The Atmosphere Archives

1. Which of the following is not among the conditions ideal for inversion

Which of the following is not among the conditions ideal for inversion of temperature?

A long winter night

Clear skies

Still air

Low air pressure near the ground surface

This question was previously asked in

UPSC CBI DSP LDCE – 2023

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Low air pressure near the ground surface is not an ideal condition for temperature inversion; rather, it is generally associated with conditions that prevent inversion.

Temperature inversion is a meteorological phenomenon where temperature increases with increasing altitude, contrary to the usual decrease. Conditions ideal for inversion are typically associated with stable atmospheric conditions that prevent vertical mixing:
1. **Long Winter Night:** Allows for maximum radiative cooling of the ground surface.
2. **Clear Skies:** Clouds absorb and re-emit outgoing radiation, reducing surface cooling. Clear skies allow for efficient outgoing terrestrial radiation and cooling of the ground and the air directly above it.
3. **Still Air:** Wind facilitates mixing of air layers, which disrupts the formation of an inversion layer. Calm or still air allows cold, dense air to accumulate near the surface.
4. **Snow Cover:** A snow-covered surface is an excellent radiator and reflector, enhancing cooling.
5. **Topography:** Valleys and low-lying areas can trap cold air, leading to strong inversions.

Low air pressure near the ground surface is generally associated with rising air (cyclonic conditions) which promotes mixing and instability, opposing the conditions needed for inversion. High pressure is typically associated with sinking air and stable conditions, which favour inversions.

Surface temperature inversions often occur on clear, calm nights when the ground cools rapidly through radiation. The air in contact with the ground cools more than the air above it, leading to the inversion. Inversions can trap pollutants near the surface, leading to reduced air quality.

2. Consider the following statements : Statement-I : Thickness of the t

Consider the following statements :

Statement-I :
Thickness of the troposphere at the equator is much greater as compared to poles.
Statement-II :
At the equator, heat is transported to great heights by strong convectional currents.

Which one of the following is correct in respect of the above statements ?

Both Statement-I and Statement-II are correct and Statement-II explains Statement-I

Both Statement-I and Statement-II are correct, but Statement-II does not explain Statement-I

Statement-I is correct, but Statement-II is incorrect

Statement-I is incorrect, but Statement-II is correct

This question was previously asked in

UPSC IAS – 2024

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Statement-I is correct. The thickness of the troposphere varies with latitude and season, being greatest at the equator (around 16-18 km) and thinnest at the poles (around 8-10 km).
Statement-II is correct. At the equator, high solar insolation leads to intense heating of the surface and lower atmosphere, resulting in strong convectional currents. These rising air currents transport heat and moisture upwards to great heights, pushing the boundary of the troposphere (tropopause) higher. At the poles, there is less heating and weaker convection, resulting in a lower tropopause.
Statement-II provides the physical mechanism (strong convection due to heat transport) that explains why the troposphere is thicker at the equator compared to the poles. Therefore, both statements are correct, and Statement-II explains Statement-I.

The thickness of the troposphere is primarily controlled by temperature and convection. Warmer temperatures and stronger convection lead to a higher tropopause.

The troposphere is the lowest layer of Earth’s atmosphere where most weather occurs. The tropopause is the boundary between the troposphere and the stratosphere.

3. Consider the following statements: Jet streams occur in the Northern

Consider the following statements:

Jet streams occur in the Northern Hemisphere only.
Only some cyclones develop an eye.
The temperature inside the eye of a cyclone is nearly 10°C lesser than that of the surroundings.

Which of the statements given above is/are correct?

1 only

2 and 3 only

2 only

1 and 3 only

This question was previously asked in

UPSC IAS – 2020

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Only statement 2 is correct. Jet streams occur in both hemispheres, and the eye of a tropical cyclone is typically warmer than its surroundings.

Statement 1 is incorrect. Jet streams are fast-flowing, narrow, meandering air currents found in the atmospheres of planets, including Earth. On Earth, major jet streams are located in the upper atmosphere (tropopause) of both the Northern Hemisphere and the Southern Hemisphere.
Statement 2 is correct. Only tropical cyclones, which are intense low-pressure systems, can develop a feature known as an ‘eye’. This eye is a relatively calm, clear region at the center of the storm. Not all cyclones, particularly weaker ones or extra-tropical cyclones, develop a clearly defined eye.
Statement 3 is incorrect. The eye of a tropical cyclone is characterized by subsiding air, which leads to warming. The temperature inside the eye is typically warmer than the surrounding eyewall, sometimes by several degrees Celsius, not lesser by 10°C.

Jet streams play a significant role in influencing weather patterns. The eye of a tropical cyclone is a defining feature of mature, intense storms and is surrounded by the eyewall, which is the region of strongest winds and heaviest rainfall.

4. During a thunderstorm, the thunder in the skies is produced by the m

During a thunderstorm, the thunder in the skies is produced by the

meeting of cumulonimbus clouds in the sky
lightning that separates the nimbus clouds
violent upward movement of air and water particles

Select the correct answer using the codes given below.

1 only

2 and 3

1 and 3

None of the above produces the thunder

This question was previously asked in

UPSC IAS – 2013

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Thunder is produced by the rapid expansion of air heated by lightning. Option 2 mentions lightning, which is the direct cause. Option 3, the violent upward movement of air and water particles (convection), is a necessary process within a thunderstorm that leads to charge separation and thus lightning. While not the direct producer of the *sound*, it is essential for the occurrence of lightning, which in turn produces thunder. Considering the options, 2 and 3 together represent the phenomena directly linked to the generation of thunder within a thunderstorm.

Lightning is an electrical discharge within a thunderstorm cloud or between the cloud and the ground. The intense heat from the lightning channel causes the surrounding air to expand rapidly, creating a shockwave that we hear as thunder. The violent upward movement of air and water particles (updrafts) within cumulonimbus clouds leads to the collision of particles, charge separation, and eventually the buildup of electrical potential that results in lightning. Thus, updrafts are integral to the process leading to lightning and, consequently, thunder.

Statement 1, the meeting of cumulonimbus clouds, is not a direct cause of thunder. Cumulonimbus clouds are the type of clouds where thunderstorms occur, but their meeting doesn’t produce the sound. While statement 2’s phrasing “lightning that separates the nimbus clouds” is awkward, it points to lightning as the cause. Statement 3 describes the process of convection which is a prerequisite for severe thunderstorms and lightning. In the context of MCQ options, 2 and 3 are the most relevant phenomena listed that lead to thunder.

5. Which one of the following statements is correct with reference to nor

Which one of the following statements is correct with reference to normal lapse rate?

Temperature is highest at ground level and decreases with increasing altitude.

Temperature is lowest at ground level and increases with increasing altitude.

Temperature remains stable with increasing altitude.

Temperature first increases with increasing altitude and gradually starts decreasing.

This question was previously asked in

UPSC CAPF – 2022

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The normal lapse rate refers to the rate at which atmospheric temperature decreases with an increase in altitude. In the troposphere, temperature is generally highest at or near the ground level and decreases as you move higher.

The normal lapse rate is approximately 6.5°C per kilometer (or 3.5°F per 1000 feet) in the troposphere. This decrease occurs because the atmosphere is primarily heated by the Earth’s surface.

There are instances where temperature increases with altitude, known as temperature inversion. These inversions occur under specific atmospheric conditions but are not the normal lapse rate.

6. The lowest temperature is observed/ recorded in which one of the follo

The lowest temperature is observed/ recorded in which one of the following layers of the atmosphere?

Stratosphere

Mesosphere

Thermosphere

Troposphere

This question was previously asked in

UPSC CAPF – 2018

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The lowest temperature in the atmosphere is observed/recorded in the Mesosphere.

– The atmosphere is divided into several layers based on temperature profiles: Troposphere, Stratosphere, Mesosphere, Thermosphere, and Exosphere.
– In the Troposphere, temperature generally decreases with altitude.
– In the Stratosphere, temperature increases with altitude due to the absorption of ultraviolet radiation by the ozone layer.
– In the Mesosphere, temperature again decreases with altitude. The coldest temperatures in the Earth’s atmosphere, often dropping below -90°C (-130°F), are found at the top of the mesosphere (the mesopause).
– In the Thermosphere, temperature increases sharply with altitude due to the absorption of high-energy solar radiation.

The mesopause, the boundary between the mesosphere and the thermosphere, is typically the coldest region of the entire atmosphere. Meteors often burn up in the mesosphere.

7. In mid-latitude regions, the diurnal variation in weather is due to

In mid-latitude regions, the diurnal variation in weather is due to

raising air/convection

sinking air/conduction

advection

radiation

This question was previously asked in

UPSC CAPF – 2018

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In mid-latitude regions, the primary driver of diurnal variation in weather is radiation.

Diurnal variation refers to the changes in weather elements (like temperature, humidity, wind, cloudiness) that occur over a 24-hour cycle. This cycle is fundamentally driven by the daily pattern of incoming solar radiation and outgoing terrestrial radiation. During the day, solar radiation heats the surface and atmosphere; at night, the Earth cools by emitting long-wave radiation. This daily heating and cooling cycle directly causes the diurnal temperature range and indirectly influences other diurnal patterns like convection (daytime heating leads to rising air and potential thunderstorms) or fog formation (nighttime cooling leads to condensation). While convection, conduction, and advection play roles in weather, radiation is the primary cause of the day-night difference that defines diurnal variation.

Advection, the horizontal movement of air masses, is a major cause of *weather changes* over periods longer than a day (synoptic scale), but the recurring daily cycle is primarily governed by the Earth’s rotation relative to the sun and the resulting radiative balance.

8. Which one of the following is NOT a favourable condition for occurrenc

Which one of the following is NOT a favourable condition for occurrence of a thunderstorm ?

Conditional and convective instability

Adequate supply of moisture in the lower atmosphere

Advection of cold dry air in the lower troposphere and warm moist air in the upper troposphere

A synoptic situation of low level convergence and upper level divergence

This question was previously asked in

UPSC CAPF – 2017

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Thunderstorms require unstable atmospheric conditions, a source of moisture, and a lifting mechanism. Statement A describes conditional and convective instability, which is essential for strong vertical air movement. Statement B highlights the need for adequate moisture, which provides latent heat when it condenses, fueling the storm, and also provides the source for precipitation. Statement D describes a synoptic situation that leads to lifting (low-level convergence forces air up) and aids thunderstorm development (upper-level divergence helps remove rising air, maintaining ascent). Statement C describes a stable atmospheric condition where cold, dense air is below warm, less dense air. This stratification inhibits vertical air movement and is unfavourable for thunderstorm development.

Thunderstorms form in unstable atmospheric conditions where warm, moist air rises. A stable atmosphere with cold air below warm air inhibits this process.

The key ingredients for a thunderstorm are moisture, instability, and a lifting mechanism (like fronts, convergence lines, orographic lift, or simple heating). Instability is often provided by a steep vertical temperature lapse rate, where temperature decreases rapidly with height. Advecting cold dry air below warm moist air would create an inversion or stable layer, suppressing convection.

9. Which one of the following layers of atmosphere has high concentration

Which one of the following layers of atmosphere has high concentration of ions ?

Stratosphere

Exosphere

Thermosphere

Troposphere

This question was previously asked in

UPSC CAPF – 2016

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The Thermosphere is the layer of the atmosphere that has a high concentration of ions.

The Thermosphere contains a region called the ionosphere, where solar radiation causes atoms and molecules to become ionized (gain or lose electrons), creating a high concentration of ions and free electrons. This ionization is responsible for phenomena like the aurora borealis/australis and facilitates the reflection of radio waves used for long-distance communication.

The atmosphere is divided into several layers based on temperature profiles: Troposphere, Stratosphere, Mesosphere, Thermosphere, and Exosphere.
– Troposphere: Lowest layer, where weather occurs.
– Stratosphere: Contains the ozone layer. Temperature increases with altitude.
– Mesosphere: Temperature decreases with altitude. Meteors burn up here.
– Thermosphere: Temperature increases significantly with altitude due to absorption of high-energy solar radiation. It includes the ionosphere.
– Exosphere: Outermost layer, where the atmosphere thins out into space.

10. Under which of the following condition(s) the occluded fronts are crea

Under which of the following condition(s) the occluded fronts are created ?

1. When the front remains stationary
2. When cold air mass moves to warm air mass
3. When warm air mass moves to cold air mass
4. When an air mass is fully lifted above the land surface

Select the correct answer using the code given below :

1 and 2

2 and 3

3 and 4

4 only

This question was previously asked in

UPSC CAPF – 2015

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The correct answer is D, stating that occluded fronts are created when an air mass is fully lifted above the land surface.

– A front is a boundary between two different air masses.
– Occluded fronts typically form when a faster-moving cold front overtakes a warm front.
– As the cold front catches up to the warm front, the colder, denser air behind the cold front lifts the warmer, less dense air of the warm sector completely off the ground.
– The defining characteristic of an occluded front is that the warm air mass is no longer in contact with the surface; it has been lifted entirely aloft by the converging colder air masses (either cold occlusion where the air behind the cold front is colder than the air ahead of the warm front, or warm occlusion where the air behind the cold front is warmer than the air ahead of the warm front).
– Statement 4 accurately describes this condition of the warm air mass being lifted above the surface, which is central to the formation and nature of an occluded front.
– Statements 1, 2, and 3 describe conditions related to stationary fronts (1), cold fronts (2), and warm fronts (3), respectively, but not the specific mechanism or state characteristic of an occluded front.

Occluded fronts are often associated with mature low-pressure systems (cyclones) and can bring complex weather patterns, including precipitation and changes in wind direction and temperature. The process of occlusion marks the beginning of the dissipation of the cyclone as the warm air is lifted and separated from its source.