182 questions
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.
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.
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.
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.
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.
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.
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.
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.
Correct: D)
Explanation: The transition from liquid to gaseous state (evaporation) requires heat input (latent heat of evaporation). Conversely, condensation and solidification release heat.
Correct: C)
Explanation: Transition from gaseous to liquid state (condensation) releases heat. Condensation releases the latent heat previously absorbed during evaporation.
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).
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.
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.
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.
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.
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.
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.
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.
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.
Correct: C)
Explanation: ISA lapse rate = -2°C/1000 ft. Difference: 8600 - 5600 = 3000 ft. Temperature: 5°C - (3 × 2) = -1°C.
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.
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.
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.
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.
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.
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.
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.
Correct: C)
Explanation: A descending air mass (subsidence) is adiabatically compressed: volume decreases and temperature increases. The air descends and warms.
Correct: C)
Explanation: A rising air mass expands adiabatically: volume increases and temperature decreases. This is adiabatic cooling.
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.
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.
Correct: C)
Explanation: A warm air mass that cools from below becomes more stable (reduced temperature gradient). This promotes stratiform clouds, not convective clouds.
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.
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.
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.
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.
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.
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.
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.
Correct: D)
Explanation: QFE = atmospheric pressure measured at aerodrome level (station). The altimeter reads 0 on the ground.
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.
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.
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.
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.
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.
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).
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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).
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).
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.
Correct: D)
Explanation: Frontal zones (transitions between air masses) produce the strongest wind gradients and turbulence.
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.
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.
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.
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.
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.
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).
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).
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.
Correct: C)
Explanation: The CB (cumulonimbus) is the most dangerous cloud: severe turbulence, lightning, hail, wind shear, icing.
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.
Correct: B)
Explanation: Cumulonimbus (Cb) are the clouds that produce the heaviest showers, hail, and thunderstorms. They contain enormous quantities of water and ice.
Correct: C)
Explanation: Drizzle is associated with stratus clouds (low stratiform clouds). Stratus produce fine, continuous drizzle. Cumulonimbus produce intense showers.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
Correct: D)
Explanation: Visibility 1–5 km with water droplets = mist (BR). Fog = visibility < 1 km.
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.
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.
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.
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.
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.
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).
Correct: C)
Explanation: If temperature rises (without adding moisture), the air can hold more water vapour → relative humidity decreases.
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.
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.
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.
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.
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.
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.
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.
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.
Correct: B)
Explanation: An unstable cold front in summer generates convective clouds (CB, TCu) with showers and thunderstorms.
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.
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.
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.
Correct: C)
Explanation: Warm and humid air sliding over cold air (warm front) = stratiform clouds, continuous rain, lowering cloud base.
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.
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.
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.
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.
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.
Correct: C)
Explanation: Maritime polar air is unstable (cold below, moist) → convection → showers in all seasons.
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.
Correct: D)
Explanation: Point C is located ahead of the approaching depression/front → pressure will fall.
Correct: C)
Explanation: The approach of an anticyclone causes a pressure rise at the nearby point in the next hour.
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.
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.
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.
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.
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.
Correct: C)
Explanation: Thunderstorms = slack pressure gradient (low pressure gradient) + strong surface heating (instability) + high 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.
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'.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
Correct: B)
Explanation: NW situation (Nordwestlage): precipitation north of the Alps, blocking effect, disturbed conditions on both sides.
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.
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.
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.
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.
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.
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.
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.
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.
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.
Correct: D)
Explanation: 280° = WNW, 15 kt mean, G25 = gusts to 25 kt.
Correct: A)
Explanation: In METAR LFSB 171100Z 29004KT 220V340: wind from 290° (WNW), 4 knots, varying between 220° (SW) and 340° (NNW).
Correct: D)
Explanation: In a METAR, cloud base is given in feet AGL (above aerodrome level).
Correct: C)
Explanation: In the METAR: BKN012 means Broken (5-7 oktas) at 1200 ft. BKN = 5-7 oktas, 012 = base at 1200 ft.
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.
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.
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).
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.
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.
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).
Correct: C)
Explanation: According to the SWC chart, area A is in the cold post-frontal sector with rain and snow showers.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
