Visibility and FogAviation Meteorology — DGCA CPL practice questions
Question 1 of 20
Fog is reported when visibility is reduced to:
All 20 questions — Visibility and Fog
Aviation Meteorology · DGCA CPL. The correct option is marked on each.
Q1. Fog is reported when visibility is reduced to:
- A.Less than 1000 m✓
- B.Exactly 1000 m
- C.1000 to 2000 m
Why: Fog = visibility below 1000 m.
Q2. RVR is reported when the visibility falls below:
- A.500 m
- B.1000 m
- C.1500 m✓
Why: RVR is assessed/reported when visibility is below 1500 m.
Q3. Radiation fog forms:
- A.Over land✓
- B.Over sea
- C.During the day
Why: Radiation fog forms over land by night-time cooling.
Q4. When visibility is between 5000 m and 1000 m with RH near 100%, the phenomenon is:
- A.Mist✓
- B.Haze
- C.Fog
Why: Mist = reduced visibility with high humidity; haze is dry.
Q5. Radiation fog forms over North India mainly during:
- A.May–June
- B.December–February✓
- C.October–November
Why: Winter gives the long cold nights needed.
Q6. Warm, moist air moving over cold ground gives rise to:
- A.Thunder clouds
- B.Fog and stratus✓
- C.Frontal clouds
Why: Cooling from below saturates the air → fog/stratus.
Q7. Warm, moist air moving over a cold surface causes:
- A.Radiation fog
- B.Advection fog✓
- C.Frontal fog
Why: Horizontal transport of warm moist air over a cold surface = advection fog.
Q8. Radiation fog forms due to:
- A.Daytime heating of the earth
- B.Radiational cooling of the earth at night✓
- C.Advection of cold air
Why: Night-time long-wave cooling of the ground.
Q9. Radiation-fog activity increases after the passage of a:
- A.Western Disturbance✓
- B.Depression
- C.Col
Why: Clearing skies + residual moisture behind a WD favour radiation fog.
Q10. Radiation fog is essentially a ____ phenomenon:
- A.Nocturnal✓
- B.Dusk
- C.Daytime
Why: It forms overnight and clears after sunrise.
Q11. Radiation fog forms over:
- A.Water
- B.Land✓
- C.Both equally
Why: Land cools rapidly at night; the sea does not.
Q12. The fog formed by horizontal movement of warm moist air over a cold surface is:
- A.Radiation
- B.Advection✓
- C.Frontal
Why: Advection fog.
Q13. Advection fog forms during:
- A.Night only
- B.Daytime only
- C.Any time of day or night✓
Why: It depends on air movement, not on time of day.
Q14. Radiation fog requires:
- A.Moisture, cloudy sky, no wind
- B.Moisture, clear sky, light wind✓
- C.Moisture, cloudy sky, strong wind
Why: Clear sky, moisture, and light wind.
Q15. The instrument used to measure visibility is the:
- A.Visiometer
- B.Transmissometer✓
- C.Ceilometer
Why: A transmissometer measures visibility/RVR; a ceilometer measures cloud base.
Q16. Advection fog forms:
- A.Over sea only
- B.Over land only
- C.Both over land and sea✓
Why: Advection fog can occur over either surface.
Q17. Fog is essentially ____ cloud on the ground:
- A.Stratocumulus
- B.Stratus✓
- C.Nimbostratus
Why: Fog is stratus cloud at the surface.
Q18. Frontal fog is most common with a:
- A.Western Disturbance
- B.Cyclone
- C.Warm front✓
- D.Cold front
Why: Rain evaporating into cold air ahead of a warm front → frontal fog.
Q19. The pressure system most favourable for fog formation is:
- A.Lows and cols
- B.Highs and troughs
- C.Lows and ridges
- D.Highs and cols✓
Why: Highs and cols give the light winds and clear skies fog needs.
Q20. The temperature structure that favours fog formation is an:
- A.Isothermal layer
- B.Adiabatic layer
- C.Inversion✓
- D.SALR layer
Why: A surface inversion traps moisture and cooling near the ground.