The Atmosphere

11. In which one of the following layers of the atmosphere all weather phe

In which one of the following layers of the atmosphere all weather pheno-menon occur ?

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Mesosphere
Troposphere
Thermosphere
Stratosphere
This question was previously asked in
UPSC NDA-2 – 2023
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The Troposphere is the lowest layer of Earth’s atmosphere, extending from the surface up to an average altitude of about 7-15 kilometers (varying with latitude and season). It contains about 75-80% of the atmosphere’s mass and nearly all of its water vapor and aerosols. Weather phenomena, such as clouds, precipitation, storms, fronts, and most air currents, occur almost exclusively within the troposphere due to the presence of water vapor and the process of convection.
Almost all weather phenomena on Earth occur in the Troposphere, the lowest layer of the atmosphere.
The layer above the troposphere is the Stratosphere, which contains the ozone layer and is relatively stable with minimal weather. The Mesosphere and Thermosphere are even higher layers with negligible weather activity.

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12. Which one of the following is the correct sequence of layers as we mov

Which one of the following is the correct sequence of layers as we move from the Earth’s surface upwards?

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Troposphere, Stratosphere, Thermosphere, Mesosphere
Troposphere, Stratosphere, Mesosphere, Thermosphere
Thermosphere, Mesosphere, Stratosphere, Troposphere
Stratosphere, Mesosphere, Troposphere, Thermosphere
This question was previously asked in
UPSC NDA-2 – 2021
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The correct option is B, Troposphere, Stratosphere, Mesosphere, Thermosphere.
The Earth’s atmosphere is divided into several layers based on temperature profiles and composition as we move upwards from the surface. The principal layers, in order from the Earth’s surface outwards, are:
1. **Troposphere:** The lowest layer, where most weather occurs. Temperature generally decreases with altitude.
2. **Stratosphere:** Above the troposphere, contains the ozone layer. Temperature increases with altitude due to ozone absorption of UV radiation.
3. **Mesosphere:** Above the stratosphere. Temperature decreases with altitude; it is the coldest layer. Most meteors burn up here.
4. **Thermosphere:** Above the mesosphere. Temperature increases sharply with altitude due to absorption of high-energy solar radiation by sparse gas molecules. The International Space Station orbits here.
Above the thermosphere is the Exosphere, transitioning into outer space.
The given options only list the first four main layers. The correct sequence starting from the surface is Troposphere, followed by Stratosphere, then Mesosphere, and finally Thermosphere among the layers listed.

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13. The Earth’s atmosphere is mainly heated by which one of the following

The Earth’s atmosphere is mainly heated by which one of the following ?

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Short wave solar radiation
Reflected solar radiation
Long wave terrestrial radiation
Scattered solar radiation
This question was previously asked in
UPSC NDA-2 – 2021
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The correct option is C, Long wave terrestrial radiation.
The Earth’s atmosphere is primarily heated indirectly. Incoming shortwave solar radiation (A) passes through the atmosphere with relatively little absorption, directly heating the Earth’s surface. The heated surface then emits energy in the form of longwave infrared radiation (C). Greenhouse gases in the atmosphere (like carbon dioxide, water vapor, methane, etc.) are efficient absorbers of this longwave terrestrial radiation. This absorption by greenhouse gases is the main process by which the atmosphere is heated, particularly in the lower layers (troposphere).
Reflected solar radiation (B) does not heat the atmosphere; it is simply bounced back into space or scattered (D). While scattered solar radiation contributes to diffuse light and some heating, the primary heating mechanism for the bulk of the atmosphere, especially the troposphere, is the absorption of outgoing longwave radiation emitted by the Earth’s surface – the greenhouse effect.

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14. The normal lapse rate of temperature of Earth’s atmosphere drops to 0°

The normal lapse rate of temperature of Earth’s atmosphere drops to 0°C at the

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upper part of ionosphere.
upper boundary of the tropopause.
lower part of mesosphere.
upper boundary of stratopause.
This question was previously asked in
UPSC NDA-2 – 2019
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The temperature of the Earth’s atmosphere generally decreases with altitude in the troposphere (normal lapse rate), increases in the stratosphere, decreases again in the mesosphere, and increases in the thermosphere. The temperature reaches a relative maximum around 0°C at the upper boundary of the stratopause.
The stratopause marks the boundary between the stratosphere and the mesosphere. In the stratosphere, temperature increases due to absorption of UV radiation by ozone. This increase stops at the stratopause, where the temperature is typically around 0°C before decreasing sharply in the mesosphere. The “normal lapse rate” (temperature decrease with height) applies to the troposphere and mesosphere. The question phrasing is slightly ambiguous (“rate… drops to 0°C at the”), but in the context of atmospheric layers and boundaries, it most likely refers to the temperature value reaching around 0°C at a boundary where the lapse rate changes direction.
The approximate temperatures at key boundaries are: Tropopause (top of troposphere): -50°C to -60°C (highly variable). Stratopause (top of stratosphere): around 0°C. Mesopause (top of mesosphere): -90°C to -100°C (coldest point). Temperature increases rapidly in the thermosphere.

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15. Which one of the following statements about temperature is correct?

Which one of the following statements about temperature is correct?

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Temperature decreases with height in the stratosphere.
Temperature is constant at different heights in the stratosphere.
Temperature increases with height in the troposphere at an average rate of 6.5 °C per kilometre.
Temperature decreases with height in the troposphere at an average rate of 6.4 °C per kilometre.
This question was previously asked in
UPSC NDA-2 – 2018
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Statement A is incorrect; temperature generally increases with height in the stratosphere due to the absorption of UV radiation by the ozone layer. Statement B is incorrect; temperature varies with height in the stratosphere, generally increasing. Statement C is incorrect; temperature decreases, not increases, with height in the troposphere. Statement D is correct; temperature decreases with height in the troposphere at an average rate, known as the lapse rate, which is approximately 6.5 °C per kilometer. The value 6.4 °C per kilometer is very close to this average rate and within acceptable variations.
This question tests knowledge of the temperature profiles in the different layers of the Earth’s atmosphere, specifically the troposphere and the stratosphere.
The troposphere is the lowest layer where most weather phenomena occur. The decrease in temperature with height is due to the fact that the troposphere is primarily heated by the Earth’s surface. The stratosphere lies above the troposphere, separated by the tropopause. The increase in temperature in the stratosphere is most pronounced in its upper part where ozone concentration is highest.

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16. Which one of the following gases is placed second in respect of abunda

Which one of the following gases is placed second in respect of abundance in the Earth’s atmosphere ?

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Oxygen
Hydrogen
Nitrogen
Carbon dioxide
This question was previously asked in
UPSC NDA-2 – 2017
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The Earth’s atmosphere is primarily composed of nitrogen (N₂) and oxygen (O₂). By volume, dry air contains approximately 78% nitrogen and 21% oxygen. The next most abundant gas is Argon (Ar), which makes up about 0.9%. Carbon dioxide (CO₂) is present in much smaller concentrations, around 0.04%. Hydrogen is present in trace amounts. Therefore, nitrogen is the most abundant gas, and oxygen is the second most abundant gas in the Earth’s atmosphere.
– Nitrogen (N₂) is the most abundant gas (approx. 78%).
– Oxygen (O₂) is the second most abundant gas (approx. 21%).
– Argon is the third most abundant (~0.9%).
The exact composition of the atmosphere can vary slightly with altitude, location, and the presence of moisture (water vapor is a significant component in humid air, but its concentration is highly variable). The balance of these gases is crucial for life on Earth and for regulating climate.

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17. Which of the following statements concerning temperature is/are correc

Which of the following statements concerning temperature is/are correct ?

  • 1. In winter season isotherms in Northern Hemisphere are more or less circular on continents
  • 2. Isotherms are parallel to latitude in Southern Hemisphere in oceans
  • 3. Minimum temperature during winter is recorded in Northern Canada

Select the correct answer using the code given below :

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1 and 2 only
1 and 3 only
1, 2 and 3
2 only
This question was previously asked in
UPSC NDA-2 – 2016
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Statement 1: In winter season, continents in the Northern Hemisphere become significantly colder than the surrounding oceans due to differential heating and cooling rates. This thermal contrast leads to isobars bending equatorward over land and poleward over oceans. While not perfectly circular, the isotherms tend to form closed patterns reflecting cold centers over the large landmasses, deviating from the zonal pattern. Compared to the Southern Hemisphere, the influence of land is pronounced, making the continental isotherms less parallel to latitudes and somewhat ‘circular’ around cold pools. This statement is generally considered correct in depicting the characteristic pattern.
Statement 2: The Southern Hemisphere is dominated by oceans. Oceans have a more uniform temperature distribution and heat/cool more slowly than land. As a result, isotherms in the Southern Hemisphere, particularly over vast oceanic areas and away from significant landmasses like Antarctica or the southern tips of continents, tend to be more regular and run broadly parallel to the lines of latitude. This statement is correct.
Statement 3: While Northern Canada experiences extremely low temperatures in winter, the absolute minimum temperatures on Earth during winter are typically recorded in places like Siberia (Russia) or Antarctica (Vostok Station holds the world record). Northern Canada is among the coldest regions, but it doesn’t necessarily record *the* minimum temperature globally. This statement is incorrect.
Isotherms are lines connecting points of equal temperature. Their patterns are influenced by latitude, altitude, distribution of land and water, ocean currents, and winds. Landmasses cause greater temperature extremes (hot summers, cold winters) compared to oceans, leading to bending of isotherms. The Southern Hemisphere’s oceanic dominance results in more zonal (latitude-parallel) temperature distribution.
The bending of isotherms over landmasses in winter (equatorward bend) and summer (poleward bend) is a direct consequence of the continentality effect. The Southern Hemisphere’s temperature patterns are simpler due to the lack of large east-west oriented landmasses at middle and high latitudes.

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18. Which one of the following pairs of properties of typical air masses i

Which one of the following pairs of properties of typical air masses is correct?

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Maritime Equatorial: Warm oceans in the equatorial zone
Maritime Polar: Warm oceans in the tropical zone
Continental Tropical: Less warm oceans in the tropical zone
Continental Polar: Moist oceans in the polar zone
This question was previously asked in
UPSC NDA-2 – 2015
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Air masses are classified based on their source region’s latitude (determining temperature: Equatorial (E), Tropical (T), Polar (P), Arctic/Antarctic (A)) and the surface type (determining moisture: Maritime (m) over oceans, Continental (c) over land). A Maritime Equatorial air mass forms over warm oceans in the equatorial region, making it warm and moist.
Air masses are classified by temperature (based on latitude of origin) and moisture content (based on surface type of origin). Maritime Equatorial (mE) air masses originate over warm equatorial oceans.
Let’s examine the other options:
B) Maritime Polar (mP): Forms over cold oceans in polar regions, typically cold and moist. The description “Warm oceans in the tropical zone” refers to mT (Maritime Tropical).
C) Continental Tropical (cT): Forms over warm land in the tropics, typically warm and dry. The description “Less warm oceans in the tropical zone” is incorrect.
D) Continental Polar (cP): Forms over cold land in polar regions, typically cold and dry. The description “Moist oceans in the polar zone” refers to mP (Maritime Polar).
Only option A accurately describes the characteristics and source region of a Maritime Equatorial air mass.

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19. Which one of the following gases is found in highest quantity in

Which one of the following gases is found in highest quantity in Exosphere?

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Hydrogen
Helium
Nitrogen
Oxygen
This question was previously asked in
UPSC NDA-2 – 2015
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The correct option is A, Hydrogen.
The exosphere is the outermost layer of the Earth’s atmosphere, extending upwards from the thermosphere and gradually thinning into space. The gases in this region are extremely sparse. Due to their very low atomic mass, hydrogen and helium are the most abundant constituents, as they are light enough to reach these high altitudes and potentially escape Earth’s gravity. Hydrogen is generally considered the dominant gas in the outermost reaches of the exosphere. Heavier gases like nitrogen and oxygen are much more concentrated in the lower atmospheric layers.
The exosphere is characterized by extremely low density and consists primarily of hydrogen, helium, and some heavier atoms and molecules near its base. This region marks the transition between Earth’s atmosphere and the vacuum of outer space. Temperature in the exosphere is highly variable and not representative of heat content due to the low particle density.

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20. Which of the following statements regarding air temperature is/are cor

Which of the following statements regarding air temperature is/are correct ?

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  • 1. Air temperature is measured at a standard height of 1.2 m (4.0 feet) above the ground surface.
  • 2. The average rate of temperature decrease with height is termed as the environmental temperature lapse rate.

Select the answer using the code given below :

1 only
2 only
Both 1 and 2
Neither 1 nor 2
This question was previously asked in
UPSC NDA-1 – 2024
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Statements 1 and 2 are correct.
Statement 1 is correct. Air temperature is typically measured at a standard height of about 1.2 to 1.25 meters (around 4 feet) above a representative surface, often inside a Stevenson screen to shield the thermometer from direct sunlight and precipitation. This standard height is used globally for consistent data collection. Statement 2 is correct. The environmental temperature lapse rate refers to the actual decrease in temperature with increasing height in the atmosphere at a given time and location. The average rate of temperature decrease in the troposphere is about 6.5°C per kilometer, often referred to as the standard or average lapse rate.
The lapse rate can vary significantly depending on atmospheric conditions. An adiabatic lapse rate refers to the change in temperature of a parcel of air as it rises or falls without exchanging heat with its surroundings (e.g., Dry Adiabatic Lapse Rate is about 9.8°C/km, Saturated Adiabatic Lapse Rate is typically less).

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