Correct: B)
Explanation: The saturated (moist) adiabatic lapse rate (SALR, averaging about 0.6°C/100 m) is lower than the dry adiabatic lapse rate (DALR, 1.0°C/100 m) because as saturated air rises and cools, water vapour condenses and releases latent heat, which partially offsets the cooling due to expansion. This means saturated air cools more slowly per unit of altitude gained. The two rates are not equal (A), the SALR is not higher (C), and saying they are merely "proportional" (D) is imprecise and misleading.
Correct: C)
Explanation: The dry adiabatic lapse rate (DALR) is exactly 1.0°C per 100 m (or approximately 3°C per 1000 ft). This is the rate at which an unsaturated air parcel cools when rising (or warms when descending) purely due to adiabatic expansion or compression. Option A (0.6°C/100 m) is approximately the saturated adiabatic lapse rate. Option B (0.65°C/100 m) is the standard atmosphere environmental lapse rate. Option D (2°/1000 ft) converts to about 0.66°C/100 m, which does not match the DALR.
Correct: C)
Explanation: Conditional instability means the atmosphere is stable for unsaturated air but becomes unstable once air parcels are lifted to saturation. When triggered — by surface heating, orographic lift, or frontal forcing — this instability produces vigorous convection: towering cumulus and cumulonimbus clouds with isolated showers and thunderstorms. Clear skies (A) indicate absolute stability or dry conditions. Layered clouds with prolonged rain (B) characterise absolutely stable (stratiform) weather. Shallow mid-level cumulus (D) indicates limited instability insufficient for significant vertical development.
Correct: C)
Explanation: The figure MET-004 shows thin, wispy, high-altitude clouds with a delicate fibrous or streaky structure — the defining visual characteristics of cirrus clouds. Cirrus forms above approximately 6,000 m (FL200) and consists entirely of ice crystals, which produce its distinctive silky or hair-like appearance. Stratus (A) is a grey, featureless layer cloud at low altitude. Cumulus (B) has a well-defined, puffy vertical structure. Altocumulus (D) appears as white or grey patches or layers of rounded masses at mid-level.
Correct: C)
Explanation: Medium to large precipitation particles (raindrops, hailstones) need time to grow by collision-coalescence or the Bergeron ice-crystal process, and strong updrafts keep droplets and ice crystals suspended in the cloud long enough for this growth to occur. Without sufficient updraft strength, particles fall out before reaching significant size. An inversion layer (A) suppresses cloud growth and precipitation. A high cloud base (B) reduces available cloud depth for particle growth. Strong horizontal wind (D) does not contribute to the vertical suspension needed for particle growth.
Correct: B)
Explanation: On standard synoptic weather charts, a warm front is depicted as a line with semicircles pointing in the direction of movement (into the colder air mass). The referenced figure MET-005 shows symbol (2) matching this convention — semicircles on one side of the frontal line. A cold front (A) uses triangular barbs pointing in the direction of advance. An occlusion (D) uses alternating triangles and semicircles on the same side. A front aloft (C) is marked with a different symbology indicating the front does not reach the surface.
Correct: C)
Explanation: The warm sector lies between the warm front and the cold front, containing the warmest, most homogeneous air. During summer, this air mass typically offers moderate to good visibility with scattered or broken cloud layers — flyable VFR conditions. Visibility below 1000 m with ground-covering cloud (A) is more typical of winter fog or orographic stratus. Heavy showers and thunderstorms (D) are characteristic of the cold front itself, not the warm sector. Few isolated high clouds (B) describe pre-frontal conditions well ahead of the system.
Correct: B)
Explanation: After a cold front passes, cold, clean polar air replaces the warm sector. This unstable air mass produces excellent visibility between showers, with convective cumulus clouds developing from surface heating and occasional rain or snow showers from cumulus congestus. Option A describes warm front approach conditions (lowering bases, continuous rain). Option C understates the convective activity typical of post-frontal polar air. Option D describes poor visibility with stratus, which is more typical of the cold sector of a warm occlusion, not the fresh polar air behind a cold front.
Correct: D)
Explanation: A polar front low (extratropical cyclone) is steered by the upper-level airflow, which is closely approximated by the direction of the isobars in the warm sector — the warm sector wind effectively carries the entire system along. This is a more reliable steering rule than fixed seasonal directions. Option A wrongly states southward movement. Options B and C propose rigid seasonal rules that oversimplify the highly variable tracks of mid-latitude cyclones across Europe.
Correct: A)
Explanation: The classic pressure trace of a passing polar front low follows three phases: pressure falls as the warm front approaches (the low draws nearer), pressure holds relatively steady in the warm sector between the two fronts, and pressure rises sharply after the cold front passes as cold, dense air replaces the warm sector. Option B wrongly has pressure rising ahead of the warm front. Option C has pressure falling behind the cold front, contradicting the arrival of dense cold air. Option D reverses the entire pattern.
Correct: D)
Explanation: In the Northern Hemisphere, as a typical polar front low passes, wind veers (shifts clockwise) at both frontal passages. At the warm front, wind veers from southeast to south or southwest. At the cold front, it veers again from southwest to west or northwest. This consistent clockwise shift indicates the low is passing to the north of the observer, which is the normal track for lows crossing Central Europe. Backing (A, B, C) would indicate the low passing to the south — an uncommon trajectory.
Correct: A)
Explanation: When cold air intrudes into the upper troposphere, it reduces the thickness of the atmospheric column (cold air is denser and occupies less vertical space), causing the heights of upper pressure surfaces to drop. This creates an upper-level low or trough. These cold-pool lows aloft are potent triggers for convective instability and often initiate cyclogenesis at the surface. An upper high (B) would form from warm-air advection, not cold intrusion. Oscillating pressure (C) and a large surface low (D) are not the direct or primary consequence of upper-level cold intrusion.
Correct: C)
Explanation: Cold air advecting into the upper troposphere steepens the lapse rate (cold air aloft over relatively warmer air below), producing conditional or even absolute instability. This destabilisation triggers convection, generating showers and thunderstorms — especially when combined with surface moisture and daytime heating. Stabilisation and settled weather (A) and calm conditions (D) are the opposite of what cold upper-air intrusion produces. Frontal weather (B) requires surface air-mass boundaries, which are not a direct result of upper-tropospheric cooling.
Correct: D)
Explanation: Cold air is denser than warm air, so a cold air column has less vertical distance (decreased spacing) between any two pressure surfaces. Because the column is compressed, the upper pressure surfaces lie at lower geometric heights, which is identified as low pressure aloft on hypsometric charts. This is why upper-level lows are always associated with cold-core air masses. Warm air produces the opposite: increased spacing and raised heights (high pressure aloft), as described in options A and C.
Correct: B)
Explanation: In summer, anticyclones bring subsiding air that warms adiabatically, suppressing deep convection and producing clear to partly cloudy skies with perhaps a few fair-weather cumulus (Cu humilis) from daytime thermal heating. The overall character is settled, warm, and dry. Squall lines and thunderstorms (A) require convective instability not present in a well-established high. Frontal passages (C) are features of low-pressure troughs. Widespread high fog (D) is a winter high-pressure phenomenon caused by temperature inversions trapping cold moist air.
Correct: C)
Explanation: On the windward (Stau) side during Foehn, moist air is forced to rise over the mountain barrier, cooling adiabatically and producing dense layered clouds (stratus, nimbostratus), obscured mountain peaks, poor visibility, and moderate to heavy orographic precipitation. Option D describes the lee-side Foehn effect — warm, dry, gusty descending wind — which is the opposite side of the mountains. Option A describes convective (unstable) weather, not the organised forced ascent of a Foehn pattern. Option B describes stagnant anticyclonic conditions, not active orographic lifting.
Correct: B)
Explanation: Weather radar detects precipitation directly by measuring the intensity of microwave energy backscattered from raindrops, snowflakes, and hail. Radar imagery shows the precise location, extent, and intensity of precipitation areas in near-real-time. A satellite picture (D) shows cloud cover but cannot directly distinguish precipitating from non-precipitating clouds. A wind chart (A) displays wind patterns only. A GAFOR (C) is a coded route forecast for general aviation that categorises flying conditions but does not depict precipitation areas graphically.
Correct: D)
Explanation: An inversion is a layer of the atmosphere where temperature increases with altitude, which is the reverse ("inversion") of the normal tropospheric lapse rate. Inversions are extremely stable and act as lids that suppress convection, trap pollution, and limit thermal development for glider pilots. Option B describes an isothermal layer (constant temperature). Option C describes the normal lapse rate. Option A is incorrect because atmospheric pressure always decreases with height, regardless of the temperature profile.
Correct: C)
Explanation: Radiation fog requires the ground to radiate longwave heat to space, cooling the surface air to the dew point. An overcast cloud layer acts as a blanket, absorbing and re-emitting radiation back toward the ground, preventing the surface from cooling sufficiently. Therefore, overcast cloud cover prevents radiation fog formation. A clear night (A), low spread (B), and calm wind (D) all favour fog formation — they are prerequisites, not preventative conditions.
Correct: C)
Explanation: An occluded front is depicted on synoptic charts by a line combining both the cold front triangles and the warm front semicircles on the same side, representing the merger of the two fronts when the faster-moving cold front overtakes the warm front. Symbol (3) in figure MET-005 shows this combined symbology, identifying it as an occlusion. A warm front (A) uses only semicircles. A cold front (B) uses only triangles. A front aloft (D) has a distinct marking indicating the frontal surface does not reach the ground.
Correct: C)
Explanation: A stationary front is a boundary between two contrasting air masses — here polar and subtropical — that is not moving significantly in either direction. Neither the cold air nor the warm air is advancing. A cold front (D) is specifically an advancing cold air mass pushing warm air aside. A warm front (A) is advancing warm air overriding cold air. An occluded front (B) results from a cold front overtaking a warm front within a mature cyclone — it involves merging fronts, not stationary boundaries.
Correct: B)
Explanation: An active shower near an airfield indicates ongoing convective downdrafts and outflow boundaries that create severe, rapidly changing low-level wind shear — a critical hazard during takeoff and landing. The gust front from a nearby shower can change wind direction and speed dramatically within seconds. Cross-country flying below moderate Cu (A) involves normal soaring conditions. Thirty minutes after a shower (C), conditions have typically stabilised. Cirrus ahead of a warm front (D) is an upper-level indicator without immediate low-level shear implications.
Correct: C)
Explanation: Haze (HZ) is caused by dry particulates — dust, smoke, industrial pollution, and fine sand — suspended in the atmosphere. Because these particles are not moisture-dependent, haze persists regardless of temperature changes. Mist (A), fog patches (B), and radiation fog (D) are all formed by water droplet suspension and are highly sensitive to temperature: warming evaporates the droplets and improves visibility, while cooling promotes further condensation and worsens it.
Correct: C)
Explanation: In METAR format, the descriptor "SH" (shower) is combined with the precipitation type "RA" (rain) to form "SHRA," which denotes moderate showers of rain. No intensity prefix means moderate. "+RA" (B) indicates heavy continuous rain, not a shower. "TS" (A) denotes a thunderstorm without specifying precipitation type. "+TSRA" (D) indicates a heavy thunderstorm with rain — a more severe phenomenon than a simple rain shower.
Correct: B)
Explanation: SIGMET (Significant Meteorological Information) warnings are issued for Flight Information Regions (FIRs) and Upper Information Regions (UIRs), which are standardised ICAO airspace blocks managed by specific ATC authorities. They warn of hazardous weather phenomena (severe turbulence, icing, volcanic ash, thunderstorms) within these defined airspace volumes. SIGMETs are not issued for individual airports (A) — those use AIRMETs or aerodrome warnings. They are not route-specific (C) or country-specific (D), as a single country may contain multiple FIRs.
