Insolation & Heat Budget – NDA Geography PYQs

NDA 2022-I

Q. 1. What is the approximate Albedo of the Earth?

(a) 10 per cent

(b) 20 per cent

(c) 30 per cent

(d) 40 per cent

Answer: (c) 30 per cent

Explanation: Earth’s average albedo (planetary albedo) is approximately 30%: meaning Earth reflects about 30% of incoming solar radiation back to space. The remaining 70% is absorbed by Earth’s surface and atmosphere. Major contributors to Earth’s albedo: clouds (account for most of the reflection), ice and snow, deserts, and the atmosphere itself. This 30% figure is an important constant in climate science. If Earth’s albedo increases (e.g., due to more ice), less energy is absorbed and temperatures fall. If albedo decreases (e.g., ice melting), more energy is absorbed: positive feedback for warming. Concept Tested: Earth’s albedo ≈ 30%; Earth reflects ~30% of incoming solar radiation back to space

NDA 2021-I

Q. 2. The atmosphere is mainly heated by which of the following?

(a) Solar radiation directly

(b) Cosmic rays

(c) Radiation from the Earth’s surface

(d) Conduction from the outer space

Answer: (c) Radiation from the Earth’s surface

Explanation: The troposphere (lower atmosphere) is primarily heated from below: by radiation from the Earth’s surface. The process: Solar radiation (shortwave) passes through the atmosphere relatively freely and heats Earth’s surface. The warmed Earth then radiates longwave (infrared) radiation upward. Greenhouse gases (CO₂, water vapour) in the troposphere absorb this longwave radiation, warming the atmosphere. The atmosphere is NOT primarily heated by direct solar radiation: most shortwave solar radiation passes through the atmosphere without being absorbed. Concept Tested: Atmosphere (troposphere) is mainly heated by longwave radiation from Earth’s surface: not directly by solar radiation

NDA 2020-I

Q. 3. Normal lapse rate is a rate of:

(a) Increase in temperature with altitude

(b) Decrease in temperature with altitude

(c) Decrease in pressure with altitude

(d) Increase in humidity with altitude

Answer: (b) Decrease in temperature with altitude

Explanation: The Normal Lapse Rate (Environmental Lapse Rate) is the average rate at which temperature DECREASES with altitude in the troposphere: approximately 6.5°C per 1,000 metres. This decrease occurs because: 1. The troposphere is primarily heated from below (by Earth’s surface radiating longwave energy after absorbing solar radiation). 2. As altitude increases, distance from the heat source increases and air pressure decreases (allowing air to expand and cool). Concept Tested: Normal lapse rate: temperature DECREASES with altitude in troposphere at ~6.5°C per 1,000 m

NDA 2019-II

Q. 4. Isotherms are lines connecting places that have:

(a) Equal rainfall

(b) Equal air pressure

(c) Equal temperature

(d) Equal sunshine

Answer: (c) Equal temperature

Explanation: An Isotherm is a contour line connecting all places that have the same temperature (at a given time or averaged over a period). The “iso-” prefix (from Greek) means “equal”. Other iso-lines: Isobar: equal air pressure. Isohyet: equal rainfall. Isohaline: equal salinity. Isoseismal: equal earthquake intensity. Concept Tested: Isotherm = line connecting places of equal temperature; “iso” = equal, “therm” = heat/temperature

NDA 2017-I

Q. 5. A place that has a large annual range of temperature is said to exhibit:

(a) Continentality

(b) Cyclonality

(c) Oceanicity

(d) Aridity

Answer: (a) Continentality

Explanation: Continentality refers to the climatic condition of inland (continental) locations that are far from the moderating influence of the ocean. Such places experience: 1. Hot summers (high maximum temperatures). 2. Cold winters (very low minimum temperatures). 3. Large annual range of temperature (difference between warmest and coldest months). In contrast, Oceanicity refers to the moderating influence of the ocean: coastal areas have smaller temperature ranges. Examples of high continentality: Siberia, Central Asia, interior Canada. Concept Tested: Continentality: large annual temperature range; hot summers, cold winters in continental interiors far from ocean

NDA 2016-I

Q. 6. The phenomenon of occurrence of higher temperature at higher altitude in a layer of the atmosphere is called:

(a) Lapse rate

(b) Inversion of temperature

(c) Albedo

(d) Thermal gradient

Answer: (b) Inversion of temperature

Explanation: Temperature inversion (or inversion of temperature) is the reversal of the normal temperature gradient: where temperature INCREASES with altitude instead of decreasing. Normally in the troposphere, temperature decreases with altitude (normal lapse rate). During an inversion, a warm layer sits above a cooler layer, creating a stable atmospheric condition. Common causes: Radiation cooling of the surface at night; subsidence in anticyclones; cold Arctic air flowing under warmer air. Temperature inversion also occurs in the stratosphere (due to ozone absorbing UV) and thermosphere (due to X-ray absorption). Concept Tested: Temperature inversion: temperature increases with altitude instead of the normal decrease; stable atmospheric condition

NDA 2015-I

Q. 7. What is the reason behind the moderating influence of the sea on the temperature of the nearby coastal areas?

(a) Low density of sea water

(b) Specific heat capacity of water

(c) The depth of the sea

(d) The volume of the sea

Answer: (b) Specific heat capacity of water

Explanation: Water has a very high specific heat capacity (4,186 J/kg/°C) compared to land (about 800 J/kg/°C). This means water requires much more energy to raise its temperature: and releases energy slowly when cooling. Because of this, the sea heats up slowly in summer (staying cooler than inland areas) and cools slowly in winter (staying warmer). This moderates the temperature of nearby coastal areas: preventing the extreme heat and cold experienced by inland (continental) regions. This phenomenon explains why coastal cities like Mumbai and London have more moderate climates than inland cities at similar latitudes. Concept Tested: Sea moderates coastal temperatures due to HIGH specific heat capacity of water; heats/cools slowly

NDA 2014-II

Q. 8. Consider the following statements:

1. Temperature generally decreases from equator towards the poles.

2. Isotherms do not exactly follow the latitudinal lines because of the differential heating of landmasses and the oceans.

Which of the statements given above is/are correct?

(a) 1 only

(b) 2 only

(c) Both 1 and 2

(d) Neither 1 nor 2

Answer: (c) Both 1 and 2

Explanation: Statement 1: Correct. The equator receives the most direct solar radiation and has the highest temperatures. Temperature generally decreases as you move poleward because sunlight becomes more oblique and days are shorter in winter. Statement 2: Correct. Isotherms deviate from latitude lines because land and sea at the same latitude have different temperatures. Over continents, temperatures are more extreme (hotter in summer, colder in winter). Over oceans, temperatures are moderated. This differential causes isotherms to bend and deviate from the parallels. Concept Tested: Temperature decreases equator to poles; isotherms deviate from parallels due to land-sea differential heating

NDA 2013-II

Q. 9. In general, temperature decreases as altitude increases. This is called:

(a) Atmospheric pressure gradient

(b) Altitude effect

(c) Normal lapse rate

(d) Adiabatic lapse rate

Answer: (c) Normal lapse rate

Explanation: The Normal Lapse Rate (also called the Environmental Lapse Rate or Standard Lapse Rate) is the average rate at which temperature decreases with altitude in the troposphere: approximately 6.5°C per 1,000 metres (or 6.5°C/km). This is different from the Adiabatic Lapse Rate, which is the rate of temperature change in rising or sinking air parcels: Dry Adiabatic Lapse Rate (DALR): 10°C/km for unsaturated air. Saturated Adiabatic Lapse Rate (SALR): 4–9°C/km for saturated (cloudy) air. Concept Tested: Normal lapse rate: temperature decreases at ~6.5°C per 1,000 m in troposphere; not adiabatic lapse rate

NDA 2013-I

Q. 10. Which one of the following statements about isotherms is NOT correct?

(a) Isotherms are lines of equal temperature

(b) Isotherms mostly run parallel to the latitudinal lines

(c) Isotherms deviate from the parallels of latitude in the temperate zone

(d) Isotherms do not deviate anywhere from the parallels of latitude

Answer: (d) Isotherms do not deviate anywhere from the parallels of latitude

Explanation: Option (d) is NOT correct: it is false. (a): Correct. Isotherms connect places of equal temperature. (b): Correct. Isotherms generally run parallel to latitude lines because temperature broadly decreases from equator to poles. (c): Correct. In the temperate zone, isotherms deviate notably from latitudinal parallels because of the contrasting temperatures of continents and oceans at the same latitude. In summer, continents are warmer than oceans (isotherms deflect poleward over continents); in winter, oceans are warmer (isotherms deflect poleward over oceans). (d): FALSE. Isotherms DO deviate from parallels: especially over continents and ocean boundaries. They are never perfectly aligned with latitudinal lines everywhere. Concept Tested: Isotherms DO deviate from latitude parallels: especially in temperate zone over continents and oceans

NDA 2012-I

Q. 11. Which one of the following best explains why temperatures in cities are generally higher than in the surrounding rural areas?

(a) Urban Heat Island effect

(b) Greenhouse effect

(c) Air pollution in cities

(d) Higher building density

Answer: (a) Urban Heat Island effect

Explanation: The Urban Heat Island (UHI) effect occurs when urban areas are significantly warmer than their surrounding rural areas. This is caused by: 1. Dark surfaces (asphalt, concrete) absorbing more solar radiation. 2. Less vegetation and transpiration in cities (trees cool through evapotranspiration). 3. Waste heat from vehicles, air conditioners, industries. 4. Dense buildings trapping heat and blocking wind. 5. Reduced sky view factor: buildings limit outgoing radiation at night. The UHI effect can raise urban temperatures by 2–8°C above rural surroundings. Concept Tested: Urban Heat Island effect: cities warmer than rural areas due to dark surfaces, low vegetation, and waste heat

NDA 2011-I

Q. 12. Which of the following has the maximum albedo?

(a) Fresh snow

(b) Tropical forests

(c) Dark soil

(d) Sandy deserts

Answer: (a) Fresh snow

Explanation: Albedo is the fraction of incoming solar radiation that is reflected back from a surface. High albedo = more reflection; low albedo = more absorption. Fresh snow has the highest albedo among common surfaces: approximately 80–90%. Its bright white surface reflects most sunlight. For comparison: Tropical forests ~12–15%; Dark soil ~5–10%; Sandy desert ~25–40%. The Earth’s average albedo is approximately 30%. Ice caps with high albedo play a role in regulating Earth’s temperature. Concept Tested: Albedo: fraction of solar radiation reflected; fresh snow has highest albedo (~80-90%)

NDA 2010-II

Q. 13. ‘Insolation’ refers to:

(a) A type of insulation used in buildings

(b) Lack of sunshine or solar energy

(c) Incoming solar radiation

(d) The process of insulation of materials

Answer: (c) Incoming solar radiation

Explanation: Insolation stands for INcoming SOLar radiATION: the amount of solar energy received per unit area on Earth’s surface or at the top of the atmosphere. Insolation varies with: 1. Latitude: equatorial regions receive more direct insolation; poles receive oblique, weaker insolation. 2. Season: the angle and duration of sunlight varies with Earth’s tilt and revolution. 3. Time of day: noon has maximum insolation; sunrise/sunset has minimum. 4. Aspect: south-facing slopes receive more insolation in the Northern Hemisphere. Concept Tested: Insolation = INcoming SOLar radiATION; varies with latitude, season, time of day, and aspect

NDA 2009-I

Q. 14. Consider the following statements:

1. Land surfaces heat up more quickly than sea surfaces.

2. Sea surfaces cool off more quickly than land surfaces.

Which of the statements given above is/are correct?

(a) 1 only

(b) 2 only

(c) Both 1 and 2

(d) Neither 1 nor 2

Answer: (c) Both 1 and 2

Explanation: Statement 1: Correct. Land heats up faster than water because land has a much lower specific heat capacity. The same amount of solar energy raises the temperature of land more than water. Statement 2: Correct. The reverse is also true: land cools off more quickly than sea surfaces (at night or during winter). The sea retains heat for longer because of its high specific heat capacity. This differential heating and cooling of land and sea is the basis for sea breezes, land breezes, monsoons, and the moderating effect of the ocean on coastal climates. Concept Tested: Land heats and cools faster than sea: due to lower specific heat capacity of land vs. water

★ JOVIK Exam Insight Land-sea heating difference for NDA: Land: low specific heat; heats quickly in day/summer; cools quickly at night/winter. Sea: high specific heat; heats slowly; cools slowly; moderates coastal temperatures. Consequences: Sea breeze (land heats faster in day → air rises → sea air flows in). Land breeze (land cools faster at night → air sinks → flows to sea).

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