### Q151: Updrafts along a mountain slope can be strengthened by... ^t50q151 - A) Warming of upper atmospheric layers - B) Thermal radiation from the windward side at night - C) Solar heating on the lee side - D) Solar heating on the windward side **Correct: D)** > **Explanation:** Solar heating on the windward slope warms the surface air, making it less dense and creating anabatic (upslope) flow that combines with the mechanical orographic lift from the oncoming wind, significantly strengthening the updraft. This is why south- and west-facing slopes in the Northern Hemisphere often produce the strongest lift during sunny afternoons. Option A (warming of upper layers) would increase stability and suppress convection. Option B (nighttime radiation from the windward side) produces cooling and katabatic (downslope) flow, the opposite of updrafts. Option C (solar heating on the lee side) does not contribute to windward-side updrafts. ### Q152: The prefix used for clouds in the high layers is... ^t50q152 - A) Alto-. - B) Nimbo-. - C) Strato-. - D) Cirro-. **Correct: D)** > **Explanation:** The prefix "Cirro-" identifies clouds in the high cloud family, typically found above approximately 6000 m (FL200) in mid-latitudes, and includes cirrus, cirrocumulus, and cirrostratus — all composed primarily of ice crystals. Option A ("Alto-") designates mid-level clouds between roughly 2000 and 6000 m, such as altostratus and altocumulus. Option B ("Nimbo-") indicates rain-producing clouds regardless of altitude, such as nimbostratus. Option C ("Strato-") refers to layered cloud forms at low to mid levels. ### Q153: What factor may limit the vertical extent of cumulus clouds at the top? ^t50q153 - A) The presence of an inversion layer - B) The absolute humidity - C) Relative humidity - D) The spread **Correct: A)** > **Explanation:** An inversion layer creates a zone where temperature increases with altitude, forming a highly stable lid that stops rising thermals from penetrating further upward. Cumulus clouds reaching this barrier flatten out and spread horizontally rather than continuing to develop vertically, which is why fair-weather cumulus often have a uniform top height. Option D (the spread, i.e., temperature minus dew point) determines cloud base height, not cloud top. Options B (absolute humidity) and C (relative humidity) influence whether clouds form at all but do not cap their vertical extent the way an inversion does. ### Q154: Which factors point toward a tendency for fog formation? ^t50q154 - A) Strong winds with falling temperature - B) Low pressure with rising temperature - C) Small spread with falling temperature - D) Small spread with rising temperature **Correct: C)** > **Explanation:** A small spread (temperature close to dew point) means the air is already near saturation, and falling temperature will close the remaining gap, causing condensation at or near the surface — fog. These are the classic pre-fog conditions monitored by pilots and forecasters. Option A (strong winds) promotes turbulent mixing that prevents the surface layer from reaching saturation. Option B (low pressure with rising temperature) widens the spread and favours lifting rather than surface fog. Option D (rising temperature) increases the spread, moving conditions away from saturation. ### Q155: What process gives rise to orographic fog (hill fog)? ^t50q155 - A) Extended radiation on cloud-free nights - B) Evaporation from warm, moist ground into very cold air - C) Cold, moist air mixing with warm, moist air - D) Warm, moist air forced over a hill or mountain range **Correct: D)** > **Explanation:** Orographic fog (hill fog) forms when warm, moist air is forced to ascend over elevated terrain, cooling adiabatically until it reaches the dew point and condenses. The resulting cloud envelops the hill or mountain and appears as fog to anyone on the slope or summit. Option A describes the formation mechanism of radiation fog, which occurs on calm, clear nights over flat terrain. Option B describes steam fog (or evaporation fog), which forms when cold air passes over much warmer water or moist surfaces. Option C describes frontal or mixing fog, a different process entirely. ### Q156: What is needed for precipitation to form inside clouds? ^t50q156 - A) High humidity and elevated temperatures - B) An inversion layer - C) Moderate to strong updrafts - D) Calm winds and intense solar insolation **Correct: C)** > **Explanation:** Precipitation particles need time to grow large enough to fall against the updraft, either through collision-coalescence (warm rain process) or the Bergeron ice-crystal process. Moderate to strong updrafts keep water droplets and ice crystals suspended in the cloud long enough for this growth to occur. Option A (high humidity and elevated temperatures) favours cloud formation but does not ensure particles grow to precipitation size. Option B (an inversion layer) suppresses cloud development and works against precipitation. Option D (calm winds and sunshine) describes surface conditions that do not directly produce in-cloud precipitation. ### Q157: In areas where isobars are widely spaced, what wind conditions should be expected? ^t50q157 - A) Strong prevailing easterly winds with rapid backing - B) Strong prevailing westerly winds with rapid veering - C) Local wind systems developing with strong prevailing westerly winds - D) Variable winds with the development of local wind systems **Correct: D)** > **Explanation:** Widely spaced isobars indicate a weak horizontal pressure gradient, which produces only light synoptic-scale winds. In the absence of a dominant pressure-driven flow, local thermally driven wind systems — such as valley-mountain breezes, sea-land breezes, and slope winds — become the primary circulation features, with wind direction varying throughout the day. Options A, B, and C all describe strong prevailing winds, which require closely spaced isobars (a steep pressure gradient) and are therefore inconsistent with the wide spacing described. ### Q158: Under what circumstances does back side weather (Rückseitenwetter) occur? ^t50q158 - A) After passage of a warm front - B) During Foehn on the lee side - C) Before passage of an occlusion - D) After passage of a cold front **Correct: D)** > **Explanation:** "Back-side weather" (Rückseitenwetter) describes the conditions in the cold, unstable polar air mass that follows behind a cold front on the western or northwestern side of a low-pressure system. It is characterized by good visibility, convective cumulus clouds, and scattered showers or snow showers. Option A (after a warm front) leads into the warm sector, not the cold back side. Option B (Foehn on the lee side) is a thermodynamic mountain phenomenon unrelated to frontal weather. Option C (before an occlusion) describes pre-frontal conditions, not back-side weather. ### Q159: How is a wind reported as 225/15 described? ^t50q159 - A) South-west wind at 15 km/h - B) North-east wind at 15 km/h - C) North-east wind at 15 kt - D) South-west wind at 15 kt **Correct: D)** > **Explanation:** In aviation weather reporting, wind is always given as the direction FROM which it blows (in degrees true) followed by speed in knots. A report of 225/15 means wind from 225 degrees (southwest) at 15 knots. Options B and C incorrectly interpret 225 degrees as northeast, perhaps confusing the direction the wind blows from with the direction it blows toward. Option A gives the correct direction but uses km/h instead of the standard aviation unit of knots. ### Q160: In the Bavarian area near the Alps, what weather typically accompanies Foehn conditions? ^t50q160 - A) Nimbostratus on the northern Alps, rotor clouds on the windward side, warm dry wind - B) High pressure over Biscay and a low over Eastern Europe - C) Cold, humid downslope wind on the lee side, flat pressure pattern - D) Nimbostratus on the southern Alps, rotor clouds on the lee side, warm dry wind **Correct: D)** > **Explanation:** During Foehn in the Bavarian pre-alpine region, the prevailing southerly flow forces moist air up the southern (Italian) side of the Alps, producing nimbostratus and heavy orographic precipitation there. As the air descends on the northern (Bavarian) lee side, it warms adiabatically and dries out, creating the characteristic warm, dry, gusty Foehn wind. Rotor clouds and lenticular clouds form on the lee side due to wave activity. Option A incorrectly places nimbostratus on the northern side and rotors on the windward side. Option B describes a synoptic pattern, not the weather itself. Option C contradicts the definition of Foehn, which produces warm, dry — not cold, humid — descending air. ### Q161: Clouds are fundamentally classified into which two basic types? ^t50q161 - A) Stratiform and ice clouds - B) Layered and lifted clouds - C) Thunderstorm and shower clouds - D) Cumulus and stratiform clouds **Correct: D)** > **Explanation:** The fundamental cloud classification divides all clouds into two basic forms based on their physical formation process: cumuliform (convective, vertically developed clouds formed by localized updrafts) and stratiform (layered, horizontally extended clouds formed by widespread, gentle lifting or cooling). All other cloud types and subtypes derive from combinations of these two basic forms. Option A incorrectly pairs stratiform with "ice clouds," which is a composition category, not a form. Option B uses non-standard terminology. Option C names specific weather phenomena rather than fundamental cloud forms. ### Q162: During Foehn conditions, what weather phenomenon marked as "2" should be expected on the lee side? See figure (MET-001). Siehe Anlage 1 ^t50q162 - A) Altocumulus Castellanus - B) Cumulonimbus - C) Altocumulus lenticularis - D) Cumulonimbus **Correct: C)** > **Explanation:** On the lee side during Foehn conditions, the descending air creates standing wave patterns downwind of the mountain ridge. These waves produce Altocumulus lenticularis — smooth, lens-shaped or almond-shaped clouds that remain stationary relative to the terrain despite strong winds passing through them. They are a hallmark of mountain wave activity. Options B and D (cumulonimbus) are associated with deep convective instability, not the stable laminar wave flow characteristic of Foehn. Option A (Altocumulus castellanus) indicates mid-level convective instability with turret-like protrusions, which is a different meteorological situation. ### Q163: When very small water droplets and ice crystals strike the leading surfaces of an aircraft, which type of ice forms? ^t50q163 - A) Hoar frost - B) Clear ice - C) Rime ice - D) Mixed ice **Correct: C)** > **Explanation:** Rime ice forms when very small supercooled water droplets freeze instantly upon contact with the aircraft's leading edges, trapping air between the frozen particles and creating a rough, white, opaque deposit. Because the droplets are so small, they freeze before they can spread, resulting in the characteristic granular texture. Option B (clear ice) forms from larger supercooled droplets that flow along the surface before freezing, producing a smooth, transparent, dense layer. Option D (mixed ice) is a combination of rime and clear ice. Option A (hoar frost) forms by direct deposition of water vapour onto cold surfaces, not by droplet impact. ### Q164: Which chart contains information about pressure patterns and frontal positions? ^t50q164 - A) Significant Weather Chart (SWC) - B) Surface weather chart. - C) Hypsometric chart - D) Wind chart. **Correct: B)** > **Explanation:** The surface weather chart (synoptic analysis chart) is the primary meteorological product displaying isobars (lines of equal pressure at MSL), the locations of highs and lows, and the positions and types of fronts (warm, cold, occluded, stationary). Option A (Significant Weather Chart) focuses on aviation hazards such as turbulence, icing, and significant cloud coverage, but does not show the full surface pressure pattern. Option C (hypsometric chart) depicts the heights of constant-pressure surfaces in the upper atmosphere. Option D (wind chart) shows wind speed and direction at specific levels without pressure or frontal information. ### Q165: What is the typical cloud sequence observed during the approach and passage of a warm front? ^t50q165 - A) Squall line with rain showers and thunderstorms (Cb), gusty wind followed by cumulus with isolated showers - B) In coastal areas, daytime wind from the coast with cumulus forming, clouds dissipating in the evening - C) Cirrus, thickening altostratus and altocumulus, lowering cloud base with rain, nimbostratus - D) Wind calming, cloud dissipation and warming in summer; extensive high fog layers forming in winter **Correct: C)** > **Explanation:** The approach of a warm front produces a characteristic descending cloud sequence as the warm air gradually overrides the retreating cold air mass. First, thin cirrus appears at high altitude, followed by cirrostratus, then progressively thickening altostratus and altocumulus at mid-levels, and finally nimbostratus with a low cloud base and prolonged steady rain. Option A describes cold front or squall line weather. Option B describes a coastal sea-breeze cycle unrelated to frontal meteorology. Option D describes anticyclonic subsidence or continental high-pressure conditions. ### Q166: What phenomenon results from cold-air downdrafts carrying precipitation from a fully developed thunderstorm cloud? ^t50q166 - A) Anvil-head top of the Cb cloud - B) Freezing rain - C) Electrical discharge - D) Gust front **Correct: D)** > **Explanation:** In a mature thunderstorm, precipitation drags cold air downward in powerful downdrafts. When this cold, dense air reaches the surface, it spreads outward rapidly as a density current, creating a gust front — a sharp boundary marked by sudden wind shifts, temperature drops, and gusty conditions that can extend several kilometres ahead of the storm. Option A (anvil-head top) is a structural feature shaped by upper-level winds, not caused by downdrafts reaching the surface. Option C (electrical discharge) results from charge separation within the cloud. Option B (freezing rain) requires a specific temperature inversion profile, not downdraft spreading. ### Q167: Which item is NOT included on Low-Level Significant Weather Charts (LLSWC)? ^t50q167 - A) Frontal lines and frontal displacement - B) Turbulence area information - C) Icing condition information - D) Radar echoes of precipitation **Correct: D)** > **Explanation:** Low-Level Significant Weather Charts are forecast products that depict meteorological hazards below a specified altitude, including frontal systems and their movement (option A), turbulence areas (option B), and icing conditions (option C). However, they do not contain radar echoes of precipitation (option D) because radar imagery is a real-time observational product, whereas LLSWC are prognostic charts prepared in advance. Precipitation areas may be indicated symbolically on LLSWC, but actual radar returns are found only on separate radar displays. ### Q168: Which cloud type produces prolonged, steady rain? ^t50q168 - A) Cirrostratus - B) Altocumulus - C) Nimbostratus - D) Cumulonimbus **Correct: C)** > **Explanation:** Nimbostratus (Ns) is a thick, dark grey, amorphous layer cloud that produces continuous, steady precipitation (rain or snow) over wide areas, typically associated with warm fronts or occlusions. Its great vertical and horizontal extent ensures prolonged precipitation reaching the ground. Option A (cirrostratus) is a thin, high-level ice cloud that does not produce surface precipitation. Option B (altocumulus) is a mid-level cloud that occasionally produces virga but not sustained surface rain. Option D (cumulonimbus) produces intense but short-lived showers and thunderstorms rather than prolonged steady rain. ### Q169: Based on cloud type, how is precipitation classified? ^t50q169 - A) Light and heavy precipitation. - B) Prolonged rain and continuous rain. - C) Showers of snow and rain. - D) Rain and showers of rain. **Correct: D)** > **Explanation:** Meteorological classification of precipitation by cloud type distinguishes two fundamental categories: rain (steady, continuous precipitation from stratiform clouds like nimbostratus) and showers of rain (intermittent, convective precipitation from cumuliform clouds like cumulonimbus or cumulus congestus). This distinction reflects the physical formation process — widespread lifting versus localized convection. Option A classifies by intensity rather than cloud type. Option B uses redundant terminology that does not distinguish cloud origins. Option C classifies by precipitation phase (snow versus rain), not by cloud type. ### Q170: Which conditions favour thunderstorm development? ^t50q170 - A) Clear night over land with cold air and fog patches - B) Warm, dry air under a strong inversion layer - C) Calm winds with cold air, overcast St or As cloud cover - D) Warm, humid air with a conditionally unstable environmental lapse rate **Correct: D)** > **Explanation:** Thunderstorm development requires three essential ingredients: moisture (warm, humid air provides the latent heat fuel), instability (a conditionally unstable lapse rate allows saturated air parcels to accelerate upward), and a lifting mechanism (fronts, orographic forcing, or surface heating). Option D combines the first two ingredients explicitly. Option A describes calm, stable nighttime conditions favouring radiation fog, not convection. Option B features a strong inversion that would cap any vertical development. Option C describes a stable, overcast situation with stratus or altostratus, which suppresses thunderstorm formation. ### Q171: When isobars on a surface weather chart are widely spaced, what does this indicate about the prevailing wind? ^t50q171 - A) Strong pressure gradients producing strong prevailing wind - B) Weak pressure gradients producing light prevailing wind - C) Strong pressure gradients producing light prevailing wind - D) Weak pressure gradients producing strong prevailing wind **Correct: B)** > **Explanation:** The spacing of isobars on a surface weather chart is inversely proportional to the pressure gradient: widely spaced isobars mean a small pressure difference over a large distance (weak gradient), which produces only light wind. Wind speed is directly driven by the pressure gradient force, so a weak gradient means weak wind. Option A contradicts itself by associating wide spacing with strong gradients. Option C pairs a strong gradient with light wind, which is meteorologically incorrect. Option D reverses the gradient-wind relationship. ### Q172: An air mass arriving in Central Europe from the Russian continent during winter is described as... ^t50q172 - A) Continental tropical air - B) Maritime polar air - C) Continental polar air - D) Maritime tropical air **Correct: C)** > **Explanation:** Air masses are classified by their source region's surface characteristics. Air originating over the vast, snow-covered Russian (Siberian) continent during winter acquires cold temperatures and very low moisture content, making it Continental Polar (cP). This air mass brings bitterly cold, dry conditions to Central Europe when it advects westward. Option B (maritime polar) originates over polar oceans and carries significant moisture. Option A (continental tropical) and option D (maritime tropical) originate in warm regions and are far too warm and/or moist to describe Siberian winter air. ### Q173: What clouds and weather are typically observed during the passage of a cold front? ^t50q173 - A) Strongly developed Cb clouds with rain showers and thunderstorms, gusty wind followed by cumulus with isolated showers - B) Wind calming, cloud dissipation and warming in summer; extensive high fog in winter - C) Cirrus, thickening altostratus and altocumulus, lowering cloud base with rain, nimbostratus - D) In coastal areas, daytime onshore wind with cumulus forming, clouds dissipating in evening **Correct: A)** > **Explanation:** Cold front passage is marked by a narrow band of intense weather as the advancing cold air undercuts the warm air, forcing it rapidly aloft. This produces strongly developed cumulonimbus (Cb) clouds, heavy rain showers, thunderstorms, and gusty winds along the frontal line, followed by cumulus with isolated showers in the cold, unstable air behind the front. Option C describes the gradual cloud sequence of an approaching warm front. Option B describes anticyclonic or high-pressure settling conditions. Option D describes a coastal sea-breeze pattern unrelated to frontal weather. ### Q174: When an aircraft is struck by lightning, what is the most immediate danger? ^t50q174 - A) Disrupted radio communication and static noise - B) Rapid cabin depressurisation and smoke in the cabin - C) Surface overheating and damage to exposed aircraft parts - D) Explosion of electrical equipment in the cockpit **Correct: C)** > **Explanation:** The most immediate physical danger from a lightning strike is surface overheating at the attachment and exit points, along with damage to exposed components such as antennas, pitot tubes, wingtips, and control surface edges. The extreme heat at the strike points can burn through thin skins, pit metal surfaces, and damage composite materials. Option A (disrupted radio communication) is a secondary effect that does not pose an immediate structural threat. Option B (cabin depressurisation) applies primarily to pressurised aircraft and is not the most common immediate consequence. Option D (explosion of cockpit equipment) is extremely unlikely in certified aircraft with proper lightning protection. ### Q175: What is meant by mountain wind? ^t50q175 - A) A wind blowing uphill from the valley during daytime. - B) A wind blowing down the mountain slope at night. - C) A wind blowing uphill from the valley at night. - D) A wind blowing down the mountain slope during daytime. **Correct: B)** > **Explanation:** Mountain wind (Bergwind) is a katabatic flow that occurs at night when mountain slopes cool by radiation faster than the free atmosphere at the same altitude. The cooled, denser air drains downslope under gravity toward the valley floor. This is part of the diurnal mountain-valley wind cycle. Option A describes valley wind (Talwind), which is the daytime anabatic upslope flow caused by solar heating. Option C reverses the nighttime flow direction. Option D reverses the daytime flow direction. ### Q176: What is the average value of the saturated adiabatic lapse rate? ^t50q176 - A) 0° C / 100 m. - B) 2° C / 1000 ft. - C) 1,0° C / 100 m. - D) 0,6° C / 100 m. **Correct: D)** > **Explanation:** The saturated (moist) adiabatic lapse rate averages approximately 0.6 degrees C per 100 m. It is lower than the dry adiabatic lapse rate (1.0 degrees C per 100 m) because latent heat released during condensation partially offsets the cooling of the ascending air parcel. Option A (0 degrees C per 100 m) would mean no temperature change with altitude, which is physically unrealistic for a rising air parcel. Option B (2 degrees C per 1000 ft, approximately 0.66 degrees C per 100 m) is a rough approximation but not the standard textbook value. Option C (1.0 degrees C per 100 m) is the dry adiabatic lapse rate, not the saturated rate. ### Q177: Throughout the year, extensive high pressure areas are found... ^t50q177 - A) In tropical regions near the equator. - B) Over oceanic areas at approximately 30°N/S latitude. - C) In mid-latitudes along the polar front. - D) In areas with extensive lifting processes. **Correct: B)** > **Explanation:** The subtropical high-pressure belt at approximately 30 degrees N and S latitude is a semi-permanent feature of the global atmospheric circulation, created by the descending branch of the Hadley cell. Warm air rising near the equator flows poleward aloft, cools, and subsides in the subtropics, forming persistent anticyclones over the oceans (e.g., the Azores High, the Pacific High). Option A (equatorial regions) is dominated by the low-pressure Intertropical Convergence Zone (ITCZ). Option C (mid-latitudes along the polar front) is a zone of cyclonic activity and low pressure. Option D (areas with extensive lifting) produce low pressure by definition, not high pressure. ### Q178: During flight, weather and operational information about the destination aerodrome can be obtained via... ^t50q178 - A) SIGMET - B) ATIS. - C) PIREP - D) VOLMET. **Correct: B)** > **Explanation:** ATIS (Automatic Terminal Information Service) is a continuous broadcast available on a dedicated frequency at equipped aerodromes, providing current weather observations, active runway, transition level, approach procedures, and relevant NOTAMs specific to that aerodrome. Pilots tune in to the ATIS frequency during flight to obtain up-to-date destination information. Option A (SIGMET) covers significant weather hazards across an entire FIR, not aerodrome-specific data. Option C (PIREP) contains pilot-reported weather conditions en route. Option D (VOLMET) broadcasts weather for multiple aerodromes but is less comprehensive than ATIS for a specific destination. ### Q179: Identify the cloud type shown in the picture. See figure (MET-002). Siehe Anlage 2 ^t50q179 - A) Cumulus - B) Cirrus - C) Stratus - D) Altus **Correct: A)** > **Explanation:** The cloud in figure MET-002 is cumulus, identifiable by its characteristic flat base (marking the condensation level) and vertically developed, cauliflower-like top with sharp white outlines against the blue sky. Cumulus clouds form through thermal convection and are the clouds most associated with soaring flight. Option B (cirrus) would appear as thin, wispy ice-crystal filaments at very high altitude. Option C (stratus) would present as a uniform, featureless grey layer. Option D ("altus") is not a recognized cloud genus in the international cloud classification system. ### Q180: What determines the character of an air mass? ^t50q180 - A) Wind speed and tropopause height - B) Region of origin and trajectory during movement - C) Environmental lapse rate at the source - D) Temperatures at both origin and present location **Correct: B)** > **Explanation:** An air mass acquires its temperature and moisture properties from the surface conditions of its source region (e.g., polar continent, tropical ocean) and then modifies as it travels over different surfaces along its trajectory. Both the origin (which sets the initial character) and the path (which modifies it) are essential for classifying and forecasting air mass behaviour. Option A (wind speed and tropopause height) are dynamic properties, not defining characteristics. Option C (environmental lapse rate at source) is a consequence of the air mass properties, not their cause. Option D (temperatures at origin and present location) captures only temperature while ignoring the critical moisture dimension. ### Q181: What cloud type is commonly observed across extensive high-pressure areas in summer? ^t50q181 - A) Squall lines and thunderstorms - B) Overcast nimbostratus - C) Scattered cumulus clouds - D) Overcast low stratus **Correct: C)** > **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 (option D) is associated with stable, moist air at low levels, common in autumn or maritime high-pressure situations. Nimbostratus (option B) is associated with frontal systems. Squall lines and thunderstorms (option A) require convective instability and moisture not typical of settled high-pressure conditions. ### Q182: The symbol marked (1) in the figure represents which frontal type? See figure (MET-005) Siehe Anlage 4 ^t50q182 - A) Warm front. - B) Front aloft. - C) Cold front. - D) Occlusion. **Correct: C)** > **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. The symbol labeled (1) in figure MET-005 matches the cold front symbol. A warm front uses semicircles. An occlusion uses alternating triangles and semicircles. A front aloft is depicted differently and is less commonly shown on basic surface charts. ### Q183: In METAR code, which identifier denotes heavy rain? ^t50q183 - A) .+SHRA. - B) RA. - C) .+RA - D) SHRA **Correct: C)** > **Explanation:** In METAR codes, precipitation intensity is indicated by a '+' prefix (heavy) or '-' prefix (light); no prefix means moderate. Rain is coded 'RA'. Therefore heavy rain is '+RA' (written as '+RA' in the standard, shown in the options as '.+RA'). 'RA' alone (option B) means moderate rain. 'SHRA' (option D) means shower of rain (moderate). '+SHRA' (option A) means heavy shower of rain — a convective shower, not continuous heavy rain. ### Q184: During which stage of a thunderstorm do strong updrafts and downdrafts coexist? ^t50q184 - A) Thunderstorm stage. - B) Dissipating stage. - C) Mature stage. - D) Initial stage. **Correct: C)** > **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, which cut off the updraft supply and weaken the storm. 'Thunderstorm stage' (option A) is not a recognised meteorological term. ### Q185: Which conditions are most conducive to aircraft icing? ^t50q185 - A) Temperatures between +10° C and -30° C in the presence of hail - B) Temperatures between 0° C and -12° C with supercooled water droplets present - C) Temperatures between -20° C and -40° C within cirrus clouds containing ice crystals - D) Sub-zero temperatures with strong wind and cloudless skies **Correct: B)** > **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 in ice crystal form and causes much less accretion. Above 0°C, droplets are not supercooled and do not freeze on contact. Icing in clear air (option D) does not occur as there are no supercooled droplets. Cirrus (option C) contains ice crystals which do not adhere significantly. ### Q186: What is the primary hazard when approaching a valley airfield with strong winds aloft blowing perpendicular to the surrounding ridges? ^t50q186 - A) Heavy downdrafts beneath thunderstorm rainfall areas - B) Wind shear during descent, with possible 180° wind direction changes - C) Reduced visibility and potential loss of sight of the airfield on final - D) Formation of moderate to severe clear ice on all aircraft surfaces **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, creating sudden loss of airspeed or ground wind opposite to the upper-level flow. Reduced visibility (option C) is a secondary concern. Icing (option D) is unrelated to mountain wind shear. Heavy downdrafts in rainfall (option A) describes thunderstorm activity, not orographic flow. ### Q187: What are "blue thermals"? ^t50q187 - A) Turbulence in the vicinity of cumulonimbus clouds - B) Descending air found between cumulus clouds - C) Thermals that rise without producing any cumulus clouds - D) Thermals occurring when cumulus coverage is below 4/8 **Correct: C)** > **Explanation:** Blue thermals are thermals that extend to significant altitude but remain below the condensation level (dew point height), so no Cumulus clouds form — the sky appears clear (blue). They are invisible to glider pilots and require instruments or experience to exploit. Option D confuses thermals with cloud coverage statistics. Option B describes sink between Cu clouds. Option A describes clear-air turbulence (CAT) near thunderstorms, a different phenomenon. ### Q188: The expression "beginning of thermals" refers to the moment when thermal strength... ^t50q188 - A) Is sufficient for cross-country soaring with cumulus clouds marking the thermals. - B) Reaches at least 1200 m MSL and becomes usable for gliding. - C) Becomes sufficient for gliding and extends to at least 600 m AGL. - D) Reaches at least 600 m AGL and produces cumulus clouds. **Correct: C)** > **Explanation:** The 'beginning of thermals' (Thermikbeginn) is the moment when thermal lift becomes sufficiently strong and deep (reaching at least 600 m AGL) for a glider to sustain flight and gain height — this is the practical definition. It does not require Cu cloud formation (option A), nor does it specify a fixed MSL altitude (option B). Option D adds an unnecessary cloud formation criterion to what is fundamentally an altitude threshold. ### Q189: How is the "trigger temperature" defined? It is the temperature which... ^t50q189 - A) A thermal reaches during its ascent at the moment cumulus clouds begin forming. - B) Must be attained at ground level for cumulus clouds to develop from thermal convection. - C) Represents the maximum surface temperature achievable before a cumulus cloud evolves into a thunderstorm. - D) Represents the minimum surface temperature required for a cumulus to develop into a thunderstorm. **Correct: B)** > **Explanation:** The trigger temperature is the minimum ground temperature that must be reached before thermals are strong enough to carry air parcels to the condensation level and form Cumulus clouds. It is found on a tephigram or skew-T diagram by tracing the dry adiabatic lapse rate from the surface intersection until it meets the temperature profile. Options A and C misstate it as a temperature reached aloft or a threshold for thunderstorm formation. Option D describes thunderstorm formation, not Cu formation. ### Q190: In a weather briefing, what does the term "over-development" refer to? ^t50q190 - A) Transition from blue thermals to cloud-marked thermals during the afternoon - B) Spreading of cumulus clouds beneath an inversion layer - C) Vertical growth of cumulus clouds into rain-producing showers - D) Intensification of a thermal low into a storm depression **Correct: C)** > **Explanation:** Over-development (Überentwicklung) occurs when Cumulus clouds develop vertically beyond Cu congestus into rain-producing Cumulonimbus clouds, generating showers and thunderstorms. This typically happens in the afternoon when the atmosphere becomes increasingly unstable. Option A describes a change in thermal visibility. Option D refers to synoptic-scale deepening of depressions. Option B describes the spreading of Cu under an inversion (which is actually 'street' or 'cover' formation, a separate phenomenon). ### Q191: In gliding meteorology, what does "shielding" refer to? ^t50q191 - A) The anvil-shaped structure at the top of a thunderstorm cloud - B) Cumulus cloud coverage expressed in eighths of the sky - C) High or mid-level cloud layers that suppress thermal activity - D) Nimbostratus covering the windward slope of a mountain range **Correct: C)** > **Explanation:** Shielding (Abschirmung) refers to a layer of high or mid-level cloud (such as Cirrostratus, Altostratus, or Altocumulus) that intercepts solar radiation before it reaches the ground, thus reducing or suppressing the surface heating required for thermal development. Option D describes cloud cover on a windward mountain slope. Option A describes the anvil of a Cb, not shielding. Option B describes sky coverage in oktas, which is unrelated. ### Q192: What is the gaseous composition of dry air? ^t50q192 - A) Oxygen 21%, Nitrogen 78%, Noble gases / carbon dioxide 1% - B) Nitrogen 21%, Oxygen 78%, Noble gases / carbon dioxide 1% - C) Oxygen 21%, Water vapour 78%, Noble gases / carbon dioxide 1% - D) Oxygen 78%, Water vapour 21%, Nitrogen 1% **Correct: A)** > **Explanation:** Dry air is composed of approximately 78% nitrogen, 21% oxygen, and 1% argon and trace gases including carbon dioxide. This is the standard atmospheric composition. All other options incorrectly swap the proportions of nitrogen and oxygen or introduce water vapour as a major component. Water vapour is a variable constituent (0–4%) not included in the standard dry air composition. ### Q193: Under ISA conditions at mean sea level, what is the mass of one cubic metre of air? ^t50q193 - A) 12,25 kg - B) 0,01225 kg - C) 1,225 kg - D) 0,1225 kg **Correct: C)** > **Explanation:** At MSL under ISA conditions, the standard air density is 1.225 kg/m³. A cube with 1 m edges has a volume of 1 m³, so its mass is 1.225 kg. Option B (0.01225 kg) is off by a factor of 100, option D (0.1225 kg) by a factor of 10, and option A (12.25 kg) by a factor of 10 in the opposite direction. These represent common decimal-point errors. ### Q194: How is the tropopause defined? ^t50q194 - A) The altitude above which temperature begins to decrease. - B) The boundary between the mesosphere and the stratosphere. - C) The layer above the troposphere where temperature increases. - D) The boundary zone between the troposphere and the stratosphere. **Correct: D)** > **Explanation:** The tropopause is the boundary layer separating the troposphere (where temperature decreases with altitude) from the stratosphere (where temperature is initially constant and then increases due to ozone absorption). It is not the layer above the troposphere (option C), nor the height where temperature starts to decrease (option A — that is the surface of the troposphere). Option B confuses the tropopause with the stratopause. ### Q195: What characterises an inversion layer? ^t50q195 - A) A boundary zone separating two distinct atmospheric layers - B) An atmospheric layer where temperature falls with increasing altitude - C) An atmospheric layer where temperature remains constant with increasing altitude - D) An atmospheric layer where temperature rises with increasing altitude **Correct: D)** > **Explanation:** An inversion layer is an atmospheric layer in which temperature increases with increasing altitude, the reverse ('inversion') of the normal decrease. Inversions suppress vertical mixing and convection, trapping pollutants and inhibiting thermal development above them. Option B describes normal atmospheric conditions. Option C describes an isothermal layer. Option A describes a generic boundary without specifying the temperature gradient direction. ### Q196: What defines an isothermal layer? ^t50q196 - A) An atmospheric layer where temperature increases with height - B) A transition zone between two other atmospheric layers - C) An atmospheric layer where temperature decreases with height - D) An atmospheric layer where temperature stays constant with height **Correct: D)** > **Explanation:** An isothermal layer is one in which temperature remains constant with increasing altitude — neither increasing (inversion, option A) nor decreasing (normal lapse rate, option C). Isothermal conditions are found, for example, in the lower stratosphere. Option B describes a generic atmospheric boundary layer, not a layer of constant temperature. ### Q197: What fundamental force initiates wind? ^t50q197 - A) Thermal force - B) Coriolis force - C) Centrifugal force - D) Pressure gradient force **Correct: D)** > **Explanation:** Wind is caused by the pressure gradient force — air flows from areas of high pressure to areas of low pressure, and the greater the pressure difference over a given distance, the stronger the resulting wind. The Coriolis force (option B) deflects wind but does not create it. Centrifugal force (option C) is a secondary effect in curved flow. There is no meteorological force specifically called 'thermal force'; thermal differences drive pressure gradients, but the direct cause of wind is the pressure gradient itself. ### Q198: Under what conditions does Foehn typically develop? ^t50q198 - A) Stability, with extensive airflow forced over a mountain ridge. - B) Instability, with a high pressure area and calm wind. - C) Stability, with a high pressure area and calm wind. - D) Instability, with extensive airflow forced over a mountain ridge. **Correct: A)** > **Explanation:** Foehn develops when a stable airflow is forced over a mountain barrier. On the windward side, the air rises moist-adiabatically (condensation releasing latent heat), and on the lee side it descends dry-adiabatically, arriving warmer and drier than before ascent. Stability is necessary for the organised flow; instability would break the flow into convective cells. Calm high-pressure conditions (options B and C) do not provide the cross-mountain pressure gradient needed. Instability (option D) would prevent the laminar flow characteristic of Foehn. ### Q199: How is the "spread" (dew-point depression) defined? ^t50q199 - A) The maximum quantity of water vapour that air can hold. - B) The ratio of actual humidity to the maximum possible humidity. - C) The difference between the actual air temperature and the dew point. - D) The difference between the dew point and the condensation point. **Correct: C)** > **Explanation:** The spread (or dew-point spread) is the difference between the actual (dry-bulb) air temperature and the dew point temperature. A small spread indicates air close to saturation; when the spread reaches zero, condensation and fog or cloud formation occur. Option D is incorrect because dew point and condensation point are effectively the same. Option B describes relative humidity. Option A describes the saturation mixing ratio or absolute humidity capacity. ### Q200: During Foehn, what weather phenomenon designated by "2" should be expected on the lee side? See figure (MET-001). Siehe Anlage 1 ^t50q200 - A) Altocumulus Castellanus - B) Altocumulus lenticularis - C) Cumulonimbus - D) Cumulonimbus **Correct: B)** > **Explanation:** This question is identical in content to question 90. During Foehn, the descending and warming lee-side flow is stable and generates standing wave clouds. Altocumulus lenticularis forms in the crests of these mountain waves on the lee side. Cumulonimbus (options C and D) requires strong convective instability absent in Foehn descent. Altocumulus Castellanus (option A) indicates mid-level instability, not the stable wave motion of a Foehn situation.