Humidity, Clouds & Rainfall – NDA Geography PYQs

Practice NDA Geography previous-year questions with detailed solutions and explanations.

Chapter-wise PYQs • Concept-based explanations • Exam insights

NDA 2021-I

Q. 1. Which of the following clouds is associated with steady and prolonged rainfall?

(a) Cumulus

(b) Nimbostratus

(d) Cumulonimbus

Answer: (b) Nimbostratus

Explanation: Nimbostratus is a dark, thick, grey cloud layer that covers the sky and produces steady, continuous, widespread rainfall (or snowfall) for many hours. Cumulus (a): fair-weather puffy clouds; no significant rainfall unless they develop into cumulonimbus. Cirrus (c): high, thin ice crystal clouds; do not produce precipitation. Cumulonimbus (d): thunderstorm cloud; produces intense but short-duration rain, hail, and lightning.
Concept Tested: Nimbostratus: associated with steady, prolonged rainfall; distinct from Cumulonimbus (intense short showers)

NDA 2019-I

Q. 2. Which one of the following is the correct sequence of cloud types from the lowest to highest altitude?

(a) Nimbostratus: Altocumulus: Cirrus

(b) Cirrus: Altocumulus: Nimbostratus

(d) Nimbostratus: Cirrus: Altocumulus

Answer: (a) Nimbostratus: Altocumulus: Cirrus

Explanation: Cloud altitude from lowest to highest: Nimbostratus: a dark, low to middle-level cloud associated with continuous rain; altitude below 2,000 m. Altocumulus: a middle-level cloud; altitude 2,000–6,000 m. Cirrus: a high cloud of ice crystals; altitude 6,000–12,000 m. Correct ascending order: Nimbostratus (lowest) → Altocumulus → Cirrus (highest).
Concept Tested: Cloud altitude sequence (low to high): Nimbostratus → Altocumulus → Cirrus

NDA 2017-II

Q. 3. When temperature rises, relative humidity:

(a) Increases

(b) Decreases

(d) First increases and then decreases

Answer: (b) Decreases

Explanation: When temperature rises while the actual water vapour content (absolute humidity) remains constant: Saturation vapour pressure increases with temperature. Relative humidity = Actual vapour pressure / Saturation vapour pressure × 100%. Since the denominator (saturation vapour pressure) increases but the numerator (actual vapour pressure) stays the same, RH decreases. This is why deserts are dry and hot: during the day, high temperatures greatly reduce relative humidity even though the absolute water vapour content may not change dramatically.
Concept Tested: Rising temperature → increasing saturation vapour pressure → decreasing relative humidity (constant absolute humidity)

NDA 2016-II

Q. 4. Which of the following pairs of types of precipitation and their descriptions is NOT correctly matched?

(a) Rain: water droplets larger than 0.5 mm in diameter

(b) Drizzle: water droplets of 0.2 to 0.5 mm in diameter

(d) Hail: falling water droplets that freeze as they fall

Answer: (d) Hail: falling water droplets that freeze as they fall

Explanation: Option (d) is NOT correctly matched. Hail does NOT form simply by water droplets freezing as they fall. Hail forms within cumulonimbus clouds through a different process: ice pellets are carried upward by strong updrafts, picking up more layers of ice as they cycle through the cloud. When they become too heavy for the updrafts, they fall to the ground as hailstones. Sleet (option c): frozen raindrops that pass through a freezing layer near the surface. This IS correctly matched. Rain (a) and Drizzle (b): their size descriptions are approximately correct.
Concept Tested: Hail: NOT falling drops that freeze; forms in cumulonimbus through updraft cycling and ice layer accumulation

NDA 2015-II

Q. 5. The leeward side of a mountain receives:

(a) Less rainfall than the windward side

(b) More rainfall than the windward side

(d) No rainfall at all

Answer: (a) Less rainfall than the windward side

Explanation: The windward (upwind) side of a mountain forces moist air to rise, cool, condense, and produce orographic rainfall. The leeward (downwind) side is in the rain shadow: the air descends, warms (adiabatically), and becomes dry, receiving much less rainfall. Examples: Western Ghats: western (windward) side receives 200–400 cm annual rainfall; eastern (leeward) Deccan receives 50–70 cm. Sierra Nevada, California: western (windward) side is lush; eastern Nevada is desert. The Sahara Desert partially exists because of rain shadow effects.
Concept Tested: Leeward side (rain shadow) receives LESS rainfall than windward side: orographic effect

NDA 2015-I

Q. 6. A rain gauge is used to measure:

(a) Atmospheric pressure

(b) Wind speed

(d) Humidity

Answer: (c) Amount of rainfall

Explanation: A rain gauge (pluviometer or udometer) is a meteorological instrument used to measure the amount of rainfall (precipitation) over a given area and time period. It measures rainfall in millimetres (mm) or inches. Other meteorological instruments: Barometer: measures atmospheric pressure. Anemometer: measures wind speed. Hygrometer: measures humidity. Thermometer: measures temperature.
Concept Tested: Rain gauge: measures the amount of rainfall in mm; other instruments: barometer (pressure), anemometer (wind speed), hygrometer (humidity)

NDA 2014-I

Q. 7. Dew is formed when:

(a) The temperature of the surface falls below the dew point of air above it

(b) The temperature of the surface rises above the dew point

(d) Wind blows strongly at night

Answer: (a) The temperature of the surface falls below the dew point of air above it

Explanation: Dew is water droplets that form on surfaces (leaves, grass, car windshields) when the surface temperature drops below the dew point of the overlying air. On calm, clear nights, surfaces lose heat rapidly by radiation. When the surface temperature falls to or below the dew point, water vapour from the adjacent air condenses as dew on the surface. If the dew point is below 0°C, ice crystals form instead of liquid dew: this is called frost.
Concept Tested: Dew: surface temperature falls below dew point → water vapour condenses on surface; frost if below 0°C

NDA 2013-II

Q. 8. Which one of the following is NOT a form of precipitation?

(a) Snow

(b) Hail

(d) Mist

Answer: (d) Mist

Explanation: Precipitation refers to any form of water that falls from clouds to the Earth’s surface. Forms of precipitation: Rain, Drizzle, Snow, Hail, Sleet (partially melted snow/ice pellets), Freezing rain. Mist is NOT precipitation: it is a suspension of tiny water droplets in the air (like very light fog). It does not fall from clouds; it is a surface atmospheric phenomenon. Mist and fog are forms of condensation in the atmosphere, not precipitation.
Concept Tested: Mist is NOT precipitation: it is suspended water droplets in air; Snow, Hail, Sleet are all precipitation

NDA 2013-I

Q. 9. Which one of the following is the highest cloud?

(a) Stratus

(b) Cirrus

(d) Nimbostratus

Answer: (b) Cirrus

Explanation: Cirrus clouds are the highest clouds, found at altitudes of 6,000–12,000 metres (20,000–40,000 feet). They are composed of ice crystals and appear as thin, wispy, hair-like streaks or curls. Cloud altitude categories: High clouds (above 6,000 m): Cirrus, Cirrostratus, Cirrocumulus. Middle clouds (2,000–6,000 m): Altostratus, Altocumulus. Low clouds (below 2,000 m): Stratus, Stratocumulus, Nimbostratus. Vertical clouds: Cumulus, Cumulonimbus (extend from low to high altitudes). Concept Tested: Cirrus: highest cloud type; 6,000–12,000 m; ice crystals; thin, wispy appearance

★ JOVIK Exam Insight Cloud classification for NDA: High clouds (ice crystals, above 6 km): Cirrus (wispy), Cirrostratus (transparent sheet), Cirrocumulus (small ripples). Middle clouds (2–6 km): Altostratus, Altocumulus. Low clouds (below 2 km): Stratus (grey layer, drizzle), Nimbostratus (dark rain cloud, steady rain), Stratocumulus. Vertical/Convective: Cumulus (fair weather), Cumulonimbus (thunderstorm, lightning, heavy rain, hail). Nimbostratus = rain cloud; Cumulonimbus = storm cloud: these are the most tested.

NDA 2012-I

Q. 10. Consider the following statements about fog:

1. Fog reduces visibility to less than 1 km.

2. Fog is formed when water vapour in air condenses at or near ground level.

Which of the statements given above is/are correct?

(a) 1 only

(b) 2 only

(d) Neither 1 nor 2

Answer: (c) Both 1 and 2

Explanation: Statement 1: Correct. By meteorological definition, fog is a condition where visibility is reduced to 1 km or less (some definitions use less than 1 km; others less than 200 m for “dense fog”). Statement 2: Correct. Fog forms when water vapour condenses at or near ground level, creating a cloud at surface level. It is essentially a low-lying cloud.
Concept Tested: Fog: visibility < 1 km; water vapour condenses at or near ground level; essentially a surface-level cloud

NDA 2011-I

Q. 11. Which one of the following statements about fog is NOT correct?

(a) Fog is most frequent in low lying areas and river valleys

(b) Radiation fog is formed during calm, clear nights when the ground surface cools through long-wave radiation

(d) Temperature of the fog layer is above the dew point of the air

Answer: (d) Temperature of the fog layer is above the dew point of the air

Explanation: Option (d) is NOT correct: it is false. Fog forms when air is cooled to its dew point or below: causing water vapour to condense into tiny water droplets. By definition, the temperature within a fog layer is AT or BELOW the dew point, not above it. (a): Correct. Cold air pools in low areas and valleys, making fog more common there. (b): Correct. Radiation fog forms on calm, clear nights when the ground radiates heat and cools air near the surface below the dew point. (c): Correct. Advection fog forms when warm, moist air moves horizontally over a cooler surface (ocean, land). San Francisco’s fog is a classic example.
Concept Tested: Fog forms when air is at or BELOW dew point (not above); fog types: radiation fog, advection fog

NDA 2010-II

Q. 12. Consider the following statements:

1. Absolute humidity is the amount of water vapour present per unit volume of air, usually expressed in grams per cubic metre.

2. Relative humidity can be expressed as a percentage.

Which of the statements given above is/are correct?

(a) 1 only

(b) 2 only

(d) Neither 1 nor 2

Answer: (c) Both 1 and 2

Explanation: Statement 1: Correct. Absolute humidity is the actual mass of water vapour per unit volume of air, typically expressed in grams per cubic metre (g/m³). It does not vary with temperature changes as long as the actual water vapour content remains the same. Statement 2: Correct. Relative humidity is always expressed as a percentage: the ratio of actual to saturation vapour pressure × 100%.
Concept Tested: Absolute humidity (g/m³) and relative humidity (%): both correctly defined; both statements correct

NDA 2009-I

Q. 13. Which one of the following is the best definition of relative humidity?

(a) The actual amount of water vapour present in the air

(b) The ratio of actual water vapour present in air to the maximum amount it can hold at the same temperature, expressed as a percentage

(d) The maximum amount of water vapour air can hold at a given temperature

Answer: (b) The ratio of actual water vapour present in air to the maximum amount it can hold at the same temperature, expressed as a percentage

Explanation: Relative Humidity (RH) = (Actual vapour pressure / Saturation vapour pressure) × 100% It expresses how close the air is to being fully saturated. RH = 100% means the air is saturated (at the dew point). Below 100%, the air can hold more water vapour. Important: RH varies with temperature. If temperature rises, saturation vapour pressure increases, so the same absolute humidity gives a LOWER relative humidity. If temperature falls, saturation decreases, so RH increases.
Concept Tested: Relative humidity: ratio of actual water vapour to saturation amount, expressed as percentage

NDA 2008-I

Q. 14. ‘Dew point’ refers to:

(a) The amount of water vapour in the air

(b) The temperature at which the air becomes saturated with water vapour

(d) The temperature at which dew is maximum

Answer: (b) The temperature at which the air becomes saturated with water vapour

Explanation: The dew point (or dew-point temperature) is the temperature to which air must be cooled (at constant pressure and humidity) for it to become saturated: reaching 100% relative humidity. When the air temperature falls to the dew point, condensation begins: producing dew (on surfaces), fog (in the air near the surface), or frost (if the dew point is below 0°C). The closer the dew point is to the actual temperature, the higher the relative humidity and the more likely condensation is. Concept Tested: Dew point: temperature at which air becomes saturated (RH = 100%); condensation begins