Exercises: The atmosphere

Air is made up of approximately 78% nitrogen, 21% oxygen, and 1% other gases (argon, carbon dioxide, water vapour, etc.). Order these components from highest to lowest proportion and represent the data using a simple bar chart.

You can do it on paper and send a photo with your answer.

The diagram shows the layers of the atmosphere (not drawn to scale).

1. a) Which layer is labelled with "?"?
2. b) In which layer do clouds form and storms occur?
3. c) Which gas forms an area in the layer labelled with "?" that absorbs ultraviolet radiation from the Sun?

State two functions of the atmosphere that make life on Earth possible, and briefly explain one of them.

Name the two most abundant gases in air and state their approximate proportion.

State whether these statements about the atmosphere are true or false and correct the false ones: air is made up only of oxygen; the troposphere is the layer where weather occurs; the exosphere is the layer closest to the surface.

Explain in your own words what atmospheric pressure is and reason why it is lower at the top of a mountain than at sea level.

A commercial aeroplane flies at about 11 km altitude and the International Space Station orbits at about 400 km. State in which layer of the atmosphere each one moves.

Name two differences between the troposphere and the outermost layers of the atmosphere, regarding air density and the phenomena that occur in them.

As you climb a mountain, the temperature drops, even though you are closer to the Sun. Explain which layer of the atmosphere this temperature drop corresponds to and reason why the peak of a high mountain is cold.

What is the ozone layer, which layer of the atmosphere is it located in, and why is its depletion a concern?

The Moon has virtually no atmosphere. State two consequences of this fact related to the functions that the atmosphere performs on Earth.

In the troposphere, temperature decreases with altitude, but in the stratosphere it increases. Relate this change of trend to the absorption of ultraviolet radiation by the ozone layer.

In high mountains, each breath provides less oxygen than at sea level. Explain how this fact is related to atmospheric pressure and why mountaineers need to acclimatise for days before climbing a very high summit.

The atmosphere is compared to a blanket wrapped around the Earth. Explain the resemblance: how it filters part of the solar radiation during the day and how it retains part of the heat during the night.

CFC gases, formerly used in aerosols and fridges, destroyed ozone and were banned by the Montreal Protocol. Explain the risk their use posed and why that agreement is considered a success of international cooperation.

Water vapour is a variable component of air. Explain what happens when a mass of humid air rises and cools down, and relate it to the formation of clouds.

A rocky exoplanet similar to Earth has been discovered that receives comparable stellar radiation, but whose atmospheric analysis indicates that it lacks an ozone layer in its middle region and does not retain water vapour in its lower layers. Reasonably justify which protective and regulating functions fulfilled by Earth's troposphere and stratosphere would be absent on that planet, and predict two critical consequences for the viability of life on its surface.

A classmate claims that it is absurd to attribute global warming to carbon dioxide ($\text{CO}_2$), since making up only 0,04 % of the air, nitrogen (78 %) and oxygen (21 %) must be the real culprits responsible for trapping heat. Refute their position by explaining the differential behaviour of these gases toward solar radiation and terrestrial infrared radiation, and predict what would happen to the planet's average temperature if $\text{CO}_2$ and the other greenhouse gases were to disappear entirely.

A weather balloon records the following temperatures as it rises: 15 °C at the surface, −50 °C at an altitude of 10 km, 0 °C at 45 km, and −80 °C at 70 km. State which layers of the atmosphere it passes through in each section and explain the change in trend observed in the data.

In the troposphere, air mixes easily through convection currents because it cools with altitude. In contrast, in the stratosphere, the temperature rises from about −56 °C at 15 km to almost 0 °C at 50 km. Justify the physical cause of this warming with altitude and predict what consequences this thermal inversion has on air stability and storm formation, explaining why long-distance commercial flights prefer to travel at the lower boundary of this layer.

A student argues that, since the air in the troposphere is much denser and contains thousands of times more atoms to emit light when excited, polar auroras should form near the ground rather than hundreds of kilometres up. Refute their hypothesis by justifying why this phenomenon only triggers in the thermosphere/ionosphere, and predict what risks would exist for the biosphere if the atmosphere did not act as a shield against these high-energy solar particles, and what risks the geomagnetic storms caused by these solar events pose to terrestrial power grids.

A hiker hermetically seals a flexible plastic bottle at the summit of a mountain at an altitude of 3000 m. Upon descending to the beach, they observe that the bottle has deformed and is completely crushed. Justify this event by refuting the idea that "air has no weight" based on the concept of mass and the air column, and predict with reasoning what would happen to that same bottle if it were sealed at the beach and carried up to the summit again.

Mars has an atmosphere about a hundred times thinner than Earth's and made almost entirely of $\text{CO}_2$. Reason why temperature differences between day and night on Mars are much greater than on Earth, even though $\text{CO}_2$ is a greenhouse gas.

A student claims that it is absurd that meteoroids disintegrate in the mesosphere because "at an altitude of 80 km the air is at −90 °C and is nearly a vacuum, so they should burn much lower down, in the troposphere, where there is more air and it is warmer". Refute their reasoning by explaining the physical cause of the heating of meteoroids at that altitude, and predict what consequences it would have for the Earth's crust and living organisms if the atmosphere lacked a mesosphere.