Heating and cooling of the atmosphere

The correct answer is D. Carbon dioxide makes up only a small fraction of the atmosphere, but a small amount can still have major effects. Green plants take in carbon dioxide during photosynthesis and, using light energy and water, make food such as glucose while releasing oxygen. Carbon dioxide also absorbs some outgoing infrared radiation from Earth, so it participates in the planet’s heat balance. This does not mean that more carbon dioxide is always beneficial; a large increase can strengthen warming and affect climate. Option A is wrong because carbon dioxide is a gas, not the main rock. Option B is wrong because an ocean tide is the rise and fall of sea level caused mainly by gravitational effects. Option C is wrong because a glacier is a mass of ice. Only D gives the relevant biological and atmospheric reasons. Memory cue: CO₂ is “plant food and heat-balance gas.”

Direct answer: Option B is correct. The main reason is the water cycle. Solar energy heats oceans, seas, lakes, rivers, wet soil and other surface water, causing evaporation. Plants also release water vapour through transpiration. Since these sources are concentrated at or near Earth’s surface, the lower atmosphere receives most of the water vapour. As moist air rises, it generally cools; cooling can lead to condensation, cloud formation and precipitation, so water vapour usually decreases with height. A is unrelated: incoming meteoroids do not supply the atmosphere’s water vapour. C is false because nitrogen is distributed through the atmosphere rather than remaining only below. D is also false; argon can move with air and has no role in explaining the vertical distribution of water vapour. Memory cue: surface water plus plants supply moisture from below.

Direct answer: The polar troposphere is lower because temperatures are lower and convection is weaker, so option A is correct. The poles receive less concentrated solar heating than the equator. The surface and nearby air therefore remain colder. Cold air expands less and does not rise through strong, deep convection as warm equatorial air does. As a result, the tropopause—the top of the troposphere—lies at a lower altitude over the poles. Option B is wrong because the atmosphere is not made only of ozone there. Option C is wrong because gravity acts at the poles just as it does elsewhere on Earth. Option D is irrelevant: meteors and their behaviour do not determine the normal height of the troposphere. The contrast to remember is warm, strongly convecting air in the tropics versus cold, weaker convection near the poles. Memory cue: “cold air, shallow troposphere.”

The correct answer is C: temperature generally decreases with height in the mesosphere. It reaches very low values near the mesopause, the boundary above the mesosphere. In the thermosphere above, the general temperature trend reverses and increases with height.

The direct answer is B: the thermosphere. This very high layer absorbs much of the Sun’s energetic ultraviolet and X-ray radiation. Absorption gives its few gas particles high kinetic energy, so the measured temperature can become very high even though the air is extremely thin. A is wrong because the troposphere is mainly the lower weather layer and is heated largely from Earth’s surface. C is wrong because the stratosphere is especially associated with ozone absorption of ultraviolet radiation, but the question asks for the upper layer strongly affected by high-energy solar radiation. D is wrong because ‘lower cloud zone’ is not a standard named atmospheric layer. Memory cue: thermosphere is thin but hot because it absorbs energetic solar radiation.

The correct answer is A. In the stratosphere, temperature generally increases with altitude because ozone absorbs some of the Sun's ultraviolet radiation and converts that energy into heat. The other options describe neither the stratosphere's temperature pattern nor its defining characteristics.

The correct answer is A. The normal lapse rate describes the general decrease in air temperature as altitude increases in the troposphere. Its average value is about 6.5°C per kilometre, though the actual rate varies with conditions and location.

Correct answer: B. Strong solar heating over the equator warms the air, causing vigorous rising motion and convection. This makes the troposphere extend farther upward, so its upper boundary—the tropopause—is generally higher there than over the poles.

Correct answer: D. Ozone in the stratosphere absorbs ultraviolet radiation from the Sun, warming the surrounding air. This absorption causes temperature to generally rise with height through much of the stratosphere.

A is correct: temperature generally decreases as altitude increases through the mesosphere, reaching very low values near the mesopause. This is the opposite of the general temperature trend in the thermosphere above it.

B is correct. “Thermo” refers to heat, and temperatures in the thermosphere are generally high because its sparse gases absorb high-energy solar radiation. The air is extremely thin, so this does not mean it would feel as hot as a hot surface at ground level.

Answer: B, because high-energy solar radiation is absorbed there. The thermosphere contains very thin gas, but its particles can absorb energetic ultraviolet and X-ray radiation from the Sun. This absorption gives the particles very high average kinetic energy, which is why the measured temperature can be extremely high. A very important distinction is that temperature measures particle energy, while the thinness of the air affects how much heat it can transfer. Thus a person would not necessarily feel intense heat there as they would in dense hot air. A is wrong because the thermosphere does not contain a soil layer. C is wrong because heavy rainfall occurs in the lower atmosphere, especially the troposphere. D is wrong because ocean water is at Earth’s surface, not in the thermosphere. Memory cue: thermosphere means high particle energy, not dense, comfortable heat.

The correct answer is A. In the troposphere, temperature generally decreases with altitude. The air is heated mainly from Earth's surface; as air rises into lower pressure, it expands and cools. This is why mountain areas are usually cooler than nearby lowlands, although local conditions can cause exceptions.

A is correct. Temperature generally decreases with height through the mesosphere, reaching very low values near its upper boundary, the mesopause. The temperature then rises with height in the thermosphere above it, so B does not describe the mesosphere.

B is correct. In the troposphere, temperature generally decreases with height because the layer is heated mainly from Earth’s surface. Rising air expands as pressure falls and usually cools. The average environmental lapse rate is about 6.5°C per kilometre, though actual conditions vary.

A is correct. Earth’s surface absorbs solar energy and warms the air above it, mainly by emitting infrared radiation and transferring heat through contact and convection. This surface-driven heating is central to energy exchange in the troposphere.

Earth absorbs solar energy and emits longwave radiation which heats the atmosphere. Exam tip: remember the atmosphere is heated mainly from below.

A heated surface emits longwave radiation. Exam tip: separate incoming solar energy from outgoing terrestrial energy.

Radiation from the Sun is mainly shortwave radiation. The Sun has a very high temperature, so it emits energy largely in shorter wavelengths, including visible light and ultraviolet radiation. This incoming solar energy is called insolation. After the Earth’s surface absorbs it, the warmed surface emits energy back toward the atmosphere mainly as longwave, or terrestrial, radiation because the Earth is much cooler than the Sun.

Thus, option B, shortwave, is correct. Longwave radiation is mainly associated with heat emitted by the Earth and its surface, not with the main incoming solar beam. Seismic radiation involves vibrations within the Earth, and acoustic radiation is related to sound waves. The simple sequence is: Sun sends mostly shortwave energy; Earth absorbs it and later releases mostly longwave energy.

Radiation can occur without a medium. Exam tip: sunlight reaching through space is a simple example.

In conduction heat passes through direct contact. Exam tip: link warming of air touching the ground with conduction.

The heated ground warms the air in contact with it. Exam tip: explain lower air warming through conduction and terrestrial radiation.

Warm air rises and cooler air sinks causing convection. Exam tip: call vertical air movement convection.

In advection heat is transferred by horizontal air movement. Exam tip: link temperature change by winds with advection.

Air from the sea can replace warmer air over land. Exam tip: treat this as a simple example of advection.