The Atmosphere Archives

41. In the Hadley cell thermal circulation, air rises up and finally desce

In the Hadley cell thermal circulation, air rises up and finally descends at

intertropical convergence zone

doldrums

subtropical high-pressure cells

equatorial troughs

This question was previously asked in

UPSC CDS-1 – 2020

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The correct answer is C) subtropical high-pressure cells.

The Hadley cell is a large-scale atmospheric circulation pattern that dominates the tropical atmosphere. Warm, moist air rises at the Intertropical Convergence Zone (ITCZ), located near the equator, driven by intense solar heating (creating a low-pressure area). This rising air cools, loses moisture (leading to tropical rainfall), and then flows poleward at high altitudes. Around 30 degrees latitude North and South, the air cools further, becomes denser, and descends towards the surface. This descending air is dry and leads to high-pressure areas known as the subtropical high-pressure cells. This descent inhibits cloud formation, resulting in clear skies and arid conditions often associated with major deserts found around these latitudes.

The Doldrums refer to the low-pressure region near the equator associated with the ITCZ, where air rises. Equatorial troughs are also low-pressure regions around the equator. Air rises, not descends, in these regions.

42. Consider the following constituent gases of the atmosphere : 1. Argo

Consider the following constituent gases of the atmosphere :

1. Argon
2. Neon
3. Helium
4. Carbon dioxide

Which one of the following is the correct ascending sequence of the above gases in terms of the volume percentage?

1-3-2-4

1-4-2-3

4-2-3-1

2-4-1-3

This question was previously asked in

UPSC CDS-1 – 2018

Download PDF Attempt Online

The question asks for the correct ascending sequence of atmospheric gases by volume percentage. Let’s list the approximate volume percentages of the given gases in dry air:
1. Argon (Ar): ~0.93%
2. Neon (Ne): ~0.0018%
3. Helium (He): ~0.0005%
4. Carbon dioxide (CO₂): ~0.04% (This value can slightly vary depending on the source/year, but its relative position is stable).
The correct ascending order by volume percentage is Helium (3) < Neon (2) < Carbon dioxide (4) < Argon (1). This corresponds to the sequence 3-2-4-1. Looking at the options provided: A) 1-3-2-4 (Ar, He, Ne, CO2) - Incorrect B) 1-4-2-3 (Ar, CO2, Ne, He) - This sequence (0.93%, 0.04%, 0.0018%, 0.0005%) represents the correct *descending* order of the gases. C) 4-2-3-1 (CO2, Ne, He, Ar) - Incorrect D) 2-4-1-3 (Ne, CO2, Ar, He) - Incorrect Based on standard scientific values, none of the options represent the correct ascending sequence (3-2-4-1). However, option B presents the correct descending sequence (1-4-2-3). It is highly probable that there is an error in the question asking for "ascending" instead of "descending", or a misprint in the options. Given that a forced choice from the options is required and B is the correct descending order, it is often the case in such flawed questions that the option matching the reverse order is the intended answer due to a mistake in the question phrasing. Assuming this likely error, we select B.

– The major components of dry air are Nitrogen (~78%), Oxygen (~21%), and Argon (~0.93%).
– Carbon dioxide, Neon, and Helium are trace gases, present in much smaller quantities.
– The order of abundance for the given gases is Argon > Carbon dioxide > Neon > Helium.

The percentages of atmospheric gases are generally constant in the lower atmosphere, except for variable gases like water vapor and carbon dioxide. The exact percentage of CO2 has been increasing due to human activities, but its relative abundance compared to Ar, Ne, and He remains in the same order.

43. Which of the following causes adiabatic temperature changes in

Which of the following causes adiabatic temperature changes in atmosphere?

Deflection and advection

Latent heat of condensation

Expansion and compression of the air

Partial absorption of solar radiation by the atmosphere

This question was previously asked in

UPSC CDS-1 – 2018

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Adiabatic temperature changes occur when the temperature of an air parcel changes due to expansion or compression without any heat exchange with its surroundings. When air rises, it expands due to lower atmospheric pressure, and this expansion causes it to cool (adiabatic cooling). When air sinks, it is compressed by higher pressure, and this compression causes it to warm (adiabatic warming).

Adiabatic processes involve temperature changes caused by work done during expansion or compression of air, not by heat transfer.

Deflection and advection involve horizontal air movement. Latent heat exchange (like condensation or evaporation) involves the release or absorption of heat, making the process non-adiabatic. Absorption of solar radiation is a form of heat transfer.

44. The incident solar radiation is trapped by constituents of the atmosph

The incident solar radiation is trapped by constituents of the atmosphere and reflect it partly towards the Earth as

microwaves

thermal infrared rays

ultraviolet rays

shortwave radiation

This question was previously asked in

UPSC Geoscientist – 2022

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The Earth absorbs incoming shortwave solar radiation and re-emits it as longwave radiation, primarily in the form of thermal infrared rays. Certain atmospheric constituents, known as greenhouse gases, absorb this outgoing infrared radiation and re-emit it in all directions, including back towards the Earth’s surface. This re-emitted radiation is thermal infrared.

– Incoming solar radiation is mostly shortwave (visible, UV, near-IR).
– Outgoing Earth radiation is mostly longwave (thermal infrared).
– Greenhouse gases absorb longwave radiation.
– The greenhouse effect involves the re-emission of absorbed longwave radiation back towards the surface.

Microwaves have longer wavelengths than infrared. Ultraviolet rays are part of the incoming solar radiation spectrum. Shortwave radiation refers generally to incoming solar energy. The trapped and re-directed energy from the atmosphere to the surface is specifically in the thermal infrared range.