Atmospheric Composition and Structure - Review Flashcards

Flashcards cover the key concepts of atmospheric composition, structure, layers, and gas sources/sinks as presented in the notes.

What is the Atmosphere?

The envelope of gases that surrounds Earth; it is smaller relative to the size of the planet and it provides oxygen and shields us from harmful radiation.

What would Earth be like without the atmosphere?

It would be sterile like the Moon; all Earth’s water would have boiled away; extreme day and night temperatures would be unpreventable.

What is the Karman line and its significance?

Defined at 100 km (62 miles) as the top of the atmosphere; above it the air is extremely thin and lift is hard to achieve.

Where is most of the atmosphere's mass located relative to the Karman line?

Over 99.9% lies below the Karman line.

Where is half of the atmosphere's mass located?

Between the Earth’s surface and about 3.5 miles (5.6 km) altitude.

How far above Earth does the atmosphere cease to exist according to the notes?

By about 120,000 miles above the Earth’s surface.

What are the two chemical-based layers of the atmosphere?

Homosphere (below about 80 km) and Heterosphere (above about 80 km).

What altitude marks the start of the Homosphere?

Below 80 km.

What is a key characteristic of the Homosphere?

The gases are well mixed and the proportions are essentially the same at all altitudes.

Which layers make up the Homosphere?

Troposphere, Stratosphere, and Mesosphere.

Where does the Heterosphere begin?

Above about 80 km.

What is true about gas distribution in the Heterosphere?

Gases are not well mixed; proportions are unequal; the lightest gases are in the upper regions and the heaviest in the lower regions.

What are the two major categories of atmospheric gases?

Permanent gases and Variable (trace) gases.

Which two gases make up over 99% of Earth’s atmosphere?

Nitrogen (N2) and Oxygen (O2).

Name some permanent gases and their approximate percentages by volume.

Argon ~0.93%, Neon ~0.0018%, Helium ~0.0005%, Hydrogen ~0.00005%, Xenon ~0.000009% (in addition to N2 and O2).

What are variable gases?

Gases that exist in extremely small quantities and vary in proportion; examples include water vapor, CO2, CH4, and O3.

Which gases are greenhouse gases listed in the notes?

Water vapor (H2O), Carbon dioxide (CO2), Methane (CH4), and Ozone (O3).

What is a 'source' in atmospheric gas context?

A source describes how a gas could enter the atmosphere (e.g., from lakes/oceans or chemical reactions).

What is a 'sink' in atmospheric gas context?

A sink describes the pathway through which a gas could exit the atmosphere.

What are the primary sources of Nitrogen (N2) in the atmosphere?

Volcanic eruptions, decaying and burning organic matter, and weathering of rocks.

What is the primary source of Oxygen (O2) in the atmosphere?

Photosynthesis.

What are the sources and sinks for Water vapor (H2O)?

Sources include evaporation from oceans, photosynthesis, and volcanic eruptions; sinks include condensation and deposition.

What are the sources and sinks for Carbon dioxide (CO2)?

Sources include volcanic eruptions, decay of organic matter, respiration, burning of fossil fuels; sinks include photosynthesis, oceans, and chemical reactions.

What are the sources and sinks for Methane (CH4)?

Sources include anaerobic bacterial decomposition; sinks include absorption by ultraviolet radiation.

What are the sources and sinks for Nitrous oxide (N2O)?

Sources include soil bacterial processes, agricultural and industrial activities, burning fossil fuels; sinks include absorption by ultraviolet radiation.

What are the sources and sinks for Ozone (O3)?

Sources include ultraviolet radiation and burning fossil fuels; sinks include absorption and breakdown by ultraviolet radiation.

What are the sources and sinks for CFCs and HFCs?

Sources are anthropogenic; sinks are absorption and breakdown by ultraviolet radiation.

What are aerosols?

Microscopic solid or liquid particles suspended in the atmosphere (dust, pollen, spores, bacteria, pollutants); can be health hazards when concentrated.

How do air and ocean fluids differ in density and flow?

Air is mostly N2 and O2 and is less dense with molecules farther apart; oceans are dense with water molecules; air flows in currents, water flows in streams.

What is air pressure and how does it vary with altitude?

The force exerted by air molecules on surfaces; greatest at sea level and decreases with altitude; wind results from pressure differences.

What is air density and how does it relate to height?

Density is the mass per unit volume; it increases with air pressure; the density is greatest at sea level due to the weight of the overlying air.

How is the atmosphere organized by temperature (basic layers)?

Troposphere, Stratosphere, Mesosphere, Thermosphere, and Exosphere.

What is the troposphere and its key features?

Extends from the surface up to about 12 km; where all weather forms; tropopause marks its top; ~80% of the atmosphere’s mass is here.

What is the environmental lapse rate (ELR)?

The rate of cooling with increasing altitude; average ELR is 6.5°C per 1000 m; can produce temperature inversions.