged radiation cooling describes radiation fog, evaporation into cold air describes steam fog, and mixing of air masses describes mixing fog. ### Q83: When humid, nearly saturated air is pushed upslope by the prevailing wind, what type of fog forms? ^q83 - A) Steaming fog - B) Radiation fog - C) Advection fog - D) Orographic fog **Correct: D)** > **Explanation:** Orographic fog forms when wind-driven humid air is mechanically lifted along a slope, cooling adiabatically until it reaches the dew point. Radiation fog requires calm nights with radiative ground cooling, advection fog forms when warm moist air moves over a cold surface, and steaming fog (Arctic sea smoke) occurs when cold air passes over warm water — none of these involve slope-forced lifting. ### Q84: Which situation most favours the formation of radiation fog? ^q84 - A) 15 kt wind / Clear sky / 16°C / Dew point 15°C - B) 2 kt wind / Clear sky / -3°C / Dew point -20°C - C) 15 kt wind / Overcast / 13°C / Dew point 12°C - D) 2 kt wind / Scattered cloud / 7°C / Dew point 6°C **Correct: D)** > **Explanation:** Radiation fog: light wind (2 kt), small temperature/dew point spread (1°C), some cloud acceptable. Option B has too large a temp/dew point spread. ### Q85: At what time of day or night is radiation fog most likely to form? ^q85 - A) In the afternoon - B) Shortly after sunset - C) At sunrise - D) Shortly before midnight **Correct: D)** > **Explanation:** Radiation fog forms shortly before midnight or in the late night, when the ground has cooled sufficiently by radiation to cool the air to the dew point. It is most dense at dawn. ### Q86: What condition can prevent the formation of radiation fog? ^q86 - A) Clear night without clouds - B) Calm wind - C) Overcast cloud cover - D) Low spread (small temperature–dew point difference) **Correct: C)** > **Explanation:** Overcast cloud cover prevents the ground from radiating heat to space at night (the greenhouse/blanket effect), so the surface does not cool sufficiently to reach the dew point, and radiation fog cannot form. Calm wind, clear nights, and a low temperature–dew point spread all favour fog formation, not prevent it. ### Q87: Suspended fine water droplets reduce visibility at an aerodrome to 1.5 km up to 1,000 ft AGL. What is the meteorological phenomenon? ^q87 - A) Haze (HZ) - B) Shallow fog (MIFG) - C) Widespread dust (DU) - D) Mist (BR) **Correct: D)** > **Explanation:** Visibility 1–5 km with water droplets = mist (BR). Fog = visibility < 1 km. ### Q88: Which factors suggest a tendency toward fog formation? ^q88 - A) Low spread combined with decreasing temperature - B) Low pressure combined with increasing temperature - C) Low spread combined with increasing temperature - D) Strong winds combined with decreasing temperature **Correct: A)** > **Explanation:** A low spread (temperature close to dew point) means the air is near saturation, and decreasing temperature (e.g., nocturnal cooling or advection of cold air) will bring the temperature down to the dew point, causing condensation and fog. Strong winds promote mixing that prevents fog. Low pressure is associated with ascending air. Increasing temperature widens the spread and dissipates fog. ### Q89: Which type of visibility reduction is least sensitive to temperature changes? ^q89 - A) Mist (BR) - B) Radiation fog (FG) - C) Haze (HZ) - D) Patches of fog (BCFG) **Correct: C)** > **Explanation:** Haze (HZ) is caused by dry particles (dust, smoke, pollution) suspended in the atmosphere and is not dependent on temperature or moisture; it persists regardless of temperature changes. Radiation fog, mist, and patches of fog are all moisture-dependent phenomena that form, thicken, or dissipate in direct response to temperature changes relative to the dew point. ## Humidity and Moisture ### Q90: How do the dew point and relative humidity change when temperature decreases? ^q90 - A) Dew point increases, relative humidity decreases - B) Dew point remains constant, relative humidity increases - C) Dew point decreases, relative humidity increases - D) Dew point remains constant, relative humidity decreases **Correct: B)** > **Explanation:** The dew point is the temperature to which air must be cooled (at constant pressure and moisture content) for saturation to occur. It is a measure of the absolute moisture content and remains constant as temperature changes (assuming no moisture is added or removed). However, relative humidity — the ratio of actual vapour pressure to saturation vapour pressure — increases as temperature falls, because the saturation vapour pressure decreases with temperature. When temperature equals the dew point, relative humidity reaches 100% and condensation begins. ### Q91: How do spread and relative humidity change when temperature increases? ^q91 - A) Spread increases, relative humidity increases - B) Spread remains constant, relative humidity increases - C) Spread remains constant, relative humidity decreases - D) Spread increases, relative humidity decreases **Correct: D)** > **Explanation:** Spread is the temperature-dew point difference (T - Td). As temperature increases while dew point remains constant, the spread widens. Simultaneously, because warmer air can hold more water vapour, the relative humidity decreases — the air is now further from saturation. A large spread indicates dry air and a high lifting condensation level. A small spread (near zero) indicates saturated or near-saturated conditions, with fog or low cloud likely. ### Q92: What does the term "spread" mean? ^q92 - A) The maximum amount of water vapour air can hold - B) The difference between the actual temperature and the dew point - C) The ratio of actual to maximum possible humidity - D) The difference between the dew point and the condensation point **Correct: B)** > **Explanation:** Spread (also called dew point depression) is simply the difference between the air temperature and the dew point temperature: Spread = T - Td. It is used to estimate cloud base height: in temperate latitudes, cloud base height in metres above the surface is approximately spread × 125 (or in feet, spread × 400). A spread of 0 means the air is saturated (fog or cloud at the surface). Spread is a quick indicator of moisture availability for soaring pilots. ### Q93: When temperature decreases while other factors remain constant, what happens to spread and relative humidity? ^q93 - A) Spread increases, relative humidity decreases - B) Spread increases, relative humidity increases - C) Spread decreases, relative humidity decreases - D) Spread decreases, relative humidity increases **Correct: D)** > **Explanation:** As temperature decreases (with dew point unchanged), the gap between temperature and dew point narrows — spread decreases. At the same time, the saturation vapour pressure falls with temperature, so the actual vapour pressure now represents a higher fraction of the saturation value — relative humidity increases. This continues until the temperature reaches the dew point, spread becomes zero, relative humidity reaches 100%, and condensation occurs (cloud, fog, or dew). ### Q94: At 10°C an air mass has 45% relative humidity. If the temperature rises to 20°C, how does the humidity change? ^q94 - A) It increases by 50% - B) It remains constant - C) It decreases - D) It increases by 45% **Correct: C)** > **Explanation:** If temperature rises (without adding moisture), the air can hold more water vapour → relative humidity decreases. ### Q95: At +2°C an air mass has a relative humidity of 35%. How will this change if the temperature drops to -5°C? ^q95 - A) Relative humidity increases - B) Relative humidity decreases by 7% - C) Relative humidity remains the same - D) Relative humidity decreases by 3% **Correct: A)** > **Explanation:** Relative humidity increases when temperature drops (water vapor content remains the same but maximum capacity decreases). Cooling from +2°C to -5°C brings air closer to saturation. ### Q96: At 18°C an air mass has a relative humidity of 29%. If the temperature rises to 28°C, how does the humidity change? ^q96 - A) It increases by 10% - B) It increases by 29% - C) It decreases - D) It remains the same **Correct: C)** > **Explanation:** If temperature rises from 18°C to 28°C, the air's maximum water vapor capacity increases, but the vapor quantity remains the same → relative humidity decreases. ## Fronts ### Q97: What frontal boundary separates subtropical air from polar cold air across Central Europe? ^q97 - A) Warm front - B) Occlusion - C) Cold front - D) Polar front **Correct: D)** > **Explanation:** The polar front is the semi-permanent boundary separating cold polar air masses from warmer subtropical air, and it is the birthplace of mid-latitude cyclones affecting Central Europe. A warm front is the leading edge of an advancing warm air mass, a cold front is the leading edge of an advancing cold air mass, and an occlusion is a later stage where these fronts merge — none of these are the primary climatological boundary itself. ### Q98: What pressure pattern is observed during the passage of a cold front? ^q98 - A) Pressure rises continuously - B) Pressure remains constant - C) Pressure falls briefly, then rises - D) Pressure falls continuously **Correct: C)** > **Explanation:** As a cold front approaches, pressure falls ahead of it due to the preceding low-pressure trough; once the front passes, colder, denser air causes pressure to rise again. Continuously increasing pressure would indicate persistent high pressure building, continuously decreasing describes a deepening low without frontal passage, and constant pressure is inconsistent with dynamic frontal systems. ### Q99: What is an air-mass boundary with no horizontal displacement called? ^q99 - A) Cold front - B) Warm front - C) Occluded front - D) Stationary front **Correct: D)** > **Explanation:** A stationary front is a boundary between two contrasting air masses with no significant horizontal movement in either direction. A cold front moves toward the warm air, a warm front moves toward the cold air, and an occluded front is the result of a cold front overtaking a warm front. ### Q100: On a synoptic chart, which symbol (labelled 1) represents a cold front? ^q100 - A) Warm front - B) Cold front - C) Front aloft - D) Occlusion **Correct: B)** > **Explanation:** On a surface weather chart, a cold front is depicted by a line with solid triangular spikes (barbs) pointing in the direction of movement. A warm front uses semicircles. An occlusion uses alternating triangles and semicircles. A front aloft is depicted differently. ### Q101: The symbol labelled (2) on the weather chart represents which front type? ^q101 - A) Cold front - B) Occlusion - C) Warm front - D) Front aloft **Correct: C)** > **Explanation:** On synoptic weather charts, a warm front is depicted by a line with semicircles pointing in the direction of movement (into the cooler air). Cold fronts use triangular barbs, occlusions combine both symbols, and a front aloft is marked differently. ### Q102: The symbol labelled (3) on the synoptic chart represents which front? ^q102 - A) Warm front - B) Cold front - C) Occlusion - D) Front aloft **Correct: C)** > **Explanation:** On standard synoptic weather charts, an occlusion is depicted by a line combining both cold-front triangles and warm-front semicircles on the same side, representing a front where the cold front has caught up with the warm front. Cold fronts show only triangles, warm fronts only semicircles, and fronts aloft are marked differently. ### Q103: What is the typical phenomenon during a summer passage of an unstable cold front? ^q103 - A) Rapid temperature rise behind the front - B) Convective clouds - C) Rapid pressure drop behind the front - D) Stratiform clouds **Correct: B)** > **Explanation:** An unstable cold front in summer generates convective clouds (CB, TCu) with showers and thunderstorms. ### Q104: What weather and clouds typify the passage of a cold front? ^q104 - A) Cirrus thickening to nimbostratus with lowering cloud base and rain - B) Calm winds, dissipating clouds, warming in summer; extended high fog in winter - C) Coastal sea breeze with cumulus forming during the day, dissipating at night - D) Strongly developed cumulonimbus with showers and thunderstorms, gusty winds followed by isolated showers **Correct: D)** > **Explanation:** Cold fronts are characterised by active convective weather: rapidly developing Cumulonimbus clouds producing heavy showers and thunderstorms, accompanied by squall-line activity, strong gusty winds, and followed by scattered cumulus with isolated showers in the cold air behind the front. Option A describes a warm front. Options B and C describe anticyclonic or sea-breeze patterns. ### Q105: What is characteristic of an active cold front with unstable properties in its wake? ^q105 - A) Stratiform cloud cover with generally poor visibility - B) Rapid temperature rise with generally poor visibility - C) Rapid pressure drop with good visibility outside showers - D) Gusty winds with good visibility outside showers **Correct: D)** > **Explanation:** Behind an active cold front with unstable characteristics, expect gusty winds and good visibility between showers. The cold, unstable air following the front produces scattered showers but good visibility between them. ### Q106: What is characteristic when unstable warm air meets an advancing cold front in summer in central Europe? ^q106 - A) Rapid pressure drop after the front passes - B) Stratiform clouds - C) Thunderstorm clouds - D) Rapid temperature rise after the front passes **Correct: C)** > **Explanation:** In European summer, when unstable warm air meets a cold front, thunderstorm clouds (Cb) develop. This is the most characteristic sign of an active summer cold front. ### Q107: When a stable, warm, humid air mass slides over a cold air mass, what conditions are most likely? ^q107 - A) Formation of a few small cumuliform clouds, rare precipitation, light turbulence, excellent visibility - B) At altitude: rapid drying of the air with good visibility. In the lowlands: dense mist or fog - C) Formation of extensive stratiform clouds with gradually lowering cloud base and sustained rainfall - D) Convective clouds, heavy showers, tendency for thunderstorms, severe turbulence **Correct: C)** > **Explanation:** Warm and humid air sliding over cold air (warm front) = stratiform clouds, continuous rain, lowering cloud base. ### Q108: What visual flight conditions prevail within the warm sector of a polar front low during summer? ^q108 - A) Moderate visibility with heavy showers and thunderstorms - B) Visibility below 1,000 m with cloud-covered ground - C) Good visibility with a few isolated high clouds - D) Moderate to good visibility with scattered clouds **Correct: D)** > **Explanation:** Within the warm sector of a polar front low, the air is relatively warm and moist but conditions typically offer moderate to good visibility with scattered or broken cloud layers. Visibility less than 1 km with ground-covering cloud is more typical of fog or orographic stratus in the cold sector. Heavy showers are post-cold-front weather. Good visibility with only high cirrus is more characteristic of the pre-warm-front region. ### Q109: What visual conditions can be expected after a cold front has passed? ^q109 - A) Medium visibility with lowering cloud base and the onset of prolonged precipitation - B) Good visibility with cumulus clouds and showers of rain or snow - C) Scattered cloud layers with visibility exceeding 5 km and shallow cumulus - D) Poor visibility with overcast stratus, snow **Correct: B)** > **Explanation:** After a cold front passes, cold, unstable polar air replaces the warm sector air; this instability produces good visibility (clean polar air) with convective cumulus clouds and showery precipitation. Poor visibility with stratus and snow is more typical of a warm occlusion. Options C and D describe intermediate or pre-frontal conditions. ### Q110: In which direction does a polar front low typically move? ^q110 - A) Parallel to the warm front line toward the south - B) To the northeast in winter, to the southeast in summer - C) Parallel to the warm-sector isobars - D) To the northwest in winter, to the southwest in summer **Correct: C)** > **Explanation:** A polar front low moves in the direction of and roughly parallel to the isobars in its warm sector, because the warm sector winds steer the system. Seasonal directional rules are oversimplified and not reliable. Movement parallel to the warm front line southward is inconsistent with the observed eastward to northeastward tracks of North Atlantic lows. ### Q111: What pressure pattern is observed during the passage of a polar front low? ^q111 - A) Falling pressure ahead of the warm front, constant in the warm sector, rising behind the cold front - B) Falling pressure ahead of the warm front, constant in the warm sector, falling behind the cold front - C) Rising pressure ahead of the warm front, rising in the warm sector, falling behind the cold front - D) Rising pressure ahead of the warm front, constant in the warm sector, rising behind the cold front **Correct: A)** > **Explanation:** Ahead of an approaching warm front, pressure falls as the low approaches. Within the warm sector, pressure remains relatively steady. After the cold front passes, cold dense air causes pressure to rise sharply. ### Q112: What wind direction changes occur during the passage of a polar front low in Central Europe? ^q112 - A) Backing at the warm front, backing at the cold front - B) Veering at the warm front, veering at the cold front - C) Backing at the warm front, veering at the cold front - D) Veering at the warm front, backing at the cold front **Correct: B)** > **Explanation:** In the Northern Hemisphere, as a polar front low passes, the wind veers (shifts clockwise, e.g., from south to southwest) with the warm front passage and veers again (e.g., from southwest to northwest) with the cold front passage. Backing (anti-clockwise shift) would indicate the low passing to the south of the observer, which is less common in Central Europe. ### Q113: Which air mass is likely to produce showers in Central Europe regardless of season? ^q113 - A) Continental tropical air - B) Maritime tropical air - C) Maritime polar air - D) Continental polar air **Correct: C)** > **Explanation:** Maritime polar air is unstable (cold below, moist) → convection → showers in all seasons. ### Q114: Under which conditions is "back-side weather" (Rückseitenwetter) expected? ^q114 - A) After the passage of a warm front - B) During Foehn on the lee side - C) Before the passage of an occlusion - D) After the passage of a cold front **Correct: D)** > **Explanation:** Back-side weather (Rückseitenwetter) describes the weather in the cold air mass following the passage of a cold front: cold, unstable polar or arctic air with scattered showers, good visibility, and gusty winds — often excellent soaring conditions for gliders in the convective back-side air. ### Q115: What will happen to pressure at a point located ahead of an approaching depression and warm front? ^q115 - A) Pressure will rise - B) No notable change - C) Rapid and regular pressure oscillations - D) Pressure will fall **Correct: D)** > **Explanation:** Point C is located ahead of the approaching depression/front → pressure will fall. ### Q116: On a synoptic chart, an approaching anticyclone will cause pressure at a nearby point to do what? ^q116 - A) No change - B) Rapid and regular variations - C) Rise - D) Fall **Correct: C)** > **Explanation:** The approach of an anticyclone causes a pressure rise at the nearby point in the next hour. ### Q117: What pressure pattern results from cold-air inflow in the upper troposphere? ^q117 - A) Alternating pressure - B) Formation of an upper-level high - C) Formation of a large surface low - D) Formation of an upper-level low **Correct: D)** > **Explanation:** When cold air advects into the upper troposphere, it contracts the air column (cold air is denser), reducing the thickness between pressure levels; this lowers pressure aloft and produces an upper-level trough or low. Upper lows associated with cold-air pools are a key trigger for convective instability. ### Q118: Cold-air intrusion in the upper troposphere may result in what weather? ^q118 - A) Frontal weather - B) Calm weather with cloud dissipation - C) Stabilisation and calm weather - D) Showers and thunderstorms **Correct: D)** > **Explanation:** Cold air intruding into the upper troposphere destabilises the atmosphere by creating a steep lapse rate. This conditional instability, when combined with moisture, generates convective activity including showers and thunderstorms. It does not produce frontal weather, nor does it cause calm weather or cloud dissipation. ### Q119: How does inflowing cold air affect the vertical spacing and height of pressure layers? ^q119 - A) Increasing spacing with higher pressure surfaces - B) Decreasing spacing with higher pressure surfaces - C) Decreasing spacing with lower pressure surfaces - D) Increasing spacing with lower pressure surfaces **Correct: C)** > **Explanation:** Cold air is denser, so a column of cold air has shorter vertical distances between pressure surfaces and pressure surfaces lie at lower heights — indicating low pressure aloft. This is why upper-level cold pools are associated with upper troughs. Warm air has the opposite effect: greater thickness and higher pressure surfaces. ### Q120: What weather phenomena should be expected around an upper-level trough? ^q120 - A) Formation of high stratus and ground-covering cloud bases - B) Calm wind with shallow cumulus clouds - C) Development of showers and thunderstorms - D) Calm weather with lifted fog layers **Correct: C)** > **Explanation:** An upper-level trough is a region of cold air aloft with positive vorticity advection, which promotes divergence aloft and convergence at the surface, triggering strong convective uplift. This instability favours the development of showers and thunderstorms. The other options describe stable, anticyclonic conditions. ## Thunderstorms ### Q121: What conditions are most favourable for thunderstorm development? ^q121 - A) Warm, dry air beneath a strong inversion layer - B) Warm, humid air with a conditionally unstable lapse rate - C) Calm winds with cold air and overcast stratus or altostratus - D) Clear night over land with cold air and fog patches **Correct: B)** > **Explanation:** Thunderstorms require three key ingredients: moisture (warm humid air provides latent energy), lift (to trigger convection), and instability (a conditionally unstable environmental lapse rate means rising saturated air becomes warmer than its surroundings and accelerates upward). The other options describe stable, overcast, or dry conditions unfavourable for convection. ### Q122: In which situation will the tendency for thunderstorms be greatest? ^q122 - A) Slack pressure gradient, significant cooling of the lower layers, high humidity - B) High pressure, significant warming of the lower layers, low humidity - C) Slack pressure gradient, significant warming of the lower layers, high humidity - D) Slack pressure gradient, significant warming of the upper layers, high humidity **Correct: C)** > **Explanation:** Thunderstorms = slack pressure gradient (low pressure gradient) + strong surface heating (instability) + high humidity. ### Q123: What mandatory conditions are required to form thermal thunderstorms? ^q123 - A) Absolutely stable atmosphere with high temperature and high humidity - B) Conditionally unstable atmosphere with low temperature and low humidity - C) Conditionally unstable atmosphere with high temperature and high humidity - D) Absolutely stable atmosphere with high temperature and low humidity **Correct: C)** > **Explanation:** Thermal (air mass) thunderstorms require a conditionally unstable atmosphere — one that becomes unstable once convection is triggered — combined with high temperatures to drive strong surface heating and high humidity to provide the latent heat energy needed to sustain deep convection. An absolutely stable atmosphere suppresses convection regardless of temperature or humidity. ### Q124: During which stage of a thunderstorm are only updrafts present? ^q124 - A) Mature stage - B) Upwind stage - C) Cumulus stage - D) Dissipating stage **Correct: C)** > **Explanation:** The cumulus stage is characterised entirely by updrafts that build the storm upward; no downdrafts have yet developed. The mature stage features both strong updrafts and downdrafts. The dissipating stage is dominated by downdrafts. There is no meteorological stage called the 'upwind stage'. ### Q125: In which stage of a thunderstorm do both strong updrafts and strong downdrafts coexist? ^q125 - A) Dissipating stage - B) Mature stage - C) Initial stage - D) Thunderstorm stage **Correct: B)** > **Explanation:** In the mature stage of a thunderstorm, both strong updrafts (sustaining the storm) and strong downdrafts (driven by precipitation drag and evaporative cooling) coexist simultaneously within the Cumulonimbus cell. The initial (cumulus) stage has only updrafts. The dissipating stage is dominated by downdrafts only. 'Thunderstorm stage' is not a recognised meteorological term. ### Q126: What phenomenon is produced by cold-air downdrafts and precipitation from a fully developed thunderstorm? ^q126 - A) Freezing rain - B) The anvil-head top of the cumulonimbus - C) Electrical discharge - D) Gust front **Correct: D)** > **Explanation:** During a fully developed (mature stage) thunderstorm, cold precipitation-laden air descends rapidly beneath the Cumulonimbus and spreads outward upon reaching the surface, creating a gust front — a sharp boundary of cold gusty air that can precede the visible storm by several kilometres. Electrical discharge is a separate hazard. The anvil top is a structural feature caused by upper-level winds. Freezing rain results from a temperature inversion aloft. ### Q127: Where should heavy downdrafts and strong wind shear close to the ground be expected? ^q127 - A) During approach to a coastal airfield with a strong sea breeze - B) During cold, clear nights when radiation fog forms - C) Near the rainfall areas of heavy showers or thunderstorms - D) On warm summer days with high, flattened cumulus clouds **Correct: C)** > **Explanation:** Precipitation falling from heavy showers or thunderstorms creates strong downdrafts (microbursts or downbursts) that spread outward near the ground, generating intense low-level wind shear. A sea-breeze front can cause some shear but not heavy downdrafts. Radiation fog nights are associated with calm conditions. Flat cumulus indicate weak convection. ### Q128: What type of thunderstorm occurs when air is forced to rise by topography into unstable, moist layers? ^q128 - A) Warm front thunderstorms - B) Thermal thunderstorms - C) Cold front thunderstorms - D) Orographic thunderstorms **Correct: D)** > **Explanation:** Orographic thunderstorms occur when air is forced to rise by topography (mountains) and reaches unstable, moist layers. Distinct from thermal or frontal thunderstorms. ### Q129: While planning a 500 km triangle flight, a squall line lies 100 km to the west of the departure airfield, extending north to south and moving east. What decision is advisable? ^q129 - A) Navigate below the cloud base of the thunderstorms - B) Change plans and fly the triangle heading east - C) Look for gaps between the thunderstorms during flight - D) Postpone the flight to another day **Correct: D)** > **Explanation:** A squall line is an organized line of severe thunderstorms that is notoriously fast-moving, unpredictable, and extremely dangerous. Moving at typical speeds of 30–60 km/h, a squall line 100 km away could reach the airfield within 2–3 hours. Flying below Cb cloud bases or attempting to navigate between cells exposes the glider to extreme turbulence, windshear, hail, and downdrafts. The only safe option is to not fly until the hazard has completely passed. ### Q130: What situation can cause severe wind shear? ^q130 - A) Flying ahead of a warm front with visible cirrus clouds - B) A shower visible close to the airfield - C) Cross-country flying below cumulus clouds at about 4 oktas coverage - D) Final approach 30 minutes after a heavy shower has passed **Correct: B)** > **Explanation:** A shower visible close to the airfield is producing active downdrafts and outflow boundaries right now; these create severe, rapidly shifting low-level wind shear that is an immediate threat during approach or departure. Flying ahead of a warm front involves gradually deteriorating conditions but not severe shear. Cross-country flying below moderate Cu is normal gliding. Thirty minutes after a shower has passed, conditions have typically normalised. ### Q131: What is the most imminent danger when an aircraft is struck by lightning? ^q131 - A) Disturbed radio communication with static noise signals - B) Explosion of electrical equipment in the cockpit - C) Surface overheat and damage to exposed aircraft parts - D) Rapid cabin depressurisation and smoke **Correct: C)** > **Explanation:** The most immediate physical danger when an aircraft is struck by lightning is surface overheat and structural damage to exposed parts — lightning can burn through fairings, damage antennas, pit metal surfaces, and in extreme cases damage control surfaces. Avionics may be affected, but explosion of cockpit equipment is not a primary risk. Depressurisation applies only to pressurised aircraft. Radio static is possible but not the most imminent danger. ## Icing ### Q132: In which temperature range is airframe icing most dangerous? ^q132 - A) +5°C to -10°C - B) 0°C to -12°C - C) +20°C to -5°C - D) -20°C to -40°C **Correct: B)** > **Explanation:** The most dangerous icing temperatures are 0°C to −12°C because liquid water droplets remain supercooled and in large quantities at these temperatures, maximising ice accretion on airframes. Above +5°C ice cannot form, and below −20°C to −40°C most water has already frozen into ice crystals which do not adhere as readily to surfaces. ### Q133: What type of ice forms when large supercooled water droplets strike an aircraft's leading edges? ^q133 - A) Mixed ice - B) Hoar frost - C) Rime ice - D) Clear ice **Correct: D)** > **Explanation:** Clear ice (glaze ice) forms when large supercooled water droplets strike an aircraft, flow back before freezing, and solidify into a dense, smooth, heavy layer that is very difficult to remove. Hoar frost forms from deposition of water vapour on cold surfaces. Rime ice forms from small supercooled droplets. Mixed ice combines both rime and clear ice characteristics. ### Q134: What type of ice results from very small supercooled droplets and ice crystals striking an airframe? ^q134 - A) Clear ice - B) Hoar frost - C) Rime ice - D) Mixed ice **Correct: C)** > **Explanation:** Rime ice forms when small supercooled water droplets and ice crystals strike the airframe and freeze instantly on contact, creating a white, opaque, brittle deposit typically on leading edges. Clear ice forms from large supercooled droplets that spread before freezing. Mixed ice is a combination. Hoar frost forms from water vapour depositing directly as ice crystals on cold surfaces, not from droplet impact. ### Q135: Which conditions are most favourable for significant ice accretion on an aircraft? ^q135 - A) Temperatures between 0°C and -12°C with supercooled water droplets present - B) Temperatures between -20°C and -40°C with ice crystals in cirrus clouds - C) Temperatures below 0°C with strong wind and clear skies - D) Temperatures between +10°C and -30°C with hail present **Correct: A)** > **Explanation:** The most severe icing occurs between 0°C and -12°C where supercooled liquid water droplets are most abundant and drop size is largest, producing clear or mixed icing on airframe surfaces. Below -20°C, cloud water is mostly ice crystal form and causes much less accretion. Above 0°C droplets do not freeze on contact. Icing in clear air does not occur as there are no supercooled droplets. ### Q136: Where is freezing rain most likely to be encountered? ^q136 - A) In summer during the passage of a warm front - B) In summer during the passage of a cold front - C) In winter during the passage of a cold front - D) In winter during the passage of a warm front **Correct: D)** > **Explanation:** Freezing rain is most common in winter during warm front passage, when rain from a warm layer falls through a sub-zero layer before reaching the ground. ### Q137: Which temperature profile above an aerodrome presents the greatest risk of freezing rain? ^q137 - A) Profile D - B) Profile C - C) Profile A (warm layer aloft, cold layer at the surface) - D) Profile B **Correct: C)** > **Explanation:** Freezing rain forms when rain from a warm layer falls through a sub-zero layer. Profile A shows the typical temperature inversion enabling this: cold layer at the surface, warm layer above. ## Turbulence ### Q138: Where should light turbulence always be expected? ^q138 - A) Below stratiform clouds at medium levels - B) When entering inversions - C) Above cumulus clouds due to thermal convection - D) Below cumulus clouds due to thermal convection **Correct: D)** > **Explanation:** Cumulus clouds are the visible tops of thermal columns. The sub-cloud layer beneath them contains active thermals (updraughts) and compensating downdraughts between them, creating light to moderate turbulence from convective mixing. This is the normal turbulent environment of thermal soaring. ### Q139: Where should moderate to severe turbulence be expected? ^q139 - A) Below thick cloud layers on the windward side of a mountain range - B) Over unbroken cloud layers - C) On the lee side of a mountain range when rotor clouds are present - D) Where extended low stratus (high fog) is present **Correct: C)** > **Explanation:** Rotor clouds (roll clouds) on the lee side of mountains are the visible indicator of the highly turbulent rotor zone beneath mountain waves. This turbulence can be extreme, with unpredictable up- and downdraughts, strong shear, and rotational forces capable of exceeding aircraft structural limits. ### Q140: What type of turbulence is found near the ground on the lee side during Foehn conditions? ^q140 - A) Clear-air turbulence (CAT) - B) Inversion turbulence - C) Thermal turbulence - D) Rotor turbulence **Correct: D)** > **Explanation:** During Foehn and mountain wave conditions, a rotor zone develops in the lower troposphere on the lee side beneath the crests of the standing waves. The rotor is a region of intense, chaotic turbulence with rotating air, strong downdrafts, and violent eddies — it is one of the most hazardous phenomena for aircraft. ### Q141: What is the greatest danger when approaching a valley airfield with strong winds blowing perpendicular to the mountain ridge? ^q141 - A) Formation of medium to heavy clear ice on all aircraft surfaces - B) Wind shear during descent, with wind direction potentially reversing by 180° - C) Reduced visibility with possible loss of sight to the airfield on final approach - D) Heavy downdrafts within rainfall areas below thunderstorm clouds **Correct: B)** > **Explanation:** When strong wind blows perpendicular to a mountain ridge, orographic lift on the windward side and mechanical turbulence create complex wind shear on the lee side. An aircraft descending into a valley airfield on the lee side may encounter severe wind shear with the wind reversing by up to 180° between altitudes. ## Foehn and Mountain Weather ### Q142: Under what conditions does Foehn typically develop? ^q142 - A) Instability with calm wind in a high-pressure area - B) Instability with widespread air blown against a mountain ridge - C) Stability with widespread air blown against a mountain ridge - D) Stability with calm wind in a high-pressure area **Correct: C)** > **Explanation:** Foehn is a warm, dry, descending wind on the lee side of a mountain range. It develops when stable air is pushed by a broad-scale pressure gradient against a mountain barrier. On the windward side, moist air rises and cools at the Saturated Adiabatic Lapse Rate after reaching the dew point, precipitating moisture. On the lee side, dry air descends at the Dry Adiabatic Lapse Rate, arriving warmer and drier than it started. ### Q143: What weather prevails on the windward side of a mountain range during Foehn? ^q143 - A) Scattered cumulus with showers and thunderstorms - B) Calm wind with high stratus (high fog) forming - C) Dissipating clouds with unusual warming and strong gusty winds - D) Layered clouds, mountains obscured, poor visibility, moderate or heavy rain **Correct: D)** > **Explanation:** On the windward (luv) side of a mountain range during Foehn conditions, moist air is forced to rise, cools at the DALR then SALR, and precipitates much of its moisture as heavy orographic rain or snow with layered cloud and poor visibility. The warm, dry and gusty descending Foehn wind occurs on the lee (downwind) side. ### Q144: What cloud phenomenon designated as "2" forms on the lee side during Foehn? ^q144 - A) Altocumulus castellanus - B) Cumulonimbus - C) Altocumulus lenticularis - D) Cumulonimbus **Correct: C)** > **Explanation:** During Foehn conditions, the air descends on the lee side and warms adiabatically, and standing wave patterns produce characteristic altocumulus lenticularis (lens-shaped wave clouds) downstream of the mountain ridge. Cumulonimbus requires strong convective instability absent in Foehn descent, and altocumulus castellanus indicates mid-level instability, not stable wave motion. ### Q145: What weather is typically experienced during Foehn in the Bavarian pre-alpine area? ^q145 - A) Nimbostratus on the northern Alps, rotor clouds on the windward side, warm and dry wind - B) Cold, humid downhill wind on the lee side with a flat pressure pattern - C) Nimbostratus on the southern Alps, rotor clouds on the lee side, warm and dry wind - D) High-pressure area over the Bay of Biscay and low-pressure area in Eastern Europe **Correct: C)** > **Explanation:** Classic Bavarian Foehn is driven by low pressure over the Gulf of Genoa and high pressure over the North Sea, forcing air southward over the Alps. Nimbostratus forms on the south (windward) side of the Alps, while on the north (lee) Bavarian side, warm and dry air descends, often accompanied by Föhnmauer (Foehn wall) and rotor clouds along the Foehn boundary. ### Q146: What typical Swiss weather situation does the sketch represent? (Showing a north-east wind between the Alps and the Jura) ^q146 - A) South Foehn situation - B) North Foehn situation - C) Bise situation - D) Westerly wind situation **Correct: C)** > **Explanation:** The sketch shows the Bise situation (north-east wind in Switzerland, between the Alps and the Jura). It is a cold, dry wind from the east-northeast, typical of anticyclonic situations centered on northern Europe. ### Q147: What typical Swiss weather situation does the sketch represent? (Showing air descending the north slope of the Alps) ^q147 - A) Westerly wind situation - B) South Foehn situation - C) North Foehn situation - D) Bise situation **Correct: B)** > **Explanation:** The sketch shows a south Foehn situation (Südföhn) in Switzerland. Air descends the north slope of the Alps, heats adiabatically and creates a warm, dry wind. ### Q148: In a NW weather situation over the Alps, what hazards should be expected in Switzerland? ^q148 - A) In winter, persistent snowfall in Ticino - B) North of the Alps: continuous precipitation; south of the Alps: very disturbed weather - C) South of the Alps generally in cloud, north of the Alps strong gusty winds - D) In summer, widespread thunderstorms south of the Alps with severe turbulence **Correct: B)** > **Explanation:** NW situation (Nordwestlage): precipitation north of the Alps, blocking effect, disturbed conditions on both sides. ## Weather Charts and Reports (METAR/TAF/GAFOR) ### Q149: What chart displays observed MSL pressure distribution along with pressure centres and fronts? ^q149 - A) Prognostic chart - B) Hypsometric chart - C) Surface weather chart - D) Significant Weather Chart (SWC) **Correct: C)** > **Explanation:** The surface weather chart (synoptic chart) displays isobars, high and low pressure centres, and frontal systems at mean sea level. A prognostic chart shows forecast conditions. The hypsometric chart shows upper-level contour heights. The SWC focuses on hazardous weather phenomena. ### Q150: What kind of chart shows areas of precipitation? ^q150 - A) GAFOR - B) Wind chart - C) Radar image - D) Satellite picture **Correct: C)** > **Explanation:** Weather radar detects the intensity and location of precipitation by measuring backscattered microwave energy from raindrops and other hydrometeors; it is the primary tool for showing precipitation areas. Satellite images show cloud cover, not precipitation directly. Wind charts show wind patterns. GAFOR is a general aviation route forecast. ### Q151: What information can be obtained from satellite images? ^q151 - A) Temperature and dew point of ambient air - B) Flight visibility, ground visibility, and ground contact - C) Overview of cloud coverage and front lines - D) Turbulence and icing **Correct: C)** > **Explanation:** Satellite imagery shows cloud cover distribution, cloud patterns, and derived front line positions across large areas. It cannot directly measure turbulence, icing, temperature/dew point profiles, or quantify ground visibility — those require other observational systems. ### Q152: What information is NOT found on a Low-Level Significant Weather Chart (LLSWC)? ^q152 - A) Information about icing conditions - B) Front lines and frontal displacement - C) Information about turbulence areas - D) Radar echoes of precipitation **Correct: D)** > **Explanation:** Low-Level Significant Weather Charts depict meteorological hazards relevant to low-altitude flight, including turbulence, icing, and frontal systems. They do not contain radar echo data, which is a real-time product displayed on weather radar imagery. LLSWC are forecast charts, not real-time radar products. ### Q153: Where can weather and operational information about the destination aerodrome be obtained during flight? ^q153 - A) PIREP - B) SIGMET - C) VOLMET - D) ATIS **Correct: D)** > **Explanation:** ATIS (Automatic Terminal Information Service) is a continuous broadcast of recorded aerodrome information including current weather, active runway, and NOTAMs, receivable by radio during flight. PIREP is pilot-reported weather en-route. SIGMET covers significant hazards over a wide area. VOLMET broadcasts meteorological information for multiple aerodromes but is less aerodrome-specific. ### Q154: What information is available in ATIS but not in a METAR? ^q154 - A) Current weather such as types of precipitation - B) Approach information such as ground visibility and cloud base - C) Mean wind speeds and maximum gust speeds - D) Operational information such as runway in use and transition level **Correct: D)** > **Explanation:** ATIS includes operational airport information such as the runway in use, transition level, approach type, and NOTAMs, which are not encoded in a METAR. A METAR does report current weather phenomena, visibility, cloud base, and wind data. ### Q155: For which areas are SIGMET warnings issued? ^q155 - A) Specific routings - B) Airports - C) Countries - D) FIRs / UIRs **Correct: D)** > **Explanation:** SIGMETs are issued for Flight Information Regions (FIRs) or Upper Information Regions (UIRs), defined blocks of airspace managed by specific ATC authorities. They are not issued for specific routes, individual countries, or individual airports. ### Q156: In a METAR, how are moderate showers of rain coded? ^q156 - A) +TSRA - B) TS - C) +RA - D) SHRA **Correct: D)** > **Explanation:** In METAR coding, the descriptor 'SH' (shower) combined with the precipitation type 'RA' (rain) gives 'SHRA' for moderate showers of rain. '+TSRA' denotes heavy thunderstorm with rain, 'TS' alone indicates thunderstorm, and '+RA' denotes heavy continuous rain. ### Q157: In a METAR, how is heavy rain designated? ^q157 - A) RA - B) SHRA - C) +SHRA - D) +RA **Correct: D)** > **Explanation:** In METAR, precipitation intensity modifiers are '+' for heavy and '-' for light. Rain is coded 'RA'; therefore '+RA' denotes heavy rain. 'RA' alone means moderate rain. 'SHRA' is shower of rain. '+SHRA' is heavy shower of rain — a convective shower, not continuous heavy rain. ### Q158: What are the wind speed and direction in this METAR: LSZB 131220Z 28015G25KT 9999 SCT035 BKN075 10/06 Q1018 NOSIG=? ^q158 - A) Wind from ESE, 15 knots, gusting to 25 knots - B) Wind from WNW, 25 knots, direction varying between WNW and SSE - C) Wind from WNW, 15 knots, direction varying between WNW and WSW - D) Wind from WNW, 15 knots, gusting to 25 knots **Correct: D)** > **Explanation:** 280° = WNW, 15 kt mean, G25 = gusts to 25 kt. ### Q159: What is the wind speed and direction in this METAR: LFSB 171100Z 29004KT 220V340 9999 FEW043 28/17 Q1013 NOSIG=? ^q159 - A) Wind from WNW, 4 knots, varying between SW and NNW - B) Wind from ESE, 4 knots, varying between NE and SSE - C) Wind from WNW, 4 knots, varying between NE and SSE - D) Wind from ESE, 4 knots, varying between SW and NNW **Correct: A)** > **Explanation:** In METAR LFSB 171100Z 29004KT 220V340: wind from 290° (WNW), 4 knots, varying between 220° (SW) and 340° (NNW). ### Q160: In a METAR, cloud base is reported in which units? ^q160 - A) Metres above sea level - B) Metres above aerodrome level - C) Feet above sea level - D) Feet above aerodrome level **Correct: D)** > **Explanation:** In a METAR, cloud base is given in feet AGL (above aerodrome level). ### Q161: What does BKN012 mean in the following METAR: LSGC 040620Z 23005KT 9000 -RA BKN012 09/08 Q1018=? ^q161 - A) 8 oktas, base at 1,200 ft - B) 5-7 oktas, base at 12,000 ft - C) 5-7 oktas, base at 1,200 ft - D) 5-7 oktas, base at 120 ft **Correct: C)** > **Explanation:** In the METAR: BKN012 means Broken (5-7 oktas) at 1200 ft. BKN = 5-7 oktas, 012 = base at 1200 ft. ### Q162: A wind barb symbol shows an arrow from the NE with one long barb and one short barb. What does this represent? ^q162 - A) Wind from SW, 30 knots - B) Wind from NE, 30 knots - C) Wind from SW, 15 knots - D) Wind from NE, 15 knots **Correct: D)** > **Explanation:** The arrow points towards the wind's origin. One long barb = 10 kt, one short barb = 5 kt. Total = 15 kt from the NE. ### Q163: A wind barb symbol points toward SW with barbs totalling 25 kt. What does it represent? ^q163 - A) Wind from NE, 25 kt - B) Wind from SW, 110 kt - C) Wind from SW, 25 kt - D) Wind from SW, 110 kt **Correct: C)** > **Explanation:** The symbol shows a wind barb arrow. An arrow pointing toward SW with one long barb (10 kt) and one short barb (5 kt) = 25 kt from SW. The tail indicates the direction from which the wind comes. ### Q164: A wind barb symbol represents wind from SSW at what speed when it shows barbs totalling 70 kt? ^q164 - A) Wind from NNE, 120 kt - B) Wind from SSW, 120 kt - C) Wind from NNE, 70 kt - D) Wind from SSW, 70 kt **Correct: D)** > **Explanation:** A wind barb pointing toward SSW with barbs representing 70 kt = wind from SSW at 70 kt. (Barbs: each long barb = 10 kt, short barb = 5 kt, pennant = 50 kt). ### Q165: On 1 June (summer time), the Swiss GAFOR valid from 06:00 to 12:00 UTC reads "XMD" for your route. What does this mean? ^q165 - A) At 09:00 LT conditions on this route will be critical - B) At 09:00 LT the route will be closed - C) At 11:00 LT the route will be closed - D) At 11:00 LT conditions will be difficult **Correct: B)** > **Explanation:** GAFOR: X = route closed, M = mountain, D = difficult. In summer time, UTC+2. The 3 letters cover 3 periods of 2 hours each. X = 06–08 UTC = 08–10 LT. At 09:00 LT (07:00 UTC), the route is closed. ### Q166: On 1 July (summer time), the Swiss GAFOR valid from 06:00 to 12:00 UTC reads "XXM" for your route. What does this mean? ^q166 - A) At 11:00 LT the route will be closed - B) At 09:00 LT the route will be critical - C) At 10:00 LT the route will be difficult - D) At 11:00 LT the route will be critical **Correct: D)** > **Explanation:** GAFOR 'XXM' in summer time in Switzerland: GAFOR valid 06:00-12:00 UTC = 08:00-14:00 CEST. X=closed, X=closed, M=difficult. So at 11:00 LT (09:00 UTC) the route is closed. ### Q167: On 1 August (summer time), the Swiss GAFOR valid from 06:00 to 12:00 UTC reads "DDO" for your route. What does this mean? ^q167 - A) At 14:00 LT the route will be difficult - B) At 08:00 LT the route will be critical - C) At 11:00 LT the route will be critical - D) At 13:00 LT the route will be open **Correct: D)** > **Explanation:** GAFOR 'DDO' summer: valid 06:00-12:00 UTC = 08:00-14:00 CEST. D=difficult, D=difficult, O=open. At 13:00 LT = 11:00 UTC → O (open). ### Q168: Referring to the Low Level SWC chart, which statement about areas A, B, and C is correct? ^q168 - A) Area B has cumuliform clouds with possible light freezing rain or fog - B) Area A lies between two warm fronts - C) Rain and snow showers are expected in area A - D) Isolated thunderstorms may occur in area C with no icing or turbulence **Correct: C)** > **Explanation:** According to the SWC chart, area A is in the cold post-frontal sector with rain and snow showers. ### Q169: What weather phenomena should be expected along the route from LOWK to EDDP according to the synoptic chart? ^q169 - A) Progressive temperature increase, tailwind, isolated thunderstorms - B) Progressive temperature increase, headwind, no thunderstorms - C) Progressive temperature decrease, tailwind, isolated thunderstorms - D) Progressive temperature decrease, headwind, isolated thunderstorms **Correct: D)** > **Explanation:** According to the synoptic chart, the LOWK-EDDP route (crossing central Europe) shows progressive temperature decrease (heading north), headwind per the situation, and isolated thunderstorms in summer. ### Q170: What weather do you expect within zone 1 (south of France) at 3,500 ft AMSL according to the weather chart? ^q170 - A) 5-8 oktas of stratiform clouds, isolated thunderstorms, surface turbulence - B) 3-4 oktas of stratiform clouds between 2,000 ft and 7,000 ft, visibility 8 km, turbulence below FL 070 - C) Isolated thunderstorms, visibility 5 km outside showers, no turbulence below FL 070 - D) Moderate icing, isolated thunderstorms with showers and turbulence **Correct: D)** > **Explanation:** In zone 1 (south of France) at 3500 ft AMSL, with active CB (cumulonimbus), one can expect: moderate icing, isolated thunderstorms with showers and turbulence. ## Soaring Weather ### Q171: What clouds and weather result when humid, unstable air is pushed against a mountain range and forced to rise? ^q171 - A) Overcast low stratus (high fog) with no precipitation - B) Embedded cumulonimbus with thunderstorms and showers of hail or rain - C) Thin altostratus and cirrostratus with light, steady precipitation - D) Smooth nimbostratus with light drizzle or snow in winter **Correct: B)** > **Explanation:** When unstable, humid air is forced to rise orographically, it triggers convective instability — air that is conditionally unstable becomes absolutely unstable once lifting begins. The resulting rapid ascent fuels cumulonimbus development, producing embedded CBs with thunderstorms, heavy showers, and hail. Stable air masses under the same conditions produce layered clouds (Ns or As) with steady rain, not convective storms. ### Q172: What are "blue thermals"? ^q172 - A) Descending air between cumulus clouds - B) Thermals with less than 4/8 cumulus coverage - C) Thermals that rise without producing cumulus clouds - D) Turbulence in the vicinity of cumulonimbus clouds **Correct: C)** > **Explanation:** "Blue thermals" exist when the lifting condensation level (LCL) is very high — the air is too dry to reach its dew point before the thermal tops out. As a result, thermals rise but no cumulus clouds form, leaving the sky clear ("blue"). For glider pilots this is challenging since there are no visual cloud markers to indicate thermal location, and the cloudbase is beyond the thermal ceiling. ### Q173: The "beginning of thermals" refers to the moment when thermal strength does what? ^q173 - A) Reaches up to 600 m AGL and forms cumulus clouds - B) Becomes usable for cross-country gliding through cumulus formation - C) Becomes usable for gliding and reaches up to 1,200 m MSL - D) Becomes usable for gliding and reaches up to 600 m AGL **Correct: D)** > **Explanation:** Thermal activity is considered to have "begun" when thermals are strong enough to support gliding and extend to at least 600 m AGL — sufficient altitude to work the lift. Below this height, thermals may exist but are too shallow to be safely exploited by a glider. Cloud formation is not a prerequisite; blue thermals can also mark the beginning of usable thermal activity. ### Q174: What does the term "trigger temperature" mean? ^q174 - A) The minimum surface temperature needed for cumulus clouds to form from thermal lifts - B) The temperature a thermal reaches at the altitude where cumulus formation begins - C) The minimum surface temperature for a thunderstorm to develop from a cumulus cloud - D) The maximum surface temperature that can be reached without thunderstorm formation **Correct: A)** > **Explanation:** The trigger temperature is the minimum surface temperature that must be reached before thermals can rise to the condensation level and form cumulus clouds. It is derived from the aerological diagram (tephigram/Stüve diagram) by tracing the dry adiabatic lapse rate from the morning sounding's moisture level back to the surface. Until this temperature is reached, thermals may exist but will not produce cumulus markers. ### Q175: What does "over-development" refer to in a weather report? ^q175 - A) Cumulus clouds spreading out below an inversion layer - B) A thermal low developing into a storm depression - C) A change from blue thermals to cloudy thermals in the afternoon - D) Vertical development of cumulus clouds into rain showers **Correct: D)** > **Explanation:** Over-development occurs when cumulus clouds continue growing vertically beyond the thermal inversion or become self-sustaining through latent heat release, developing into cumulonimbus (Cb) with heavy rain showers, lightning, and hail. This typically happens during humid summer afternoons when atmospheric instability is high and the inhibiting layer is weak. For glider pilots, over-development signals the end of safe soaring conditions and a need to land. ### Q176: The soaring forecast states environmental instability. Morning dew covers the grass and no thermals are active. What thermal development can be expected? ^q176 - A) Dew formation prevents all thermal activity for the day - B) After sunset and formation of a ground-level inversion, thermals are likely - C) With continued solar heating, thermal lifting is likely to begin - D) Environmental instability prevents air from being lifted, so no thermals will form **Correct: C)** > **Explanation:** Morning dew indicates the air cooled to the dew point overnight (radiation cooling), but this is temporary. Once solar insolation heats the ground, the surface temperature rises, warming the air above it until the temperature exceeds the trigger temperature. Environmental instability means the lapse rate is steep enough to sustain thermals once they begin, so good thermal conditions are likely to develop during the morning hours. ### Q177: Thickening cirrus clouds approaching from one direction and blocking the sun will cause what change in thermal activity? ^q177 - A) Cirrus clouds indicate instability and the onset of over-development - B) Cirrus clouds reduce insolation and weaken thermal activity - C) Cirrus clouds can intensify insolation and improve thermals - D) Cirrus clouds signal a high-level inversion with thermal activity continuing to that level **Correct: B)** > **Explanation:** Thermals are driven by differential heating of the ground by solar radiation. Thickening cirrus clouds progressively filter out solar energy, reducing ground heating and therefore thermal strength and depth. Dense cirrus can reduce insolation enough to stop thermal activity entirely. Additionally, approaching cirrus from one direction often indicates an advancing warm front, which brings widespread cloud, stable conditions, and further suppression of thermals. ### Q178: What does the term "shielding" refer to? ^q178 - A) Coverage of cumulus clouds stated as a fraction of the sky in oktas - B) The anvil-like structure at the top of a thunderstorm cloud - C) Nimbostratus covering the windward side of a mountain range - D) High or mid-level cloud layers that impair thermal activity **Correct: D)** > **Explanation:** Shielding describes the effect of high or medium cloud layers (cirrus, cirrostratus, altostratus) that block solar radiation and suppress thermal development below. Even partial cloud cover at these levels can significantly reduce ground insolation. Gliding forecasts include shielding assessments to indicate when and where thermals will be weakened or absent. ### Q179: What weather conditions are typical of summer high-pressure areas in Central Europe? ^q179 - A) Small isobar spacing with calm winds and local wind systems - B) Large isobar spacing with strong prevailing westerlies - C) Large isobar spacing with calm winds and local wind systems forming - D) Small isobar spacing with strong prevailing northerlies **Correct: C)** > **Explanation:** In summer, high pressure areas over Central Europe produce widely spaced isobars, meaning weak pressure gradients and calm synoptic winds; this allows local thermally driven wind systems (valley breezes, sea breezes) to develop. Small isobar spacing means strong winds. Strong synoptic flow is associated with low-pressure systems. ### Q180: What weather conditions prevail in winter high-pressure areas? ^q180 - A) Squall lines and thunderstorms - B) Calm winds with widespread high fog - C) Calm weather with cloud dissipation and a few high cumulus - D) Changing weather with passing frontal lines **Correct: B)** > **Explanation:** In winter, high pressure areas favour calm winds and surface-based temperature inversions that trap moisture near the ground, leading to widespread high fog (Hochnebel) or stratus. Frontal weather is associated with lows, thunderstorms require instability absent in winter highs, and option C describes summer conditions. ### Q181: What weather in summer high-pressure areas brings calm conditions with only scattered fair-weather cumulus? ^q181 - A) Squall lines and thunderstorms - B) Calm weather with cloud dissipation and a few high cumulus - C) Changing weather with frontal passages - D) Calm winds with widespread high fog **Correct: B)** > **Explanation:** In summer, high pressure areas bring calm synoptic winds and subsidence suppresses deep convection, resulting in sunny skies with possible development of small fair-weather cumulus. Frontal weather is associated with lows, squall lines require instability, and fog is typical of winter or overnight conditions. ### Q182: Under which precipitation type is the least danger to aviation? ^q182 - A) Heavy snowfall - B) Rain showers - C) Drizzle - D) Hail **Correct: C)** > **Explanation:** Drizzle is the least dangerous precipitation for aviation as its droplets are very small and quantity is low. Hail, snow, and heavy showers are much more dangerous.