# Meteorology

> Source: QuizVDS.it (EASA ECQB-SPL) | 50 questions
> Free practice: https://quizvds.it/en-en/quiz/spl-en

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### Q1: What clouds and weather may result from an humid and instable air mass, that is pushed against a chain of mountains by the predominant wind and forced to rise? ^q1
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^q1)*
- A) Embedded CB with thunderstorms and showers of hail and/or rain.
- B) Smooth, unstructured NS cloud with light drizzle or snow (during winter).
- C) Thin Altostratus and Cirrostratus clouds with light and steady precipitation.
- D) Overcast low stratus (high fog) with no precipitation.
**Correct: A)**

> **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.

### Q2: What type of fog emerges if humid and almost saturated air, is forced to rise upslope of hills or shallow mountains by the prevailling wind? ^q2
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^q2)*
- A) Advection fog
- B) Steaming fog
- C) Radiation fog
- D) Orographic fog
**Correct: D)**

> **Explanation:** Orographic fog forms when wind-driven humid air is mechanically lifted along a slope, cooling adiabatically until it reaches the dew point. Radiation fog requires calm nights with radiative ground cooling, advection fog forms when warm moist air moves over a cold surface, and steaming fog (Arctic sea smoke) occurs when cold air passes over warm water — none of these involve slope-forced lifting.

### Q3: What phenomenon is referred to as "blue thermals"? ^q3
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^q3)*
- A) Thermals with less than 4/8 Cu coverage
- B) Descending air between Cumulus clouds
- C) Turbulence in the vicinity of Cumulonimbus clouds
- D) Thermals without formation of Cu clouds
**Correct: D)**

> **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.

### Q4: The term "beginning of thermals" refers to the moment when thermal intensity... ^q4
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^q4)*
- A) Becomes usable for cross-country gliding by formation of Cu clouds.
- B) Becomes usable for gliding and reaches up to 1200 m MSL.
- C) Reaches up to 600 m AGL and forms Cumulus clouds.
- D) Becomes usable for gliding and reaches up to 600 m AGL.
**Correct: D)**

> **Explanation:** Thermal activity is considered to have "begun" when thermals are strong enough to support gliding and extend to at least 600 m AGL — sufficient altitude to work the lift. Below this height, thermals may exist but are too shallow to be safely exploited by a glider. Cloud formation is not a prerequisite; blue thermals (see Q3) can also mark the beginning of usable thermal activity.

### Q5: The term "trigger temperature" is defined as the temperature which... ^q5
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^q5)*
- A) Is reached by a thermal lift during ascend when formation of Cumulus clouds begins.
- B) Is the maximum temperature at ground level that can be reached without formation of a thunderstorm from a Cumulus cloud.
- C) Is the minimum temperature at ground level that has to be reached so formation of a thunderstorm from a Cumulus cloud can occur.
- D) Must be obtained at ground level so Cumulus clouds can be formed by thermal lifts.
**Correct: D)**

> **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.

### Q6: What situation is called "over-development" in a weather report? ^q6
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^q6)*
- A) Change from blue thermals to cloudy thermals during the afternoon
- B) Development of a thermal low to a storm depression
- C) Vertical development of Cumulus clouds to rain showers
- D) Widespreading of Cumulus clouds below an inversion layer
**Correct: C)**

> **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.

### Q7: The gliding weather report states environmental instability. At morning, dew covers gras and no thermals are presently active. What development can be expected for thermal activity? ^q7
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^q7)*
- A) Formation of dew prevents all thermal activity during the following day
- B) With ongoing insolation and ground warming, thermal lifting is likely to begin
- C) Environmental instability prevents air from being lifted and no thermals will be generated
- D) After sunset and formation of a ground-level inversion thermal activity is likely to begin
**Correct: B)**

> **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.

### Q8: What change in thermal activity may be expected with cirrus clouds coming up from one direction and becoming more dense, blocking the sun? ^q8
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^q8)*
- A) Cirrus clouds may intensify insolation and improve thermal activity
- B) Cirrus clouds indicate an high-level inversion with thermal activity ongoing up to that level
- C) Cirrus clouds prevent insolation and impair thermal activity.
- D) Cirrus clouds indicate instability and beginning of over-development
**Correct: C)**

> **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.

### Q9: What situation is referred to as "shielding"? ^q9
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^q9)*
- A) Ns clouds, covering the windward side of a mountain range
- B) High or mid-level cloud layers, impairing thermal activity
- C) Anvil-like structure at the upper levels of a thunderstorm cloud
- D) Coverage of Cumulus clouds, stated as part of eights of the sky
**Correct: B)**

> **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 due to cloud cover above the expected thermal layer.

### Q10: While planning a 500 km triangle flight, there is a squall line 100 km west of the departure airfield, extending from north to south, moving east. Concerning the weather situation, what decision would be recommendable? ^q10
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^q10)*
- A) To change plans and start the triangle heading east
- B) To postpone the flight to another day
- C) To plan the flight below cloud base of the thunderstorms
- D) During flight, to look for spacing between thunderstorms
**Correct: B)**

> **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.

### Q11: What is the gas composition of "air"? ^q11
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^q11)*
- A) Oxygen 78 % Water vapour 21 % Nitrogen 1 %
- B) Oxygen 21 % Nitrogen 78 % Noble gases / carbon dioxide 1 %
- C) Oxygen 21 % Water vapour 78 % Noble gases / carbon dioxide 1 %
- D) Nitrogen 21 % Oxygen 78 % Noble gases / carbon dioxide 1 %
**Correct: B)**

> **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.

### Q12: Weather phenomena are most common to be found in which atmospheric layer? ^q12
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^q12)*
- A) Tropopause
- B) Stratosphere
- C) Thermosphere
- D) Troposphere
**Correct: D)**

> **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.

### Q13: What is the mass of a "cube of air" with the edges 1 m long, at MSL according ISA? ^q13
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^q13)*
- A) 0,01225 kg
- B) 0,1225 kg
- C) 12,25 kg
- D) 1,225 kg
**Correct: D)**

> **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.

### Q14: At what rate does the temperature change with increasing height according to ISA (ICAO Standard Atmosphere) within the troposphere? ^q14
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^q14)*
- A) Decreases by 2° C / 1000 ft
- B) Increases by 2° C / 100 m
- C) Decreases by 2° C / 100 m
- D) Increases by 2° C / 1000 ft
**Correct: A)**

> **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.

### Q15: What is the mean height of the tropopause according to ISA (ICAO Standard Atmosphere)? ^q15
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^q15)*
- A) 11000 f
- B) 11000 m
- C) 18000 ft
- D) 36000 m
**Correct: B)**

> **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.

### Q16: The term "tropopause" is defined as... ^q16
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^q16)*
- A) The layer above the troposphere showing an increasing temperature.
- B) The height above which the temperature starts to decrease.
- C) The boundary area between the troposphere and the stratosphere.
- D) The boundary area between the mesosphere and the stratosphere.
**Correct: C)**

> **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.

### Q17: Temperatures will be given by meteorological aviation services in Europe in which unit? ^q17
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^q17)*
- A) Gpdam
- B) Kelvin
- C) Degrees Centigrade (° C)
- D) Degrees Fahrenheit
**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.

### Q18: What is meant by "inversion layer"? ^q18
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^q18)*
- A) An atmospheric layer where temperature increases with increasing height
- B) An atmospheric layer where temperature decreases with increasing height
- C) An atmospheric layer with constant temperature with increasing height
- D) A boundary area between two other layers within the atmosphere
**Correct: A)**

> **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.

### Q19: What is meant by "isothermal layer"? ^q19
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^q19)*
- A) An atmospheric layer where temperature decreases with increasing height
- B) An atmospheric layer with constant temperature with increasing height
- C) A boundary area between two other layers within the atmosphere
- D) An atmospheric layer where temperature increases with increasing height
**Correct: B)**

> **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.

### Q20: The temperature lapse rate with increasing height within the troposphere according ISA is... ^q20
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^q20)*
- A) 1° C / 100 m.
- B) 0,6° C / 100 m.
- C) 0,65° C / 100 m.
- D) 3° C / 100 m.
**Correct: C)**

> **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.

### Q21: Which process may result in an inversion layer at about 5000 ft (1500 m) height? ^q21
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^q21)*
- A) Ground cooling by radiation during the night
- B) Intensive sunlight insolation during a warm summer day
- C) Advection of cool air in the upper troposphere
- D) Widespread descending air within a high pressure area
**Correct: D)**

> **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.

### Q22: An inversion layer close to the ground can be caused by... ^q22
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^q22)*
- A) Thickening of clouds in medium layers.
- B) Large-scale lifting of air
- C) Intensifying and gusting winds.
- D) Ground cooling during the night.
**Correct: D)**

> **Explanation:** Radiation inversion forms on calm, clear nights when the ground radiates heat into space and cools rapidly. The air in contact with the ground also cools, while air a few hundred metres above remains warmer — creating a temperature inversion near the surface. This type of inversion is common in anticyclonic conditions and often produces radiation fog or low stratus in the morning, which burns off as the sun heats the ground.

### Q23: What is the ISA standard pressure at FL 180 (5500 m)? ^q23
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^q23)*
- A) 300 hPa
- B) 250 hPa
- C) 1013.25 hPa
- D) 500 hPa
**Correct: D)**

> **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.

### Q24: Which processes result in decreasing air density? ^q24
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^q24)*
- A) Decreasing temperature, increasing pressure
- B) Increasing temperature, increasing pressure
- C) Increasing temperature, decreasing pressure
- D) Decreasing temperature, decreasing pressure
**Correct: C)**

> **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.

### Q25: The pressure at MSL in ISA conditions is... ^q25
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^q25)*
- A) 1013.25 hPa.
- B) 113.25 hPa.
- C) 15 hPa.
- D) 1123 hPa.
**Correct: A)**

> **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.

### Q26: The height of the tropopause of the International Standard Atmosphere (ISA) is at... ^q26
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^q26)*
- A) 36000 ft.
- B) 5500 ft
- C) 48000 ft.
- D) 11000 ft.
**Correct: A)**

> **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 Q15 which asks in metres — both questions test knowledge of the same value expressed in different units.

### Q27: The barometric altimeter indicates height above... ^q27
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^q27)*
- A) Mean sea level.
- B) A selected reference pressure level.
- C) Ground.
- D) Standard pressure 1013.25 hPa.
**Correct: B)**

> **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.

### Q28: The altimeter can be checked on the ground by setting... ^q28
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^q28)*
- A) QFF and comparing the indication with the airfield elevation.
- B) QFE and comparing the indication with the airfield elevation.
- C) QNH and comparing the indication with the airfield elevation.
- D) QNE and checking that the indication shows zero on the ground.
**Correct: C)**

> **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.

### Q29: The barometric altimeter with QFE setting indicates... ^q29
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^q29)*
- A) True altitude above MSL.
- B) Height above the pressure level at airfield elevation.
- C) Height above MSL.
- D) Height above standard pressure 1013.25 hPa.
**Correct: B)**

> **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.

### Q30: The barometric altimeter with QNH setting indicates... ^q30
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^q30)*
- A) True altitude above MSL.
- B) Height above MSL
- C) Height above the pressure level at airfield elevation.
- D) Height above standard pressure 1013.25 hPa.
**Correct: B)**

> **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" (answer A) accounts for actual temperature deviations from ISA — QNH gives indicated altitude, which may differ from true altitude in non-ISA conditions.

### Q31: How can wind speed and wind direction be derived from surface weather charts? ^q31
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^q31)*
- A) By alignment and distance of isobaric lines
- B) By annotations from the text part of the chart
- C) By alignment and distance of hypsometric lines
- D) By alignment of lines of warm- and cold fronts.
**Correct: A)**

> **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).

### Q32: Which force causes "wind"? ^q32
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^q32)*
- A) Centrifugal force
- B) Pressure gradient force
- C) Coriolis force
- D) Thermal force
**Correct: B)**

> **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.

### Q33: Above the friction layer, with a prevailing pressure gradient, the wind direction is... ^q33
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^q33)*
- A) At an angle of 30° to the isobars towards low pressure.
- B) Perpendicular to the isobars.
- C) Parallel to the isobars.
- D) Perpendicular to the isohypses.
**Correct: C)**

> **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.

### Q34: Which of the stated surfaces will reduce the wind speed most due to ground friction? ^q34
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^q34)*
- A) Flat land, lots of vegetation cover
- B) Flat land, deserted land, no vegetation
- C) Oceanic areas
- D) Mountainous areas, vegetation cover
**Correct: D)**

> **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.

### Q35: The movement of air flowing together is called... ^q35
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^q35)*
- A) Convergence.
- B) Subsidence.
- C) Soncordence
- D) Divergence.
**Correct: A)**

> **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.

### Q36: The movement of air flowing apart is called... ^q36
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^q36)*
- A) Convergence.
- B) Concordence.
- C) Subsidence.
- D) Divergence.
**Correct: D)**

> **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.

### Q37: What weather development will result from convergence at ground level? ^q37
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^q37)*
- A) Ascending air and cloud formation
- B) Descending air and cloud dissipation
- C) Ascending air and cloud dissipation
- D) Descending air and cloud formation
**Correct: A)**

> **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.

### Q38: When air masses meet each other head on, how is this referred to and what air movements will follow? ^q38
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^q38)*
- A) Convergence resulting in air being lifted
- B) Divergence resulting in air being lifted
- C) Divergence resulting in sinking air
- D) Divergence resulting in sinking air
**Correct: A)**

> **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.

### Q39: What are the air masses that Central Europe is mainly influenced by? ^q39
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^q39)*
- A) Arctic and polar cold air
- B) Tropical and arctic cold air
- C) Equatorial and tropical warm air
- D) Polar cold air and tropical warm air
**Correct: D)**

> **Explanation:** Central Europe sits in the mid-latitude westerly belt between the polar front (cold polar air from the north) and subtropical high pressure (warm tropical air from the south). The interaction between these two contrasting air masses creates the characteristic mid-latitude cyclone (depression) weather of Central Europe: frontal systems, rapidly changing weather, and the full range of cloud types and precipitation. This dynamic contrast also drives the polar jet stream overhead.

### Q40: With regard to global circulation within the atmosphere, where does polar cold air meets subtropical warm air? ^q40
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^q40)*
- A) At the equator
- B) At the subtropical high pressure belt
- C) At the polar front
- D) At the geographic poles
**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.

### Q41: "Foehn" conditions usually develop with... ^q41
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^q41)*
- A) Instability, high pressure area with calm wind.
- B) Stability, high pressure area with calm wind.
- C) Stability, widespread air blown against a mountain ridge.
- D) Instability, widespread air blown against a mountain ridge.
**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 (SALR ~0.6°C/100 m) after reaching the dew point, precipitating moisture. On the lee side, dry air descends at the Dry Adiabatic Lapse Rate (DALR ~1°C/100 m), arriving warmer and drier than it started — the Foehn effect.

### Q42: What type of turbulence is typically found close to the ground on the lee side during Foehn conditions? ^q42
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^q42)*
- A) Clear-air turbulence (CAT)
- B) Inversion turbulence
- C) Turbulence in rotors
- D) Thermal turbulence
**Correct: C)**

> **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. Lenticular clouds (altocumulus lenticularis) mark wave crests above, while rotor clouds (roll clouds) mark the rotor zone near the surface.

### Q43: Light turbulence always has to be expected... ^q43
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^q43)*
- A) Above cumulus clouds due to thermal convection.
- B) Below stratiform clouds in medium layers.
- C) When entering inversions.
- D) Below cumulus clouds due to thermal convection.
**Correct: D)**

> **Explanation:** Cumulus clouds are the visible tops of thermal columns. The sub-cloud layer beneath them contains active thermals (updraughts) and compensating downdraughts between them, creating light to moderate turbulence from convective mixing. This is the normal turbulent environment of thermal soaring. Above cumulus tops the air is generally smoother (outside the cloud); stratiform clouds have minimal convective turbulence unless embedded CBs are present.

### Q44: Moderate to severe turbulence has to be expected... ^q44
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^q44)*
- A) Below thick cloud layers on the windward side of a mountain range.
- B) Overhead unbroken cloud layers.
- C) On the lee side of a mountain range when rotor clouds are present.
- D) With the appearance of extended low stratus clouds (high fog).
**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. Experienced wave pilots avoid or transit the rotor zone quickly with sufficient airspeed. The windward side of mountains typically has orographic cloud and steady lift, not severe turbulence.

### Q45: Which answer contains every state of water found in the atmosphere? ^q45
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^q45)*
- A) Liquid, solid, and gaseous
- B) Liquid
- C) Gaseous and liquid
- D) Liquid and solid
**Correct: A)**

> **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.

### Q46: How do dew point and relative humidity change with decreasing temperature? ^q46
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^q46)*
- A) Dew point decreases, relative humidity increases
- B) Dew point remains constant, relative humidity increases
- C) Dew point increases, relative humidity decreases
- D) Dew point remains constant, relative humidity decreases
**Correct: B)**

> **Explanation:** The dew point is the temperature to which air must be cooled (at constant pressure and moisture content) for saturation to occur. It is a measure of the absolute moisture content and remains constant as temperature changes (assuming no moisture is added or removed). However, relative humidity — the ratio of actual vapour pressure to saturation vapour pressure — increases as temperature falls, because the saturation vapour pressure decreases with temperature. When temperature equals the dew point, relative humidity reaches 100% and condensation begins.

### Q47: How do spread and relative humidity change with increasing temperature? ^q47
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^q47)*
- A) Spread remains constant, relative humidity increases
- B) Spread remains constant, relative humidity decreases
- C) Spread increases, relative humidity decreases
- D) Spread increases, relative humidity increases
**Correct: C)**

> **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 (high cloud base). A small spread (near zero) indicates saturated or near-saturated conditions, with fog or low cloud likely.

### Q48: The "spread" is defined as... ^q48
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^q48)*
- A) Difference between actual temperature and dew point.
- B) Difference between dew point and condensation point.
- C) Relation of actual to maximum possible humidity of air
- D) Maximum amount of water vapour that can be contained in air.
**Correct: A)**

> **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.

### Q49: With other factors remaining constant, decreasing temperature results in... ^q49
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^q49)*
- A) Decreasing spread and increasing relative humidity.
- B) Increasing spread and increasing relative humidity.
- C) Decreasing spread and decreasing relative humidity.
- D) Increasing spread and decreasing relative humidity.
**Correct: A)**

> **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).

### Q50: What process causes latent heat being released into the upper troposphere? ^q50
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^q50)*
- A) Cloud forming due to condensation
- B) Descending air across widespread areas
- C) Evaporation over widespread water areas
- D) Stabilisation of inflowing air masses
**Correct: A)**

> **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).

## BAZL/OFAC — Series 1 Questions

### BAZL Br.50 Q10 : Which of these clouds presents the greatest danger to air navigation? ^bazl_50_10

> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_50_10)*
> *Source : BAZL/OFAC Série 1 - Branches Communes*

- A) Cirrostratus
- B) Cirrocumulus
- C) Cumulonimbus
- D) Altocumulus

**Correct : C)**

> **Explanation:** The CB (cumulonimbus) is the most dangerous cloud: severe turbulence, lightning, hail, wind shear, icing.

### BAZL Br.50 Q19 : In which situation will the tendency for thunderstorms be most pronounced? ^bazl_50_19

> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_50_19)*
> *Source : BAZL/OFAC Série 1 - Branches Communes*

- A) Slack pressure gradient situation, significant cooling of the lower air layers, high air humidity.
- B) High pressure situation, significant warming of the lower air layers, low air humidity.
- C) Slack pressure gradient situation, significant warming of the lower air layers, high air humidity.
- D) Slack pressure gradient situation, significant warming of the upper air layers, high air humidity.

**Correct : C)**

> **Explanation:** Thunderstorms = slack pressure gradient (low pressure gradient) + strong surface heating (instability) + high humidity.

### BAZL Br.50 Q11 : Due to fine suspended water droplets, visibility at an aerodrome is only 1.5 km up to 1000 ft AGL. What is the meteorological phenomenon causing this visibility reduction? ^bazl_50_11

> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_50_11)*
> *Source : BAZL/OFAC Série 1 - Branches Communes*

- A) Mist (BR).
- B) Haze (HZ).
- C) Shallow fog (MIFG).
- D) Widespread dust (DU).

**Correct : A)**

> **Explanation:** Visibility 1–5 km with water droplets = mist (BR). Fog = visibility < 1 km.

### BAZL Br.50 Q12 : Which of the following situations most favours the formation of radiation fog? ^bazl_50_12

> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_50_12)*
> *Source : BAZL/OFAC Série 1 - Branches Communes*

- A) 15 kt / Clear sky / 16°C / Dew point 15°C
- B) 2 kt / Scattered cloud / 7°C / Dew point 6°C
- C) 2 kt / Clear sky / -3°C / Dew point -20°C
- D) 15 kt / Overcast / 13°C / Dew point 12°C

**Correct : B)**

> **Explanation:** Radiation fog: light wind (2 kt), small temperature/dew point spread (1°C), some cloud acceptable. Option (C) has too large a temp/dew point spread.

### BAZL Br.50 Q1 : The temperature recorded at Samedan airport (LSZS, AD elevation 5600 ft) is +5°C. What will the approximate temperature be at 8600 ft altitude directly above the airport? (Assume ISA lapse rate) ^bazl_50_1

> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_50_1)*
> *Source : BAZL/OFAC Série 1 - Branches Communes*

- A) -1°C
- B) +11°C
- C) -6°C
- D) +5°C

**Correct : A)**

> **Explanation:** ISA lapse rate = -2°C/1000 ft. Difference: 8600 - 5600 = 3000 ft. Temperature: 5°C - (3 × 2) = -1°C.

### BAZL Br.50 Q2 : The QFE of an aerodrome (AD elevation 3500 ft) corresponds to: ^bazl_50_2

> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_50_2)*
> *Source : BAZL/OFAC Série 1 - Branches Communes*

- A) The instantaneous pressure at the measurement station level reduced to sea level taking into account the ISA temperature lapse rate.
- B) The instantaneous pressure at the measurement station level reduced to sea level taking into account the actual temperature profile.
- C) The instantaneous pressure at the measurement station level.
- D) The instantaneous pressure at sea level.

**Correct : C)**

> **Explanation:** QFE = atmospheric pressure measured at aerodrome level (station). The altimeter reads 0 on the ground.

### BAZL Br.50 Q6 : What does the following symbol mean? (Arrow with one long barb and one short barb) ^bazl_50_6

> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_50_6)*
> *Source : BAZL/OFAC Série 1 - Branches Communes*
> **Wind barb symbol:**
> ![[figures/bazl_50_q06_wind_barb.png]]
> *Wind from the north-east (~045°), 15 knots (1 long barb = 10 kt + 1 short barb = 5 kt)*

- A) Wind from SW, 30 knots.
- B) Wind from SW, 15 knots.
- C) Wind from NE, 15 knots.
- D) Wind from NE, 30 knots.

**Correct : C)**

> **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.

### BAZL Br.50 Q3 : What are the wind speed and direction in the following METAR? LSZB 131220Z 28015G25KT 9999 SCT035 BKN075 10/06 Q1018 NOSIG= ^bazl_50_3

> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_50_3)*
> *Source : BAZL/OFAC Série 1 - Branches Communes*

- A) Wind from WNW, 15 knots, direction varying between WNW and WSW.
- B) Wind from WNW, 25 knots, direction varying between WNW and SSE.
- C) Wind from ESE, 15 knots, gusting to 25 knots.
- D) Wind from WNW, 15 knots, gusting to 25 knots.

**Correct : D)**

> **Explanation:** 280° = WNW, 15 kt mean, G25 = gusts to 25 kt.

### BAZL Br.50 Q9 : In Switzerland, cloud base in a METAR is given in... ^bazl_50_9

> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_50_9)*
> *Source : BAZL/OFAC Série 1 - Branches Communes*

- A) ...metres above aerodrome level.
- B) ...feet above sea level.
- C) ...feet above aerodrome level.
- D) ...metres above sea level.

**Correct : C)**

> **Explanation:** In a METAR, cloud base is given in feet AGL (above aerodrome level).

### BAZL Br.50 Q5 : You are flying at very high altitude (northern hemisphere) and consistently have a crosswind from the left. You conclude that: ^bazl_50_5

> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_50_5)*
> *Source : BAZL/OFAC Série 1 - Branches Communes*

- A) A high-pressure area is to the left of your track, a low-pressure area to the right.
- B) A high-pressure area is to the right of your track, a low-pressure area to the left.
- C) There is a high-pressure area ahead of you and a low-pressure area behind you.
- D) There is a low-pressure area ahead of you and a high-pressure area behind you.

**Correct : B)**

> **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.

### BAZL Br.50 Q15 : What will be the probable change in atmospheric pressure at point C in the coming hours? (Synoptic chart with depression and fronts) ^bazl_50_15

> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_50_15)*
> *Source : BAZL/OFAC Série 1 - Branches Communes*
> **Synoptic chart:**
> ![[figures/bazl_50_q15_synoptic_fronts.png]]
> *T = depression centre. A = warm sector (between warm front and cold front). B = behind the cold front (cold air mass). C = ahead of the warm front (cool air mass).*
> *Cold front: blue triangles. Warm front: red semicircles.*

- A) Pressure will undergo rapid and regular variations.
- B) Pressure will rise.
- C) No notable variation.
- D) Pressure will fall.

**Correct : D)**

> **Explanation:** Point C is located ahead of the approaching depression/front → pressure will fall.

### BAZL Br.50 Q13 : Which of the following phenomena is typical in summer during the passage of an unstable cold front? ^bazl_50_13

> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_50_13)*
> *Source : BAZL/OFAC Série 1 - Branches Communes*

- A) Stratiform clouds.
- B) Rapid rise in temperature behind the front.
- C) Rapid fall in atmospheric pressure behind the front.
- D) Convective clouds.

**Correct : D)**

> **Explanation:** An unstable cold front in summer generates convective clouds (CB, TCu) with showers and thunderstorms.

### BAZL Br.50 Q18 : Of the situations described below, which is most likely to occur when a stable, warm and humid air mass slides over a cold air mass? ^bazl_50_18

> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_50_18)*
> *Source : BAZL/OFAC Série 1 - Branches Communes*

- A) At altitude: rapid drying of the air, dissipation of clouds, good visibility. In the lowlands: dense mist or fog at ground level.
- B) Formation of a few small cumuliform clouds, rare precipitation, light turbulence, excellent visibility.
- C) Formation of convective clouds, heavy showers, tendency for thunderstorms, severe turbulence.
- D) Formation of extensive stratiform clouds, cloud base gradually lowering, sustained rainfall.

**Correct : D)**

> **Explanation:** Warm and humid air sliding over cold air (warm front) = stratiform clouds, continuous rain, lowering cloud base.

### BAZL Br.50 Q14 : Which of the following air masses is likely to produce showers in central Europe regardless of the season? ^bazl_50_14

> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_50_14)*
> *Source : BAZL/OFAC Série 1 - Branches Communes*

- A) Maritime polar air.
- B) Maritime tropical air.
- C) Continental polar air.
- D) Continental tropical air.

**Correct : A)**

> **Explanation:** Maritime polar air is unstable (cold below, moist) → convection → showers in all seasons.

### BAZL Br.50 Q17 : What hazards are you likely to encounter in Switzerland in the presence of this meteorological situation? (Chart showing high pressure to the SW, depression to the N, NW flow) ^bazl_50_17

> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_50_17)*
> *Source : BAZL/OFAC Série 1 - Branches Communes*
> **Synoptic chart Switzerland/Alps:**
> ![[figures/bazl_50_q17_synoptic_alps.png]]
> *Anticyclone (H) to the west, depression (T) to the north-east, isobars indicating NW flow over Switzerland.*

- A) In winter, persistent snowfall in Ticino.
- B) To the south, the Alps are generally in cloud. North of the Alps, strong gusty winds.
- C) North of the Alps: continuous precipitation; south of the Alps: very disturbed weather.
- D) In summer, widespread thunderstorms south of the Alps due to blocking effect, accompanied by severe turbulence.

**Correct : C)**

> **Explanation:** NW situation (Nordwestlage): precipitation north of the Alps, blocking effect, disturbed conditions on both sides.

### BAZL Br.50 Q20 : To answer this question, refer to the Low Level SWC chart. Which of the following statements is correct? ^bazl_50_20

> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_50_20)*
> *Source : BAZL/OFAC Série 1 - Branches Communes*
> **Low Level Significant Weather Chart (OGDD70)**
> ![[figures/bazl_50_q20_low_level_swc.png]]
> *Fixed Time Prognostic Chart — Valid: 09 UTC, 22 JAN 2015*
> *Issued by MeteoSwiss*
>
> | Zone | Cloud cover | Cloud base | Cloud top | Visibility | Turbulence | Icing |
> |------|-----------|-------------|---------------|------------|------------|---------|
> | A | BKN/OVC SC, AC | 3000 ft | FL080 | > 10 km | MOD below FL080 | MOD FL040-FL080 |
> | B | BKN/OVC ST, SC | 1500 ft | FL060 | 5-8 km, locally 3 km (BR) | MOD below FL060 | MOD FL030-FL060 |
> | C | SCT/BKN CU, SC | 4000 ft | FL100 | > 10 km | ISOL MOD | LGT FL050-FL100 |
>
> *0°C isotherm: FL040 (north) to FL060 (south). Surface wind: SW 15-25 kt.*

- A) Rain and snow showers are to be expected in area A.
- B) In area B, cumuliform clouds are to be expected. Additionally, there may be light freezing rain or freezing fog.
- C) Area A lies between two warm fronts.
- D) Isolated thunderstorms may occur in area C. However, there will be no icing or turbulence.

**Correct : A)**

> **Explanation:** According to the SWC chart, area A is in the cold post-frontal sector with rain and snow showers.

### BAZL Br.50 Q4 : You are preparing to land on a sunny summer afternoon at an aerodrome whose runway runs parallel to the coast. The terrain is flat. As you begin the final approach, the coast is to your left. What will be the direction of the thermal wind? ^bazl_50_4

> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_50_4)*
> *Source : BAZL/OFAC Série 1 - Branches Communes*

- A) Tailwind.
- B) Crosswind from the left.
- C) Headwind.
- D) Crosswind from the right.

**Correct : B)**

> **Explanation:** In the afternoon, the sea breeze blows from sea to land. With the coast to the left, the wind comes from the left.

### BAZL Br.50 Q7 : Where are you most likely to encounter strong winds and turbulence in the low-level air layers? ^bazl_50_7

> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_50_7)*
> *Source : BAZL/OFAC Série 1 - Branches Communes*

- A) At the centre of a depression.
- B) At the centre of an anticyclone.
- C) In a region with a slack pressure gradient in winter.
- D) In the transition zone between two air masses.

**Correct : D)**

> **Explanation:** Frontal zones (transitions between air masses) produce the strongest wind gradients and turbulence.

### BAZL Br.50 Q8 : At a temperature of 10°C, an air mass has a relative humidity of 45%. How will this change if the temperature rises to 20°C? ^bazl_50_8

> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_50_8)*
> *Source : BAZL/OFAC Série 1 - Branches Communes*

- A) It will increase by 50%.
- B) It will decrease.
- C) It will remain constant.
- D) It will increase by 45%.

**Correct : B)**

> **Explanation:** If temperature rises (without adding moisture), the air can hold more water vapour → relative humidity decreases.

### BAZL Br.50 Q16 : On 1 June (summer time), you receive the Swiss GAFOR valid from 06:00 to 12:00 UTC. The forecast for the planned route is: "XMD". This means that: ^bazl_50_16

> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_50_16)*
> *Source : BAZL/OFAC Série 1 - Branches Communes*

- A) At 09:00 LT conditions on this route will be critical.
- B) At 09:00 LT the route will be closed.
- C) At 11:00 LT conditions on this route will be difficult.
- D) At 11:00 LT the route will be closed.

**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.

---

## Series 2 — FOCA/BAZL Mock Exam

### BAZL 501 Q1 — What does the symbol below represent? ^bazl_501_1
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_501_1)*
![[figures/bazl_501_q1.png]]
- A) Wind from SW, 25 kt
- B) Wind from NE, 25 kt
- C) Wind from SW, 110 kt
- D) Wind from SW, 110 kt
**Correct: A)**

> **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.

### BAZL 501 Q2 — At what time of day or night do you expect radiation fog to form? ^bazl_501_2
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_501_2)*
- A) Shortly after sunset
- B) At sunrise
- C) In the afternoon
- D) Shortly before midnight
**Correct: D)**

> **Explanation:** Radiation fog forms shortly before midnight or in the late night, when the ground has cooled sufficiently by radiation to cool the air to the dew point. It is most dense at dawn.

### BAZL 501 Q3 — What typical Swiss weather situation does the sketch below represent? ^bazl_501_3
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_501_3)*
![[figures/bazl_501_q3.png]]
- A) South Foehn situation
- B) Westerly wind situation
- C) Bise situation
- D) North Foehn situation
**Correct: C)**

> **Explanation:** The sketch shows the Bise situation (north-east wind in Switzerland, between the Alps and the Jura). It is a cold, dry wind from the east-northeast, typical of anticyclonic situations centered on northern Europe.

### BAZL 501 Q4 — With which altimeter setting does an altimeter on the ground at an airport indicate the airport elevation? ^bazl_501_4
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_501_4)*
- A) QFF
- B) QFE
- C) QNH
- D) QNE
**Correct: C)**

> **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.

### BAZL 501 Q5 — Which statement is correct regarding the clouds in the following METAR? LSGC 040620Z 23005KT 9000 -RA BKN012 09/08 Q1018= ^bazl_501_5
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_501_5)*
- A) 8 oktas, base at 1200 ft
- B) 5-7 oktas, base at 1200 ft
- C) 5-7 oktas, base at 12000 ft
- D) 5-7 oktas, base at 120 ft
**Correct: B)**

> **Explanation:** In the METAR: BKN012 means Broken (5-7 oktas) at 1200 ft. BKN = 5-7 oktas, 012 = base at 1200 ft.

### BAZL 501 Q6 — How will atmospheric pressure change at point A in the next hour? ^bazl_501_6
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_501_6)*
![[figures/bazl_501_q6.png]]
- A) Rapid and regular variations.
- B) A rise.
- C) No change.
- D) A fall.
**Correct: D)**

> **Explanation:** The synoptic chart shows a cold front approaching point A. Cold front passage is accompanied by a pressure drop before the front, then a rise after. Based on the front's position on the chart, pressure at point A will fall.

### BAZL 501 Q7 — What weather phenomena do you expect within zone 1 (south of France) at an altitude of 3500 ft AMSL? ^bazl_501_7
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_501_7)*
![[figures/bazl_501_q7.png]]
- A) 5-8 oktas of stratiform clouds, isolated thunderstorms, turbulence near the surface.
- B) Isolated thunderstorms, visibility 5 km outside showers, no turbulence below FL 070.
- C) Moderate icing, isolated thunderstorms with showers and turbulence.
- D) 3-4 oktas of stratiform clouds between 2000 ft and 7000 ft, visibility 8 km, turbulence below FL 070.
**Correct: C)**

> **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. The SIGMET or forecast weather shows these typical conditions.

### BAZL 501 Q8 — Which cloud type is composed exclusively of ice crystals? ^bazl_501_8
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_501_8)*
- A) Stratus
- B) Cumulonimbus
- C) Altocumulus
- D) Cirrus
**Correct: D)**

> **Explanation:** Cirrus clouds are exclusively composed of ice crystals. They form at very high altitude (above 6000 m) where temperatures are very low. Cumulonimbus can contain both phases (water and ice).

### BAZL 501 Q9 — With which cloud type is drizzle most likely to be encountered? ^bazl_501_9
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_501_9)*
- A) Cirrocumulus
- B) Cumulonimbus
- C) Altocumulus
- D) Stratus
**Correct: D)**

> **Explanation:** Drizzle is associated with stratus clouds (low stratiform clouds). Stratus produce fine, continuous drizzle. Cumulonimbus produce intense showers.

### BAZL 501 Q10 — Which of the following phenomena indicates a high risk of thunderstorms? ^bazl_501_10
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_501_10)*
- A) A bright ring around the sun (halo)
- B) Tower-shaped clouds (altocumulus castellanus)
- C) Lenticular clouds (altocumulus lenticularis)
- D) Stratiform clouds (stratus)
**Correct: B)**

> **Explanation:** Altocumulus castellanus (tower-shaped clouds) indicate significant atmospheric instability at medium altitude and are precursors of thunderstorms. Lenticular clouds indicate mountain waves.

### BAZL 501 Q11 — Which of the following phase transitions requires a heat input? ^bazl_501_11
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_501_11)*
- A) Transition from liquid to solid state
- B) Transition from liquid to gaseous state
- C) Transition from gaseous to solid state
- D) Transition from gaseous to liquid state
**Correct: B)**

> **Explanation:** The transition from liquid to gaseous state (evaporation) requires heat input (latent heat of evaporation). Conversely, condensation and solidification release heat.

### BAZL 501 Q12 — On which slopes are the strongest updrafts found in the diagram below? ^bazl_501_12
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_501_12)*
![[figures/bazl_501_q12.png]]
- A) 3 and 1
- B) 3 and 2
- C) 4 and 2
- D) 4 and 1
**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.

### BAZL 501 Q13 — Which of the following phenomena is likely behind an active cold front with unstable characteristics? ^bazl_501_13
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_501_13)*
- A) Rapid temperature rise, generally poor visibility.
- B) Rapid pressure drop, good visibility outside showers.
- C) Stratiform cloud cover, generally poor visibility.
- D) Gusty winds, good visibility outside showers.
**Correct: D)**

> **Explanation:** Behind an active cold front with unstable characteristics, expect gusty winds and good visibility between showers. The cold, unstable air following the front produces scattered showers but good visibility between them.

### BAZL 501 Q14 — An aircraft flies at flight level FL 70 from Bern (QNH 1012 hPa) to Marseille (QNH 1027 hPa). Will the true altitude above sea level change (all other things being equal) while the aircraft is at FL70? ^bazl_501_14
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_501_14)*
- A) It is not possible to answer the question.
- B) No.
- C) Yes, the aircraft climbs.
- D) Yes, the aircraft descends.
**Correct: D)**

> **Explanation:** At FL70, with higher QNH at destination (1027 hPa vs 1012 hPa at departure), the aircraft actually descends relative to true altitude. True altitude at FL70 is lower where QNH is higher, so the aircraft is actually flying lower.

### BAZL 501 Q15 — At a temperature of +2 degrees C, an air mass has a relative humidity of 35%. How will this change if the temperature drops to -5 degrees C? ^bazl_501_15
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_501_15)*
- A) Relative humidity decreases by 3%.
- B) Relative humidity decreases by 7%.
- C) Relative humidity increases.
- D) Relative humidity remains the same.
**Correct: C)**

> **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.

### BAZL 501 Q16 — A cold air mass moves over a warmer land area and warms in the lower air layers. How does it change? ^bazl_501_16
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_501_16)*
- A) If clouds form, mainly stratiform clouds can be expected.
- B) It becomes more unstable.
- C) Its relative humidity increases.
- D) Atmospheric pressure increases.
**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.

### BAZL 501 Q17 — On 1 July (summer time) you receive the Swiss GAFOR valid from 06:00 to 12:00 UTC. The forecast for the planned route is: "XXM". This means: ^bazl_501_17
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_501_17)*
- A) At 11:00 LT the flight route will be closed.
- B) At 11:00 LT the flight route will be critical. c) At 10:00 LT the flight route will be difficult.
- D) At 09:00 LT the flight route will be critical.
**Correct: B)**

> **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.

### BAZL 501 Q18 — How do the volume and temperature of a descending air mass change? ^bazl_501_18
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_501_18)*
- A) Both increase.
- B) Volume decreases, temperature increases.
- C) Both decrease.
- D) Volume increases, temperature decreases.
**Correct: B)**

> **Explanation:** A descending air mass (subsidence) is adiabatically compressed: volume decreases and temperature increases. The air descends and warms.

### BAZL 501 Q19 — To the north of a radiosonde at high altitude (Northern Hemisphere) there is a high pressure area, to the south a low pressure area. The wind will carry the balloon in the direction of: ^bazl_501_19
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_501_19)*
- A) South
- B) West
- C) North
- D) East
**Correct: D)**

> **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).

### BAZL 501 Q20 — With which temperature profile above an aerodrome is the risk of freezing rain greatest? ^bazl_501_20
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_501_20)*
![[figures/bazl_501_q20.png]]
- A) Profile B
- B) Profile A
- C) Profile D
- D) Profile C
**Correct: B)**

> **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.

---

## Series 3 — FOCA/BAZL Mock Exam

### BAZL 502 Q1 — Which of the following phase transitions releases heat? ^bazl_502_1
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_502_1)*
- A) Transition from solid to liquid state
- B) Transition from solid to gaseous state
- C) Transition from gaseous to liquid state
- D) Transition from liquid to gaseous state
**Correct: C)**

> **Explanation:** Transition from gaseous to liquid state (condensation) releases heat. Condensation releases the latent heat previously absorbed during evaporation.

### BAZL 502 Q2 — Where are the strongest downdraughts found in the diagram below? ^bazl_502_2
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_502_2)*
![[figures/bazl_502_q2.png]]
- A) 4
- B) 3
- C) 2
- D) 1
**Correct: B)**

> **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.

### BAZL 502 Q3 — How will atmospheric pressure change at point B in the next hour? ^bazl_502_3
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_502_3)*
![[figures/bazl_502_q3.png]]
- A) No change.
- B) Rapid and regular variations.
- C) A rise.
- D) A fall.
**Correct: C)**

> **Explanation:** The synoptic chart shows an anticyclone approaching point B. The approach of an anticyclone causes a pressure rise at point B in the next hour.

### BAZL 502 Q4 — An aircraft flies at flight level FL 90 from Zurich (QNH 1020 hPa) to Munich (QNH 1005 hPa). Will the true altitude above sea level change (all other things being equal) while the aircraft is at FL 90? ^bazl_502_4
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_502_4)*
- A) It is not possible to answer the question.
- B) No.
- C) Yes, the aircraft climbs.
- D) Yes, the aircraft descends.
**Correct: D)**

> **Explanation:** At FL90, flying from Zürich (QNH 1020) to Munich (QNH 1005): QNH decreases → true altitude decreases → aircraft descends relative to sea level while maintaining the same FL.

### BAZL 502 Q5 — At a temperature of 18 degrees C, an air mass has a relative humidity of 29%. How will this change if the temperature rises to 28 degrees C? ^bazl_502_5
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_502_5)*
- A) Relative humidity increases by 29%.
- B) Relative humidity increases by 10%.
- C) Relative humidity remains the same.
- D) Relative humidity decreases.
**Correct: D)**

> **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.

### BAZL 502 Q6 — A warm air mass moves over a colder land area and cools in the lower air layers. How does it change? ^bazl_502_6
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_502_6)*
- A) It becomes more stable.
- B) If clouds form, mainly convective clouds can be expected.
- C) Its relative humidity decreases.
- D) Atmospheric pressure falls.
**Correct: A)**

> **Explanation:** A warm air mass that cools from below becomes more stable (reduced temperature gradient). This promotes stratiform clouds, not convective clouds.

### BAZL 502 Q7 — On 1 August (summer time) you receive the Swiss GAFOR valid from 06:00 to 12:00 UTC. The forecast for the planned route is: "DDO". This means that: ^bazl_502_7
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_502_7)*
- A) At 08:00 LT the flight route will be critical.
- B) At 13:00 LT the flight route will be open.
- C) At 14:00 LT the flight route will be difficult.
- D) At 11:00 LT the flight route will be critical.
**Correct: B)**

> **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).

### BAZL 502 Q8 — How do the volume and temperature of a rising air mass change? ^bazl_502_8
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_502_8)*
- A) Both increase.
- B) Both decrease.
- C) Volume increases, temperature decreases.
- D) Volume decreases, temperature increases.
**Correct: C)**

> **Explanation:** A rising air mass expands adiabatically: volume increases and temperature decreases. This is adiabatic cooling.

### BAZL 502 Q9 — Under identical conditions, which precipitation is the least dangerous for aviation? ^bazl_502_9
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_502_9)*
- A) Hail
- B) Heavy snowfall
- C) Drizzle
- D) Rain showers
**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.

### BAZL 502 Q10 — Where do you have the greatest risk of encountering freezing rain? ^bazl_502_10
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_502_10)*
- A) In summer during the passage of a warm front.
- B) In winter during the passage of a cold front.
- C) In summer during the passage of a cold front.
- D) In winter during the passage of a warm front.
**Correct: D)**

> **Explanation:** Freezing rain is most common in winter during warm front passage, when rain from a warm layer falls through a sub-zero layer before reaching the ground.

### BAZL 502 Q11 — What does the symbol below represent? ^bazl_502_11
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_502_11)*
![[figures/bazl_502_q11.png]]
- A) Wind from SSW, 70 kt
- B) Wind from NNE, 70 kt
- C) Wind from SSW, 120 kt
- D) Wind from NNE, 120 kt
**Correct: A)**

> **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).

### BAZL 502 Q12 — What is the name of the phenomenon that develops when a moist air mass moves horizontally over a colder surface? ^bazl_502_12
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_502_12)*
- A) Sea spray
- B) Orographic fog
- C) Advection fog
- D) Radiation fog
**Correct: C)**

> **Explanation:** Advection fog forms by horizontal movement of a moist air mass over a colder surface. The air cools to its dew point.

### BAZL 502 Q13 — What typical Swiss weather situation does the sketch below represent? ^bazl_502_13
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_502_13)*
![[figures/bazl_502_q13.png]]
- A) South Foehn situation
- B) Westerly wind situation
- C) Bise situation
- D) North Foehn situation
**Correct: A)**

> **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.

### BAZL 502 Q14 — What must you set on the altimeter so that it indicates flight height (height AAL) above a particular aerodrome? ^bazl_502_14
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_502_14)*
- A) The QNH of the aerodrome.
- B) The QNE of the aerodrome.
- C) The QFE of the aerodrome.
- D) The QFF of the aerodrome.
**Correct: C)**

> **Explanation:** To display AAL height (Above Aerodrome Level), set the QFE of the aerodrome. The altimeter then shows 0 on the ground and height in flight.

### BAZL 502 Q15 — What is the wind speed and direction in the following METAR? LFSB 171100Z 29004KT 220V340 9999 FEW043 28/17 Q1013 NOSIG= ^bazl_502_15
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_502_15)*
- A) Wind from ESE, 4 knots, direction varying between SW and NNW
- B) Wind from WNW, 4 knots, direction varying between NE and SSE
- C) Wind from ESE, 4 knots, direction varying between NE and SSE.
- D) Wind from WNW, 4 knots, direction varying between SW and NNW.
**Correct: D)**

> **Explanation:** In METAR LFSB 171100Z 29004KT 220V340: wind from 290° (WNW), 4 knots, varying between 220° (SW) and 340° (NNW).

### BAZL 502 Q16 — What phenomenon is characteristic of a cold front advancing in summer in central Europe when the thermodynamic structure of the warm air is unstable? ^bazl_502_16
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_502_16)*
- A) Rapid fall of atmospheric pressure once the front has passed.
- B) Thunderstorm clouds.
- C) Stratiform clouds.
- D) Rapid rise in temperature once the front has passed.
**Correct: B)**

> **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.

### BAZL 502 Q17 — What weather phenomena should be expected along the route from LOWK to EDDP (dotted arrow)? ^bazl_502_17
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_502_17)*
![[figures/bazl_502_q17.png]]
- A) Progressive decrease in temperature, headwind, isolated thunderstorms.
- B) Progressive increase in temperature, headwind, no thunderstorms.
- C) Progressive increase in temperature, tailwind, isolated thunderstorms.
- D) Progressive decrease in temperature, tailwind, isolated thunderstorms.
**Correct: A)**

> **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.

### BAZL 502 Q18 — Which cloud type is most likely to produce heavy showers? ^bazl_502_18
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_502_18)*
- A) Cirrocumulus
- B) Cumulonimbus
- C) Altostratus
- D) Nimbostratus
**Correct: B)**

> **Explanation:** Cumulonimbus (Cb) are the clouds that produce the heaviest showers, hail, and thunderstorms. They contain enormous quantities of water and ice.

### BAZL 502 Q19 — To the north of a radiosonde at high altitude (Northern Hemisphere) there is a low pressure area, to the south a high pressure area. The wind will carry the balloon in the direction of: ^bazl_502_19
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_502_19)*
- A) South
- B) East
- C) West
- D) North
**Correct: C)**

> **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).

### BAZL 502 Q20 — What are the thunderstorms called that occur when air is forced to rise by topography and reaches unstable, moist layers? ^bazl_502_20
> *[FR](../SPL%20Exam%20Questions%20FR/50%20-%20M%C3%A9t%C3%A9orologie.md#^bazl_502_20)*
- A) Thermal thunderstorms
- B) Cold front thunderstorms
- C) Warm front thunderstorms
- D) Orographic thunderstorms
**Correct: D)**

> **Explanation:** Orographic thunderstorms occur when air is forced to rise by topography (mountains) and reaches unstable, moist layers. Distinct from thermal or frontal thunderstorms.