The atmosphere

Name the layers of the atmosphere in order from Earth's surface outwards into space and state a characteristic feature of each.

State the main composition of air (the two dominant gases with their approximate proportions) and name two trace gases whose variation is of major environmental importance.

What is the tropopause and at what approximate altitude is it located? Discuss why commercial aircraft fly close to it (stability, less turbulence, lower consumption).

Explain what atmospheric pressure is, with which instrument it is measured and in which units, and discuss how and why it varies with altitude (what does a barometric altimeter actually measure?).

Explain what the lapse rate (vertical thermal gradient) of the troposphere is and what a thermal inversion is, relating the latter to episodes of trapped pollution over major cities in winter.

An atmospheric sounding taken over a plain at midday records $28\ \text{°C}$ at $0\ \text{m}$ altitude; $19\ \text{°C}$ at $1000\ \text{m}$; $14\ \text{°C}$ at $2000\ \text{m}$; $11\ \text{°C}$ at $3000\ \text{m}$; and $-56\ \text{°C}$ at $12\ \text{km}$ (tropopause level).

1. a) Calculate the environmental vertical temperature gradient (environmental lapse rate, ELR) in $\text{°C/100 m}$ for each of the first three sections ($0-1000\ \text{m}$, $1000-2000\ \text{m}$, and $2000-3000\ \text{m}$) and compare them with the standard average tropospheric lapse rate ($0{,}65\ \text{°C/100 m}$).
2. b) A parcel of dry air at $30\ \text{°C}$ rises due to thermal buoyancy, cooling at the dry adiabatic lapse rate ($\text{DALR} = 1\ \text{°C/100 m}$). Determine the exact altitude at which it will reach neutral buoyancy and state whether the atmosphere is unstable or stable in each of the sections it traverses.
3. c) Predict what will happen to the buoyancy of a storm cloud rising with convective force when its top reaches $12\ \text{km}$ and penetrates into the stratosphere. Based on this, justify why cumulonimbus clouds develop a flat, anvil-shaped morphology at that level.

Outline in words the general circulation of the atmosphere (Hadley cell, Intertropical Convergence Zone, subtropical anticyclones) and use it to explain the climatic contrast between the humid north and the arid south-east of the Iberian Peninsula.

Explain the mechanism of the daytime sea breeze and of the night-time land breeze (differential warming and cooling of land and sea) and discuss what effect they have on the pollution of a coastal city (do they carry it out to sea or recirculate it?).

Explain the Foehn effect: what happens to a mass of humid air as it climbs a mountain range (cooling, condensation, rain) and as it descends on the other slope (drier and warmer air), and relate it to the contrast between the Cantabrian coast and the Meseta.

What is the relative humidity of the air? Explain why the same amount of water vapour gives different relative humidity values depending on the temperature, and relate it to the formation of dew as the night cools.

Explain why the sky looks blue at midday and reddish at sunset, resorting to the scattering of light by the molecules of the air and to the longer path the light travels when the Sun is low.

Distinguish between a warm front and a cold front: which air mass advances in each case, which clouds and what type of precipitation (persistent or intense and brief) each brings, and what temperature change an observer notices after they pass.

Name four primary atmospheric pollutants (sulphur dioxide, nitrogen oxides, suspended particles, carbon monoxide) and indicate one main source of each.

Describe the function of the stratospheric ozone layer, what substances destroyed it (CFCs), and why the Montreal Protocol is considered the greatest success of environmental diplomacy.

Distinguish between classical or London-type smog (a mixture of smoke and fog with $\text{SO}_2$ and particles) and Los Angeles-type photochemical smog (ozone and secondary compounds formed by sunlight), indicating the season and the typical conditions of each.